Association between the XRCC6 polymorphisms and cancer risks: a systematic review and meta-analysis

An overview of chemically induced rodent models for sporadic colorectal cancer: Histopathological and translational perspectives

Globally, colorectal cancer (CRC) is one of the most frequently diagnosed human gastrointestinal neoplasia and the second leading cause of cancer-related death in both men and women. Despite considerable efforts currently devoted to the study of the biology and treatment of CRC, patient prognosis and survival are still poor. Sporadic CRC is a complex multistep disease and usually emerges in the setting of lifestyle and dietary changes mainly observed in industrialized countries with high human development index (HDI) (westernized style). The molecular pathogenesis of sporadic CRC presents genetic heterogeneity with APC, RAS, PIK3CA, TGFBR, SMAD4, and TP53 mutations usually detected during the progression of this malignancy. The establishment of sporadic CRC models has become essential for both basic and translational research to improve our understanding of the pathophysiology, unravel new molecular drivers, and preventive/therapeutic improvement of this malignancy. Chemically induced rodent models of sporadic CRC recapitulate most key morphological and genetic/epigenetic events observed during the promotion and progression of this malignancy, establishing effective diagnostic and prevention strategies to be translated into clinical practice. The present review gathers the main features of the state-of-the-art evidence on chemically induced rodent models, widely applied for translational modelling of sporadic CRC with a specific focus on histopathology and prevention perspectives. Our narrative review reinforces the persistent value of these bioassays and encourages the use of multimodel strategies for further investigations.

DNA Double-Strand Break Response and Repair Gene Polymorphisms May Influence Therapy Results and Prognosis in Head and Neck Cancer Patients

Radiotherapy and cisplatin-based chemotherapy belong to the main treatment modalities for head and neck squamous cell carcinoma (HNSCC) and induce cancer cell death by generating DNA damage, including the most severe double-strand breaks (DSBs). Alterations in DSB response and repair genes may affect individual DNA repair capacity and treatment sensitivity, contributing to the therapy resistance and poor prognosis often observed in HNSCC. In this study, we investigated the association of a panel of single-nucleotide polymorphisms (SNPs) in 20 DSB signaling and repair genes with therapy results and prognosis in 505 HNSCC patients treated non-surgically with DNA damage-inducing therapies. In the multivariate analysis, there were a total of 14 variants associated with overall, locoregional recurrence-free or metastasis-free survival. Moreover, we identified 10 of these SNPs as independent predictors of therapy failure and unfavorable prognosis in the whole group or in two treatment subgroups. These were MRE11 rs2155209, XRCC5 rs828907, RAD51 rs1801321, rs12593359, LIG4 rs1805388, CHEK1 rs558351, TP53 rs1042522, ATM rs1801516, XRCC6 rs2267437 and NBN rs2735383. Only CHEK1 rs558351 remained statistically significant after correcting for multiple testing. These results suggest that specific germline variants related to DSB response and repair may be potential genetic modifiers of therapy effects and disease progression in HNSCC treated with radiotherapy and cisplatin-based chemoradiation.

Arthrospira (Spirulina) platensis feeding reduces the early stage of chemically induced rat colon carcinogenesis

Colorectal cancer is the third most diagnosed cancer worldwide and linked to dietary/lifestyle factors. Arthrospira (Spirulina) platensis (AP) contains bioactive compounds with beneficial effects in vivo/in vitro. We evaluated the effects of AP feeding against 1,2-dimethylhydrazine (DMH)-induced colon carcinogenesis. Male Sprague Dawley rats were given subcutaneous injections of DMH (4 × 40 mg/kg body weight) (G1-G3) or vehicle (G4-G5) twice a week (weeks 3-4). During weeks 1-4, animals were fed a diet containing 1 % (G2) or 2 % (G3-G4) AP powder (w/w). After this period, all groups received a balanced diet until week 12. Some animals were euthanised after the last DMH injection (week 4) for histological, immunohistochemical (Ki-67, γ-H2AX and caspase-3) and molecular analyses (real time-PCR for 91 genes), while other animals were euthanised at week 12 for preneoplastic aberrant crypt foci (ACF) analysis. Both AP treatments (G2-G3) significantly decreased the DMH-induced increase in γ-H2AX (DNA damage) and caspase 3 (DNA damage-induced cell death) in colonic crypts at week 4. In addition, Cyp2e1 (Drug metabolism), Notch1, Notch2 and Jag1 genes (Notch pathway) and Atm, Wee1, Chek2, Mgmt, Ogg1 and Xrcc6 genes (DNA repair) were also down-regulated by 2 % AP feeding (G3) at week 4. A significant reduction in ACF development was observed in both AP-treated groups (G2-G3) at week 12. In conclusion, findings indicate that AP feeding reduced acute colonic damage after DMH, resulting in fewer preneoplastic lesions. Our study provided mechanistic insights on dietary AP-preventive effects against early colon carcinogenesis.

