PIK3CA mutation in endometrial epithelia promotes Viperin-dependent inflammatory response to insulin 1

Endometrial epithelia (EE) 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 EE is unknown. Here, we treated EE cells carrying the PIK3CAH1047R oncogene with insulin and examined differential transcriptomes by RNA-seq. While cells responded to insulin, the magnitude of differential gene expression (DGE) was 9 times greater in PIK3CAH1047R cells, representing a synergistic effect between insulin signaling and PIK3CAH1047R. Interferon signaling and the unfolded protein response (UPR) were enriched pathways among affected genes. Insulin treatment in normal cells activated normal endoplasmic reticulum stress (ERS) response programs, while PIK3CAH1047R cells activated programs necessary to avoid ERS-induced apoptosis. PIK3CAH1047R expression alone resulted in fewer differentially expressed genes, however, top among these was overexpression of Viperin (RSAD2), which is involved in viral response and upregulated in the endometrium during early pregnancy. The transcriptional changes induced by insulin in PIK3CAH1047R cells were rescued by knockdown of Viperin, while overexpression alone was insufficient to induce a DGE response to insulin, suggesting that Viperin is necessary but not sufficient for the synergistic effect of PIK3CAH1047R and insulin treatment. We identified interferon signaling, viral response, and protein targeting pathways that are induced by insulin but dependent on Viperin in PIK3CAH1047R mutant cells. These results suggest a differential response to insulin signaling in mutated EE. 12Z endometriotic epithelial cells transfected with non-targeting siRNA and pBabe-PIK3CA*H1047R or empty vector, and were treated either with 100 nM insulin or vehicle. Cells were assayed 72 hours post-transfection via RNA-seq.