The long term goal of this research program is to gain knowledge concerning the mechanisms involved in the response of mammalian cells to radiation, with particular reference to its carcinogenic and mutagenic effects. The approach is a multi- faceted one, and the endpoints under investigation include mutagenesis, malignant transformation, cell survival and the induction of chromosomal abnormalities. The program has a dual purpose: first, to better define the risks of low-level radiation exposure by examining the role of factors such as total dose, dose-rate, LET and the intracellular distribution of dose on mutagenesis and transformation; and second, to learn more about the cellular and molecular mechanisms for these effects.
The specific aims are: 1) To identify oncogenes activated during the process of malignant transformation by radiation. Transfection of DNA into NIH 3T3 cells will be carried out at regular intervals after irradiation of 10T1/2 cell cultures; DNA from primary and secondary transfectants will be examined by Southern blotting and reactivity to specific monoclonal antibodies. 2) To examine the direct mutagenic effects of various types of ionizing radiation on the c-Ha-ras proto-oncogene by transfection of the irradiated gene in a plasmid vector. 3) To examine factors involved in the morphological transformation and immortalization of human diploid fibroblasts. A particular focus will be on the study of a DNA fragment derived from the second intron of c-myc which induces specific morphologic alterations in a strain of partially transformed cells. We propose to identify this presumptive regulatory element by deletion analysis and sequencing, and furthur study its role in transformation. 4) To analyze the molecular structure of spontaneous and induced mutations at the autosomal tk locus in the TK6 human cell line. Appropriate probes will be obtained and restriction fragment or sequence polymorphic markers sought. Molecular biological techniques will be employed in order to determine whether the large-scale changes we have observed involve gene conversion, mitotic recombination or multi-locus deletion events and to estimate their extent. 5) To carry out cytogenetic analysis of mutant clones in order to determine whether large scale DNA structural changes are associated with visible chromosomal abnormalities. Results will be correlated with those of dosage blots. 6) To analyse the spectrum of molecular structural changes induced by different types of radiation including fast neutrons, heavy ions and Auger emitting radionuclides. 7) To continue studies of the relative biological effectiveness for transformation and mutagenesis of low dose, low dose-rate neutron exposure. 8) To investigate the role of microdistribution of dose of high LET radiation within the cell on its biologic effects by use of Auger electron emitting radionuclides. Emphasis will be on mutagenesis in human TK6 cells.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Unknown (R35)
Project #
5R35CA047542-04
Application #
3479703
Study Section
Special Emphasis Panel (SRC (88))
Project Start
1988-04-15
Project End
1995-03-31
Budget Start
1991-04-01
Budget End
1992-03-31
Support Year
4
Fiscal Year
1991
Total Cost
Indirect Cost
Name
Harvard University
Department
Type
Schools of Public Health
DUNS #
082359691
City
Boston
State
MA
Country
United States
Zip Code
02115
Little, J B (2007) [Nontargeted effects of ionizing radiation: implications for low-dose exposures] Radiats Biol Radioecol 47:262-72
Little, John B (2006) Lauriston S. Taylor lecture: nontargeted effects of radiation: implications for low-dose exposures. Health Phys 91:416-26
Mamon, H J; Dahlberg, W; Azzam, E I et al. (2003) Differing effects of breast cancer 1, early onset (BRCA1) and ataxia-telangiectasia mutated (ATM) mutations on cellular responses to ionizing radiation. Int J Radiat Biol 79:817-29
Azzam, Edouard I; Nagasawa, Hatsumi; Yu, Yongjia et al. (2002) Cell cycle deregulation and xeroderma pigmentosum group C cell transformation. J Invest Dermatol 119:1350-4
Fitzek, Markus M; Dahlberg, William K; Nagasawa, Hatsumi et al. (2002) Unexpected sensitivity to radiation of fibroblasts from unaffected parents of children with hereditary retinoblastoma. Int J Cancer 99:764-8
Little, John B; Nagasawa, Hatsumi; Dahlberg, William K et al. (2002) Differing responses of Nijmegen breakage syndrome and ataxia telangiectasia cells to ionizing radiation. Radiat Res 158:319-26
Romney, C A; Paulauskis, J D; Nagasawa, H et al. (2001) Multiple manifestations of X-ray-induced genomic instability in Chinese hamster ovary (CHO) cells. Mol Carcinog 32:118-27
Syljuasen, R G; Krolewski, B; Little, J B (2001) Molecular events in radiation transformation. Radiat Res 155:215-221
Romney, C A; Paulauskis, J D; Little, J B (2001) X-ray induction of microsatellite instability at autosomal loci in human lymphoblastoid WTK1 cells. Mutat Res 478:97-106
Krolewski, B; Little, J B (2000) Overexpression of p21 protein in radiation-transformed mouse 10T(1/2) cell clones. Mol Carcinog 27:141-8

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