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EFFECT OF ARSENICALS ON CELL CYCLE DISTRIBUTION AND EXPRESSION OF CELL CYCLE PROTEINS IN HUMAN PRIMARY KERATINOCYTES
Mudipalli, A, R J. Preston, AND J C. Fuscoe. EFFECT OF ARSENICALS ON CELL CYCLE DISTRIBUTION AND EXPRESSION OF CELL CYCLE PROTEINS IN HUMAN PRIMARY KERATINOCYTES. Presented at New Hampshire Arsenic Consortium, Manchester, NH, May, 29-31, 2002.
Environmental exposure to arsenic is a major public health concern. Epidemiological studies have demonstrated a strong correlation between levels of arsenic in drinking water and incidence of cancers of skin, lung, bladder and peripheral and cerebro vascular diseases. Despite enormous efforts to understand the biological effects of arsenic, the specific mechanism(s) of action for cancer development are very poorly understood. The role of confounding factors such as UV adds another dimension to the study of arsenic carcinogenesis and risk assessment. Here we hypothesize that arsenicals may cause an override of cell cycle arrest caused by a DNA damaging agent such as UV, and promote the proliferation of unrepaired cells. An in vitro human primary keratinocyte model was developed to study the initial cell cycle events pertaining to the initiation and propagation of cells leading to cancer. Cells were treated with a single dose of UVB (100mJ/cm2) and then exposed to various concentrations of arsenite (iAs; 0-12uM) and two of the trivalent methyl derivatives, methyl oxoarsenie (MAsIII; 0-2uM), and iododimethyl arsine (DMAsIII;0-3uM), for 48h. Cell proliferation indices and cell cycle distributions were determined by MTT (3- [4,5-dimethyl thiazol -2-yl] 2, 5- diphenyl- tetrazolium bromide) and flow cytometric analyses, respectively. Additional controls include treatment with arsenicals but not UV, UV alone, and untreated cells. At 48h arsenicals were found to significantly increase the cell proliferation in a concentration dependent manner in UV exposed cells (DMAsIII> MasIII> iAs ) as compared to UV exposed controls. Flow cytometric analyses revealed differential effects on cell cycle distribution. These data suggest that arsenicals are capable of overriding the cell cycle arrest caused by UV-induced DNA damage. Preliminary studies on the expression of cell cycle specific proteins by western blot analysis indicated significant differences in the expression of Cyclin D1, CdK5 and PCNA, that were dependent on UV exposure and/or methylation status of arsenic (with several fold increase in PCNA and decrease in Cdk5 expression in UV-exposed cells treated with methylated arsenicals). These results indicate that arsenicals are capable of overriding the cell cycle arrest caused by UV damage by the up or down regulation of specific cell cycle proteins. Replication on a damaged template may result in mutations that initiate carcinogenesis associated with As exposure. Further studies utilizing this in vitro cell culture model may aid in elucidating the molecular mechanisms involved in arsenic carcinogenicity.
This abstract does not reflect US EPA policy.
Record Details:Record Type: DOCUMENT (PRESENTATION/ABSTRACT)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LABORATORY
ENVIRONMENTAL CARCINOGENESIS DIVISION
MOLECULAR TOXICOLOGY BRANCH