Association of Polymorphisms in NHEJ Pathway Genes with HIV-1 Infection and AIDS Progression in a Northern Chinese MSM Population

Background and Aims

Men who have sex with men (MSM) are at high risk of HIV infection. The nonhomologous end joining (NHEJ) pathway is the main way of double-stranded DNA break (DSB) repair in the higher eukaryotes and can repair the DSB timely at any time in cell cycle. It is also indicated that the NHEJ pathway is associated with HIV-1 infection since the DSB in host genome DNA occurs in the process of HIV-1 integration. The aim of the present investigation was to evaluate associations of single-nucleotide polymorphisms (SNPs) in NHEJ pathway genes with susceptibility to HIV-1 infection and AIDS progression among MSM residing in northern China.

Methods

A total of 481 HIV-1 seropositive men and 493 HIV-1 seronegative men were included in this case-control study. Genotyping of 22 SNPs in NHEJ pathway genes was performed using the SNPscan™ Kit.

Results

Positive associations were observed between XRCC6 rs132770 and XRCC4 rs1056503 genotypes and the susceptibility to HIV-1 infection. In gene-gene interaction analysis, significant SNP-SNP interactions of XRCC6 and XRCC4 genetic variations were found to play a potential role in the risk of HIV-1 infection. In stratified analysis, XRCC5 rs16855458 was significantly associated with CD4+ T cell counts in AIDS patients, whereas LIG4 rs1805388 was linked to the clinical phases of AIDS patients.

Conclusions

NHEJ gene polymorphisms can be considered to be risk factors of HIV-1 infection and AIDS progression in the northern Chinese MSM population.

Context-dependent functions of pattern recognition receptors in cancer

The immune system plays a critical role in shaping all facets of cancer, from the early initiation stage through to metastatic disease and resistance to therapy. Our understanding of the importance of the adaptive arm of the immune system in antitumour immunity has led to the implementation of immunotherapy with immune checkpoint inhibitors in numerous cancers, albeit with differing efficacy. By contrast, the clinical utility of innate immunity in cancer has not been exploited, despite dysregulated innate immunity being a feature of at least one-third of all cancers associated with tumour-promoting chronic inflammation. The past two decades have seen innate immune pattern recognition receptors (PRRs) emerge as critical regulators of the immune response to microbial infection and host tissue damage. More recently, it has become apparent that in many cancer types, PRRs play a central role in modulating a vast array of tumour-inhibiting and tumour-promoting cellular responses both in immune cells within the tumour microenvironment and directly in cancer cells. Herein, we provide a comprehensive overview of the fast-evolving field of PRRs in cancer, and discuss the potential to target PRRs for drug development and biomarker discovery in a wide range of oncology settings.

