Genome-wide association study identifies multiple susceptibility loci for glioma

A Mendelian randomization study of the entire phenome to explore the causal links between epilepsy

OBJECTIVE

The causes and triggering factors of epilepsy are still unknown. The results of genome-wide association studies can be utilized for a phenome-wide association study using Mendelian randomization (MR) to identify potential risk factors for epilepsy.

METHODS

This study utilizes two-sample MR analysis to investigate whether 316 phenotypes, including lifestyle, environmental factors, blood biomarker, and more, are causally associated with the occurrence of epilepsy. The primary analysis employed the inverse variance weighted (IVW) model, while complementary MR analysis methods (MR Egger, Wald ratio) were also employed. Sensitivity analyses were also conducted to evaluate heterogeneity and pleiotropy.

RESULTS

There was no evidence of a statistically significant causal association between the examined phenotypes and epilepsy following Bonferroni correction (p < 1.58 × 10-4) or false discovery rate correction. The results of the MR analysis indicate that the frequency of tiredness or lethargy in the last 2 weeks (p = 0.042), blood uridine (p = 0.003), blood propionylcarnitine (p = 0.041), and free cholesterol (p = 0.044) are suggestive causal risks for epilepsy. Lifestyle choices, such as sleep duration and alcohol consumption, as well as biomarkers including steroid hormone levels, hippocampal volume, and amygdala volume were not identified as causal factors for developing epilepsy (p > 0.05).

CONCLUSIONS

Our study provides additional insights into the underlying causes of epilepsy, which will serve as evidence for the prevention and control of epilepsy. The associations observed in epidemiological studies may be partially attributed to shared biological factors or lifestyle confounders.

Previously reported CCDC26 risk variant and novel germline variants in GALNT13, AR, and MYO10 associated with familial glioma in Finland

Predisposing factors underlying familial aggregation of non-syndromic gliomas are still to be uncovered. Whole-exome sequencing was performed in four Finnish families with brain tumors to identify rare predisposing variants. A total of 417 detected exome variants and 102 previously reported glioma-related variants were further genotyped in 19 Finnish families with brain tumors using targeted sequencing. Rare damaging variants in GALNT13, MYO10 and AR were identified. Two families carried either c.553C>T (R185C) or c.1214T>A (L405Q) on GALNT13. Variant c.553C>T is located on the substrate-binding site of GALNT13. AR c.2180G>T (R727L), which is located on a ligand-binding domain of AR, was detected in two families, one of which also carried a GALNT13 variant. MYO10 c.4448A>G (N1483S) was detected in two families and c.1511C>T (A504V) variant was detected in one family. Both variants are located on functional domains related to MYO10 activity in filopodia formation. In addition, affected cases in six families carried a known glioma risk variant rs55705857 in CCDC26 and low-risk glioma variants. These novel findings indicate polygenic inheritance of familial glioma in Finland and increase our understanding of the genetic contribution to familial glioma susceptibility.

Prevalence of pathogenic germline variants in adult-type diffuse glioma

Background

No consensus germline testing guidelines currently exist for glioma patients, so the prevalence of germline pathogenic variants remains unknown. This study aims to determine the prevalence and type of pathogenic germline variants in adult glioma.

Methods

A retrospective review at a single institution with paired tumor/normal sequencing from August 2018-April 2022 was performed and corresponding clinical data were collected.

Results

We identified 152 glioma patients of which 15 (9.8%) had pathogenic germline variants. Pathogenic germline variants were seen in 11/84 (13.1%) of Glioblastoma, IDH wild type; 3/42 (7.1%) of Astrocytoma, IDH mutant; and 1/26 (3.8%) of Oligodendroglioma, IDH mutant, and 1p/19q co-deleted patients. Pathogenic variants in BRCA2, MUTYH, and CHEK2 were most common (3/15, 20% each). BRCA1 variants occurred in 2/15 (13%) patients, with variants in NF1, ATM, MSH2, and MSH3 occurring in one patient (7%) each. Prior cancer diagnosis was found in 5/15 patients (33%). Second-hit somatic variants were seen in 3/15 patients (20%) in NF1, MUTYH, and MSH2. Referral to genetics was performed in 6/15 (40%) patients with pathogenic germline variants. 14/15 (93%) of patients discovered their pathogenic variant as a result of their paired glioma sequencing.

Conclusions

These findings suggest a possible overlooked opportunity for determination of hereditary cancer syndromes with impact on surveillance as well as potential broader treatment options. Further studies that can determine the role of variants in gliomagenesis and confirm the occurrence and types of pathogenic germline variants in patients with IDH wild type compared to IDH mutant tumors are necessary.

Multi-ancestry genome-wide association study of 4069 children with glioma identifies 9p21.3 risk locus

BACKGROUND

Although recent sequencing studies have revealed that 10% of childhood gliomas are caused by rare germline mutations, the role of common variants is undetermined and no genome-wide significant risk loci for pediatric central nervous system tumors have been identified to date.

METHODS

Meta-analysis of 3 population-based genome-wide association studies comprising 4069 children with glioma and 8778 controls of multiple genetic ancestries. Replication was performed in a separate case-control cohort. Quantitative trait loci analyses and a transcriptome-wide association study were conducted to assess possible links with brain tissue expression across 18 628 genes.

RESULTS

Common variants in CDKN2B-AS1 at 9p21.3 were significantly associated with astrocytoma, the most common subtype of glioma in children (rs573687, P-value of 6.974e-10, OR 1.273, 95% CI 1.179-1.374). The association was driven by low-grade astrocytoma (P-value of 3.815e-9) and exhibited unidirectional effects across all 6 genetic ancestries. For glioma overall, the association approached genome-wide significance (rs3731239, P-value of 5.411e-8), while no significant association was observed for high-grade tumors. Predicted decreased brain tissue expression of CDKN2B was significantly associated with astrocytoma (P-value of 8.090e-8).

CONCLUSIONS

In this population-based genome-wide association study meta-analysis, we identify and replicate 9p21.3 (CDKN2B-AS1) as a risk locus for childhood astrocytoma, thereby establishing the first genome-wide significant evidence of common variant predisposition in pediatric neuro-oncology. We furthermore provide a functional basis for the association by showing a possible link to decreased brain tissue CDKN2B expression and substantiate that genetic susceptibility differs between low- and high-grade astrocytoma.

International patterns and trends in the brain cancer incidence and mortality: An observational study based on the global burden of disease

Background

Brain cancer is a serious issue in the global burden of diseases. This observational research aimed to assess trends of the brain cancer incidence and mortality in the world in the period 1990-2019.

Methods

Brain cancer incidence and mortality data were retrieved from the Global Burden of Disease 2019 study database. The joinpoint regression analysis was done to assess the brain cancer indicence and mortality trends: the average annual percent change (AAPC) along with its 95% confidence interval (95% CI) was calculated.

Results

In both sexes, the highest age-standardized rates of incidence and mortality were found in high-income regions (Europe and America), while the lowest were observed in the African Region. A significant rise in brain cancer incidence rates both in males and females was observed in all regions, with one exception of a significantly decreased trend only among males in the South-East Asia Region. Among countries with increased trends in incidence and mortality from brain cancer, Cuba experienced the most marked increase in both incidence (AAPC = +5.7% in males and AAPC = +5.4% in females) and mortality rates (AAPC = +5.5% in males and AAPC = +5.1% in females). Among countries that experienced a decline in brain cancer incidence and mortality, Hungary and Greenland showed the most marked decline in both sexes (equally by -1.0%).

Conclusion

Brain cancer shows increasing global incidence rates in both sexes and represents a priority for prevention and further research.

