Comprehensive analysis of DNA repair gene variants and risk of meningioma

Scrutinizing Deleterious Nonsynonymous SNPs and Their Effect on Human POLD1 Gene

POLD1 (DNA polymerase delta 1, catalytic subunit) is a protein-coding gene that encodes the large catalytic subunit (POLD1/p125) of the DNA polymerase delta (Polδ) complex. The consequence of missense or nonsynonymous SNPs (nsSNPs), which occur in the coding region of a specific gene, is the replacement of single amino acid. It may also change the structure, stability, and/or functions of the protein. Mutation in the POLD1 gene is associated with autosomal dominant predisposition to colonic adenomatous polyps, colon cancer, endometrial cancer (EDMC), breast cancer, and brain tumors. These de novo mutations in the POLD1 gene also result in autosomal dominant MDPL syndrome (mandibular hypoplasia, deafness, progeroid features, and lipodystrophy). In this study, genetic variations of POLD1 which may affect the structure and/or function were analyzed using different types of bioinformatics tools. A total of 17038 nsSNPs for POLD1 were collected from the NCBI database, among which 1317 were missense variants. Out of all missense nsSNPs, 28 were found to be deleterious functionally and structurally. Among these deleterious nsSNPs, 23 showed a conservation scale of >5, 2 were predicted to be associated with binding site formation, and one acted as a posttranslational modification site. All of them were involved in coil, extracellular structures, or helix formation, and some cause the change in size, charge, and hydrophobicity.

Past medical history of tumors other than meningioma is a negative prognostic factor for tumor recurrence in meningiomas WHO grade I

Background

Prognostic markers for meningioma recurrence are needed to guide patient management. Apart from rare hereditary syndromes, the impact of a previous unrelated tumor disease on meningioma recurrence has not been described before.

Methods

We retrospectively searched our database for patients with meningioma WHO grade I and complete resection provided between 2002 and 2016. Demographical, clinical, pathological, and outcome data were recorded. The following covariates were included in the statistical model: age, sex, clinical history of unrelated tumor disease, and localization (skull base vs. convexity). Particular interest was paid to the patients’ past medical history. The study endpoint was date of tumor recurrence on imaging. Prognostic factors were obtained from multivariate proportional hazards models.

Results

Out of 976 meningioma patients diagnosed with a meningioma WHO grade I, 416 patients fulfilled our inclusion criteria. We encountered 305 women and 111 men with a median age of 57 years (range: 21–89 years). Forty-six patients suffered from a tumor other than meningioma, and no TERT mutation was detected in these patients. There were no differences between patients with and without a positive oncological history in terms of age, tumor localization, or mitotic cell count. Clinical history of prior tumors other than meningioma showed the strongest association with meningioma recurrence (p = 0.004, HR = 3.113, CI = 1.431–6.771) both on uni- and multivariate analysis.

Conclusion

Past medical history of tumors other than meningioma might be associated with an increased risk of meningioma recurrence. A detailed pre-surgical history might help to identify patients at risk for early recurrence.

Pregnancy and brain tumors; a systematic review of the literature

The incidence of primary brain tumors during pregnancy is uncommon. The etiology of these can range from different genetic syndromes such as Li Fraumeni, neurofibromatosis type I, and hormonal associated tumors. The number of meningiomas gradually tends to increase during pregnancy, suggesting a relationship between non-malignant meningiomas and hormonal changes. Clinical features are non specific or can be misinterpreted with pregnancy symptoms such as headache, vomiting and dizziness. It is worth mentioning that the symptoms due to intracranial tumors are no different in pregnant compared with non pregnant patients. However, retrospective studies in glioma behavior suggested that both tumor volume and growth, increased during pregnancy. These changes were correlated with clinical worsening and increased frequency of seizures. The diagnosis requires a proper neurologic exploration and the support of imaging studies. Treatment of tumors is very controversial since we look for the preservation of both mother and fetus. In theory, the best therapy for the mother will also be the best therapy for the fetus. During pregnancy, ideally the treatment is symptomatic, to preserve the fetus, and definite treatment may be performed after birth; the latter is not always accomplished since patients may present with impending herniation or a malignant tumor for which immediate management is necessary. We intend to give an updated review in the literature on the adequate treatment of brain tumors during pregnancy and the anesthetic management during the definite treatment. Literature data was obtained from Pubmed using the search terms: "Pregnancy", "Brain", "Tumors". A total of forty-three articles were selected.

Comorbidity of cerebellopontine angle meningioma with other primary neoplasms

BACKGROUND

Meningioma is known to be accompanied by other primary neoplasms, yet has been evaluated less than these.

OBJECTIVE

This study investigated comorbidity of cerebellopontine angle (CPA) meningioma with other primary neoplasms.

METHODS

Overall 1,085 meningioma cases including 16 meningiomas at the CPA were enrolled for investigating the presence of other primary neoplasms. Another 16 age-, sex-, and size-matched CPA schwannoma were also included for comparison.

RESULTS

Of a data-base cohort study of overall 1085 meningioma cases, 165 cases (15%) were associated with other primary neoplasms. In contrast, 8 (50%) of 16 CPA meningioma and one (8%) of 16 CPA schwannoma showed other primary neoplasms. Except for one patient who had oral cancer prior to the diagnosis of CPA meningioma by 4 years, the interval from diagnosis of CPA meningioma to that of other primary neoplasm ranged 0-6 (mean, 3.1 ± 2.5) years.

CONCLUSION

Prevalence of comorbidity with other primary neoplasms is significantly higher in CPA meningioma (50%) than overall meningioma (15%) and CPA schwannoma (8%). In addition to follow-up MR imaging to visualize both residual tumor and regional brain environment after treatment of CPA meningioma, long-term systemic screening for other primary neoplasm is also mandatory.

Risk of primary brain tumour after breast cancer

INTRODUCTION

Cancer registry data in the USA indicated that women diagnosed with breast cancer before the age of 40 were at increased risk of a new primary tumour within the brain and women aged 50 years or above were at lower risk than expected. Our aim was to investigate if similar results could be found in Danish population-based data, considering an explanatory role of hormonal status.

METHODS

Our study cohort included all women diagnosed with breast cancer below the age of 60 between 1978 and 2013 in Denmark. A total of 47,920 women were followed up in the Danish Cancer Registry for primary brain cancer. Standardized incidence ratios (observed/expected cases (O/E)) were used to estimate the risk of getting a primary brain tumour in the breast cancer cohort.

RESULTS

Data indicated an increased tendency of brain cancer following breast cancer at ages below 60 years (O/E = 1.24). For premenopausal women (age <49 at the diagnosis of breast cancer) the O/E was 1.25. Stratifying by time of breast cancer diagnosis, we observed an increased risk of being diagnosed with a brain tumour among women aged 49 years or younger at breast cancer diagnosis between 2004 and 2013.

