The long-term objective of this research is to elucidate the mechanisms of low-dose radiation-induced carcinogenesis through studying its effects on a series of specific membrane-associated pathways known to be rapidly activated in whole or in part by the tumor promoting agents 12-0-tetradecanoyl-phorbol-13-acetate (TPA) and epidermal growth factor (EGF), as well as by a variety of growth-promoting hormones and other cell-stimulatory agents. We will examine the effects of radiation on levels of key components of these pathways: Phosphatidylinositol-4,5-biphosphate, inositol-1,4,5-triphosphate, diacylglycerols, and free cytoplasmic Ca2+, as well as on the activity of the phosphorylating enzyme protein kinase C. These levels/activities will be assayed: 1) at selected times post-irradiation, to determine whether any radiation-induced effects are rapidly produced (as expected from direct membrane perturbations) or are produced at later times (expected if such effects arise from radiation-produced alterations in gene expression); 2) during a radiation-initiated/promotor (TPA, EGF, or the hormone cortisone)-enhanced transformation regiment, to determine whether initiating doses of radiation alter inositol phospholipid-associated pathways known to be activated by selected tumor promoters; and 3) at various post-irradiation times in the presence of large, transformation-suppressing dietary protease inhibitors (the Bowman-Birk inhibitor and the chick-pea inhibitor), which are likely to be membrane-active and whose action in inhibiting specific steps in the series of inositol phospholipid-related membrane-associated pathways could support a role for such step(s) in carcinogenesis. Additionally, we will perform a series of radiation-induced transformation assays in the presence of modulators of levels/activities of specific components (cytoplasmic (Ca2+, protein kinase C) of the pathways studied, to ascertain whether altering the availabiligy of these components affects the ability of cells to undergo radiation-induced or radiation-initiated/promotor-enhanced transformation. Experiments will be performed in an in vitro system utilizing the mouse embryo-derived C3H10T-1/2 cell line used extensively for in vitro transformation research. These studies will provide information about whether there are direct or indirect effects of low-dose radiation on membrane-associated cellular activation processes known to be induced by tumor promotors, as well as elucidate the role of these activation processes in low-dose radiation induced cell transformation as it is promoted by hormonal and other promoting agents and inhibited by dietary protease inhibitors.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA034680-08
Application #
3172446
Study Section
Radiation Study Section (RAD)
Project Start
1988-12-15
Project End
1990-07-31
Budget Start
1989-08-01
Budget End
1990-07-31
Support Year
8
Fiscal Year
1989
Total Cost
Indirect Cost
Name
University of Pennsylvania
Department
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Umans, R S; Kennedy, A R (1992) Effects of activators and inhibitors of protein kinase C on X-ray induced malignant transformation in vitro. Eur J Cancer 28A:732-5
Su, L N; Toscano Jr, W A; Kennedy, A R (1991) Suppression of phorbol ester-enhanced radiation-induced malignancy in vitro by protease inhibitors is independent of protein kinase C. Biochem Biophys Res Commun 176:18-24
Flick, M B; Kennedy, A R (1991) Effect of protease inhibitors on DNA amplification in SV40-transformed Chinese hamster embryo cells. Cancer Lett 56:103-8
Kennedy, A R (1991) Is there a critical target gene for the first step in carcinogenesis? Environ Health Perspect 93:199-203
Radner, B S; Kennedy, A R (1990) Suppression of x-ray induced transformation by Valium and aspirin in mouse C3H10T1/2 cells. Cancer Lett 51:49-57
Kennedy, A R (1989) Relevance of in vitro transformation systems to skin carcinogenesis in vivo. Prog Clin Biol Res 298:103-12
Kennedy, A R; Umans, R S (1988) Effects of glucocorticoid hormones on radiation induced and 12-O-tetradecanoylphorbol-13-acetate enhanced radiation transformation in vitro. Cancer Lett 40:169-75
Umans, R S; Kennedy, A R (1988) Effects of estrogen antagonists on estradiol-enhanced radiation transformation in vitro. Cancer Lett 40:177-83
Billings, P C; St Clair, W; Ryan, C A et al. (1987) Inhibition of radiation-induced transformation of C3H/10T1/2 cells by chymotrypsin inhibitor 1 from potatoes. Carcinogenesis 8:809-12
Umans, R S; Kennedy, A R (1987) Effects of testosterone and dihydrotestosterone on malignant transformation in C3H10T 1/2 cells. Eur J Cancer Clin Oncol 23:339-42

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