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Review

Targeting the Heterogeneous Tumour-Associated Macrophages in Hepatocellular Carcinoma

by
Aloña Agirre-Lizaso
1,†,
Maider Huici-Izagirre
1,†,
Josu Urretabizkaia-Garmendia
1,
Pedro M. Rodrigues
1,2,3,
Jesus M. Banales
1,2,3,4 and
Maria J. Perugorria
1,2,5,*
1
Department of Liver and Gastrointestinal Diseases, Biodonostia Research Institute, Donostia University Hospital, University of the Basque Country (UPV-EHU), 20014 Donostia-San Sebastian, Spain
2
Centre for the Study of Liver and Gastrointestinal Diseases (CIBERehd), Instituto de Salud Carlos III (ISCIII), 28029 Madrid, Spain
3
IKERBASQUE, Basque Foundation for Science, 48009 Bilbao, Spain
4
Department of Biochemistry and Genetics, School of Sciences, University of Navarra, 31008 Pamplona, Spain
5
Department of Medicine, Faculty of Medicine and Nursing, University of the Basque Country (UPV/EHU), 20014 Donostia-San Sebastian, Spain
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Cancers 2023, 15(20), 4977; https://doi.org/10.3390/cancers15204977
Submission received: 1 September 2023 / Revised: 30 September 2023 / Accepted: 9 October 2023 / Published: 13 October 2023
(This article belongs to the Special Issue Immunotherapy for Hepatocellular Carcinoma: Novel Experimental Approaches and Biomarkers)
Versions Notes

Abstract

:

Simple Summary

Hepatocellular carcinoma (HCC) is a highly lethal disease with an increasing incidence. Despite the advancements in diagnosis and recent therapeutic options, improving the prognosis of HCC patients remains challenging. One of the reasons of the unsatisfactory outcome of patients with HCC is the complex tumour microenvironment (TME), which is composed of immune and stromal cells, limiting effective treatments. Recent research has highlighted the importance of macrophages in the development and progression of HCC, opening new possibilities for therapy. This review focuses on the heterogeneity of tumour-associated macrophages (TAMs) in HCC, the mechanisms through which HCC tumour cells polarize macrophages, and the therapeutic targets that are currently being tested to explore novel therapies that can improve the prognosis and quality of life of HCC patients.

Abstract

Hepatocellular carcinoma (HCC) is a prevalent and aggressive cancer that comprises a complex tumour microenvironment (TME). Tumour-associated macrophages (TAMs) are one of the most abundant immune cells present in the TME, and play a key role both in the development and in the progression of HCC. Thus, TAM-based immunotherapy has been presented as a promising strategy to complement the currently available therapies for HCC treatment. Among the novel approaches focusing on TAMs, reprogramming their functional state has emerged as a promising option for targeting TAMs as an immunotherapy in combination with the currently available treatment options. Nevertheless, a further understanding of the immunobiology of TAMs is still required. This review synthesizes current insights into the heterogeneous nature of TAMs in HCC and describes the mechanisms behind their pro-tumoural polarization focusing the attention on their interaction with HCC cells. Furthermore, this review underscores the potential involvement of TAMs’ reprogramming in HCC therapy and highlights the urgency of advancing our understanding of these cells within the dynamic landscape of HCC.

1. Introduction

Hepatocellular carcinoma (HCC) is the most common form of liver cancer and accounts for ~80% of cases [1]. Currently, HCC is considered a global health concern as its global incidence is increasing, being the third leading cause of cancer death worldwide, with approximately 18% of patients experiencing a relative 5-year survival rate [1,2]. The majority of HCC cases commonly arise in individuals with underlying chronic liver diseases resulting from hepatitis B virus (HBV) or hepatitis C virus (HCV) infection, alcohol abuse and metabolic liver disease, particularly nonalcoholic fatty liver disease (NAFLD) [3].
A significant proportion of HCC cases are still diagnosed at advanced stages, compromising the therapeutic options. In this regard, the advancements in the understanding of the molecular biology of the HCC has allowed us to develop molecular targeted agents (MTAs), including immune-checkpoint inhibitors (ICIs) [4,5], tyrosine kinase inhibitors (TKIs) and monoclonal antibodies (mAb) as a useful strategy for the treatment of advanced HCC. Sorafenib was the first treatment approved for HCC [6] and this paved the way for the development of new drugs including multi-targeted TKIs [7,8,9], as well as the vascular endothelial growth factor (VEGF) inhibitor [10]. Importantly, during the last few years, immunotherapy has made considerable progress in HCC treatment and the combination of ICIs and the VEGF inhibitor (atezolizumab plus bevacizumab) is currently the first-line treatment for patients with advanced HCC [11,12]. However, only some patients respond to this treatment and although inflamed and noninflamed HCC tumours and genomic signatures have been described and associated with response to ICIs [13], it is still important to develop a better understanding of the immune landscape of HCC.
The tumour microenvironment (TME) includes innate and adaptive immune cells, stromal cells, endothelial cells, cancer-associated fibroblasts and the extracellular matrix (ECM). Together, these components create a niche where tumour cells can grow and disseminate [14]. Tumour-associated macrophages (TAMs) are one of the most abundant stromal components in the TME of HCC tumours, and play a key role in promoting tumour progression by enhancing tumour growth, ECM remodeling, angiogenesis and metastasis, as well as in resistance to chemotherapeutic agents and checkpoint blockade immunotherapy [14,15]. Given the multifaceted functions of TAMs in the progression of HCC [15], selectively targeting the immunosuppressive TAMs within the TME holds promise in order to complement, and synergize with, currently available tools for HCC treatment. Novel approaches focusing on TAMs have been used in various strategies including their depletion, inhibition of their recruitment and reprogramming their functional state [16]. In this sense, macrophage reprogramming is devoid of the toxicities that involve strategies such as the ablation of all macrophages [16], and allows us to take advantage of their plasticity to change their phenotype and enhance their anti-tumour capacity. In this review, we discuss the heterogeneity of TAMs in HCC, the mechanisms by which tumour cells reprogram these cells and novel therapeutic options that are currently being tested at the preclinical and clinical levels.