Mutational landscape of primary spinal cord astrocytoma

Primary spinal cord astrocytoma (SCA) is a rare disease. Knowledge about the molecular profiles of SCAs mostly comes from intracranial glioma; the pattern of genetic alterations of SCAs is not well understood. Herein, we describe genome-sequencing analyses of primary SCAs, aiming to characterize the mutational landscape of primary SCAs. We utilized whole exome sequencing (WES) to analyze somatic nucleotide variants (SNVs) and copy number variants (CNVs) among 51 primary SCAs. Driver genes were searched using four algorithms. GISTIC2 was used to detect significant CNVs. Additionally, recurrently mutated pathways were also summarized. A total of 12 driver genes were identified. Of those, H3F3A (47.1%), TP53 (29.4%), NF1 (19.6%), ATRX (17.6%), and PPM1D (17.6%) were the most frequently mutated genes. Furthermore, three novel driver genes seldom reported in glioma were identified: HNRNPC, SYNE1, and RBM10. Several germline mutations, including three variants (SLC16A8 rs2235573, LMF1 rs3751667, FAM20C rs774848096) that were associated with risk of brain glioma, were frequently observed in SCAs. Moreover, 12q14.1 (13.7%) encompassing the oncogene CDK4 was recurrently amplified and negatively affected patient prognosis. Besides frequently mutated RTK/RAS pathway and PI3K pathway, the cell cycle pathway controlling the phosphorylation of retinoblastoma protein (RB) was mutated in 39.2% of patients. Overall, a considerable degree of the somatic mutation landscape is shared between SCAs and brainstem glioma. Our work provides a key insight into the molecular profiling of primary SCAs, which might represent candidate drug targets and complement the molecular atlas of glioma. © 2023 The Pathological Society of Great Britain and Ireland.

Role of DNA methylation in the relationship between glioma risk factors and glioma incidence: a two-step Mendelian randomization study

Genetic evidence suggests glioma risk is altered by leukocyte telomere length, allergic disease (asthma, hay fever or eczema), alcohol consumption, childhood obesity, low-density lipoprotein cholesterol (LDLc) and triglyceride levels. DNA methylation (DNAm) variation influences many of these glioma-related traits and is an established feature of glioma. Yet the causal relationship between DNAm variation with both glioma incidence and glioma risk factors is unknown. We applied a two-step Mendelian randomization (MR) approach and several sensitivity analyses (including colocalization and Steiger filtering) to assess the association of DNAm with glioma risk factors and glioma incidence. We used data from a recently published catalogue of germline genetic variants robustly associated with DNAm variation in blood (32,851 participants) and data from a genome-wide association study of glioma risk (12,488 cases and 18,169 controls, sub-divided into 6191 glioblastoma cases and 6305 non-glioblastoma cases). MR evidence indicated that DNAm at 3 CpG sites (cg01561092, cg05926943, cg01584448) in one genomic region (HEATR3) had a putative association with glioma and glioblastoma risk (False discovery rate [FDR] < 0.05). Steiger filtering provided evidence against reverse causation. Colocalization presented evidence against genetic confounding and suggested that differential DNAm at the 3 CpG sites and glioma were driven by the same genetic variant. MR provided little evidence to suggest that DNAm acts as a mediator on the causal pathway between risk factors previously examined and glioma onset. To our knowledge, this is the first study to use MR to appraise the causal link of DNAm with glioma risk factors and glioma onset. Subsequent analyses are required to improve the robustness of our results and rule out horizontal pleiotropy.

Transcriptomic and connectomic correlates of differential spatial patterning among gliomas

Unravelling the complex events driving grade-specific spatial distribution of brain tumour occurrence requires rich datasets from both healthy individuals and patients. Here, we combined open-access data from The Cancer Genome Atlas, the UK Biobank and the Allen Brain Human Atlas to disentangle how the different spatial occurrences of glioblastoma multiforme and low-grade gliomas are linked to brain network features and the normative transcriptional profiles of brain regions. From MRI of brain tumour patients, we first constructed a grade-related frequency map of the regional occurrence of low-grade gliomas and the more aggressive glioblastoma multiforme. Using associated mRNA transcription data, we derived a set of differential gene expressions from glioblastoma multiforme and low-grade gliomas tissues of the same patients. By combining the resulting values with normative gene expressions from post-mortem brain tissue, we constructed a grade-related expression map indicating which brain regions express genes dysregulated in aggressive gliomas. Additionally, we derived an expression map of genes previously associated with tumour subtypes in a genome-wide association study (tumour-related genes). There were significant associations between grade-related frequency, grade-related expression and tumour-related expression maps, as well as functional brain network features (specifically, nodal strength and participation coefficient) that are implicated in neurological and psychiatric disorders. These findings identify brain network dynamics and transcriptomic signatures as key factors in regional vulnerability for glioblastoma multiforme and low-grade glioma occurrence, placing primary brain tumours within a well established framework of neurological and psychiatric cortical alterations.

Association of RNA m7G Modification Gene Polymorphisms with Pediatric Glioma Risk

Glioma stemming from glial cells of the central nervous system (CNS) is one of the leading causes of cancer death in childhood. The genetic predisposition of glioma is not fully understood. METTL1-WDR4 methyltransferase complex is implicated in tumorigenesis by catalyzing N7-methylguanosine (m⁷G) modification of RNA. This study is aimed at determining the association of glioma risk with three polymorphisms (rs2291617, rs10877013, and rs10877012) in METTL1 and five polymorphisms (rs2156315 rs2156316, rs6586250, rs15736, and rs2248490) in WDR4 gene in children of Chinese Han. We enrolled 314 cases and 380 controls from three independent hospitals. Genotypes of these polymorphisms were determined using the TaqMan assay. We found the WDR4 gene rs15736 was significantly associated with reduced glioma risk (GA/AA vs. GG: adjusted odds ratio = 0.63, 95%confidence interval = 0.42 - 0.94, P = 0.023) out of the eight studied polymorphisms. Stratified analyses showed that the association of rs15736 with the risk of glioma remained significant in children aged 60 months or older, girls, the subgroups with astrocytic tumors, or grade I + II glioma. We also found the combined effects of five WDR4 gene polymorphisms on glioma risk. Finally, expression quantitative trait locus (eQTL) analyses elucidated that the rs15736 polymorphism was related to the expression level of WDR4 and neighboring gene cystathionine-beta-synthase (CBS). Our finding provided evidence of a causal association between WDR4 gene polymorphisms and glioma susceptibility in Chinese Han children.

SNP-Target Genes Interaction Perturbing the Cancer Risk in the Post-GWAS

Cancer ranks as the second leading cause of death worldwide, and, being a genetic disease, it is highly heritable. Over the past few decades, genome-wide association studies (GWAS) have identified many risk-associated loci harboring hundreds of single nucleotide polymorphisms (SNPs). Some of these cancer-associated SNPs have been revealed as causal, and the functional characterization of the mechanisms underlying the cancer risk association has been illuminated in some instances. In this review, based on the different positions of SNPs and their modes of action, we discuss the mechanisms underlying how SNPs regulate the expression of target genes to consequently affect tumorigenesis and the development of cancer.

Prediagnostic biomarkers for early detection of glioma—using case–control studies from cohorts as study approach

Background

Understanding the trajectory and development of disease is important and the knowledge can be used to find novel targets for therapy and new diagnostic tools for early diagnosis.

Methods

Large cohorts from different parts of the world are unique assets for research as they have systematically collected plasma and DNA over long-time periods in healthy individuals, sometimes even with repeated samples. Over time, the population in the cohort are diagnosed with many different diseases, including brain tumors.

Results

Recent studies have detected genetic variants that are associated with increased risk of glioblastoma and lower grade gliomas specifically. The impact for genetic markers to predict disease in a healthy population has been deemed low, and a relevant question is if the genetic variants for glioma are associated with risk of disease or partly consist of genes associated to survival. Both metabolite and protein spectra are currently being explored for early detection of cancer.

Conclusions

We here present a focused review of studies of genetic variants, metabolomics, and proteomics studied in prediagnostic glioma samples and discuss their potential in early diagnostics.

Two independent variants of epidermal growth factor receptor associated with risk of glioma in a Korean population

Gliomas are the most common primary tumors in the brain and spinal cord. In previous GWASs, SNPs in epidermal growth factor receptor (EGFR) have been reported as risk loci for gliomas. However, EGFR variants associated with gliomas in the Korean population remain unstudied. This study explored the association of EGFR SNPs with the risk of glioma. We genotyped 13 EGFR exon SNPs in a case-control study that included 324 Korean patients diagnosed with glioma and 480 population-based controls. Statistical analyses of the association between EGFR SNPs and glioma risk were conducted using logistic regression. Both stepwise analysis and conditional logistic analysis were performed to identify independent associations among genotyped variants. We confirmed that two SNPs (rs2227983, rs1050171) were significantly associated with glioma (rs2227983: odds ratio = 1.42, P^corr = 0.009; rs1050171: odds ratio = 1.68, P^corr = 0.005). Additionally, the stepwise analysis and conditional logistic analysis indicated that both SNPs created variants with independent genetic effects. This study is the first to show evidence that functional variants of EGFR, namely, rs2227983 (K521R) and rs1050171 (Q787Q), are associated with an increased risk of glioma in the Korean population. Future work should confirm the functional association between EGFR variants and glioma.

