Cooperative participation of epigenomic and genomic alterations in the clinicopathological diversity of gastric adenocarcinomas: significance of cell adhesion and epithelial-mesenchymal transition-related signaling pathways.

The present study was conducted to clarify the cooperative significance of epigenomic and genomic abnormalities during gastric carcinogenesis. Using 21 samples of normal control gastric mucosa (C), 109 samples of non-cancerous gastric mucosa (N) and 105 samples of cancerous tissue (T) from 109 patients with primary gastric adenocarcinomas, genome-wide DNA methylation analysis was performed using Infinium assay. Among these samples, 66 paired N and corresponding T samples were subjected to whole-exome and single nucleotide polymorphism array analyses. As had been shown in our previous study, 109 patients were clustered clinicopathologically into least aggressive Cluster A (n = 20), most aggressive Cluster B1 (n = 20) and Cluster B2 (n = 69). Most DNA methylation alterations in each cluster had already occurred even in N samples compared with C samples, and DNA methylation alterations at the precancerous N stage were inherited by the established cancers themselves. Recurrent single nucleotide variants and insertions/deletions resulting in functional disruption of the proteins encoded by the ABCA10, BNC2, CDH1, CTNNB1, SMAD4 and VAV2 genes were specific to Cluster B1, whereas those of the APC, EGFR, ERBB2, ERBB3, MLH1 and MUC6 genes were specific to Cluster A. MetaCore pathway analysis revealed that the epigenomically affected TWIST1 gene and genomically affected CDH1, CTNNB1, MMP9, TLN2, ROCK1 and SMAD4 genes were accumulated in signaling pathways related to cell adhesion, cytoskeleton remodeling and epithelial-mesenchymal transition in Cluster B1. These data indicate that epigenomic alterations at the precancerous stage are important in gastric carcinogenesis and that epigenomic and genomic alterations cooperatively underlie the aggressiveness of gastric adenocarcinomas.

Simple prediction model for homologous recombination deficiency in breast cancers in adolescents and young adults.

PURPOSE: Homologous recombination deficiency (HRD), which influences the efficacy of PARP inhibitor- and platinum agent-based therapies, is a prevalent phenotype of breast cancer in adolescents and young adults (AYAs; 15-39 years old). However, HRD score, indicating HRD status, is not routinely assessed in the breast oncology clinic, particularly in patients without germline BRCA1/2 mutations. Hence, we sought to develop a model for determining HRD status based on genetic and clinicopathological factors. METHODS: Subjects were our own cohort of 46 Japanese AYA breast cancer patients and two existing breast cancer cohorts of US and European patients. Models for prediction of the HRD-high phenotype, defined as HRD score ≥ 42, were constructed by logistic regression analysis, using as explanatory variables genetic and clinicopathological factors assessable in the clinical setting. RESULTS: In all three cohorts, the HRD-high phenotype was associated with germline BRCA1/2 mutation, somatic TP53 mutation, triple-negative subtype, and higher tumor grade. A model based on these four factors, developed using the US cohort, was validated in the Japanese and European AYA cases: area under the receiver operating characteristic curve [AUC] was 0.90 and 0.96, respectively. A model based on three factors excluding germline BRCA1/2 mutation also yielded high-predictive power in cases from these two cohorts without germline BRCA1/2 mutations: AUC was 0.92 and 0.90, respectively. CONCLUSIONS: The HRD-high phenotype of AYA breast cancer patients can be deduced from genomic and pathological factors that are routinely examined in the oncology clinic, irrespective of germline BRCA1/2 mutations.

Gene aberration profile of tumors of adolescent and young adult females.

There has been little improvement in the prognosis for adolescent and young adult (AYA) tumor patients. Hence, there is an urgent need to understand the etiology of tumor development and identify actionable gene aberrations to improve prevention and therapy. Here, 76 sporadic tumors (48 breast, 22 ovarian, and six uterine) from 76 AYA females (age range, 25-39 years) were subjected to whole exome and RNA sequencing to determine their mutational signatures and actionable gene profiles. Two individuals with breast cancer (4.2% of cases) and one with ovarian cancer (5.3% of cases) carried germline BRCA2 mutations. The two cases with breast tumors also each carried an additional deleterious germline mutation: one in TP53 and the other in CHEK2. Mutational signature analysis of the 76 tumors indicated that spontaneous deamination of 5-methylcytosine and activity of the APOBEC cytidine deaminase protein family are major causes of mutagenesis. In addition, 18 breast or ovarian tumors (18/70, 26%), including the three cases with germline BRCA2 mutations, exhibited a predominant "BRCAness" mutational signature, an indicator of functional BRCA1/BRCA2 deficiency. Actionable aberrations and high tumor mutation burdens were detected in 24 breast (50%), 17 ovarian (77%), and five uterine (83%) tumor cases. Thus, mutational processes and aberrant genes in AYA tumors are largely shared with those identified in non-AYA tumors. The efficacy of molecular targeting and immune checkpoint inhibitory therapies should be explored for both AYA and non-AYA patients.

