Loss of heterozygosity and lack of mutations of the XPG/ERCC5 DNA repair gene at 13q33 in prostate cancer

MiR-15a/miR-16-1 expression inversely correlates with cyclin D1 levels in Men1 pituitary NETs

Multiple Endocrine Neoplasia type 1 (MEN1) is an autosomal dominant disorder characterised by the combined occurrence of parathyroid, pituitary and pancreatic islet tumours, and is due to mutations of the MEN1 gene, which encodes the tumour suppressor protein menin. Menin has multiple roles in genome stability, transcription, cell division and proliferation, but its mechanistic roles in tumourigenesis remain to be fully elucidated. MicroRNAs (miRNA) are non-coding single stranded RNAs that post-transcriptionally regulate gene expression and have been associated with tumour development, although the contribution of miRNAs to MEN1-associated tumourigenesis and their relationship with menin expression are not fully understood. Alterations in miRNA expression, including downregulation of three putative 'tumour suppressor' miRNAs, miR-15a, miR-16-1 and let-7a, have been reported in several tumour types including non-MEN1 pituitary adenomas. We have therefore investigated the expression of miR-15a, miR-16-1 and let-7a in pituitary tumours that developed after 12 months of age in female mice with heterozygous knock out of the Men1 gene (Men1+/- mice). The miRNAs miR-15a, miR-16-1 and let-7a were significantly downregulated in pituitary tumours (by 2.3-fold, p<0.05; 2.1-fold p<0.01 and 1.6-fold p<0.05, respectively) of Men1+/- mice, compared to normal wild type pituitaries. MiR-15a and miR-16-1 expression inversely correlated with expression of cyclin D1, a known pro-tumourigenic target of these miRNAs, and knock down of menin in a human cancer cell line (HeLa), and AtT20 mouse pituitary cell line resulted in significantly decreased expression of miR-15a (p<0.05), indicating that the decrease in miR-15a may be a direct result of lost menin expression.

Polymorphisms in ERCC2 and ERCC5 and Risk of Prostate Cancer: A Meta-Analysis and Systematic Review

Background and Objective: Excision repair cross complementing (ERCC) group genes play important roles in the nucleotide excision repair (NER) way, which can effectively remove bulky lesions and reduce UV-caused DNA damage by environmental chemicals. Polymorphisms in ERCCs were thought to be related to prostate cancer (PCa) risk. However, it has been unclear whether this relationship is consistent. This study aimed to obtain the overall profile regarding the associations between ERCCs polymorphisms and PCa risk. Materials and Methods: We identified relevant studies by a systematic search of PubMed, Medline, Embase, Google Scholar databases, Web of Science and Wanfang databases up to April 8, 2018. Odds ratios (ORs) with 95% confidential intervals (95%CIs) were conducted to evaluate the associations. All the statistical analyses were conducted basing on STATA 12.0 software. Results: Finally, a total of 29 previous studies published in 17 publications were included for four polymorphisms in two DNA repair genes (ERCC2-rs1799793, ERCC2-rs238406, ERCC2-rs13181 and ERCC5-rs17655). Overall, we observed no significant connection between these four polymorphisms and PCa risk. However, after stratifying the studies by ethnicity, ERCC2-rs1799793 polymorphism was associated with an increased risk of PCa in Asian patients and the relationship was subsequently validated with the allelic model, the homozygous model and the recessive model when extracting the data of Asian patients for specific analyses (B vs. A: OR = 1.537, 95%CI: 1.240-1.906, PA< 0.001; BB vs. AA: OR = 2.089, 95%CI: 1.388-3.145, PA< 0.001 and BB vs. BA + AA: OR = 1.929, 95%CI: 1.313-2.835, PA= 0.020). Furthermore, subgroup analyses were also conducted by Hardy-Weinberg Equilibrium (HWE) and source of control, negative results were identified for ERCC2-rs238406, ERCC2-rs13181 and ERCC5-rs17655 polymorphisms (PA> 0.050). Conclusion: To sum up, our work demonstrated that ERCC2-rs1799793 polymorphism is positively associated with PCa risk in Asian population. Further larger-scale studies with subjects of the same ethnicity and biological characteristics are required to verify these findings.

Role of DNA repair-related gene polymorphisms in susceptibility to risk of prostate cancer

AIM

We assessed the association between genetic variants of XPG, XPA, XPD, CSB, XPC and CCNH in the nucleotide excision repair (NER) pathway and risk of prostate cancer.