Epidemiological characteristics and genetic alterations in adult diffuse glioma in East Asian populations

Understanding the racial specificities of diseases-such as adult diffuse glioma, the most common primary malignant tumor of the central nervous system-is a critical step toward precision medicine. Here, we comprehensively review studies of gliomas in East Asian populations and other ancestry groups to clarify the racial differences in terms of epidemiology and genomic characteristics. Overall, we observed a lower glioma incidence in East Asians than in Whites; notably, patients with glioblastoma had significantly younger ages of onset and longer overall survival than the Whites. Multiple genome-wide association studies of various cohorts have revealed single nucleotide polymorphisms associated with overall and subtype-specific glioma susceptibility. Notably, only 3 risk loci-5p15.33, 11q23.3, and 20q13.33-were shared between patients with East Asian and White ancestry, whereas other loci predominated only in particular populations. For instance, risk loci 12p11.23, 15q15-21.1, and 19p13.12 were reported in East Asians, whereas risk loci 8q24.21, 1p31.3, and 1q32.1 were reported in studies in White patients. Although the somatic mutational profiles of gliomas between East Asians and non-East Asians were broadly consistent, a lower incidence of EGFR amplification in glioblastoma and a higher incidence of 1p19q-IDH-TERT triple-negative low-grade glioma were observed in East Asian cohorts. By summarizing large-scale disease surveillance, germline, and somatic genomic studies, this review reveals the unique characteristics of adult diffuse glioma among East Asians, to guide clinical management and policy design focused on patients with East Asian ancestry.

Implementation of individualised polygenic risk score analysis: a test case of a family of four

BACKGROUND

Polygenic risk scores (PRS) have been widely applied in research studies, showing how population groups can be stratified into risk categories for many common conditions. As healthcare systems consider applying PRS to keep their populations healthy, little work has been carried out demonstrating their implementation at an individual level.

CASE PRESENTATION

We performed a systematic curation of PRS sources from established data repositories, selecting 15 phenotypes, comprising an excess of 37 million SNPs related to cancer, cardiovascular, metabolic and autoimmune diseases. We tested selected phenotypes using whole genome sequencing data for a family of four related individuals. Individual risk scores were given percentile values based upon reference distributions among 1000 Genomes Iberians, Europeans, or all samples. Over 96 billion allele effects were calculated in order to obtain the PRS for each of the individuals analysed here.

CONCLUSIONS

Our results highlight the need for further standardisation in the way PRS are developed and shared, the importance of individual risk assessment rather than the assumption of inherited averages, and the challenges currently posed when translating PRS into risk metrics.

Association of TP53 rs1042522 C>G Polymorphism with Glioma Risk in Chinese Children

Glioma is the most common intracranial malignancy. TP53 is a crucial tumor suppressor gene that plays an essential regulatory role in cell growth, apoptosis, and DNA repair. The TP53 rs1042522 C>G polymorphism has been reported to be strongly associated with various tumor risks. To assess the TP53 rs1042522 C>G polymorphism with glioma risk in Chinese children, we determined the genotypes of the TP53 rs1042522 C>G polymorphism in 171 glioma patients and 228 cancer-free controls by Taqman assay. We assessed the association of the polymorphism with glioma risk using odds ratio (OR) and 95% confidence interval (CI) generated by logistic regression models. We also performed stratified analyses by age, gender, tumor subtypes, and clinical stages, but no significant association was detected between TP53 rs1042522 C>G polymorphism and childhood glioma risk. These results suggest that the TP53 rs1042522 C>G polymorphism is not associated with glioma risk in Chinese children. Subsequent studies with a larger sample size are needed to validate our results.

CASC15 Gene Polymorphisms and Glioma Susceptibility in Chinese Children

OBJECTIVE

Gliomas are the most common tumors in the central nervous system. The cancer susceptibility candidate 15 (CASC15) gene has been reported to be a susceptibility gene for several types of cancer. No studies have been carried out on the predisposing effect of CASC15 gene single nucleotide polymorphisms (SNPs) on glioma risk.

METHODS

In order to determine whether CASC15 gene SNPs are involved in glioma susceptibility, the first association study in a relatively large sample, which consisted of 171 patients and 228 healthy controls recruited from China, was performed. The contribution of SNPs (rs6939340 A>G, rs4712653 T>C and rs9295536 C>A) to the risk of glioma was evaluated by multinomial logistic regression, based on the calculation of the odds ratio (OR) and 95% confidence interval (CI).

RESULTS

In the single locus and combined analysis, it was revealed that the genetic risk score had no significant associations between CASC15 gene SNPs and glioma risk. However, in the stratified analysis, a significant decrease in risk of glioma was observed in subjects of <60 months old with the rs4712653 TT genotype, when compared to those with the CC/CT genotype (OR=0.12, 95% CI=0.02-0.91, P=0.041).

CONCLUSION

The present study provides referential evidence on the association between the genetic predisposition of the CASC15 gene and glioma risk in Chinese children. However, more well-designed case-control studies and functional experiments are needed to further explore the role of CASC15 gene SNPs.

Inherited genetics of adult diffuse glioma and polygenic risk scores-a review

Knowledge about inherited and acquired genetics of adult diffuse glioma has expanded significantly over the past decade. Genomewide association studies (GWAS) stratified by histologic subtype identified six germline variants that were associated specifically with glioblastoma (GBM) and 12 that were associated with lower grade glioma. A GWAS performed using the 2016 WHO criteria, stratifying patients by IDH mutation and 1p/19q codeletion (as well as TERT promoter mutation), discovered that many of the known variants are associated with specific WHO glioma subtypes. In addition, the GWAS stratified by molecular group identified two additional novel regions: variants in D2HGDH that were associated with tumors that had an IDH mutation and a variant near FAM20C that was associated with tumors that had both IDH mutation and 1p/19q codeletion. The results of these germline associations have been used to calculate polygenic risk scores, from which to estimate relative and absolute risk of overall glioma and risk of specific glioma subtypes. We will review the concept of polygenic risk models and their potential clinical utility, as well as discuss the published adult diffuse glioma polygenic risk models. To date, these prior genetic studies have been done on European populations. Using the published glioma polygenic risk model, we show that the genetic associations published to date do not generalize across genetic ancestries, demonstrating that genetic studies need to be done on more diverse populations.

Genome-Wide Association Study Identifies Multiple Susceptibility Loci for Malignant Neoplasms of the Brain in Taiwan

Primary brain malignancy is a rare tumor with a global incidence of less than 10 per 100,000 people. Hence, there is limited power for identifying risk loci in individual studies, especially for Han Chinese. We performed a genome-wide association study (GWAS) in Taiwan, including 195 cases and 195 controls. We identified five new genes for malignant neoplasms of the brain: EDARADD (rs645507, 1p31.3, p = 7.71 × 10⁻⁵, odds ratio (OR) = 1.893), RBFOX1 (rs8044700, p = 2.35 × 10⁻⁵, OR = 2.36), LMF1 (rs3751667, p = 7.24 × 10⁻⁷, OR = 2.17), DPP6 (rs67433368, p = 8.32 × 10⁻⁵, OR = 3.94), and NDUFB9 (rs7827791, p = 9.73 × 10⁻⁶, OR = 4.42). These data support that genetic susceptibility toward GBM or non-GBM tumors is highly distinct, likely reflecting different etiologies. Combined with signaling analysis, we found that RNA modification may be related to major risk factors in primary malignant neoplasms of the brain.

The Role of Vti1a in Biological Functions and Its Possible Role in Nervous System Disorders

Vesicle transport through interaction with t-SNAREs 1A (Vti1a), a member of the N-ethylmaleimide-sensitive factor attachment protein receptor protein family, is involved in cell signaling as a vesicular protein and mediates vesicle trafficking. Vti1a appears to have specific roles in neurons, primarily by regulating upstream neurosecretory events that mediate exocytotic proteins and the availability of secretory organelles, as well as regulating spontaneous synaptic transmission and postsynaptic efficacy to control neurosecretion. Vti1a also has essential roles in neural development, autophagy, and unconventional extracellular transport of neurons. Studies have shown that Vti1a dysfunction plays critical roles in pathological mechanisms of Hepatic encephalopathy by influencing spontaneous neurotransmission. It also may have an unknown role in amyotrophic lateral sclerosis. A VTI1A variant is associated with the risk of glioma, and the fusion product of the VTI1A gene and the adjacent TCF7L2 gene is involved in glioma development. This review summarizes Vti1a functions in neurons and highlights the role of Vti1a in the several nervous system disorders.