2. Heterogeneity and Plasticity of TAMs in HCC

TAMs are considered a diverse and heterogeneous cell population originating from multiple sources and displaying various phenotypes and functions. Macrophages can be either embryonically seeded in the liver, where they continue to renew themselves, or derived from monocyte precursors that infiltrate tissues and undergo differentiation in response to specific microenvironmental conditions [17]. TAMs are primarily believed to arise from circulating monocytes, which respond to inflammatory signals emitted by tumour cells, leading to their differentiation into TAMs and contributing to tumour progression [18]. However, some studies also suggest that Kupffer cells (KCs) might also account for a small proportion of the total TAM pool of HCC [19,20]. In a study by Sharma et al., three populations of TAMs were identified and named as folate receptor beta (FOLR2) TAM1, osteopontin (SPP1) positive TAM2 and metallothionein 1G (MT1G)-enriched TAM3 [21]. While TAM2 and TAM3 clusters are believed to originate from monocytes, the TAM1 population can be further divided into two clusters. One of these clusters is predicted to be monocyte-derived, while the other cluster shows significant similarity to KCs [21,22]. Moreover, in another study, two macrophage clusters among seven clusters in HBV/HCV-related HCC tumours were considered Kupffer-like cells owing to their high expression of VSIG4, a membrane protein specific to tissue-resident macrophages [20].
Traditionally, macrophages have been categorized into two different activation states based on the expression of cell surface polarization markers as classically activated (M1) and alternatively activated (M2). TAMs are generally classified as pro-tumourigenic M2-like macrophages and their presence has been associated with a worse clinical outcome [20]. In this regard, a M2-like TAM-related signature associated with a poor prognosis in HCC patients has been described including prognosis-related genes such as PDLIM3, PAM, PDLIM7, FSCN1, DPYSL2, ARID5B, LGALS3, and KLF2 [23]. However, recent studies employing single-cell RNA-sequencing (sc-RNA-seq) technology have revealed the heterogeneity of TAMs in HCC. These studies have shown that certain TAM populations express both M1 and M2 markers, indicating a spectrum of intermediary phenotypes and highlighting their pleiotropic functions [20,24,25]. Thus, TAMs represent a highly heterogeneous cell population that can exert either pro-tumour or sometimes anti-tumour activities. Indeed, Song et al. identified a IL1B+ macrophage cluster in patients with HBV/HCV-related HCC that might be involved in anti-tumour responses, although further experiments need to be conducted to confirm this statement [20].
Multiple single-cell atlases of the HCC TME have been conducted using sc-RNA-seq technology and revealed the distinct transcriptional landscapes of each subpopulation within the TME [20,21,24,25,26,27,28,29,30]. These studies have also highlighted a significant level of heterogeneity among macrophages across different tumours, as certain populations were found to be specifically associated with individual patients, indicating inter-tumoural heterogeneity [27]. Importantly, it should be noted that each study has employed its own unique nomenclature for assigning names to the various subpopulations based on genes that were highly expressed in each specific subpopulation. However, it is important to note that there is considerable overlap among the different studies conducted, as shown in Table 1. This indicates that despite the unique nomenclature applied by each study, there are shared characteristics and subpopulations across multiple single-cell atlases of the HCC TME.
In a study by Lu et al. [27], five macrophage clusters enriched in tumour tissues were identified, which were consistent across patients. These clusters included anti-inflammatory TREM2+ macrophages newly recruited into tumours, which shared similarities with the FOLR2+ TAM1 cluster from Sharma’s HCC dataset [21] and Liu et al.’s FOLR2+ cluster [26]. Additionally, Lu et al. also described monocyte-derived FCN1+ LYZ+ VCAN+ macrophages, VEGFA+ macrophages associated with oxidative stress, and MMP9+ SSP1+ macrophages, which were considered terminally differentiated TAMs. The latter TAMs were believed to originate from monocyte-derived FCN1+ LYZ+ VCAN+ or TREM2+ macrophages and promote HCC cell migration, invasion, and tumour angiogenesis. These MMP9+ SSP1+ macrophages shared some similarities with SPP1+ TAM2s expressing TREM2 in Sharma’s HCC dataset [21,27]. Furthermore, Gao et al. [28] observed that compared to adjacent non-tumoural liver tissue, the APOC1+ SSP1+ TAM and HSPA1B+ TAM subpopulations were increased in tumour tissue. However, it remains uncertain and requires further confirmation whether these APOC1+ SPP1+ TAMs identified by Gao et al. represent the same population previously defined by Sharma et al. and Lu et al. [21,27]. Interestingly, recently, Liu et al. combined spatial transcriptomics with sc-RNA-seq and found that SPP1+ macrophages interact with cancer-associated fibroblasts (CAFs) to form a spatial structure named the tumour immune barrier (TIB) that limits the infiltration of immune cells into the tumour core [26].
Table 1. Marker genes for macrophage clusters from single-cell atlases of the HCC TME.
Table 1. Marker genes for macrophage clusters from single-cell atlases of the HCC TME.
Zhang et al. [25]
Mφ-THBS1+Mφ-C1QA+Mφ-APOE+Mφ-GPX3+Mφ-VCAN+Mφ-MARCO+
CST3, LYZ, CD68, THBS1, S100A8, S100A9CST3, LYZ, CD68, CD163, CD169, C1QA, SLC40A1, GPNMBCST3, LYZ, CD68, CD163, CD169, APOECST3, LYZ, CD68, FCGR3A, SAT1, LST1, HLA-DQB1CST3, LYZ, CD68, S100A4, HLA-DRA, HLA-DQA1CST3, LYZ, CD68, MARCO, S100A9, CD163
Sharma et al. [21]
TAM 1TAM 2TAM 3
C1QC, C1QA, SEPP1, LGMN, APOC1, CTSD, CD68, MS4A4A, PLD3, FOLR2, GPNMB, CD63, CTSB, FCGR3A, PSAP, FTL, CD14, LIPA, TYROBP, NPC2, DAB2, FCGRT, RNASE1, CTSC, FCER1G, C1QB, SLC40A1, APOE, CCL3, CCL3L3, MS4A7, CCL4L2, CD5L, VCAM1, CST3, SDC3, ITM2B, CCL4, CXCL2, IGF1, CD163, HES1, FOS, IER3RNASE1, CTSD, CSTB, NUPR1, FTL, APOC1, GPNMB, CTSB, APOE, CTSZ, LGALS1, PLTP, FABP5, TREM2, CXCL3, COLEC12, HSPA1A, PLIN2, SCD, CTSL, HSPA1B, MMP19, PLD3, ABL2, CEBPBMT1H, MT1X, MT1M, MT1E, MT1F, APOC3, ORM1, FTL, APOA2, APOC1, MT1A, ALB, ORM2, MT2A, AMBP, APOA1, AHSG, SAA1, RBP4, SIRPG, KNG1, LINC00520, OTOA, UCHL1, APOB
Song et al. [20]
Mφ-IL1B+Mφ-VSIG4+Mφ-FABP5+Mφ-S100A6+Mφ-S100A12+
TNFAIP3, IL1B, HSPA1B, AREG, CXCL10, WARS, CCL3L1, DNAJB1, GBP1, APOB, C3A, EREG, GBP5, G0S2, CXCL9GLDN, VSIG4, ADAMTS2, RPS26, TREM2, ALB, APOC3, RNASE1, SAA1, VWF, APOA1, GPR34, MS4A4A, STAB1, MSR1, SLCO2B1, A2M, HP, SELENOP, ABCC5, FOLR3, AL355075.4, FCER2, CLEC5A, OLR1, ALOX5AP, FN1, MT1GFABP4, PDK4, DHRS9, CXCL12, LIPA, ATP1B1, CLEC10A, MGLL, NRP1, ITGB5, MMP9, IGF1, TIMP3, SCN1B, HRH1, WWP1, FABP5, LPL, VCAM1, LILRB5, MATK, EGFL7, PHLDA1, CCL2, TM4SF19AL391807.1, S100A8, S100A9, VCAN, SULT1A1, RETN, CCR2, CDA, NRG1, CYP1B1, SELL, IL17RA, S1PR3, POU2F2, RFLNB, IGHA1, F5, AC007952.4, MGST1, CX3CR1MNDA, S100A8, S100A12, NFE2, CDA, CRISPLD2, TMEM154, SHROOM1, S1PR3, PRAM1, SLC46A2, NLRP12, LFNG, CX3CR1, NHSL2, S100Z
Mφ-CCL18+Mφ-AQP9+
CCL18, NUPR1, SCD, GATM, PLTP, GPNMB, APOC1, LGMN, RGS1, ARL4C, ATP6V0D2, APOE, SELENOP, A2M, PMP22, CTSB, CREM, SLC40A1, IGF1, CTSL, PLXDC1, ABCA1, DAB2, SPP1, C2, SLCO2B1, MSR1, CD163L1, SDC3, ABCG1, SLC2A1, CD59, FOLR2, RARRES1, AVPI1, RNASE1, FABP3, SLC7A8, ELL2, TNFRSF21, PLD3, HLA-DQA1, FUCA1, ACP5, CTSD, CD28, SMPDL3A, ENPP2, NRP1, IL2RA, ANKRD37, TSC22D1, OTOA, NPL, KCNMA1, SLC2A5, FABP5, ZNF331, AKR1B1, PLA2G7, ME1, VAT1, CSTB, SDS, SLC19A2, COLEC12, GAL3ST4, TFRC, ADM, ANKH, NRP2, FRMD4A, GPR137B, SGPL1, PKD2L1, HS3ST2, TCEAL9, MMP19, SDC2, BEX3, HSD17B14, CD209, ARRDC3, IL18BP, FARP1, EPHX1, VCAM1, SLC16A10, BNIP3, HLA-DRB5, FAM213A, GPX3, MAFF, CXCL3, RAB42, TMIGD3, CHCHD6, IGSF21, MMP14, CXCL2, INSIG1, EGLN3, ZNF395, ADAMDEC1, ADAM8, CHMP1B, CD5L, PLAU, HILPDA, HK2, GADD45A, SERPINF1, CXCL8, IL4I1, CCL4L2 AQP9, VCAN, SLC11A1, IFI44L, S100A12, NAMPT, FPR1, S100A8, CD55, IFI6, LILRA5, S100A9, IFITM2, VNN2, AC245128.3, SOCS3, CD300E, VSTM1, SLC25A37, MX2, ACSL1, IFITM3, LY6E, HMGB2, PLSCR1, PHC2, NLRP3, CLEC4E, ISG15, SLC2A3, SERPINB1, MX1, SELL, IFI44, ICAM3, FPR2, TREM1, THBS1, NFIL3, CLU, TIMP1, EREG, IRF7, UPP1, RIPOR2, GCA, RETN, MEGF9, CLEC4D, XAF1, MCTP2, OSCAR, LRRK2, MXD1, NFE2, RNASE2, CDA, AGFG1, OAS2, LINC02207, PGD, CRISPLD2, IL1R2, FES, CDKN2D, AL034397.3, CPD, AREG, GK, PROK2, FYN, LINC00937, MPHOSPH6, ECE1, CCDC69, RSAD2, RAB27A, CKAP4, OASL, MBOAT7, TMEM71, CR1, PADI4, MCEMP1, F5, CRIP1, CREB5, IL1RAP, MFGE8, GK5, CYP1B1, HBEGF, THBD, LTB4R, HERC5, ANXA6, FCAR, ADM, PLBD1, PDE4D, SPATA13, CEACAM4, MAN2A2, OAS3, VNN1, BCL3, TSPAN2, PTGER2, OSM, SPRY1, TOR1B, TOB1, TRMT6
Sun et al. [24]
Mφ-c1Mφ-c2Mφ-c3Mφ-c4Mφ-c5
CD163, CD68, SLC40A1, SELENOP, FOLR2, APOA2, IGLL5SLC16A10, CTNNB1, WTAP, SERINC5, PHACTR1SPP1, CSTB, RNASE1, MMP12, HK2BAG3, HSPB1, ZFAND2A, HSPH1, HSPA6, DNAJA4APOA2, BAG3, HSPB1, ZFAND2A, HSPH1, HSPA6, DNAJA4
Lu et al. [27]
Mφ-MARCO+Mφ-TREM2+MoMFs-c1MoMFs-c2Mφ-VEGFA+Mφ-MMP9+
MARCO, CD5L, C1QB, C1QA, SLC40A1, LIPA, MS4A7, MS4A6A, CFD, CD163C1QC, C1QB, C1QA, RNASE1, LGMN, HLA-DRA, MS4A4A, HLA-DPA1, SLC40A1, CD74S100A8, S100A9, IL1B, CXCL8, CXCL3, G0S2, EREG, PLAUR, CCL20, CXCL2FCN1, S100A8, S100A9, G0S2, LST1, BCL2A1, AIF1, LYZ, BAG3, C15orf48RNASE1, CCL3L3, CCL4L2, C1QA, LGMN, CCL3L3, CEBPB, CD83, BAG3, CCL18SSP1, MMP12, MMP9, FABP5, CSTB, GPNMB, LGALS1, RNASE1, C15orf48, CXCL8
Liu et al. [26]
Mφ-SPP1+
CSTB, SPP1, FTL, FABP5, CTSD, RNASE1, GPNMB, LGALS1, TM4SF19, NUPR1, CTSL, LGALS3, CCL7, VIM, SLAMF9, FABP4, BNIP3, MIF, ATP6V1F, CD68
In addition, Zhang et al. found two distinct macrophage clusters enriched in tumour tissues. These clusters were THBS1+ macrophages, which exhibited a signature similar to myeloid-derived suppressor cells (MDSCs) and were thus referred to as MDSC-like macrophages, and C1QA+ macrophages, which simultaneously presented signatures for TAMs, M1, and M2 macrophages [25]. Interestingly, MDSC-like macrophages highly expressed the S100A family genes FCN1 and VCAN, suggesting these could be the monocyte-derived macrophages also described by Lu et al. and Song et al. [20,27], and the C1QA+ macrophages highly expressed other genes such as APOE and TREM2. Additionally, Song et al. found a macrophage population that was absent in previous sc-RNA-seq studies and was mostly infiltrated in advanced HCC patients, and characterized by a higher expression of CCL18 [20]. These macrophages showed strong activity in lipid transport and metabolism, and immunosuppressive-related pathways.
Besides the heterogeneity observed at the individual cell level, it has been demonstrated that immune cell infiltrates exhibit notable differences between intrahepatic metastatic lesions in multifocal HCC and those in cases of multicentric occurrence. Indeed, in metastases, a higher presence of M2 macrophages and a lower abundance of T cells have been observed [31]. However, further studies need to be performed to characterize the distinct transcriptional landscapes.

3. The Dynamic Crosstalk between HCC Tumour Cells and TAMs

The TME, and especially TAMs, orchestrate complex and dynamic interactions with HCC tumour cells by cell-to-cell contact and/or soluble messengers [32]. In this regard, HCC tumour cells recruit monocytes to the HCC TME by secreting various factors and promote the transition into TAMs with a predominant M2-like phenotype [33]. Likewise, TAMs interact with the neighbouring cells in order to maintain an immunosuppressive microenvironment that ultimately results in tumour development and progression [34].

3.1. The Effect of HCC Tumour Cells Inducing M2 Polarization of TAMs in the TME

HCC tumour cells interact with TAMs through the secretion of diverse signalling molecules and exosomes that contain proteins, metabolites and nucleic acids (Table 2).

3.1.1. Signalling-Molecule Mediated Crosstalk

Cytokines represent a group of signalling proteins that play key roles in the immunomodulation of cancer [35]. In HCC, the interleukin-8 (IL-8) secreted by tumour cells induces the M2 polarization of TAMs, which further contributes to the epithelial to mesenchymal transition (EMT) of HCC cells [36]. On the other hand, the secretion of the pleiotropic cytokine IL-6 by HCC cells promotes the recruitment of TAMs to the TME, with the expression levels of this cytokine being associated with a poor prognosis of the patients [37]. Moreover, IL-6 secreted by HCC cells was shown to induce the expression of the immune checkpoint molecules such as programmed cell death ligand 1 (PD-L1) in TAMs and thus modulate immunosuppression [38]. Importantly, understanding the mechanisms involved in the regulation of immunosuppressive molecules could help to improve the efficacy of ICIs. Other pro-inflamatory cytokines such as IL-1β were shown to upregulate PD-L1 and colony-stimulating factor 1 (CSF1) expression in HCC cells [39]. HCC-derived CSF1 shifts macrophage polarization toward an M2 phenotype [40]. Indeed, it has been shown that inhibiting CSF1 receptor halts HCC progression in mouse models by inducing TAM polarization towards an M1-like phenotype [41]. Other cytokines such as osteopontin (SPP1) have also been associated with an immunosuppressive phenotype of macrophages in HCC. SPP1 facilitates M2-like polarization of macrophages, and promotes the expression of PD-L1 in HCC cells through the activation of the CSF1/CSF1R pathway in macrophages [42]. Moreover, multiomics analysis demonstrated that the oncogene SPP1 was associated with a poor prognosis in HCC. In vitro assays further demonstrated that SPP1 mediates interactions between HCC cells and TAMs by acting as a ligand, promoting M2-like polarization [43]. In addition, the chemokine CCL5 secreted by HCC tumour cells enhances the M2/M1 ratio of macrophages, boosting HCC progression [44]. Drp1-mediated mitochondrial fission has been reported to induce the cytosolic mitochondrial DNA (mtDNA) stress in HCC cells, which enhances CCL2 secretion by the TLR9-mediated NF-kB signalling pathway and promotes TAM recruitment and polarization [45]. Apart from CCL2, other HCC-derived cytokines and growth factors such as the macrophage inhibitory factor (MIF) and hepatocyte growth factor (HGF) have been reported to promote macrophage recruitment and M2-like stimulation [46,47]. In line with this, miR-144/451a cluster silencing by epigenetic mechanisms was shown to contribute to HCC progression targeting MIF and HGF [48].
Regarding specific signalling pathways, it has been demonstrated that HCC tumour cell-derived WNT ligands interact with macrophages, inducing polarization into an immunosuppressive M2-like phenotype, which in turn leads to tumour growth, migration and metastasis [49]. Likewise, several studies have emphasized the relevance of WNT and other major developmental signalling pathways (e.g., NOTCH) on TAM differentiation and consequent HCC progression, opening the door for new treatments targeting the WNT pathway [19,50,51].
Other signalling molecules that are secreted by HCC tumour cells include the protein high mobility group box 1 (HMGB1), which promotes autophagy-regulated M2 polarization of TAMs via the production of ROS in these cells through the TLR2/NOX2 axis [52]. In vivo assays with HCC-bearing mice showed that by inhibiting HMGB1 and ROS, M2-like TAM accumulation and nodule formation decreased [52].
On the other hand, the secretion of reactive nitrogen species (RNS) such as nitric oxide (NO), which were shown to be regulated by the transcription factor forkhead box O-1 (FOXO1) in HCC cells, modulates TAM infiltration and polarization towards an antitumour phenotype by reducing IL-6 and CD206 expression in these macrophages [53].