NRBF2 regulates the chemoresistance of small cell lung cancer by interacting with the P62 protein in the autophagy process

Reversing chemotherapy resistance in small cell lung cancer (SCLC) is crucial to improve patient prognosis. The present study aims to investigate the underlying mechanisms in SCLC chemoresistance. We see that nuclear receptor binding factor 2 (NRBF2) is a poor prognostic factor in SCLC. The effects of NRBF2 on chemoresistance were determined in SCLC. The underlying molecular mechanisms of NRBF2 in the autophagy process in SCLC were examined. NRBF2 positively regulated autophagy, leading to drug resistance in SCLC. The MIT domain of NRBF2 directly interacted with the PB1 domain of P62. This interaction increased autophagic P62 body formation, revealing the regulatory role of NRBF2 in autophagy. Notably, NRBF2 was directly modulated by the transcription factor XRCC6. The MIT domain of NRBF2 interacts with the PB1 domain of P62 to regulate the autophagy process, resulting in SCLC chemoresistance. NRBF2 is likely a useful chemotherapy response marker and therapeutic target in SCLC.

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NRBF2 promoted the chemoresistance of SCLC in vitro and in vivo

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The chemoresistance induced by NRBF2 was mediated via autophagy in SCLC

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NRBF2 interacting with P62 contributed to autophagic P62 bodies' formation

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NRBF2 was regulated by XRCC6 via direct binding to the NRBF2 gene promoter

Associations between AGT M235T Polymorphism and Cancer: An Updated Meta-Analysis

We assessed the relationship between AGT gene M235T polymorphism and the susceptibility to cancer by performing an updated meta-analysis. This study retrospectively searched related articles in the electronic databases. Afterwards, we determined combined odds ratios (ORs) and related 95% confidence intervals (CIs) by the fixed- or random-effects model. The present meta-analysis enrolled altogether 9 articles. On the whole, the relationship between AGT M235T polymorphism and the cancer risk was not significant among the entire population (TT vs. MM: OR = 1.28, 95%CI = 0.80 − 2.04; TM vs. MM: OR = 0.90, 95%CI = 0.53 − 1.52; recessive model: OR = 1.13, 95%CI = 0.83 − 1.52; dominant model: OR = 0.93, 95%CI = 0.55 − 1.57). Subgroup analysis by ethnicity, cancer type, and study quality for the relationship between the AGT M235T polymorphism and cancer risk showed no significant association. According to findings in the present meta-analysis, AGT M235T polymorphism may not be related to cancer susceptibility.

Genetic polymorphisms in DNA repair genes and hepatocellular carcinoma risk

Hepatocellular carcinoma (HCC) is one of the most frequent types of tumors worldwide. Its occurrence and development have been related to various risk factors, such as chronic infection with hepatitis B or C viruses and alcohol addiction. DNA repair systems play a critical role in maintaining the integrity of the genome. Defects in these systems have been related to increased susceptibility to various types of cancer. Multiple genetic polymorphisms in genes of DNA repair systems have been reported that may affect DNA repair capacity (DRC) and modulate risk to cancer. Several studies have been conducted to assess the role of polymorphisms of DNA repair genes on the HCC risk. Identifying these polymorphisms and their association with HCC risk may help to improve prevention and treatment strategies. In this study, we review investigations that evaluated the association between genetic polymorphisms of DNA repair genes and risk of HCC.

XRCC4 rs28360071 intronic variant is associated with increased risk for infant acute lymphoblastic leukemia with KMT2A rearrangements

Early age acute leukemia (EAL) shows a high frequency of KMT2A-rearrangements (KMT2A-r). Previous investigations highlighted double-strand breaks arising from maternal exposure to xenobiotics during pregnancy as a risk factor for EAL and KMT2A-r. In this case-control study, we investigated the relationship between EAL and genetic variants of the nonhomologous end-joining (XRCC6 rs5751129, XRCC4 rs6869366 and rs28360071), since they might affect DNA repair capacity, leading to KMT2A-r and leukemogenesis. Samples from 577 individuals (acute lymphoblastic leukemia-ALL, n=164; acute myeloid leukemia-AML, n=113; controls, n=300) were genotyped. No significant association was found for rs5751129 and rs6869366, whereas rs28360071 was associated with an increased risk for ALL with KMT2A-r (IIxID: OR - Odds ratio 2.23, CI 1.17-4.25, p=0.014). Bone marrow samples from ALL patients showed a higher expression of XRCC4 compared to AML patients (p=0.025). Human Splicing Finder 3.1 predicted that the deleted allele of rs28360071 is potentially associated with the activation of a 5’ cryptic splice site in intron 3 of XRCC4. The sequencing of cDNA did not show any differences on the splicing process for the rs28360071 genotypes. Our results suggest that the deleted allele for rs28360071 increases the risk for ALL with KMT2A-r, but not by modifying the XRCC4 expression levels or its structure.

