ALDH1A1 and cholangiocarcinoma: The Wnt-β-catenin pathway has been shown to be activated in cancer cells with high expression of ALDH1A1 and ALDH3A1 in prostate, ovarian, and liver cancer cells [86, 90, 110]; and the TGFβ pathway has been reported to facilitate therapy resistance in ALDHhi breast cancer cells, and to be involved in expression of ALDH1A1 in cholangiocarcinoma and pancreatic cancer [90, 103, 151, 152].