3.1.2. Exosome-Mediated Crosstalk

In the context of HCC, tumour cell-derived exosomes are known to modulate macrophage polarization and promote immune escape and tumour progression [54,55]. Among the transported molecules, noncoding RNA molecules (e.g., microRNAs, circular RNAs and long noncoding RNAs) constitute a major group and act as oncogenes or tumour suppressors [56]. In line with this, HCC tumour cell-derived exosomal miR-21-5p promotes TAM differentiation into an M2 phenotype by directly targeting Ras homolog family member B (RhoB) [57]. Likewise, exosomal miR-23a-3p released from endoplasmatic reticulum-stressed HCC cells has been reported to induce PD-L1 expression in TAMs and consequently inhibit T cell function [58]. Regarding the abovementioned relevance of PD-L1/PD-1 in maintaining an immunosuppressive TME, another study described how GOLM1-mediated exosomal PD-L1 transport into TAMs aggravated CD8+ T cell suppression in HCC [59]. Additionally, exosomal miR-146a-5p has also demonstrated to drive the M2 polarization of TAMs and disrupt T cell functions [60]. Moreover, a study by Zongqiang et al. described that HCC cell-derived exosomal miR452-5p targets TIMP3 in TAMs, provoking M2 polarization and fostering HCC progression [61]. Besides miRNAs, circular RNAs play crucial roles in tumour immunity by acting as miRNA sponges, among others [62]. An example of that could be circTMEM181, which was found to be upregulated in anti-PD1 therapy-resistant HCC patients [63]. Mechanistically, exosomal circTMEM181 sponges miR-488-3p and enhances CD39 expression in macrophages, leading to CD8+ T cell dysfunction and anti-PD-1 resistance. Furthermore, a recent study shows that tumour-derived exosomal hsa_circ_0074854 participates in the differentiation of M2-like TAMs and its suppression inhibits HCC tumour growth [64].
Table 2. HCC tumour cell-derived molecules that participate in the crosstalk with TAMs.
Table 2. HCC tumour cell-derived molecules that participate in the crosstalk with TAMs.
MoleculeType of CrosstalkMechanism of Action and Effect on TAMsReferences
IL-8Signalling molecule-mediated
-
Induces polarization of TAMs into a M2 phenotype, further contributing to the EMT of HCC cells.
[36]
IL-6Signalling molecule-mediated
-
Promotes the recruitment of TAMs to the TME.
-
Induces expression of PD-L1 in HCC TAMs.
[37,38]
CSF1Signalling molecule-mediated
-
Induces M2-like polarization of macrophages and anti-PD-1 resistance.
[40,41]
SPP1Signalling molecule-mediated
-
Promotes M2-like polarization of macrophages.
[43]
CCL5Signalling molecule-mediated
-
Enhances the M2/M1 ratio of macrophages, boosting HCC progression.
[44]
CCL2Signalling molecule-mediated
-
Promotes TAM recruitment and polarization.
[45]
AcetoacetateSignalling molecule-mediated
-
Induces TAM recruitment and enhances M2 polarization of macrophages by regulating MIF activity.
[46,48]
HGFSignalling molecule-mediated
-
Induces migration and regulates the distribution of M2 macrophages in the tumour tissue.
[47,48]
WNT ligandsSignalling molecule-mediated
-
Induce polarization of macrophages into an immunosuppressive M2-like phenotype, which in turn leads to tumour growth, migration and metastasis.
[49]
HMGB1Signalling molecule-mediated
-
Promotes M2 polarization of TAMs via the HMGB1/TLR2/NOX2/autophagy axis.
[52]
NOSignalling molecule-mediated
-
Enhances TAM infiltration and polarization towards an anti-tumour phenotype.
-
Reduces IL-6 and CD206 expression in macrophages.
[53]
miR-21-5pExosome-mediated
-
Promotes TAM differentiation into a M2 phenotype via RhoB UTR targeting.
[57]
miR-23a-3pExosome-mediated
-
Induces PD-L1 expression in TAMs and consequently inhibits T cell function.
[58]
PD-L1Exosome-mediated
-
Aggravates CD8+ T cell suppression in HCC.
[59]
miR-146a-5pExosome-mediated
-
Drives M2 polarization of TAMs and disrupts T cell functions.
[60]
miR452-5pExosome-mediated
-
Targets TIMP3 in TAMs, provoking a M2 polarization and fostering HCC progression.
[61]
circTMEM181Exosome-mediated
-
Sponges miR-488-3p and enhances CD39 expression in macrophages, leading to CD8+ T cell dysfunction and anti-PD-1 resistance.
[63]
hsa_circ_0074854Exosome-mediated
-
Participates in the differentiation of M2-like TAMs and its suppression inhibits HCC tumour growth.
[64]
Abbreviations: CCL, C-C motif chemokine; CD, cluster of differentiation; CSF1, colony-stimulating factor 1; EMT, epithelial to mesenchymal transition; HCC, hepatocellular carcinoma; HGF, hepatocyte growth factor; HMGB1, high mobility group box 1; IL, interleukin; MIF, macrophage inhibitory factor; NO, nitric oxide; NOX2, NADPH oxidase 2; PD-1, programmed cell death protein 1; PD-L1, programmed cell death ligand 1; RhoB, Ras homolog family member B; SPP1, osteopontin; TAMs, tumour-associated macrophages; TIMP3, metalloproteinase inhibitor 3; TLR2, toll-like receptor 2; TME, tumour microenvironment; UTR, untranslated region; WNT, wingless-related integration site.

3.2. The Effect of M2-Like TAMs Promoting the Progression, Growth and Invasiveness of HCC

In recent years, many studies have aimed to elucidate the molecular mechanisms that hide behind the complex interactions of M2-like TAMs with tumour cells favouring HCC progression (Table 3).

3.2.1. Signalling Molecule-Mediated Crosstalk

In respect of signalling molecule-mediated crosstalk, it has been shown that in hypoxic and inflammatory conditions, M2-like TAMs secrete high amounts of IL-1β, inducing an overexpression of hypoxia inducible factor (HIF)-1α in HCC cells, the latter being responsible of an increased EMT of HCC cells and HCC metastasis in mouse models [65]. Moreover, numerous works have underlined the importance of TAMs-derived IL-6 in promoting HCC progression and metastasis [66,67,68].
Similarly, IL-8 has been shown to promote EMT of HCC tumour cells via the JAK2/STAT3/Snail signalling pathway, and hence induce their migration and invasion [69]. In addition, immunosuppressive TAMs have shown to promote EMT on HCC cells via WNT/β catenin pathway by releasing tumour necrosis factor α (TNF-α) [70]. M2 macrophage-derived chemokine ligand 17 (CCL17) is also known to promote EMT in HCC cells via the WNT/β catenin pathway, contributing to tumourigenesis [71].
Besides cytokines, the secretion of TGF-β by TAMs promotes EMT and confers stem-like properties to HCC tumour cells [72]. Likewise, S100 calcium-binding protein A9 (S100A9) secreted by TAMs boosts HCC progression by inducing stemness of tumour cells [73]. In addition, the pro-tumour lectin galectin-1 (Gal-1), when secreted by TAMs via TLR2-mediated secretory autophagy, has been shown to induce HCC progression [74]. Computational analyses of public datasets and in vitro and in vivo experiments have identified the oncoprotein-induced transcript 3 (OIT3) as a novel M2 marker. The overexpression of OIT3 in M2 macrophages was found to be associated with a higher expression of molecules that induce HCC progression, metastasis and immunosuppression such as matrix metallopeptidase 2 (MMP2), VEGFA and PD-L1 in TAMs [75,76].

3.2.2. Exosome-Mediated Crosstalk

Exosome-mediated crosstalk is also involved in the interplay between M2 TAMs and HCC tumour cells. Exosomal miR-17-92 clusters from M2-like TAMs were shown to induce a mismatch in the TGF-β1/BMP-7 pathway of HCC tumour cells by modulating post-transcriptional and post-translational modifications of various proteins. As a consequence, miR-17-92 increased HCC tumour cells’ stem-like properties and their invasive capacity [77]. Another M2 macrophage-derived exosomal miRNA with the capacity of stimulating the stemness of HCC cells is miR-27a-3p, which targets thioredoxin-interacting protein (TXNIP) [78]. Likewise, exosomal miR-92a-2-5p secreted by macrophages boosts the invasiveness of tumour cells by modulating the AR/PHLPP/p-AKT/β-catenin signalling pathway [79]. Moreover, miR-660-5p secreted from M2 macrophages modulates Kruppel-like factor 3 (KLF3) in HCC tumour cells, therefore inducing HCC progression [80]. TAMs can also secrete exosomes containing M2 macrophage polarization-associated lncRNAs, such as lncMMPA, which induces the proliferation of HCC tumour cells by regulating their metabolism [81]. On the other hand, exosome-mediated crosstalk also happens between M1 macrophages and tumour cells. For instance, exosomal miR-628-5p secreted by M1 macrophages inhibits HCC progression by targeting the circFUT8/miR-552-3p/CHMP4B pathway [82].
Table 3. TAM-derived molecules that participate in the crosstalk with HCC tumour cells.
Table 3. TAM-derived molecules that participate in the crosstalk with HCC tumour cells.
MoleculeType of CrosstalkMechanism of Action and Effect on HCC Tumour CellsReferences
IL-1βSignalling molecule-mediated
-
Stimulates an increase in EMT of HCC cells and metastasis via HIF-1α/IL-1β signalling pathway.
[65]
IL-6Signalling molecule-mediated
-
Induces HCC carcinogenesis via STAT3 signalling pathway.
-
Enhances inflammation response inducing HCC progression.
-
Stimulates HCC metastasis under hypoxic conditions.
[66,67,68]
IL-8Signalling molecule-mediated
-
Promotes EMT of HCC tumour cells via JAK2/STAT3/Snail signalling pathway and hence induces their migration and invasion.
[69]
TNF-αSignalling molecule-mediated
-
Promotes EMT on HCC cells via WNT/β catenin pathway.
[70]
CCL17Signalling molecule-mediated
-
Promotes EMT on HCC cells via WNT/β catenin pathway, contributing to tumourigenesis.
[71]
TGF-βSignalling molecule-mediated
-
Promotes EMT and confers stem-like properties to HCC tumour cells.
[72]
S100A9Signalling molecule-mediated
-
Boosts HCC progression by inducing stemness of tumour cells.
[73]
Gal-1Signalling molecule-mediated
-
It is secreted by TAMs via TLR2-mediated secretory autophagy and induces HCC progression.
[74]
miR-17-92 clusterExosome-mediated
-
Induces a mismatch in the TGF-β1/BMP-7 pathway of HCC tumour cells, leading to an increase in HCC tumour cells’ stem-like properties and invasive capacity.
[77]
miR-27a-3pExosome-mediated
-
Stimulates stemness of tumour cells by targeting TXNIP.
[78]
miR-92a-2-5pExosome-mediated
-
Boosts invasiveness of tumour cells by modulating AR/PHLPP/p-AKT/β-catenin signalling pathway.
[79]
miR-660-5pExosome-mediated
-
Modulates KLF3 in HCC tumour cells, therefore inducing HCC progression.
[80]
lncMMPAExosome-mediated
-
Induces proliferation of HCC tumour cells by regulating their metabolism.
[81]
miR-628-5pExosome-mediated
-
Inhibits HCC progression by targeting the circFUT8/miR-552-3p/CHMP4B pathway.
[82]
Abbreviations: AR, androgen receptor; BMP-7, bone morphogenetic protein 7; CCL17, C-C motif chemokine 17; CHMP4B, charged multivesicular body protein 4B; EMT, epithelial to mesenchymal transition; Gal-1, galectin-1; HCC, hepatocellular carcinoma; HIF-1α, hypoxia inducible factor 1α; IL, interleukin; JAK2, Janus kinase 2; KLF3, Kruppel-like factor3; PHLPP, PH domain leucine-rich repeat protein phosphatase; S100A9, S100 calcium-binding protein A9; STAT3, signal transducer and activator of transcription 3; TAMs, tumour-associated macrophages; TGF-β, transforming growth factor β; TLR2, toll-like receptor 2; TNF-α, tumour necrosis factor α; TXNIP, thioredoxin-interacting protein; WNT, wingless-related integration site.

