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EFFECT OF ARSENICALS ON THE EXPRESSION OF CELL CYCLE PROTEINS AND EARLY SIGNALING EVENTS IN PRIMARY HUMAN KERATINOCYTES.
Citation:
Mudipalli, A, R D. Owen, AND R J. Preston. EFFECT OF ARSENICALS ON THE EXPRESSION OF CELL CYCLE PROTEINS AND EARLY SIGNALING EVENTS IN PRIMARY HUMAN KERATINOCYTES. Presented at 94th American Assoc. of Cancer Research, Washington, DC, 07/11-14/03.
Description:
Effect of Arsenicals on the Expression of Cell Cycle Proteins and Early Signaling Events in Primary Human Keratinocytes.
Mudipalli, A, Owen R. D. and R. J. Preston, Environmental Carcinogenesis Division, USEPA, RTP, NC 27711.
Environmental exposure to arsenic is a major public health problem. Epidemiological observations strongly indicate correlation between drinking water arsenic exposure and cancers of multiple types. At the cellular level, arsenite has multiple effects on cellular functions that include enhanced/delayed cell proliferation, increased differentiation and induction of apoptosis. The role of confounding factors such as UV light, adds yet another level of complexity to the study of arsenic carcinogenesis and risk assessment. To investigate the initial events critical for the initiation and propagation of cells leading to carcinogenesis a human primary keratinocyte cell model has been developed and is utilized in this laboratory. Primary cells were exposed to a single dose of UVB (100 mJ/cm2) to induce DNA damage/ growth arrest. Post UV treatment with various arsenicals [inorganic arsenite (iAs), and two methylated metabolites, methyl oxoarsine (MMA III) and iododimethyl arsine (DMA III)] increased proliferation of cells. This increase in proliferation observed at 48 h post exposure is concentration dependent and is in the order of DMA III > MMA III > iAs. Flow cytometric analyses revealed differential effects on cell cycle distribution. Significant differences in the expression of cell cycle proteins (Cyclin D1, Cdk5 and PCNA ) were also observed. These differences were dependent on UV exposure and/or methylation status of the arsenical.We then investigated cell cycle markers (cdc25A, cdc25C), upstream signal mediators (stress activated kinases) and the secretion of epidermal growth factor (EGF). Cells were exposed to a single dose of UVB(lOOmJ/cm2) and were given arsenicals at concentrations that induced maximal cell proliferation. The results indicate altered expression of cdc25A and cdc25C. Both iAs (6uM) and DMA III (0.4uM) increased the expression of cdc25A by 6 and 8 fold and cdc25C by 3 and 6 fold in UV treated cells at 24h, whereas their expression was decreased significantly in cells treated with MMA III. The expression of cdc25A and cdc25C were also found significantly increased when cells were treated with arsenicals alone. The expression of the phosphorylated stress activated protein kinase was found increased by 4-5 fold only in cells exposed to both UV and methylated arsenicals at 1h and 24h. In cells treated with arsenicals alone, EGF levels became detectable at 15 minutes and significantly higher (22-45%) at 6h. The present observations on the differential expression of these mediators in arsenical induced cell proliferation with and without UV, suggest participation of different upstream signaling events. Future efforts will be directed toward understanding these cellular responses. (This abstract does not reflect EPA policy).