核苷酸切除修复与铂类耐药研究进展

目前肿瘤化疗仍以肿瘤发生部位和病理类型为基础选择药物,由于肿瘤本身以及个体之间存在异质性,相同部位和相同病理类型的肿瘤对化疗敏感性存在差异。长期以来,人们追求根据肿瘤自身药物敏感性开展个体化治疗。近年来,药物敏感相关基因检测获得快速发展,使个体化化疗成为可能。在相关基因与化疗药物研究领域中,核苷酸切除修复基因与铂类药物研究是最受瞩目的内容之一。1铂类药物耐药机制铂类药物(顺铂、卡铂、草酸铂)是临床上最常用的一类化疗药物。铂类药物进入肿瘤细胞后与DNA结合,形成Pt-DNA加合物,导致DNA的链间或链内交链,引起DNA复制障碍,从而抑制肿瘤细胞分裂。铂类药物的耐药机制主要有减少药物摄取积聚、通过共扼结合去除药物毒性、提高对铂类药物诱导产生的DNA加合物的耐受性及提高DNA修复能力等。研究证实,临床缓解率与循环中Pt-DNA加合物的水平相关,如果肿瘤细胞DNA修复能力减低,就会导致Pt-DNA加合物清除减少,使患者对铂类药物的疗效提高,反之疗效则差。因此,DNA修复能力是影响铂类药物疗效的主要原因。DNA切除修复途径主要有碱基切除修复(base-exc ision repair,BER)、DNA双链断裂修复(DN...     

DNA修复基因单核苷酸多态性预测铂类药物敏感性和预后

铂类药物是治疗实体肿瘤常用的药物之一,但是肿瘤细胞对铂类药物耐药导致化疗失败,成为临床治疗的一大难题。DNA修复能力是影响疗效的重要原因。DNA修复基因单核苷酸多态性(SNP)可改变DNA修复能力,因此,检测这些基因的单核苷酸多态性可以预测疗效。现综述DNA修复基因单核苷酸多态性预测铂类药物敏感性和预后的研究进展。     

铂类药物化疗与基因多态性临床研究进展

化疗是恶性肿瘤治疗支柱之一,选择敏感而低毒的化疗药物是提高疗效减轻不良反应的关键。现阶段随着研究的不断深入,已有多种抗肿瘤药物可通过化疗药物疗效及毒性预测分子及其基因多态性预测患者对相应药物的敏感性和毒性。铂类药物是最常用的化疗药物,与其它药物组成了多种有效的化疗方案,这里我们对常见铂类药物的疗效预测分子做一综述,为临床深入开展“铂类药物疗效预测个体化化疗”提供依据和支持。铂类药物进入肿瘤细胞后与DNA结合,形成Pt-DNA加合物,导致DNA的链间或链内交链,引起DNA复制障碍。DNA修复能力是影响铂类药物疗效的…     

核苷酸切除修复通路基因多态性与肺癌易感性研究

目的研究显示核苷酸切除修复通路在去除吸烟引起的DNA损伤中发挥着重要的作用,旨在探讨核苷酸切除修复通路单核苷酸多态性与吸烟相关性肺癌易感性的关系。方法选取1010例肺癌患者和1011例正常对照。采用基于通路的候选基因选点策略,从核苷酸切除修复通路相关的8个核心基因中筛选出40个标签SNPs进行检测和分析。结果单个位点分析发现6个SNPs（ERCC1 2个,DDB2 2个,ERCC4／XPF 1个,XPC 1个）与肺癌的易感性相关。进一步采用Logistic回归模型,调整年龄、性别、吸烟史和肿瘤家族史后,仍有3个SNPs（ERCC1 rs3212948,DDB2 rs830083,ERCC4 rs3136038）与肺癌易感性存在统计学关联。等位基因联合分析结果进一步表明肺癌的发病风险随着风险等位基因个数的增加而增加,尤其是ERCC1,ERCC2,ERCC3,ERCC5,XPA和XPC。结论本研究结果提示核苷酸切除修复通路基因多态性可能与中国汉族人群的肺癌个体易感性有关,值得进一步进行功能学探讨及大样本人群验证.     