4. Current Strategies Targeting TAMs in HCC

During the last few years, several preclinical and clinical studies have started to evaluate TAM-centered therapeutic strategies in HCC. In this regard, several approaches for targeting TAMs have been proposed for limiting liver cancer progression, including targeting TAM recruitment and accumulation in the tumour and the functional reprogramming of TAMs (Table 4).
Although the inhibition of monocyte/macrophage recruitment by chemokine targeting approaches such as blocking the CCL2/CCR2 axis with a CCR2 antagonist suppresses tumour growth [83] and potentiates the therapeutic effects of sorafenib in mouse models of HCC [84], using CCR2 antagonists as a monotherapy might not be as effective as initially thought, as compensatory TAM subsets such as KC-like TAMs can emerge [19]. These results highlight that combination therapies targeting different cell types or the reprogramming of TAMs might be a more viable therapeutic strategy for patients with HCC. Indeed, a clinical trial (NCT04123379) to assess the clinical efficacy of BMS-813160, a CCR2/CCR5 inhibitor, in combination with nivolumab (anti-PD1 mAb) is currently ongoing. In this phase IIa trial designed to assess the clinical efficacy of BMS-813160, patients will receive nivolumab monotherapy or neoadjuvant nivolumab in combination with BMS-813160 prior to surgical resection, with the primary endpoint being significant tumour necrosis (>70% tumour necrosis at time of surgery) and the secondary endpoints being the time to surgery, safety and tolerability, radiographic response, progression-free survival, and overall survival. Another well-stablished method of reducing TAM recruitment and their polarization includes blocking the CSF1/CSFR1 axis, which is a well-known monocyte/macrophage differentiation and survival factor [85,86]. HCC-derived CSF1, which is transcriptionally regulated by ZFP64, induces M2-like polarization of macrophages and anti-PD1 resistance [40]. Mechanistically, blocking the PKCα/ZFP64/CSF1 axis with multi-kinase inhibitors such as Lenvatinib, which is able to decrease PKC expression levels [87], improves anti-PD1 efficacy [40,88]. Other strategies targeting the CSF1/CSFR1 axis like CSF1R blockade by PLX3397, an inhibitor for CSF1R tyrosine kinase, have shown to inhibit tumour progression in mouse models of HCC by shifting the polarization of TAMs [41]. In line with these results, inhibition of the CSF1/CSFR1 pathway reduces macrophage recruitment and M2 phenotype polarization and sensitizes HCC tumours to anti-PD-L1 blockade [42]. These preclinical studies suggest that therapeutic strategies blocking CSF1 signalling via CSFR1 inhibition on TAMs might increase the efficacy of ICIs in patients with HCC. In fact, a phase 2 clinical trial (NCT04050462) with the anti-CSFR1 antibody cabiralizumab as an adjuvant therapy for immune checkpoint-based treatment with nivolumab is currently ongoing in patients with HCC, which aims to measure the objective response rate (ORR) of cabiralizumab in combination with nivolumab in comparison to nivolumab monotherapy.
Although strategies directed to target TAMs have initially been focused on macrophage depletion, there is growing evidence that reprogramming of TAMs to overcome an immunosuppressive environment may constitute a more effective therapeutic strategy in cancer [89]. One of the hotspots in reversing the TAM phenotype in cancer has been inhibiting the phosphoinositide 3-kinase gamma (PI3Kγ), which was identified as a potent regulator of macrophage polarization, stimulating C/EBPβ activation with the consequent activation of an immunosuppressive transcriptional program in various solid tumours [90]. Moreover, it was shown that PI3Kγ inhibition can synergize with T cell-targeted therapy (anti-PD-1) in mouse tumour models [90]. As some of the mechanisms of resistance to sorafenib, which has been the first-line treatment for HCC for many years, have been linked to the presence of M2-type macrophages in HCC [47,91,92], combination strategies such as sorafenib in combination with the PI3Kγ inhibitor (TG100-115) have been tested in the preclinical setting [93]. In line with this, a clinical trial for HCC patients with the combination of a Pan-PI3K inhibitor (SF1126) with the anti-PD1 mAb nivolumab was also designed (NCT03059147). Directly targeting transcription factors such as C/EBPα that regulate the function of myeloid cells and that are deregulated in solid tumours such as HCC [94] can represent another therapeutic option [95]. In this regard, therapeutic upregulation of C/EBPα with small activating RNA (saRNA; MTL-CEBPA) has been tested in the preclinical and clinical setting in combination with sorafenib (NCT02716012), resulting in an overall reduction in pro-tumour M2 TAMs and showing anti-tumour responses in patients with advanced HCC. The anti-tumour effects of MTL-CEBPA in different mouse cancer models were accentuated when this treatment was combined with ICIs [95], with this being the rationale behind designing a new clinical trial that investigates the potential benefit of MTL-CEBPA and pembrolizumab (anti-PD1) combination in patients with liver cancer (NCT04105335). Other protein kinases that are enriched in TAMs of HCC tumours based on single-cell RNA sequencing data include glycogen synthase kinase 3β (GSK3β) [96]. Of note, macrophage GSK3β deficiency halts the progression of HCC by inhibiting the M2 phenotype of TAMs and enhances the sensitivity of anti-PD1 immunotherapy. Inhibiting GSK3β with a GSK3β inhibitor in TAMs reduces the proliferation, migration and invasion of HCC cells in vitro and inhibits tumour growth in vivo improving the sensitivity of the anti-PD1 therapy.
Metabolic reprogramming of TAMs is also linked to the plasticity of these cells. In this respect, it has been shown that receptor-interacting protein kinase 3 (RIPK3) is downregulated in HCC-associated TAMs, its deficiency being associated with a reduction in reactive oxygen species (ROS) production and fatty acid oxidation (FAO) via PPAR pathway activation and an induction of M2 polarization of TAMs [97]. In line with this, FAO blockade in TAMs reverses their immunosuppressive phenotype in mouse HCC tissues and supresses HCC tumourigenesis.
Other strategies of promoting reprogramming of TAMs towards an M1 phenotype includes the use of TLR agonists, such as resiquimod (R848), a potent agonist of toll-like receptors TLR7 and TLR8, to enhance cancer immunotherapy [98]. In line with this, recently engineered microparticles (MPs) derived from alpha-fetoprotein (AFP)-overexpressing macrophages loaded with resiquimod (R848@M2pep-MPsAFP) were developed to target and reprogram M2-like TAMs into M1-like phenotypes to ameliorate tumour immunosuppressive microenvironments [99]. Additionally, R848@M2pep-MPsAFP induces stronger stem-like CD8+ T cell proliferation and differentiation to achieve a long-term immune surveillance to boost anti-PD-1 therapy in HCC [99]. In this respect, a clinical trial employing the RO7119929 agent, which is a TLR7 agonist, in combination with tocilizumab (anti-IL-6 receptor) has been performed (NCT04338685). However, combination therapy with a checkpoint inhibitor may be needed to leverage the proinflammatory potential of the RO7119929 agent to enhance the anti-tumour activity [100].
On the other hand, other strategies to enhance the anti-tumour responses of TAMs include restoring their phagocytic capacity by blocking the “don’t eat me” signal of CD47-SIRPα. CD47 expression in HCC cells is correlated with the poor overall survival of patients with HCC [101] and antibody-mediated targeting CD47 was shown to inhibit tumour growth in mouse models of HCC [102]. In addition, combination therapies of CD47 blockade with the anti-CD47 antibody and doxorrubicin have demonstrated an enhanced beneficial effect as compared to doxorrubicin in monotherapy [103]. Moreover, CD47 expression levels in HCC cells might serve as a prognostic marker of patients who might benefit from TACE treatment [101]. In this respect, anti-human SIRPα antibodies have been developed for the treatment of HCC and assessed in a clinical trial (NCT02868255), being the objective of this trial to harvest samples from patients with HCC (inflammatory ascites, HCC resections and blood samples) to evaluate SIRP-CD47 expression and the effect of the anti-hSIRP Ab on various cellular types.
Recent genetic engineering technologies, such as chimeric antigen receptor macrophages (CAR-M), have started to pave the way for using macrophages in adoptive cell therapies to treat solid tumours [104]. In vitro, CAR-Ms have demonstrated to have antigen-specific phagocytosis capacity and to promote tumour clearance. Of note, an infusion of CAR-Ms have been shown to prevent tumour progression in various solid tumour mouse models [104]. A phase I human study of adenovirally transduced autologous macrophages engineered to contain an anti-HER2 CAR in patients with HER2 overexpressing solid tumours in monotherapy and in combination with pembrolizumab is currently ongoing (NCT04660929).
Regarding their potential applicability in HCC, a liver macrophage-targeting mRNA-laden lipid nanoparticle (LNP) was recently generated to produce CAR-Ms coexpressing glypican-3 (GPC3)-specific CAR, a glycoprotein attached and extensively upregulated in HCC tissues, and Siglec-G lacking immunoreceptor tyrosine-based inhibition motifs (Siglec- GΔITIMs). Siglec-G is expressed on the surface of macrophages and interacts with the anti-phagocytic signal protein CD24 upregulated in the tumour tissues of HCC patients. This interaction activates the ITIM motif in macrophages, which is known to restrict the phagocytic function of macrophages. Thus, this novel approach may help macrophages to identify and competitively bind to CD24 of HCC cells, augmenting the cellular phagocytosis by evading the activation of ITIMs, subsequently favouring the antigen cross-presentation of CAR-Ms [105]. In fact, mice treated with LNPs generating CAR-Ms as well as CD24-Siglec-G blockade are able to augment the phagocytic function of liver macrophages, reduce tumour burden and increase the survival of mice subjected to an orthotopic HCC model.
Table 4. Preclinical studies and clinical trials targeting TAMs in HCC.
Table 4. Preclinical studies and clinical trials targeting TAMs in HCC.
Molecular TargetAgentCombination TherapyResultsClinical Trial NumberReferences
CCL2/CCR2 axisCCR2 antagonist (RDC018)N/AInhibits tumour growth and metastasis and prolongs the survival of mice. [83]
CCR2 antagonist (747)Sorafenib (low-dose)Enhances the therapeutic efficacy of low-dose sorafenib, elevating the numbers of intra-tumoural CD8+ T cells and increasing death of tumour cells. [84]
CCL2/CCR2 and CCL5/CCR5 axisCCR2/CCR5 inhibitor
(BMS-813160)		Anti-PD1 mAb (Nivolumab)Clinical trial Phase II (ongoing)NCT04123379
CSF1/CSFR1 axisGö6976, a protein kinase inhibitor, lenvatinib, or using a CSF-1R inhibitor (BLZ945)Anti-PD1 therapyGö6976 or BLZ945 combined with anti-PD1 inhibit tumour growth. Lenvatinib and anti-PD1 exert synergistic anti-tumour effects and prolongs the survival of mice [40,88]
CSF1R inhibitor (PLX3397)N/ACSF1R blockade delays tumour growth by shifting the polarization of TAMs toward an M1-like phenotype. [41]
CSF1R inhibitor (PLX3397)Anti-PD-L1Blocking CSF1/CSF1R prevents TAM trafficking and enhances the efficacy of anti-PD-L1. [42]
Anti-CSF1R mAb (Cabiralizumab)Anti-PD1 mAb (Nivolumab)Clinical trial Phase II (ongoing)NCT04050462
PI3KγTG100-115SorafenibHigher anti-tumour efficiency than the free drug solutions. [93]
Pan-PI3K inhibitor (SF1126)Anti-PD1 mAb (Nivolumab)Clinical trial Phase INCT03059147
C/EBPαsaRNA; MTL-CEBPASorafenibA marked reduction in tumour growth following MTL-CEBPA treatment is observed in preclinical mouse HCC models. [95]
saRNA; MTL-CEBPASorafenibClinical trial Phase Ib.
MTL-CEBPA causes radiologic regression of tumours in 26.7% of patients with HCC with an underlying viral etiology.		NCT02716012[95]
saRNA; MTL-CEBPAAnti-PD1 mAb (Pembrolizumab)Clinical trial Phase Ia/Ib (ongoing)NCT04105335
GSK3βGSK3β inhibitorAnti-PD1 mAbMacrophage GSK3β-deficiency inhibits the progression of HCC and enhances the sensitivity of anti-PD1 immunotherapy. [96]
RIPK3RIPK3 inhibitor (GSK872)N/AEnhances M2 markers (CD206 and Arg1) and PPARs (Ppara and Pparg) in macrophages. [97]
TLR7 and TLR8 agonistsR848@M2pep-MPsAFPAnti-PD-1 mAb R848@M2pep-MPsAFP efficiently reprograms M2-like macrophages and activates CD8+ T cells decreasing the tumour growth and prolonging the survival of mice improving the anti-tumour immune response of anti-PD-1 antibody. [99]
TLR7 agonist (RO7119929)N/AClinical trial Phase I. Combination therapy with ICIs may be needed to enhance its anti-tumour activity.NCT04338685[100]
CD47-SIRPαAnti-CD47 mAbN/ACD47 blockade inhibits tumour growth in mouse heterotopic and orthotopic models of HCC. [102]
Anti-CD47 mAbDoxorubicinAnti-CD47 Ab in combination with doxorubicin exerts maximal effects on tumour suppression in a patient-derived HCC xenograft mouse model, as compared to monotherapies alone. [103]
Anti-hSIRPα AbN/AClinical trial.
Collection of human samples		NCT02868255
CAR
macrophages		LNP-mediated dual mRNA co-delivery of Siglec-GΔITIMs-expressing GPC3-specific CAR macrophagesN/ALNP-engineered Siglec-GΔITIMs-expressing GPC3-specific CAR-Ms present augmented HCC-specific engulfment of macrophages, subsequently stimulating an adaptive anti-tumour immune response and preventing tumour growth in an orthotopic HCC mouse model. [105]
Anti-HER2 CAR-M (CT-0508) in patients with HER2 overexpressing solid tumours Anti-PD1 mAb (Pembrolizumab)Clinical trial Phase I (ongoing)NCT04660929
Abbreviations: Arg1, arginase 1; CAR, chimeric antigen receptor; CCL, C-C motif chemokine ligand; CCR, C-C motif chemokine receptor; CD, cluster of differentiation; C/EBPα, CCAAT/enhancer-binding protein alpha; CSF1, colony-stimulating factor 1; CSF1R, colony-stimulating factor 1 receptor; GPC3, glypican 3; GSK3β, glycogen synthase kinase 3β; HCC, hepatocellular carcinoma; ICI, immune checkpoint inhibitor; LNP, lipid nanoparticle; mAb, monoclonal antibody; PD-1, programmed cell death protein 1; PD-L1, programmed cell death ligand 1; PI3Kγ, phospatidylinositide 3-kinase γ; RIPK3, receptor interacting serine/threonine kinase 3; SIRPα, signal-regulatory protein α; TAMs, tumour-associated macrophages; TLR, toll-like receptor.

