Aberrant methylation of secreted frizzled-related protein genes in tissues of colorectal cancer and cancer cell lines

Abstract

Objective To investigate the association of promoter hypermethylation of secreted frizzled-related proteins (SFRPs) in patients with colorectal cancer. Methods The promoter hypermethylation of SFRPs in 20 sporadic colorectal cancer tissues and adjacent mucosa were detected by methylation-specific PCR. The amplified DNA was subcloned into the T-A cloning vector and sequenced. Two colorectal cancer cell lines (HCT116 and SW480) were treated with 5-aza-2' deoxycytidine for demethylation. The promoter hypermethylation and protein expression of SFRPs in colorectal cancer cell lines were detected by methylation-specific PCR and Western blotting. Results It was demonstrated that the hypermethylation of SFRP 1, 2, 4 or 5 was 19/20,17/20,3/20 or 13/20in cancer tissues, respectively, whereas it was 12/20, 8/12, 1/20 or 7/20 in adjacent mucosa,respectively. SFRP 1, 2 or 5 methylation was more frequently found in cancer tissue than in adjacent mucosa (P～0.05). Methylation of SFRP 1, 2, 4 and 5 were found in HCT116 cell line, but only SFRP1 and SFRP2 were found in SW480 cell line. There was a negative correlation between protein expression and methylation of SFRPs. The Western blotting revealed that SFRP protein re-expressedafter it treated with 5-aza-2' deoxyeytidine. Conclusion Methylation of SFRP 1, 2 or 5 gene is associated with the evolution of eolorectal cancer, and is closely related to silencing expression. Key words: Colorectal neoplasms; Methylation; Secreted frizzled-related protein genes