Association between genetic polymorphism of XRCC6 T-991C and risk of varicocele

Background

The DNA non-homologous end-joining repair gene XRCC6 (Ku70) plays an essential role in the DNA double-strand break (DSB) repairs. Defects in the DSB repair pathway results in genomic instability. Varicocele is characterized by high pressure and stasis in the veins of the testis. There is little knowledge about the molecular mechanisms underlying varicocele. One of the reasons for increased spermatozoa DNA damage is high concentrations of reactive oxygen species (ROS), which leads to DNA-DSBs. We assumed that a promoter T-991C (rs5751129) polymorphism in the XRCC6 gene was associated with susceptibility to varicocele in infertile men. Therefore, 63 infertile varicocele men and 150 healthy controls were recruited in our study. The healthy controls had no history of varicocele, and they were matched with patients by age.

Results

Our results showed that infertile varicocele patients and control groups had significant differences in the distribution of their genotypic and allelic frequency (p = 0.00) in the XRCC6 promoter T-991C polymorphism. Men who carried CC genotype had a 5.22-fold increased odds ratio of developing infertile varicocele compared to those who carried the wild-type TT genotype (95% CI 2.31–11.81, P < 0.001).

Conclusions

Our results suggested that the CC genotype and the C allele in the promoter region of XRCC6 gene might play an important role in developing infertility in the varicocele men. Further research is needed to provide the effect of this polymorphism.

DNA-PK in human malignant disorders: Mechanisms and implications for pharmacological interventions

The DNA-PK holoenzyme is a fundamental element of the DNA damage response machinery (DDR), which is responsible for cellular genomic stability. Consequently, and predictably, over the last decades since its identification and characterization, numerous pre-clinical and clinical studies reported observations correlating aberrant DNA-PK status and activity with cancer onset, progression and responses to therapeutic modalities. Notably, various studies have established in recent years the role of DNA-PK outside the DDR network, corroborating its role as a pleiotropic complex involved in transcriptional programs that operate biologic processes as epithelial to mesenchymal transition (EMT), hypoxia, metabolism, nuclear receptors signaling and inflammatory responses. In particular tumor entities as prostate cancer, immense research efforts assisted mapping and describing the overall signaling networks regulated by DNA-PK that control metastasis and tumor progression. Correspondingly, DNA-PK emerges as an obvious therapeutic target in cancer and data pertaining to various pharmacological approaches have been published, largely in context of combination with DNA-damaging agents (DDAs) that act by inflicting DNA double strand breaks (DSBs). Currently, new generation inhibitors are tested in clinical trials. Several excellent reviews have been published in recent years covering the biology of DNA-PK and its role in cancer. In the current article we are aiming to systematically describe the main findings on DNA-PK signaling in major cancer types, focusing on both preclinical and clinical reports and present a detailed current status of the DNA-PK inhibitors repertoire.

Yeast-based assays for the functional characterization of cancer-associated variants of human DNA repair genes

Technological advances are continuously revealing new genetic variants that are often difficult to interpret. As one of the most genetically tractable model organisms, yeast can have a central role in determining the consequences of human genetic variation. DNA repair gene mutations are associated with many types of cancers, therefore the evaluation of the functional impact of these mutations is crucial for risk assessment and for determining therapeutic strategies. Owing to the evolutionary conservation of DNA repair pathways between human cells and the yeast Saccharomyces cerevisiae, several functional assays have been developed. Here, we describe assays for variants of human genes belonging to the major DNA repair pathways divided in functional assays for human genes with yeast orthologues and human genes lacking a yeast orthologue. Human genes with orthologues can be studied by introducing the correspondent human mutations directly in the yeast gene or expressing the human gene carrying the mutations; while the only possible approach for human genes without a yeast orthologue is the heterologous expression. The common principle of these approaches is that the mutated gene determines a phenotypic alteration that can vary according to the gene studied and the domain of the protein. Here, we show how the versatility of yeast can help in classifying cancer-associated variants.

