Inhibiting UNC13B Suppresses Cell Proliferation by Upregulating the Apoptotic Pathway in Multiple Myeloma

<b>Background/Objectives:</b> Multiple myeloma (MM) is the second most common hematological malignancy and remains incurable because of its complex and heterogeneous pathogenesis. <i>UNC13B</i> (unc-13 homolog B) encodes Munc13-2, a presynaptic protein that is involved in vesicle exocytosis. While its role has been explored in neurological diseases, its function in cancer biology remains largely uncharacterized. This study aimed to elucidate the role of UNC13B in regulating MM cell proliferation and apoptosis. <b>Methods:</b><i>UNC13B</i> mRNA expression was assessed across human MM cell lines. ARD cells, which exhibited the highest <i>UNC13B</i> expression, were transduced with a UNC13B-specific shRNA via a lentiviral vector. Cell proliferation, apoptosis, and expression of associated proteins were evaluated by means of the Cell Counting Kit-8 (CCK-8) assay, flow cytometry, and Western blot analysis. <b>Results:</b><i>UNC13B</i> was significantly upregulated in MM cell lines. The knockdown of <i>UNC13B</i> in ARD cells markedly inhibited cell proliferation and induced apoptosis. These changes were accompanied by the downregulation of proliferation-related proteins and upregulation of pro-apoptotic markers. Western blot analysis suggests that UNC13B may exert its effects by modulating key regulatory proteins, including PINK1, CDK2, AKR7A3, and Bim. <b>Conclusions:</b> Our findings suggest that UNC13B supports MM cell survival and proliferation, potentially through the regulation of oncogenic and apoptotic signaling pathways. UNC13B may represent a novel therapeutic target in multiple myeloma.