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A comparative study of microstructure parameters and mechanical property characteristics of consolidated Ni3Al samples formed by spark plasma sintering after a preliminary short-term mechanical activation and mixing in a mortar is carried out. It is found out that the grain size of the mechanically pre-activated material is several times smaller than that of the material sintered after mixing in a mortar. This feature is manifested in the differences in the values of microhardness and short-term strength. The annealing temperature effect on the structure parameters and mechanical properties of Ni3Al samples is revealed depending on the pretreatment. It is assumed that the formation of a high-defect structural state, characterized by fine grains combined with an increased level of microdistortions, during mechanical activation predetermines the strength properties of the material both after spark plasma sintering and after deformation and heat treatment.

The results of studying the microstructure and mechanical properties of the V-W-Cr alloy after different regimes of thermomechanical treatment are presented. It is shown that the use of the modified regime promotes the formation of a more uniform grain structure, which provides an increase in strength properties at room temperature by more than 10%. Analysis and comparison of the results showed that the thermal stability and the level of strength properties of V-Me(Cr, W)-Zr(C, O, N)-system alloys are mainly provided by the effects of disperse strengthening with stable Zr-based particles.

A study of the features of relaxation processes activation in Ni3Al samples obtained by ball milling and subsequent spark plasma sintering (SPS) was carried out. The effect of the duration of the preliminary high-energy ball milling (HEBM) on the activation of structural relaxation processes at temperatures above and below the SPS temperature was revealed. It was found that at temperatures above the synthesis temperature, the main relaxation processes are associated with the activation of primary recrystallization in the most defective regions, that consist of grains of submicron sizes. It was shown that the temperature of activation of high-defect states relaxation in SPS samples of Ni3Al decreases with an increase in the duration of the preliminary HEBM.

Background: The genetic etiology of osteosarcoma remains poorly understood despite the publication of a genome-wide association study. Association between HLA genetic variants and risk of several cancers has been observed, but HLA variation is not well captured by standard SNP arrays.Methods: We genotyped 207 Californian pediatric osteosarcoma cases and 696 controls of European ancestry using a custom genome-wide array supplemented with approximately 6,000 additional probes across the MHC region. We subsequently imputed 4-digit classical HLA alleles using a reference panel of 5,225 individuals who underwent high-resolution HLA typing via next-generation sequencing. Case-control comparisons were adjusted for ancestry-informative principal components, and top associations from the discovery analysis underwent replication in an independent dataset of 657 cases and 1,183 controls.Results: Three highly correlated HLA class II variants (r 2 = 0.33-0.98) were associated with osteosarcoma risk in discovery analyses, including HLA-DRB1*0301 (OR = 0.52; P = 3.2 × 10-3), HLA-DQA1*0501 (OR = 0.74; P = 0.031), and HLA-DQB1*0201 (OR = 0.51; P = 2.7 × 10-3). Similar associations were observed in the replication data (P range = 0.011-0.037). Meta-analysis of the two datasets identified HLA-DRB1*0301 as the most significantly associated variant (ORmeta = 0.62; P meta = 1.5 × 10-4), reaching Bonferroni-corrected statistical significance. The meta-analysis also revealed a second significant independent signal at HLA-DQA1*01:01 (ORmeta = 1.33, P meta = 1.2 × 10-3), and a third suggestive association at HLA-DQB1*0302 (ORmeta = 0.73, P meta = 6.4 × 10-3).Conclusions: Multiple independent HLA class II alleles may influence osteosarcoma risk.Impact: Additional work is needed to extend our observations to other patient populations and to clarify the potential causal mechanisms underlying these associations. Understanding immunologic contributions to the etiology of osteosarcoma may inform rational therapeutic targets. Cancer Epidemiol Biomarkers Prev; 27(10); 1151-8. ©2018 AACR.

