RNF43 and cholangiocarcinoma: The cholangiocarcinoma cell line EGI‐1 (Wnt‐addicted due to an R‐spondin translocation), the ovarian cancer cell line MCAS (Wnt‐addicted due to an RNF43 mutation), and the pancreatic cancer cell line CFPAC‐1 (sensitive to Wnt inhibition, mechanism unknown) were used.