NOTUM and ovarian cancer: In this study, the top 3 Wnt signaling pathway-related genes were RSPO4, NOTUM, and SFRP5. R-spondin 4 (RSPO4) is an agonist of the Wnt signaling pathway, and was elevated about 2.5 folds in the high-risk population in our study, indicating that RSPO4 may promote ovarian cancer progression through activation of the Wnt pathway.