Search Results (201)

Brain metastases in hormone receptor-positive metastatic breast cancer remain incompletely characterized at the molecular level. We report isolated central nervous system progression in a 60-year-old woman with hormone receptor-positive breast cancer initially diagnosed at the age of 38 and metastatic recurrence diagnosed at the age of 55. After approximately five years of extracranial disease control with letrozole plus palbociclib, she developed multiple brain metastases, including a large cerebellar lesion requiring surgical resection. Molecular profiling of the resected lesion identified ESR1 Y537S and ERBB2 Y772_A775dup, whereas postoperative plasma circulating tumor DNA analyzed using a sensitive next-generation sequencing assay showed no detectable somatic alteration. Extracranial disease remained in complete metabolic response. This tissue–plasma discordance is compatible with spatial genomic heterogeneity but may also reflect a low circulating tumor fraction, postoperative reduction in tumor burden, and limited release of tumor-derived DNA from CNS lesions into the systemic circulation. This case highlights the limitations of plasma circulating tumor DNA for evaluating CNS-limited progression and supports direct molecular profiling of brain metastases when tissue is available. Full article

Background/Objectives: Extra virgin olive oil (EVOO), a key component of the Mediterranean diet, has attracted research interest because olive-derived phenolics demonstrate potential anticancer activity in experimental models. This review summarizes evidence concerning whole EVOO, phenolic-enriched EVOO, olive phenolic extracts, and the isolated compounds hydroxytyrosol, oleuropein, oleocanthal, and oleacein. Methods: A structured narrative search of PubMed, Web of Science, ScienceDirect, and Google Scholar was conducted for literature published between 2015 and 2025. Evidence was reviewed for breast, prostate, colorectal, pancreatic, bone, oral, liver, gastric, hematological, and brain cancers. Comparatively limited evidence concerning cervical, endometrial, ovarian, melanoma, non-melanoma skin, and thyroid cancers was summarized separately. Results: The molecular evidence was derived primarily from cell culture and animal studies using isolated phenolics and concentrated extracts. Preclinical studies indicate that EVOO phenolics may demonstrate anticancer activity through multiple mechanisms, including antioxidant activity, anti-inflammatory effects, cell cycle arrest, induction of apoptosis, inhibition of metastasis, anti-angiogenic activity, and modulation of key signaling pathways, such as PI3K/AKT/mTOR, MAPK/ERK, NF-κB, JAK/STAT, Wnt/β-catenin, p53, and epithelial–mesenchymal transition-related pathways. Most molecular and pathway-level evidence was obtained using isolated phenolic compounds in cell culture or animal models, whereas evidence directly examining whole EVOO consumption was largely observational and substantially more limited. Experimental studies also reported that oleocanthal induced lysosomal membrane permeabilization, whereas hydroxytyrosol and oleuropein promoted mitochondria-mediated apoptosis. Furthermore, preclinical combination studies suggested enhanced tumor-cell sensitivity to selected chemotherapeutic, targeted, and immunotherapeutic agents. However, these effects have not been established in patients. Human evidence remains limited mainly to observational dietary associations and small exploratory interventions, with no conclusive demonstration of cancer prevention or therapeutic efficacy. Conclusions: Isolated EVOO-derived phenolic compounds demonstrated promising anticancer mechanisms in preclinical models. However, these results should not be directly extrapolated to dietary EVOO because experimentally administered doses, bioavailability, metabolism, and food-matrix interactions differ substantially from human dietary exposure. Therefore, well-designed studies using chemically characterized EVOO, pharmacokinetic investigations, and controlled human trials are required before dietary or clinical recommendations can be made. Full article