Associations between genetic polymorphisms in interleukin-10 and hematological oncology: evidence from a meta-analysis

Background: Associations between polymorphisms in interleukin-10 (IL-10) and hematological oncology were already explored by many genetic association studies, with controversial findings. The aim of this meta-analysis was to more comprehensively analyze associations between polymorphisms in IL-10 and hematological oncology by combing the results of all relevant studies.Methods: Eligible articles were searched from Pubmed, Embase, WOS and CNKI. The latest literature searching update was performed on 8 October 2019. We used Review Manager to combine the results of eligible studies.Results: Forty-one articles were included in this meta-analysis. IL-10 rs1800890 polymorphism was found to be significantly associated with hematological oncology under AA vs. TT+TA (recessive comparison, OR = 1.12, 95% CI 1.02-1.24), and rs1800896 polymorphism was also found to be significantly associated with hematological oncology under AA vs. AG+GG (dominant comparison, OR = 0.89, 95% CI 0.83-0.95) in overall combined analyses. In subgroup analyses, we observed positive results for rs1800871 (recessive comparison), rs1800872 (dominant, recessive and allele comparisons), and rs1800896 (dominant and allele comparisons) polymorphisms in the non-Hodgkin's lymphoma (NHL) subgroup. Besides, we also detected positive associations between rs1800872 polymorphism and acute leukemia (AL) (dominant and recessive comparisons) and found significant associations between rs1800896 polymorphism and chronic leukemia (CL) (recessive comparison).Conclusion: In summary, this meta-analysis demonstrated that IL-10 rs1800890, rs1800896, rs1800871 and rs1800872 polymorphisms may confer susceptibility to hematology oncology, especially for NHL.

A meta-analysis of the relationship between paraoxonase 1 polymorphisms and cancer

Some previous studies already explored associations between paraoxonase 1 (PON1) polymorphisms and cancer, with conflicting findings. Here, we aimed to better analyse the relationship between PON1 polymorphisms and cancer in a larger combined population by performing a meta-analysis. We searched PubMed, Embase, and Web of Science for related articles. We calculated odds ratio (OR) and 95% confidence interval (CI) to estimate whether there are genetic associations between PON1 polymorphisms and cancer. Forty studies were included for this meta-analysis. The PON1 rs854560 polymorphism (L55M) was found to be significantly associated with cancer in general population (dominant comparison: p = .04, OR = 0.85, 95%CI 0.73-0.99; recessive comparison: p = .007, OR = 1.27, 95%CI 1.07-1.51; allele comparison: p = 0.02, OR = 0.85, 95%CI 0.75-0.97). Subgroup analyses indicated that the significant findings were mainly driven by the haematological tumours and breast cancer subgroups. We did not observe any positive findings for PON1 rs662 polymorphism (Q192R) in combined analyses. In summary, this meta-analysis proved that PON1 rs854560 polymorphism could be used to identify individual with elevated susceptibility to cancer, especially for haematological tumours and breast cancer.

Association of angiotensin ІІ type 1 receptor gene A1166C polymorphism with cancer risk: An updated meta-analysis

Objective:

The association between angiotensin II type 1 receptor (AGTR1) gene A1166C polymorphism and cancer risk has been investigated in many studies. However, the results have been inconclusive. A meta-analysis was performed to obtain a more precise estimation of the relationship.

Methods:

The PubMed and China National Knowledge Infrastructure databases were searched for published literature. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strengths of association.

Results:

Ten studies, including 1553 patients and 1904 controls, were included in the meta-analysis. Overall, there were no significant associations between the AGTR1 gene A1166C polymorphism and cancer risk in the general population (CC vs AA: OR = 1.09, 95% CI = 0.50–2.37; AC vs AA: OR = 1.54, 95% CI = 0.81–2.91; dominant model: OR = 1.46, 95% CI = 0.77–2.79; recessive model: OR = 1.12, 95% CI = 0.84–1.49). In a subgroup analysis by nationality and cancer type, the results also showed no association between this polymorphism and cancer risk.