切除修复交叉互补基因1与铂类药物耐药

铂类药物耐药是多种复杂机制共同作用的结果.其中,肿瘤细胞切除修复交叉互补基因1(ERCC1)表达及其多态性是肿瘤细胞产生铂类药物耐药的重要机制之一.抑制ERCC1的表达可逆转铂类药物耐药性.     

碱基切除修复基因多态性与晚期非小细胞肺癌铂类药物化疗敏感性

目的:探讨DNA碱基切除修复通路中XRCC1 Arg399Gln和ADPRT Val762Ala基因多态性与晚期非小细胞肺癌(NSCLC)铂类药物化疗敏感性的关联,并与先前报道的XRCC1 T-77C、Argl94Trp联合分析其预测作用.方法:收集接受铂类药物为基础化疗的晚期NSCLC患者107例,用PCR-RFLP法检测基因型,分析各基因型与铂类药物化疗有效率的关联,并以非条件Logistic回归模型对患者年龄、性别、病理类型、临床分期和治疗方案进行校正.结果:对XRCC1 Arg399Gln多态性进行单因素分析时,发现携带至少1个Gln等位基因的患者的化疗有效率是携带Arg/Arg基因型者的0.42倍(95%CI:0.19-0.93),差异具有统计学意义;经多因素校正后发现携带至少1个Gln等位基因的患者的化疗有效率是携带Arg/Arg基因型者的0.52倍(95%CI:0.22-1.26),但差异不再具有统计学意义.对ADPRT Val762Ala多态性进行多因素分析时,发现携带至少1个Ala等位基因的患者的化疗有效率是携带Val/Val基因型者的1.57倍(95%CI:0.67-3.66).联合分析各患者4个多态性位点的铂类药物敏感基因型的总数目与铂类药物化疗有效率的关联,并经多因素分析校正后,发现携带3-4个铂类药物敏感基因型的患者的化疗有效率是具有0-2个铂类药物敏感基因型者的4.15倍(95%CI:1.54-11.19),差异具有统计学意义.结论:XRCC1 Arg399Gln多态性与铂类药物化疗敏感性的关系需进一步确认,似乎携带野生型Arg/Arg者对铂类药物化疗更敏感;但未能发现ADPRTVal762Ala多态性与铂类药物化疗敏感性存在明显关联;4个多态性位点联合分析的预测效能高于单个位点.     

rs9904341多态性与肺癌易感性和铂类药物化疗敏感性的相关性

[目的]探讨survivin基因启动子区rs9904341位点多态性与肺癌发生风险和晚期非小细胞肺癌(NSCLC)患者铂类药物化疗疗效的关系。[方法]通过聚合酶链反应—限制性酶切片断多态性方法(PCR-RFLP)检测289例健康对照组和289例肺癌患者的rs9904341多态性的基因型;其中130例晚期NSCLC仅接受铂类药物化疗,分析经2个周期化疗后的疗效及基因型与铂类药物化疗疗效和生存期的关系。[结果]基因型CC、CG、GG在肺癌组的分布频率分别为29.07%、47.05%、23.87%,在对照组的分布频率分别为20.42%、51.9%、27.68%,两组无显著性差异(P=0.053)。肺癌组中C等位基因和CC基因型的分布均显著高于对照组(P<0.05)。rs9904341多态性与晚期NSCLC患者铂类药物化疗有效率无显著相关性,但与临床受益率相关,GG基因型携带者的临床受益率是CC基因型者的2.06倍(95%CI:0.71～5.97,P=0.184)。对289例肺癌患者生存分析显示,CC基因型肺癌患者较CG+GG基因型预后差(95%CI:1.11～2.6,P=0.015)。[结论]rs9904341多态性与肺癌的发病风险、预后及晚期NSCLC患者铂类药物化疗临床受益率相关。     

肺癌化疗中铂类药物耐药性检测的研究进展

本以铂类耐药相关的p-gP、MRP、p-53、LRP、谷胱甘肽有关的解毒系统检测为重点，就肺癌化疗中铂类药物耐药性的检测进行了简要综述。虽然在这方面有许多问题需要进一步研究，但联合GST-π、P-53、LRP、γ-GCS检测必将有助于临床对肺癌铂类药物耐药性的监测。     

DNA修复基因单核苷酸多态性与铂类药物抵抗研究进展

目前,肿瘤的标准化疗仍然是以解剖部位为基础选择化疗药物,但由于肿瘤本身以及患者个体之间异质性的存在,同一部位的肿瘤对标准化疗的敏感性及化疗产生的毒副反应差异很大。以肿瘤自身药物敏感性为指导开展个体化的药物治疗成为多年来临床研究的热点。随着人类基因组计划的完成,恶性肿瘤的分子亚分类成为可能,以药物敏感相关基因为检测目标的药物基因组学、药物遗传学获得快速发展,使个体化的药物治疗成为可能。     

核苷酸切除修复基因XPA反义RNA增强肺癌细胞对顺铂的敏感性

背景与目的：目前认为,肿瘤细胞自身核苷酸切除修复(nucleotide excision repair,NER)能力增强是肿瘤细胞产生耐药性最重要的机制之一。着色性干皮病A(xeroderma pigmentosun groupA,XPA)基因在核苷酸切除修复早期发挥核心作用。本研究拟探讨XPA基因表达与肺癌细胞株对顺铂敏感性的关系。方法：将XPA的反义RNA稳定转染人肺癌细胞株A549．用有限稀释法筛选阳性细胞克隆。分别用Northern blot和Western blot法检测阳性细胞克隆XPA mRNA和蛋白水平;MTT法检测肿瘤细胞对顺铂敏感性;宿主细胞再活化反应(host cell reactivation,HCR)检测肿瘤细胞DNA损伤修复能力。结果：筛选得到6个阳性克隆AS1～AS6,其中AS3～AS6细胞克隆的XPAmRNA和蛋白水平均明显降低。剂量依赖实验表明,顺铂对A549细胞与AS1～AS6细胞克隆的半数抑制浓度(IC50)分别为8．1、7．6、4．7、3．2、1．9、2．8、4．1~g／ml。统计学分析表明．与A549细胞相比,AS3～AS6细胞对顺铂的敏感性明显增强(F=9．75、9．14、7．39、8．91,P=0．005、0．006、0．012、0．006),而且XPA mRNA表达水平与细胞IC50值呈显著相关(r=0．927,P=0．003)。处理24、48、72h后,AS3～AS6细胞对顺铂的敏感性同样显著增强。HCR实验结果表明,AS3～AS6细胞的NER能力显著减弱,而且XPA mRNA表达水平与细胞NER能力呈显著相关(r=0．854、0．696、0．858;p=0．014、0．082、0．013)。结论：XPA反义RNA转染可明显降低肺癌细胞XPAmRNA水平,减弱细胞NER能力,继而使肺癌细胞对顺铂的敏感性增强。     

Nucleotide excision repair gene XPD polymorphisms and genetic predisposition to melanoma

The nucleotide excision repair pathway has evolved to deal with UV light-induced DNA damage. Individuals with the rare inherited nucleotide excision repair deficiency disease xeroderma pigmentosum have a 1000-fold increased incidence of skin cancer. We are interested in the possibility that more subtle changes in nucleotide excision repair genes, resulting in either a reduced capacity for repair or in altered interactions between repair proteins and components of the cell cycle control machinery, might constitute important genetic risk factors for the development of skin cancer in the general population. To investigate this hypothesis we have compared the frequency of polymorphisms in exons 6, 22 and 23 of the XPD gene in melanoma patients and a control group. For each of these two allele polymorphisms one of the alleles was over-represented in the melanoma group and there was a significant association with melanoma. Importantly, this association did not extend to markers immediately flanking the XPD gene, thus providing evidence that XPD gene polymorphisms might predispose to melanoma in the general population. There is a report that one of the polymorphic XPD alleles (exon 23 Lys), which is over-represented in the melanoma group, has reduced repair proficiency and we discuss the possibility that this is the causal change to the XPD gene that predisposes to melanoma.     

Nucleotide excision repair and human syndromes

DNA damage is implicated in cancer and aging, and several DNA repair mechanisms exist that safeguard the genome from these deleterious consequences. Nucleotide excision repair (NER) removes a wide diversity of lesions, the main of which include UV-induced lesions, bulky chemical adducts and some forms of oxidative damage. The NER process involves the action of at least 30 proteins in a 'cut-and-paste'-like mechanism. The consequences of a defect in one of the NER proteins are apparent from three rare recessive syndromes: xeroderma pigmentosum (XP), Cockayne syndrome (CS) and the photosensitive form of the brittle hair disorder trichothiodystrophy (TTD). Sun-sensitive skin is associated with skin cancer predisposition in the case of XP, but remarkably not in CS and TTD. Moreover, the spectrum of clinical symptoms differs considerably between the three syndromes. CS and TTD patients exhibit a spectrum of neurodevelopmental abnormalities and, in addition, TTD is associated with ichthyosis and brittle hair. These typical CS and TTD abnormalities are difficult to comprehend as a consequence of defective NER. This review briefly describes the biochemistry of the NER process, summarizes the clinical features of the NER disorders and speculates on the molecular basis underlying these pleitropic syndromes.     

Nucleotide excision repair gene polymorphisms and recurrence after treatment for superficial bladder cancer.

PURPOSE: Interindividual differences in DNA repair capacity not only modify individual susceptibility to carcinogenesis, but also affect individual response to cancer treatment. Nucleotide excision repair (NER) is one of the major DNA repair pathways in mammalian cells involved in the removal of a wide variety of DNA lesions. Polymorphisms in NER genes may influence DNA repair capacity and affect clinical outcome of bladder cancer treatment. EXPERIMENTAL DESIGN: To test the influence of NER gene polymorphisms on superficial bladder cancer outcome (recurrence and progression), we conducted a follow-up study of 288 patients with superficial bladder cancer. Median follow-up among patients who were recurrence-free at the end of observation was 21.7 months from diagnosis. The specific polymorphic loci examined include XPA [A/G at 5' untranslated region (UTR)], XPC (poly AT, Ala(499)Val, Lys(939)Gln), XPD (Asp(312)Asn, Lys(751)Gln), XPG (His(1104)Asp), ERCC 1 (G/T at 3' UTR), and ERCC6 (Met(1097)Val, Arg(1230)Pro). RESULTS: The ERCC6 (Met(1097)Val) polymorphism had a significant impact on recurrence: carriers of at least one variant allele (Val) had a significantly higher recurrence risk than carriers of the wild-type allele (Met/Met; hazard ratio, 1.54; 95% confidence interval, 1.02-2.33). There were no overall statistically significant differences in the distributions of the other polymorphisms between patients with and without recurrence. However, when we combined these variant genotypes, there was a significant trend for an increased recurrence risk with an increasing number of putative high-risk alleles. Using individuals with five or fewer putative high-risk alleles as the reference group, individuals with six to seven risk alleles and individuals with eight or more risk alleles had higher recurrence risks, with hazard ratios of 0.92 (0.54-1.57) and 2.53 (1.48-4.30), respectively (P for trend < 0.001). There was also a significant trend for shorter recurrence-free survival time with increasing number of variant alleles (log rank test, P = 0.0007). When we stratified the patients according to intravesical Bacillus Calmette-Guerin treatment, we found a significant trend for shorter recurrence-free survival time in patients with variant alleles of XPA or ERCC6 polymorphisms who received Bacillus Calmette-Guerin treatment (log rank test, P = 0.078 and 0.022, respectively). There were no significant individual or joint associations between these polymorphisms and progression. CONCLUSIONS: These data suggest that interindividual differences in DNA repair capacity may have an important impact on superficial bladder cancer recurrence. A pathway-based approach is preferred to study the effects of individual polymorphism on clinical outcomes.     

Nucleotide excision repair gene polymorphisms and risk of advanced colorectal adenoma: XPC polymorphisms modify smoking-related risk.

OBJECTIVES: Nucleotide excision repair enzymes remove bulky damage caused by environmental agents, including carcinogenic polycyclic aromatic hydrocarbons found in cigarette smoke, a risk factor for colorectal adenoma. Among participants randomized to the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, we studied the risk of advanced colorectal adenoma in relation to cigarette smoking and selected single nucleotide polymorphisms (SNP) in the nucleotide excision repair pathway.METHODS: Cases (n = 772) were subjects with left-sided advanced adenoma (>1 cm in size, high-grade dysplasia, or villous characteristics). Controls (n = 777) were screen-negative for left-sided polyps by sigmoidoscopy. DNA was extracted from blood samples and 15 common nonsynonymous SNPs in seven-nucleotide excision repair genes [XPC, RAD23B (hHR23B), CSB (ERCC6), XPD (ERCC2), CCNH, XPF (ERCC4), and XPG (ERCC5)] were genotyped.RESULTS: None of the studied SNPs were independently associated with advanced adenoma risk. Smoking was related to adenoma risk and XPC polymorphisms (R492H, A499V, K939Q) modified these effects (P(interaction) from 0.03-0.003). Although the three XPC variants were in linkage disequilibrium, a multivariate logistic regression tended to show independent protective effects for XPC 499V (P(trend) = 0.06), a finding supported by haplotype analysis (covariate-adjusted global permutation P = 0.03).CONCLUSIONS: Examining a spectrum of polymorphic variants in nucleotide excision repair genes, we found evidence that smoking-associated risks for advanced colorectal adenoma are modified by polymorphisms in XPC, particularly haplotypes containing XPC 499V.     

Nucleotide excision repair polymorphisms may modify ionizing radiation-related breast cancer risk in US radiologic technologists

Exposure to ionizing radiation has been consistently associated with increased risk of female breast cancer. Although the majority of DNA damage caused by ionizing radiation is corrected by the base-excision repair pathway, certain types of multiple-base damage can only be repaired through the nucleotide excision repair pathway. In a nested case-control study of breast cancer in US radiologic technologists exposed to low levels of ionizing radiation (858 cases, 1,083 controls), we examined whether risk of breast cancer conferred by radiation was modified by nucleotide excision gene polymorphisms ERCC2 (XPD) rs13181, ERCC4 (XPF) rs1800067 and rs1800124, ERCC5 (XPG) rs1047769 and rs17655; and ERCC6 rs2228526. Of the 6 ERCC variants examined, only ERCC5 rs17655 showed a borderline main effect association with breast cancer risk (OR(GC) = 1.1, OR(CC) = 1.3; p-trend = 0.08), with some indication that individuals carrying the C allele variant were more susceptible to the effects of occupational radiation (EOR/Gy(GG) = 1.0, 95% CI = <0, 6.0; EOR/Gy(GC/CC) = 5.9, 95% CI = 0.9, 14.4; p(het) = 0.10). ERCC2 rs13181, although not associated with breast cancer risk overall, statistically significantly modified the effect of occupational radiation dose on risk of breast cancer (EOR/Gy(AA) = 9.1, 95% CI = 2.1-21.3; EOR/Gy(AC/CC) = 0.6, 95% CI = <0, 4.6; p(het) = 0.01). These results suggest that common variants in nucleotide excision repair genes may modify the association between occupational radiation exposure and breast cancer risk.     

Nucleotide excision repair pathway genes and oral premalignant lesions.

