CDK4 and cholangiocarcinoma: To understand the molecular mechanisms by which TLPE extract induces apoptosis and cell cycle arrest in CCA cell lines, the expression levels of Bcl2 (anti-apoptotic protein), Bax (pro-apoptotic protein), p53 (tumor suppressor protein) and cell cycle-related proteins (p21; inhibitor of cyclin dependent kinases, CDK4; the progression through the G1 phase) were examined.