Deleterious Pulmonary Surfactant System Gene Mutations in Lung Adenocarcinomas Associated With Usual Interstitial Pneumonia.

PURPOSE: Usual interstitial pneumonia (UIP) is a risk factor for lung carcinogenesis. This study was performed to characterize mutagenesis and mutational target genes underlying lung carcinogenesis in patients with UIP. PATIENTS AND METHODS: A cohort of 691 Japanese patients with lung adenocarcinoma (LADC), of whom 54 had UIP and 637 did not, was studied for driver oncogene aberrations. Whole-exome analysis was performed for 296 cases, including 51 with UIP, to deduce mutagenic processes and identify commonly affected genes. Logistic regression analysis was used to detect associations of gene aberrations with clinicopathological factors. RESULTS: The EGFR mutation was markedly less prevalent in patients with LADC with UIP than in those without (1.9% [one of 54] v. 49.9% [318 of 637]; P < .001), even in heavy smokers (25.3% [38 of 150] of patients with > 40 pack-years; P < .001). Mutational signature analysis indicated that UIP-positive LADCs develop through accumulation of single-nucleotide and indel mutations caused by smoking. Pulmonary surfactant system genes (PSSGs) NKX2-1/TTF1, SFTPA1, SFTPA2, SFTPB, and SFTPC were identified as targets for mutations (preferentially indels), and mutations were specifically associated with shorter overall survival of patients with UIP-positive LADC, independent of pathologic stage (hazard ratio, 4.9; 95% CI, 1.7 to 14.4; P = .0037). CONCLUSION: LADCs with UIP develop through mutational events caused by smoking, independently of EGFR mutation. PSSGs were identified as a mutational target and as a novel prognostic factor in UIP-positive LADC. PSSG deficiency might increase the malignancy of tumor cells by increasing the tumor-promoting effects of UIP.

Alterations of the spindle checkpoint pathway in clinicopathologically aggressive CpG island methylator phenotype clear cell renal cell carcinomas.

CpG-island methylator phenotype (CIMP)-positive clear cell renal cell carcinomas (RCCs) are characterized by accumulation of DNA hypermethylation of CpG islands, clinicopathological aggressiveness and poor patient outcome. The aim of this study was to clarify the molecular pathways participating in CIMP-positive renal carcinogenesis. Genome (whole-exome and copy number), transcriptome and proteome (two-dimensional image converted analysis of liquid chromatography-mass spectrometry) analyses were performed using tissue specimens of 87 CIMP-negative and 14 CIMP-positive clear cell RCCs and corresponding specimens of non-cancerous renal cortex. Genes encoding microtubule-associated proteins, such as DNAH2, DNAH5, DNAH10, RP1 and HAUS8, showed a 10% or higher incidence of genetic aberrations (non-synonymous single-nucleotide mutations and insertions/deletions) in CIMP-positive RCCs, whereas CIMP-negative RCCs lacked distinct genetic characteristics. MetaCore pathway analysis of CIMP-positive RCCs revealed that alterations of mRNA or protein expression were significantly accumulated in six pathways, all participating in the spindle checkpoint, including the "The metaphase checkpoint (p = 1.427 × 10(-6))," "Role of Anaphase Promoting Complex in cell cycle regulation (p = 7.444 × 10(-6))" and "Spindle assembly and chromosome separation (p = 9.260 × 10(-6))" pathways. Quantitative RT-PCR analysis revealed that mRNA expression levels for genes included in such pathways, i.e., AURKA, AURKB, BIRC5, BUB1, CDC20, NEK2 and SPC25, were significantly higher in CIMP-positive than in CIMP-negative RCCs. All CIMP-positive RCCs showed overexpression of Aurora kinases, AURKA and AURKB, and this overexpression was mainly attributable to increased copy number. These data suggest that abnormalities of the spindle checkpoint pathway participate in CIMP-positive renal carcinogenesis, and that AURKA and AURKB may be potential therapeutic targets in more aggressive CIMP-positive RCCs.

Expression and clinical significance of genes frequently mutated in small cell lung cancers defined by whole exome/RNA sequencing.

