POU5F1 and cholangiocarcinoma: Based on univariate Cox regression analysis, OCT4+CTC (versus none CTC) [hazard ratio (HR) = 5.540, P = 0.001], previous chemotherapy (versus no) (HR = 3.093, P = 0.002), and treatment line of second or above (versus first) (HR = 3.093, P = 0.002) were related to shorter PFS in advanced CCA patients (Fig. 4A).