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（16，569 bp）。线粒体基因组的整个蛋白质编码能力致力于产生13个蛋白质亚基。这13种蛋白质构成了各种亚基，这些亚基构成了能量（ATP）产生和其他线粒体功能所必需的四种氧化磷酸化（OXPHOS）复合物。非洲裔美国人（AAM）的前列腺癌发病率最高，在早期患上前列腺癌，在诊断时肿瘤分级较高，转移率和死亡率高于白人美国人（CAM）。前列腺癌中这种种族多样性的遗传机制尚未得到很好的理解。我们的研究表明，在AAM减少线粒体DNA含量在前列腺癌的发生中起着重要的作用。我们测定了AAM和CAM中白色血细胞（WBC）和前列腺肿瘤中mtDNA的拷贝数。我们的初步研究表明，AAM和CAM的WBC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的前列腺肿瘤含有比CAM肿瘤少>6倍的mtDNA。我们的初步数据表明，在核基因编码线粒体DNA聚合酶γ（POLG 1）的突变诱导线粒体DNA的消耗，并在体外增加癌细胞的致瘤潜力。这些研究表明，线粒体DNA的稳态必须发挥重要作用，在癌症的发生。基于这些观察结果，我们推测线粒体DNA含量减少在AAM的前列腺肿瘤发生中起着关键作用，通过显著改变线粒体OXPHOS。目的1：确定AAM前列腺肿瘤中POLG 1突变谱与CAM中POLG 1突变谱是否不同。鉴定AAM原发性前列腺肿瘤中POLG 1基因的独特突变，并确定其对mtDNA耗竭、OXPHOS活性和细胞凋亡的功能意义。目的2：研究突变型POLG 1诱导线粒体DNA缺失对体外和小鼠前列腺肿瘤发生的影响。前列腺细胞线粒体DNA缺失的研究对于提高我们对非裔美国人前列腺肿瘤发生的认识具有重要的意义。该提案解决了PAR-09-160的两个关键目标，要求在癌症健康差异（R21）的基础癌症研究中提供探索性赠款。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）探索非裔美国人因mtDNA含量的“遗传差异”而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.