Carcinogenic Interactions of Radiation and Chemicals

描述(申请人提供)：我们以前在敏感的BALB/cByJ小鼠和耐药的C57BL/6ByJ小鼠之间证明了辐射诱发乳腺癌的敏感性和辐射诱导的细胞遗传不稳定性的品系差异，并提供了这种敏感性差异是可遗传的特征的证据。对这些菌株的DNA序列分析表明，BALB/c小鼠存在两个独有的多态性。对这两个菌株、F1杂交种和回交动物的研究表明，对辐射诱导的细胞遗传不稳定性的敏感性与编码DNA依赖蛋白激酶催化亚单位(DNA PKcs)的Prkdc基因显著相关。BALB/c Prkdc等位基因纯合的小鼠(Prkdc BALB/c)在辐射后双链断裂修复方面也存在缺陷，表现出激酶活性降低，Western分析显示DNA-PKcs的信号强度降低。由于修复缺陷、Western信号强度降低、激酶活性降低以及这两个基因多态性的存在都与辐射诱导的细胞遗传学不稳定的易感性显著相关，我们现在建议研究该基因座与辐射诱导的乳腺癌易感性之间的遗传联系，并更直接地阐明Prkdc BALB/c在辐射诱导的不稳定和乳腺癌中的作用。我们现在还证明了来自BALB/c和SCID的乳腺细胞的辐射导致了端粒之间的融合和辐射诱导的双链断裂(DSB)，这可能是由于DNA PKcs作为端粒维持的重要元件的功能缺陷所致。具体地说，该项目的目的是：1)直接确定PrkdcBALB基因多态性的功能后果；2)确定Prkdc BALB基因在辐射诱导的乳腺癌易感性中的作用；3)确定端粒功能障碍在辐射诱导的细胞遗传学不稳定和乳腺癌中的作用。

DESCRIPTION (provided by applicant): We previously demonstrated strain differences in susceptibility to radiation-induced mammary cancer and radiation-induced cytogenetic instability between sensitive BALB/cByJ, and resistant C57BL/6ByJ mice and provided evidence that such susceptibility differences were heritable traits. Sequence analysis of cDNA from these strains indicates two polymorphisms unique to the BALB/c mouse. Studies in the two strains, F1 hybrids, and in backcross animals have demonstrated a significant association between susceptibility to radiation-induced cytogenetic instability and Prkdc, the gene encoding the catalytic subunit of DNA dependent protein kinase (DNA PKcs). Mice homozygous for the BALB/c Prkdc allele (Prkdc BALB/c) are also deficient in the post-irradiation repair of double strand breaks, showed a reduced kinase activity, and western analyses showed a reduced intensity of signal for DNA-PKcs. Since the repair deficiency, reduced western signal intensity, reduced kinase activity, and the presence of these two polymorphisms are all significantly associated with increased susceptibility to radiation-induced cytogenetic instability, we now propose to examine the genetic linkage between this locus and susceptibility to radiation-induced mammary cancer, and to more directly elucidate the role of Prkdc BALB/c in radiation-induced instability and mammary cancer. We have now also demonstrated that irradiation of mammary cells from BALB/c as well as SCID, which have a truncating mutation of Prkdc, results in fusions between telomeres and radiation-induced double strand breaks (DSB) presumably as a result of a defect in the function of DNA PKcs as an important element in telomere maintenance. Specifically, the aims of this project are to: 1) directly determine the functional consequence of polymorphorisms in PrkdcBALB; 2) determine the role of Prkdc BALB in susceptibility to radiation-induced mammary cancer; 3) determine the contribution of telomere dysfunction in radiation-induced cytogenetic instability and mammary cancer.