BackgroundAlthough increased height has been associated with osteosarcoma risk in previous epidemiologic studies, to the authors' knowledge the relative contribution of stature during different developmental timepoints remains unclear. Furthermore, the question of how genetic determinants of height impact osteosarcoma etiology remains unexplored. Genetic variants associated with stature in previous genome-wide association studies may be biomarkers of osteosarcoma risk.MethodsThe authors tested the associations between osteosarcoma risk and polygenic scores for adult height (416 variants), childhood height (6 variants), and birth length (5 variants) in 864 osteosarcoma cases and 1879 controls of European ancestry.ResultsEach standard deviation increase in the polygenic score for adult height, corresponding to a 1.7-cm increase in stature, was found to be associated with a 1.10-fold increase in the risk of osteosarcoma (95% confidence interval [95% CI], 1.01-1.19; P =.027). Each standard deviation increase in the polygenic score for childhood height, corresponding to a 0.5-cm increase in stature, was associated with a 1.10-fold increase in the risk of osteosarcoma (95% CI, 1.01-1.20; P =.023). The polygenic score for birth length was not found to be associated with osteosarcoma risk (P =.11). When adult and childhood height scores were modeled together, they were found to be independently associated with osteosarcoma risk (P =.037 and P = .043, respectively). An expression quantitative trait locus for cartilage intermediate layer protein 2 (CILP2), rs8103992, was significantly associated with osteosarcoma risk after adjustment for multiple comparisons (odds ratio, 1.35; 95% CI, 1.16-1.56 [P = 7.93×10-5 and Padjusted =.034]).ConclusionsA genetic propensity for taller adult and childhood height attainments contributed independently to osteosarcoma risk in the current study data. These results suggest that the biological pathways affecting normal bone growth may be involved in osteosarcoma etiology.

Although genome-wide association studies have identified several susceptibility loci for adult glioma, little is known regarding the potential contribution of genetic variation in the human leukocyte antigen (HLA) region to glioma risk. HLA associations have been reported for various malignancies, with many studies investigating selected candidate HLA polymorphisms. However, no systematic analysis has been conducted in glioma patients, and no investigation into potential non-additive effects has been described. We conducted comprehensive genetic analyses of HLA variants among 1746 adult glioma patients and 2312 controls of European-ancestry from the GliomaScan Consortium. Genotype data were generated with the Illumina 660-Quad array, and we imputed HLA alleles using a reference panel of 5225 individuals in the Type 1 Diabetes Genetics Consortium who underwent high-resolution HLA typing via next-generation sequencing. Case-control comparisons were adjusted for population stratification using ancestry-informative principal components. Because alleles in different loci across the HLA region are linked, we created multigene haplotypes consisting of the genes DRB1, DQA1, and DQB1. Although none of the haplotypes were associated with glioma in additive models, inclusion of a dominance term significantly improved the model for multigene haplotype HLA-DRB1*1501-DQA1*0102-DQB1*0602 (P = 0.002). Heterozygous carriers of the haplotype had an increased risk of glioma [odds ratio (OR) 1.23; 95% confidence interval (CI) 1.01-1.49], while homozygous carriers were at decreased risk compared with non-carriers (OR 0.64; 95% CI 0.40-1.01). Our results suggest that the DRB1*1501-DQA1*0102-DQB1*0602 haplotype may contribute to the risk of glioma in a non-additive manner, with the positive dominance effect partly explained by an epistatic interaction with HLA-DRB1*0401-DQA1*0301-DQB1*0301.

