E2F1 and cholangiocarcinoma: To explore the relationship between FOXM1, E2F1 and TYMS expression and their functional roles in CCA, western blot and real-time quantitative PCR (qPCR) analyses were performed to determine the baseline steady-state expression levels of FOXM1 and TYMS, as well as one of their known regulator E2F1, in four CCA cell lines25.