To verify whether CpG methylation has any regulatory effect on SFRP1 expression in CCA cells, we performed qRT-PCR assays to compare SFRP1 levels in 5-aza-2'-deoxycytidine (5-aza-dC, a DNA methyltransferase inhibitor)-treated and -untreated CCA cells. This evidence concerns the gene SFRP1 and cholangiocarcinoma.