CONCLUSION

The results indicate an increased tendency of developing a primary brain tumour in women with previous breast cancer history. Whereas the finding in premenopausal women is in line with the SEER data, the finding among postmenopausal is not. Primary brain tumours in breast cancer patients call for research in genetics and hormones to establish common risk factors.

Epidemiology of meningiomas

More than 70,000 primary central nervous system tumors are diagnosed in the United States each year. Approximately 36% of these are meningiomas, making it the most common primary brain tumor. Because meningioma risk increases dramatically with age, the healthcare burden of meningioma in the developed world will continue to rise as demographics shift toward an older population. In addition to demographic factors associated with increased meningioma risk (i.e., older age, female sex, African American ethnicity), increased body mass index is a strong risk factor. A history of atopic allergies, eczema, and increased serum IgE are all consistently associated with reduced meningioma risk, suggesting a potential role for immunosurveillance. Although ionizing radiation is a strong meningioma risk factor, it accounts for very few cases at the population level. Recent studies suggest that diagnostic radiation (e.g., dental X-rays) increases meningioma risk. Because radiation dosages associated with medical imaging have decreased dramatically, the public health impact of this exposure is likely in decline. Genome-wide association studies have identified common inherited variants in the gene MLLT10 and RIC8A as low-penetrance meningioma risk alleles. To provide further insight into the etiology of meningioma, future studies will need to simultaneously examine genetic and environmental risk factors, while also stratifying analyses by subject sex.

Long-Term Use of Tamoxifen Is Associated With a Decreased Subsequent Meningioma Risk in Patients With Breast Cancer: A Nationwide Population-Based Cohort Study

Background: Earlier studies have indicated a relatively higher risk of occurring meningioma among female breast cancer survivors and have suggested that tamoxifen might decrease this risk. The present study evaluated whether tamoxifen use in breast cancer patients can reduce the risk of meningioma.

Methods: We designed a population-based cohort study by using data from the National Health Insurance system of Taiwan to assess this issue. Between January 1, 2000, and December 31, 2008, women with breast cancer and of age ≥20 years were included. They were divided into two groups: those who had not received tamoxifen therapy and those who had. The Cox’s proportion hazard regression analysis was conducted to estimate the effects of tamoxifen treatment and the subsequent meningioma risk.

Results: We identified a total of 50,442 tamoxifen users and 30,929 non-tamoxifen users. Tamoxifen users had a borderline significantly lower overall risk of meningioma than non-tamoxifen users [adjusted hazard ratio (aHR) = 0.64, 95% confidence interval (95% CI) = 0.40–1.02]. A statistically significant difference was found in those patients with tamoxifen treatment duration longer than 1,500 days (aHR = 0.42, 95% CI = 0.19–0.91) or with cumulative dosage exceeding 26,320 mg (aHR = 0.44, 95% CI = 0.22–0.88). Furthermore, no statistically significant joint effect of aromatase inhibitors and tamoxifen on the occurrence of meningioma among breast cancer patients was seen.

Conclusion: Tamoxifen users had a non-significantly (36%) lower risk of developing meningioma than did tamoxifen non-users; however, our data indicated that tamoxifen therapy is associated with a reduced meningioma risk for Taiwanese breast cancer patients receiving long duration or high cumulative dosage treatment with tamoxifen.

Racial Differences in Disease Presentation and Management of Intracranial Meningioma

Objective/Hypothesis  The aim of the study was to determine the impact of race on disease presentation and treatment of intracranial meningioma in the United States. Study Design  This study comprised of the analysis of a national population-based tumor registry. Methods  Analysis of the surveillance, epidemiology, and end results (SEER) database was performed, including all patients identified with a diagnosis of intracranial meningioma. Associations between race, disease presentation, treatment strategy, and overall survival were analyzed in a univariate and multivariable model. Results  A total of 65,973 patients with intracranial meningiomas were identified. Of these, 45,251 (68.6%) claimed white, 7,796 (12%) black, 7,154 (11%) Hispanic, 4,902 (7%) Asian, and 870 (1%) patients reported "other-unspecified" or "other-unknown." The median annual incidence of disease was lowest among black (3.43 per 100,000 persons) and highest among white (9.52 per 100,000 persons) populations ( p  < 0.001). Overall, Hispanic patients were diagnosed at the youngest age and white patients were diagnosed at the oldest age (mean of 59 vs. 66 years, respectively; p  < 0.001). Compared with white populations, black, Hispanic, and Asian populations were more likely to present with larger tumors ( p  < 0.001). After controlling for tumor size, age, and treatment center in a multivariable model, Hispanic patients were more likely to undergo surgery than white, black, and Asian populations. Black populations had the poorest disease specific and overall survival rates at 5 years following surgery compared with other groups. Conclusion  Racial differences among patients with intracranial meningioma exist within the United States. Understanding these differences are of vital importance toward identifying potential differences in the biological basis of disease or alternatively inequalities in healthcare delivery or access Further studies are required to determine which factors drive differences in tumor size, age, annual disease incidence, and overall survival between races.

Relevance of DNA repair gene polymorphisms to gastric cancer risk and phenotype

Variations in DNA repair genes have been reported as key factors in gastric cancer (GC) susceptibility but results among studies are inconsistent. We aimed to assess the relevance of DNA repair gene polymorphisms and environmental factors to GC risk and phenotype in a Caucasian population in Spain. Genomic DNA from 603 patients with primary GC and 603 healthy controls was typed for 123 single nucleotide polymorphisms in DNA repair genes using the Illumina platform. Helicobacter pylori infection with CagA strains (odds ratio (OR): 1.99; 95% confidence interval (CI): 1.55–2.54), tobacco smoking (OR: 1.77; 95% CI: 1.22–2.57), and family history of GC (OR: 2.87; 95% CI: 1.85–4.45) were identified as independent risk factors for GC. By contrast, the TP53 rs9894946A (OR: 0.73; 95% CI: 0.56–0.96), TP53 rs1042522C (OR: 0.76; 95% CI: 0.56–0.96), and BRIP1 rs4986764T (OR: 0.55; 95% CI: 0.38–0.78) variants were associated with lower GC risk. Significant associations with specific anatomopathological GC subtypes were also observed, most notably in the ERCC4 gene with the rs1799801C, rs2238463G, and rs3136038T variants being inversely associated with cardia GC risk. Moreover, the XRCC3 rs861528 allele A was significantly increased in the patient subgroup with diffuse GC (OR: 1.75; 95% CI: 1.30–2.37). Our data show that specific TP53, BRIP1, ERCC4, and XRCC3 polymorphisms are relevant in susceptibility to GC risk and specific subtypes in Caucasians.