Conclusions:

This meta-analysis demonstrated that the AGTR1 gene A1166C polymorphism does not appear to be related to the risk of cancer.

Four polymorphisms in the IL-22 gene and the risk of cancer: A meta-analysis

OBJECTIVE

IL-22 plays an important role in cancer carcinogenesis. However, the association between IL-22 polymorphisms and cancer risk was inconclusive. The objective of the current study was to assess these associations by meta-analysis.

METHODS

PubMed, EMbase, CNKI, VIP, and Wanfang databases were searched up to 31 January 2018. The results were screened according to the inclusion and exclusion criteria. The associations between polymorphisms and cancer risk were estimated by meta-analysis. All analyses were performed using the Revman5.3 software.

RESULTS

A total of four polymorphisms (rs2227485, rs1179251, rs1179246, and rs1182844) in seven studies were included. The results of meta-analysis indicated that the rs1179251 polymorphism [OR = 1.46, 95% CI (1.17, 1.82), P = 0.0008 for GG+GC vs. CC] was associated with increased risk of cancer, while the rs2227485, rs1179246, and rs1182844 polymorphisms were not associated with cancer risk.

CONCLUSIONS

The current meta-analysis suggests that IL-22 gene rs1179251 polymorphism may be a risk factor for cancer.

Role of polymorphic XRCC6 (Ku70)/XRCC7 (DNA-PKcs) genes towards susceptibility and prognosis of lung cancer patients undergoing platinum based doublet chemotherapy

The DNA repair genes XRCC6 and XRCC7 formed an integral part of double strand break repair (DSBR) pathway. The two genes are thought to play an important role in the repair of lethal double strand damage on DNA. Polymorphic DSBR genes are studied to effect genomic stability. We intend to explore the association of DSBR genes i.e. XRCC6 and XRCC7 with susceptibility and survival in North Indian lung cancer patients. DNA isolation and genotyping was done for 320 controls and 330 lung cancer cases enrolled in the study. Each and every lung cancer study subjects were made a telephonic call and were followed for their health after administration of chemotherapy. Statistical analysis for susceptibility was done using logistic regression analysis. Survival analysis was done using Kaplan-Meier followed by Cox-regression. Small cell lung cancer (SCLC) subtype posed an amplified risk towards lung cancer in case of XRCC7 6721G>T (OR = 4.11, p = 0.0040). Gene-environment interaction analysis revealed that non-smokers with heterozygous genotype (CG) in case of XRCC6 61C>G showed a strong protective effect (OR = 0.38, p = 0.01) towards lung cancer. Survival analysis revealed poor prognosis in case of XRCC6 61C>G SCLC subtype. XRCC6 and XRCC7 were not involved in overall susceptibility and survival. However, in case of XRCC7 6721G>T subjects with SCLC subtype showed an increased susceptibility while poor prognosis in case of XRCC6 61C>G.

Transcriptional signature of lymphoblastoid cell lines of BRCA1, BRCA2 and non-BRCA1/2 high risk breast cancer families

Approximately 25% of hereditary breast cancer cases are associated with a strong familial history which can be explained by mutations in BRCA1 or BRCA2 and other lower penetrance genes. The remaining high-risk families could be classified as BRCAX (non-BRCA1/2) families.

Gene expression involving alternative splicing represents a well-known mechanism regulating the expression of multiple transcripts, which could be involved in cancer development. Thus using RNA-seq methodology, the analysis of transcriptome was undertaken to potentially reveal transcripts implicated in breast cancer susceptibility and development.

RNA was extracted from immortalized lymphoblastoid cell lines of 117 women (affected and unaffected) coming from BRCA1, BRCA2 and BRCAX families. Anova analysis revealed a total of 95 transcripts corresponding to 85 different genes differentially expressed (Bonferroni corrected p-value <0.01) between those groups. Hierarchical clustering allowed distinctive subgrouping of BRCA1/2 subgroups from BRCAX individuals. We found 67 transcripts, which could discriminate BRCAX from BRCA1/BRCA2 individuals while 28 transcripts discriminate affected from unaffected BRCAX individuals.

