Overview and clinical significance of multiple mutations in individual genes in hepatocellular carcinoma.

BACKGROUND: Multiple mutation (MM) within a single gene has recently been reported as a mechanism involved in carcinogenesis. The present study investigated the clinical significance of MMs in hepatocellular carcinoma (HCC). METHODS: Two hundred twenty-three surgically resected HCCs were subjected to gene expression profiling and whole-exome sequencing. RESULTS: MMs in individual genes were detected in 178 samples (MM tumors: 79.8%). The remaining samples all carried a single mutation (SM tumors: 20.2%). Recurrence-free survival in the MM group was significantly worse in comparison to the SM group (P = 0.012). A Cox proportional hazard analysis revealed that MM tumor was an independent predictor for worse a prognosis (hazard ratio, 1.72; 95% confidence interval, 1.01-3.17; P = 0.045). MMs were frequently observed across in various genes, especially MUC16 (15% of samples had at least one mutation in the gene) and CTNNB1 (14%). Although the MUC16 mRNA expression of MUC16 wild-type and MUC16 SM tumors did not differ to a statistically significant extent, the expression in MUC16 MM tumors was significantly enhanced in comparison to MUC16 SM tumors (P < 0.001). In MUC16, MMs were associated with viral hepatitis, higher tumor marker levels and vascular invasion. The MUC16 MMs group showed significantly worse recurrence-free survival in comparison to the MUC16 SM group (P = 0.022), while no significant difference was observed between the MUC16 SM group and the MUC16 wild-type group (P = 0.324). CONCLUSIONS: MM was a relatively common event that may occur selectively in specific oncogenes and is involved in aggressive malignant behavior.

Disclosure of secondary findings in exome sequencing of 2480 Japanese cancer patients.

High-throughput sequencing has greatly contributed to precision medicine. However, challenges remain in reporting secondary findings (SFs) of germline pathogenic variants and managing the affected patients. The aim of this study was to examine the incidence of SFs in Japanese cancer patients using whole exome sequencing (WES) and to understand patient preferences regarding SF disclosure. WES was conducted for 2480 cancer patients. Genomic data were screened and classified for variants of 59 genes listed by the American College of Medical Genetics and Genomics SF v2.0 and for an additional 13 hereditary cancer-related genes. Majority of the participants (68.9%; 1709/2480) opted for disclosure of their SFs. Thirty-two pathogenic or likely pathogenic variants, including BRCA1 (7 patients), BRCA2 (4), CHEK2 (4), PTEN (3), MLH1 (3), SDHB (2), MSH6 (1), NF1 (1), EXT2 (1), NF1 (1), NTRK1 (1), MYH7 (3), MYL2 (1), TNNT2 (1), LDLR (2), FBN1 (1), and KCNH2 (1) were recognized in 36 patients (1.5%). Twenty-eight (77.8%) patients underwent genetic counseling and received their SF results. Eighteen (64.3%) patients underwent clinical management for SFs. Genetic validation tests were administered significantly more frequently to patients with than without a SF-related personal history (P = 0.025). This was a first attempt at a large-scale systematic exome analysis in Japan; nevertheless, many cancer patients opted for disclosure of SFs and accepted or considered clinical management.

Mutational concordance analysis provides supportive information for double cancer diagnosis.

BACKGROUND: Mutation analysis using next-generation sequencing highlights the features of tumors with somatic alterations. However, the mutation profile of double cancer remains unclear. Here, we analyzed tumors derived from the same patient using whole exome sequencing (WES) to investigate the coherence of somatic mutations in double cancer. METHODS: First, the tumor mutational burden (TMB) was investigated using WES of 5521 tumor specimens from a Japanese pan-cancer cohort. The frequencies of mutation concordance were then compared in these cancers. Finally, we calculated the expected value of mutational concordance fitting a Poisson distribution to determine the relationship between double and metastatic cancers. RESULTS: In all, 44, 58, and 121 paired samples were diagnosed as double cancer, multifocal lesions (derived from identical tissues), and metastasis, respectively. Our analysis revealed that common somatic mutations were almost entirely absent in double cancer, whereas primary tumors and metastatic foci harbored several identical alterations. Concordance of the mutation profile in the same patient reflects the tumor origin and development, suggesting the potential for identifying double cancer based on common somatic mutations. Furthermore, according to a Poisson distribution, double cancer could be discriminated based on paired samples from the same patient. The probability of double cancer with more than 10 mutations was ≤1 part-per-billion (ppb, 10- 9). In multifocal lesions, 74% of tumor pairs accumulated ≤10 common mutations, implying a difference in tumor origin within identical tissues. CONCLUSIONS: These findings indicate that counting common somatic mutations can indicate the differences in origin between tumors derived from the same patient. Our mutation coherence analysis can thus provide beneficial information for diagnosing double cancer.

BMP4 and PHLDA1 are plausible drug-targetable candidate genes for KRAS G12A-, G12D-, and G12V-driven colorectal cancer.