5. Future Perspectives and Conclusions

In cancer, the existence of a distinct microenvironment of each tumour contributes to the heterogeneity of macrophages [106]. Although many studies in HCC have defined distinct macrophage populations, this has been achieved by applying their own unique nomenclature, despite there being considerable overlap across the different studies [20,21,24,25,26,27,28,29,30]. In line with this, TAMs might derive primarily from circulating blood monocytes, even though evidence also suggests that KCs might also account for a small part of the total TAM pool of HCC [19]. Lineage tracing of TAMs in HCC can lead to a more thorough understanding of the complex nature of the TME. In future experiments, given the heterogeneity of TAMs, it will be important to describe their origin, surface markers, role and spatial distributions to identify the specific types being studied in each experiment. Moreover, as specific macrophage subsets assume distinct roles in HCC and anti-tumour immunity, avoiding simply classifying macrophages into M1 and M2 groups is important, and studies in the future should focus on carefully characterizing the great diversity of macrophage subpopulations.
TAMs can dynamically interact and crosstalk with HCC tumour cells modulating the development, growth and invasiveness of HCC cells by a great variety of mechanisms. In this regard, HCC tumour cells are known to secrete signalling molecules such as cytokines, chemokines and growth factors that are able to promote the transition of macrophages into TAMs acquiring a predominant M2-like phenotype. Most of the studies characterizing the secretome of HCC cells and the influence of the secreted factors on macrophages are based on in vitro models that do not recapitulate the great complexity and diversity of macrophages that are present in the TME of HCC tumours.
Recently, TAMs have emerged as a relevant cell type for targeted therapy in liver cancer and several preclinical and clinical therapeutic approaches have been developed aiming to deplete or reduce this population in HCC tumours. Nevertheless, pan-macrophage therapeutic strategies targeting all macrophages are often associated with a compensatory emergence of other immunosuppressive cell types and the presence of systemic toxicity, with limited therapeutic benefits. In this respect, reprogramming M2-like TAMs to acquire an immunostimulatory phenotype may represent a more effective strategy, in particular when this approach is combined with other treatments such as immune checkpoint inhibitors. Despite the fact that preclinical studies have demonstrated encouraging results, the use of animal models have some limitations, as they do not recapitulate the complex heterogeneity and full spectrum of TAM subtypes that are present in humans. At present, there are only a small number of clinical trials targeting TAMs. Nonetheless, their efficacy needs to be further assessed.
Adoptive cell therapies using genetic engineered technologies such as CAR-M have also started to enter the field of cancer, also holding promise for the treatment of HCC. Accordingly, macrophages equipped with tumour antigen-specific CARs present increased anti-tumour activity. However, major challenges remain to be solved before their potential clinical application, including the selection of liver tumour cell-specific targets and their biosafety profiles. On the one hand, macrophages present a relatively weak proliferative capacity, which might affect the prolonged therapeutic benefit. Moreover, the high heterogeneity of HCC tumours might compromise the efficiency of CAR-Ms, as some HCC cells that do not express the target antigens may exist. In addition, although promising results might be obtained from experimental in vivo studies, further clinical trials in patients with a much more complex HCC heterogeneity are required to evaluate the efficiency of CAR-Ms.
In the future, tailoring TAM-targeted therapies in combination with other therapeutic strategies may constitute a promising alternative treatment for patients with HCC.

Author Contributions

A.A.-L., M.H.-I., J.U.-G. and M.J.P.: wrote the first draft and designed tables; P.M.R. and J.M.B.: reviewed and edited the manuscript; M.J.P.: designed, wrote, assembled, and critically reviewed the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

M Huici-Izagirre was funded by a grant from the Scientific Foundation of the Spanish Association Against Cancer (PRDGU233927HUIC). P.M. Rodrigues, J.M. Banales and M.J. Perugorria were funded by the Spanish Carlos III Health Institute (ISCIII) (J.M. Banales (FIS PI18/01075, PI21/00922 and Miguel Servet Program CPII19/00008); M.J. Perugorria (PI20/00186); P.M. Rodrigues (Miguel Servet Program)) cofinanced by “Fondo Europeo de Desarrollo Regional” (FEDER).

Conflicts of Interest

The authors declare no conflict of interest.

Abbreviations

CAF: cancer-associated fibroblast; CAR-M, chimeric antigen receptor macrophage; CSF1, colony-stimulating factor 1; ECM, extracellular matrix; EMT, epithelial to mesenchymal transition; FDA, food and drug administration; HBV, Hepatitis B virus; HCC, Hepatocellular carcinoma; HCV, Hepatitis C virus; ICI; immune checkpoint inhibitor; IL, interleukin; KC, Kupffer cell; NAFLD, nonalcoholic fatty liver disease; mAb, monoclonal antibody; MDSC, myeloid-derived suppressor cells; MTA, molecular targeted agent; PD-L1, programmed cell death ligand 1; sc-RNA-seq, single-cell RNA-sequencing; SPP1, osteopontin; TAM, tumour-associated macrophage; TKI, tyrosine kinase inhibitor; TME, tumour microenvironment; VEGF, vascular endothelial growth factor.

