title: Mutagenesis of the Ha-ras oncogene in mouse skin tumors induced by polycyclic aromatic hydrocarbons.
abstract: The importance of mutational activation of the Ha-ras protooncogene in polycyclic aromatic hydrocarbon-induced mouse skin tumors was investigated in a complete carcinogenesis model using repetitive applications of 7,12-dimethylbenz[a]anthracene (DMBA), or in an initiation-promotion model using a single application of dibenz[c,h]acridine (DB[c,h]ACR) or benzo[a]pyrene (B[a]BP) followed by chronic treatment with phorbol 12-myristate 13-acetate. DNA isolated from carcinomas induced by DMBA or DB[c,h]ACR, but not by B[a]P, efficiently transformed NIH 3T3 cells, and a high percentage of the transformed foci had an amplified Ha-ras gene. Restriction enzyme Southern blot analysis and DNA sequencing revealed that the amplified Ha-ras genes of the transformants had an A----T transversion in the second position of the 61st codon. The same mutation was also detected in primary tumor DNA in a high percentage of the DMBA- or DB[c,h]ACR-induced carcinomas. Identification of the mutation in NIH 3T3 cells transformed with DNA from DB[c,h]ACR-induced benign skin papillomas suggests that it is an early event in skin carcinogenesis. Thus, mutation of the 61st codon of the Ha-ras-1 gene appears to be a critical step in the formation of mouse skin tumors induced in both of the two models tested. Our analyses also delineate two other classes of hydrocarbon-induced carcinomas--namely, tumors whose DNAs efficiently transform 3T3 cells but do not contain mutated ras genes and tumors whose DNAs do not transform 3T3 cells.
mesh_terms: D000818:Animals; D001483:Base Sequence; D002273:Carcinogens; D002471:Cell Transformation, Neoplastic; D003001:Cloning, Molecular; D004262:DNA Restriction Enzymes; D005260:Female; D051379:Mice; D009154:Mutation; D009857:Oncogenes; D011083:Polycyclic Compounds; D011110:Polymorphism, Genetic; D012878:Skin Neoplasms / Q000139:chemically induced / Q000235:genetics*
chemical_list: D002273:Carcinogens; D011083:Polycyclic Compounds; D004262:DNA Restriction Enzymes