title: The effect of arsenicals on ultraviolet-radiation-induced growth arrest and related signaling events in human keratinocytes.
abstract: The molecular mechanisms mediating arsenic-induced carcinogenesis are not well understood. The role of confounding factors such as ultraviolet radiation (UV), add another level of complexity to the study of arsenic carcinogenesis and the cancer-risk assessment on humans. We hypothesized that arsenicals are capable of overriding the growth arrest caused by UV treatment and may lead to selective proliferation. To test this hypothesis, a primary normal human epidermal keratinocyte (NHEK) cell culture model was used. One group was pre-exposed to UVB (100 mJ/cm(2)) that arrested a majority ( approximately 95%) of cells in G0/G1 (+UV) and a second group was not exposed to UV (-UV). Treatment of cells with various arsenicals [0-12 microM of inorganic arsenite (iAs), 0-2 microM of methyl oxoarsine (MMAs III) and 0-3 microM of iododimethyl arsine (DMAs III)] indicated a concentration-dependent increase in proliferation at 24 h in the order of DMAs III > MMAs III > iAs. Flow-cytometric analyses revealed differential effects on cell cycle distribution. Analysis of a battery of cell cycle proteins (cyclin D1, cdk5, PCNA, cdc25A and cdc25C) indicated exposure-specific differential expression profiles. Increased activation of JNK phosphorylation (5-10-fold) in the +UV group and the synergistic increase with methyl arsenicals suggested that JNK might be involved in cell survival and proliferative signaling. Induction of EGF levels and increased phosphorylation of the EGF receptor by arsenicals (+UV) suggested that the EGF signaling pathway might mediate arsenical-induced cell proliferation of NHEK cells. Differential activation of ERK1/2 by arsenicals (+/-UV) suggested that EGF-mediated cell proliferation by arsenicals in UV-treated NHEK cells may not involve ERK activation. Taken together, the data suggest that both UV exposure and methylation status of the arsenicals dictate the participation of key cell cycle proteins and related signaling events in arsenical-induced cell proliferation.
authors.affiliation: Environmental Carcinogenesis Division, National Health and Environmental Effects Research Laboratory, ORD, US EPA, Research Triangle Park, NC 27711, USA. mudipalli.anu@epa.gov
authors.forename: Anuradha
authors.initials: A
authors.lastname: Mudipalli
authors.forename: Russell D
authors.initials: RD
authors.lastname: Owen
authors.forename: R Julian
authors.initials: RJ
authors.lastname: Preston
mesh_terms: D001152:Arsenicals / Q000494:pharmacology*; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects / Q000528:radiation effects; D018797:Cell Cycle Proteins / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects* / Q000528:radiation effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004797:Enzyme-Linked Immunosorbent Assay; D004815:Epidermal Growth Factor / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects / Q000528:radiation effects; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects / Q000528:radiation effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects* / Q000528:radiation effects; D016159:Tumor Suppressor Protein p53 / Q000235:genetics; D014466:Ultraviolet Rays
chemical_list: D001152:Arsenicals; D018797:Cell Cycle Proteins; D018809:Proliferating Cell Nuclear Antigen; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3