RSPO1 and ovarian cancer: To functionally investigate the role of SFRP2 in ovarian cancer, we cultivated five epithelial ovarian cancer cell lines in the absence and presence of extracellular WNT effectors, including WNT3 (WNT) alone; WNT and RSPO1 (RSPO); WNT and SFRP2 (recombinant human protein); and WNT, RSPO and SFRP2 and tested the level of AXIN2 as a WNT/β-catenin target gene [31].