References

  1. Sung, H.; Ferlay, J.; Siegel, R.L.; Laversanne, M.; Soerjomataram, I.; Jemal, A.; Bray, F. Global Cancer Statistics 2020: GLOBOCAN Estimates of Incidence and Mortality Worldwide for 36 Cancers in 185 Countries. CA Cancer J. Clin. 2021, 71, 209–249. [Google Scholar] [CrossRef] [PubMed]
  2. Siegel, R.L.; Miller, K.D.; Fuchs, H.E.; Jemal, A. Cancer Statistics, 2022. CA Cancer J. Clin. 2022, 72, 7–33. [Google Scholar] [CrossRef]
  3. Yang, J.D.; Hainaut, P.; Gores, G.J.; Amadou, A.; Plymoth, A.; Roberts, L.R. A Global View of Hepatocellular Carcinoma: Trends, Risk, Prevention and Management. Nat. Rev. Gastroenterol. Hepatol. 2019, 16, 589–604. [Google Scholar] [CrossRef]
  4. El-Khoueiry, A.B.; Sangro, B.; Yau, T.; Crocenzi, T.S.; Kudo, M.; Hsu, C.; Kim, T.-Y.; Choo, S.-P.; Trojan, J.; Welling, T.H.; et al. Nivolumab in Patients with Advanced Hepatocellular Carcinoma (CheckMate 040): An Open-Label, Non-Comparative, Phase 1/2 Dose Escalation and Expansion Trial. Lancet 2017, 389, 2492–2502. [Google Scholar] [CrossRef]
  5. Finn, R.S.; Ryoo, B.-Y.; Merle, P.; Kudo, M.; Bouattour, M.; Lim, H.Y.; Breder, V.; Edeline, J.; Chao, Y.; Ogasawara, S.; et al. Pembrolizumab as Second-Line Therapy in Patients with Advanced Hepatocellular Carcinoma in KEYNOTE-240: A Randomized, Double-Blind, Phase III Trial. J. Clin. Oncol. 2020, 38, 193–202. [Google Scholar] [CrossRef] [PubMed]
  6. Llovet, J.M.; Ricci, S.; Mazzaferro, V.; Hilgard, P.; Gane, E.; Blanc, J.-F.; de Oliveira, A.C.; Santoro, A.; Raoul, J.-L.; Forner, A.; et al. Sorafenib in Advanced Hepatocellular Carcinoma. N. Engl. J. Med. 2008, 359, 378–390. [Google Scholar] [CrossRef] [PubMed]
  7. Kudo, M.; Finn, R.S.; Qin, S.; Han, K.-H.; Ikeda, K.; Piscaglia, F.; Baron, A.; Park, J.-W.; Han, G.; Jassem, J.; et al. Lenvatinib versus Sorafenib in First-Line Treatment of Patients with Unresectable Hepatocellular Carcinoma: A Randomised Phase 3 Non-Inferiority Trial. Lancet 2018, 391, 1163–1173. [Google Scholar] [CrossRef]
  8. Bruix, J.; Qin, S.; Merle, P.; Granito, A.; Huang, Y.-H.; Bodoky, G.; Pracht, M.; Yokosuka, O.; Rosmorduc, O.; Breder, V.; et al. Regorafenib for Patients with Hepatocellular Carcinoma Who Progressed on Sorafenib Treatment (RESORCE): A Randomised, Double-Blind, Placebo-Controlled, Phase 3 Trial. Lancet 2017, 389, 56–66. [Google Scholar] [CrossRef] [PubMed]
  9. Abou-Alfa, G.K.; Meyer, T.; Cheng, A.-L.; El-Khoueiry, A.B.; Rimassa, L.; Ryoo, B.-Y.; Cicin, I.; Merle, P.; Chen, Y.; Park, J.-W.; et al. Cabozantinib in Patients with Advanced and Progressing Hepatocellular Carcinoma. N. Engl. J. Med. 2018, 379, 54–63. [Google Scholar] [CrossRef] [PubMed]
  10. Zhu, A.X.; Kang, Y.-K.; Yen, C.-J.; Finn, R.S.; Galle, P.R.; Llovet, J.M.; Assenat, E.; Brandi, G.; Pracht, M.; Lim, H.Y.; et al. Ramucirumab after Sorafenib in Patients with Advanced Hepatocellular Carcinoma and Increased α-Fetoprotein Concentrations (REACH-2): A Randomised, Double-Blind, Placebo-Controlled, Phase 3 Trial. Lancet Oncol. 2019, 20, 282–296. [Google Scholar] [CrossRef] [PubMed]
  11. Finn, R.S.; Qin, S.; Ikeda, M.; Galle, P.R.; Ducreux, M.; Kim, T.-Y.; Kudo, M.; Breder, V.; Merle, P.; Kaseb, A.O.; et al. Atezolizumab plus Bevacizumab in Unresectable Hepatocellular Carcinoma. N. Engl. J. Med. 2020, 382, 1894–1905. [Google Scholar] [CrossRef]
  12. Cheng, A.-L.; Qin, S.; Ikeda, M.; Galle, P.R.; Ducreux, M.; Kim, T.-Y.; Lim, H.Y.; Kudo, M.; Breder, V.; Merle, P.; et al. Updated Efficacy and Safety Data from IMbrave150: Atezolizumab plus Bevacizumab vs. Sorafenib for Unresectable Hepatocellular Carcinoma. J. Hepatol. 2022, 76, 862–873. [Google Scholar] [CrossRef] [PubMed]
  13. Montironi, C.; Castet, F.; Haber, P.K.; Pinyol, R.; Torres-Martin, M.; Torrens, L.; Mesropian, A.; Wang, H.; Puigvehi, M.; Maeda, M.; et al. Inflamed and Non-Inflamed Classes of HCC: A Revised Immunogenomic Classification. Gut 2023, 72, 129–140. [Google Scholar] [CrossRef] [PubMed]
  14. Donne, R.; Lujambio, A. The Liver Cancer Immune Microenvironment: Therapeutic Implications for Hepatocellular Carcinoma. Hepatology 2023, 77, 1773–1796. [Google Scholar] [CrossRef] [PubMed]
  15. Cheng, K.; Cai, N.; Zhu, J.; Yang, X.; Liang, H.; Zhang, W. Tumor-Associated Macrophages in Liver Cancer: From Mechanisms to Therapy. Cancer Commun. 2022, 42, 1112–1140. [Google Scholar] [CrossRef]
  16. Cassetta, L.; Pollard, J.W. Targeting Macrophages: Therapeutic Approaches in Cancer. Nat. Rev. Drug Discov. 2018, 17, 887–904. [Google Scholar] [CrossRef] [PubMed]
  17. Krenkel, O.; Tacke, F. Liver Macrophages in Tissue Homeostasis and Disease. Nat. Rev. Immunol. 2017, 17, 306–321. [Google Scholar] [CrossRef]
  18. Zheng, H.; Peng, X.; Yang, S.; Li, X.; Huang, M.; Wei, S.; Zhang, S.; He, G.; Liu, J.; Fan, Q.; et al. Targeting Tumor-Associated Macrophages in Hepatocellular Carcinoma: Biology, Strategy, and Immunotherapy. Cell Death Discov. 2023, 9, 65. [Google Scholar] [CrossRef]
  19. Ye, Y.-C.; Zhao, J.-L.; Lu, Y.-T.; Gao, C.-C.; Yang, Y.; Liang, S.-Q.; Lu, Y.-Y.; Wang, L.; Yue, S.-Q.; Dou, K.-F.; et al. NOTCH Signaling via WNT Regulates the Proliferation of Alternative, CCR2-Independent Tumor-Associated Macrophages in Hepatocellular Carcinoma. Cancer Res. 2019, 79, 4160–4172. [Google Scholar] [CrossRef] [PubMed]
  20. Song, G.; Shi, Y.; Zhang, M.; Goswami, S.; Afridi, S.; Meng, L.; Ma, J.; Chen, Y.; Lin, Y.; Zhang, J.; et al. Global Immune Characterization of HBV/HCV-Related Hepatocellular Carcinoma Identifies Macrophage and T-Cell Subsets Associated with Disease Progression. Cell Discov. 2020, 6, 90. [Google Scholar] [CrossRef] [PubMed]
  21. Sharma, A.; Seow, J.J.W.; Dutertre, C.-A.; Pai, R.; Blériot, C.; Mishra, A.; Wong, R.M.M.; Singh, G.S.N.; Sudhagar, S.; Khalilnezhad, S.; et al. Onco-Fetal Reprogramming of Endothelial Cells Drives Immunosuppressive Macrophages in Hepatocellular Carcinoma. Cell 2020, 183, 377–394.e21. [Google Scholar] [CrossRef] [PubMed]
  22. Guilliams, M.; Scott, C.L. Liver Macrophages in Health and Disease. Immunity 2022, 55, 1515–1529. [Google Scholar] [CrossRef]
  23. Qu, X.; Zhao, X.; Lin, K.; Wang, N.; Li, X.; Li, S.; Zhang, L.; Shi, Y. M2-like Tumor-Associated Macrophage-Related Biomarkers to Construct a Novel Prognostic Signature, Reveal the Immune Landscape, and Screen Drugs in Hepatocellular Carcinoma. Front. Immunol. 2022, 13, 994019. [Google Scholar] [CrossRef]
  24. Sun, Y.; Wu, L.; Zhong, Y.; Zhou, K.; Hou, Y.; Wang, Z.; Zhang, Z.; Xie, J.; Wang, C.; Chen, D.; et al. Single-Cell Landscape of the Ecosystem in Early-Relapse Hepatocellular Carcinoma. Cell 2021, 184, 404–421.e16. [Google Scholar] [CrossRef]
  25. Zhang, Q.; He, Y.; Luo, N.; Patel, S.J.; Han, Y.; Gao, R.; Modak, M.; Carotta, S.; Haslinger, C.; Kind, D.; et al. Landscape and Dynamics of Single Immune Cells in Hepatocellular Carcinoma. Cell 2019, 179, 829–845.e20. [Google Scholar] [CrossRef]
  26. Liu, Y.; Xun, Z.; Ma, K.; Liang, S.; Li, X.; Zhou, S.; Sun, L.; Liu, Y.; Du, Y.; Guo, X.; et al. Identification of a Tumour Immune Barrier in the HCC Microenvironment That Determines the Efficacy of Immunotherapy. J. Hepatol. 2023, 78, 770–782. [Google Scholar] [CrossRef]
  27. Lu, Y.; Yang, A.; Quan, C.; Pan, Y.; Zhang, H.; Li, Y.; Gao, C.; Lu, H.; Wang, X.; Cao, P.; et al. A Single-Cell Atlas of the Multicellular Ecosystem of Primary and Metastatic Hepatocellular Carcinoma. Nat. Commun. 2022, 13, 4594. [Google Scholar] [CrossRef]
  28. Gao, J.; Li, Z.; Lu, Q.; Zhong, J.; Pan, L.; Feng, C.; Tang, S.; Wang, X.; Tao, Y.; Lin, J.; et al. Single-Cell RNA Sequencing Reveals Cell Subpopulations in the Tumor Microenvironment Contributing to Hepatocellular Carcinoma. Front. cell Dev. Biol. 2023, 11, 1194199. [Google Scholar] [CrossRef] [PubMed]
  29. Liu, Y.; Zhang, L.; Ju, X.; Wang, S.; Qie, J. Single-Cell Transcriptomic Analysis Reveals Macrophage-Tumor Crosstalk in Hepatocellular Carcinoma. Front. Immunol. 2022, 13, 955390. [Google Scholar] [CrossRef] [PubMed]
  30. Ho, D.W.-H.; Tsui, Y.-M.; Chan, L.-K.; Sze, K.M.-F.; Zhang, X.; Cheu, J.W.-S.; Chiu, Y.-T.; Lee, J.M.-F.; Chan, A.C.-Y.; Cheung, E.T.-Y.; et al. Single-Cell RNA Sequencing Shows the Immunosuppressive Landscape and Tumor Heterogeneity of HBV-Associated Hepatocellular Carcinoma. Nat. Commun. 2021, 12, 3684. [Google Scholar] [CrossRef]
  31. Dong, L.-Q.; Peng, L.-H.; Ma, L.-J.; Liu, D.-B.; Zhang, S.; Luo, S.-Z.; Rao, J.-H.; Zhu, H.-W.; Yang, S.-X.; Xi, S.-J.; et al. Heterogeneous Immunogenomic Features and Distinct Escape Mechanisms in Multifocal Hepatocellular Carcinoma. J. Hepatol. 2020, 72, 896–908. [Google Scholar] [CrossRef]
  32. Liu, P.; Kong, L.; Liu, Y.; Li, G.; Xie, J.; Lu, X. A Key Driver to Promote HCC: Cellular Crosstalk in Tumor Microenvironment. Front. Oncol. 2023, 13, 1135122. [Google Scholar] [CrossRef]
  33. Sung, P.S. Crosstalk between Tumor-Associated Macrophages and Neighboring Cells in Hepatocellular Carcinoma. Clin. Mol. Hepatol. 2022, 28, 333–350. [Google Scholar] [CrossRef]
  34. Yeung, O.W.H.; Lo, C.-M.; Ling, C.-C.; Qi, X.; Geng, W.; Li, C.-X.; Ng, K.T.P.; Forbes, S.J.; Guan, X.-Y.; Poon, R.T.P.; et al. Alternatively Activated (M2) Macrophages Promote Tumour Growth and Invasiveness in Hepatocellular Carcinoma. J. Hepatol. 2015, 62, 607–616. [Google Scholar] [CrossRef]
  35. Dranoff, G. Cytokines in Cancer Pathogenesis and Cancer Therapy. Nat. Rev. Cancer 2004, 4, 11–22. [Google Scholar] [CrossRef] [PubMed]
  36. Xiao, P.; Long, X.; Zhang, L.; Ye, Y.; Guo, J.; Liu, P.; Zhang, R.; Ning, J.; Yu, W.; Wei, F.; et al. Neurotensin/IL-8 Pathway Orchestrates Local Inflammatory Response and Tumor Invasion by Inducing M2 Polarization of Tumor-Associated Macrophages and Epithelial-Mesenchymal Transition of Hepatocellular Carcinoma Cells. Oncoimmunology 2018, 7, e1440166. [Google Scholar] [CrossRef]
  37. Zhou, T.-Y.; Zhou, Y.-L.; Qian, M.-J.; Fang, Y.-Z.; Ye, S.; Xin, W.-X.; Yang, X.-C.; Wu, H.-H. Interleukin-6 Induced by YAP in Hepatocellular Carcinoma Cells Recruits Tumor-Associated Macrophages. J. Pharma. Sci. 2018, 138, 89–95. [Google Scholar] [CrossRef]
  38. Zhang, W.; Liu, Y.; Yan, Z.; Yang, H.; Sun, W.; Yao, Y.; Chen, Y.; Jiang, R. IL-6 Promotes PD-L1 Expression in Monocytes and Macrophages by Decreasing Protein Tyrosine Phosphatase Receptor Type O Expression in Human Hepatocellular Carcinoma. J. Immunother. Cancer 2020, 8, e000285. [Google Scholar] [CrossRef] [PubMed]
  39. He, Q.; Liu, M.; Huang, W.; Chen, X.; Zhang, B.; Zhang, T.; Wang, Y.; Liu, D.; Xie, M.; Ji, X.; et al. IL-1β-Induced Elevation of Solute Carrier Family 7 Member 11 Promotes Hepatocellular Carcinoma Metastasis Through Up-Regulating Programmed Death Ligand 1 and Colony-Stimulating Factor 1. Hepatology 2021, 74, 3174–3193. [Google Scholar] [CrossRef]
  40. Wei, C.-Y.; Zhu, M.-X.; Zhang, P.-F.; Huang, X.-Y.; Wan, J.-K.; Yao, X.-Z.; Hu, Z.-T.; Chai, X.-Q.; Peng, R.; Yang, X.; et al. PKCα/ZFP64/CSF1 Axis Resets the Tumor Microenvironment and Fuels Anti-PD1 Resistance in Hepatocellular Carcinoma. J. Hepatol. 2022, 77, 163–176. [Google Scholar] [CrossRef] [PubMed]
  41. Ao, J.-Y.; Zhu, X.-D.; Chai, Z.-T.; Cai, H.; Zhang, Y.-Y.; Zhang, K.-Z.; Kong, L.-Q.; Zhang, N.; Ye, B.-G.; Ma, D.-N.; et al. Colony-Stimulating Factor 1 Receptor Blockade Inhibits Tumor Growth by Altering the Polarization of Tumor-Associated Macrophages in Hepatocellular Carcinoma. Mol. Cancer Ther. 2017, 16, 1544–1554. [Google Scholar] [CrossRef] [PubMed]
  42. Zhu, Y.; Yang, J.; Xu, D.; Gao, X.-M.; Zhang, Z.; Hsu, J.L.; Li, C.-W.; Lim, S.-O.; Sheng, Y.-Y.; Zhang, Y.; et al. Disruption of Tumour-Associated Macrophage Trafficking by the Osteopontin-Induced Colony-Stimulating Factor-1 Signalling Sensitises Hepatocellular Carcinoma to Anti-PD-L1 Blockade. Gut 2019, 68, 1653–1666. [Google Scholar] [CrossRef]
  43. Liu, L.; Zhang, R.; Deng, J.; Dai, X.; Zhu, X.; Fu, Q.; Zhang, H.; Tong, Z.; Zhao, P.; Fang, W.; et al. Construction of TME and Identification of Crosstalk between Malignant Cells and Macrophages by SPP1 in Hepatocellular Carcinoma. Cancer Immunol. Immunother. 2022, 71, 121–136. [Google Scholar] [CrossRef] [PubMed]
  44. Cao, P.; Ma, B.; Sun, D.; Zhang, W.; Qiu, J.; Qin, L.; Xue, X. Hsa_circ_0003410 Promotes Hepatocellular Carcinoma Progression by Increasing the Ratio of M2/M1 Macrophages through the MiR-139-3p/CCL5 Axis. Cancer Sci. 2022, 113, 634–647. [Google Scholar] [CrossRef] [PubMed]
  45. Bao, D.; Zhao, J.; Zhou, X.; Yang, Q.; Chen, Y.; Zhu, J.; Yuan, P.; Yang, J.; Qin, T.; Wan, S.; et al. Mitochondrial Fission-Induced MtDNA Stress Promotes Tumor-Associated Macrophage Infiltration and HCC Progression. Oncogene 2019, 38, 5007–5020. [Google Scholar] [CrossRef]
  46. Yang, T.; Wang, Y.; Dai, W.; Zheng, X.; Wang, J.; Song, S.; Fang, L.; Zhou, J.; Wu, W.; Gu, J. Increased B3GALNT2 in Hepatocellular Carcinoma Promotes Macrophage Recruitment via Reducing Acetoacetate Secretion and Elevating MIF Activity. J. Hematol. Oncol. 2018, 11, 50. [Google Scholar] [CrossRef]
  47. Dong, N.; Shi, X.; Wang, S.; Gao, Y.; Kuang, Z.; Xie, Q.; Li, Y.; Deng, H.; Wu, Y.; Li, M.; et al. M2 Macrophages Mediate Sorafenib Resistance by Secreting HGF in a Feed-Forward Manner in Hepatocellular Carcinoma. Br. J. Cancer 2019, 121, 22–33. [Google Scholar] [CrossRef] [PubMed]
  48. Zhao, J.; Li, H.; Zhao, S.; Wang, E.; Zhu, J.; Feng, D.; Zhu, Y.; Dou, W.; Fan, Q.; Hu, J.; et al. Epigenetic Silencing of MiR-144/451a Cluster Contributes to HCC Progression via Paracrine HGF/MIF-Mediated TAM Remodeling. Mol. Cancer 2021, 20, 46. [Google Scholar] [CrossRef]
  49. Yang, Y.; Ye, Y.-C.; Chen, Y.; Zhao, J.-L.; Gao, C.-C.; Han, H.; Liu, W.-C.; Qin, H.-Y. Crosstalk between Hepatic Tumor Cells and Macrophages via Wnt/β-Catenin Signaling Promotes M2-like Macrophage Polarization and Reinforces Tumor Malignant Behaviors. Cell Death Dis. 2018, 9, 793. [Google Scholar] [CrossRef]
  50. Jiang, Y.; Han, Q.; Zhao, H.; Zhang, J. Promotion of Epithelial-Mesenchymal Transformation by Hepatocellular Carcinoma-Educated Macrophages through Wnt2b/β-Catenin/c-Myc Signaling and Reprogramming Glycolysis. J. Exp. Clin. Cancer Res. 2021, 40, 13. [Google Scholar] [CrossRef]
  51. Tian, X.; Wu, Y.; Yang, Y.; Wang, J.; Niu, M.; Gao, S.; Qin, T.; Bao, D. Long Noncoding RNA LINC00662 Promotes M2 Macrophage Polarization and Hepatocellular Carcinoma Progression via Activating Wnt/β-Catenin Signaling. Mol. Oncol. 2020, 14, 462–483. [Google Scholar] [CrossRef] [PubMed]
  52. Shiau, D.-J.; Kuo, W.-T.; Davuluri, G.V.N.; Shieh, C.-C.; Tsai, P.-J.; Chen, C.-C.; Lin, Y.-S.; Wu, Y.-Z.; Hsiao, Y.-P.; Chang, C.-P. Hepatocellular Carcinoma-Derived High Mobility Group Box 1 Triggers M2 Macrophage Polarization via a TLR2/NOX2/Autophagy Axis. Sci. Rep. 2020, 10, 13582. [Google Scholar] [CrossRef]
  53. Cui, X.; Zhao, H.; Wei, S.; Du, Q.; Dong, K.; Yan, Y.; Geller, D.A. Hepatocellular Carcinoma-Derived FOXO1 Inhibits Tumor Progression by Suppressing IL-6 Secretion from Macrophages. Neoplasia 2023, 40, 100900. [Google Scholar] [CrossRef]
  54. Baig, M.S.; Roy, A.; Rajpoot, S.; Liu, D.; Savai, R.; Banerjee, S.; Kawada, M.; Faisal, S.M.; Saluja, R.; Saqib, U.; et al. Tumor-Derived Exosomes in the Regulation of Macrophage Polarization. Inflamm. Res. 2020, 69, 435–451. [Google Scholar] [CrossRef]
