CUL4A and intrahepatic cholangiocarcinoma: We examined two iCCA cell lines and 86 cases of intrahepatic cholangiocarcinoma to analyze copy number of three target genes, including cullin 4A (CUL4A), insulin receptor substrate 2 (IRS2), and transcription factor Dp-1 (TFDP1) at 13q34 by quantitative real-time polymerase chain reaction.