CASP8, XRCC1, WRN, NF2, and BRIP1 Polymorphisms Analysis Shows Their Genetic Susceptibility for Meningioma Risk and the Association with Tumor-Related Phenotype in a Chinese Population

OBJECTIVE

To investigate 10 candidate single nucleotide polymorphisms (SNPs) in 5 genes (CASP8, XRCC1, WRN, NF2, and BRIP1) to confirm the association between the 5 genes and the meningioma risk in a Chinese population.

METHODS

We examined 10 candidate SNPs in 5 genes (CASP8, XRCC1, WRN, NF2, and BRIP1) to confirm the association between the 5 genes and the meningioma risk and tumor-related phenotype in 433 individuals, including 215 patients with meningioma and 218 controls.

RESULTS

The polymorphisms rs4968451T>G in BRIP1 were significantly associated with the risk of meningioma (TT vs. TG vs. GG additive, P = 0.005; TT+TG vs. GG dominant, P = 0.015; TT/GT+GG recessive, P = 0.034). The significant association was found only in females for BRIP1 rs4968451T>G (TT+TG vs. GG dominant, P = 0.001; TT/GT+GG recessive, P = 0.044). We observed no significant association between genotypes and the meningioma risk for the other 9 SNPs. Through genotype-phenotype analysis, the genotype of BRIP1 rs4968451T>G was also strongly associated with tumor-related phenotypes, including the tumor grade and tumor subtypes. BRIP1 rs4968451T>G was associated with markedly grade I meningioma risk (TT+TG vs. GG dominant, P = 0.008; TT/GT+GG recessive, P = 0.020). In addition, BRIP1 rs4968451T>G was associated with markedly meningothelial and transitional meningioma risk. Furthermore, the genotype of CAPS8, XRCC1, and NF2 was associated with different subtype of meningioma risk.

CONCLUSIONS

This study indicated a role for BRIP1 gene variations in meningioma and may be informative for future genetic or biological studies of meningioma. These findings will assist in further understanding the genetic cause for meningiomas and guide more effective biological interventions to facilitate meningiomas.

Werner syndrome (WRN) gene variants and their association with altered function and age-associated diseases

Werner syndrome (WS) is a heritable autosomal recessive human disorder characterized by the premature onset of several age-associated pathologies including cancer. The protein defective in WS patients, WRN, is encoded by a member of the human RECQ gene family that contains both a DNA exonuclease and a helicase domain. WRN has been shown to participate in several DNA metabolic pathways including DNA replication, recombination and repair, as well as telomere maintenance and transcription modulation. Here we review base pair-level genetic variation that has been documented in WRN, with an emphasis on non-synonymous coding single nucleotide polymorphisms (SNPs) and their associations with anthropomorphic features, longevity and disease risk. These associations have been challenging to identify, as many reported WRN SNP associations appear to be further conditioned upon ethnic, age, gender or other environmental co-variables. The WRN variant phenotypic associations identified to date are intriguing, and several are of clear clinical import. Consequently, it will be important to extend these initial associations and to identify the mechanisms and conditions under which specific WRN variants may compromise WRN function to drive cellular and organismal phenotypes as well as disease risk.

Clinical and Genetic Risk Prediction of Subsequent CNS Tumors in Survivors of Childhood Cancer: A Report From the COG ALTE03N1 Study

Purpose Survivors of childhood cancer treated with cranial radiation therapy are at risk for subsequent CNS tumors. However, significant interindividual variability in risk suggests a role for genetic susceptibility and provides an opportunity to identify survivors of childhood cancer at increased risk for these tumors. Methods We curated candidate genetic variants from previously published studies in adult-onset primary CNS tumors and replicated these in survivors of childhood cancer with and without subsequent CNS tumors (82 participants and 228 matched controls). We developed prediction models to identify survivors at high or low risk for subsequent CNS tumors and validated these models in an independent matched case-control sample (25 participants and 54 controls). Results We demonstrated an association between six previously published single nucleotide polymorphisms (rs15869 [ BRCA2], rs1805389 [ LIG4], rs8079544 [ TP53], rs25489 [ XRCC1], rs1673041 [ POLD1], and rs11615 [ ERCC1]) and subsequent CNS tumors in survivors of childhood cancer. Including genetic variants in a Final Model containing age at primary cancer, sex, and cranial radiation therapy dose yielded an area under the curve of 0.81 (95% CI, 0.76 to 0.86), which was superior ( P = .002) to the Clinical Model (area under the curve, 0.73; 95% CI, 0.66 to 0.80). The prediction model was successfully validated. The sensitivity and specificity of predicting survivors of childhood cancer at highest or lowest risk of subsequent CNS tumors was 87.5% and 83.5%, respectively. Conclusion It is possible to identify survivors of childhood cancer at high or low risk for subsequent CNS tumors on the basis of genetic and clinical information. This information can be used to inform surveillance for early detection of subsequent CNS tumors.

A miR-SNP biomarker linked to an increased lung cancer survival by miRNA-mediated down-regulation of FZD4 expression and Wnt signaling

Through a new hypothesis-driven and microRNA-pathway-based SNP (miR-SNP) association study we identified a novel miR-SNP (rs713065) in the 3'UTR region of FZD4 gene linked with decreased risk of death in early stage NSCLC patients. We determined biological function and mechanism of action of this FZD4-miR-SNP biomarker in a cellular platform. Our data suggest that FZD4-miR-SNP loci may significantly influence overall survival in NSCLC patients by specifically interacting with miR-204 and modulating FZD4 expression and cellular function in the Wnt-signaling-driven tumor progression. Our findings are bridging the gap between the discovery of epidemiological SNP biomarkers and their biological function and will enable us to develop novel therapeutic strategies that specifically target epigenetic markers in the oncogenic Wnt/FZD signaling pathways in NSCLC.

