Polymorphisms in human DNA repair genes and head and neck squamous cell carcinoma

Comprehensive analysis of DNA damage repair in squamous cell carcinoma subtypes

AIMS

Defective components resulting from DNA damage and repair mechanisms have been found to be underlying causes that affect the development and progression of different types of cancers, including squamous cell carcinoma (SCC). A more detailed classification of SCC is necessary for better application of DNA damage repair therapies.

MATERIALS AND METHODS

We aimed to characterize the molecular profile of SCC by developing a classification system based on DNA damage repair gene expression profiles. An integrative analysis was performed using a metadata set of 1374 SCC human samples from the UCSC Genome Browser. We then analyzed genomic alterations and mutations, and genes-TF-microRNA regulatory relationships and conducted enrichment, survival, and immune infiltration analyses.

KEY FINDINGS

This study was conducted on a total of 1374 SCC patients and 402 DNA damage repair genes. Two subtypes were established using consensus clustering, with 1143 patients being of the Non DDR subtype and 231 patients being of the DDR subtype. MATH, mutation burden, and heterogeneity were significantly higher in Non-DDR subtype than in DDR subtype. Next, a total of 1081 differentially expressed genes and 21 microRNAs were identified between the two subtypes and a genes-TF-microRNA regulatory network was constructed. In addition, stromal score, immune score and ESTIMATE score were significantly lower for the Non-DDR subtype, while tumor purity was significantly lower for the DDR subtype. In addition, five pathways associated with DNA damage repair were all enriched in the DDR subtype.

SIGNIFICANCE

Our study established two subtypes of SCC based on DNA damage repair, which may help to predict prognosis and determine the most suitable treatment for SCC patients.

Assessment on the influence of TLR4 and DNA repair genes in laryngeal cancer susceptibility: a selective examination in a Romanian case control study

Background: Tumor characterization through the study of molecular biology has become an invaluable tool in understanding cancer development and evolution due to its relationship with chromosomal mutations, alterations or aberrations. The purpose of this study was to investigate the involvement of genes such as TLR-4 and DNA repair pathways (XRCC1 and XPD) in laryngeal cancer susceptibility in a Romanian population. Method: We performed a case-control study on 157 laryngeal cancer patients and 101 healthy controls. Genetic testing was carried out using Polymerase Chain Reaction-Restriction Fragment Length Polymorphism. Results: We identified the Gln allele of the XPDLys751Gln polymorphism as an individual risk factor in laryngeal cancer development (Gln vs Lys, adjusted OR=1.65, 95%CI=1.13–2.40, P=0.008). Subjects with the mutant homozygote variant (Gln/Gln) had a two fold increase in cancer risk (adjusted OR=2.18, 95%CI=1.06–4.47, p=0.028) when compared to the reference wild type genotype (Lys/Lys). Stratification by sex and age, identified males under 62 years as the most susceptible group with an almost three fold risk (adjusted OR=2.94, 95%CI=1.31–6.59, p=0.007) for the dominant model (Lys/Gln+Gln/Gln). No associations were found for TLR-4Thr399Ile, XRCC1Arg194Trp and XRCC1Arg399Gln. Conclusion: The results of the study show that the XPDLys751Gln polymorphism may be among other independent risk factors for developing laryngeal cancer where as TLR-4Thr399Ile, XRCC1Arg194Trp and XRCC1 Arg399Gln show no such association. However, we consider the relative small number of the subjects selected for this analyses a possible limitation towards the real influence the obtain results may pertain in laryngeal cancer evolution.

