PTEN and cholangiocarcinoma: Their data further suggest that cholangiocarcinoma arise from hepatocyte-derived cholangiocytes, whereby PTEN deletion resulted in up-regulation of TGFBR2, and deletion of TGFBR2 increased cholangiocyte proliferation, indicating that the main function of epithelial TGFBR2 is to restrict cholangiocyte proliferation.108