BackgroundChronic lymphocytic leukemia (CLL) is the most common leukemia in the Western world. Shorter mean telomere length in leukemic cells has been associated with more aggressive disease. Germline polymorphisms in telomere maintenance genes affect telomere length and may contribute to CLL susceptibility.MethodsWe collected genome-wide data from two groups of patients with CLL (N = 273) and two control populations (N = 5,725). In ancestry-adjusted case-control comparisons, we analyzed eight SNPs in genes definitively associated with inter-individual variation in leukocyte telomere length (LTL) in prior genome-wide association studies: ACYP2, TERC, NAF1, TERT, OBFC1, CTC1, ZNF208, and RTEL1 RESULTS: Three of the eight LTL-associated SNPs were associated with CLL risk at P < 0.05, including those near: TERC [OR, 1.46; 95% confidence interval (CI), 1.15-1.86; P = 1.8 × 10(-3)], TERT (OR = 1.23; 95% CI, 1.02-1.48; P = 0.030), and OBFC1 (OR, 1.36; 95% CI, 1.08-1.71; P = 9.6 × 10(-3)). Using a weighted linear combination of the eight LTL-associated SNPs, we observed that CLL patients were predisposed to longer LTL than controls in both case-control sets (P = 9.4 × 10(-4) and 0.032, respectively). CLL risk increased monotonically with increasing quintiles of the weighted linear combination.ConclusionsGenetic variants in TERC, TERT, and OBFC1 are associated with both longer LTL and increased CLL risk. Because the human CST complex competes with shelterin for telomeric DNA, future work should explore the role of OBFC1 and other CST complex genes in leukemogenesis.ImpactA genetic predisposition to longer telomere length is associated with an increased risk of CLL, suggesting that the role of telomere length in CLL etiology may be distinct from its role in disease progression. Cancer Epidemiol Biomarkers Prev; 25(7); 1043-9. ©2016 AACR.

Aberrant telomere lengthening is an important feature of cancer cells in adults and children. In addition to somatic mutations, germline polymorphisms in telomere maintenance genes impact telomere length. Whether these telomere-associated polymorphisms affect risk of childhood malignancies remains largely unexplored. We collected genome-wide data from three groups with pediatric malignancies [neuroblastoma (N = 1516), acute lymphoblastic leukemia (ALL) (N = 958) and osteosarcoma (N = 660)] and three control populations (N = 6892). Using case-control comparisons, we analyzed eight single nucleotide polymorphisms (SNPs) in genes definitively associated with interindividual variation in leukocyte telomere length (LTL) in prior genome-wide association studies: ACYP2, TERC, NAF1, TERT, OBFC1, CTC1, ZNF208 and RTEL1 Six of these SNPs were associated (P < 0.05) with neuroblastoma risk, one with leukemia risk and one with osteosarcoma risk. The allele associated with longer LTL increased cancer risk for all these significantly associated SNPs. Using a weighted linear combination of the eight LTL-associated SNPs, we observed that neuroblastoma patients were predisposed to longer LTL than controls, with each standard deviation increase in genotypically estimated LTL associated with a 1.15-fold increased odds of neuroblastoma (95%CI = 1.09-1.22; P = 7.9×10(-7)). This effect was more pronounced in adolescent-onset neuroblastoma patients (OR = 1.46; 95%CI = 1.03-2.08). A one standard deviation increase in genotypically estimated LTL was more weakly associated with osteosarcoma risk (OR = 1.10; 95%CI = 1.01-1.19; P = 0.017) and leukemia risk (OR = 1.07; 95%CI = 1.00-1.14; P = 0.044), specifically for leukemia patients who relapsed (OR = 1.19; 95%CI = 1.01-1.40; P = 0.043). These results indicate that genetic predisposition to longer LTL is a newly identified risk factor for neuroblastoma and potentially for other cancers of childhood.

Glioma, the most common central nervous system cancer in adults, has poor prognosis. Here we identify a new SNP associated with glioma risk, rs1920116 (near TERC), that reached genome-wide significance (Pcombined = 8.3 × 10(-9)) in a meta-analysis of genome-wide association studies (GWAS) of high-grade glioma and replication data (1,644 cases and 7,736 controls). This region has previously been associated with mean leukocyte telomere length (LTL). We therefore examined the relationship between LTL and both this new risk locus and other previously established risk loci for glioma using data from a recent GWAS of LTL (n = 37,684 individuals). Alleles associated with glioma risk near TERC and TERT were strongly associated with longer LTL (P = 5.5 × 10(-20) and 4.4 × 10(-19), respectively). In contrast, risk-associated alleles near RTEL1 were inconsistently associated with LTL, suggesting the presence of distinct causal alleles. No other risk loci for glioma were associated with LTL. The identification of risk alleles for glioma near TERC and TERT that also associate with telomere length implicates telomerase in gliomagenesis.

