Birinapant enhances cisplatin sensitivity in epithelial ovarian cancer through modulation of apoptotic and survival signaling pathways.

BACKGROUND: Resistance to platinum-based chemotherapy in epithelial ovarian cancer is frequently driven by dysregulation of apoptotic pathways and overexpression of inhibitor of apoptosis proteins (IAPs). Smac mimetics, such as Birinapant, target IAPs and modulate TNF-α-associated signaling; however, their therapeutic efficacy is highly context-dependent. METHODS: We investigated the effects of Birinapant in combination with Cisplatin in ovarian cancer cell lines with distinct sensitivity profiles (SKOV3 and MDAH-2774), along with normal human endometrial stromal cells (HESC) to assess selectivity. Cell viability was measured using the MTT assay, and drug interactions were evaluated using the Chou-Talalay method. Apoptosis was quantified by Annexin V/PI flow cytometry. Protein expression (cIAP1, NF-κB, Caspase-3/8) was analyzed by immunofluorescence, and gene expression (BIRC2, CASP3/8, RELA, TNF) was assessed by RT-qPCR. RESULTS: The Birinapant-Cisplatin combination significantly reduced cell viability in SKOV3 cells and demonstrated strong synergistic effects (CI = 0.057-0.237), accompanied by substantial dose reduction. In contrast, MDAH-2774 cells exhibited limited responsiveness and predominantly antagonistic interactions. Mechanistically, combination treatment in SKOV3 cells was associated with reduced cIAP1 expression, suppression of NF-κB signaling, and activation of Caspase-8 and Caspase-3. Notably, TNF Mrna expression was strongly increased (log₂FC ≈ + 5.6), supporting involvement of TNF-associated apoptotic signaling. CONCLUSION: Birinapant increased the sensitivity of SKOV3 ovarian cancer cells to cisplatin by enhancing TNF-α-associated apoptotic signaling, while this synergistic effect was not observed in MDAH-2774 cells, emphasizing the importance of cellular context in determining SMAC mimetic responses. Our findings suggest that TNF-α responsiveness, cIAP1 (BIRC2)-related signaling, and the ability of cancer cells to activate apoptotic pathways, particularly caspase-8, may serve as potential biomarkers for identifying tumors more likely to respond to Birinapant-based combination therapies. Further studies using additional ovarian cancer models and clinical samples are required to validate the predictive value of these biomarkers.