Genetic changes of MLH1 and MSH2 genes could explain constant findings on microsatellite instability in intracranial meningioma

Postreplicative mismatch repair safeguards the stability of our genome. The defects in its functioning will give rise to microsatellite instability. In this study, 50 meningiomas were investigated for microsatellite instability. Two major mismatch repair genes, MLH1 and MSH2, were analyzed using microsatellite markers D1S1611 and BAT26 amplified by polymerase chain reaction and visualized by gel electrophoresis on high-resolution gels. Furthermore, genes DVL3 (D3S1262), AXIN1 (D16S3399), and CDH1 (D16S752) were also investigated for microsatellite instability. Our study revealed constant presence of microsatellite instability in meningioma patients when compared to their autologous blood DNA. Altogether 38% of meningiomas showed microsatellite instability at one microsatellite locus, 16% on two, and 13.3% on three loci. The percent of detected microsatellite instability for MSH2 gene was 14%, and for MLH1, it was 26%, for DVL3 22.9%, for AXIN1 17.8%, and for CDH1 8.3%. Since markers also allowed for the detection of loss of heterozygosity, gross deletions of MLH1 gene were found in 24% of meningiomas. Genetic changes between MLH1 and MSH2 were significantly positively correlated (p = 0.032). We also noted a positive correlation between genetic changes of MSH2 and DVL3 genes (p = 0.034). No significant associations were observed when MLH1 or MSH2 was tested against specific histopathological meningioma subtype or World Health Organization grade. However, genetic changes in DVL3 were strongly associated with anaplastic histology of meningioma (χ² = 9.14; p = 0.01). Our study contributes to better understanding of the genetic profile of human intracranial meningiomas and suggests that meningiomas harbor defective cellular DNA mismatch repair mechanisms.

Molecular Genetics of Intracranial Meningiomas with Emphasis on Canonical Wnt Signalling

Research over the last decade recognized the importance of novel molecular pathways in pathogenesis of intracranial meningiomas. In this review, we focus on human brain tumours meningiomas and the involvement of Wnt signalling pathway genes and proteins in this common brain tumour, describing their known functional effects. Meningiomas originate from the meningeal layers of the brain and the spinal cord. Most meningiomas have benign clinical behaviour and are classified as grade I by World Health Organization (WHO). However, up to 20% histologically classified as atypical (grade II) or anaplastic (grade III) are associated with higher recurrent rate and have overall less favourable clinical outcome. Recently, there is emerging evidence that multiple signalling pathways including Wnt pathway contribute to the formation and growth of meningiomas. In the review we present the synopsis on meningioma histopathology and genetics and discuss our research regarding Wnt in meningioma. Epithelial-to-mesenchymal transition, a process in which Wnt signalling plays an important role, is shortly discussed.

Nervous System and Intracranial Tumour Incidence by Ethnicity in England, 2001-2007: A Descriptive Epidemiological Study

Background

There is substantial variation in nervous system and intracranial tumour incidence worldwide. UK incidence data have limited utility because they group these diverse tumours together and do not provide data for individual ethnic groups within Blacks and South Asians. Our objective was to determine the incidence of individual tumour types for seven individual ethnic groups.

Methods

We used data from the National Cancer Intelligence Network on tumour site, age, sex and deprivation to identify 42,207 tumour cases. Self-reported ethnicity was obtained from the Hospital Episode Statistics database. We used mid-year population estimates from the Office for National Statistics. We analysed tumours by site using Poisson regression to estimate incidence rate ratios comparing non-White ethnicities to Whites after adjustment for sex, age and deprivation.

Results

Our study showed differences in tumour incidence by ethnicity for gliomas, meningiomas, pituitary tumours and cranial and paraspinal nerve tumours. Relative to Whites; South Asians, Blacks and Chinese have a lower incidence of gliomas (p<0.01), with respective incidence rate ratios of 0.68 (confidence interval: 0.60–0.77), 0.62 (0.52–0.73) and 0.58 (0.41–0.83). Blacks have a higher incidence of meningioma (p<0.01) with an incidence rate ratio of 1.29 (1.05–1.59) and there is heterogeneity in meningioma incidence between individual South Asian ethnicities. Blacks have a higher incidence of pituitary tumours relative to Whites (p<0.01) with an incidence rate ratio of 2.95 (2.37–3.67). There is heterogeneity in pituitary tumour incidence between individual South Asian ethnicities.

Conclusions

We present incidence data of individual tumour types for seven ethnic groups. Current understanding of the aetiology of these tumours cannot explain our results. These findings suggest avenues for further work.

Genetic variation as a modifier of association between therapeutic exposure and subsequent malignant neoplasms in cancer survivors

Subsequent malignant neoplasms (SMNs) are associated with significant morbidity and are a major cause of premature mortality among cancer survivors. Several large studies have demonstrated a strong association between the radiation and/or chemotherapy used to treat primary cancer and the risk of developing SMNs. However, for any given therapeutic exposure, the risk of developing an SMN varies between individuals. Genomic variation can potentially modify the association between therapeutic exposures and SMN risk and may explain the observed interindividual variability. In this review, the author provides a brief overview of the current knowledge regarding the role of genomic variation in the development of therapy-related SMNs and discusses the methodological challenges in undertaking an endeavor to develop a deeper understanding of the molecular underpinnings of therapy-related SMNs, such as an appropriate study design, the identification of an adequately sized study population together with a reliable plan for collecting and maintaining high-quality DNA, clinical validation of the phenotype, and the selection of an appropriate approach or platform for genotyping. Understanding the factors that can modify the risk of treatment-related SMNs is critical to developing targeted intervention strategies and optimizing risk-based health care for cancer survivors.

Cyclin D1 gene G870A variants and primary brain tumors

Alterations of cyclin D1, one of the main regulators of the cell cycle, are known to be involved in various cancers. The CCDN1 G870A polymorphism causes production of a truncated variant with a shorter half-life and thus thought to impact the regulatory effect of CCDN1. The aim of the present study was to contribute to existing results to help to determine the prognostic value of this specific gene variant and evaluate the role of CCDN1 G870A polymorphism in brain cancer susceptibility. A Turkish study group including 99 patients with primary brain tumors and 155 healthy controls were examined. Genotypes were determined by polymerase chain reaction-restriction fragment length polymorphism analysis. The CCDN1 genotype frequencies in meningioma, glioma and control cases were not significantly different (p>0.05). No significant association was detected according to clinical parameters or tumor characteristics; however, a higher frequency of AG genotype was recorded within patients with astrocytic or oligoastrocytic tumors. A significant association between AG genotype and gliobilastoma multiforme (GBM) was recorded within the patients with glial tumors (p value=0.048 OR: 1.87 CI% 1.010-3.463). According to tumor characteristics, no statistically significant difference was detected within astrocytic, oligoasltrocytic tumors and oligodentrioglias. However, patients with astrocytic astrocytic or oligoastrocytic tumors showed a higher frequency of AG genotype (50%) when compared to those with oligodendrioglial tumors (27.3%). Our results indicate a possible relation between GBM formation and CCDN1 genotype.

Association between DNA repair gene polymorphisms and risk of glioma: a systematic review and meta-analysis

BACKGROUND

Association studies of germline DNA repair single nucleotide polymorphisms (SNPs) and glioma risk have yielded inconclusive results. We therefore performed a systematic review and meta-analysis of studies investigating this association.

