MOLECULAR MECHANISM OF SUPPRESSION OF NEOPLASTIC TRANSFORMATION BY LOW DOSES OF LOW LET RADIATION
We are currently funded (9/01-8/04) by the DOE Low Dose Radiation Research Program to examine mechanisms underlying the suppression of neoplastic transformation in vitro by low doses of low LET radiation. For the new studies proposed under Notice 04-21, we intend to follow up on our observation that upregulation of DNA repair may be an important factor and that its importance is dose-dependent. The experimental system will be the human hybrid cell neoplastic transformation assay that we are currently using. We propose to test the following hypothesis: Down-regulation of DNA dsb repair will abrogate the low dose suppression of neoplastic transformation. Using the technique of RNA silencing, it is proposed to test the effect of down-regulation of the two major DNA dsb repair pathways, homologous recombination (HR) and non-homologous end-joining (NHEJ), on the dose response relationship for neoplastic transformation. Based on prior studies, we predict that this will result in abrogation of the suppressive effect at doses in the range 1 to 10 cGy, but not at lower doses. The proposed experiments will also help address the question as to which of the two DNA repair pathways may be the most important in causing suppression of transformation. HR is a pathway that is predominant in S and G2 phase cells and is known to be less error-prone than the NHEJ pathway that is predominant in G1 phase. We hypothesize that down-regulation of HR will result in the most effective abrogation of suppression. An important component of this study will be the determination of the how abrogation of DNA dsb repair impacts the spontaneous transformation frequency, presumably a consequence of endogeneous DNA damage. Experiments will be carried out using partially synchronized populations of cells enriched for G1 and S/G2 respectively. In addition to the endpoint of neoplastic transformation the impact of down-regulation of HR and NHEJ on the formation and disappearance of the DNA dsb marker, gamma-H2AX, will be studied.
- Research Organization:
- Univ. of California, Irvine, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC)
- DOE Contract Number:
- FG02-05ER64083
- OSTI ID:
- 1010270
- Report Number(s):
- FG02-05ER64083
- Country of Publication:
- United States
- Language:
- English
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