DNA修复基因XRCC1在胃癌中的表达及意义

目的探讨DNA修复基因XRCC1在胃癌中的表达及意义。方法用免疫组化方法检测胃癌组织、远癌组织及肠上皮化生组织中XRCC1的蛋白表达。结果 3组XRCC1在胃癌组织中的表达水平间,差异均有统计学意义(P<0.05)。结论 XRCC1在胃癌组织中表达异常,提示其在胃癌发生过程中可能起重要作用。     

枸杞对DNA损伤后修复作用的研究

寻找天然抗致癌的物质对人类肿瘤的预防作用早已引起人们的重视。枸杞是我国传统中药。既是食品，又是药品，久服可坚筋骨，轻身不老，而耐寒暑。现代医学研究发现，枸杞具抗衰延寿，提高免疫功能，抑制癌细胞生长等作用。以小鼠骨髓细胞染色体畸变率为指标，进一步探讨枸...     

干扰survivin表达减少肿瘤细胞对紫外线诱导DNA损伤的修复作用

目的：研究生存素（survivin）对紫外线（UV）诱导的肿瘤细胞DNA损伤修复作用及其机制。方法：本研究构建和包装survivin蛋白shRNA慢病毒载体;依据逐孔稀释法确定转染效率及滴度;以实时荧光定量法确定干扰效果;采用宿主细胞复活法（HCR）检测survivin蛋白表达对细胞整体DNA损伤修复能力的影响。结果：干扰survivin的表达显著降低肺腺癌H1299细胞对UV诱导DNA损伤的修复能力。结论：Survivin在UV诱导DNA损伤的修复作用中扮演重要角色。本研究可以为以survivin为靶点的肿瘤治疗提供一定的理论依据。     

聚腺苷二磷酸核糖聚合酶-1、DNA损伤修复与疾病

聚腺苷二磷酸核糖聚合酶-1是存在于多数真核细胞中的一个蛋白质翻译后修饰酶，在受损DNA链断裂后的修复及其续发反应中所起作用越来越受到重视。细胞DNA因环境不良因素的作用损伤后，PARP-1可能作为细胞DNA损伤的分子感受器，识别、结合到DNA断裂处，并被激活，催化受体蛋白的聚腺苷二磷     

二种DNA损伤剂诱发SCE及其修复特性的研究

研究结果表明,多功能烷化剂MMC所引起的DNA初级损伤的SCE诱发能力显著低于次级损伤,但CCNU所引起的初级损伤与次级损伤的SCE诱发能力无显著差异。5-溴脱氧尿嘧啶核苷渗入DNA后,对DNA上初级损伤修复不利。     

二氯胺基酚对 V79 细胞 DNA 损伤效应的研究

我们采用单细胞凝胶电泳新技术和ＳＣＥ试验研究了８３－１除草剂的主要代谢产物２，４－二氯－６－胺基酚（ＤＣＡＰ）对Ｖ７９细胞的ＤＮＡ损伤作用。结果表明，ＤＣＡＰ浓度≥５０μｇ／ｍｌ时，细胞出现明显的ＤＮＡ迁移和姐妹染色单体交换（Ｐ＜０．０１），说明ＤＣＡＰ是ＤＮＡ损伤剂。结合前期研究结果推断，６位硝基还原成胺基是该除草剂在体内活化致癌的基本途径。结果还表明，单细胞凝胶电泳比ＳＣＥ试验更灵敏，可能是研究环境低剂量暴露的遗传危害最有效的手段。     