METHODS

We identified 27 eligible studies investigating 105 SNPs in 42 DNA repair genes. Of these, 10 SNPs in 7 genes were analyzed in at least 4 studies and were therefore included in our meta-analysis. The meta-analysis was performed for homozygote comparison, heterozygote comparison, and dominant and recessive models by applying a fixed- or random-effects model. The funnel and forest plots were created using RevMan software.

RESULTS

We found that SNPs rs3212986 (odds ratio [OR] = 1.35 (1.08-1.68), P = .008), rs13181 (OR = 1.18 (1.06-1.31), P = .002), and rs25487 (OR = 1.12 (1.03-1.22), P = .007) in DNA repair genes ERCC1, ERCC2 (XPD), and XRCC1 may increase the risk of glioma, while polymorphisms rs1136410 (OR = 0.78 (0.68-0.89), P = .0004) and rs12917 (OR = 0.84 (0.73-0.96), P = .01) in PARP1(ADPRT) and MGMT are associated with decreased susceptibility to glioma. No evidence of significant associations between ERCC2 rs1799793, OGG1 rs1052133, XRCC1 rs25489, XRCC1 rs1799782, or XRCC3 rs861539 and risk of glioma was observed.

CONCLUSION

This study provides evidence that DNA repair genes ERCC1, ERCC2, and XRCC1 might be low-penetrance glioma-risk genes, while MGMT and PARP1 polymorphisms may confer protection against glioma.

Replicative DNA polymerase mutations in cancer

Three DNA polymerases - Pol α, Pol δ and Pol ɛ - are essential for DNA replication. After initiation of DNA synthesis by Pol α, Pol δ or Pol ɛ take over on the lagging and leading strand respectively. Pol δ and Pol ɛ perform the bulk of replication with very high fidelity, which is ensured by Watson-Crick base pairing and 3'exonuclease (proofreading) activity. Yeast models have shown that mutations in the exonuclease domain of Pol δ and Pol ɛ homologues can cause a mutator phenotype. Recently, we identified germline exonuclease domain mutations (EDMs) in human POLD1 and POLE that predispose to 'polymerase proofreading associated polyposis' (PPAP), a disease characterised by multiple colorectal adenomas and carcinoma, with high penetrance and dominant inheritance. Moreover, somatic EDMs in POLE have also been found in sporadic colorectal and endometrial cancers. Tumors with EDMs are microsatellite stable and show an 'ultramutator' phenotype, with a dramatic increase in base substitutions.

The roles of Jumonji-type oxygenases in human disease

The iron- and 2-oxoglutarate-dependent oxygenases constitute a phylogenetically conserved class of enzymes that catalyze hydroxylation reactions in humans by acting on various types of substrates, including metabolic intermediates, amino acid residues in different proteins and various types of nucleic acids. The discovery of jumonji (Jmj), the founding member of a class of Jmj-type chromatin modifying enzymes and transcriptional regulators, has culminated in the discovery of several branches of histone lysine demethylases, with essential functions in regulating the epigenetic landscape of the chromatin environment. This work has now been considerably expanded into other aspects of epigenetic biology and includes the discovery of enzymatic steps required for methyl-cytosine demethylation as well as modification of RNA and ribosomal proteins. This overview aims to summarize the current knowledge on the human Jmj-type enzymes and their involvement in human pathological processes, including development, cancer, inflammation and metabolic diseases.

Loss of SUFU function in familial multiple meningioma

Meningiomas are the most common primary tumors of the CNS and account for up to 30% of all CNS tumors. An increased risk of meningiomas has been associated with certain tumor-susceptibility syndromes, especially neurofibromatosis type II, but no gene defects predisposing to isolated familial meningiomas have thus far been identified. Here, we report on a family of five meningioma-affected siblings, four of whom have multiple tumors. No NF2 mutations were identified in the germline or tumors. We combined genome-wide linkage analysis and exome sequencing, and we identified in suppressor of fused homolog (Drosophila), SUFU, a c.367C>T (p.Arg123Cys) mutation segregating with the meningiomas in the family. The variation was not present in healthy controls, and all seven meningiomas analyzed displayed loss of the wild-type allele according to the classic two-hit model for tumor-suppressor genes. In silico modeling predicted the variant to affect the tertiary structure of the protein, and functional analyses showed that the activity of the altered SUFU was significantly reduced and therefore led to dysregulated hedgehog (Hh) signaling. SUFU is a known tumor-suppressor gene previously associated with childhood medulloblastoma predisposition. Our genetic and functional analyses indicate that germline mutations in SUFU also predispose to meningiomas, particularly to multiple meningiomas. It is possible that other genic mutations resulting in aberrant activation of the Hh pathway might underlie meningioma predisposition in families with an unknown etiology.

Dental x-rays and risk of meningioma

BACKGROUND

Ionizing radiation is a consistently identified and potentially modifiable risk factor for meningioma, which is the most frequently reported primary brain tumor in the United States. The objective of this study was to examine the association between dental x-rays-the most common artificial source of ionizing radiation-and the risk of intracranial meningioma.

METHODS

This population-based case-control study included 1433 patients who had intracranial meningioma diagnosed at ages 20 to 79 years and were residents of the states of Connecticut, Massachusetts, North Carolina, the San Francisco Bay Area, and 8 counties in Houston, Texas between May 1, 2006 and April 28, 2011 (cases). A control group of 1350 individuals was frequency matched on age, sex, and geography (controls). The main outcome measure for the study was the association between a diagnosis of intracranial meningioma and self-reported bitewing, full-mouth, and panorex dental x-rays.

RESULTS

Over a lifetime, cases were more than twice as likely as controls (odds ratio [OR], 2.0; 95% confidence interval [CI], 1.4-2.9) to report having ever had a bitewing examination. Regardless of the age at which the films were obtained, individuals who reported receiving bitewing films on a yearly basis or with greater frequency had an elevated risk for ages <10 years (OR, 1.4; 95% CI, 1.0-1.8), ages 10 to 19 years (OR, 1.6; 95% CI, 1.2-2.0), ages 20 to 49 years (OR, 1.9; 95% CI, 1.4-2.6), and ages ≥40 years (OR, 1.5; 95% CI, 1.1-2.0). An increased risk of meningioma also was associated with panorex films taken at a young age or on a yearly basis or with greater frequency, and individuals who reported receiving such films at ages <10 years had a 4.9 times increased risk (95% CI, 1.8-13.2) of meningioma. No association was appreciated for tumor location above or below the tentorium.

CONCLUSIONS

Exposure to some dental x-rays performed in the past, when radiation exposure was greater than in the current era, appears to be associated with an increased risk of intracranial meningioma. As with all sources of artificial ionizing radiation, considered use of this modifiable risk factor may be of benefit to patients.