Drug repurposing represents a rational and resource-efficient strategy to expand the oncological armamentarium by leveraging the established pharmacology, clinical experience, and safety-monitoring frameworks of approved non-oncological agents. Clozapine (CZP), an atypical antipsychotic characterized by broad receptor pharmacology, complex biotransformation, and clinically relevant toxicological liabilities, has emerged as a candidate of interest following preclinical evidence of context-dependent anticancer activity across multiple tumor types. As such, CZP provides an informative case study at the interface between therapeutic drug action and xenobiotic behavior. This review provides a critical and integrated synthesis of the current evidence supporting the repurposing of CZP in oncology, with particular emphasis on the relationship between its molecular mechanisms, dose–exposure requirements, pharmacological complexity, and potential toxicity. Analysis of in vitro and in vivo studies across glioblastoma, non-small cell lung cancer, breast cancer, and melanoma brain metastasis models indicates that CZP can impair tumor cell proliferation and survival through a form of mechanistic plasticity. Rather than acting through a single conserved pathway, CZP appears to disrupt shared upstream processes related to pro-survival signaling, cellular stress tolerance, and metabolic homeostasis, while engaging tumor-specific downstream responses, including autophagic cell death, mitochondria-dependent apoptosis, oxidative stress, and coordinated modulation of survival and angiogenic pathways. Despite this mechanistic rationale, translation remains substantially constrained, most notably by the order of magnitude gap between anticancer-effective concentrations in vitro and clinically achievable plasma exposures, requiring careful distinction between potentially useful anticancer pharmacology and nonspecific xenobiotic-induced cellular stress and clinically unacceptable toxicity. Key limitations include the discrepancy between anticancer-effective concentrations observed in vitro and exposures achievable during standard psychiatric dosing, the limited understanding of how CZP metabolism and metabolite formation may influence efficacy and toxicity, the absence of integrated pharmacokinetic–pharmacodynamic and toxicokinetic modeling, and the lack of dedicated clinical trial evidence. To address these challenges, this review examines complementary translational strategies, including patient-derived organoids, co-culture systems, microphysiological platforms, pharmacokinetic and toxicological modeling, and computational digital twin frameworks. Together, these approaches may support a biologically informed and risk-aware evaluation of CZP, helping to identify responsive tumor contexts, anticipate exposure-related liabilities, and prioritize rational combination strategies. By integrating therapeutic potential with xenobiotic pharmacology and toxicology, this review positions CZP within the evolving landscape of precision oncology and evidence-driven drug repurposing. Full article

Background: Breast cancer with isolated bone metastases at initial diagnosis represents a clinically distinct metastatic phenotype, often associated with more indolent biology and relatively favorable outcomes compared with visceral metastatic disease. The survival impact of resecting the intact primary breast tumor in de novo metastatic breast cancer remains controversial. In this study, we evaluated the association between primary breast surgery and overall survival (OS), defined as the time from diagnosis to death attributable to breast cancer, in patients presenting with isolated bone metastatic breast cancer. Methods: We performed a retrospective population-based cohort study using the Surveillance, Epidemiology, and End Results (SEER) database. Because the SEER variable for bone metastasis at diagnosis is available from 2010 onward and HER2-defined subtype information is available in the modern SEER era, the effective study period was defined as 2010–2021 rather than the full 2000–2021 SEER release period. Patients with breast cancer and isolated bone metastases at presentation, without evidence of lung, liver, brain, or other distant metastatic sites at diagnosis, were included. Demographic and clinicopathological variables, including age, sex, race, biologic subtype, histology, chemotherapy, radiotherapy, and primary breast surgery, were analyzed. Overall survival (OS), defined as the time from diagnosis to death attributable to breast cancer, was estimated using Kaplan–Meier methods and compared using the log-rank test. Independent prognostic factors were evaluated using multivariable Cox proportional hazards modeling. Results: A total of 6500 eligible patients were identified. Surgery of the primary breast tumor was performed in 1513 (23.3%) patients, and 62.8% received chemotherapy. Five-year overall survival (OS) was significantly higher among patients who underwent surgery than among those who did not undergo surgery (59.5% vs. 38.6%; p < 0.001). In multivariable analysis, primary breast surgery remained independently associated with improved OS (hazard ratio [HR] 0.54, 95% CI 0.48–0.62; p < 0.001). Age, histology, chemotherapy, radiotherapy, and biologic subtype were also associated with prognosis. Sex was not significant in the unadjusted analysis (p = 0.188), and the multivariable sex finding was interpreted cautiously because only 96 men were included. Conclusions: In this population-based cohort of patients with de novo breast cancer and isolated bone metastases, primary breast surgery was associated with improved survival among selected patients. However, this association should not be interpreted as causal, given the inherent limitations of observational registry data, including treatment selection, potential immortal-time bias, unmeasured metastatic burden, performance status, systemic therapy type and response, and local symptom burden, which are not fully captured in SEER. These findings support careful multidisciplinary consideration of local therapy in selected patients, while emphasizing the need for confirmation in prospectively designed studies. Full article