Mitochondrial DNA sequence variation and risk of glioma

BACKGROUND

Malignant gliomas are the most common primary adult brain tumors, with a poor prognosis and ill-defined etiology. Mitochondrial DNA (mtDNA) sequence variation has been linked with certain cancers; however, research on glioma is lacking.

METHODS

We examined the association of common (minor allele frequency ≥ 5%) germline mtDNA variants and haplogroups with glioma risk in 1,566 glioma cases and 1,017 controls from a US case-control study, and 425 glioma cases and 1,534 matched controls from the UK Biobank cohort (UKB). DNA samples were genotyped using the UK Biobank array that included a set of common and rare mtDNA variants. Risk associations were examined separately for glioblastoma (GBM) and lower grade tumors (non-GBM).

RESULTS

In the US study, haplogroup W was inversely associated with glioma when compared with haplogroup H (OR = 0.43, 95%CI: 0.23-0.79); this association was not demonstrated in the UKB (OR = 1.07, 95%CI: 0.47-2.43). In the UKB, the variant m.3010G > A was significantly associated with GBM (OR = 1.32; 95%CI: 1.01-1.73; p = 0.04), but not non-GBM (1.23; 95%CI: 0.78-1.95; p = 0.38); no similar association was observed in the US study. In the US study, the variant m.14798 T > C, was significantly associated with non-GBM (OR = 0.72; 95%CI: 0.53-0.99), but not GBM (OR = 0.86; 95%CI: 0.66-1.11), whereas in the UKB, a positive association was observed between this variant and GBM (OR = 1.46; 95%CI: 1.06-2.02) but not non-GBM (OR = 0.92; 95%CI: 0.52-1.63). None of these associations were significant after adjustment for multiple testing.

CONCLUSION

The association of inherited mtDNA variation, including rare and singleton variants, with glioma risk merits further study.

From GWAS to drug screening: repurposing antipsychotics for glioblastoma

BACKGROUND

Glioblastoma is currently an incurable cancer. Genome-wide association studies have demonstrated that 41 genetic variants are associated with glioblastoma and may provide an option for drug development.

METHODS

We investigated FDA-approved antipsychotics for their potential treatment of glioblastoma based on genome-wide association studies data using a 'pathway/gene-set analysis' approach.

RESULTS

The in-silico screening led to the discovery of 12 candidate drugs. DepMap portal revealed that 42 glioma cell lines show higher sensitivities to 12 candidate drugs than to Temozolomide, the current standard treatment for glioblastoma.

CONCLUSION

In particular, cell lines showed significantly higher sensitivities to Norcyclobenzaprine and Protriptyline which were predicted to bind targets to disrupt a certain molecular function such as DNA repair, response to hormones, or DNA-templated transcription, and may lead to an effect on survival-related pathways including cell cycle arrest, response to ER stress, glucose transport, and regulation of autophagy. However, it is recommended that their mechanism of action and efficacy are further determined.

The Epidemiology of Central Nervous System Tumors

This article reviews the current epidemiology of central nervous system tumors. Population-level basic epidemiology, nationally and internationally, and current understanding of germline genetic risk are discussed, with a focus on known and well-studied risk factors related to the etiology of central nervous system tumors.

Evaluating the prognostic performance of a polygenic risk score for breast cancer risk stratification

BACKGROUND

Polygenic risk scores (PRS) could potentially improve breast cancer screening recommendations. Before a PRS can be considered for implementation, it needs rigorous evaluation, using performance measures that can inform about its future clinical value.

OBJECTIVES

To evaluate the prognostic performance of a regression model with a previously developed, prevalence-based PRS and age as predictors for breast cancer incidence in women from the Estonian biobank (EstBB) cohort; to compare it to the performance of a model including age only.

METHODS

We analyzed data on 30,312 women from the EstBB cohort. They entered the cohort between 2002 and 2011, were between 20 and 89 years, without a history of breast cancer, and with full 5-year follow-up by 2015. We examined PRS and other potential risk factors as possible predictors in Cox regression models for breast cancer incidence. With 10-fold cross-validation we estimated 3- and 5-year breast cancer incidence predicted by age alone and by PRS plus age, fitting models on 90% of the data. Calibration, discrimination, and reclassification were calculated on the left-out folds to express prognostic performance.

RESULTS

A total of 101 (3.33‰) and 185 (6.1‰) incident breast cancers were observed within 3 and 5 years, respectively. For women in a defined screening age of 50-62 years, the ratio of observed vs PRS-age modelled 3-year incidence was 0.86 for women in the 75-85% PRS-group, 1.34 for the 85-95% PRS-group, and 1.41 for the top 5% PRS-group. For 5-year incidence, this was respectively 0.94, 1.15, and 1.08. Yet the number of breast cancer events was relatively low in each PRS-subgroup. For all women, the model's AUC was 0.720 (95% CI: 0.675-0.765) for 3-year and 0.704 (95% CI: 0.670-0.737) for 5-year follow-up, respectively, just 0.022 and 0.023 higher than for the model with age alone. Using a 1% risk prediction threshold, the 3-year NRI for the PRS-age model was 0.09, and 0.05 for 5 years.

CONCLUSION

The model including PRS had modest incremental performance over one based on age only. A larger, independent study is needed to assess whether and how the PRS can meaningfully contribute to age, for developing more efficient screening strategies.

Associations between LMO1 gene polymorphisms and central nervous system tumor susceptibility

IMPORTANCE

LIM domain only 1 (LMO1) gene polymorphisms were previously found to be implicated in the risk of several cancers. No available studies were performed regarding the predisposing effect of LMO1 gene single nucleotide polymorphisms (SNPs) on central nervous system (CNS) tumor risk.

OBJECTIVE

We aimed to determine whether the LMO1 gene SNPs were associated with the risk of CNS tumor by applying a case-control study with 191 cases and 248 controls in China.

METHODS

The contributions of LMO1 gene SNPs to the risk of CNS tumor was evaluated by multinomial logistic regression.

RESULTS

Based on the calculations of odds ratio (OR) and 95% confidence interval (CI), we failed to detect a significant relationship between each LMO1 gene SNP (rs110419 A>G, rs4758051 G>A, rs10840002 A>G, rs204938 A>G, and rs2168101 G>T) and CNS tumor risk, respectively. A negative association was also found in the combined effects on these five SNPs and CNS tumor risk. The stratification analysis further demonstrated the individuals with rs204938 AG/GG genotype confer to increased risk of CNS tumor compared with those with an AA genotype in males (OR: 1.74, 95% CI: 1.01-2.98, P = 0.046).

INTERPRETATION

We concluded that LMO1 gene SNPs may not strong enough to influence the risk of CNS tumor in Chinese children. More studies are required to verify this association.

Relationship between genetically determined telomere length and glioma risk

Background

Telomere maintenance is increasingly recognized as being fundamental to glioma oncogenesis with longer leukocyte telomere length (LTL) reported to increase risk of glioma. To gain further insight into the relationship between telomere genetics and risk of glioma, we conducted several complementary analyses, using genome-wide association studies data on LTL (78 592 individuals) and glioma (12 488 cases and 18 169 controls).

Methods

We performed both classical and summary Mendelian randomization (SMR), coupled with heterogeneity in dependent instruments tests, at genome-wide significant LTL loci to examine if an association was mediated by the same causal variant in glioma. To prioritize genes underscoring glioma-LTL associations, we analyzed gene expression and DNA methylation data.

Results

Genetically increased LTL was significantly associated with increased glioma risk, random-effects inverse variance weighted ORs per 1 SD unit increase in the putative risk factor (odds ratio [OR]_SD) 4.79 (95% confidence interval: 2.11-10.85; P = 1.76 × 10⁻⁴). SMR confirmed the previously reported LTL associations at 3q26.2 (TERC; P_SMR = 1.33 × 10⁻⁵), 5p15.33 (TERT; P_SMR = 9.80 × 10⁻²⁷), 10q24.33 (STN1 alias OBFC1; P_SMR = 4.31 × 10⁻⁵), and 20q13.3 (STMN3/RTEL1; P_SMR = 2.47 × 10⁻⁴) glioma risk loci. Our analysis implicates variation at 1q42.12 (P_SMR = 1.55 × 10⁻²), 6p21.3 (P_SMR = 9.76 × 10⁻³), 6p22.2 (P_SMR = 5.45 × 10⁻³), 7q31.33 (P_SMR = 6.52 × 10⁻³), and 11q22.3 (P_SMR = 8.89 × 10⁻⁴) as risk factors for glioma risk. While complicated by patterns of linkage disequilibrium, genetic variation involving PARP1, PRRC2A, CARMIL1, POT1, and ATM-NPAT1 was implicated in the etiology of glioma.

