||5R03CA096431-02 Interpret this number
||Colorado State University
||DNA Double Strand Break Repair in Tobacco Carcinogenesis
DESCRIPTION (provided by applicant):
Despite strong epidemiological data associating tobacco smoke to lung cancer,
the mechanism of carcinogenesis by tobacco chemicals is not well understood.
Among those exposed to tobacco smoke, only a certain portion develop lung
cancer suggesting the involvement of genetic factor(s) in the susceptible
population. A difference in DNA repair ability has been suggested for the
explanation of the susceptibility. Of the various DNA repair pathways, a
relationship between nucleotide excision repair and tobacco carcinogens (e.g.
benzo[a]pyrene) has been well documented. However, DNA double strand break
(DSB) repair, another important repair pathway, has rarely been studied with
tobacco chemicals in mammalian systems. Since a recent study revealed a
positive association between lung cancer and the reduced activity of a protein
involved in DNA DSB repair, this application is initiated to confirm and
extend the study on the role of DNA DSB repair in tobacco carcinogenesis. DNA
DSB is the most destructive form of DNA damage and can lead to cell death,
mutation and transformation if not repaired or mis-repaired. An efficient way
to study the role of DNA DSB repair is to use DNA DSB repair deficient mutant
cell lines exposed to tobacco chemicals. Specific Aim 1 addresses: Various
rodent and human DNA DSB repair deficient cell lines will be treated with
several tobacco carcinogens and cigarette smoke condensate (CSC), and
comparisons will be made to wild type cells with regard to cell survival and
mutation frequency. This is to test the hypothesis "Mammalian cells utilize
DNA DSB repair mechanism or protein(s) associated with DNA DSB repair in the
recovery process of DNA damage induced by tobacco carcinogens". Further
molecular studies are suggested based on the cell line studies. These studies
have the potential to identify a new tobacco sensitive sub-population. The
experiments in Specific Aim 2 are proposed based on our recent finding that
lung cancer sensitive BALB/c mice showed a mild DNA DSB repair defect.
Specific Aim 2 puts forward the studies on the cell viability, DNA DSB
formation and chromosome rearrangements in alveolar macrophage (AM),
lymphocytes and lung epithelial cells from BALB/c and C57BL/6 (control) mice
exposed to tobacco carcinogens. Two hypotheses will be tested in this aim: (1)
Cells from BALB/c mice show a higher level of chromosome misrejoining which is
detected by a sensitive premature chromosome condensation (PCC) assay in
interphase chromosomes combined with/without fluorescence in situ
hybridization (FISH)." (2) There is a good correlation between the sensitivity
data with lymphocytes and those with AM and/or lung epithelial cells. The
proposed experiments not only provide new mechanistic insight on the initial
step for tobacco carcinogenesis, but also help furnish sensitive diagnostic
tools to identify lung cancer susceptible individuals.
Cytotoxicity of cigarette smoke condensate is not due to DNA double strand breaks: Comparative studies using radiosensitive mutant and wild-type CHO cells.
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DNA repair, 2003-03-01; 2(3), p. 309-14.