黄芪多糖调控细胞DNA损伤修复发挥抗非小细胞肺癌活性的机制研究

目的 探讨黄芪多糖通过DNA损伤修复发挥抗非小细胞肺癌（NSCLC）活性的作用及机制。方法 通过ip氨基甲酸酯（0.8 mg/g）建立NSCLC小鼠模型,观察肺组织表面结节的数量及形态在体评价黄芪多糖（300 mg/kg）的抗肿瘤活性;CCK8法评价黄芪多糖体外抗人NSCLC细胞系A549（40.00、20.00、10.00、5.00、2.50、1.25 μmol/L）和HCC827（100、50、25 μmol/L）增殖活性;并通过单细胞凝胶电泳测定（彗星试验）评价黄芪多糖对A549（40 μmol/L）和HCC827（50 μmol/L）细胞DNA损伤的影响;通过实时荧光定量PCR（RT-qPCR）、Western blotting、RNA干扰、免疫荧光染色实验研究黄芪多糖对VRK1/P53BP1信号通路的作用。结果 与模型组小鼠比较,黄芪多糖和吉非替尼（阳性药）组的结节数目显著减少（P<0.05、0.01）;黄芪多糖组的肿瘤结节呈近似圆形,与紧密排列的肿瘤结节边界清晰,模型和吉非替尼组的结节呈现不规则结构,细胞排列松散,更具侵略性。黄芪多糖呈剂量相关性地抑制A549和HCC827细胞增殖,显著缩短的彗尾和橄榄炬（P<0.05、0.001）,保护DNA完整性;显著增加NSCLC细胞中VRK1 mRNA和蛋白表达水平（P<0.05、0.01）,同时免疫荧光分析发现P53BP1和VRK1蛋白表达水平升高,且VRK1蛋白可在细胞核和细胞质之间移位;通过VRK1敲低反向验证上述结果。结论 黄芪多糖通过激活VRK1/P53BP1信号转导途径增强DNA损伤修复,进而抑制NSCLC细胞增殖。     

非同源末端连接修复相关因子对DNA损伤修复调控及肿瘤治疗作用的研究进展

细胞在内源性或外源性因子的胁迫作用下会产生各种损伤,包括遗传物质DNA的双链断裂(DSB)。非同源末端连接(NHEJ)是哺乳动物细胞中DSB损伤修复的一种主要机制。NHEJ过程中一些主要因子如DNA依赖性蛋白激酶、DNA交联修复蛋白1C、X射线修复交叉互补蛋白4/DNA连接酶Ⅳ和X射线修复交叉互补蛋白4类似因子对DNA损伤修复(DDR)具有重要的调控作用,其中任何一种因子的改变都会影响DDR的效率。此外,NHEJ相关因子与肿瘤发生息息相关。本文针对NHEJ相关因子调控DSB修复方面的研究作一简要综述,并对NHEJ修复相关因子在肿瘤治疗中的研究进行总结。     

Modulation of oxidative DNA damage by repair enzymes XRCC1 and hOGG1

The influence of DNA repair gene polymorphisms (XRCC1: Arg194Trp, Arg280His, Arg399Gln; APE1: Asp148Glu; hOGG1: Ser326Cys) on oxidative DNA damage is controversial and was investigated in 214 German workers with occupational exposure to vapors and aerosols of bitumen,compared to 87 German construction workers without exposure, who were part of the Human Bitumen Study. Genotypes were determined by real-time polymerase chain reaction (PCR), and actual smoking habits by a questionnaire and cotinine analysis. Oxidative DNA damage in white blood cells (WBC) collected pre- and postshift was measured as 8-oxodGuo adducts/10(6) dGuo by a hjigh-performance liquid chromatography electron capture detection (HPLC-ECD) method, followed by calculation of the difference between post- and preshift values (Δ8-oxodGuo/10(6) dGuo). The 214 bitumen exposed workers showed higher median Δ8-oxodGuo values than the 87 references. In the whole study group (n=301) there was a trend for increasing adduct values for XRCC1 Arg(GG)399Gln(AA) during a shift, especially in nonsmokers (n=108. Referents (n=87) displayed a similar trend for hOGG1 Ser(CC)326Cys(GG). In contrast, XRCC1 Arg(GG)280His(AA) showed a decrease of median Δ8-oxodGuo/10(6) dGuo values in workers with exposure to vapors and aerosols of bitumen (n=214), especially in smokers (n=145). XRCC1 Arg194Trp and APE1 Asp148Glu displayed no marked association with Δ8-oxodGuo levels. Data indicate that the combination of different variants in DNA damage repair enzymes may modulate the production of 8-oxoguanine adducts in WBC produced by xenobiotics during a shift.     

