Particulate Cr(VI) Toxicology in Human Lung Epithelial Cells and Fibroblasts

项目摘要 肺癌仍然是美国癌症死亡的主要原因。 是为了更好地了解其原因。六价铬[Cr（VI）]是一种主要的人类肺癌致癌物 由于在工作场所和一般环境中暴露于它是很常见的，因此对健康的关注。我们的研究 重点研究Cr（VI）诱导的致癌机制，这是目前未知的。在 特别是，这项工作的重点是颗粒状Cr（VI）化合物，因为它们是最有效的Cr（VI） 致癌物质。最近的研究表明，颗粒铬（VI）诱导染色体不稳定性，并导致细胞 逃避DNA双链断裂修复，这是人类肺癌的标志。因此，本研究重点 颗粒状Cr（VI）如何诱导细胞逃避DNA双链断裂修复，导致染色体 不稳定性和致癌作用。我们的数据显示，长期暴露于颗粒状Cr（VI）会特别影响 同源重组效应臂（HR修复），破坏RAD 51核蛋白丝形成，丢失 其中之一会导致染色体不稳定。因此，本研究的目标是描述这种影响， HR修复和潜在的变化，以了解所涉及的机制。我们的假设是： 颗粒Cr（VI）破坏了RAD 51核蛋白丝形成失活的潜在机制 Cr（VI）诱导的DNA断裂的HR修复导致CIN和肿瘤转化。我们将测试这个 通过三个相互关联的具体目标的假设。目标1将确定Cr（VI）如何影响BRCA 2，DSS 1， RAD 51 B、RAD 51 C、RAD 51 D、RPA和XRCC 2破坏人RAD 51核蛋白丝形成 肺细胞目的2确定在哺乳动物中破坏的RAD 51丝形成的持续性和细胞遗传性。 用Cr（VI）致瘤转化的人肺细胞，和BRCA 2，DSS 1，RAD 51 B， 来自人Cr（VI）工作者的肺肿瘤中的RAD 51 C、RAD 51 D、RPA和XRCC 2。目标3确定影响 Cr（VI）对肺中BRCA 2、DSS 1、RAD 51 B、RAD 51 C、RAD 51 D、RPA和XRCC 2蛋白水平的影响， 暴露于Cr（VI）的动物的肺肿瘤。结果将导致第一次报告的详细资料， Cr（VI）与HR修复效应臂在细胞和分子水平上的相互作用， 这些方面的特点在肿瘤的结果，包括肿瘤铬（VI）暴露的工人。 结果还将显示哪些变化是短暂的，取决于暴露，哪些变化在细胞中持续存在 逃避细胞死亡并发展为肿瘤的结果。这项研究意义重大，因为它提供了：1） 了解Cr（VI）的致癌机制; 2）更好地评估暴露风险的基本信息 3）进一步研究铬（VI），其他金属和肺癌的一般机制的方法。

PROJECT SUMMARY Lung cancer continues to be the leading cause of cancer death in the U.S. One of the key strategies to combating it is to better understand its causes. Hexavalent chromium [Cr(VI)] is a human lung carcinogen of major public health concern because exposure to it is common in the workplace and in the general environment. Our study focuses on investigating the mechanisms of Cr(VI)-induced carcinogenesis, which are currently unknown. In particular, this work focuses on the particulate Cr(VI) compounds, because they are the most potent Cr(VI) carcinogens. Recent studies indicate particulate Cr(VI) induces chromosome instability and causes cells to evade DNA double strand break repair, which are hallmarks of human lung cancer. Thus, this research focuses on how particulate Cr(VI) induces cells to evade DNA double strand break repair leading to chromosome instability and carcinogenesis. Our data show prolonged exposure to particulate Cr(VI) specifically impacts the effector arm of homologous recombination (HR repair), disrupting RAD51 nucleoprotein filament formation, loss of which can cause chromosome instability. Therefore, the goal of this research is to characterize this impact on HR repair and the underlying changes in order to understand the mechanisms involved. Our hypothesis is: particulate Cr(VI) disrupts the underlying mechanisms of RAD51 nucleoprotein filament formation inactivating HR repair of Cr(VI)-induced DNA breaks resulting in CIN and neoplastic transformation. We will test this hypothesis through three interrelated specific aims. Aim 1 will determine how Cr(VI) impacts BRCA2, DSS1, RAD51B, RAD51C, RAD51D, RPA, and XRCC2 to disrupt RAD51 nucleoprotein filament formation in human lung cells. Aim 2 determines the persistence and cellular heritability of disrupted RAD51 filament formation in human lung cells neoplastically transformed by Cr(VI), and the protein levels of BRCA2, DSS1, RAD51B, RAD51C, RAD51D, RPA, and XRCC2 in lung tumors from human Cr(VI) workers. Aim 3 determines the impact of Cr(VI) on protein levels of BRCA2, DSS1, RAD51B, RAD51C, RAD51D, RPA, and XRCC2 in the lungs and lung tumors of Cr(VI)-exposed animals. Results will lead to the first reports of detailed information of the interactions of Cr(VI) with the effector arm of HR repair at a cellular and molecular level and the first characterizations of these aspects in neoplastic outcomes including tumors from Cr(VI)-exposed workers. Results will also show which changes are transient and depend on exposure and which changes persist in cells that escape cell death and progress to neoplastic outcomes. This research is significant because it provides: 1) An understanding of Cr(VI)’s carcinogenic mechanism; 2) Essential information to better assess exposure risk to particulates; and 3) A mechanistic approach for further study of Cr(VI), other metals and lung cancer in general.