13-cis-retinoic acid inhibits the self-renewal, migration, invasion and adhesion of cholangiocarcinoma cells

13-cis-retinoic acid (13CRA), a Food and Drug Administration-approved drug for severe acne, is currently being investigated for its potential use in skin cancer prevention. 13CRA has been reported to exhibit antitumor effects against various types of cancer cells, both in vitro and in vivo. However, to the best of our knowledge, no information is yet available regarding the effects of 13CRA on cholangiocarcinoma (CCA), a malignancy of the bile duct epithelia. Currently, there are no reliably effective therapeutic options for metastatic CCA. The present study thus aimed to evaluate the effects of 13CRA on the self-renewal, migration, invasion and adhesion of CCA cells, and also investigated the underlying mechanisms. The results revealed that 13CRA suppressed cell proliferation via the inhibition of the self-renewal ability of CCA cells. 13CRA induced cell cycle arrest at the G(2)/M phase in KKU-100 and KKU-213B CCA cells through the regulation of cell cycle-regulatory genes and proteins. 13CRA reduced the cell migratory ability of both cell lines via the modulation of the genes and proteins associated with epithelial-mesenchymal transition. 13CRA also inhibited the invasive and adhesive abilities of CCA cells via the suppression of genes and proteins associated with the invasion and adhesion of CCA cells. On the whole, these results suggested that 13CRA exerts suppressive effects on CCA cell proliferation, migration, adhesion and invasion.