RNF43 and breast carcinoma: To further confirm that activation of Wnt/β-catenin signaling is responsible for RCOR2-induced breast cancer cell plasticity, we treated RCOR2-KO1 MDA-MB-231 cells with a specific GSK3 inhibitor, CHIR99021 (1 μM), which can bypass RNF43 to activate β-catenin.