Oxidative DNA Damage And Repair In Prostate Cancer

前列腺癌中的氧化 DNA 损伤和修复

• 批准号: 7132274
• 负责人: michele k evans
• 金额: --
• 依托单位: NATIONAL INSTITUTE ON AGING
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7132274
• 关键词: DNA damage; DNA repair; carcinogenesis; cell line; enzyme activity; gas chromatography mass spectrometry; glutathione peroxidase; glutathione transferase; inflammation; liquid chromatography mass spectrometry; mitochondrial DNA; molecular oncology; neoplasm /cancer genetics; oxidative stress; prostate neoplasms; superoxide dismutase; thymine

Mutagenic oxidative DNA base damage increases with age in prostatic tissue. Various factors may influence this increase including: increased production of reactive oxygen species, increased susceptibility to oxidative stress, alterations in detoxifying enzyme levels or defects in DNA repair. Using LC/MS and GC/MS, we show increased levels of oxidative DNA base lesions, 8-hydroxyguanine (8-oxoG), 8-oxoadenine (8-oxoA) and 5-hydroxycytosine (5OHC) over the baseline in PC-3 and DU-145 prostate cancer cells following exposure to ionizing radiation and a repair period. Nuclear extracts from PC-3 and DU-145 prostate cancer cell lines are defective in the incision of 8-oxoG, 5OHC and thymine glycol (TG) relative to the non-malignant prostate cell line. Consistent with reduced expression of OGG1 2a, incision of 8-oxoG is reduced in PC-3 and DU-145 mitochondrial extracts. We also show a correlation between severely defective incision of TG and 5OHC and reduced levels of NTH1 in PC-3 mitochondria. The antioxidant enzymes, glutathione peroxidase (GPx), catalase, and superoxide dismutases (SOD1, SOD2), have altered expression patterns in these cancer cell lines. Genetic analysis of the OGG1 gene reveals that both PC-3 and DU-145 cell lines harbor polymorphisms associated with a higher susceptibility to certain cancers. These data suggest that the malignant phenotype in PC-3 and DU-145 cell lines may be associated with defects in base excision repair (BER) and alterations in expression of antioxidant enzymes. Prostate cancer, is the most prevalent form of cancer among American men and is the second leading cause of their cancer mortality. In the United States, prostate cancer is one of the fastest growing cancers in terms of incidence among American men. While certain factors including: dietary, genetic, lifestyle and environmental are associated with prostate cancer risk, the molecular mechanisms underlying the etiology of the disease are largely unknown. Several genes associated with heritable forms of prostate cancer have been identified and somatic alterations in these genes are presumed to set the stage for the development and/or progression of the disease. To this end, it has been shown that hypermethylation of the -class glutathione S-transferase gene (GSTP1) promoter region inhibits transcription of the gene and is associated with prostate cancer development [4-6]. The GSTP1 gene product probably protects genomic DNA in prostate cells from the deleterious effects of genotoxic agents. Environmental carcinogens such as polycyclic aromatic hydrocarbons may play a role in the etiology of prostate cancer since 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine has been shown to induce prostate cancer in rats. Reactive oxygen species (ROS), most notably the hydroxyl radicals, generated endogenously by cellular metabolism are known to cause oxidative DNA damage that has been implicated in prostate carcinogenesis. Research on the development of prostate cancer suggests that symptomatic and asymptomatic chronic and acute inflammation occurs in the prostate over the life span and acts in synergy with other factors to cause injury to prostatic epithelium. In response to this injury, cellular proliferation occurs followed by oxidative stress related to the ongoing inflammatory process that may in turn result in high rates of oxidative damage to DNA. Furthermore, Bostwick et al. has reported low levels of SOD1, SOD2, and catalase in prostate intraepithelial neoplasia and prostate cancer relative to benign prostate epithelium thereby implicating oxidative DNA damage in prostate carcinogenesis. There is also a significant increase in the proportion of mutagenic oxidatively induced DNA base lesions, 8-hydroxyadenine (8-oxoA), and 8-hydroxyguanine (8-oxoG) in malignant prostatic tissue as well as an increase in the levels of these lesions in benign prostatic tissue with aging. The existence of OGG1 genetic polymorphisms in prostate cancer patients further supports the notion that defective DNA repair may be associated with prostate cancer risk. Taken together these data suggest that reactive oxygen species and oxidative DNA damage may play a critical role in the development of prostate cancer. Oxidative DNA damage has been shown to be higher in the mitochondrial than in the nuclear genome due to the higher metabolic rate in the mitochondria relative to the nucleus. DNA lesions caused by ROS are numerous and include: DNA strand breaks, apurinic/apyrimidinic (AP) sites, modified DNA bases and DNA-protein cross-links. Thymine glycol (TG), 8-oxoG and other DNA base lesions may lead to deleterious biological consequences. TG is a cytotoxic lesion that blocks both DNA replication [21] and transcription [22], causing cell death. On the other hand, 8-oxoG is a pre-mutagenic lesion that results in GC to TA transversions, whereas, 8-oxoA causes both AT to GC transition and AT to CG transversion mutations [24]. Indeed, spontaneous transversion mutations have been observed in proto-oncogenes and the tumor suppressor gene, p53, a commonly mutated gene in cancer that has been shown to play a role in DNA repair. Oxidatively induced mutations in the mtDNA can lead to cellular dysfunction and have been implicated in degenerative diseases, cancer and aging. This damage must be repaired in order to maintain proper genetic integrity. Cells utilize BER pathway as the primary means of minimizing the deleterious effects associated with oxidative DNA damage. In addition to DNA repair, cells express antioxidants that detoxify ROS produced during aerobic respiration. The genome of cancer cells is more prone to oxidative damage due to the high rate of metabolism associated with increased cellular proliferation. This high metabolic rate in cancer cells may result in increased production of ROS that could significantly increase oxidative DNA damage and may be accompanied by alterations in antioxidant levels. It is plausible that increased oxidative DNA damage coupled with alteration in antioxidant levels in cancer cells may result in insufficient DNA repair. Indeed, this is the case in a few cancer cell lines studied showing defective BER in breast cancer cell lines. Recently, defects in DNA mismatch repair (MMR), the pathway that removes errors arising during DNA replication, have been reported in prostate cancer. Although, levels of oxidative DNA damage have been shown to be increased in cancerous cells or tissues relative to non-cancerous cells or tissues, the relationship between elevated oxidative DNA damage and DNA repair in carcinogenesis is still poorly understood. To our knowledge, there have been no reports addressing the repair of oxidatively induced DNA base lesions in prostate cancer cells. Therefore, we hypothesize that oxidative DNA repair may be defective in prostate tissue as a result of uncontrolled oxidative stress and increased oxidative DNA damage. We used two well-studied prostate cancer cell lines, PC-3, DU-145 and a non-malignant prostate cell line, RWPE-1 to address our hypothesis.