METHODS

We genotyped the XPG, XPA, XPD, CSB, XPC and CCNH polymorphisms by a 384-well plate format on the MassARRAY® platform. Multivariate logistical regression analysis was used to assess the associations between the six gene polymorphisms and risk of prostate cancer.

RESULTS

Individuals carrying the XPG rs229614 TT (OR=2.01, 95%CI=1.35-3.27) genotype and T allele (OR=1.73, 95%CI=1.37-2.57) were moderately significantly associated with a higher risk of prostate cancer. Subjects with XPD rs13181 G allele had a marginally increased risk of prostate cancer, with adjusted OR(95%CI) of 1.53 (1.04-2.37). Moreover, individuals carrying with CSB rs2228526 GG genotype (OR=2.05, 95% CI=1.23-3.52) and G allele (OR=1.56, 95%CI=1.17-2.05) were associated with a higher increased risk of prostate cancer. The combination genotype of XPG rs2296147 T and CSB rs2228526 G allele had accumulative effect on the risk of this cancer, with an OR (95% CI) of 2.23(1.37-3.59).

CONCLUSIONS

Our study indicates that XPG rs2296147 and CSB rs2228526 polymorphisms are significantly associated with increased risk of prostate cancer, and that combination of XPG rs2296147 T allele and CSB rs2228526 G allele is strongly associated with an increased risk.

DNA repair genes polymorphism (XPG and XRCC1) and association of prostate cancer in a north Indian population

Prostate cancer is the most commonly diagnosed cancer in men worldwide and is the second leading cause of cancer related mortality. Genetic background may account for the difference in susceptibility of individuals to different diseases and the relationship between genetic polymorphism and some diseases has been extensively studied. There are several common polymorphisms in genes encoding DNA repair enzymes, some of these polymorphisms are reported to result in subtle structural alterations of the repair enzyme and modulation of the repair capacity. The aim of the present study was to analyze the effect of XPG Asp 1104His and XRCC1 Arg309Gln polymorphisms on risk of prostate cancer in north Indian population. Statistically significant increased risk of prostate cancer was observed on individuals that posses His/His genotype of XPG (OR 2.53, 95% CI 0.99-6.56, P = 0.031). In this study 150 prostate cancer diagnosed patients, 150 healthy controls and 150 BPH (benign prostate hyper plasia) were recruited from north Indian population. Moreover, individuals that carried the Gln/Gln genotype of XRCC1 also showed statistically increased risk of prostate cancer (OR 2.06, 95% CI 1.07-4.00, P = 0.033). The Asp/Asp of XPG and Gln/Gln of XRCC1 in combination showed statistically increased risk of prostate cancer in cases (OR 3.29, 95% CI 1.09-10.16, P = 0.032).

Cis-acting genetic variation at an E2F1/YY1 response site and putative p53 site is associated with altered allele-specific expression of ERCC5 (XPG) transcript in normal human bronchial epithelium

ERCC5 (XPG) is a key component of the nucleotide excision DNA repair pathway. In two recent case-control studies, we determined that ERCC5 transcript expression pattern in grossly normal human bronchial epithelial cells (NBEC) was different in individuals diagnosed with lung cancer compared with non-lung cancer controls. In this study, we tested the hypothesis that variation at cis-acting sites contributed to observed variation in ERCC5 transcript expression in NBEC. Allele-specific expression (ASE) was measured at transcribed polymorphic site rs1047768 in exon 2 of ERCC5 in NBEC complementary DNA (cDNA) of 22 individuals using allele-specific competitive polymerase chain reaction. ASE at rs1047768 was then assessed for association with allelotype at polymorphic sites rs751402 (E2F1 and YY1 recognition and response site) and rs2296147 (putative P53 recognition site) in the proximal promoter and 5' untranslated region, respectively, of ERCC5. Interindividual variation in recombination between rs751402, rs2296147 and rs1047768 in poly-heterozygotes was controlled for by allele-specific sequencing. Measured rs1047768 T:C allelic ratio was (i) significantly higher in NBEC cDNA compared with genomic DNA controls (P < 0.001) among samples heterozygous at both rs751402 and rs2296147; (ii) less high (P = 0.02) for samples homozygous at rs751402 but heterozygous at rs2296147 and (iii) not significantly different (P = 0.18) for doubly homozygous individuals. Here, we demonstrate that rs751402 A allele and rs2296147 T allele are associated with higher ASE of ERCC5 T allele transcript at rs1047768 in NBEC.

