title: Systemic modulation by ultraviolet irradiation of cutaneous N-methyl-N'-nitro-N-nitrosoguanidine-induced carcinogenesis.
abstract: Ultraviolet irradiation can systemically enhance subsequent skin cancer induction by benzo[a]pyrene, methylcholanthrene, or UV radiation. The present study was designed to determine whether UVB irradiation influences host susceptibility to the alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Female C3H/HeJ mice were exposed dorsally to UVB radiation from banks of 6 Westinghouse FS40 sun lamps. The mice received a total UV dose of approximately 8.1 x 10(5) J m-2 over a 15-week period. After termination of UVB treatments, ventral tumors were induced by 4 applications of 30 mumol of MNNG at 8-day intervals. At 20 weeks after the first MNNG treatment, UVB-irradiated mice had 7-fold more MNNG-induced, ventral tumors than did the unirradiated control mice (P = 0.026, Wilcoxon rank sum test). Ventral application of MNNG after cessation of dorsal UVB exposure, but before UV tumor appearance, did not influence photocarcinogenesis. These results demonstrate that UV irradiation can systemically decrease host resistance to tumor induction by the methylating agent, MNNG.
authors.affiliation: Department of Radiation Oncology, University of Arizona, College of Medicine, Tucson 85724.
authors.forename: H L
authors.initials: HL
authors.lastname: Gensler
mesh_terms: D000818:Animals; D005260:Female; D008769:Methylnitronitrosoguanidine / Q000633:toxicity*; D051379:Mice; D008809:Mice, Inbred C3H; D009374:Neoplasms, Experimental / Q000139:chemically induced / Q000209:etiology*; D009381:Neoplasms, Radiation-Induced / Q000209:etiology; D012878:Skin Neoplasms / Q000139:chemically induced / Q000209:etiology*; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D008769:Methylnitronitrosoguanidine