We report an unusual case of brain radionecrosis following fractionated stereotactic radiotherapy (FSRT) delivered to a calvarial metastasis in a patient with metastatic luminal A breast cancer. A 40-year-old woman developed three subcentimetric brain lesions during follow-up, initially interpreted as new metastases and treated with FSRT. Subsequent radiological progression and advanced imaging suggested radionecrosis, which was confirmed histologically after surgical resection. Retrospective dosimetric analysis revealed that all lesions arose within the high-dose isodose region of the previously irradiated skull metastasis, despite compliance with established brain dose constraints. This case highlights a previously unreported risk of brain radionecrosis after stereotactic irradiation of skull bone metastases and underscores the need for caution in treatment planning and imaging interpretation. Full article

Objective: This study aimed to evaluate the prognostic significance of positron emission tomography/computed tomography (PET/CT)-derived sarcopenia in patients with hormone receptor-positive, HER2-negative metastatic breast cancer treated with cyclin-dependent kinase 4/6 (CDK4/6) inhibitors. Methods: This retrospective single-center study included 77 patients treated between January 2018 and March 2025. Sarcopenia was assessed using skeletal muscle index (SMI) at the L3 level on fluorodeoxyglucose (FDG) PET/CT. Patients were classified as sarcopenic or non-sarcopenic. Clinical, nutritional parameters including body mass index (BMI) and prognostic nutritional index (PNI), and inflammatory parameters including pan-immune inflammation value (PIV) were analyzed. The primary endpoint was progression-free survival (PFS). Results: Sarcopenia was present in 35.1% of patients. After a median follow-up of 38 months, sarcopenic patients had significantly shorter PFS compared with non-sarcopenic patients (18 vs. 38 months; HR: 2.37, 95% CI 1.12–4.99, p = 0.02, multivariable analysis). In multivariable analysis, sarcopenia, recurrent disease, brain metastasis, and liver metastasis were independent predictors of PFS. No significant association was observed between sarcopenia and overall survival. BMI, PNI, and PIV were not associated with survival outcomes. Toxicity profiles were comparable between groups. Conclusions: PET/CT-derived sarcopenia may be a prognostic factor for PFS in patients receiving CDK4/6 inhibitors, whereas conventional nutritional and inflammatory markers are not. These findings support the clinical utility of imaging-based body composition assessment. Prospective studies incorporating functional measures of sarcopenia are warranted. Full article

Background/Objectives: CD138 (syndecan-1) is a cell-surface heparan sulfate proteoglycan involved in cell–matrix interactions and growth factor signaling, and it has been implicated in tumor progression. However, the clinical significance of compartment-specific CD138 expression in breast cancer remains unclear. In this study, we investigated the prognostic and transcriptomic features of compartment-specific CD138 expression in invasive breast cancer. Methods: We performed an integrated analysis of immunohistochemistry and RNA sequencing of 111 invasive ductal carcinoma specimens. Tumors were classified into four groups according to CD138 expression in the tumor and stromal compartments. Clinicopathological data and survival outcomes were obtained from medical records, and transcriptomic profiles were analyzed using RNA sequencing. Results: The tumor-positive/stroma-negative phenotype (Group 1) was associated with poorer recurrence-free survival than the other phenotypes. According to multivariable Cox regression analysis, Group 1 remained an independent prognostic factor after adjustment for age, lymph node status, and Ki-67 index (hazard ratio, 5.493; p = 0.0028). Group 1 was also associated with lymph node metastasis and HER2 expression. All brain metastases occurred in Group 1, although the number of events was low. Transcriptomic profiling identified the upregulation of small nucleolar RNAs in Group 1 tumors, with the enrichment of pathways related to ribosome biogenesis, RNA processing, and translational regulation. Conclusions: Compartment-specific CD138 expression identifies an aggressive breast cancer phenotype with distinct transcriptomic features. This phenotype may have prognostic value and warrants validation using larger, independent cohorts. Full article

