Search Results (98)

(1) Background: KMT2A (alias MLL) is located at chromosome 11q23 and encodes histone methyltransferase 2A which activates target genes via chromatin methylation of histone H3 lysine K4. Mutations of KMT2A, including partial tandem duplication (PTD) and fusion with partner genes, are present in both lymphoid and myeloid acute leukemia. More than 100 various KMT2A fusion genes have been described, with only a minority represented by cell line models. (2) Methods: Cytogenetic and genomic copy number analyses, PCR, Western blot and RNA-sequencing were performed to characterize aberrations in acute myeloid leukemia (AML) cell line KOPM-88. Bioinformatic analysis of public AML patient data revealed differentially expressed genes. Functional analyses were performed by siRNA-mediated knockdown and live-cell imaging. (3) Results: The AML cell line KOPM-88 is derived from a boy at relapse and has been reported to carry t(X;11)(q24;q23), albeit with uncharacterized breakpoints. In KOPM-88 we identified fusion gene KMT2A::SEPTIN6 generated by this translocation, but excluded KMT2A-PTD. KMT2A::SEPTIN6 activated bone morphogenetic protein (BMP)-signalling and inhibited expression of HOXA7 and HOXA9. BMP signalling in turn activated cell proliferation and inhibited CDKN2B expression. (4) Conclusions: KOPM-88 contains fusion gene KMT2A::SEPTIN6, representing the only cell line model for this rare type of KMT2A rearrangement. KOPM-88 may serve to advance novel therapeutic treatments for KMT2A::SEPTIN6-positive AML. Full article

Background/Objectives: Adoptive transfer of allogeneic natural killer (NK) cells represents a promising off-the-shelf immunotherapy for cancer, offering advantages in safety and availability over autologous T cell therapies. However, generating therapeutically sufficient NK cell numbers remains challenging due to their low frequency in blood sources. Engineered feeder cell co-cultures have enabled substantial expansions of NK cells to clinically relevant doses. Methods: We evaluated the plasma cell leukemia-derived ARH-77 cell line as a feeder for ex vivo NK cell expansion from healthy donor peripheral blood mononuclear cells (PBMCs). Unmodified ARH-77 was compared to K562, followed by engineering both lines to co-express B7-H6 (NKp30 ligand), CD137L (4-1BBL), IL-15, and IL-15Rα via sequential lentiviral transduction. PBMCs were co-cultured with irradiated feeders in cytokine-supplemented (IL-2, IL-21, and later IL-15) RPMI-1640 or DMEM/F-12 medium for up to 28 days. Expansion (fold change in CD3⁻CD56⁺ cells), purity, surface receptor expression, and cytotoxicity (against K562 targets) were quantified. Results: Unmodified ARH-77 supported significantly greater NK cell expansion than K562 (model-estimated 681-fold vs. 155-fold at week 4 in RPMI; p = 0.0018), with higher purity but comparable cytotoxicity and receptor profiles. Engineered ARH-77 cells achieved robust expansion in RPMI, comparable to that of engineered K562 cells. In optimized DMEM/F-12 medium, engineered ARH-77 drove superior expansion (up to model-estimated 101,241-fold; 95% CI 46,771–219,146 at week 4), significantly outperforming engineered K562 (4.4-fold greater; 95% CI 1.01 to 18.54; p = 0.0479) while maintaining high purity and equivalent cytotoxicity. Substantial inter-donor variability influenced expansion magnitude, though relative feeder performance remained consistent across donors. Conclusions: Genetically modified ARH-77 feeder cells provide a potent platform for large-scale ex vivo expansion of functional NK cells. Full article