Human DNA glycosylases involved in the repair of oxidatively damaged DNA

Reactive oxygen species from endogenous and environmental sources induce oxidative damage to DNA, and hence pose an enormous threat to the genetic integrity of cells. Such oxidative DNA damage is restored by the base excision repair (BER) pathway that is conserved from bacteria to humans and is initiated by DNA glycosylases, which simply remove the aberrant base from the DNA backbone by hydrolyzing the N-glycosidic bond (monofunctional DNA glycosylase), or further catalyze the incision of a resulting abasic site (bifunctional DNA glycosylase). In human cells, oxidative pyrimidine lesions are generally removed by hNTH1, hNEIL1, or hNEIL2, whereas oxidative purine lesions are removed by hOGG1. hSMUG1 excises a subset of oxidative base damage that is poorly recognized by the above enzymes. Unlike these enzymes, hMYH removes intact A misincorporated opposite template 8-oxoguanine during DNA replication. Although hNTH1, hOGG1, and hMYH account for major cellular glycosylase activity for inherent substrate lesions, mouse models deficient in the enzymes exhibit no overt phenotypes such as the development of cancer, implying backup mechanisms. Contrary to the mouse model, hMYH mutations have been shown to lead to a multiple colorectal adenoma syndrome and high colorectal cancer risk. For cleavage of the N-glycosidic bond, bifunctional DNA glycosylases (hNTH1, hNEIL1, hNEIL2, and hOGG1) use Lys or Pro for direct attack on sugar C1', whereas monofunctional DNA glycosylases (hSMUG1 and hMYH) use an activated water molecule. DNA glycosylases for oxidative damage, if not all, are covalently trapped by DNA containing 2-deoxyribonolactone or oxanine. Thus, the depletion of functional DNA glycosylases using covalent trapping may reduce the BER capacity of cancer cells, hence potentiating the efficacy of anticancer drugs or radiation therapy.     

Increase the cisplatin cytotoxicity and cisplatin-induced DNA damage in HepG2 cells by XRCC1 abrogation related mechanisms

Cisplatin is one of the most potent chemotherapeutic anticancer drugs for the treatment of various cancers. The cytotoxic action of the drug is often thought to be associated with its ability to bind DNA to form cisplatin–DNA adducts. Impaired DNA repair processes including base excision repair (BER) play important roles on its cytotoxicity. XRCC1 is a key protein known to play a central role at an early stage in the BER pathway. However, whether XRCC1 contributes to decrease the cisplatin cytotoxicity and cisplatin-induced DNA damage in HepG2 still remains unknown. Hence, the purpose of this study was to explore whether abrogation of XRCC1 gene expression by short hairpin RNAs (shRNA) could reduce DNA repair and thus sensitize liver cancer cells to cisplatin. We abrogated the XRCC1 gene in HepG2 cell using shRNA transfection. Cell viability was measured by MTT assay and clonogenicity assay. Comet assay was used to detect the DNA damage induced by cisplatin. The host cell reactivation was employed to assess the DNA repair capacity of cisplatin-damaged luciferase reporter plasmid. Flow cytometry analysis was used to determine cisplatin-induced apoptosis, cell cycle and reactive oxygen species (ROS). The results showed that abrogation of XRCC1 could sensitize HepG2 cells to cisplatin. This enhanced cytotoxicity could be attributed to the increased DNA damage and reduced DNA repair capacity. Increasing cell cycle arrest and intracellular ROS production lead to more tumor cell apoptosis and then enhanced the cisplatin cytotoxicity. Our results suggested that the cisplatin cytotoxicity may increase by targeting inhibition of XRCC1.     

Modulation of DNA repair capacity and mRNA expression levels of XRCC1, hOGG1 and XPC genes in styrene-exposed workers