To our knowledge, this represents the first study identifying transcripts differentially expressed in lymphoblastoid cell lines from major classes of mutation-related breast cancer subgroups, namely BRCA1, BRCA2 and BRCAX. Moreover, some transcripts could discriminate affected from unaffected BRCAX individuals, which could represent potential therapeutic targets for breast cancer treatment.

The Role of the Core Non-Homologous End Joining Factors in Carcinogenesis and Cancer

DNA double-strand breaks (DSBs) are deleterious DNA lesions that if left unrepaired or are misrepaired, potentially result in chromosomal aberrations, known drivers of carcinogenesis. Pathways that direct the repair of DSBs are traditionally believed to be guardians of the genome as they protect cells from genomic instability. The prominent DSB repair pathway in human cells is the non-homologous end joining (NHEJ) pathway, which mediates template-independent re-ligation of the broken DNA molecule and is active in all phases of the cell cycle. Its role as a guardian of the genome is supported by the fact that defects in NHEJ lead to increased sensitivity to agents that induce DSBs and an increased frequency of chromosomal aberrations. Conversely, evidence from tumors and tumor cell lines has emerged that NHEJ also promotes chromosomal aberrations and genomic instability, particularly in cells that have a defect in one of the other DSB repair pathways. Collectively, the data present a conundrum: how can a single pathway both suppress and promote carcinogenesis? In this review, we will examine NHEJ's role as both a guardian and a disruptor of the genome and explain how underlying genetic context not only dictates whether NHEJ promotes or suppresses carcinogenesis, but also how it alters the response of tumors to conventional therapeutics.

Digital gene expression profiling analysis of DNA repair pathways in colon cancer stem population of HT29 cells

Cancer stem cells (CSCs) contribute to the relapse and development of new neoplasm lesions. While most available clinical approaches, such as chemical and radiation therapies, will kill the majority of cancer cells, they do not kill them all. Some resisting cells, like CSCs, are able to survive due to their excellent self-maintaining capabilities, even in challenging environments. In the present study, we investigated the mRNA level of DNA repair genes of colon CSCs from the HT29 cell line in response to single-strand damage and double-strand breaks, as well as the evident upregulation of key genes in base excision repair, mismatch repair, non-homologous end-joining, and homologous recombination pathways in these cells. Digital gene expression analysis identified upregulated genes in CD44⁺ HT29 cells that may play important roles in DNA repair. Our results reveal that colon CSCs bear efficient DNA repair abilities, which might explain the survival of colon CSCs after repeated chemical and radiation therapy.

XRCC5 VNTR, XRCC6 -61C>G, and XRCC7 6721G>T Gene Polymorphisms Associated with Male Infertility Risk: Evidences from Case-Control and In Silico Studies

We evaluate the association between genetic polymorphisms of XRCC5 VNTR, XRCC6 -61C>G, and XRCC7 6721G>T with male infertility susceptibility. A total of 392 men including 178 infertile males (102 idiopathic azoospermia and 76 severe oligozoospermia) and 214 healthy controls were recruited. XRCC6 -61C>G and XRCC7 6721G>T genotyping was performed by PCR-RFLP whereas XRCC5 VNTR was performed by PCR. The 2R allele and 2R allele carriers of XRCC5 VNTR polymorphism significantly decreased risk of male infertility. The mutant GG genotypes and carriers of the CG and GG genotypes of XRCC6 -61C>G showed increased risk for the male infertility. Furthermore, the G allele of the XRCC6 -61C>G was correlated with increased susceptibility to male infertility. Likewise, the T allele of the XRCC7 6721G>T polymorphism was associated with increased susceptibility to male infertility in azoospermia. In silico analysis predicted that the presence of tandem repeats in XRCC5 gene prompter can be sequence to bind to more nuclear factors. Also, rs2267437 (C>G) variant was located in a well-conserved region in XRCC6 promoter and this variation might lead to differential allelic expression. The XRCC7 6721G>T gene polymorphism occurred in an acceptor-splicing site, but this polymorphism has no severe modification on XRCC7 mRNA splicing. Our results indicate the association of XRCC5 VNTR, XRCC6 -61C>G, and XRCC7 6721G>T gene polymorphisms with male infertility in Iranian men.

