title: Allele loss and point mutation in codons 12 and 61 of the c-Ha-ras oncogene in carcinogen-transformed human breast epithelial cells.
abstract: There is significant evidence that the ras oncogene plays a role in experimental mammary carcinogenesis; the evidence in human breast cancer, however, is more limited. We induced the expression of transformation phenotypes in the human breast epithelial cell line MCF-10F with the chemical carcinogens 7,12-dimethylbenz[a]anthracene, N-methyl-N-nitrosourea, N-methyl-N-nitro-N'-nitrosoguanidine, and benzo[a]pyrene. This work was designed to clarify whether chemically induced neoplastic transformation correlates with alterations in the ras gene. MCF-10F cells have two c-Ha-ras alleles, identified by 1.0-kb and 1.2-kb restriction fragments. Treatment with carcinogens resulted in the loss of one of the alleles (1.0 kb). Polymerase chain reaction-amplified DNA from all carcinogen-treated cells was analyzed for point mutations in c-Ha-ras at codons 12 and 61. All of the carcinogens induced a mutation of the remaining allele at the first position of codon 12 (GGC-->AGC). Another frequent mutation occurred at the first position of codon 61 (CAG-->GAG). The changes in c-Ha-ras were associated with the emergence of colony formation in agar-methocel, but no specific changes in this gene correlated with the emergence of invasiveness or tumorigenesis, indicating that other genes may be involved in the process.
authors.affiliation: Department of Pathology, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111.
authors.forename: P L
authors.initials: PL
authors.lastname: Zhang
authors.forename: G
authors.initials: G
authors.lastname: Calaf
authors.forename: J
authors.initials: J
authors.lastname: Russo
mesh_terms: D000328:Adult; D000483:Alleles; D000818:Animals; D001483:Base Sequence; D001940:Breast / Q000187:drug effects; D001943:Breast Neoplasms / Q000139:chemically induced* / Q000235:genetics*; D015197:Carcinogenicity Tests; D002273:Carcinogens; D002460:Cell Line; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D003062:Codon / Q000235:genetics*; D015342:DNA Probes; D004273:DNA, Neoplasm / Q000235:genetics; D004848:Epithelium / Q000473:pathology / Q000502:physiology; D005260:Female; D005784:Gene Amplification; D017353:Gene Deletion; D011905:Genes, ras / Q000235:genetics*; D006801:Humans; D015151:Immunoblotting; D051379:Mice; D016513:Mice, SCID; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D010641:Phenotype; D017354:Point Mutation / Q000187:drug effects / Q000235:genetics*; D016133:Polymerase Chain Reaction
chemical_list: D002273:Carcinogens; D003062:Codon; D015342:DNA Probes; D004273:DNA, Neoplasm