Mitochondrial DNA and Prostate Cancer in African American

描述（由申请人提供）：线粒体在细胞增殖、细胞信号传导和细胞凋亡中起核心作用。线粒体含有自己的DNA （mtDNA）。mtDNA是人类起源和种族的决定因素。人类mtDNA是一个非常小的基因组（16569 bp）。线粒体基因组的整个蛋白质编码能力专门用于生产13个蛋白质亚基。这13种蛋白质组成了不同的亚基，组成了四种氧化磷酸化（OXPHOS）复合物，对能量（ATP）的产生和其他线粒体功能至关重要。非裔美国男性（AAM）的前列腺癌发病率最高，在早期就发展为前列腺癌，在诊断时呈现更高的肿瘤分级，并且具有比白人美国男性（CAM）更高的转移率和死亡率。前列腺癌种族差异背后的遗传机制尚不清楚。我们的研究表明，AAM中mtDNA含量的降低在前列腺癌发生中起重要作用。我们测量了从AAM和CAM获得的白细胞（WBC）和前列腺肿瘤的mtDNA拷贝数。我们的初步研究表明，AAM和CAM的白细胞中含有相似数量的mtDNA（拷贝数）。然而，当调整年龄、Gleason分级和PSA（前列腺特异性抗原）时，AAM前列腺肿瘤的mtDNA含量比CAM肿瘤少60倍。我们的初步数据表明，编码线粒体DNA聚合酶γ (POLG1)的核基因突变诱导mtDNA的耗竭，并增加体外癌细胞的致瘤潜力。这些研究表明mtDNA稳态在癌变过程中起重要作用。基于这些观察，我们假设mtDNA含量降低通过显著改变线粒体OXPHOS在AAM前列腺肿瘤发生中起关键作用。目的1：确定AAM前列腺肿瘤POLG1突变谱与CAM前列腺肿瘤POLG1突变谱是否存在差异。鉴定AAM原发性前列腺肿瘤中POLG1基因的独特突变，并确定其在mtDNA缺失、OXPHOS活性和细胞凋亡中的功能意义。目的2：在体外和小鼠异种移植模型中确定突变体POLG1诱导mtDNA缺失对前列腺肿瘤发生的影响。提出的前列腺细胞mtDNA缺失的发展具有显著的潜力，以提高我们对非裔美国人前列腺肿瘤发生的理解。该提案解决了PAR-09-160在癌症健康差异的基础癌症研究中请求探索性资助的两个关键目标（R21）。这些目标包括：1)开发“旨在研究癌症差异的新细胞培养模型/系统”；2)探索由于mtDNA含量的“遗传差异”，非裔美国男性对前列腺癌的易感性。

DESCRIPTION (provided by applicant): Mitochondria play a central role in cell proliferation, cell signaling and apoptosis. Mitochondria contain their own DNA (mtDNA). mtDNA serves as a determinant of human origin and ethnicity. Human mtDNA is a very small (16,569 bp) genome. The entire protein coding capacity of the mitochondrial genome is dedicated to the production of 13 protein subunits. These 13 proteins constitute various subunits that make up four oxidative phosphorylation (OXPHOS) complexes essential for energy (ATP) production and other mitochondrial function. African-American men (AAM) have the highest rate of prostate cancer, develop prostate cancer at an early age, present with a higher tumor grade at time of diagnosis, and have a higher rate of metastasis and mortality than Caucasian American men (CAM). The genetic mechanism(s) underlying this racial diversity in prostate cancer is not well understood. Our studies demonstrate that in AAM reduced mtDNA content plays an important role in prostate carcinogenesis. We measured the mtDNA copy number in white blood cells (WBC) and prostate tumor obtained from AAM and CAM. Our preliminary studies suggest that WBC of both AAM and CAM contained similar amount of mtDNA (copy number). However, when adjusted for age, Gleason grade and PSA (prostate specific antigen) the prostate tumors of AAM contained >6 times less mtDNA than CAM tumors. Our preliminary data suggest that mutations in nuclear gene encoding mitochondrial DNA polymerase gamma (POLG1) induce depletion of mtDNA and increase tumorigenic potential of cancer cells in vitro. These studies suggest that mtDNA homeostasis must play an important role in carcinogenesis. Based on these observations we hypothesize that reduced mtDNA content plays a critical role in prostate tumorigenesis in AAM by significantly altering the mitochondrial OXPHOS. AIM 1: Determine whether mutational spectrum of POLG1 in AAM prostate tumors differs from POLG1 mutational spectrum of CAM. Identify distinctive mutations in POLG1 gene in primary prostate tumors of AAM and determine its functional significance on mtDNA depletion, OXPHOS activity and apoptosis. AIM 2: Determine the consequences of mutant POLG1 induced depletion of mtDNA on prostate tumorigenesis in vitro and in mouse xenograft model. The proposed development of mtDNA depletion in prostate cells has the significant potential to enhance our understanding of prostate tumorigenesis in the African American population. This proposal addresses the two key objectives of the PAR-09-160 requesting exploratory grants in basic cancer research in cancer health disparities (R21). These objectives include: 1) the development of "new cell culture models/systems designed to investigate cancer disparities" and 2) explores the susceptibility to prostate cancer in African-American men due to "genetic differences" in mtDNA content.