Breast cancer brain metastasis (BCBM) affects up to 30% of patients with metastatic disease and carries a median survival of only 4–18 months. Emerging evidence reveals that BCBM cells are not passive survivors, but active participants that hijack core neurotransmitter networks, GABA (gamma-aminobutyric acid) and glutamate, to fuel their growth. BCBM, particularly triple-negative breast cancer (TNBC), frequently switch to a GABAergic mode utilizing brain-derived GABA as an oncometabolite. In parallel, BCBM cells can also form direct synapses with neurons, tapping into excitatory input through glutamatergic receptors to drive tumor cell proliferation and survival. Concurrently, reprogrammed astrocytes establish gap junctions, secrete growth factors, and provide metabolic support. Together, tumor cells, neurons, and astrocytes form a pathological partnership locked in feedback loops sustaining metastatic progression. This review focuses on the unique mechanisms employed by distinct breast cancer subtypes and maps the metastatic progression from pre-metastatic to mature brain metastatic niche formation of BCBM. We highlight opportunities to repurpose neurological drugs to disrupt these communication axes. Full article

Brain metastases remain a major problem for cancer patients, impacting their treatment and survival. The pathogenesis of brain metastases is largely unknown. Recent reports indicate that the adhesion molecule protocadherin γ C3 (PCDHGC3) is differentially expressed in various cancer cells and endothelial cells of the blood–brain barrier (BBB), suggesting its involvement in the development of brain metastases. Therefore, we generated a PCDHGC3 knockout (KO) in the triple-negative breast cancer cell line HCC1806 and the malignant melanoma cell line A2058. Control and KO cells were compared using cell proliferation, adhesion and invasion assays, gene expression analyses and matrix metalloproteinase (MMP) activity assays. While the PCDHGC3 KO mutation led to increased proliferation in HCC1806 cells, with no difference observed in A2058, it significantly increased adhesion to in vitro BBB models as well as invasion in both HCC1806 and A2058 KO cell lines. Although changes in mRNA expression of genes involved in metastasis, angiogenesis and cell adhesion were found in PCDHGC3 KO breast cancer and melanoma cells, the number of genes with significantly increased mRNA expression was higher in A2058 KO cells than in HCC1806 KO cells. While the mRNA expression of MMP1 and 2 was increased in A2058 KO cells, no significant changes were found in HCC1806 KO cells. However, increased MMP activity in the cell culture medium was detected in HCC1806 KO cells, while A2058 KO cells showed lower MMP-activity compared to control. These findings provide insights into the role of PCDHGC3 in cancer cell extravasation during metastatic process and identify potential therapeutic targets for further investigation. Full article

Background: Many studies evaluating central nervous system (CNS) metastases in breast cancer (BC) combine germline BRCA1 and BRCA2 pathogenic variant carriers, limiting gene-specific interpretation. We evaluated gene-specific overall survival (OS) after CNS metastasis and time to CNS involvement. Methods: We retrospectively identified BC patients with confirmed CNS metastases (1995–2022) from the Medical University of Vienna and the kConFab consortium. Germline status was classified as gBRCA1 PV, gBRCA2 PV, or non-carrier. Primary endpoint was OS from CNS metastasis diagnosis; secondary endpoint was CNS metastasis-free interval from primary BC diagnosis. Kaplan–Meier/log-rank tests were used for group comparisons. Multivariable Cox models assessed OS in complete cases, stratified by molecular subtype and adjusted for prognostic factors. Sensitivity analyses included subtype-adjusted and time-period models. Results: Among 115 patients (gBRCA1 n = 32, gBRCA2 n = 18, and non-carriers n = 65), median OS differed by germline status (p = 0.019): 20.0 months (95% CI 6.7–60.0) for gBRCA2 versus 7.1 months (95% CI 3.7–10.0) for gBRCA1 and 7.6 months (95% CI 3.4–12.0) for non-carriers. In subtype-stratified analyses, gBRCA1 showed similar mortality to non-carriers (HR 0.90, 95% CI 0.49–1.64, p = 0.730), while gBRCA2 showed a lower but non-significant hazard (HR 0.48, 95% CI 0.18–1.25, p = 0.131). Median CNS metastasis-free interval was longer for gBRCA2 (8.4 years) versus gBRCA1 (3.0 years) and non-carriers (3.1 years; p = 0.020). Sensitivity analyses were consistent. Conclusions: gBRCA2 carriers demonstrated longer unadjusted OS after CNS metastasis and a longer CNS metastasis-free interval compared with gBRCA1 carriers and non-carriers. However, these associations were attenuated and not statistically significant after adjustment, and should therefore be interpreted as hypothesis-generating. These findings supports further investigation of gene-specific CNS disease trajectories in larger cohorts. Full article