Despite the frequent detection of KRAS driver mutations in patients with colorectal cancer (CRC), no effective treatments that target mutant KRAS proteins have been introduced into clinical practice. In this study, we identified potential effector molecules, based on differences in gene expression between CRC patients carrying wild-type KRAS (n = 390) and those carrying KRAS mutations in codon 12 (n = 240). CRC patients with wild-type KRAS harboring mutations in HRAS, NRAS, PIK3CA, PIK3CD, PIK3CG, RALGDS, BRAF, or ARAF were excluded from the analysis. At least 11 promising candidate molecules showed greater than two-fold change between the KRAS G12 mutant and wild-type and had a Benjamini-Hochberg-adjusted P value of less than 1E-08, evidence of significantly differential expression between these two groups. Among these 11 genes examined in cell lines transfected with KRAS G12 mutants, BMP4, PHLDA1, and GJB5 showed significantly higher expression level in KRAS G12A, G12D, and G12V transfected cells than in the wild-type transfected cells. We expect that this study will lead to the development of novel treatments that target signaling molecules functioning with KRAS G12-driven CRC.

Sharing genetic test results of germline pathogenic variants of hereditary cancer with relatives: A single-center cross-sectional study.

OBJECTIVE: This study aimed to determine whether Japanese cancer patients share test results of germline pathogenic variants of hereditary cancer with their relatives. METHODS: This single-center cross-sectional study enrolled 21 Japanese patients who received results of germline pathogenic variants of hereditary cancer at least 6 months prior. RESULTS: All patients shared their test results with at least one relative, with the following sharing rates: 85.7% for first-degree relatives, 10% for second-degree relatives and 8.3% for third-degree relatives. Patients most commonly shared the information with their children aged >18 years (86.7%), followed by their siblings (73.6%), spouses (64.7%) and parents (54.5%). Three categories were extracted from qualitative analysis: 'characteristics of my cancer', 'knowledge and caution about inheritability' and 'utilization of medical care.' CONCLUSIONS: The rate of test result sharing with first-degree relatives was comparable with those in Europe and the USA. Patients with germline pathogenic variants also tended to share their test results more with their children and siblings than with their parents. Informing their relatives of the results was suggestive of the motivation to influence their relatives' health outcome and contribute to the well-being of their children and siblings.

Characterization of tumors with ultralow tumor mutational burden in Japanese cancer patients.

Tumor mutational burden analysis using whole-exome sequencing highlights features of tumors with various mutations or known driver alterations. Cancers with few changes in the exon regions have unclear characteristics, even though low-mutated tumors are often detected in pan-cancer analysis. In the present study, we analyzed tumors with low tumor mutational burden listed in the Japanese version of The Cancer Genome Atlas, a data set of 5020 primary solid tumors. Our analysis revealed that detection rates of known driver mutations and copy number variation were decreased in samples with tumor mutational burden below 1.0 (ultralow tumor), compared with those in samples with low tumor mutational burden (≤5 mutations/Mb). This trend was also observed in The Cancer Genome Atlas data set. In the ultralow tumor mutational burden tumors, expression analysis showed decreased TP53 inactivation and chromosomal instability. TP53 inactivation frequently correlated with PI3K/mTOR-related gene expression, implying suppression of the PI3K/mTOR pathway in ultralow tumor mutational burden tumors. In common with mutational burden, the T cell-inflamed gene expression profiling signature was a potential marker for prediction of an immune checkpoint inhibitor response, and some ultralow tumor mutational burden tumor populations highly expressed this signature. Our analysis focused on how these tumors could provide insight into tumors with low somatic alteration that are difficult to detect solely using whole-exome sequencing.

Japanese version of The Cancer Genome Atlas, JCGA, established using fresh frozen tumors obtained from 5143 cancer patients.

This study aimed to establish the Japanese Cancer Genome Atlas (JCGA) using data from fresh frozen tumor tissues obtained from 5143 Japanese cancer patients, including those with colorectal cancer (31.6%), lung cancer (16.5%), gastric cancer (10.8%) and other cancers (41.1%). The results are part of a single-center study called "High-tech Omics-based Patient Evaluation" or "Project HOPE" conducted at the Shizuoka Cancer Center, Japan. All DNA samples and most RNA samples were analyzed using whole-exome sequencing, cancer gene panel sequencing, fusion gene panel sequencing and microarray gene expression profiling, and the results were annotated using an analysis pipeline termed "Shizuoka Multi-omics Analysis Protocol" developed in-house. Somatic driver alterations were identified in 72.2% of samples in 362 genes (average, 2.3 driver events per sample). Actionable information on drugs that is applicable in the current clinical setting was associated with 11.3% of samples. When including those drugs that are used for investigative purposes, actionable information was assigned to 55.0% of samples. Germline analysis revealed pathogenic mutations in hereditary cancer genes in 9.2% of samples, among which 12.2% were confirmed as pathogenic mutations by confirmatory test. Pathogenic mutations associated with non-cancerous hereditary diseases were detected in 0.4% of samples. Tumor mutation burden (TMB) analysis revealed 5.4% of samples as having the hypermutator phenotype (TMB ≥ 20). Clonal hematopoiesis was observed in 8.4% of samples. Thus, the JCGA dataset and the analytical procedures constitute a fundamental resource for genomic medicine for Japanese cancer patients.

