title: Arsenic and benzo[a]pyrene differentially alter the capacity for differentiation and growth properties of primary human epidermal keratinocytes.
abstract: Normal human epidermal keratinocytes (NHEK) have been chosen as an in vitro model to test the hypothesis that chemicals which alter or interfere in cellular differentiation will concomitantly induce growth perturbations and are, thus, potential carcinogens. In these studies, we have focused on two known skin carcinogens, arsenic and benzo(a)pyrene (BaP). Our results demonstrated that BaP inhibits terminal differentiation in NHEK, as measured by cross-linked envelope (CLE) formation, up to 5.8-fold in control and 1.7-fold in calcium (Ca2+)-treated cells. In comparison, arsenic decreased CLE formation 20-fold in control cells and 5.5-fold in Ca2+-treated NHEK. To characterize the effects of these agents on the growth rate and cell cycle distributions of NHEK, flow cytometric analysis was used. BaP at 2 microM increased proliferation rates by 29%. Altered cell-cycle distribution in BaP-treated cells indicated a more rapid progression through the cell cycle, possibly by a shortened G2 phase. In contrast, arsenic at 5 microM inhibited proliferation by 25%; growth arrest (9%) was also observed in NHEK treated with 2 mM Ca2+. Our findings suggest that, although both BaP and arsenic inhibit CLE production in NHEK, different mechanisms may be involved. Studies in progress will attempt to identify molecular markers involved in the observed chemical effects. These markers will facilitate a mechanistic understanding of how an altered balance between growth and differentiation may play a role in the transformation process in NHEK.
authors.affiliation: Quantitative and Computational Toxicology Group, Center for Environmental Toxicology and Technology, and Department of Environmental Radiological Health Sciences, Colorado State University, Fort Collins, 80523, USA.
authors.forename: D S
authors.initials: DS
authors.lastname: Perez
authors.forename: L
authors.initials: L
authors.lastname: Armstrong-Lea
authors.forename: M H
authors.initials: MH
authors.lastname: Fox
authors.forename: R S H
authors.initials: RS
authors.lastname: Yang
authors.forename: J A
authors.initials: JA
authors.lastname: Campain
mesh_terms: D001151:Arsenic / Q000633:toxicity*; D001564:Benzo(a)pyrene / Q000633:toxicity*; D002118:Calcium / Q000494:pharmacology; D002273:Carcinogens / Q000633:toxicity*; D002453:Cell Cycle / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000032:analysis / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005434:Flow Cytometry; D006801:Humans; D007091:Image Processing, Computer-Assisted; D015603:Keratinocytes / Q000187:drug effects* / Q000473:pathology; D011003:Ploidies
chemical_list: D002273:Carcinogens; D001564:Benzo(a)pyrene; D004247:DNA; D001151:Arsenic; D002118:Calcium