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DNA hypermethylation and loss of expression of the P16 tumor suppressor gene in cadmium transformed BALB/C-3T3 cells.
Joseph-P; Lei-Y; Muchnok-T; Ong-T
Environ Mol Mutagen 2001 Mar; 37(32):41
In spite of its weak mutagenic potential, cadmium has been shown to be carcinogenic in laboratory animals. The underlying molecular mechanisms responsible for cadmium (Cd)-induced cell transformation and carcinogenesis, however, are not clearly understood. We have undertaken studies investigation aberrant DNA methylation resulting in changes in the expression of cancer-related genes as a possible epigenetic mechanism for Cd carcinogenesis. Genomic DNA isolated from BALB/c-3T3 cells morphologically transformed with Cd was restriction digested with Mse1 (methylation non-sensitive) alone or with MSe1 and BstU1 (methylation sensitive). The resulting DNA was analyzed for differential methylation using a PCR-based technique - Methylation Sensitive Restriction Fingerprinting (MSRF). DNA fragments differentially methylated in the transformed cells compared with the non-transformed cells were indentified by MSRF and subcloned into the TA-cloning vector. The results of MSRF were confirmed by southern hybridization analysis using the aberrantly methylated DNA fragments as the probes. DNA sequencing and sequence similarity analysis identified one of the aberrantlyl methylated DNA fragments as the p16 tumor suppressor gene. Further studies have shown that the expression of p16 tumor suppressor gene was significantly lower in the transformed cells compared wiht the non-transformed cells. Since DNA hypermethylation is known to result in gene silencing, it appears that the decreased expression p16 gene in the Cd transformed BALB/c-3T3 cells may be due to its hypermethylation. Further, decreased expression of the p16 gene may in part be responsible for the Cd-induced cell transformation and tumorigenesis.
Cadmium-compounds; Cell-transformation; Tumors; DNA-damage; Laboratory-animals; Animals; Animal-studies; Carcinogenesis; Carcinogenicity; Carcinogens; Tumorigens; Tumorigenesis
Toxicology and Molecular Biology Branch, Health Effects Laboratory Division, CDC/NIOSH, 1095 Willowdale Road, Morgantown, WV 26505
Abstract; Conference/Symposia Proceedings
Issue of Publication
Environmental and Molecular Mutagenesis
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