Glycosylation is essential for hematopoietic cell homeostasis and malignant transformation. Dysregulated expression of glycosylation genes in leukemia cells accelerates disease progression and fosters drug resistance. Therefore, targeting these genes offers a promising avenue for anti-leukemic therapy. In this study, we explore the roles of N-glycans in acute promyelocytic leukemia (APL) differentiation using the ATRA-induced wild-type NB4 (WT/ATRA) or HL-60 cell model. We found that expression of N-acetylglucosaminyltransferase IVa (GnT-IVa, encoded by the MGAT4A gene) and its product (β1,4-GlcNAc-branched N-glycan) increased significantly during differentiation, as evaluated by lectin blot, real-time PCR, and flow cytometry. Interestingly, analysis of the Gene Expression Omnibus (GEO) public data showed that MGAT4A expression is significantly lower in APL patients, and higher MGAT4A expression was associated with favorable survival in AML cohorts. To address the role of GnT-IVa in differentiation, we established MGAT4A- and MGAT4B-knockout (KO) NB4 cell lines using CRISPR/Cas9. Compared to WT/ATRA cells, MGAT4A KO, but not MGAT4B KO, markedly suppressed ATRA-induced differentiation, as evidenced by reduced expression of CD11b and CD11c. We found that CD11b is a major glycoprotein carrying β1,4-GlcNAc-branched N-glycans. This modification enhanced CD11b stability, as CD11b expression declined more rapidly in MGAT4A KO cells in the presence of cycloheximide. In addition, MGAT4A KO suppressed ERK/MAPK signaling, which contributed to differentiation. Our study highlights the critical role of GnT-IVa in regulating APL differentiation, which may provide a basis for developing new differentiation therapies for APL. Full article

Background/Objectives: Acute myeloid leukemia (AML) comprises a heterogeneous group of diseases, with some subtypes displaying promyelocytic features and altered differentiation programs. Aberrant cytokine receptor signaling has been implicated in leukemogenesis, and IL-5Rα has recently emerged as a potential marker in selected AML subsets, including promyelocytic variants. Benralizumab is a monoclonal antibody directed against the alpha chain of the interleukin-5 receptor (CD125), which blocks IL-5Rα–mediated signaling. This proof-of-concept study aimed to explore the effects of the anti-IL-5Rα monoclonal antibody Benralizumab in an in vitro AML cell model with promyelocytic characteristics. Methods: Public transcriptomic datasets were analyzed to evaluate IL-5Rα expression in AML subtypes. HL-60 cells, an AML cell line expressing IL-5Rα, were treated with Benralizumab and analyzed for cell cycle distribution and modulation of key signaling and apoptotic pathways by flow cytometry and Western blotting. Results: IL-5Rα was highly expressed in AML, particularly in M2 and M3 subtypes. Benralizumab treatment reduced STAT3 expression, activated ERK and NF-κB signaling, induced p21 and p27 expression, altered cell cycle distribution, and induced caspase-8 cleavage, suggesting activation of extrinsic apoptotic signaling. Conclusions: These findings provide preliminary proof-of-concept evidence that IL-5Rα targeting by Benralizumab may directly affect cell survival and cell cycle regulation in AML cells with promyelocytic characteristics. When interpreted together with the in silico analyses performed on AML patient datasets, these results support the rationale for future validation in APL-oriented models carrying the PML::RARα fusion, the disease-defining oncogenic driver generated by the t(15;17) translocation that blocks myeloid differentiation. However, the in silico and in vitro datasets were not formally integrated at the patient level, and these functional results should be considered exploratory. Full article

Background: B-cell malignancies have been effectively treated using chimeric antigen receptor-T (CAR-T) treatment employing traditional αβT cells. However, because of several obstacles, application in acute myeloid leukemia (AML) is still restricted. A safer “off-the-shelf” alternative can be supplied by CAR-γδT cells, which have major histocompatibility complex (MHC)-independent tumor identification capabilities and a decreased risk of graft versus host disease (GvHD). This study aimed to develop FLT3-targeted CAR-γδT cells that co-express cytokines (IL-2 or IL-7) to increase their anti-AML persistence and therapeutic efficacy. Methods: FLT3-CAR-γδT cells, FLT3-IL2-CAR-γδT cells, and FLT3-IL7-CAR-γδT cells were constructed. Their antitumor potency was comprehensively assessed through cytotoxicity assays, cytokine release, and persistence evaluation in vitro (using AML cell lines and primary AML cells) and in vivo (via mouse model). Results: Superior cytotoxicity against AML cell lines (OCI-AML3, MOLM-13, THP-1, and MV4-11) was demonstrated by FLT3-IL2-CAR-γδT cells, which also released higher levels of granzyme B, interferon-γ (IFN-γ), and tumor necrosis factor-α (TNF-α). FLT3-IL2-CAR-γδT cells exhibited cytotoxicity in some primary AML cells in vitro. During the antigen-repeated stimulation assay, FLT3-IL2-CAR-γδT cells preserved the stem cell-like memory T (T_SCM) cell subsets, sustained cytokine release, and maintained excellent viability. FLT3-IL2-CAR-γδT cells considerably slowed the development of AML in vivo and extended the existence (>68 days) of mice. Conclusions: FLT3-IL2-CAR-γδT cells exhibit potent and durable anti-AML activity, providing a novel strategy for clinical AML immunotherapy. Full article