Background/Objectives: Brain metastasis (BM) represents a significant clinical challenge in advanced breast cancer, yet the molecular mechanisms driving breast cancer brain metastasis (BCBM) remain incompletely characterized. This study aims to identify key molecular pathways and hub genes specifically associated with BCBM through comprehensive bioinformatic analyses. Methods: Gene Set Enrichment Analysis (GSEA), differential gene expression analysis, and weighted gene co-expression network analysis (WGCNA) were performed using two independent GEO datasets (GSE191230 and GSE43837). Protein–protein interaction (PPI) networks were constructed to visualize functional interconnections among dysregulated genes. Survival analyses were conducted using the Kaplan–Meier Plotter database to evaluate the prognostic significance of identified hub genes. Results: GSEA revealed significant upregulation of metabolic pathways (mTORC1 signaling, glycolysis, oxidative phosphorylation) and downregulation of immune-related pathways in BCBM compared to primary tumors. Integrative analysis identified 34 consistently dysregulated genes across datasets, from which 12 hub genes were validated. Among these, RRM2, CDCA8, CCNB1, LMNB2, FANCI, NCAPH, YWHAZ, and ESPL1 demonstrated brain-specific over-expression compared to other metastatic sites. Functional enrichment analysis highlighted cell cycle dysregulation as a critical mechanism in BCBM, and all hub genes showed significant association with poor prognosis in breast cancer patients. Conclusions: This study identifies a unique molecular profile of BCBM characterized by cell cycle dysregulation, metabolic reprogramming, and immune microenvironment alterations. The brain-specific expression patterns of these hub genes represent potential biomarkers for BCBM risk assessment and novel therapeutic targets, providing a basis for precision medicine development. Full article

Triple-negative breast cancer (TNBC) is associated with a high risk of brain metastases (BMs). Although systemic therapies have improved extracranial disease control, the central nervous system (CNS) remains less accessible to numerous agents. As a result, this limited drug penetration makes brain metastases (BMs) remain common in TNBC, which are a leading cause of serious symptoms. This review summarizes recent key advances in triple-negative breast cancer brain metastases (TNBC-BMs), including epidemiology, prognostic stratification, biological mechanisms of CNS tropism and treatment resistance, and evolving management strategies. We discuss potential mechanisms of brain colonization, including the FOXC1-CXCR4 axis, ST6GALNAC5-related interactions with the blood–brain barrier (BBB), and the bidirectional crosstalk between metastatic cells and the brain microenvironment, particularly astrocytes and microglia. Furthermore, we evaluate the evolving clinical management, emphasizing the transition from whole-brain radiotherapy (WBRT) toward more selective local approaches such as stereotactic radiotherapy (SRS) and hippocampal sparing techniques. Concurrently, we examine the integration of CNS active systemic therapy across specific molecular subsets. This review systematically distinguishes standard-of-care interventions from investigational strategies, ultimately underscoring critical evidence gaps within the TNBC-BM landscape. Full article

Mechanisms underlying breast cancer brain metastasis (BCBM) are still not well understood. Here, we identified that BCBM patient serum contained extracellular vesicles (EVs) with high levels of microRNAs (miRNAs)-107 and -425. Levels of miR-107 and miR-425 were elevated in brain metastases, and the elevation was associated with poor patient prognoses. Ectopic expression of miR-107 and miR-425 promoted mammospheres; however, the inhibition of miR-425, but not miR-107, suppressed breast cancer mammosphere formation. We further observed that EVs from miR-425-overexpressing breast cancer cells strongly activated astrocytes whereas their inhibitors abrogated the effect. Conditioned media from miR-425-activated astrocytes promoted mammospheres. To elucidate how miR-425 activates astrocytes, we found that, within astrocytes, miR-425 suppressed the expression of transcription factor ZNF24, which downregulated CCL8 cytokine expression/secretion, leading to the subsequent activation of astrocytes. Using a mouse study, we further determined the role of miR-425 in brain metastasis formation and observed that miR-425-overexpressing breast cancer cells exhibited significantly more aggressive growth in mouse brains compared to control cells. Immunohistochemistry and immunofluorescence analyses of mouse brain metastases revealed that miR-425-overexpressing tumors exhibited significantly increased activation, intratumoral accumulation, and proliferation of astrocytes, and a decrease in ZNF24 expression compared to control tumors. Together, our findings demonstrate, for the first time, that breast cancer EV-derived miR-425 promotes BCBM via activating astrocytes in the brain microenvironment through the novel EV-miR-425-ZNF24-CCL8 signaling axis. Full article

