PIK3CA mutation in endometriotic epithelial cells promotes viperin-dependent inflammatory response to insulin

Endometrial epithelia are known to harbor cancer driver mutations in the absence of any pathologies, including mutations in PIK3CA. Insulin plays an important role in regulating uterine metabolism during pregnancy, and hyperinsulinemia is associated with conditions impacting fertility. Hyperinsulinemia also promotes cancer, but the direct action of insulin on mutated endometrial epithelial cells is unknown. Here, we treated 12Z endometriotic epithelial cells carrying the PIK3CA^H1047R oncogene with insulin and examined transcriptomes by RNA-seq. While cells naively responded to insulin, the magnitude of differential gene expression (DGE) was nine times greater in PIK3CA^H1047R cells, representing a synergistic effect between insulin signaling and PIK3CA^H1047R expression. Interferon signaling and the unfolded protein response (UPR) were enriched pathways among affected genes. Insulin treatment in wild-type cells activated normal endoplasmic reticulum stress (ERS) response programs, while PIK3CA^H1047R cells activated programs necessary to avoid ERS-induced apoptosis. PIK3CA^H1047R expression alone resulted in overexpression (OE) of Viperin (RSAD2), which is involved in viral response and upregulated in the endometrium during early pregnancy. The transcriptional changes induced by insulin in PIK3CA^H1047R cells were rescued by knockdown of Viperin, while Viperin OE alone was insufficient to induce a DGE response to insulin, suggesting that Viperin is necessary but not sufficient for the synergistic effect of PIK3CA^H1047R and insulin treatment. We identified interferon signaling, viral response, and protein targeting pathways that are induced by insulin but dependent on Viperin in PIK3CA^H1047R mutant cells. These results suggest that response to insulin signaling is altered in mutated endometriotic epithelial cells.