Small cell lung cancer (SCLC) is the most aggressive type of lung cancer. Only 15% of SCLC patients survive beyond 2 years after diagnosis. Therefore, for the improvement of patients' outcome in this disease, it is necessary to identify genetic alterations applicable as therapeutic targets in SCLC cells. The purpose of this study is the identification of genes frequently mutated and expressed in SCLCs that will be targetable for therapy of SCLC patients. Exome sequencing was performed in 28 primary tumors and 16 metastatic tumors from 38 patients with SCLCs. Expression of mutant alleles was verified in 19 cases by RNA sequencing. TP53, RB1 and PTEN were identified as being significantly mutated genes. Additional 36 genes were identified as being frequently (≥10%) mutated in SCLCs by combining the results of this study and two recent studies. Mutated alleles were expressed in 8 of the 36 genes, TMEM132D, SPTA1, VPS13B, CSMD2, ANK2, ASTN1, ASPM and FBN3. In particular, the TMEM132D, SPTA1 and VPS13B genes were commonly mutated in both early and late stage tumors, primary tumors and metastases, and tumors before and after chemotherapy, as in the case of the TP53 and RB1 genes. Therefore, in addition to TP53, RB1 and PTEN, TMEM132D, SPTA1 and VPS13B could be also involved in SCLC development, with the products from their mutated alleles being potential therapeutic targets in SCLC patients.

Development of lung adenocarcinomas with exclusive dependence on oncogene fusions.

This report delivers a comprehensive genetic alteration profile of lung adenocarcinomas (LADC) driven by ALK, RET, and ROS1 oncogene fusions. These tumors are difficult to study because of their rarity. Each drives only a low percentage of LADCs. Whole-exome sequencing and copy-number variation analyses were performed on a Japanese LADC cohort (n = 200) enriched in patients with fusions (n = 31, 15.5%), followed by deep resequencing for validation. The driver fusion cases showed a distinct profile with smaller numbers of nonsynonymous mutations in cancer-related genes or truncating mutations in SWI/SNF chromatin remodeling complex genes than in other LADCs (P < 0.0001). This lower mutation rate was independent of age, gender, smoking status, pathologic stage, and tumor differentiation (P < 0.0001) and was validated in nine fusion-positive cases from a U.S. LADCs cohort (n = 230). In conclusion, our findings indicate that LADCs with ALK, RET, and ROS1 fusions develop exclusively via their dependence on these oncogene fusions. The presence of such few alterations beyond the fusions supports the use of monotherapy with tyrosine kinase inhibitors targeting the fusion products in fusion-positive LADCs.

Multilayer-omics analysis of renal cell carcinoma, including the whole exome, methylome and transcriptome.

The aim of this study was to identify pathways that have a significant impact during renal carcinogenesis. Sixty-seven paired samples of both noncancerous renal cortex tissue and cancerous tissue from patients with clear cell renal cell carcinomas (RCCs) were subjected to whole-exome, methylome and transcriptome analyses using Agilent SureSelect All Exon capture followed by sequencing on an Illumina HiSeq 2000 platform, Illumina Infinium HumanMethylation27 BeadArray and Agilent SurePrint Human Gene Expression microarray, respectively. Sanger sequencing and quantitative reverse transcription-PCR were performed for technical verification. MetaCore software was used for pathway analysis. Somatic nonsynonymous single-nucleotide mutations, insertions/deletions and intragenic breaks of 2,153, 359 and 8 genes were detected, respectively. Mutations of GCN1L1, MED12 and CCNC, which are members of CDK8 mediator complex directly regulating ß-catenin-driven transcription, were identified in 16% of the RCCs. Mutations of MACF1, which functions in the Wnt/ß-catenin signaling pathway, were identified in 4% of the RCCs. A combination of methylome and transcriptome analyses further highlighted the significant role of the Wnt/ß-catenin signaling pathway in renal carcinogenesis. Genetic aberrations and reduced expression of ERC2 and ABCA13 were frequent in RCCs, and MTOR mutations were identified as one of the major disrupters of cell signaling during renal carcinogenesis. Our results confirm that multilayer-omics analysis can be a powerful tool for revealing pathways that play a significant role in carcinogenesis.

High-resolution characterization of a hepatocellular carcinoma genome.

Hepatocellular carcinoma, one of the most common virus-associated cancers, is the third most frequent cause of cancer-related death worldwide. By massively parallel sequencing of a primary hepatitis C virus-positive hepatocellular carcinoma (36× coverage) and matched lymphocytes (>28× coverage) from the same individual, we identified more than 11,000 somatic substitutions of the tumor genome that showed predominance of T>C/A>G transition and a decrease of the T>C substitution on the transcribed strand, suggesting preferential DNA repair. Gene annotation enrichment analysis of 63 validated non-synonymous substitutions revealed enrichment of phosphoproteins. We further validated 22 chromosomal rearrangements, generating four fusion transcripts that had altered transcriptional regulation (BCORL1-ELF4) or promoter activity. Whole-exome sequencing at a higher sequence depth (>76× coverage) revealed a TSC1 nonsense substitution in a subpopulation of the tumor cells. This first high-resolution characterization of a virus-associated cancer genome identified previously uncharacterized mutation patterns, intra-chromosomal rearrangements and fusion genes, as well as genetic heterogeneity within the tumor.