Association between single-nucleotide polymorphisms in DNA double-strand break repair genes and prostate cancer aggressiveness in the Spanish population

BACKGROUND

Novel predictors of prognosis and treatment response for prostate cancer (PCa) are required to better individualize treatment. Single-nucleotide polymorphisms (SNPs) in four genes directly (XRCC5 (X-ray repair complementing defective repair in Chinese hamster cells 5) and XRCC6 (X-ray repair complementing defective repair in Chinese hamster cells 6)) or indirectly (PARP1 and major vault protein (MVP)) involved in non-homologous end joining were examined in 494 Spanish PCa patients.

METHODS

A total of 22 SNPs were genotyped in a Biotrove OpenArray NT Cycler. Clinical tumor stage, diagnostic PSA serum levels and Gleason score at diagnosis were obtained for all participants. Genotypic and allelic frequencies were determined using the web-based environment SNPator.

RESULTS

(XRCC6) rs2267437 appeared as a risk factor for developing more aggressive PCa tumors. Those patients carrying the GG genotype were at higher risk of developing bigger tumors (odds ratio (OR)=2.04, 95% confidence interval (CI) 1.26-3.29, P=0.004), present higher diagnostic PSA levels (OR=2.12, 95% CI 1.19-3.78, P=0.011), higher Gleason score (OR=1.65, 95% CI 1.01-2.68, P=0.044) and D'Amico higher risk tumors (OR=2.38, 95% CI 1.24-4.58, P=0.009) than those patients carrying the CC/CG genotypes. Those patients carrying the (MVP) rs3815824 TT genotype were at higher risk of presenting higher diagnostic PSA levels (OR=4.74, 95% CI 1.40-16.07, P=0.013) than those patients carrying the CC genotype. When both SNPs were analyzed in combination, those patients carrying the risk genotypes were at higher risk of developing D'Amico higher risk tumors (OR=3.33, 95% CI 1.56-7.17, P=0.002).

CONCLUSIONS

We believe that for the first time, genetic variants at XRCC6 and MVP genes are associated with risk of more aggressive disease, and would be taken into account when assessing the malignancy of PCa.

The catalase C-262T gene polymorphism and cancer risk: a systematic review and meta-analysis

Many studies suggest that catalase C-262T gene polymorphism is associated with cancer risk, but with inconsistent results. This study aimed to summarize the overall association between catalase C-262T polymorphism and cancer risk. Literature search was performed in PubMed, Embase, and other databases, studies regarding the association between catalase C-262T polymorphism and cancer risk were identified, and data were retrieved and analyzed by using Review Manager 5.0.24 and STATA 12.0. A total of 18 publications with 22 case-control studies, including 9777 cancer patients and 12,223 controls, met the inclusion criteria. Meta-analysis results showed significant association between catalase C-262 T polymorphism and cancer risk (TT vs CT + CC: odds ratio [OR] = 1.17, 95% confidence interval [CI] = 1.03-1.31, P = 0.01). Subgroup analyses stratified by cancer types suggested the catalase C-262T polymorphism was significantly associated with an increased prostate cancer risk (TT vs CT + CC: OR = 1.61, 95% CI = 1.17-2.22, P = 0.004); for subgroup analyses stratified by ethnicity, no associations between this polymorphism and Asians or whites were identified (CT + TT vs CC: OR = 1.11, 95% CI = 0.98-1.26, P = 0.09 for whites; OR = 1.19, 95% CI = 0.78-1.80, P = 0.42 for Asians). In summary, the catalase C-262T polymorphism may be a risk factor for cancer with cancer type-specific effects. Further studies should be performed to confirm these findings.