Conclusions

These observations extend the role of telomere-related genes in the development of glioma.

NBPF4 mitigates progression in colorectal cancer through the regulation of EZH2-associated ETFA

Colorectal cancer (CRC) is one of the leading causes of death worldwide, and hence, there is a need to elucidate the molecular mechanisms contributing to the progression of CRC. In this study, we aimed at assessing the role of long non‐coding RNA NBPF4 on the tumorigenesis of CRC. Silencing or overexpression experiments were performed on HCT116 and SW260 in vitro models. BALB/c athymic female nude mice aged 5–6 weeks were used as in vivo models. To assess the relationship between NBPF4 and its regulatory RNA pull‐down assay, RNA immunoprecipitation, luciferase activity, Western blotting and qRT‐PCR were employed. Initially, we identified that NBPF4 was downregulated in CRC tissues and cell lines. Furthermore, we observed that NBPF4 decreased tumorigenesis in both in vitro and in vivo models. Additionally, we identified that ETFA was highly expressed in CRCs and was negatively associated with NBPF4. Subsequently, we identified that EZH2, a transcriptional factor, activated ETFA by enhancing the methylation of its promoter, and EZH2 was also highly regulated in CRCs. Using COAD and READ databases, we confirmed that EZH2 and ETFA were positively correlated. Furthermore, we identified NBPF4 and EZH2 were targets for ZFP36, which bound and positively regulated NBPF4. This prevented NBPF4 from binding to its negative regulator miR‐17‐3p. Our results demonstrated that NBPF4 downregulated EZH2 and stabilized itself by binding to ZFP36, thus escaping from inhibition by miR‐17‐3p, which allowed mitigation of CRC through inhibition of ETFA.

Genetic variants of CYP4F12 gene are associated with glioma susceptibility

Glioma is a common and fatal primary malignant tumor of the central nervous system, and its prognosis is poor. To determine the susceptibility markers of gliomas in Chinese population we conducted a genome-wide association study (GWAS) of glioma in the Han Chinese population, with a total of 485 glioma cases and 485 controls. Genotyping was conducted using the Applied Biosystems Axiom Precision Medicine Diversity Array. Besides, we carried out imputation using IMPUTE 2.0 software, and the 1000 Genomes Phase 3 was used as the reference panel. The logistic regression model was used to analyze the association of each SNP with glioma risk, assuming an additive genetic model, which was implemented in PLINK version 1.9. Odds ratio (OR) and 95% confidence interval (CI) were estimated from logistic regression analysis with adjustment for age and gender. The results revealed that the SNP (rs688755) in the exon region of CYP4F12 at 19p13.12 reached genome-wide significance associated with gliomas (P = 2.35 × 10^-8 , OR = 3.55, 95% CI = 2.20-5.74). Our findings provide deeper insight into the genetic contribution to glioma in different populations.

A Functional Variant on 9p21.3 Related to Glioma Risk Affects Enhancer Activity and Modulates Expression of CDKN2B-AS1

Genome‐wide association studies have identified SNPs associated with glioma risk on 9p21.3, but biological mechanisms underlying this association are unknown. We tested the hypothesis that a functional SNP on 9p21.3 affects activity of an enhancer, causing altered expression of nearby genes. We considered all SNPs in linkage disequilibrium with the 9p21.3 sentinel SNP rs634537 that mapped to putative enhancers. An enhancer containing rs1537372 exhibited allele‐specific effects on luciferase activity. Deletion of this enhancer in GBM cell lines correlated with decreased expression of CDKN2B‐AS1. Expression quantitative trait loci analysis using non‐diseased brain samples showed rs1537372 to be a consistently significant eQTL for CDKN2B‐AS1. Additionally, our analysis of Hi‐C data generated in neural progenitor cells showed that the bait region containing rs1537372 interacted with the CDKN2B‐AS1 promoter. These data suggest rs1537372, a SNP at the 9p21.3 risk locus, is a functional variant that modulates expression of CDKN2B‐AS1.

Functional analysis of low-grade glioma genetic variants predicts key target genes and transcription factors

BACKGROUND

Large-scale genome-wide association studies (GWAS) have implicated thousands of germline genetic variants in modulating individuals' risk to various diseases, including cancer. At least 25 risk loci have been identified for low-grade gliomas (LGGs), but their molecular functions remain largely unknown.

METHODS

We hypothesized that GWAS loci contain causal single nucleotide polymorphisms (SNPs) that reside in accessible open chromatin regions and modulate the expression of target genes by perturbing the binding affinity of transcription factors (TFs). We performed an integrative analysis of genomic and epigenomic data from The Cancer Genome Atlas and other public repositories to identify candidate causal SNPs within linkage disequilibrium blocks of LGG GWAS loci. We assessed their potential regulatory role via in silico TF binding sequence perturbations, convolutional neural network trained on TF binding data, and simulated annealing-based interpretation methods.

RESULTS

We built an interactive website (http://education.knoweng.org/alg3/) summarizing the functional footprinting of 280 variants in 25 LGG GWAS regions, providing rich information for further computational and experimental scrutiny. We identified as case studies PHLDB1 and SLC25A26 as candidate target genes of rs12803321 and rs11706832, respectively, and predicted the GWAS variant rs648044 to be the causal SNP modulating ZBTB16, a known tumor suppressor in multiple cancers. We showed that rs648044 likely perturbed the binding affinity of the TF MAFF, as supported by RNA interference and in vitro MAFF binding experiments.

CONCLUSIONS

The identified candidate (causal SNP, target gene, TF) triplets and the accompanying resource will help accelerate our understanding of the molecular mechanisms underlying genetic risk factors for gliomas.

Meta-Analyses of Splicing and Expression Quantitative Trait Loci Identified Susceptibility Genes of Glioma

Background

The functions of most glioma risk alleles are unknown. Very few studies had evaluated expression quantitative trait loci (eQTL), and insights of susceptibility genes were limited due to scarcity of available brain tissues. Moreover, no prior study had examined the effect of glioma risk alleles on alternative RNA splicing.

Objective

This study explored splicing quantitative trait loci (sQTL) as molecular QTL and improved the power of QTL mapping through meta-analyses of both cis eQTL and sQTL.

Methods

We first evaluated eQTLs and sQTLs of the CommonMind Consortium (CMC) and Genotype-Tissue Expression Project (GTEx) using genotyping, or whole-genome sequencing and RNA-seq data. Alternative splicing events were characterized using an annotation-free method that detected intron excision events. Then, we conducted meta-analyses by pooling the eQTL and sQTL results of CMC and GTEx using the inverse variance-weighted model. Afterward, we integrated QTL meta-analysis results (Q < 0.05) with the Glioma International Case Control Study (GICC) GWAS meta-analysis (case:12,496, control:18,190), using a summary statistics-based mendelian randomization (SMR) method.

Results

Between CMC and GTEx, we combined the QTL data of 354 unique individuals of European ancestry. SMR analyses revealed 15 eQTLs in 11 loci and 32 sQTLs in 9 loci relevant to glioma risk. Two loci only harbored sQTLs (1q44 and 16p13.3). In seven loci, both eQTL and sQTL coexisted (2q33.3, 7p11.2, 11q23.3 15q24.2, 16p12.1, 20q13.33, and 22q13.1), but the target genes were different for five of these seven loci. Three eQTL loci (9p21.3, 20q13.33, and 22q13.1) and 4 sQTL loci (11q23.3, 16p13.3, 16q12.1, and 20q13.33) harbored multiple target genes. Eight target genes of sQTLs (C2orf80, SEC61G, TMEM25, PHLDB1, RP11-161M6.2, HEATR3, RTEL1-TNFRSF6B, and LIME1) had multiple alternatively spliced transcripts.

Conclusion

Our study revealed that the regulation of transcriptome by glioma risk alleles is complex, with the potential for eQTL and sQTL jointly affecting gliomagenesis in risk loci. QTLs of many loci involved multiple target genes, some of which were specific to alternative splicing. Therefore, quantitative trait loci that evaluate only total gene expression will miss many important target genes.