Hunting for the causes of meningioma--obesity is a suspect

In this issue of the journal, Michaud and colleagues report a 48% increased risk of meningioma in obese individuals compared with individuals with a normal body mass index (BMI). This large prospective cohort study adds weight to the suggested link between BMI and meningioma, thus contributing to the growing number of cancer sites likely associated with body fatness. Although the exact mechanisms underlying the BMI-meningioma link are unclear, possible mediators include hormonal factors, immunologic response, and levels of insulin or insulin-like growth factors, each of which has been implicated by various levels of evidence in meningioma risk. Understanding the relationships between body fatness, height, and hormonal and immunologic factors could provide important clues to the etiology of meningioma and may have implications for the early detection and prevention of these tumors.

Family and personal medical history and risk of meningioma

OBJECT

Little is known about the epidemiology of meningioma, the most frequently reported primary brain tumor in the US. The authors undertook a case-control study to examine the relationship between family and personal medical history and meningioma risk.

METHODS

The authors compared the personal and first-degree family histories of 1124 patients with meningioma (age range 20-79 years) in Connecticut, Massachusetts, North Carolina, the San Francisco Bay Area, and 8 Houston counties between May 1, 2006, and February 26, 2010, and the histories of 1000 control individuals who were frequency-matched for age, sex, and geography.

RESULTS

The patients were more likely than the controls to report a first-degree family history of meningioma (OR 4.4, 95% CI 1.6-11.5), and there was an even stronger association in younger cases. The patients were less likely than controls to report immune conditions including allergy (OR 0.6, 95% CI 0.5-0.7) but were more likely to report a history of thyroid cancer (OR 4.7, 95% CI 1.02-21.5) or leukemia (OR 5.4, 95% CI 1.2-24.1) (most after radiotherapy). Among women, patients were more likely than controls to report hormonally related conditions--uterine fibroid tumors (OR 1.2, 95% CI 1.0-1.5), endometriosis (OR 1.5, 95% CI 1.5-2.1), and breast cancer (OR 1.4, 95% CI 0.8-2.3).

CONCLUSIONS

The influence of genetics, the immune system, and radiation near the head on meningioma risk is suggested in the authors' findings; the role of hormones is intriguing but requires further study.

Inverse association between eczema and meningioma: a meta-analysis

BACKGROUND AND PURPOSE

The pathogenesis of primary brain tumors may be related to immune response. Prior studies have shown a strong association between allergy and glioma; however, so far no significant association has been established between allergy and meningioma. Here, we conducted a meta-analysis of published studies to investigate the association of meningioma with the overall and specific allergic conditions.

METHODS

PubMed, EMBASE database, and Cochrane Library were searched for pertinent citations published between January 1979 and October 2009. We used the following searching strategy (brain tumor [Text Word] OR meningioma [Text Word]) AND (allergy [Text Word] OR atopy [Text Word] OR asthma [Text Word] OR eczema [Text Word] OR hay fever [Text Word]) to search for relevant studies. Random effect model was used to estimate the association between allergic conditions and meningioma.

RESULT

A total of 7 studies (5 case-control studies and 2 cohort studies) were included in the analysis, involving 54,391 participants, of whom 2,656 had meningioma. When compared to non-allergic conditions, the pooled odds ratio (OR) with any allergic conditions for meningioma was 0.91 (95% CI: 0.79-1.04, p = 0.163), suggesting that there is no significant association between meningioma and allergic conditions. Interestingly, further analysis showed that eczema had significantly inverse association with meningioma (OR, 0.75; 95% CI: 0.65-0.87, p < 0.05). On the other hand, no significant association was found for asthma (OR, 0.88; 95% CI: 0.75-1.04, p = 0.126) and hay fever (OR, 0.90; 95% CI: 0.79-1.03, p = 0.137).

CONCLUSION

In conclusion, there was a significantly negative association between eczema and meningioma, suggesting that eczema may reduce the risk of meningioma. Although it was not statistically significant association between meningioma and other specific allergic conditions such as asthma and hay fever, further studies with large sample size may be needed to determine its relationship.

Gene expression profiles of non-small cell lung cancer: survival prediction and new biomarkers

OBJECTIVES

Despite the well-defined histological types of non-small cell lung cancer (NSCLC), a given stage is often associated with wide-ranging survival rates and treatment outcomes. This disparity has led to an increased demand for the discovery and identification of new informative biomarkers.

METHODS

In the current study, we screened 81 NSCLC samples using Illumina whole-genome gene expression microarrays in an effort to identify differentially expressed genes and new NSCLC biomarkers.

RESULTS

We identified novel genes whose expression was upregulated in NSCLC, including SPAG5, POLH, KIF23, and RAD54L, which are associated with mitotic spindle formation, DNA repair, chromosome segregation, and dsDNA break repair, respectively. We also identified several novel genes whose expression was downregulated in NSCLC, including SGCG, NLRC4, MMRN1, and SFTPD, which are involved in extracellular matrix formation, apoptosis, blood vessel leakage, and inflammation, respectively. We found a significant correlation between RNA degradation and survival in adenocarcinoma cases.

CONCLUSIONS

Even though the follow-up time was too limited to draw final conclusions, we were able to show better prediction p values in a group selection based on molecular profiles compared to histology. The current study also uncovered new candidate biomarker genes that are likely to be involved in diverse processes associated with NSCLC development.

Brain tumors and hormonal factors: review of the epidemiological literature

BACKGROUND

To date, the etiology of primary tumors of the central nervous system (mainly gliomas and meningiomas) is poorly understood. The role of sex hormones has been suggested, based on clinical, experimental, biological, and epidemiological data.

OBJECTIVE

To review the epidemiological studies on the relation between hormonal factors and the occurrence of glioma and meningioma, in order to identify new research developments.

METHODS

Articles published until September 2010 were selected by considering exogenous and endogenous exposures and specific brain tumors. Standardized information was collected from 20 articles: 15 concerning gliomas and 13 meningiomas.

RESULTS

An increased glioma risk was observed with later menarche and menopause, while a reduced glioma risk was observed with hormone replacement therapy (HRT) and oral contraceptive use, despite duration of use had no effect on risk. Meningioma risk increased after menopause and with HRT use. No clear association was found with pregnancy and breastfeeding.

CONCLUSION

Results are globally concordant with the biologic hypothesis assuming that female sex hormones are protective against glioma and may increase the risk of meningioma. However, new epidemiological studies should be conducted in order to confirm these associations and to refine the role of hormonal factors in brain etiology.

DNA replication fidelity and cancer

Cancer is fueled by mutations and driven by adaptive selection. Normal cells avoid deleterious mutations by replicating their genomes with extraordinary accuracy. Here we review the pathways governing DNA replication fidelity and discuss evidence implicating replication errors (point mutation instability or PIN) in carcinogenesis.

