ESR1 and breast cancer: INPP4B-overexpressing PIK3CA-mutant ER+ breast cancer cells were selectively sensitive to nanomolar concentrations of pyrvinium [102], an FDA-approved anthelmintic drug that binds and activates CK1α to suppress Wnt/β-catenin signaling [103], and were significantly more sensitive to pyrvinium in combination with the standard-of-care treatment 4-hydroxytamoxifen (4-OHT) [102].