Co-targeting cystathionine gamma-lyase and mTOR: a promising therapeutic strategy in clear cell ovarian cancer.

). We measured viability, proliferation, colony formation, apoptosis, and protein signaling. Drug interaction was quantified with a synergy model.Everolimus reduced viability and increased apoptosis across CCOC cell lines, but activity was modest as a single agent. Adding CTH inhibition produced synergistic growth suppression at low doses, with the effect being stronger under hypoxia. The combination reduced colony formation over 14 days and decreased spheroid size while increasing caspase-3/7 activity. Dual treatment decreased HIF1α protein expression more than either monotherapy while maintaining strong inhibition of mTOR/S6 kinase signaling; total mTOR and S6 kinase were unchanged. In CTH-deficient models, the synergy was maintained; however, pharmacological inhibition of CTH with AVG did not produce additional effects, indicating dependence on CTH activity and supporting an on-target mechanism. Similar antiproliferative effects with combined treatment were observed in a CTH-expressing Ewing sarcoma (EwS) model.Together, these findings support biomarker-guided strategies and rational combination therapies that achieve dual targeting of mTOR and CTH, thereby disrupting protein translation and hypoxia adaptation in CCOC and other CTH-expressing cancers.