SLAMF7, also known as CD319, a SLAM (signaling lymphocytic activation molecule) family receptor, is relatively weakly expressed on chronic lymphocytic leukemia (CLL) B cells. This study evaluated the ability of elotuzumab (E), an anti-SLAMF7/CD319 antibody, to induce antibody-dependent cellular cytotoxicity (ADCC) against CLL cell lines (MEC-1, MEC-2, CI, HG-3, PGA-1, WA-OSEL). ADCC was assessed by flow cytometry using E (100 μg/mL), rituximab (R, 100 μg/mL), and their combination (E + R). CLL lines served as targets (T), while peripheral blood mononuclear cells (PBMCs) or NK cells from healthy donors served as effectors (E) at an 8:1 E:T ratio for 4 h. With PBMCs, E-induced ADCC ranged from 1.3 ± 1.2% (PGA-1) to 14.6 ± 8.1% (MEC-1); R-induced ADCC ranged from 9.2 ± 4.6% (PGA-1) to 16.6 ± 9.4% (WA-OSEL). With NK cells, E-induced ADCC ranged from 1.8 ± 3.7% (PGA-1) to 27.3 ± 4.7% (MEC-1); R-induced ADCC ranged from 5.1 ± 4.3% (PGA-1) to 27.5 ± 13.6% (CI). E outperformed R in MEC-1, while R was superior elsewhere. Cell lines with higher SLAMF7/CD319 expression displayed increased sensitivity to E. Cell lines with del17p showed higher SLAMF7/CD319 expression. The combination of E + R showed no significant synergy over monotherapies. In conclusion, elotuzumab induced significant ADCC in CLL cells, warranting further therapeutic evaluation. Full article

Histone acetylation and deacetylation are key regulators of gene expression and are frequently dysregulated in cancer, contributing to tumorigenesis and drug resistance. Overexpression of histone deacetylases (HDACs) in many cancer types leads to silencing of tumor suppressor genes and uncontrolled proliferation. Tumors often rely on epigenetic mechanisms to escape therapy and develop resistance. This study aimed to identify novel compounds that selectively target cancer cells while minimizing toxicity to non-cancerous cell lines. A series of novel HDAC inhibitors was evaluated using the Differential Nuclear Staining (DNS) assay, flow cytometry, and HDAC inhibition assays. These assays assessed cytotoxicity, selectivity, and mechanisms of cell death. Among seven compounds tested, VS-186B exhibited the highest cytotoxicity and Selective Cytotoxicity Index (SCI), particularly against the human Jurkat T-cell leukemia cell line. Flow cytometry experiments (Annexin V-FITC, ROS, JC-1, and Caspase-3/7 assays) revealed that VS-186B induced apoptosis. VS-186B was more cytotoxic than Curcumin and Vorinostat across most of the cell lines tested and was more specific to hematological cells. Connectivity Map (CMap) analysis showed strong similarity to genes affected by known HDAC inhibitors. Subsequently, HDAC enzymatic assays confirmed that VS-186B inhibits Class I and II HDACs in a dose-dependent manner. VS-186B exhibits promising anticancer potential as a selective HDAC inhibitor since it induces apoptosis in cancer cells without significant cytotoxicity to non-cancerous lines with a similar gene expression profile to known HDAC inhibitors. These findings support further development of VS-186B as an epigenetic treatment for leukemia/lymphoma. Full article

