WNT4 and breast neoplasm: In contrast to normal human epithelial cells, HR‐positive breast tumors proliferate via autocrine mechanisms that involve PR‐induced expression of RANKL, Wnt4, and cyclin D1, as well as PR‐induced activation of protein kinases including CDK2, c‐Src, CK2, MAPK, and PI3K/AKT [46].