Targeting cancer stem cells in cholangiocarcinoma (Review).

The incidence of cholangiocarcinoma has been increasing steadily over the past 50 years, but the survival rates remained low due to the disease being highly resistant to non‑surgical treatment interventions. Cancer stem cell markers are expressed in cholangiocarcinoma, suggesting that they serve a significant role in the physiology of the disease. Cancer stem cells are frequently implicated in tumor relapse and acquired resistance to a number of therapeutic strategies, including chemotherapy, radiation and immune checkpoint inhibitors. Novel targeted therapies to eradicate cancer stem cells may assist in overcoming treatment resistance in cholangiocarcinoma and reduce the rates of relapse and recurrence. Several signaling pathways have been previously documented to regulate the development and survival of cancer stem cells, including Notch, janus kinase/STAT, Hippo/yes‑associated protein 1 (YAP1), Wnt and Hedgehog signaling. Although pharmacological agents have been developed to target these pathways, only modest effects were reported in clinical trials. The Hippo/YAP1 signaling pathway has come to the forefront in the field of cancer stem cell research due to its reported involvement in epithelium‑mesenchymal transition, cell adhesion, organogenesis and tumorigenesis. In the present article, recent findings in terms of cancer stem cell research in cholangiocarcinoma were reviewed, where the potential therapeutic targeting of cancer stem cells in this disease was discussed.