Over kanserinde GSDMC- ve GSDMD-aracılı piroptotik hücre ölümü ve bu hücre ölüm mekanizmasına östrojenin etkisi

Ovarian cancer is the leading cause of death among gynecological malignancies, and it is the seventh most common cancer among women. Pyroptosis is a form of regulated pro-inflammatory cell death mechanism mediated and executed by the membrane-targeting (via their NT domains), lipid-binding, pore-forming gasdermin (GSDM) family of proteins. In this thesis, we found that mRNA expression of GSDMD and GDMDC is up-regulated in serous ovarian cancer compared to healthy ovaries, and that expression of GSDME and PJVK is down-regulated in serous ovarian cancer. GSDMB and GSDMD expressions showed differences among various histological subtypes of epithelial ovarian cancer. Copy number gains (CNV gains) were highly frequent (around %50) in genes encoding GSDMC and GSDMD in ovarian cancer patients. High expression of GSDMD and GSDMC was associated with shorter progression-free survival (PFS) in TP53-mutated ovarian cancer patients. Furthermore, we observed higher GSDMD and lower GSDME protein levels in ovarian tumors compared to surrounding/adjacent non-malignant stromal cells in the tumor microenvironment. Expression of NINJ1, a protein which mediates plasma membrane rupture following pyroptosis, decreased from early stage to late stage in serous ovarian cancer. The percentage of NINJ1 copy number loss events was the highest in ovarian cancer among other cancers. High expression of NINJ1 was associated with favorable overall survival (OS) in patients with ovarian cancer. NINJ1 mRNA expression was lower in cisplatin-resistant cells compared to cisplatin-sensitive ovarian cancer cells in vitro. Moreover, we showed that estrogen treatment increases the expression of GSDMC and GSDMD at the transcript level in chemosensitive (A2780) but not in chemoresistant (A2780-AD) ovarian cancer cell lines in vitro. We found that upon GSDMC overexpression, the decrease in cell viability in nigericin (a pyroptosis inducer)-treated A2780-AD cells reduces to a less significant level compared to that in A2780-AD negative control cells. Besides, we reported that GSDMC or GSDMD overexpression increases cell viability in untreated (without nigericin treatment) A2780 cells. We found that when GSDMD gene is silenced in A2780 cells, the decrease in cell viability in response to nigericin is reduced to a less significant level compared to that in negative siRNA-transfected A2780 cells. When GSDMC gene was silenced in A2780-AD cells, the decrease in cell viability in response to nigericin was reduced to a non-significant level compared to that in negative siRNA-transfected A2780-AD cells. In A2780 cell line, we found that inhibition of certain caspases (caspase-1, caspase-4, caspase-6 or caspase-8) using specific caspase inhibitors results in the loss of nigericin-induced decreases in cell viability. In contrast, the inhibition of only caspase-1, but not of any other caspases studied, led to a loss of nigericin-induced decreases in cell viability in chemoresistant A2780-AD cell line. We showed that upon inhibition of caspase-1, -4 or -8, the levels of released IL-18 from A2780 cells treated with nigericin slightly decreases compared to A2780 cells treated only with nigericin but not with any of the specific caspase inhibitors.Combined, our work provides a better understanding of pyroptosis and its regulation, and of certain proteins that mediates this cell death mechanism in the context of ovarian cancer.