Forgie, B.; Prakash, R.; Marno, D.; Abdalbari, F. H.; Zorychta, E.; Noman, A. S. M.; Goyeneche, A. A.; Gilbert, L.; Burnier, J. V.; Telleria, C. M.

PurposeCisplatin (CDDP) is the most active chemotherapy for ovarian cancer; primary or acquired resistance signals a poor prognosis. Nelfinavir (NFV), an HIV protease inhibitor, has demonstrated anti-tumor activity in multiple cancer models, but its interaction with CDDP in ovarian cancer has yet to be demonstrated. In this work, we addressed whether the combination of CDDP and NFV provides treatment advantage in platinum (Pt)-resistant ovarian cancer cells. MethodsDrug synergy between NFV and CDDP was assessed using cell vitality assays and Loewe additivity modelling. Apoptotic and pyroptotic signalling were evaluated by immunoblotting, mitochondrial membrane potential analysis, and lactate dehydrogenase (LDH) release, and caspase inhibition. Transcriptomic changes were assessed by bulk mRNA sequencing followed by differential gene expression analysis and gene set enrichment analysis. ResultsNFV synergized with CDDP to reduce the viability of Pt-resistant ovarian cancer cells, promoting a regulated lytic cell death phenotype involving apoptotic and pyroptotic features. Combination treatment induced caspase-8 and caspase-3 activation, and downstream gasdermin E (GSDME) processing. Inhibition of caspase-3 significantly attenuated cell death, and caspase-8 inhibition rescued viability and prevented Bid cleavage, caspase-3 activation, and GSDME cleavage. These effects occurred in the context of enhanced endoplasmic reticulum stress, increased DNA damage with reduced DNA repair, and impaired Akt-driven survival signalling. ConclusionsOur findings establish that NFV synergizes with CDDP in killing Pt-resistant ovarian cancer cells by promoting a caspase-8-dependent apoptotic-to-secondary pyroptotic response, supporting further investigation of NFV as a potential drug to be repurposed to increase the efficacy of Pt-based therapy.