Genetic variants in m6A modification core genes are associated with glioma risk in Chinese children

Glioma is a highly heritable disease with a strong genetic component. The N6-methyladenosine (m⁶A) modification core genes play important roles in the context of cancer. However, the effects of polymorphisms in the m⁶A modification core genes on the risk of pediatric glioma remain undefined. Here, we intended to demonstrate the relationship between 24 functional single-nucleotide polymorphisms (SNPs) in eight m⁶A modification core genes and glioma risk. Case-control design and multinomial logistic regression were used to develop models to estimate the risk of glioma while accounting for the subtypes of glioma. A total of 171 glioma cases and 228 controls from South China were genotyped using a TaqMan assay. The WTAP rs7766006, YTHDF2 rs3738067, and FTO rs9939609 variants conferred a statistically significant increased risk of glioma, respectively. YTHDC1 rs2293595, YTHDC1 rs3813832, and FTO rs8047395 were associated with a significant inverse association with risk of glioma, respectively. The significant associations were more predominant in stratification analyses of certain subgroups. Functional annotations revealed that WTAP rs7766006 and YTHDF2 rs3738067 could be potential functional variants by increasing expression of WTAP and YTHDF2 mRNA, respectively. Overall, these findings implicate variants in the m⁶A modification core genes as playing a role in pediatric glioma etiology.

Lack of association between modifiable exposures and glioma risk: a Mendelian randomization analysis

Background

The etiological basis of glioma is poorly understood. We have used genetic markers in a Mendelian randomization (MR) framework to examine if lifestyle, cardiometabolic, and inflammatory factors influence the risk of glioma. This methodology reduces bias from confounding and is not affected by reverse causation.

Methods

We identified genetic instruments for 37 potentially modifiable risk factors and evaluated their association with glioma risk using data from a genome-wide association study of 12 488 glioma patients and 18 169 controls. We used the estimated odds ratio of glioma associated with each of the genetically defined traits to infer evidence for a causal relationship with the following exposures:

Lifestyle and dietary factors—height, plasma insulin-like growth factor 1, blood carnitine, blood methionine, blood selenium, blood zinc, circulating adiponectin, circulating carotenoids, iron status, serum calcium, vitamins (A1, B12, B6, E, and 25-hydroxyvitamin D), fatty acid levels (monounsaturated, omega-3, and omega-6) and circulating fetuin-A;

Cardiometabolic factors—birth weight, high density lipoprotein cholesterol, low density lipoprotein cholesterol, total cholesterol, total triglycerides, basal metabolic rate, body fat percentage, body mass index, fasting glucose, fasting proinsulin, glycated hemoglobin levels, diastolic and systolic blood pressure, waist circumference, waist-to-hip ratio; and

Inflammatory factors— C-reactive protein, plasma interleukin-6 receptor subunit alpha and serum immunoglobulin E.

Results

After correction for the testing of multiple potential risk factors and excluding associations driven by one single nucleotide polymorphism, no significant association with glioma risk was observed (ie, P_Corrected > 0.05).

Conclusions

This study did not provide evidence supporting any of the 37 factors examined as having a significant influence on glioma risk.

XPG gene polymorphisms and glioma susceptibility: a two-centre case-control study

Background: Glioma, the most common tumour in children next to leukaemia, is difficult to treat, with a poor prognosis and high recurrence rate. Xeroderma pigmentosum group G (XPG) plays a key role in the nucleotide excision repair pathway, which may modulate individual susceptibility to developing cancer. We hypothesized links between XPG variants and glioma in children.Methods: We tested our hypothesis in a study comparing 171 glioma cases with 228 age and sex matched controls, determining XPG polymorphisms rs2094258 C > T, rs751402 C > T, rs2296147 T > C, rs1047768 T > C, rs873601 G > A by standard molecular genetic methods.Results: rs2094258 C > T was associated with a decreased glioma risk, but carrying the rs1047768 C or rs873601 A allele brought an increased risk. Subjects carrying 5 risk genotypes had a significantly increased glioma risk at an adjusted odds ratio of 1.97 (95% confidence Interval 1.26-3.08)(p = 0.003) when compared with those carrying 0-4 risk genotypes. Furthermore, children with 5 risk genotypes had a higher glioma risk when aged >60 months, were more likely to be male, and with subtypes of astrocytic tumours, and low-grade clinical stage, when compared to those with 0-4 risk genotypes. Preliminary functional exploration suggested that rs2094258 is linked with the expression of its surrounding genes in the expression quantitative trait locus analysis.Conclusion: Certain variants of XPG are risk factors for paediatric glioma, and so may be useful in early diagnosis.

Germline ALK variations are associated with a poor prognosis in glioma and IDH-wildtype glioblastoma

BACKGROUND

Glioma is the most common primary brain tumor. Clear classification is crucial for accurate diagnosis and individualized treatment. Histopathological characteristics and genetic alterations have shown to be related to prognosis and treatment response. Germline variants are important components of genetic alterations. However, the distribution of germline variations in glioma patients and their association with survival remain unknown.

METHODS

We carried out whole-exome sequencing on 99 cases to explore germline variants in glioma. We also analyzed the association of germline variants with clinicopathological features and other prognostic indicators.

RESULTS

All the glioma cases harbored rare germline variants. Germline ALK variants (gALK-Mut) were identified in 12/99 (12.12%) patients. The gALK-Mut patients had significantly shorter overall survival than germline ALK wildtype (gALK-WT) patients in the all glioma group (99 cases) and the subset of patients with IDH-wildtype glioblastoma (IDH-WT-GBM, 39 cases) (P = 0.013 and 0.027, respectively). The gALK-Mut patients also had higher frequency of BIRC5, PIK3CA and RPN1 somatic mutations than the gALK-WT patients in IDH-WT-GBM. Other confounding factors appeared to contribute to patient survival. The subgroup of patients in IDH-WT-GBM with gALK-Mut/TP53-Mut had worse prognosis than the gALK-WT/TP53-Mut subgroup (P = 0.031); The gALK-Mut/TERT-WT and gALK-Mut/TERT-Mut subgroups both had a worse prognosis than the gALK-WT/TERT-Mut subgroup (P = 0.031 and 0.018, respectively).

CONCLUSIONS

Our study revealed ALK variation was an independent indicator of poor prognosis in glioma and IDH-WT-GBM. It could be a promising biomarker and tractable therapeutic target for this deadly disease.

No Association Between FTO Gene Polymorphisms and Central Nervous System Tumor Susceptibility in Chinese Children

Background

Central nervous system (CNS) tumor is a malignancy commonly seen occurring in childhood, worldwide. Fat mass and obesity-associated (FTO) enzyme, initially identified as an obesity-related protein, also functions as a susceptibility gene for cancers. However, predisposing effect of FTO gene single nucleotide polymorphisms (SNPs) on CNS tumor risk remains unknown.

Methods

Herein, we genotyped 314 CNS tumor patients and 380 healthy controls samples from three hospitals to explore whether FTO gene SNPs impact CNS tumor risk. TaqMan SNP genotyping assay was applied for the genotyping. Odds ratios (ORs) and 95% confidence intervals (CIs), generated from multinomial logistic regression, were applied to determine the associations of SNPs (rs1477196 G>A, rs9939609 T>A, rs7206790 C>G, and rs8047395 A>G) in FTO gene with risk of CNS tumor.

Results

We failed to detect significant associations between FTO gene SNPs and CNS tumor risk, either in single-locus or combined analysis. A significantly increased ependymoma risk was found for carriers with 3-4 risk genotypes in comparison to 0-2 risk genotypes (adjusted OR=1.94, 95% CI=1.11-3.37, P=0.020).

Conclusion

Our data indicated that FTO gene SNPs are unlikely to have large effects on CNS tumor risk but may have weaker effects.

Searching for causal relationships of glioma: a phenome-wide Mendelian randomisation study

BACKGROUND

The aetiology of glioma is poorly understood. Summary data from genome-wide association studies (GWAS) can be used in a Mendelian randomisation (MR) phenome-wide association study (PheWAS) to search for glioma risk factors.

METHODS

We performed an MR-PheWAS analysing 316 phenotypes, proxied by 8387 genetic variants, and summary genetic data from a GWAS of 12,488 glioma cases and 18,169 controls. Causal effects were estimated under a random-effects inverse-variance-weighted (IVW-RE) model, with robust adjusted profile score (MR-RAPS), weighted median and mode-based estimates computed to assess the robustness of findings. Odds ratios per one standard deviation increase in each phenotype were calculated for all glioma, glioblastoma (GBM) and non-GBM tumours.

