PDCD4 and cholangiocarcinoma: A different study by Selaru et al. confirmed an overexpression of miR-21 in human CCA tissues in relation to non-cancer tissues [65] and showed that miR-21 induced carcinogenesis in CCA by downregulating the expression of programmed cell death 4 (PDCD4) and tissue inhibitor of metalloproteinase (TIMP) 3.