A functional single nucleotide polymorphism in mucin 1, at chromosome 1q22, determines susceptibility to diffuse-type gastric cancer.

BACKGROUND & AIMS: Two major types of gastric cancer, intestinal and diffuse, develop through distinct mechanisms; the diffuse type is considered to be more influenced by genetic factors, although the mechanism is unknown. Our previous genome-wide association study associated 3 single nucleotide polymorphisms (SNPs) with diffuse-type gastric cancer (DGC); 1 was a functional SNP (rs2294008) in prostate stem cell antigen (PSCA), but the loci of the other 2 were not investigated. METHODS: We performed high-density mapping to explore a linkage disequilibrium status of the 2 SNPs at chromosome 1q22. A DGC case-control study was conducted using DNA from 606 cases and 1264 controls (all Japanese individuals) and validated using DNA from Japanese (304 cases, 1465 controls) and Korean (452 cases, 372 controls) individuals. The effects of SNPs on function were analyzed by reporter assays and analyses of splice variants. RESULTS: A region of a strong linkage disequilibrium with the 2 SNPs contained mucin 1 (MUC1) and other 4 genes and SNPs significantly associated with DGC (rs2070803: P = 4.33 × 10(-13); odds ratio [OR], 1.71 by meta-analysis of the studies on the 3 panels) but not with intestinal-type gastric cancer. Functional studies demonstrated that rs4072037 (P = 1.43 × 10(-11); OR, 1.66 by meta-analysis) in MUC1 affects promoter activity and determines the major splicing variants of MUC1 in the gastric epithelium. Individuals that carry both SNPs rs2294008 in PSCA and rs4072037 in MUC1 have a high risk for developing DGC (OR, 8.38). CONCLUSIONS: MUC1 is the second major DGC susceptibility gene identified. The SNPs rs2070803 and rs4072037 in MUC1 might be used to identify individuals at risk for this type of gastric cancer.

Genome-wide association study of pancreatic cancer in Japanese population.

Pancreatic cancer shows very poor prognosis and is the fifth leading cause of cancer death in Japan. Previous studies indicated some genetic factors contributing to the development and progression of pancreatic cancer; however, there are limited reports for common genetic variants to be associated with this disease, especially in the Asian population. We have conducted a genome-wide association study (GWAS) using 991 invasive pancreatic ductal adenocarcinoma cases and 5,209 controls, and identified three loci showing significant association (P-value<5x10(-7)) with susceptibility to pancreatic cancer. The SNPs that showed significant association carried estimated odds ratios of 1.29, 1.32, and 3.73 with 95% confidence intervals of 1.17-1.43, 1.19-1.47, and 2.24-6.21; P-value of 3.30x10(-7), 3.30x10(-7), and 4.41x10(-7); located on chromosomes 6p25.3, 12p11.21 and 7q36.2, respectively. These associated SNPs are located within linkage disequilibrium blocks containing genes that have been implicated some roles in the oncogenesis of pancreatic cancer.

Genetic variation in PSCA is associated with susceptibility to diffuse-type gastric cancer.

Gastric cancer is classified into intestinal and diffuse types, the latter including a highly malignant form, linitis plastica. A two-stage genome-wide association study (stage 1: 85,576 SNPs on 188 cases and 752 references; stage 2: 2,753 SNPs on 749 cases and 750 controls) in Japan identified a significant association between an intronic SNP (rs2976392) in PSCA (prostate stem cell antigen) and diffuse-type gastric cancer (allele-specific odds ratio (OR) = 1.62, 95% CI = 1.38-1.89, P = 1.11 x 10(-9)). The association was far less significant in intestinal-type gastric cancer. We found that PSCA is expressed in differentiating gastric epithelial cells, has a cell-proliferation inhibition activity in vitro and is frequently silenced in gastric cancer. Substitution of the C allele with the risk allele T at a SNP in the first exon (rs2294008, which has r(2) = 0.995, D' = 0.999 with rs2976392) reduces transcriptional activity of an upstream fragment of the gene. The same risk allele was also significantly associated with diffuse-type gastric cancer in 457 cases and 390 controls in Korea (allele-specific OR = 1.90, 95% CI = 1.56-2.33, P = 8.01 x 10(-11)). The polymorphism of the PSCA gene, which is possibly involved in regulating gastric epithelial-cell proliferation, influences susceptibility to diffuse-type gastric cancer.