The hybrid Sechium edule H387 07, commonly known as chayote, has shown potential as an antiproliferative, cytotoxic, and pro-apoptotic agent in the murine leukemia cell lines P388 (macrophagic) and J774 (monocytic) and in the myelomonocytic leukemia cell line WEHI-3. However, despite these reported bioactivities, its pharmacokinetic profile remains largely unexplored. Understanding the absorption, distribution, and elimination of this hybrid is critical for addressing unmet therapeutic needs and for advancing the development of natural product-based therapies. These effects are attributed to the presence of phenols, flavonoids, and cucurbitacins in its organic extracts. In this study, the pharmacokinetic parameters of secondary metabolites from methanolic extracts of Sechium H387 07 were evaluated after oral administration in mice, while its segregant H387 M16 was subjected to complementary phytochemical characterization. Methanolic extracts of Sechium edule H387 07 were orally administered to mice at doses of 8, 125, and 250 mg/kg, and plasma, liver, and urine samples were collected at 1, 6, 24, and 48 h post-treatment. High-performance liquid chromatography (HPLC) identified polyphenols and cucurbitacins, notably cucurbitacin B (CuB) and cucurbitacin IIA (CuIIA), in the biological samples, and pharmacokinetic variables such as the maximum plasma concentration (C_max), time to reach maximum concentration (T_max), half-life (T_1/2), and volume of distribution (V_d) were determined. For instance, CuB exhibited a C_max of 37.56 µg/mL at 1 h post-dose after oral administration of 125 mg/kg, confirming its rapid absorption and systemic distribution. Notably, the presence of CuIIA in plasma was documented for the first time, along with the pharmacokinetic profiles of apigenin, phloretin, CuB, CuE, and CuI. In parallel, the segregant H387 M16 was characterized via colorimetric assays, thin-layer chromatography (TLC), HPLC, and antioxidant activity tests, which revealed high levels of flavonoids, phenols, and cucurbitacins, with an antioxidant activity of approximately 75% at the highest tested dose (1 mg/mL), supporting its suitability for future bioassays. Overall, these findings not only provide novel pharmacokinetic data for key metabolites of the H387 07 hybrid but also establish the phytochemical and antioxidant profile of its segregant H387 M16. This dual characterization strengthens the evidence of the therapeutic potential of Sechium genotypes and provides a valuable foundation for future studies aiming to develop standardized protocols and explore translational applications in drug development and natural product-based therapies. Full article

Acute lymphoblastic leukemia (ALL) remains a formidable therapeutic challenge, particularly within high-risk cohorts. Advances in next-generation sequencing have elucidated critical mutations that significantly influence prognosis and therapeutic decision-making. Tyrosine kinase inhibitors (TKIs) have significantly improved treatment outcomes in Philadelphia chromosome-positive (Ph+) ALL. Meanwhile, emerging therapies such as monoclonal antibodies and chimeric antigen receptor (CAR) T-cell therapies show promise for B-cell ALL, although they are associated with considerable toxicities. These developments underscore the persistent need for alternative therapeutic strategies that can benefit a wider range of patients. In this study, human ALL cell lines—characterized by either wild-type or mutant tumor protein p53 (TP53) status—were treated with RG7388 (an MDM2 (mouse double minute 2 homolog) inhibitor) and BBI608 (a STAT3 (signal transducer and activator of transcription 3) inhibitor), both as single agents and in combination. Cell viability was quantified using XTT assays, while apoptosis was assessed via flow cytometry. Additionally, immunoblotting and qRT-PCR were employed to evaluate changes in protein and gene expression, respectively. RG7388 demonstrated potent growth inhibition in the majority of ALL cell lines, with p53-mutant cell lines exhibiting resistance. BBI608 reduced cell viability across all tested cell lines, though with variable sensitivity. Notably, the combination of RG7388 and BBI608 elicited synergistic anti-proliferative effects in p53 wild-type and partially functional p53-mutant cells, enhancing apoptosis and stabilizing p53 protein levels. In contrast, MOLT-4 cells, which harbor concurrent TP53 and STAT3 mutations, did not benefit from the combination treatment, indicating an inherent resistance phenotype within this subset. Collectively, these findings highlight the therapeutic potential of combined MDM2 and STAT3 inhibition in ALL, particularly in p53 wild-type and partially functional p53-mutant contexts. This combinatorial approach augments apoptosis and tumor growth suppression, offering a promising avenue for expanding treatment options for a broader patient population. Further investigation is warranted to validate these preclinical findings and to explore translational implications in genetically diverse ALL subsets. Full article

