ABCB1 and cholangiocarcinoma: Mdr-1 gene overexpression found in many tumor cells including leukaemia (Yague et al., 2003), colon cancer (Hu, et al., 2016), breast cancer (David et al., 2004), hepatocellular carcinoma (Grude et al., 2002) and cholangiocarcinoma (Marin et al., 2018).