title: Methylation-induced silencing of ASC/TMS1, a pro-apoptotic gene, is a late-stage event in colorectal cancer.
abstract: The hypermethylation of tumor-suppressor gene promoter regions has been shown to result in the epigenetic inactivation of many genes. ASC/TMS1 is a pro-apoptotic gene that has been shown to be methylated in many different human neoplasms. The methylation status of ASC/TMS1 was analyzed in a series of colorectal cancer (CRC) cell lines, adenomas and primary colorectal cancers and normal colorectal tissue samples using methylation-specific PCR (MSP). The gene expression of ASC/TMS1 in the CRC cell lines was analyzed using reverse-transcriptase PCR (RT-PCR). Methylation analysis showed complete methylation of ASC/TMS1 in 5 of 7 (71%) CRC cell lines. RT-PCR showed absence of mRNA expression in these same cell lines, and expression was restored after treatment with the demethylating drug 5-aza-2'-deoxyazacytidine. The two unmethylated cell lines showed ASC/TMS1 mRNA expression both before and after treatment with 5-aza-2'-deoxyazacytidine. Methylation was seen in 20 of 115 (17%) of primary colorectal cancer specimens, but no methylation was seen in 30 colorectal adenomas and 11 normal colorectal tissue samples. Methylation status of ASC/TMS1 was correlated with a series of clinicopathological variables using multivariate analysis. Methylation of ASC/TMS1 was more common in right-sided tumors (p = 0.02), concordant with hMLH1 methylation (p = 0.03) and is a late stage event, occurring in 0 of 18 tubular adenomas, 0 of 12 villous adenomas, 2 of 44 (5%) Stage 1 cancers, 8 of 31 (26%) Stage 2 cancers, 8 of 21 (38%) Stage 3 cancers and 2 of 19 (11%) Stage 4 cancers. The ASC/TMS1 gene is frequently silenced in CRC due to promoter hypermethylation. Methylation of ASC/TMS1 appears to be a late-stage event in colorectal carcinogenesis associated with invasive carcinomas but not with normal colorectal tissue or colorectal adenomas. Methylation of ASC/TMS1 may have implications for cancer prognosis.
authors.affiliation: Department of Surgery, Johns Hopkins University, Baltimore, Maryland, USA.
authors.forename: Marco A
authors.initials: MA
authors.lastname: Riojas
authors.forename: Mingzhou
authors.initials: M
authors.lastname: Guo
authors.forename: Sabine C
authors.initials: SC
authors.lastname: Glöckner
authors.forename: Emi Ota
authors.initials: EO
authors.lastname: Machida
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Baylin
authors.forename: Nita
authors.initials: N
authors.lastname: Ahuja
mesh_terms: D000328:Adult; D000368:Aged; D053468:CARD Signaling Adaptor Proteins; D045744:Cell Line, Tumor; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000473:pathology; D003598:Cytoskeletal Proteins / Q000235:genetics*; D019175:DNA Methylation; D005260:Female; D020868:Gene Silencing; D006801:Humans; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D053468:CARD Signaling Adaptor Proteins; D003598:Cytoskeletal Proteins; C402202:PYCARD protein, human; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha