Genetic association between ERCC5 rs17655 polymorphism and lung cancer risk: evidence based on a meta-analysis

Correlation of ERCC5 polymorphisms and linkage disequilibrium associated with overall survival and clinical outcome to chemotherapy in breast cancer

Purpose

ERCC5 is a DNA endonuclease and nucleotide excision repair gene; its mutations lead to a lack of activity by this enzyme, causing oxidative DNA damage. This study aimed to assess the role of four selected single nucleotide polymorphisms (SNPs) in ERCC5 and their linkage disequilibrium associated with survival analysis and clinical outcomes in breast cancer.

Patients and methods

Four SNPs (rs751402, rs17655, rs2094258, and rs873601) of the ERCC5 gene were analyzed using the PCR-RFLP technique, followed by sequencing in 430 breast cancer (BC) cases and 430 cancer-free individuals. Statistical analysis was performed using MedCalc 17 and SPSS version 24, while bioinformatic analysis of linkage disequilibrium was performed using Haploview software 4.2.

Results

Multivariate analysis showed that the rs751402 and rs2094258 polymorphisms were significantly associated with an elevated risk of BC (P < 0.001), while the other two SNPs, rs17655 and rs873601, did not show any association (P > 0.001). Survival analysis revealed that rs751402 and rs2094258 had longer overall survival periods (P <0.001) than rs17655 and rs873601. Moreover, rs751402 and rs2094258 also had significantly longer overall survival (log-rank test, P < 0.005) for all three survival functions (positive family history, ER+PR status, and use of contraceptives), while rs17655 and rs873601 did not show any significant association. Only rs873601 showed a strong negative correlation with all the chemotherapeutic groups.

Conclusion

The current results suggest that variations in ERCC5 may contribute to BC development and that their genetic anomalies may be associated with cancer risk and may be used as a biomarker of clinical outcome.

An insight into clinical outcome of XPG polymorphisms in breast cancer

XPG polymorphisms are associated with varied clinical outcomes in different cancers but up-till now no study has been reported on breast cancer. Therefore, current study was aimed to explore the association of breast cancer risk factors and XPG polymorphisms (rs2296147 and rs1047768). It also investigated impact of XPG variants on overall survival and progression free survival among breast cancer cases. A total of 493 histopathologically identified breast cancer cases and 387 healthy females were genotyped by ARMS-PCR. Relationship between general characteristics, XPG polymorphisms and breast cancer risk was accessed by conditional logistic regression and illustrated by OR and 95% CI. Kaplan Meier test was applied to estimate survival distributions whereas log rank test demonstrated survival differences. Association of XPG variants with OS and PFS in breast cancer was illustrated by HR and 95% CI. Early onset of menopause, consanguinity and family history contributed (P < 0.05) towards breast cancer development. Both rs2296147 and rs1047768 SNPs were found to be associated (P < 0.05) with the risk of breast cancer. XPG rs1047768 was significantly associated with decreased PFS (HR 1.72; 95% CI 1.0-2.8) in breast cancer cases (P = 0.013) which was demonstrated by median time of 26 months for T > C variant when compared with median time of 37 months for TT genotype. No association was found between XPG rs2296147 polymorphism and survival analysis among breast cancer cases. XPG (rs1047768 T > C) variant may play a significant role in terms of decreased PFS and could be used as a predictor of unfavourable prognosis among breast cancer.

XPG rs17655 G>C polymorphism associated with cancer risk: evidence from 60 studies

Xeroderma pigmentosum group G (XPG), a key component in nucleotide excision repair pathway, functions to cut DNA lesions during DNA repair. Genetic variations that alter DNA repair gene expression or function may decrease DNA repair ability and impair genome integrity, thereby predisposing to cancer. The association between XPG rs17655 G>C polymorphism and cancer risk has been investigated extensively, but the results remain contradictory. To get a more accurate conclusion, we performed a comprehensive meta-analysis of 60 case-control studies, involving 27,098 cancer cases and 30,535 healthy controls. Crude odds ratios (ORs) and 95% confidence interval (CIs) were calculated to determine the association of interest. Pooled analysis indicated that the XPG rs17655 G>C polymorphism increased the risk of overall cancer (CC vs. GG: OR=1.10, 95% CI=1.00-1.20; CG vs. GG: OR=1.06, 95% CI=1.02-1.11; CG+CC vs. GG: OR=1.07, 95% CI=1.02-1.12; C vs. G: OR=1.05, 95% CI=1.01-1.09). Stratification analysis by cancer type further showed that this polymorphism was associated with increased risk of gastric cancer and colorectal cancer. This meta-analysis indicated that the XPG gene rs17655 G>C polymorphism was associated with increased overall cancer risk, especially the risk of gastric cancer and colorectal cancer. Further validation experiments are needed to strength our conclusion.