Background: Breast cancer brain metastases (BCBM) lack effective treatments, contributing to breast cancer-related morbidity and mortality. Integrating translational animal models and advanced non-invasive imaging can accelerate the development of urgently needed therapies. Method: In this study, we developed an intracarotid method mimicking BCBM and compared it to the stereotactic model in terms of animal welfare, tumour establishment, and blood–brain barrier (BBB) permeability. BCBM was established through intracarotid or stereotactic inoculation of BT474 and MDA-MB-231.Luc2 cells in NMRI nude mice. We utilised magnetic resonance imaging (MRI) and bioluminescence imaging (BLI) to monitor tumour growth and BBB permeability, supported by fluorescent immunohistochemistry for validation. Finally, light sheet microscopy (LSM) was employed to visualise tumour establishment in intact brains. Results: Both inoculation methods achieved a survival rate > 70%, with animals recovering within a week post-surgery. MRI and BLI effectively visualised tumour growth with stereotactic implantation, resulting in single tumours, while intracarotid inoculation led to micro-seeding of up to seven tumours in one brain. Tumour growth was rapid and homogenous in the stereotactic model, whereas the intracarotid model exhibited slower, heterogenous growth. Notably, BBB permeability was significantly higher in small tumours in the stereotactic model when compared to the intracarotid model (p = 0.003). Ex vivo analyses validated these findings with the identification of multiple metastasis in the intracarotid model and single tumours in the stereotactic model. Conclusions: We developed an animal model that closely mimics BCBM, highlighting extravasation and micro-seeding while maintaining animal welfare. Our established imaging protocols enable longitudinal evaluations of BBB permeability and treatment response, creating a translational platform for testing novel anti-cancer therapies. Full article

Background/Objectives: Human epidermal growth factor receptor 2 (HER2)-positive breast cancer is linked to poorer overall survival and a higher risk of brain metastases compared to HER2-negative breast cancer. Current preclinical studies lack robust HER2+ metastatic syngeneic mouse models for investigating targeted and immunomodulatory therapies. This study aims to develop effective HER2+ mouse models to investigate response dynamics to HER2-targeted therapy and immunotherapy. Methods: The human HER2 gene (WT or mutant p.A775_G776insYVMA, GFP-tagged at the C-terminus) was introduced into triple-negative breast cancer (TNBC) mouse mammary carcinoma cells with known metastatic potential (4T1 and EO771) via lentiviral transduction. HER2 expression and phosphorylation were analyzed using Western blotting and immunohistochemistry. Tumors were treated with HER2-targeted therapy (trastuzumab and tucatinib), immune checkpoint blockade (anti-PD-1 and anti-CTLA-4), and anti-HER2 antibody–drug conjugate (ADC) to evaluate treatment efficacy. Metastatic potential was assessed with brain fluorescence imaging. Statistical analysis included ANOVA and Kaplan–Meier tests. Results: Newly established lines demonstrated expression of HER2+, with HER2^YVMA lines showing higher phosphorylation than HER2^WT lines. Cells were tumorigenic, demonstrating in vivo tumor take rates at 100% for 4T1-HER2 and 15–30% for EO771-HER2. HER2 overexpression led to a 30% increase in spontaneous brain metastasis in the 4T1-HER2 models. Trastuzumab alone did not reduce primary tumor size but significantly reduced brain GFP signal by 17% ± 8% and 26% ± 7% in the 4T1-HER2^WT and 4T1-HER2^YVMA models, respectively. Combinational therapies with anti-HER2 therapy and immune checkpoint blockade effectively suppressed primary tumor growth and prolonged survival in EO771-HER2^YVMA model. T-Dxd, but not T-DM1, demonstrated partial treatment response in the EO771-HER2^WT model. Conclusions: HER2+ syngeneic tumor models were developed that spontaneously metastasize to the brain and demonstrate variable responses to immunotherapies and ADCs. These models are valuable for advancing molecular imaging modalities for HER2+ brain metastasis, studying blood–brain barrier penetration of HER2-targeted drugs, and exploring the combination of therapies, including immunotherapy. Full article