Association between XRCC3 Thr241Met polymorphism and risk of gynecological malignancies: A meta-analysis

Studies have investigated the relationship between the X-ray cross- complementing group 3 (XRCC3) Thr241Met polymorphism and the risk of gynecological malignancies (GM) with the contradictory conclusions. Here, a meta-analysis was performed to provide clear picture of the association between Thr241Met and GM risk. The Pubmed and Chinese National Knowledge Infrastructure (CNKI) databases were searched for published eligible studies. The pooled odds ratios (OR) with their corresponding 95% confidence interval (CI) was used to assessed the strength of association. Totally, 15 publications with 5,740 cases and 9,931 controls were included. In the overall analysis, the results of meta-analysis showed no significant association between the Thr241Met and the risk of GM. However, in the Asians subgroup, significant increased risks were found in the comparisons of TT/CT+TT vs. CC(TT vs. CC: OR=3.25, 95% CI=1.47-7.18; CT+TT vs. CC: OR=1.51, 95%CI=1.10-2.09) in Asians; additionally, stratified analysis by cancer type in Asians, significantly increased risks was found in cervical carcinoma (CT vs. CC: OR=1.50, 95%CI=1.04-2.14; TT vs. CC: OR=3.14, 95%CI=1.38-7.14; CT+TT vs. CC: OR=1.64, 95% CI=1.17-2.31). It suggests that the risk of GM might be significantly increased by the XRCC3 Thr241Met polymorphism according to ethnicity and cancer types. Further studies with larger sample size in different ethnic populations and different sites of GM are needed to verify the findings.

Identification of novel heterozygous Apex 1 gene variant (Glu87Gln) in patients with head and neck cancer of Indian origin

Gene polymorphism among humans is one of the factors governing individual's susceptibility and resistance to various diseases including cancer. DNA repair enzymes play an important role in protecting our genome from various mutagens and preventing cancer. The role of DNA repair enzyme Apurinic/Apyrimidinic endodeoxyribonuclease 1 (Apex 1) in cancer has been very well documented. Using genomic DNA, Apex 1 coding region of 76 patients (n = 76) with head and neck cancer were amplified and sequenced to detect variations in the sequence. Of 76 patients, 1 patient with heterozygous novel Apex 1 variant (Glu87Gln) was identified. A comparative analysis of wild type and variant protein using in silico approach was performed to understand the difference in the structure and the function. This further revealed that the variant had a slight impact on the structure, which affected the stability and function of the protein. Using the state-of-the-art Molecular dynamic simulation analysis, we observed a loss in number of hydrogen bonds and salt bridge with a substitution of Gln for Glu at Position 87. This could be a possible reason behind the loss of stability/function of the protein. This study revealed a new variant of the Apex 1 gene; further studies will lead to the novel roles played by the variant Apex 1 protein in cause, disease progression, and response to the treatment in patients with cancer with Glu87Gln variant.

Common polymorphisms of the hOGG1, APE1 and XRCC1 genes correlate with the susceptibility and clinicopathological features of primary angle-closure glaucoma

The present case study aims to elucidate the correlation between the human 8-hydroxyguanineglycosylase (hOGG1), APE1 and X-ray repair cross-complementing gene 1 (XRCC1) gene polymorphisms to the susceptibility and clinicopathological features of primary angle closure glaucoma (PACG) in a Chinese Han population. Blood samples were obtained from 258 PACG patients (case group) and 272 healthy volunteers (control group). PCR with sequence-specific primer (PCR-SSP) was used to determine the allele frequencies and genotype distributions of the hOGG1, APE1 and XRCC1 genes. The risk factors of PACG were determined using logistic regression analysis. The results indicated that hOGG1 Ser326Cys, APE1 Asp148Glu and XRCC1 Arg399Gln polymorphisms were correlated with the risk of PACG. Furthermore, there were thicker corneas, higher intraocular pressure (IOP) and a shorter axial length in patients carrying the mutant genotypes of hOGG1 Ser326Cys (Ser/Cys + Cys/Cys), APE1 Asp148Glu (Asp/Glu + Glu/Glu) and XRCC1 Arg399Gln (Arg/Gln + Glu/Glu) than those carrying the corresponding wild-type genotypes. According to the logistic regression analysis, Asp148Glu and Arg399Gln polymorphisms, a short axial length and high IOP are major risk factors for PACG. These findings reveal that hOGG1 Ser326Cys, APE1 Asp148Glu and XRCC1 Arg399Gln polymorphisms are correlated with the risk and clinicopathological features of PACG in a Chinese Han population.