RESULTS

No significant associations (P < 1.58 × 10-4) were observed between phenotypes and glioma under the IVW-RE model. Suggestive associations (1.58 × 10-4 < P < 0.05) were observed between leukocyte telomere length (LTL) with all glioma (ORSD = 3.91, P = 9.24 × 10-3) and GBM (ORSD = 4.86, P = 3.23 × 10-2), but the association was primarily driven by the TERT variant rs2736100. Serum low-density lipoprotein cholesterol and plasma HbA1C showed suggestive associations with glioma (ORSD = 1.11, P = 1.39 × 10-2 and ORSD = 1.28, P = 1.73 × 10-2, respectively), both associations being reliant on single genetic variants.

CONCLUSIONS

Our study provides further insight into the aetiological basis of glioma for which published data have been mixed.

Adult diffuse glioma GWAS by molecular subtype identifies variants in D2HGDH and FAM20C

BACKGROUND

Twenty-five germline variants are associated with adult diffuse glioma, and some of these variants have been shown to be associated with particular subtypes of glioma. We hypothesized that additional germline variants could be identified if a genome-wide association study (GWAS) were performed by molecular subtype.

METHODS

A total of 1320 glioma cases and 1889 controls were used in the discovery set and 799 glioma cases and 808 controls in the validation set. Glioma cases were classified into molecular subtypes based on combinations of isocitrate dehydrogenase (IDH) mutation, telomerase reverse transcriptase (TERT) promoter mutation, and 1p/19q codeletion. Logistic regression was applied to the discovery and validation sets to test for associations of variants with each of the subtypes. A meta-analysis was subsequently performed using a genome-wide P-value threshold of 5 × 10-8.

RESULTS

Nine variants in or near D-2-hydroxyglutarate dehydrogenase (D2HGDH) on chromosome 2 were genome-wide significant in IDH-mutated glioma (most significant was rs5839764, meta P = 2.82 × 10-10). Further stratifying by 1p/19q codeletion status, one variant in D2HGDH was genome-wide significant in IDH-mutated non-codeleted glioma (rs1106639, meta P = 4.96 × 10-8). Further stratifying by TERT mutation, one variant near FAM20C (family with sequence similarity 20, member C) on chromosome 7 was genome-wide significant in gliomas that have IDH mutation, TERT mutation, and 1p/19q codeletion (rs111976262, meta P = 9.56 × 10-9). Thirty-six variants in or near GMEB2 on chromosome 20 near regulator of telomere elongation helicase 1 (RTEL1) were genome-wide significant in IDH wild-type glioma (most significant was rs4809313, meta P = 2.60 × 10-10).

CONCLUSIONS

Performing a GWAS by molecular subtype identified 2 new regions and a candidate independent region near RTEL1, which were associated with specific glioma molecular subtypes.

A functional variant on 20q13.33 related to glioma risk alters enhancer activity and modulates expression of multiple genes

Genome‐wide association studies (GWAS) have identified single‐nucleotide polymorphisms (SNPs) associated with glioma risk on 20q13.33, but the biological mechanisms underlying this association are unknown. We tested the hypothesis that a functional SNP on 20q13.33 impacted the activity of an enhancer, leading to an altered expression of nearby genes. To identify candidate functional SNPs, we identified all SNPs in linkage disequilibrium with the risk‐associated SNP rs2297440 that mapped to putative enhancers. Putative enhancers containing candidate functional SNPs were tested for allele‐specific effects in luciferase enhancer activity assays against glioblastoma multiforme (GBM) cell lines. An enhancer containing SNP rs3761124 exhibited allele‐specific effects on activity. Deletion of this enhancer by CRISPR‐Cas9 editing in GBM cell lines correlated with an altered expression of multiple genes, including STMN3, RTEL1, RTEL1‐TNFRSF6B, GMEB2, and SRMS. Expression quantitative trait loci (eQTL) analyses using nondiseased brain samples, isocitrate dehydrogenase 1 (IDH1) wild‐type glioma, and neurodevelopmental tissues showed STMN3 to be a consistent significant eQTL with rs3761124. RTEL1 and GMEB2 were also significant eQTLs in the context of early CNS development and/or in IDH1 wild‐type glioma. We provide evidence that rs3761124 is a functional variant on 20q13.33 related to glioma/GBM risk that modulates the expression of STMN3 and potentially other genes across diverse cellular contexts.

Cancer-driving mutations and variants of components of the membrane trafficking core machinery

The core machinery for vesicular membrane trafficking broadly comprises of coat proteins, RABs, tethering complexes and SNAREs. As cellular membrane traffic modulates key processes of mitogenic signaling, cell migration, cell death and autophagy, its dysregulation could potentially results in increased cell proliferation and survival, or enhanced migration and invasion. Changes in the levels of some components of the core machinery of vesicular membrane trafficking, likely due to gene amplifications and/or alterations in epigenetic factors (such as DNA methylation and micro RNA) have been extensively associated with human cancers. Here, we provide an overview of association of membrane trafficking with cancer, with a focus on mutations and variants of coat proteins, RABs, tethering complex components and SNAREs that have been uncovered in human cancer cells/tissues. The major cellular and molecular cancer-driving or suppression mechanisms associated with these components of the core membrane trafficking machinery shall be discussed.

Vesicle transport through interaction with t-SNAREs 1a (Vti1a)'s roles in neurons

The Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) family mediates membrane fusion during membrane trafficking and autophagy in all eukaryotic cells, with a number of SNAREs having cell type-specific functions. The endosome-trans-Golgi network (TGN) localized SNARE, Vesicle transport through interaction with t-SNAREs 1A (Vti1a), is unique among SNAREs in that it has numerous neuron-specific functions. These include neurite outgrowth, nervous system development, spontaneous neurotransmission, synaptic vesicle and dense core vesicle secretion, as well as a process of unconventional surface transport of the Kv4 potassium channel. Furthermore, the human VT11A gene is known to form fusion products with neighboring genes in cancer tissues, and VT11A variants are associated with risk in cancers, including glioma. In this review, I highlight VTI1A's known physio-pathological roles in brain neurons, as well as unanswered questions in these regards.

Molecular characteristics of diffuse lower grade gliomas: what neurosurgeons need to know

The importance of genomic information in intrinsic brain tumors is highlighted in the World Health Organization (WHO) 2016 classification of gliomas, which now incorporates both phenotype and genotype data to assign a diagnosis. By using genetic markers to both categorize tumors and advise patients on prognosis, this classification system has minimized the risk of tissue sampling error, improved diagnostic accuracy, and reduced inter-rater variability. In the neurosurgical community, it is critical to understand the role genetics plays in tumor biology, what certain mutations mean for the patient's prognosis and adjuvant treatment, and how to interpret the results of sequencing data that are generated following tumor resection. In this review, we examine the critical role of genetics for diagnosis and prognosis and highlight the importance of tumor genetics for neurosurgeons caring for patients with diffuse lower grade gliomas.

The Non-coding Side of Medulloblastoma

Medulloblastoma (MB) is the most common pediatric brain tumor and a primary cause of cancer-related death in children. Until a few years ago, only clinical and histological features were exploited for MB pathological classification and outcome prognosis. In the past decade, the advancement of high-throughput molecular analyses that integrate genetic, epigenetic, and expression data, together with the availability of increasing wealth of patient samples, revealed the existence of four molecularly distinct MB subgroups. Their further classification into 12 subtypes not only reduced the well-characterized intertumoral heterogeneity, but also provided new opportunities for the design of targets for precision oncology. Moreover, the identification of tumorigenic and self-renewing subpopulations of cancer stem cells in MB has increased our knowledge of its biology. Despite these advancements, the origin of MB is still debated, and its molecular bases are poorly characterized. A major goal in the field is to identify the key genes that drive tumor growth and the mechanisms through which they are able to promote tumorigenesis. So far, only protein-coding genes acting as oncogenic drivers have been characterized in each MB subgroup. The contribution of the non-coding side of the genome, which produces a plethora of transcripts that control fundamental biological processes, as the cell choice between proliferation and differentiation, is still unappreciated. This review wants to fill this major gap by summarizing the recent findings on the impact of non-coding RNAs in MB initiation and progression. Furthermore, their potential role as specific MB biomarkers and novel therapeutic targets is also highlighted.