NAT2 and NER genetic variants and sporadic prostate cancer susceptibility in African Americans

Prostate cancer is a common malignancy that disproportionately affects African-American men. Environmental factors and variation in genes responsible for chemical and dietary carcinogen metabolism and DNA damage repair may modulate risk. Fourteen single nucleotide polymorphisms in NAT2 and four NER genes (ERCC1, XPF/ERCC4, XPG/ERCC5 and CSB/ERCC6) were genotyped in a case-control study of 254 African-American prostate cancer cases and 301 healthy controls from Washington, DC. Smoking status, BMI, age and genetic ancestry were included as covariates in the association analyses. We found that individuals homozygous for the XPG/ERCC5 -72C/T promoter polymorphism had a significant reduction in risk, for prostate cancer (OR=0.12; 95% CI=0.03-0.48). A haplotype trend regression test also revealed a protective effect for the haplotype bearing the T allele (P=0.003). In silica analyses suggest a functional implication for the promoter variant since it deletes a GCF transcriptional factor-binding site responsible for the downregulation of transcription. The protective effect of the promoter SNP on risk for prostate cancer was independent of smoking. In contrast, none of the SNPs typed for NAT2, ERCC1, ERCC4 and ERCC6 showed significant association with risk. Additional tests for genotype interactions were not significant. We note that there may be other factors, such as dietary exposures, which may modulate prostate cancer risk in combination with genetic variation within the NAT2 and NER genes. Our results, in combination with previous observations of LOH for ERCC5 in prostate tumors, provide further evidence for a role of XPG/ERCC5 in the etiology of prostate cancer.

Pattern of sequence variation across 213 environmental response genes

To promote the clinical and epidemiological studies that improve our understanding of human genetic susceptibility to environmental exposure, the Environmental Genome Project (EGP) has scanned 213 environmental response genes involved in DNA repair, cell cycle regulation, apoptosis, and metabolism for single nucleotide polymorphisms (SNPs). Many of these genes have been implicated by loss-of-function mutations associated with severe diseases attributable to decreased protection of genomic integrity. Therefore, the hypothesis for these studies is that individuals with functionally significant polymorphisms within these genes may be particularly susceptible to genotoxic environmental agents. On average, 20.4 kb of baseline genomic sequence or 86% of each gene, including a substantial amount of introns, all exons, and 1.3 kb upstream and downstream, were scanned for variations in the 90 samples of the Polymorphism Discovery Resource panel. The average nucleotide diversity across the 4.2 MB of these 213 genes is 6.7 x 10(-4), or one SNP every 1500 bp, when two random chromosomes are compared. The average candidate environmental response gene contains 26 PHASE inferred haplotypes, 34 common SNPs, 6.2 coding SNPs (cSNPs), and 2.5 nonsynonymous cSNPs. SIFT and Polyphen analysis of 541 nonsynonymous cSNPs identified 57 potentially deleterious SNPs. An additional eight polymorphisms predict altered protein translation. Because these genes represent 1% of all known human genes, extrapolation from these data predicts the total genomic set of cSNPs, nonsynonymous cSNPs, and potentially deleterious nonsynonymous cSNPs. The implications for the use of these data in direct and indirect association studies of environmentally induced diseases are discussed.

Antitumor activity of irofulven monotherapy and in combination with mitoxantrone or docetaxel against human prostate cancer models

BACKGROUND

Irofulven (6-hydroxymethylacylfulvene, HMAF, MGI 114) is a novel antitumor agent currently undergoing clinical trials in hormone-refractory prostate cancer. This report examines the efficacy of irofulven alone or in combination with mitoxantrone or docetaxel against androgen-independent prostate cancer cell lines.

METHODS

To elucidate the activity of irofulven monotherapy and in combination, PC-3 and DU-145 cell lines were utilized in cellular viability assessments and tumor growth inhibition studies.

RESULTS

Viability assays with irofulven and mitoxantrone show additive to synergistic activity. Furthermore, irofulven and mitoxantrone in combination exhibit enhanced antitumor activity against PC-3 and DU-145 xenografts. Additive combination effects are also observed when irofulven and docetaxel were tested against PC-3 xenografts and curative activity (8/10 CR) is observed in DU-145 xenografts.