  55. Han, Q.; Zhao, H.; Jiang, Y.; Yin, C.; Zhang, J. HCC-Derived Exosomes: Critical Player and Target for Cancer Immune Escape. Cells 2019, 8, 558. [Google Scholar] [CrossRef]
  56. Zhou, Z.; Wang, Z.; Gao, J.; Lin, Z.; Wang, Y.; Shan, P.; Li, M.; Zhou, T.; Li, P. Noncoding RNA-Mediated Macrophage and Cancer Cell Crosstalk in Hepatocellular Carcinoma. Mol. Ther. oncolytics 2022, 25, 98–120. [Google Scholar] [CrossRef]
  57. Yu, H.; Pan, J.; Zheng, S.; Cai, D.; Luo, A.; Xia, Z.; Huang, J. Hepatocellular Carcinoma Cell-Derived Exosomal MiR-21-5p Induces Macrophage M2 Polarization by Targeting RhoB. Int. J. Mol. Sci. 2023, 24, 4593. [Google Scholar] [CrossRef] [PubMed]
  58. Liu, J.; Fan, L.; Yu, H.; Zhang, J.; He, Y.; Feng, D.; Wang, F.; Li, X.; Liu, Q.; Li, Y.; et al. Endoplasmic Reticulum Stress Causes Liver Cancer Cells to Release Exosomal MiR-23a-3p and Up-Regulate Programmed Death Ligand 1 Expression in Macrophages. Hepatology 2019, 70, 241–258. [Google Scholar] [CrossRef]
  59. Chen, J.; Lin, Z.; Liu, L.; Zhang, R.; Geng, Y.; Fan, M.; Zhu, W.; Lu, M.; Lu, L.; Jia, H.; et al. GOLM1 Exacerbates CD8+ T Cell Suppression in Hepatocellular Carcinoma by Promoting Exosomal PD-L1 Transport into Tumor-Associated Macrophages. Signal Transduct. Target. Ther. 2021, 6, 397. [Google Scholar] [CrossRef] [PubMed]
  60. Yin, C.; Han, Q.; Xu, D.; Zheng, B.; Zhao, X.; Zhang, J. SALL4-Mediated Upregulation of Exosomal MiR-146a-5p Drives T-Cell Exhaustion by M2 Tumor-Associated Macrophages in HCC. Oncoimmunology 2019, 8, 1601479. [Google Scholar] [CrossRef] [PubMed]
  61. Zongqiang, H.; Jiapeng, C.; Yingpeng, Z.; Chuntao, Y.; Yiting, W.; Jiashun, Z.; Li, L. Exosomal MiR-452-5p Induce M2 Macrophage Polarization to Accelerate Hepatocellular Carcinoma Progression by Targeting TIMP3. J. Immunol. Res. 2022, 2022, 1032106. [Google Scholar] [CrossRef]
  62. Guan, L.; Hao, Q.; Shi, F.; Gao, B.; Wang, M.; Zhou, X.; Han, T.; Ren, W. Regulation of the Tumor Immune Microenvironment by Cancer-Derived Circular RNAs. Cell Death Dis. 2023, 14, 132. [Google Scholar] [CrossRef] [PubMed]
  63. Lu, J.-C.; Zhang, P.-F.; Huang, X.-Y.; Guo, X.-J.; Gao, C.; Zeng, H.-Y.; Zheng, Y.-M.; Wang, S.-W.; Cai, J.-B.; Sun, Q.-M.; et al. Amplification of Spatially Isolated Adenosine Pathway by Tumor-Macrophage Interaction Induces Anti-PD1 Resistance in Hepatocellular Carcinoma. J. Hematol. Oncol. 2021, 14, 200. [Google Scholar] [CrossRef] [PubMed]
  64. Wang, Y.; Gao, R.; Li, J.; Tang, S.; Li, S.; Tong, Q.; Li, S. Downregulation of Hsa_circ_0074854 Suppresses the Migration and Invasion in Hepatocellular Carcinoma via Interacting with HuR and via Suppressing Exosomes-Mediated Macrophage M2 Polarization. Int. J. Nanomed. 2021, 16, 2803–2818. [Google Scholar] [CrossRef]
  65. Zhang, J.; Zhang, Q.; Lou, Y.; Fu, Q.; Chen, Q.; Wei, T.; Yang, J.; Tang, J.; Wang, J.; Chen, Y.; et al. Hypoxia-Inducible Factor-1α/Interleukin-1β Signaling Enhances Hepatoma Epithelial-Mesenchymal Transition through Macrophages in a Hypoxic-Inflammatory Microenvironment. Hepatology 2018, 67, 1872–1889. [Google Scholar] [CrossRef]
  66. Wan, S.; Zhao, E.; Kryczek, I.; Vatan, L.; Sadovskaya, A.; Ludema, G.; Simeone, D.M.; Zou, W.; Welling, T.H. Tumor-Associated Macrophages Produce Interleukin 6 and Signal via STAT3 to Promote Expansion of Human Hepatocellular Carcinoma Stem Cells. Gastroenterology 2014, 147, 1393–1404. [Google Scholar] [CrossRef] [PubMed]
  67. Kong, L.; Zhou, Y.; Bu, H.; Lv, T.; Shi, Y.; Yang, J. Deletion of Interleukin-6 in Monocytes/Macrophages Suppresses the Initiation of Hepatocellular Carcinoma in Mice. J. Exp. Clin. Cancer Res. 2016, 35, 131. [Google Scholar] [CrossRef] [PubMed]
  68. Jiang, J.; Wang, G.-Z.; Wang, Y.; Huang, H.-Z.; Li, W.-T.; Qu, X.-D. Hypoxia-Induced HMGB1 Expression of HCC Promotes Tumor Invasiveness and Metastasis via Regulating Macrophage-Derived IL-6. Exp. Cell Res. 2018, 367, 81–88. [Google Scholar] [CrossRef]
  69. Fu, X.-T.; Dai, Z.; Song, K.; Zhang, Z.-J.; Zhou, Z.-J.; Zhou, S.-L.; Zhao, Y.-M.; Xiao, Y.-S.; Sun, Q.-M.; Ding, Z.-B.; et al. Macrophage-Secreted IL-8 Induces Epithelial-Mesenchymal Transition in Hepatocellular Carcinoma Cells by Activating the JAK2/STAT3/Snail Pathway. Int. J. Oncol. 2015, 46, 587–596. [Google Scholar] [CrossRef] [PubMed]
  70. Chen, Y.; Wen, H.; Zhou, C.; Su, Q.; Lin, Y.; Xie, Y.; Huang, Y.; Qiu, Q.; Lin, J.; Huang, X.; et al. TNF-α Derived from M2 Tumor-Associated Macrophages Promotes Epithelial-Mesenchymal Transition and Cancer Stemness through the Wnt/β-Catenin Pathway in SMMC-7721 Hepatocellular Carcinoma Cells. Exp. Cell Res. 2019, 378, 41–50. [Google Scholar] [CrossRef] [PubMed]
  71. Zhu, F.; Li, X.; Chen, S.; Zeng, Q.; Zhao, Y.; Luo, F. Tumor-Associated Macrophage or Chemokine Ligand CCL17 Positively Regulates the Tumorigenesis of Hepatocellular Carcinoma. Med. Oncol. 2016, 33, 17. [Google Scholar] [CrossRef]
  72. Fan, Q.-M.; Jing, Y.-Y.; Yu, G.-F.; Kou, X.-R.; Ye, F.; Gao, L.; Li, R.; Zhao, Q.-D.; Yang, Y.; Lu, Z.-H.; et al. Tumor-Associated Macrophages Promote Cancer Stem Cell-like Properties via Transforming Growth Factor-Beta1-Induced Epithelial-Mesenchymal Transition in Hepatocellular Carcinoma. Cancer Lett. 2014, 352, 160–168. [Google Scholar] [CrossRef]
  73. Wei, R.; Zhu, W.-W.; Yu, G.-Y.; Wang, X.; Gao, C.; Zhou, X.; Lin, Z.-F.; Shao, W.-Q.; Wang, S.-H.; Lu, M.; et al. S100 Calcium-Binding Protein A9 from Tumor-Associated Macrophage Enhances Cancer Stem Cell-like Properties of Hepatocellular Carcinoma. Int. J. Cancer 2021, 148, 1233–1244. [Google Scholar] [CrossRef] [PubMed]
  74. Davuluri, G.V.N.; Chen, C.-C.; Chiu, Y.-C.; Tsai, H.-W.; Chiu, H.-C.; Chen, Y.-L.; Tsai, P.-J.; Kuo, W.-T.; Tsao, N.; Lin, Y.-S.; et al. Autophagy Drives Galectin-1 Secretion From Tumor-Associated Macrophages Facilitating Hepatocellular Carcinoma Progression. Front. Cell Dev. Biol. 2021, 9, 741820. [Google Scholar] [CrossRef]
  75. Yang, S.; Zhang, J.; Xu, Y.; Wang, J.; Zhao, H.; Lei, J.; Zhou, Y.; Chen, Y.; Wu, L.; Zhou, M.; et al. OIT3 Mediates Macrophage Polarization and Facilitates Hepatocellular Carcinoma Progression. Cancer Immunol. Immunother. 2022, 71, 2677–2689. [Google Scholar] [CrossRef] [PubMed]
  76. Wen, J.; Yang, S.; Yan, G.; Lei, J.; Liu, X.; Zhang, N.; Zhang, J.; Deng, H.; Wu, L.; Li, Y. Increased OIT3 in Macrophages Promotes PD-L1 Expression and Hepatocellular Carcinogenesis via NF-ΚB Signaling. Exp. Cell Res. 2023, 428, 113651. [Google Scholar] [CrossRef]
  77. Ning, J.; Ye, Y.; Bu, D.; Zhao, G.; Song, T.; Liu, P.; Yu, W.; Wang, H.; Li, H.; Ren, X.; et al. Imbalance of TGF-Β1/BMP-7 Pathways Induced by M2-Polarized Macrophages Promotes Hepatocellular Carcinoma Aggressiveness. Mol. Ther. 2021, 29, 2067–2087. [Google Scholar] [CrossRef] [PubMed]
  78. Li, W.; Xin, X.; Li, X.; Geng, J.; Sun, Y. Exosomes Secreted by M2 Macrophages Promote Cancer Stemness of Hepatocellular Carcinoma via the MiR-27a-3p/TXNIP Pathways. Int. Immunopharmacol. 2021, 101, 107585. [Google Scholar] [CrossRef] [PubMed]
  79. Liu, G.; Ouyang, X.; Sun, Y.; Xiao, Y.; You, B.; Gao, Y.; Yeh, S.; Li, Y.; Chang, C. The MiR-92a-2-5p in Exosomes from Macrophages Increases Liver Cancer Cells Invasion via Altering the AR/PHLPP/p-AKT/β-Catenin Signaling. Cell Death Differ. 2020, 27, 3258–3272. [Google Scholar] [CrossRef]
  80. Tian, B.; Zhou, L.; Wang, J.; Yang, P. MiR-660-5p-Loaded M2 Macrophages-Derived Exosomes Augment Hepatocellular Carcinoma Development through Regulating KLF3. Int. Immunopharmacol. 2021, 101, 108157. [Google Scholar] [CrossRef]
  81. Xu, M.; Zhou, C.; Weng, J.; Chen, Z.; Zhou, Q.; Gao, J.; Shi, G.; Ke, A.; Ren, N.; Sun, H.; et al. Tumor Associated Macrophages-Derived Exosomes Facilitate Hepatocellular Carcinoma Malignance by Transferring LncMMPA to Tumor Cells and Activating Glycolysis Pathway. J. Exp. Clin. Cancer Res. 2022, 41, 253. [Google Scholar] [CrossRef] [PubMed]
  82. Wang, L.; Yi, X.; Xiao, X.; Zheng, Q.; Ma, L.; Li, B. Exosomal MiR-628-5p from M1 Polarized Macrophages Hinders M6A Modification of CircFUT8 to Suppress Hepatocellular Carcinoma Progression. Cell. Mol. Biol. Lett. 2022, 27, 106. [Google Scholar] [CrossRef] [PubMed]
  83. Li, X.; Yao, W.; Yuan, Y.; Chen, P.; Li, B.; Li, J.; Chu, R.; Song, H.; Xie, D.; Jiang, X.; et al. Targeting of Tumour-Infiltrating Macrophages via CCL2/CCR2 Signalling as a Therapeutic Strategy against Hepatocellular Carcinoma. Gut 2017, 66, 157–167. [Google Scholar] [CrossRef]
  84. Yao, W.; Ba, Q.; Li, X.; Li, H.; Zhang, S.; Yuan, Y.; Wang, F.; Duan, X.; Li, J.; Zhang, W.; et al. A Natural CCR2 Antagonist Relieves Tumor-Associated Macrophage-Mediated Immunosuppression to Produce a Therapeutic Effect for Liver Cancer. EBioMedicine 2017, 22, 58–67. [Google Scholar] [CrossRef] [PubMed]
  85. Stanley, E.R.; Chitu, V. CSF-1 Receptor Signaling in Myeloid Cells. Cold Spring Harb. Perspect. Biol. 2014, 6, a021857. [Google Scholar] [CrossRef]
  86. Ries, C.H.; Cannarile, M.A.; Hoves, S.; Benz, J.; Wartha, K.; Runza, V.; Rey-Giraud, F.; Pradel, L.P.; Feuerhake, F.; Klaman, I.; et al. Targeting Tumor-Associated Macrophages with Anti-CSF-1R Antibody Reveals a Strategy for Cancer Therapy. Cancer Cell 2014, 25, 846–859. [Google Scholar] [CrossRef]
  87. Kim, S.-M.; Kim, S.Y.; Park, C.S.; Chang, H.-S.; Park, K.C. Impact of Age-Related Genetic Differences on the Therapeutic Outcome of Papillary Thyroid Cancer. Cancers 2020, 12, 448. [Google Scholar] [CrossRef]
  88. Kato, Y.; Tabata, K.; Kimura, T.; Yachie-Kinoshita, A.; Ozawa, Y.; Yamada, K.; Ito, J.; Tachino, S.; Hori, Y.; Matsuki, M.; et al. Lenvatinib plus Anti-PD-1 Antibody Combination Treatment Activates CD8+ T Cells through Reduction of Tumor-Associated Macrophage and Activation of the Interferon Pathway. PLoS ONE 2019, 14, e0212513. [Google Scholar] [CrossRef]
  89. Kowal, J.; Kornete, M.; Joyce, J.A. Re-Education of Macrophages as a Therapeutic Strategy in Cancer. Immunotherapy 2019, 11, 677–689. [Google Scholar] [CrossRef]
  90. Kaneda, M.M.; Messer, K.S.; Ralainirina, N.; Li, H.; Leem, C.J.; Gorjestani, S.; Woo, G.; Nguyen, A.V.; Figueiredo, C.C.; Foubert, P.; et al. PI3Kγ Is a Molecular Switch That Controls Immune Suppression. Nature 2016, 539, 437–442. [Google Scholar] [CrossRef]
  91. Chen, Y.; Ramjiawan, R.R.; Reiberger, T.; Ng, M.R.; Hato, T.; Huang, Y.; Ochiai, H.; Kitahara, S.; Unan, E.C.; Reddy, T.P.; et al. CXCR4 Inhibition in Tumor Microenvironment Facilitates Anti-Programmed Death Receptor-1 Immunotherapy in Sorafenib-Treated Hepatocellular Carcinoma in Mice. Hepatology 2015, 61, 1591–1602. [Google Scholar] [CrossRef]
  92. Wang, H.-C.; Haung, L.-Y.; Wang, C.-J.; Chao, Y.-J.; Hou, Y.-C.; Yen, C.-J.; Shan, Y.-S. Tumor-Associated Macrophages Promote Resistance of Hepatocellular Carcinoma Cells against Sorafenib by Activating CXCR2 Signaling. J. Biomed. Sci. 2022, 29, 99. [Google Scholar] [CrossRef] [PubMed]
  93. Li, G.; Zhao, L. Sorafenib-Loaded Hydroxyethyl Starch-TG100-115 Micelles for the Treatment of Liver Cancer Based on Synergistic Treatment. Drug Deliv. 2019, 26, 756–764. [Google Scholar] [CrossRef]
  94. Lourenço, A.R.; Coffer, P.J. A Tumor Suppressor Role for C/EBPα in Solid Tumors: More than Fat and Blood. Oncogene 2017, 36, 5221–5230. [Google Scholar] [CrossRef]
  95. Hashimoto, A.; Sarker, D.; Reebye, V.; Jarvis, S.; Sodergren, M.H.; Kossenkov, A.; Sanseviero, E.; Raulf, N.; Vasara, J.; Andrikakou, P.; et al. Upregulation of C/EBPα Inhibits Suppressive Activity of Myeloid Cells and Potentiates Antitumor Response in Mice and Patients with Cancer. Clin. Cancer Res. 2021, 27, 5961–5978. [Google Scholar] [CrossRef] [PubMed]
  96. Sun, G.; Liu, H.; Zhao, J.; Zhang, J.; Huang, T.; Sun, G.; Zhao, S.; Zhang, Z.; Cao, H.; Rong, D.; et al. Macrophage GSK3β-Deficiency Inhibits the Progression of Hepatocellular Carcinoma and Enhances the Sensitivity of Anti-PD1 Immunotherapy. J. Immunother. Cancer 2022, 10, e005655. [Google Scholar] [CrossRef]
  97. Wu, L.; Zhang, X.; Zheng, L.; Zhao, H.; Yan, G.; Zhang, Q.; Zhou, Y.; Lei, J.; Zhang, J.; Wang, J.; et al. RIPK3 Orchestrates Fatty Acid Metabolism in Tumor-Associated Macrophages and Hepatocarcinogenesis. Cancer Immunol. Res. 2020, 8, 710–721. [Google Scholar] [CrossRef] [PubMed]
  98. Rodell, C.B.; Arlauckas, S.P.; Cuccarese, M.F.; Garris, C.S.; Li, R.; Ahmed, M.S.; Kohler, R.H.; Pittet, M.J.; Weissleder, R. TLR7/8-Agonist-Loaded Nanoparticles Promote the Polarization of Tumour-Associated Macrophages to Enhance Cancer Immunotherapy. Nat. Biomed. Eng. 2018, 2, 578–588. [Google Scholar] [CrossRef]
  99. Zhang, X.; Wei, Z.; Yong, T.; Li, S.; Bie, N.; Li, J.; Li, X.; Liu, H.; Xu, H.; Yan, Y.; et al. Cell Microparticles Loaded with Tumor Antigen and Resiquimod Reprogram Tumor-Associated Macrophages and Promote Stem-like CD8+ T Cells to Boost Anti-PD-1 Therapy. Nat. Commun. 2023, 14, 5653. [Google Scholar] [CrossRef]
  100. Yoo, C.; Verdaguer, H.; Lin, C.-C.; Qvortrup, C.; Yau, T.; Oh, D.-Y.; Lichtenegger, F.; Franjkovic, I.; Kratochwil, N.; Bessa, J.; et al. Abstract CT096: Phase 1 Study of RO7119929 (TLR7 Agonist Prodrug) in Patients (Pts) with Advanced Primary or Metastatic Liver Cancers. Cancer Res. 2023, 83, CT096. [Google Scholar] [CrossRef]
  101. Chen, J.; Zheng, D.-X.; Yu, X.-J.; Sun, H.-W.; Xu, Y.-T.; Zhang, Y.-J.; Xu, J. Macrophages Induce CD47 Upregulation via IL-6 and Correlate with Poor Survival in Hepatocellular Carcinoma Patients. Oncoimmunology 2019, 8, e1652540. [Google Scholar] [CrossRef]
  102. Xiao, Z.; Chung, H.; Banan, B.; Manning, P.T.; Ott, K.C.; Lin, S.; Capoccia, B.J.; Subramanian, V.; Hiebsch, R.R.; Upadhya, G.A.; et al. Antibody Mediated Therapy Targeting CD47 Inhibits Tumor Progression of Hepatocellular Carcinoma. Cancer Lett. 2015, 360, 302–309. [Google Scholar] [CrossRef] [PubMed]
  103. Lo, J.; Lau, E.Y.T.; So, F.T.Y.; Lu, P.; Chan, V.S.F.; Cheung, V.C.H.; Ching, R.H.H.; Cheng, B.Y.L.; Ma, M.K.F.; Ng, I.O.L.; et al. Anti-CD47 Antibody Suppresses Tumour Growth and Augments the Effect of Chemotherapy Treatment in Hepatocellular Carcinoma. Liver Int. 2016, 36, 737–745. [Google Scholar] [CrossRef]
  104. Klichinsky, M.; Ruella, M.; Shestova, O.; Lu, X.M.; Best, A.; Zeeman, M.; Schmierer, M.; Gabrusiewicz, K.; Anderson, N.R.; Petty, N.E.; et al. Human Chimeric Antigen Receptor Macrophages for Cancer Immunotherapy. Nat. Biotechnol. 2020, 38, 947–953. [Google Scholar] [CrossRef] [PubMed]
  105. Yang, Z.; Liu, Y.; Zhao, K.; Jing, W.; Gao, L.; Dong, X.; Wang, Y.; Han, M.; Shi, C.; Tang, C.; et al. Dual MRNA Co-Delivery for in Situ Generation of Phagocytosis-Enhanced CAR Macrophages Augments Hepatocellular Carcinoma Immunotherapy. J. Control. Release 2023, 360, 718–733. [Google Scholar] [CrossRef] [PubMed]
  106. Kumar, M.P.; Du, J.; Lagoudas, G.; Jiao, Y.; Sawyer, A.; Drummond, D.C.; Lauffenburger, D.A.; Raue, A. Analysis of Single-Cell RNA-Seq Identifies Cell-Cell Communication Associated with Tumor Characteristics. Cell Rep. 2018, 25, 1458–1468.e4. [Google Scholar] [CrossRef]
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MDPI and ACS Style

