GSDME-mediated pyroptosis is essential for the chemotherapeutic effects achieved by combined treatment of temsirolimus and 5-fluorouracil in ovarian carcinoma cells

OBJECTIVES: The expression of GSDMD and GSDME in ovarian cancerous tissues, adjacent tissues, and cancer cell lines remain poorly characterized. The contribution of pyroptosis to the synergistic therapeutic effects of PI3K-AKT-mTOR inhibitors and cell cycle inhibitors in ovarian carcinoma is unknown. METHOD: GSDME and GSDMD expression were quantified in ovarian cancer tissues, adjacent tissues, and cancer cell lines. The cytotoxic effects of temsirolimus (an PI3K-AKT-mTOR inhibitor) and 5-fluorouracil (5-FU, a cell cycle inhibitor) were assessed. RESULTS: Both GSDMD and GSDME were detected in ovarian cancer tissues and adjacent tissues. However, the N-terminals of GSDME and GSDMD were only expressed in cancerous tissues, with the GSDME-N terminal being particularly prominent. Similarly, in ovarian cancer cell lines, only GSDME-N terminal was increased when treated by temsirolimus and 5-FU, together with significantly suppressed cell proliferation. Synergistic treatment with temsirolimus and 5-FU further reduced cancer cell viability and enhanced pyroptosis by upregulating GSDME-N terminal expression. RNA interference confirmed that GSDME-mediated pyroptosis is essential for the cytotoxic effects of monotherapy and combination chemotherapy. 5-FU fails to induce complete conversion of pyroptosis to ferroptosis when combined with temsirolimus, even at extremely high concentrations. The drug combination also promoted apoptosis and ferroptosis, which were significantly attenuated by N-acetyl-L-cysteine (NAC). CONCLUSION: GSDME is the principal executor of spontaneous pyroptosis in ovarian cancer tissues. In chemotherapy employing cell cycle-targeting agents or PI3K-AKT-mTOR pathway inhibitors (alone or in combination) is beneficial, and pyroptosis is an indispensable cell death mechanism. Reactive oxygen species act as a nodal regulator orchestrating pyroptosis, apoptosis, and ferroptosis.