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METHYLATION OF ARSENITE BY SOME MAMMALIAN CELL LINES
Sharma, R, B. Peng, A D. Kligerman, AND M J. Mass. METHYLATION OF ARSENITE BY SOME MAMMALIAN CELL LINES. Presented at Impact of Biotechnology on Cancer: Predictive Oncology & Therapy: Diagnostic & Prognostic Indicators, Geneva, Switzerland, Oct. 28-31, 2000.
THIS ABSTRACT WAS SUBMITTED ELECTRONICALLY;. SPACE CONSTRAINTS WERE SEVERE)
Methylation of Arsenite by Some Mammalian Cell Lines.
Methylation of arsenite is thought to play an important role in the carcinogenicity of arsenic.
Aim 1: Determine if there is differential methylation of arsenite in various mammalian cells that can explain tissue, cell, or species specific sensitivity to arsenic carcinogenicity or toxicity. Aim 2: Determine if arsenite methyltransferase (AMTase) expression is repressed in culture and can be activated by a DNA hypomethylating agent, 5-aza-2'-deoxycytidine (5-aza-dC).
Methods: Several mammalian cell lines originating from neoplasms of(l) human liver HepG2, (2) human non-small cell lung cancer (NSCLC, A549), (3) human small cell lung cancer (SCLC, H82), human renal cancers, (4) UOK 121, (5) UOK 123, (6) human testicular cancer (CRL- 1973), and primary lymphocytes of (7) human, (8) guinea pig, (9) mouse and (10) rat were used for differential dose-dependent methylation studies of arsenite. Two million cells were exposed to several concentrations of 73 As-sodium arsenite for 48 hr. Cell and media fractions were analyzed for inorganic As (III) (iAs), monomethylarsonic acid (MMA(V)) and dimethylarsinic
acid (DMA(V)). HepG2 cells were pretreated with 5-aza-dC for 48 hr before methylation studies using 0.1 uM arsenite.
Results: In both human neoplastic tissues and mammalian primary lymphocytes, DMA production increased linearly at low arsenite concentrations; MMA production did not. DMA formation decreased and MMA formation increased at higher arsenite concentrations. Data expressed as DMA + MMA metabolite levels at 0.5 uM arsenite, pmol/10.6 cells 148 hr incubation (cell source): 181 + 18.69 (6),93.70 + 62.34 (1),29.04 + 66.63 (4),7.27 + 14.72 (5), 3.98 + 5.58 (3),0 + 4.84 (2); at 5 ~M arsenite, 38.31+315.80 (7),105+125.67 (8),59.44 +
136.25 (9),638.63 + 1044.77 (10). In HepG2 cells, MMA formation decreased and more iAs was left unmethylated upon 0.5 uM 5-aza-dC treatment (pmo11106 cells 148 hr; control vs. treated: DMA, 65 vs. 60; MMA, 22 vs.13; iAs, 13 vs. 33).
Conclusion: Tissue-specific differential methylation was observed in both primary and neoplastic cell lines. Methylation capacity based on DMA formation in human neoplastic cells was as follows: testis> liver> kidney >lung; in primary lymphocytes methylation capacity was ordered as follows: rat>guinea pig> mouse> human. 5-aza-dC enhanced AMTase activity in HepG2 cells by approximately 2- fold.
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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
BIOCHEMISTRY AND PATHOBIOLOGY BRANCH