Genetic polymorphisms and lung cancer risk: Evidence from meta-analyses and genome-wide association studies

A growing number of studies investigating the association between Single Nucleotide Polymorphisms (SNPs) and lung cancer risk have been published since over a decade ago. An updated integrative assessment on the credibility and strength of the associations is required. We searched PubMed, Medline, and Web of Science on or before August 29^th, 2016. A total of 198 articles were deemed eligible for inclusion, which addressed the associations between 108 variants and lung cancer. Among the 108 variants, 63 were reported to be significantly associated with lung cancer while the remaining 45 were reported non-significant. Further evaluation integrating the Venice Criteria and false-positive report probability (FPRP) was performed to determine the strength of cumulative epidemiological evidence for the 63 significant associations. As a result, 15 SNPs on or near 12 genes and one miRNA with strong evidence of association with lung cancer risk were identified, including TERT (rs2736098), CHRNA3 (rs1051730), AGPHD1 (rs8034191), CLPTM1L (rs401681 and rs402710), BAT3 (rs3117582), TRNAA (rs4324798), ERCC2 (Lys751Gln), miR-146a2 (rs2910164), CYP1B1 (Arg48Gly), GSTM1 (null/present), SOD2 (C47T), IL-10 (-592C/A and -819C/T), and TP53 (intron 6). 19 SNPs were given moderate rating and 17 SNPs were rated as having weak evidence. In addition, all of the 29 SNPs identified in 12 genome-wide association studies (GWAS) were proved to be noteworthy based on FPRP value. This review summarizes and evaluates the cumulative evidence of genetic polymorphisms and lung cancer risk, which can serve as a general and useful reference for further genetic studies.

Functional Analysis of SNPs in the ERCC5 Promoter in Advanced Colorectal Cancer Patients Treated With Oxaliplatin-Based Chemotherapy

The promoter is the center for regulation of gene transcription due to containing numerous transcription factor binding sites. The aim of the study was to determine whether genetic variations at excision repair cross complementation group 5 (ERCC5) promoter could affect transcription factor binding and whether such single nucleotide polymorphism (SNP)-dependent binding could affect gene expression, drug response, and clinical outcome.A total of 170 patients who were cytologically or histologically confirmed with advanced colorectal cancer (CRC), at least 1 measurable lesion, and underwent oxaliplatin-based chemotherapy were studied. The polymerase chain reaction-ligation detection reaction (PCR-LDR) was used to analyze SNPs. The reporter gene assay system and electrophoretic mobility shift assays (EMSA) were performed to investigate the effect of SNPs on the ERCC5 promoter activity and DNA-binding activity, respectively. The mRNA and protein expression of ERCC5 in tumor tissues of colorectal cancer patients with different genotypes were detected by real-time PCR and western blot, respectively.Both -763A and -763G allele had nuclear protein-binding ability. +25A allele did not show any nuclear protein-binding ability, whereas +25G allele did. The relative luciferase activity of the -763A/+25G haplotype was significantly higher than other 3 haplotypes (P < 0.05). The expression level of ERCC5 mRNA and protein was significantly higher in tumor tissues with -763AA+25GG genotype combination than that with -763GG+25AA genotype combination (P < 0.05, respectively). Allelic variants (-763AA vs -763AG or -763GG, +25GG versus +25AG or +25AA) were significantly associated with shorter progression-free survival (PFS) and overall survival (OS) (P < 0.05, respectively). At multivariate analysis, patients with risk genotypes (-763AA or +25GG genotype) demonstrated a significantly increasing risk of progression (P = 0.01) or worse OS (P = 0.001).The ERCC5 promoter polymorphisms at -763 and +25 may be important functional variants and predictors of clinical outcome of CRC patients who received oxaliplatin chemotherapy.

XPG rs2296147 T>C polymorphism predicted clinical outcome in colorectal cancer

Xeroderma pigmentosum group G (XPG), one of key components of nucleotide excision repair pathway (NER), is involved in excision repair of UV-induced DNA damage. Single nucleotide polymorphisms (SNPs) in the XPG gene have been reported to associate with the clinical outcome of various cancer patients. We aimed to assess the impact of four potentially functional SNPs (rs2094258 C>T, rs2296147 T>C, rs751402 G>A, and rs873601 G>A) in the XPG gene on prognosis in colorectal cancer (CRC) patients. A total of 1901 patients diagnosed with pathologically confirmed CRC were genotyped for four XPG polymorphisms. Cox proportional hazards model analysis controlled for several confounding factors was conducted to compute hazard ratios (HRs) and 95% confidence intervals (CIs). Of the four included SNPs, only rs2296147 was shown to significantly affect progression-free survival (PFS) in CRC. Patients carrying rs2296147 CT/TT genotype had a significantly shorter median 10 years PFS than those carrying CC genotype (88.5 months vs. 118.1 months), and an increased progression risk were observed with rs2296147 (HR = 1.324, 95% CI = 1.046-1.667). Moreover, none of the four SNPs were associated with overall survival. In conclusion, our study showed that XPG rs2296147 CT/TT variants conferred significant survival disadvantage in CRC patients in term of PFS. XPG rs2296147 polymorphism could be predictive of unfavorable prognosis of CRC patients.