Association of GSTT1 null, XPD 751 CC and XPC 939 CC genotypes with increased levels of genomic damage among hospital pathologists

CONTEXT

Hospital workers are at risk for genotoxic damage following occupationally exposure to xenobiotics. Pathologists are exposed to chemicals during their use in health care environments, particularly throughout inhalation of airborne agents, absorption through skin or contact with the patient's body fluids.

OBJECTIVE

We evaluated the level of genomic damage in a sample of 61 hospital pathologists (occupationally exposed to antineoplastic drugs and sterilizing agents) and 60 control subjects.

MATERIALS AND METHODS

Lymphocytes were analyzed by SCEs and CAs assays and genotyped for GSTT1, GSTM1, CYP1A1 Ile/Val, XPD (A751C) and XPC (A939C) gene polymorphisms.

RESULTS

Pathologists showed significantly higher frequencies of SCEs and CAs with respect to control subjects. GSTT1 null genotype was found to be associated with higher SCEs and CAs frequencies, whereas XPD 751 CC and XPC 939 CC genotypes only with a higher level of SCEs.

DISCUSSION AND CONCLUSIONS

The SCEs and CAs results are consistent with other published data, placing hospital workers as a category at risk for genotoxic damage caused by chronic exposure to xenobiotics. The higher levels of cytogenetic damage observed among GSTT1 null, XPD 751 and XPC 939 CC homozygote subjects confirm the importance of the genetic polymorphisms analysis associated to genotoxicological studies.

XRCC3 is a promising target to improve the radiotherapy effect of esophageal squamous cell carcinoma

Radiotherapy is widely applied for treatment of esophageal squamous cell carcinoma (ESCC). The Rad51-related protein XRCC3 plays roles in the recombinational repair of DNA double-strand breaks to maintain chromosome stability and repair DNA damage. The present study aimed to investigate the effect of XRCC3 on the radiotherapy response of ESCC and the underlying mechanisms of the roles of XRCC3 in ESCC radiosensitivity. XRCC3 expression in ESCC cells and tissues was higher than that in normal esophageal epithelial cells and corresponding adjacent noncancerous esophageal tissue. High XRCC3 expression was positively correlated with resistance to chemoradiotherapy in ESCC and an independent predictor for short disease-specific survival of ESCC patients. Furthermore, the therapeutic efficacy of radiotherapy in vitro and in vivo was substantially increased by knockdown of XRCC3 in ESCC cells. Ectopic overexpression of XRCC3 in both XRCC3-silenced ESCC cells dramatically enhanced ESCC cells' resistance to radiotherapy. Moreover, radiation resistance conferred by XRCC3 was attributed to enhancement of homologous recombination, maintenance of telomere stability, and a reduction of ESCC cell death by radiation-induced apoptosis and mitotic catastrophe. Our data suggest that XRCC3 protects ESCC cells from ionizing radiation-induced death by promoting DNA damage repair and/or enhancing telomere stability. XRCC3 may be a novel radiosensitivity predictor and promising therapeutic target for ESCC.

Photosensitive human syndromes

Photosensitivity in humans can result from defects in repair of light-induced DNA lesions, from photoactivation of chemicals (including certain medications) with sunlight to produce toxic mediators, and by immune reactions to sunlight exposures. Deficiencies in DNA repair and the processing of damaged DNA during replication and transcription may result in mutations and genomic instability. We will review current understanding of photosensitivity to short wavelength ultraviolet light (UV) due to genetic defects in particular DNA repair pathways; deficiencies in some are characterized by an extremely high incidence of cancer in sun-exposed tissues, while in others no cancers have been reported.

Gene-environment interactions in determining differences in genetic susceptibility to cancer in subsites of the head and neck

Genetic differences in susceptibility to cancer in subsites of the head and neck were investigated in a case-control study involving 750 cases of cancers of the oral cavity, larynx, or pharynx, and an equal number of healthy controls. The prevalence of variant genotypes of cytochrome P450 (CYP) 1A1, 1B1, 2E1, or glutathione-S-transferase M1 (null) in cases suggests that polymorphisms in drug metabolizing enzymes (DMEs) modify cancer risk within subsites of the head and neck. Tobacco or alcohol use was found to increase the risk in cases of laryngeal, pharyngeal, or oral cavity cancers. Interaction between genetic variation in DMEs and tobacco smoke (or smoking) exposures conferred significant risk for laryngeal cancer. Likewise, strong associations of the polymorphic genotypes of DMEs with cases of pharyngeal and oral cavity cancer who were tobacco chewers or alcohol users demonstrate that gene-environment interactions may explain differences in genetic susceptibility for cancers of the oral cavity, larynx, and pharynx.

