OBJECTIVETo study aberrant DNA methylation potentially resulting in changes in the expression of cancer-related genes as a possible epigenetic mechanism for cadmium carcinogenesis.

METHODSGenomic DNA isolated from CdCl(2)-transformed BALB/c-3T3 cells was digested with Mse1 (methylation non-sensitive) alone or with Mse1 and BstU1 (methylation sensitive). The resulting DNA was analyzed for aberrant methylation using PCR-based technique-Methylation-Sensitive Restriction Fingerprinting (MSRF). Several DNA fragments differentially methylated in the transformed cells identified by MSRF were confirmed by Southern hybridization analysis using the aberrantly methylated DNA fragments as the probes.

RESULTSAberrant DNA methylation was identified in the transformed cells. DNA sequencing and sequence similarity analysis identified one of the aberrantly methylated DNA fragments as the p16 tumor suppressor gene.

CONCLUSIONDNA hypermethylation is known to result in gene silencing, it appears that hypermethylation of p16 gene may represent a possible epigenetic mechanism for Cd-induced cell transformation and carcinogenesis.

Animals ; BALB 3T3 Cells ; Blotting, Southern ; Cadmium ; toxicity ; Cell Transformation, Neoplastic ; CpG Islands ; DNA Methylation ; Genes, p16 ; Mice ; Restriction Mapping