致突变性氧化DNA碱基损伤随着前列腺组织年龄的增长而增加。各种因素可能影响这种增加，包括：活性氧的产生增加，对氧化应激的易感性增加，解毒酶水平的改变或DNA修复的缺陷。通过LC/MS和GC/MS，我们发现PC-3和DU-145前列腺癌细胞的氧化DNA碱基病变、8-羟基鸟嘌呤（8-oxoG）、8-氧腺嘌呤（8-oxoA）和5-羟基胞嘧啶（5OHC）水平在暴露于电离辐射和修复期后高于基线水平。PC-3和DU-145前列腺癌细胞的核提取物在8-oxoG、5OHC和胸腺嘧啶乙二醇（TG）的切口上相对于非恶性前列腺细胞株存在缺陷。与OGG1 2a表达减少一致，PC-3和DU-145线粒体提取物中8-oxoG的切口减少。我们还发现TG和5OHC切口严重缺陷与PC-3线粒体中NTH1水平降低之间存在相关性。抗氧化酶，谷胱甘肽过氧化物酶（GPx），过氧化氢酶和超氧化物歧化酶（SOD1, SOD2）在这些癌细胞系中改变了表达模式。OGG1基因的遗传分析显示，PC-3和DU-145细胞系都存在与某些癌症的高易感性相关的多态性。这些数据提示PC-3和DU-145细胞系的恶性表型可能与碱基切除修复（BER）缺陷和抗氧化酶表达改变有关。

项目成果

Loss of functional prion protein: A role in prion disorders?

• DOI: 10.1016/s1074-5521(96)90128-3
• 发表时间: 1996-08-01
• 期刊: CHEMISTRY & BIOLOGY
• 作者: Borchelt, DR;Sisodia, SS
• 通讯作者: Sisodia, SS