Transcriptomic Analyses for Identification and Prioritization of Genes Associated With Alzheimer's Disease in Humans

Long non-coding RNAs (lncRNAs), as important ncRNA regulators, play crucial roles in the regulation of various biological processes, and their aberrant expression is related to the occurrence and development of diseases, which is gradually validated by more and more studies. Alzheimer’s disease (AD) is a chronic neurodegenerative disease that often develops slowly and gradually deteriorates over time. However, which functions the lncRNAs perform in AD are almost unknown. In this study, we performed transcriptome analysis in AD, containing 12,892 known lncRNAs and 19,053 protein-coding genes (PCGs). Further, 14 down-regulated and 39 up-regulated lncRNAs were identified, compared with normal brain samples, which indicated that these lncRNAs might play critical roles in the pathogenesis of AD. In addition, 19 down-regulated and 28 up-regulated PCGs were also detected. Using the differentially expressed lncRNAs and PCGs through the WGCNA method, an lncRNA–mRNA co-expressed network was constructed. The results showed that lncRNAs RP3-522J7, MIR3180-2, and MIR3180-3 were frequently co-expressed with known AD risk PCGs. Interestingly, PCGs in the network are significantly enriched in brain- or AD-related biological functions, including the brain renin–angiotensin system, cell adhesion, neuroprotective role of THOP1 in AD, and so on. Furthermore, it was shown that 18 lncRNAs and 7 PCGs were highly expressed in normal brain tissue relative to other normal tissue types, suggesting their potential as diagnostic markers of AD, especially RP3-522J7, MIR3180-2, MIR3180-3, and CTA-929C8. In total, our study identified a compendium of AD-related dysregulated lncRNAs and characterized the corresponding biological functions of these lncRNAs in AD, which will be helpful to understand the molecular basis and pathogenesis of AD.

Dissecting Molecular Features of Gliomas: Genetic Loci and Validated Biomarkers

Recently, several studies focused on the genetics of gliomas. This allowed identifying several germline loci that contribute to individual risk for tumor development, as well as various somatic mutations that are key for disease classification. Unfortunately, none of the germline loci clearly confers increased risk per se. Contrariwise, somatic mutations identified within the glioma tissue define tumor genotype, thus representing valid diagnostic and prognostic markers. Thus, genetic features can be used in glioma classification and guided therapy. Such copious genomic variabilities are screened routinely in glioma diagnosis. In detail, Sanger sequencing or pyrosequencing, fluorescence in-situ hybridization, and microsatellite analyses were added to immunohistochemistry as diagnostic markers. Recently, Next Generation Sequencing was set-up as an all-in-one diagnostic tool aimed at detecting both DNA copy number variations and mutations in gliomas. This approach is widely used also to detect circulating tumor DNA within cerebrospinal fluid from patients affected by primary brain tumors. Such an approach is providing an alternative cost-effective strategy to genotype all gliomas, which allows avoiding surgical tissue collection and repeated tumor biopsies. This review summarizes available molecular features that represent solid tools for the genetic diagnosis of gliomas at present or in the next future.

The Genetic Architecture of Gliomagenesis-Genetic Risk Variants Linked to Specific Molecular Subtypes

Genome-wide association studies have identified 25 germline genetic loci that increase the risk of glioma. The somatic tumor molecular alterations, including IDH-mutation status and 1p/19q co-deletion, have been included into the WHO 2016 classification system for glioma. To investigate how the germline genetic risk variants correlate with the somatic molecular subtypes put forward by WHO, we performed a meta-analysis that combined findings from 330 Swedish cases and 876 controls with two other recent studies. In total, 5,103 cases and 10,915 controls were included. Three categories of associations were found. First, variants in TERT and TP53 were associated with increased risk of all glioma subtypes. Second, variants in CDKN2B-AS1, EGFR, and RTEL1 were associated with IDH-wildtype glioma. Third, variants in CCDC26 (the 8q24 locus), C2orf80 (close to IDH), LRIG1, PHLDB1, ETFA, MAML2 and ZBTB16 were associated with IDH-mutant glioma. We therefore propose three etiopathological pathways in gliomagenesis based on germline variants for future guidance of diagnosis and potential functional targets for therapies. Future prospective clinical trials of patients with suspicion of glioma diagnoses, using the genetic variants as biomarkers, are necessary to disentangle how strongly they can predict glioma diagnosis.

Risk factors for childhood and adult primary brain tumors

Primary brain tumors account for ~1% of new cancer cases and ~2% of cancer deaths in the United States; however, they are the most commonly occurring solid tumors in children. These tumors are very heterogeneous and can be broadly classified into malignant and benign (or non-malignant), and specific histologies vary in frequency by age, sex, and race/ethnicity. Epidemiological studies have explored numerous potential risk factors, and thus far the only validated associations for brain tumors are ionizing radiation (which increases risk in both adults and children) and history of allergies (which decreases risk in adults). Studies of genetic risk factors have identified 32 germline variants associated with increased risk for these tumors in adults (25 in glioma, 2 in meningioma, 3 in pituitary adenoma, and 2 in primary CNS lymphoma), and further studies are currently under way for other histologic subtypes, as well as for various childhood brain tumors. While identifying risk factors for these tumors is difficult due to their rarity, many existing datasets can be leveraged for future discoveries in multi-institutional collaborations. Many institutions are continuing to develop large clinical databases including pre-diagnostic risk factor data, and developments in molecular characterization of tumor subtypes continue to allow for investigation of more refined phenotypes. Key Point 1. Brain tumors are a heterogeneous group of tumors that vary significantly in incidence by age, sex, and race/ethnicity.2. The only well-validated risk factors for brain tumors are ionizing radiation (which increases risk in adults and children) and history of allergies (which decreases risk).3. Genome-wide association studies have identified 32 histology-specific inherited genetic variants associated with increased risk of these tumors.

Genome-wide association and epidemiological analyses reveal common genetic origins between uterine leiomyomata and endometriosis

Uterine leiomyomata (UL) are the most common neoplasms of the female reproductive tract and primary cause for hysterectomy, leading to considerable morbidity and high economic burden. Here we conduct a GWAS meta-analysis in 35,474 cases and 267,505 female controls of European ancestry, identifying eight novel genome-wide significant (P < 5 × 10^-8) loci, in addition to confirming 21 previously reported loci, including multiple independent signals at 10 loci. Phenotypic stratification of UL by heavy menstrual bleeding in 3409 cases and 199,171 female controls reveals genome-wide significant associations at three of the 29 UL loci: 5p15.33 (TERT), 5q35.2 (FGFR4) and 11q22.3 (ATM). Four loci identified in the meta-analysis are also associated with endometriosis risk; an epidemiological meta-analysis across 402,868 women suggests at least a doubling of risk for UL diagnosis among those with a history of endometriosis. These findings increase our understanding of genetic contribution and biology underlying UL development, and suggest overlapping genetic origins with endometriosis.

TERT rs10069690 polymorphism and cancers risk: A meta-analysis

BACKGROUND

Studies have identified that the telomerase reverse transcriptase (TERT) gene polymorphism rs10069690 (C>T) is associated with cancer risk, but the results remain inconclusive.

METHODS

To provide a more precise estimation of the relationship, we performed a meta-analysis of 45 published studies including 329,035 cases and 730,940 controls. We conducted a search in PubMed, Google Scholar and Web of Science to select studies on the association between rs10069690 and cancer risk. Stratification by ethnicity, cancer type, cancers' classification, source of control, sample size, and genotype method was used to explore the source of heterogeneity. The pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were evaluated using random effects models. Sensitivity, publication bias, false-positive report probability (FPRP) and statistical power were also assessed.

RESULTS

The result demonstrated that rs10069690 was significantly associated with an increased risk of cancer overall (OR = 1.09, 95% CI: 1.06-1.12, p < .001) under the allele model. Stratification analysis revealed an increased cancer risk in subgroups of breast cancer, ovarian cancer, lung cancer, thyroid cancer, and renal cell carcinoma (RCC). However, a significantly decreased association was observed in pancreatic cancer in the European population (OR = 0.93,95% CI: 0.87-0.99, p = .031). In the subgroup analysis based on cancer type, no significant association was found in prostate cancer, leukemia, colorectal cancer and glioma.

CONCLUSIONS

This meta-analysis suggested that the TERT rs10069690 polymorphism may be a risk factor for cancer, especially breast cancer, ovarian cancer, lung cancer, thyroid cancer, and RCC. Further functional studies are warranted to reveal the role of the polymorphism in carcinogenesis.