IER5 Promotes Ovarian Cancer Cell Proliferation and Peritoneal Dissemination.

Background/Objective: Ovarian cancer (OC) is one of the most lethal gynecological cancers, having a worldwide mortality rate of 66% in 2020. The overall 5-year relative survival rate is only 21% for distant stages, due to the lack of early diagnosis. Epithelial OC, the most common high-grade serous carcinoma, carries p53 mutations in most cases. However, we found that the immediate early response 5 gene (IER5), a p53 target gene, is overexpressed in ovarian cancer cells. The molecular mechanism underlying the role of IER5 in OC has not been well studied. We previously reported that IER5 promotes the dephosphorylation and activation of heat shock factor-1 (HSF1), the master regulator of proteostasis, which induces heat shock protein (HSP) expression. Methods/Results: Here we show that Ier5 mRNA expression is higher in ovarian cancer cells (MOV, ID8G, and HM-1) compared to normal ovarian cells. We also show that OC cells floating in the ascites have higher Ier5 expression than the parental strain. Knockdown of Ier5 suppressed HSP upregulation and proliferation of OC, while overexpression of IER5 promoted HSP upregulation. Knockdown of Hsf1 showed results similar to Ier5 knockdown. Conclusions: These results indicate that the IER5-HSF1 pathway contributes to the proliferation and peritoneal dissemination of OC cells. We also found that higher expression of IER5 family genes is related to poorer prognosis of OC patients, suggesting the potential of the IER5 gene family as diagnostic markers for OC, as well as potential therapeutic targets.