Decreased levels of single-strand breaks in DNA (SSBs), reflecting DNA damage, have previously been observed with increased styrene exposure in contrast to a dose-dependent increase in the base-excision repair capacity. To clarify further the above aspects, we have investigated the associations between SSBs, micronuclei, DNA repair capacity and mRNA expression in XRCC1, hOGG1 and XPC genes on 71 styrene-exposed and 51 control individuals. Styrene concentrations at workplace and in blood characterized occupational exposure. The workers were divided into low (below 50 mg/m³) and high (above 50 mg/m³) styrene exposure groups. DNA damage and DNA repair capacity were analyzed in peripheral blood lymphocytes by Comet assay. The mRNA expression levels were determined by qPCR. A significant negative correlation was observed between SSBs and styrene concentration at workplace (R = − 0.38, p = 0.001); SSBs were also significantly higher in men (p = 0.001). The capacity to repair irradiation-induced DNA damage was the highest in the low exposure group (1.34 ± 1.00 SSB/10⁹ Da), followed by high exposure group (0.72 ± 0.81 SSB/10⁹ Da) and controls (0.65 ± 0.82 SSB/10⁹ Da). The mRNA expression levels of XRCC1, hOGG1 and XPC negatively correlated with styrene concentrations in blood and at workplace (p < 0.001) and positively with SSBs (p < 0.001). Micronuclei were not affected by styrene exposure, but were higher in older persons and in women (p < 0.001). In this study, we did not confirm previous findings on an increased DNA repair response to styrene-induced genotoxicity. However, negative correlations of SSBs and mRNA expression levels of XRCC1, hOGG1 and XPC with styrene exposure warrant further highly-targeted study.     

Targeting deficient DNA damage repair in gastric cancer

Introduction: Over recent years our understanding of DNA damage repair has evolved leading to an expansion of therapies attempting to exploit DNA damage repair deficiencies across multiple solid tumours. Gastric cancer has been identified as a tumour where a subgroup of patients demonstrates deficiencies in the homologous recombination pathway providing a potential novel treatment approach for this poor prognosis disease.

Area covered: This review provides an overview of DNA damage repair and how this has been targeted to date in other tumour types exploiting the concept of synthetic lethality. This is followed by a discussion of how deficiencies in homologous recombination may be identified across tumour types and on recent progress in targeting DNA repair deficiencies in gastric cancer.

Expert opinion: Gastric cancer remains a difficult malignancy to treat and the possibility of targeting deficient DNA repair in a subgroup of patients is an exciting prospect. Future combinations with immunotherapy and radiotherapy are appealing and appear to have a sound biological rationale. However, much work remains to be done to understand the significance of the genetic and epigenetic alterations involved, to elucidate the optimum predictive signatures or biomarkers and to consider means of overcoming treatment resistance.     

DNA damage and repair in the brain after cerebral ischemia

In experimental models of brain injury of the ischemia-reperfusion type, there is a period of time in which the formation of oxidative damage exceeds its repair. Simultaneously, the expression of immediate early genes is induced to activate the expression of late effector genes. Drugs that reduce the need to repair during this transient period of time also attenuate neuronal death after brain injury. An example discussed in this review is the activator protein-1 (AP-1), the product of the c-fos gene and other immediate early genes. What is the effect of a delayed expression of these genes in relationship to the process of cell death? This short period presents a window of opportunity to study the effects of oxidative damage on gene expression in the brain and specific deficiencies in gene repair that have been associated with particular neurological disorders.     

Targeting DNA damage repair precision medicine strategies in cancer

DNA repair targeted therapeutics is a promising precision medicine strategy in cancer. The development and clinical use of PARP inhibitors has transformed lives for many patients with BRCA germline deficient breast and ovarian cancer as well as platinum sensitive epithelial ovarian cancers. However, lessons learnt from the clinical use of PARP inhibitors also confirm that not all patients respond either due to intrinsic or acquired resistance. Therefore, the search for additional synthetic lethality approaches is an active area of translational and clinical research. Here, we review the current clinical state of PARP inhibitors and other evolving DNA repair targets including ATM, ATR, WEE1 inhibitors and others in cancer.     

Mammalian DNA base excision repair proteins: their interactions and role in repair of oxidative DNA damage

The DNA base excision repair (BER) is a ubiquitous mechanism for removing damage from the genome induced by spontaneous chemical reaction, reactive oxygen species (ROS) and also DNA damage induced by a variety of environmental genotoxicants. DNA repair is essential for maintaining genomic integrity. As we learn more about BER, a more complex mechanism emerges which supersedes the classical, simple pathway requiring only four enzymatic reactions. The key to understand the complete BER process is to elucidate how multiple proteins interact with one another in a coordinated process under specific physiological conditions.