Chimeric antigen receptor (CAR) T-cell therapy directed to CD19 and B-cell maturation antigen has revolutionized treatment of B-cell leukemia and lymphoma, and multiple myeloma. However, identifying suitable targets for acute myeloid leukemia (AML) remains challenging due to concurrent expression of potential target antigens on normal hematopoietic stem cells or tissues. As the stress-induced B7H6 molecule is rarely found on normal tissues but expressed on many cancers including AML and melanoma, the NKp30-ligand B7H6 emerges as a promising target for NKp30-based CAR T therapy for these tumors. In this study, we report a comprehensive B7H6 expression analysis on primary AML and melanoma as well as on different tumor cell-lines examined by RT-qPCR and flow cytometry, and efficient anti-tumor reactivity of NKp30-CAR T cells to AML and melanoma. To overcome limitations of autologous CAR T-cell fitness-dependent efficacy and patient-tailored production, we generated CRISPR/Cas9-mediated TCR-knockout (TCR^KO) NKp30-CAR T cells as an off-the-shelf approach for CAR T therapy. Functional studies comparing NKp30-CD28 CAR or NKp30-CD137 CAR TCR⁺ and TCR^KO T lymphocytes revealed superior anti-tumoral immunity of NKp30-CD28 CAR TCR^KO T cells to AML and melanoma cell lines in vitro, and effective control of tumor burden in an NSG melanoma-xenograft mouse model. In conclusion, these findings highlight the therapeutic potential of NKp30 CAR TCR^KO T cells for adoptive T-cell therapy to B7H6-expressing cancers, including melanoma and AML. Full article

Background/Objectives: This study compared overall survival (OS) associated with common real-world treatment sequences in patients with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) in the United States. Methods: Utilizing the nationwide Flatiron Health electronic health record-derived de-identified database, adult CLL/SLL patients who initiated systemic therapy (JAN2016-NOV2023) and received at least two lines of therapy (LoTs) were analyzed. Treatment regimens were categorized based on drug class, and most frequent (n ≥ 50) sequences (first LoT followed by [→] second LoT) were compared. OS from initiation of the first LoT was compared using multivariable Cox proportional hazard models, and adjusted hazard ratios with 95% CIs were reported. Results: Among 2354 eligible patients, n = 1711 (73%) received the 16 most frequent treatment sequences. Sequencing chemoimmunotherapy (CIT) → CIT (HR: 2.29 [1.23–4.28]), anti-CD20 monoclonal antibody (anti-CD20mab) monotherapy → CIT (1.95 [1.03–3.69]), and covalent Bruton tyrosine kinase inhibitor (cBTKi) monotherapy → anti-CD20mab monotherapy (2.00 [1.07–3.74]) were associated with worse OS compared to patients treated with cBTKi monotherapy → B-cell lymphoma 2 inhibitors (BCL2i) + anti-CD20mab (reference). Conclusions: OS associated with other sequences were not significantly different from the reference sequence in adjusted analyses, suggesting a lack of evidence for the optimal standard of care for sequencing the first two LoTs in real-world settings. Future research should reassess sequencing outcomes as novel treatments become adopted into clinical practice. Full article

Current treatments against leukemia present several limitations, prompting the search for new therapeutic agents, particularly those derived from natural products. In this context, structural modifications were performed on the triterpene 3α,24-dihydroxylup-20(29)-en-28-oic acid (T1), isolated from Phoradendron wattii. Among the five derivatives obtained, 3α,24-dihydroxy-30-oxolup-20(29)-en-28-oic acid (T1c) exhibited the highest activity, with an IC₅₀ value of 12.90 ± 0.1 µM against THP-1 cells. T1c significantly reduced cell viability in both acute lymphoblastic leukemia (CCRF-CEM, REH, JURKAT, and MOLT-4) and acute myeloid leukemia (THP-1) cell lines, inducing apoptosis after 48 h of treatment, while showing minimal cytotoxicity toward normal mononuclear cells (MNCs). In silico molecular docking studies were conducted against three key protein targets: BCL-2 (B-cell lymphoma 2), EGFR (epidermal growth factor receptor, tyrosine kinase domain), and FLT3 (FMS-like tyrosine kinase 3). The lowest binding energies (kcal/mol) observed were as follows: T1–BCL-2: −10.12, EGFR: −12.75, FLT3: −14.05; T1c–BCL-2: −10.23, EGFR: −14.50, FLT3: −14.07; T2–BCL-2: −11.59, EGFR: −15.00, FLT3: −14.03. These findings highlight T1c as a promising candidate in the search for anti-leukemic drugs which deserves further study. Full article