Agirre-Lizaso, A.; Huici-Izagirre, M.; Urretabizkaia-Garmendia, J.; Rodrigues, P.M.; Banales, J.M.; Perugorria, M.J. Targeting the Heterogeneous Tumour-Associated Macrophages in Hepatocellular Carcinoma. Cancers 2023, 15, 4977. https://doi.org/10.3390/cancers15204977

AMA Style

Agirre-Lizaso A, Huici-Izagirre M, Urretabizkaia-Garmendia J, Rodrigues PM, Banales JM, Perugorria MJ. Targeting the Heterogeneous Tumour-Associated Macrophages in Hepatocellular Carcinoma. Cancers. 2023; 15(20):4977. https://doi.org/10.3390/cancers15204977

Chicago/Turabian Style

Agirre-Lizaso, Aloña, Maider Huici-Izagirre, Josu Urretabizkaia-Garmendia, Pedro M. Rodrigues, Jesus M. Banales, and Maria J. Perugorria. 2023. "Targeting the Heterogeneous Tumour-Associated Macrophages in Hepatocellular Carcinoma" Cancers 15, no. 20: 4977. https://doi.org/10.3390/cancers15204977

APA Style

Agirre-Lizaso, A., Huici-Izagirre, M., Urretabizkaia-Garmendia, J., Rodrigues, P. M., Banales, J. M., & Perugorria, M. J. (2023). Targeting the Heterogeneous Tumour-Associated Macrophages in Hepatocellular Carcinoma. Cancers, 15(20), 4977. https://doi.org/10.3390/cancers15204977

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