[Epidemiology of glioblastoma]

An increasing incidence of glioblastoma has been observed over the last 30 years. Improvements in diagnostic tools such as CT scans and MRI, changes observed in histological classifications, and adjustments in neurosurgical practices have contributed substantially to this increase. Moreover, the aging of the population and the increasing occurrence of glioblastoma beyond 60 years of age are additional explanations. In Gironde (France), where a specialized registry has been established, the annual incidence of glioblastoma is 4.96/100,000. Wide geographic variations are observed, possibly linked to ethnicity. However, the role of intrinsic and/or extrinsic factors cannot be ruled out. Comparing data between registries is difficult and requires taking into account periods of recruitment and diagnostic tools. Ethnicity, age, sex, hereditary syndromes, some constitutive polymorphisms, and brain irradiation are the established risk factors Allergies or asthma, certain viral infections, autoimmune diseases, nonsteroidal anti-inflammatory drug intake, substitutive hormonal therapy, and dietary antioxidant intake are the established protective factors. Many studies on electromagnetic fields - in particular cellular phones - pesticides, solvents, and other factors have been published. Until now, the results are discordant or are not confirmed because of methodological limitations. Future studies combining constitutive polymorphisms and exposure assessment are likely to provide consistent and important data that will improve our knowledge in the epidemiology of glioblastoma.

Epidemiology and etiology of meningioma

Although most meningiomas are encapsulated and benign tumors with limited numbers of genetic aberrations, their intracranial location often leads to serious and potentially lethal consequences. They are the most frequently diagnosed primary brain tumor accounting for 33.8% of all primary brain and central nervous system tumors reported in the United States between 2002 and 2006. Inherited susceptibility to meningioma is suggested both by family history and candidate gene studies in DNA repair genes. People with certain mutations in the neurofibromatosis gene (NF2) have a very substantial increased risk for meningioma. High dose ionizing radiation exposure is an established risk factor for meningioma, and lower doses may also increase risk, but which types and doses are controversial or understudied. Because women are twice as likely as men to develop meningiomas and these tumors harbor hormone receptors, an etiologic role for hormones (both endogenous and exogenous) has been hypothesized. The extent to which immunologic factors influence meningioma etiology has been largely unexplored. Growing emphasis on brain tumor research coupled with the advent of new genetic and molecular epidemiologic tools in genetic and molecular epidemiology promise hope for advancing knowledge about the causes of intra-cranial meningioma. In this review, we highlight current knowledge about meningioma epidemiology and etiology and suggest future research directions.

Risk of meningioma and common variation in genes related to innate immunity

BACKGROUND

The etiology of meningioma, the second most common type of adult brain tumor in the United States, is largely unknown. Prior studies indicate that history of immune-related conditions may affect the risk of meningioma.

METHODS

To identify genetic markers for meningioma in genes involved with innate immunity, we conducted an exploratory association study of 101 meningioma cases and 330 frequency-matched controls of European ancestry using subjects from a hospital-based study conducted by the National Cancer Institute. We genotyped 1,407 "tag" single nucleotide polymorphisms (SNP) in 148 genetic regions chosen on the basis of an r2>0.8 and minor allele frequency of >5% in Caucasians in HapMap1. Risk of meningioma was estimated by odds ratios and 95% confidence intervals.

RESULTS

Seventeen SNPs distributed across 12 genetic regions (NFKB1 (3), FCER1G (3), CCR6 (2), VCAM1, CD14, TNFRSF18, RAC2, XDH, C1D, TLR1/TLR10/TLR6, NOS1, and DEFA5) were associated with the risk of meningioma with P<0.01. Although individual SNP tests were not significant after controlling for multiple comparisons, gene region-based tests were statistically significant (P<0.05) for TNFRSF18, NFKB1, FCER1G, CD14, C1D, CCR6, and VCAM1.

CONCLUSIONS AND IMPACT

Our results indicate that common genetic polymorphisms in innate immunity genes may be associated with risk of meningioma. Given the small sample size, replication of these results in a larger study of meningioma is needed.

DNA repair gene polymorphisms and risk of adult meningioma, glioma, and acoustic neuroma

Although the etiology of primary brain tumors is largely unknown, prior studies suggest that DNA repair polymorphisms may influence risk of glioma. Altered DNA repair is also likely to affect the risk of meningioma and acoustic neuroma, but these tumors have not been well studied. We estimated the risk of glioma (n = 362), meningioma (n = 134), and acoustic neuroma (n = 69) in non-Hispanic whites with respect to 36 single nucleotide polymorphisms from 26 genes involved in DNA repair in a hospital-based, case-control study conducted by the National Cancer Institute. We observed significantly increased risk of meningioma with the T variant of GLTSCR1 rs1035938 (OR(CT/TT) = 3.5; 95% confidence interval: 1.8-6.9; P(trend) .0006), which persisted after controlling for multiple comparisons (P = .019). Significantly increased meningioma risk was also observed for the minor allele variants of ERCC4 rs1800067 (P(trend) .01); MUTYH rs3219466 (P(trend) .02), and PCNA rs25406 (P(trend) .03). The NBN rs1805794 minor allele variant was associated with decreased meningioma risk (P(trend) .006). Risk of acoustic neuroma was increased for the ERCC2 rs1799793 (P(trend) .03) and ERCC5 rs17655 (P(trend) .05) variants and decreased for the PARP1 rs1136410 (P(trend) .03). Decreased glioma risk was observed with the XRCC1 rs1799782 variant (P(trend) .04). Our results suggest that common DNA repair variants may affect the risk of adult brain tumors, especially meningioma.

Genetic variants in association studies--review of strengths and weaknesses in study design and current knowledge of impact on cancer risk

Sequencing of the human genome has recently been completed and mapping of the complete genomic variation is ongoing. During the last decade there has been a huge expansion of studies of genetic variants, both with respect to association studies of disease risk and for studies of genetic factors of prognosis and treatments response, i.e., pharmacogenomics. The use of genetics to predict a patient's risk of disease or treatment response is one step toward an improved personalised prevention and screening modality for the prevention of cancer and treatment selection. The technology and statistical methods for completing whole genome tagging of variants and genome wide association studies has developed rapidly over the last decade. After identifying the genetic loci with the strongest, statistical associations with disease risk, future studies will need to further characterise the genotype-phenotype relationship to provide a biological basis for prevention and treatment decisions according to genetic profile. This review discusses some of the general issues and problems of study design; we also discuss challenges in conducting valid association studies in rare cancers such as paediatric brain tumours, where there is support for genetic susceptibility but difficulties in assembling large sample sizes. The clinical interpretation and implementation of genetic association studies with respect to disease risk and treatment is not yet well defined and remains an important area of future research.