BACKGROUND: The clonal evolution of tumor cell populations can be reconstructed from patterns of genetic alterations. In contrast, tumor epigenetic states are reversible and sensitive to the tumor microenvironment, presumably precluding the use of epigenetics to discover the clonal and sub-clonal evolution of tumors. We recently used mutation patterns to learn how low grade gliomas evolve over time, and also discovered that temozolomide treatment of LGG is associated with TMZ-induced hypermutation and malignant progression to GBM (BE Johnson et al, Science, 2014). METHODS: We used exome and RNA sequencing, DNA methylation arrays, along with computational analysis to construct phylogenetic and phyloepigenetic relationships among co-evolving tumor cell populations. RESULTS: Here we examined the spatial and temporal dynamics of DNA methylation in our clinically and genetically characterized cohort of IDH1-mutant low-grade gliomas and their patient-matched recurrences. While all tumors exhibited the hypermethylation signature associated with IDH1 mutation, low-grade gliomas that underwent spontaneous or temozolomide-associated malignant progression to high-grade glioblastoma multiforme (GBM) had a unique signature of DNA hypomethylation enriched for both active enhancers, and sites of age-related hypermethylation in the brain. Genes with promoter hypomethylation and concordant transcriptional upregulation during evolution to GBM were enriched in cell cycle function, evolving in concert with genetic alterations that deregulate the G1/S cell cycle checkpoint. Despite the plasticity of tumor epigenetic states, phyloepigenetic relationships robustly recapitulated phylogenetic patterns inferred from somatic mutations in the same patients. CONCLUSIONS: These findings highlight widespread co-dependency of genetic and epigenetic events throughout the clonal evolution of initial and recurrent gliomas.

BACKGROUND: Glioblastoma, the most common and aggressive form of glioma, has a median survival time of just 15 months. Both inherited and acquired genetic variation influence gliomagenesis. Previous genome-wide association studies (GWAS) have discovered seven glioma risk loci, including two in genes involved in telomere structure and function (TERT and RTEL1). METHODS: To identify novel high-grade glioma risk loci, we performed SNP imputation and meta-analysis of genome-wide array data from The University of California, San Francisco Adult Glioma Study (AGS), The Cancer Genome Atlas (TCGA) and the Wellcome Trust Case-Control Consortium (WTCCC) (1,013 cases and 6,595 controls). SNPs with P < 1.0x10-6 in the discovery meta-analysis underwent attempted replication in an additional 631 glioblastoma cases and 1141 controls from The Mayo Clinic and UCSF. To investigate potential functional mechanisms through which SNPs might promote gliomagenesis, we examined the relationship between mean leukocyte telomere length (LTL) and glioma risk loci using data from a recent GWAS of LTL (N = 37,684). RESULTS: One novel SNP association from the discovery phase meta-analysis met criteria for attempted replication. This SNP was significantly associated with high-grade glioma risk in the replication dataset (P = 3.4x10-3). The combined P-value for all 1644 cases and 7736 controls achieved genome-wide statistical significance (8.3x10-9). Glioma risk alleles in both our newly identified risk region and the known TERT risk locus were strongly associated with longer LTL (P < 5.0x10-8). In contrast, glioma risk alleles near RTEL1 were inconsistently associated with LTL and suggested the presence of distinct causal alleles underlying these two phenotypes. No other established glioma risk loci were associated with LTL. CONCLUSIONS: We identify a novel genome-wide significant association between a constitutive SNP and glioma risk. Because telomere maintenance is a universal requirement of oncogenic progression and telomere length displays substantial interindividual variability, telomere length is a promising epidemiologic risk factor for human cancers. We demonstrate that alleles in our novel locus and in TERT are associated with both longer mean LTL and with increased glioma risk. These results strongly implicate inherited variation near these two genes in facilitating gliomagenesis through a mechanism involving lengthened telomeres. SECONDARY CATEGORY: n/a.