Background and Objectives: A thorough comprehension of the essential molecules and related processes underlying the carcinogenesis, proliferation, and recurrence of acute myeloid leukemia (AML) is crucial. This study aimed to investigate the expression levels, diagnostic and prognostic significance and biological roles of Bcl-2-associated athanogene 4 (BAG4) in AML carcinogenesis. Materials and Methods: Gene expression profiles were analyzed using publicly available datasets, particularly GSE9476 and TCGA, using tools such as GEO2R, GEPIA2, UALCAN and TIMER2.0. The immune infiltration correlation was examined using the GSCA platform, while the function of BAG4 at the single-cell level was analyzed via CancerSEA. Protein–protein and gene–gene interaction networks were constructed using STRING and GeneMANIA, and enrichment analyses were performed using GO, KEGG and DAVID. Expression validation was performed using RT-qPCR in HL-60 (AML) and HaCaT (normal) cells, and ROC curve analysis evaluated the diagnostic accuracy. Results: BAG4 was significantly overexpressed in AML tissues and cell lines compared with healthy controls. High BAG4 expression was associated with poor overall survival and strong diagnostic power (AUC = 0.944). BAG4 was positively associated with immune cell infiltration and negatively associated with CD4+/CD8+ T and NK cells. At the single-cell level, BAG4 was associated with proliferation, invasion, and DNA repair functions. Functional network analysis showed that BAG4 interacted with apoptosis and necroptosis-related genes such as BCL2, BAG3 and TNFRSF1A and was enriched in pathways such as NF-κB, TNF signaling and apoptosis. Conclusions: BAG4 is overexpressed in AML and is associated with adverse clinical outcomes and immune modulation. It may play an important role in leukemogenesis by affecting apoptotic resistance and immune evasion. BAG4 has potential as a diagnostic biomarker and treatment target in AML, but further in vivo and clinical validation is needed. Full article

Background/Objectives: The physiological activation of cytotoxic CD8^pos T cells (CTLs) relies on the engagement of the TCR/CD3 complex with cognate peptide-HLA class I (pHLA-I) on target cells, triggering cell lysis with appropriate cytokine release and minimized off-target toxicity. In contrast, current immunotherapies for CD19-expressing hematological malignancies, such as chimeric antigen receptor (CAR) T cells and bispecific T cell engagers (BiTEs), bypass TCR/pHLA interactions, resulting in CTL hyperactivation and excessive cytokine release, which frequently cause severe immune-related adverse events (irAEs). Thus, there is a pressing need for T cell-based therapies that preserve physiological activation while maintaining antitumor efficacy. Methods: To address this, we developed CD19-ReTARG^TPR, a novel fusion protein consisting of the immunodominant cytomegalovirus (CMV) pp65-derived peptide TPRVTGGAM (TPR) covalently presented by a soluble HLA-B*07:02/β2-microglobulin complex fused to a high-affinity CD19-targeting Fab antibody fragment. The treatment of CD19-expressing cancer cells with CD19-ReTARG^TPR makes them recognizable for pre-existing anti-CMV_pp65 CTLs via physiological TCR-pHLA engagement. Results: Our preclinical data demonstrate that CD19-ReTARG^TPR efficiently redirects anti-CMV CTLs to eliminate CD19-expressing cancer cells, including both established cell lines and primary chronic lymphocytic leukemia (CLL) cells. Unlike CD19-directed CAR T cells or the CD19/CD3 BiTE blinatumomab, CD19-ReTARG^TPR mediated robust cytotoxic activity without triggering supraphysiological cytokine release. Importantly, this approach retained efficacy even against cancer cells with low CD19 expression. Conclusions: In summary, we provide a robust proof-of-concept study and show that CD19-ReTARG^TPR offers a promising alternative strategy for T cell redirection, enabling the selective and effective killing of CD19-expressing malignancies while minimizing cytokine-driven toxicities through physiological CTL activation pathways. Full article

Human T cell leukemia virus type 1 (HTLV 1) is an oncogenic retrovirus responsible for the development of adult T cell leukemia (ATL). The minus strand of HTLV-1 provirus encodes an oncoprotein named HTLV-1 bZIP factor (HBZ), which plays a pivotal role in viral replication and T cell proliferation. Of particular interest is the spliced HBZ isoform (sHBZ), which is predominantly expressed in ATL cells and localizes within the nucleolus, conferring immortalizing properties to T cells. Our previous study has shown that sHBZ colocalizes and associates with Nucleophosmin/B23, a nucleolar phosphoprotein with multiple functions. In this study, through an optimized nucleolar isolation method, we first confirmed sHBZ’s nucleolar localization via Western blotting in transfected HEK293T cells, chronically HTLV-1-infected T cell lines, and freshly infected HeLa cells. We further demonstrated that the sHBZ/B23 association predominantly occurs in the nucleolus by co-immunoprecipitation of cell fractions. Our study highlights the nucleolar localization of sHBZ and its possibly essential interaction with this nucleolar-residing protein, leading to cell immortalization. Full article