PURPOSE: Oral premalignant lesions (OPL) are associated with tobacco exposure and an increase in risk of oral cancer. Nucleotide excision repair (NER) is one of the major DNA repair pathways involved in the removal of tobacco carcinogen adducts. Polymorphisms in NER genes may cause variations in DNA repair capacity and increase susceptibility to both premalignant lesions and cancer. EXPERIMENTAL DESIGN: In this case-control study of 144 OPL patients and 288 controls, we genotyped 11 polymorphisms in 8 major NER genes, including XPA [A23G at 5' untranslated region (UTR)], XPD (Asp312Asn, Lys751Gln), XPC (Ala499Val, Lys939Gln), XPG (His1104Asp), XPF (Pro662Ser), ERCC6 (Met1097Val, Arg1230Pro) Rad23B (Ala249Val), and CCNH (Val270Ala). RESULTS: We found significant or borderline-significant associations between OPL risk and the polymorphisms XPA (A23G), XPD (Lys751Gln), XPC (Ala499Val), Rad23B (Ala249Val), and XPD (Asp312Asn), with adjusted odds ratios (ORs) of 1.97 [95% confidence interval (95% CI), 1.27-3.06], 1.60 (95% CI, 1.02-2.51), 0.63 (95% CI, 0.40-1.00), 0.67 (95% CI, 0.41-1.07), and 1.42 (95% CI, 0.90-2.23), respectively. When further stratified analyses were done, the decreased risk conferred by the XPC (Ala499Val) variant allele was more evident in older individuals (OR, 0.50; 95% CI, 0.24-1.03), in women (OR, 0.46; 95% CI, 0.21-1.01), in ever smokers (OR, 0.59; 95% CI, 0.33-1.05), and in never drinkers (OR, 0.42; 95% CI, 0.18-1.00). Finally, we found joint effects between these NER gene variants and smoking status. For example, when never smokers with the XPA 23A genotypes were used as the reference group, the ORs for never smokers with the XPA 23G genotype, smokers with the 23A genotype, and smokers with 23G genotypes were 2.19 (1.07-4.46), 2.64 (1.42-4.89), and 5.04 (2.62-9.69), respectively. Gene-gene and gene-smoking interaction for OPLs risk were also confirmed by multifactor dimensionality reduction (MDR) analysis in our study. MDR analysis revealed that a model containing ever smoking, XPA (A23G), XPC (Ala499Val), and XPD (Asp312Asn) was the best model to predict OPL risk with maximum average cross-validation consistency and minimum prediction error (P < 0.001). CONCLUSION: Our results suggest that polymorphisms in NER genes may contribute to genetic susceptibility to OPLs and may therefore contribute to the development of oral cancer.     

Association of genetic polymorphisms in the base excision repair pathway with lung cancer risk: a meta-analysis

Lung cancer is a major cause of cancer-related death in the developed countries and the overall survival rate has still an extremely poor. Although cigarette smoking is the main cause of lung cancer, not all smokers develop lung cancer, and a fraction of lifelong non-smokers will die from lung cancer. Genetic host factors have recently been implicated to account for some of the observed differences in lung cancer susceptibility. Various DNA alterations can be caused by exposure to environmental and endogenous carcinogens. Most of these alterations, if not repaired, may result in genetic instability, mutagenesis and cell death. DNA repair mechanisms are important for maintaining DNA integrity and preventing carcinogenesis. Recent genetic association studies on lung cancer risk have focused on identifying effects of single nucleotide polymorphisms (SNPs) in candidate genes, among which DNA repair genes are increasingly studied. Genetic variations in DNA repair genes are thought to modulate DNA repair capacity and are suggested to be related to lung cancer risk. We identified a sufficient number of epidemiologic studies on lung cancer to conduct a meta-analysis for genetic polymorphisms in nucleotide base repair (BER) pathway, focusing on 8-oxoguanine DNA glycosylase 1, X-ray cross-complementing group 1 (XRCC1) and apurinic/apyrimidinic endonuclease 1. The 399Gln/Gln genotype of the XRCC1 Arg399Gln polymorphism was associated with an increased risk of lung cancer among Asians (OR=1.34, 95% CI=1.16-1.54) but not among Caucasians. Little evidence of associations has been found between other BER genes and lung cancer risk. Considering the data available, it can be conjectured that if there is any risk association between single SNP and lung cancer, this risk increase/decrease will probably be minimal. Advances in identification of new polymorphisms and in high-throughput genotyping techniques will facilitate analysis of multiple genes in multiple DNA repair pathways. Therefore, it is likely that the defining feature of future epidemiologic studies will be the simultaneous analysis of large samples of cases and controls.