CDK4 and intrahepatic cholangiocarcinoma: Meanwhile, PTK7 silencing induced apoptosis and also mediated a slight decrease in the expression levels of the cell cycle-related proteins CDK2, CDK4, CDK6, and cyclin D1, along with an increase in the expression levels of p16, p21, and p27, which may be a potential mechanism by which PTK7 silencing inhibits ICC progression.