This project has two interrelated goals. The first goal is to answer the question of whether initiation in vivo is a common (e.g., 1 per 1000 cells or more frequent) or rare event at the cellular level. Initiation is defined here as a cellular change (lesion) that is directly and rapidly induced by carcinogen exposure and leads to the formation of a malignant neoplasm. This first goal will be addressed by quantitating the frequency of initiation in rat mammary epithelial cells following in situ exposure to each of the mammary carcinogens NMU and DMBA. This will be accomplished using a limiting dilution transplantation assay that we have developed for this purpose. The second related goal of this project is to examine the hypothesis that activation of the c-Ha-ras-1 oncogene is at least one possible primary cellular change responsible for cellular initiation of carcinogenesis in the rat mammary gland. Carcinomas developing from known numbers of exposed surviving target cells in the experiments relating to the first goal will be examined to determine if they possess an activated c-Ha-ras-1 gene, i.e. is this gene mutated at codon 12 (NMU-induced) or 61 (DMBA-induced). Restriction mapping will be the primary method used for this determination. This will be followed by oligonucleotide hybridization for determination of specific base substitutions in the altered c-Ha-ras-1. The data obtained from these measurements will allow us to answer the question of whether c-Ha-ras-1 activation is an early event. If it is an early event, its frequency per exposed mammary cell will also be calculated from these data. In addition, we will quantitate mutation frequency at other loci from similarly exposed cells in order to address the question of the relative """"""""hotness"""""""" (propensity to mutate) of c-Ha-ras-1. Finally, these experiments will be extended to a physical carcinogen, ionizing radiation. This carcinogen will be explored because, unlike DMBA and NMU, it is an efficient inducer of deletions. Thus, a different mutation spectrum would be expected. We feel that the experiments proposed here will aid our understanding of the etiology of mammary cancer. This understanding may lead to new approaches to cancer prevention.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
1R01CA044387-01
Application #
3186946
Study Section
Chemical Pathology Study Section (CPA)
Project Start
1987-07-01
Project End
1992-06-30
Budget Start
1987-07-01
Budget End
1988-06-30
Support Year
1
Fiscal Year
1987
Total Cost
Indirect Cost
Name
University of Wisconsin Madison
Department
Type
Schools of Medicine
DUNS #
161202122
City
Madison
State
WI
Country
United States
Zip Code
53715
Thompson, T A; Kim, K; Gould, M N (1998) Harvey ras results in a higher frequency of mammary carcinomas than Kirsten ras after direct retroviral transfer into the rat mammary gland. Cancer Res 58:5097-104
Gould, M N (1995) Rodent models for the study of etiology, prevention and treatment of breast cancer. Semin Cancer Biol 6:147-52
Ariazi, E A; Thompson, T A; Burkholder, J K et al. (1995) Transcriptional regulatory and response mapping of the rat Ha-ras upstream sequence using primary mammary epithelial cells. Carcinogenesis 16:965-8
Kamiya, K; Yasukawa-Barnes, J; Mitchen, J M et al. (1995) Evidence that carcinogenesis involves an imbalance between epigenetic high-frequency initiation and suppression of promotion. Proc Natl Acad Sci U S A 92:1332-6
Thompson, T A; Gould, M N; Burkholder, J K et al. (1993) Transient promoter activity in primary rat mammary epithelial cells evaluated using particle bombardment gene transfer. In Vitro Cell Dev Biol 29A:165-70
Gould, M N (1993) Cellular and molecular aspects of the multistage progression of mammary carcinogenesis in humans and rats. Semin Cancer Biol 4:161-9
Oakley, C S; Welsch, M A; Zhai, Y F et al. (1993) Comparative abilities of athymic nude mice and severe combined immune deficient (SCID) mice to accept transplants of induced rat mammary carcinomas: enhanced transplantation efficiency of those rat mammary carcinomas that have elevated expression of neu o Int J Cancer 53:1002-7
Wang, B; Kennan, W S; Yasukawa-Barnes, J et al. (1992) Difference in the response of neu and ras oncogene-induced rat mammary carcinomas to early and late ovariectomy. Cancer Res 52:4102-5
Wang, B; Kennan, W S; Yasukawa-Barnes, J et al. (1991) Frequent induction of mammary carcinomas following neu oncogene transfer into in situ mammary epithelial cells of susceptible and resistant rat strains. Cancer Res 51:5649-54
Gould, M N; Clifton, K H; Kamiya, K et al. (1991) Quantitative and molecular comparison of initiation frequency of mammary carcinogenesis by radiation and chemical carcinogens. Radiat Environ Biophys 30:221-3

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