CONCLUSIONS

These studies demonstrate that irofulven displays strong activity as monotherapy and in combination with mitoxantrone or docetaxel against androgen-independent prostate cancer in vitro and in vivo; thus, supporting the clinical investigation of irofulven against hormone-refractory prostate cancer.

Polymorphisms in the DNA repair enzyme XPD are associated with increased levels of PAH-DNA adducts in a case-control study of breast cancer

We present findings on the associations between DNA adduct levels in breast tissue, risk of breast cancer, and polymorphisms in the DNA repair enzyme XPD. Breast cancer cases, benign breast disease (BBD) controls, and healthy controls were enrolled. Polycyclic aromatic hydrocarbons (PAH)-DNA adduct levels were measured by immunohistochemistry in breast tissue samples from cases and BBD controls. XPD polymorphisms at codons 312 and 751 was determined by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analysis using white blood cell DNA. Neither of the polymorphisms were associated with case-control status, both in comparisons of cases and BBD controls, and cases and healthy controls. XPD polymorphisms at codons 312 and 751 were associated with higher levels of PAH-DNA in tumor tissue from breast cancer cases. Subjects with an Asp/Asn or Asn/Asn polymorphic genotype in codon 312 of XPD had elevated levels of PAH-DNA adducts compared to subjects with the Asp/Asp genotype (0.55 optical density (OD) v.s. 0.33 OD, p < 0.01). PAH-DNA adducts were associated with increasing copy number of the Gln allele for the codon 751 polymorphism (p for trend <0.01). Among subjects with the Asp/Asn or Asn/Asn genotype at codon 312, adduct levels were higher in tumor tissue compared to tissue from BBD controls (0.55 OD v.s. 0.36 OD, p = 0.003). Among subjects with the Gln/Gln genotype at codon 751 adduct levels were higher in tumor tissue compared to tissue from BBD controls (0.68 OD v.s. 0.40 OD, p = 0.01). The trend of increasing PAH-DNA adduct levels with either the Asn/Asn or Gln/Gln genotype was greater in tumor tissue than the trend in BBD control tissue.

Impaired nonhomologous end-joining provokes soft tissue sarcomas harboring chromosomal translocations, amplifications, and deletions

Although nonhomologous end-joining (NHEJ) deficiency has been shown to accelerate lymphoma formation in mice, its role in suppressing tumors in cells that do not undergo V(D)J recombination is unclear. Utilizing a tumor-prone mouse strain (ink4a/arf(-/-)), we examined the impact of haploinsufficiency of a NHEJ component, DNA ligase IV (Lig4), on murine tumorigenesis. We demonstrate that lig4 heterozygosity promotes the development of soft-tissue sarcomas that possess clonal amplifications, deletions, and translocations. That these genomic alterations are relevant in tumorigenesis is supported by the finding of frequent mdm2 amplification, a known oncogene in human sarcoma. Together, these findings support the view that loss of a single lig4 allele results in NHEJ activity being sufficiently reduced to engender chromosomal aberrations that drive non-lymphoid tumorigenesis.

The human XPG gene: gene architecture, alternative splicing and single nucleotide polymorphisms

Defects in the XPG DNA repair endonuclease gene can result in the cancer-prone disorders xeroderma pigmentosum (XP) or the XP-Cockayne syndrome complex. While the XPG cDNA sequence was known, determination of the genomic sequence was required to understand its different functions. In cells from normal donors, we found that the genomic sequence of the human XPG gene spans 30 kb, contains 15 exons that range from 61 to 1074 bp and 14 introns that range from 250 to 5763 bp. Analysis of the splice donor and acceptor sites using an information theory-based approach revealed three splice sites with low information content, which are components of the minor (U12) spliceosome. We identified six alternatively spliced XPG mRNA isoforms in cells from normal donors and from XPG patients: partial deletion of exon 8, partial retention of intron 8, two with alternative exons (in introns 1 and 6) and two that retained complete introns (introns 3 and 9). The amount of alternatively spliced XPG mRNA isoforms varied in different tissues. Most alternative splice donor and acceptor sites had a relatively high information content, but one has the U12 spliceosome sequence. A single nucleotide polymorphism has allele frequencies of 0.74 for 3507G and 0.26 for 3507C in 91 donors. The human XPG gene contains multiple splice sites with low information content in association with multiple alternatively spliced isoforms of XPG mRNA.