ALLELE LOSS AND POINT MUTATION IN CODON-12 AND CODON-61 OF THE C-HA-RAS ONCOGENE IN CARCINOGEN-TRANSFORMED HUMAN BREAST EPITHELIAL-CELLS

There is significant evidence that the ras oncogene plays a role in ex perimental mammary carcinogenesis; the evidence in human breast cancer , however, is more limited. We induced the expression of transformatio n phenotypes in the human breast epithelial cell line MCF-10F with the chemical carcinogens 7,12-dimethylbenz[a]anthracene, N-methyl-N-nitro sourea, N-methyl-N-nitro-N'-nitrosoguanidine, and benzo[a]pyrene. This work was designed to clarify whether chemically induced neoplastic tr ansformation correlates with alterations in the ras gene. MCF-10F cell s have two c-Ha-ras alleles, identified by 1.0-kb and 1.2-kb restricti on fragments. Treatment with carcinogens resulted in the loss of one o f the alleles (1.0 kb). Polymerase chain reaction-amplified DNA from a ll carcinogen-treated cells was analyzed for point mutations in c-Ha-r as at codons 12 and 61. All of the carcinogens induced a mutation of t he remaining allele at the first position of codon 12 (GGC-->ACC). Ano ther 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 ge ne correlated with the emergence of invasiveness or tumorigenesis, ind icating that other genes may be involved in the process. (C) 1994 Wile y-Liss, Inc.