Polymorphisms in uracil-processing genes, but not one-carbon nutrients, are associated with altered DNA uracil concentrations in an urban Puerto Rican population

BACKGROUND

Five genes--UNG, SMUG1, MBD4, TDG, and DUT--are involved in the repair or prevention of uracil misincorporation into DNA, an anomaly that can cause mutagenic events that lead to cancer. Little is known about the determinants of uracil misincorporation, including the effects of single nucleotide polymorphisms (SNPs) in the abovementioned genes. Because of their metabolic function, folate and other one-carbon micronutrients may be important factors in the control of uracil misincorporation.

OBJECTIVES

We sought to identify polymorphisms in uracil-processing genes that are determinants of DNA uracil concentration and to establish whether one-carbon nutrient status can further modify their effects.

DESIGN

We examined the relations between 23 selected variants in the 5 uracil-processing genes, uracil concentrations in whole-blood DNA, and one-carbon nutrient (folate, vitamins B-6 and B-12, and riboflavin) status in 431 participants of the Boston Puerto Rican Health Study.

RESULTS

Four SNPs in DUT, UNG, and SMUG1 showed a significant association with DNA uracil concentration. The SNPs in SMUG1 (rs2029166 and rs7296239) and UNG (rs34259) were associated with increased uracil concentrations in the variant genotypes (P = 0.011, 0.022, and 0.045, respectively), whereas the DUT SNP (rs4775748) was associated with a decrease (P = 0.023). In this population, one-carbon nutrient status was not associated with DNA uracil concentration, and it did not modify the effect of these 4 identified SNPs.

CONCLUSION

Because elevated uracil misincorporation may induce mutagenic lesions, possibly leading to cancer, we propose that the 4 characterized SNPs in DUT, UNG, and SMUG1 may influence cancer risk and therefore deserve further investigation.

[Epidemiology of primary brain tumor]

Two main approaches are generally used to study the epidemiology of primary brain tumors. The first approach is to identify risk factors, which may be intrinsic or related to external causes. The second main approach is descriptive. Intrinsic factors potentially affecting risk include genetic predisposition and susceptibility, gender, race, birth weight and allergy. Radiation exposure is the main extrinsic factor affecting risk. A large body of work devoted, among others, to electromagnetic fields and especially cellular phones, substitutive hormonal therapy, pesticides, and diet have been published. To date, results have been discordant. Descriptive epidemiological studies have reported an increasing annual incidence of primary brain tumors in industrialized countries. The main reasons are the increasing age of the population and better access to diagnostic imaging. Comparing incidences from one registry to another is difficult. Spatial and temporal variations constitute one explanation and evolutions in coding methods another. In all registries, weak incidence of primary brain tumors constitute a very important limiting factor. Renewed interest from the neuro-oncological community is needed to obtain pertinent and essential data which could facilitate improved knowledge on this topic.

Brain tumor epidemiology: consensus from the Brain Tumor Epidemiology Consortium

Epidemiologists in the Brain Tumor Epidemiology Consortium (BTEC) have prioritized areas for further research. Although many risk factors have been examined over the past several decades, there are few consistent findings, possibly because of small sample sizes in individual studies and differences between studies in patients, tumor types, and methods of classification. Individual studies generally have lacked samples of sufficient size to examine interactions. A major priority based on available evidence and technologies includes expanding research in genetics and molecular epidemiology of brain tumors. BTEC has taken an active role in promoting understudied groups, such as pediatric brain tumors; the etiology of rare glioma subtypes, such as oligodendroglioma; and meningioma, which, although it is not uncommon, has only recently been registered systematically in the United States. There also is a pressing need for more researchers, especially junior investigators, to study brain tumor epidemiology. However, relatively poor funding for brain tumor research has made it difficult to encourage careers in this area. In this report, BTEC epidemiologists reviewed the group's consensus on the current state of scientific findings, and they present a consensus on research priorities to identify which important areas the science should move to address.

Genetic susceptibility to cancer: the role of polymorphisms in candidate genes

CONTEXT

Continuing advances in genotyping technologies and the inclusion of DNA collection in observational studies have resulted in an increasing number of genetic association studies.

OBJECTIVE

To evaluate the overall progress and contribution of candidate gene association studies to current understanding of the genetic susceptibility to cancer.

DATA SOURCES

We systematically examined the results of meta-analyses and pooled analyses for genetic polymorphisms and cancer risk published through March 2008.

STUDY SELECTION

We identified 161 meta-analyses and pooled analyses, encompassing 18 cancer sites and 99 genes. Analyses had to meet the following criteria: include at least 500 cases, have cancer risk as outcome, not be focused on HLA antigen genetic markers, and be published in English.

DATA EXTRACTION

Information on cancer site, gene name, variant, point estimate and 95% confidence interval (CI), allelic frequency, number of studies and cases, tests of study heterogeneity, and publication bias were extracted by 1 investigator and reviewed by other investigators.

RESULTS

These 161 analyses evaluated 344 gene-variant cancer associations and included on average 7.3 studies and 3551 cases (range, 508-19 729 cases) per investigated association. The summary odds ratio (OR) for 98 (28%) statistically significant associations (P value <.05) were further evaluated by estimating the false-positive report probability (FPRP) at a given prior probability and statistical power. At a prior probability level of 0.001 and statistical power to detect an OR of 1.5, 13 gene-variant cancer associations remained noteworthy (FPRP <0.2). Assuming a very low prior probability of 0.000001, similar to a probability assumed for a randomly selected single-nucleotide polymorphism in a genome-wide association study, and statistical power to detect an OR of 1.5, 4 associations were considered noteworthy as denoted by an FPRP value <0.2: GSTM1 null and bladder cancer (OR, 1.5; 95% CI, 1.3-1.6; P = 1.9 x 10(-14)), NAT2 slow acetylator and bladder cancer (OR, 1.46; 95% CI, 1.26-1.68; P = 2.5 x 10(-7)), MTHFR C677T and gastric cancer (OR, 1.52; 95% CI, 1.31-1.77; P = 4.9 x 10(-8)), and GSTM1 null and acute leukemia (OR, 1.20; 95% CI, 1.14-1.25; P = 8.6 x 10(-15)). When the OR used to determine statistical power was lowered to 1.2, 2 of the 4 noteworthy associations remained so: GSTM1 null with bladder cancer and acute leukemia.

CONCLUSION

In this review of candidate gene association studies, nearly one-third of gene-variant cancer associations were statistically significant, with variants in genes encoding for metabolizing enzymes among the most consistent and highly significant associations.