title: Elevated expression of Ha-ras is an early event in two-stage skin carcinogenesis in SENCAR mice.
abstract: Alterations in the expression of the Ha-ras oncogene were investigated in SENCAR mice epidermis at various stages of initiation and promotion during two-stage skin carcinogenesis in SENCAR mice. Adult SENCAR mice were treated with 200 nmol of the (+) enantiomer of benzo[a]pyrene 7,8-diol 9,10-epoxide-anti (BPDE-anti), a potent initiating agent, followed by repetitive treatments with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Other mice were 'sham'-initiated with the (-) enantiomer of BPDE-anti, which is inactive as a tumor initiator. Polyadenylated RNA was isolated from pre-tumor epidermis and tumors at eight different stages of tumorigenesis and analyzed for changes in Ha-ras expression using Northern blot hybridization. Significantly enhanced levels of Ha-ras RNA were observed in TPA-promoted papillomas as early as 7 weeks after initiation. Only trace amounts of Ha-ras RNA were present in untreated epidermis or epidermis treated with the (+) or (-) enantiomer followed by 2-12 treatments with TPA (pre-papilloma stage). Southern blot hybridization of tumor DNA indicated that the increased expression of the Ha-ras oncogene was not due to gene amplification. We conclude that elevated levels of Ha-ras expression can occur at an early stage of tumor development in mouse epidermis in vivo and may play a role in tumorigenesis.
mesh_terms: D000818:Animals; D005260:Female; D005784:Gene Amplification; D051379:Mice; D008815:Mice, Inbred Strains; D009693:Nucleic Acid Hybridization; D010212:Papilloma / Q000235:genetics; D011061:Poly A / Q000032:analysis; D011519:Proto-Oncogenes; D012313:RNA / Q000032:analysis; D012333:RNA, Messenger; D012878:Skin Neoplasms / Q000139:chemically induced / Q000235:genetics*; D013755:Tetradecanoylphorbol Acetate
chemical_list: D012333:RNA, Messenger; D011061:Poly A; D012313:RNA; D013755:Tetradecanoylphorbol Acetate