Association of X-ray repair cross complementing group 1 Arg399Gln polymorphisms with the risk of squamous cell carcinoma of the head and neck: evidence from an updated meta-analysis

BACKGROUND

Epidemiologic studies have reported the association of X-ray repair cross-complementary group 1 (XRCC1) Arg399Gln polymorphisms with susceptibility to squamous cell carcinoma of the head and neck (HNSCC). However, the results were conflictive rather than conclusive. The purpose of this study was to clarify the association of XRCC1 Arg399Gln variants with HNSCC risk.

METHODS

Systematic searches were performed through the search engines of PubMed, Elsevier, Science Direct, CNKI and Chinese Biomedical Literature Database. Summary odds ratio (OR) with 95% confidence intervals (CI) was computed to estimate the strength association.

RESULTS

Overall, we did not observe any association of XRCC1 Arg399Gln polymorphisms with HNSCC risk in total population (OR = 0.95, 95% CI: 0.76-1.19 for Gln/Gln vs. Arg/Arg, OR = 1.05, 95% CI: 0.92-1.20 for Arg/Gln vs. Arg/Arg, and OR = 1.03, 95% CI: 0.90-1.18 for Gln/Gln+Arg/Gln vs. Arg/Arg) based on 18 studies including 3917 cases and 4560 controls. In subgroup analyses, we observed an increased risk of XRCC1 399 Arg/Gln genotype for HNSCC in Caucasians (OR = 1.20, 95% CI: 1.00-1.44) and Gln/Gln genotype for larynx squamous cell carcinoma (OR = 1.63, 95% CI: 1.10-2.40). We did not observe any association between XRCC1 Arg399Gln variants and HNSCC risk in additional subgroup analyses.

CONCLUSION

The results from this present meta-analysis suggest that XRCC1 Arg399Gln variants may contribute to HNSCC risk among Caucasians and to the risk of larynx squamous cell carcinoma. Further, well-designed studies with larger sample sizes are required to verify our findings.

DNA repair gene XRCC1 polymorphisms and head and neck cancer risk: an updated meta-analysis including 16344 subjects

BACKGROUND

DNA repair gene X-ray repair cross complementing group 1 (XRCC1) plays an important role in the maintenance of the genomic integrity and protection of cells from DNA damage. Sequence variation in XRCC1 gene may alter head and neck cancer (HNC) susceptibility. However, these results are inconclusive. To derive a more precise estimation of the relationship between XRCC1 polymorphism and HNC risk, we undertook a meta-analysis involving 16,344 subjects.

METHODS

A search of the literature by PubMed, Embase, Web of Science and China National Knowledge Infrastructure was performed to identify studies based on the predetermined inclusion criteria. The odds ratio (OR) with 95% confidence interval (CI) was combined using a random-effects model or a fixed-effects model.

RESULTS

Twenty-nine studies consisting of 6,719 cases and 9,627 controls were identified and analyzed. Overall, no evidence of significant association was observed between XRCC1 Arg194Trp, XRCC1 Arg280His, XRCC1 Arg399Gln genotypes and the risk of HNC in any genetic models. Subgroup analyses according to ethnicity, tumor site, publication year, genotyping method also detected no significant association in any subgroup, except that oral cancer was associated with Arg194Trp variant in recessive model. Furthermore, no significant effect of these polymorphisms interacted with smoking on HNC risk was detected but Arg194Trp homozygous variant.

CONCLUSION

In conclusion, this meta-analysis suggests that the XRCC1 Arg194Trp, Arg280His and Arg399Gln polymorphism may not involve in HNC susceptibility. Further studies about gene-gene and gene-environment interactions in different populations are required.