Mutational burden and signatures in 4000 Japanese cancers provide insights into tumorigenesis and response to therapy.

Tumor mutational burden (TMB) and mutational signatures reflect the process of mutation accumulation in cancer. However, the significance of these emerging characteristics remains unclear. In the present study, we used whole-exome sequencing to analyze the TMB and mutational signature in solid tumors of 4046 Japanese patients. Eight predominant signatures-microsatellite instability, smoking, POLE, APOBEC, UV, mismatch repair, double-strand break repair, and Signature 16-were observed in tumors with TMB higher than 1.0 mutation/Mb, whereas POLE and UV signatures only showed moderate correlation with TMB, suggesting the extensive accumulation of mutations due to defective POLE and UV exposure. The contribution ratio of Signature 16, which is associated with hepatocellular carcinoma in drinkers, was increased in hypopharynx cancer. Tumors with predominant microsatellite instability signature were potential candidates for treatment with immune checkpoint inhibitors such as pembrolizumab and were found in 2.8% of cases. Furthermore, based on microarray analysis, tumors with predominant signatures were classified into 2 subgroups depending on the expression of immune-related genes reflecting differences in the immune context of the tumor microenvironment. Tumor subpopulations differing in the content of infiltrating immune cells might respond differently to immunotherapeutics. An understanding of cancer characteristics based on TMB and mutational signatures could provide new insights into mutation-driven tumorigenesis.

Driver gene alterations and activated signaling pathways toward malignant progression of gastrointestinal stromal tumors.

Mutually exclusive KIT and PDGFRA mutations are considered to be the earliest events in gastrointestinal stromal tumors (GIST), but insufficient for their malignant progression. Herein, we aimed to identify driver genes and signaling pathways relevant to GIST progression. We investigated genetic profiles of 707 driver genes, including mutations, gene fusions, copy number gain or loss, and gene expression for 65 clinical specimens of surgically dissected GIST, consisting of six metastatic tumors and 59 primary tumors from stomach, small intestine, rectum, and esophagus. Genetic alterations included oncogenic mutations and amplification-dependent expression enhancement for oncogenes (OG), and loss of heterozygosity (LOH) and expression reduction for tumor suppressor genes (TSG). We assigned activated OG and inactivated TSG to 27 signaling pathways, the activation of which was compared between malignant GIST (metastasis and high-risk GIST) and less malignant GIST (low- and very low-risk GIST). Integrative molecular profiling indicated that a greater incidence of genetic alterations of driver genes was detected in malignant GIST (96%, 22 of 23) than in less malignant GIST (73%, 24 of 33). Malignant GIST samples groups showed mutations, LOH, and aberrant expression dominantly in driver genes associated with signaling pathways of PI3K (PIK3CA, AKT1, and PTEN) and the cell cycle (RB1, CDK4, and CDKN1B). Additionally, we identified potential PI3K-related genes, the expression of which was upregulated (SNAI1 and TPX2) or downregulated (BANK1) in malignant GIST. Based on our observations, we propose that inhibition of PI3K pathway signals might potentially be an effective therapeutic strategy against malignant progression of GIST.

Metachronous ovarian endometrioid carcinomas in a patient with a PTEN variant: case report of incidentally detected Cowden syndrome.

BACKGROUND: Somatic PTEN mutation occurs in a proportion of ovarian endometrioid carcinomas. However, these cancers have seldom been reported in diseases associated with germline PTEN variants, such as Cowden syndrome (CS). CASE PRESENTATION: The present case was a 39-year-old woman with a left ovarian carcinoma who demonstrated a germline splice variant of PTEN (c.1026 + 1G > T) following genome-wide whole exome sequencing of her germline DNA. Histology of her resected tumor revealed endometrioid carcinoma of the same type as a right ovarian cancer resected eight years previously. These tumors showed null immunostaining for PTEN. She was genetically diagnosed with CS. Despite her clinical examinations had demonstrated several characteristic findings of CS, including mammary fibroma, esophageal and skin papilloma, colonic hamartoma, uterine myoma, and lipoma, the clinicians could not approach this diagnosis. CONCLUSION: Ovarian endometrioid carcinoma is generally thought to develop from endometrial tissue menstruated from the uterus and implanted on the ovary. To date, ovarian cancers have not been listed as CS-related cancers; however, ovarian endometrioid cancer can have a potential association with CS in endometriosis cases.

Comprehensive characterization of genes associated with the TP53 signal transduction pathway in various tumors.

The TP53 signal transduction pathway is an attractive target for cancer treatments. In this study, we conducted a comprehensive molecular evaluation of 907 patients with cancer in Japan to identify genomic alterations in the TP53 pathway. TP53 mutations were frequently detected in many cancers, except melanoma, thymic tumors, gastrointestinal stromal tumors, and renal cancers. The frequencies of non-synonymous single nucleotide variants (SNVs) in the TP53 family members TP63 and TP73 were relatively low, although genes with increased frequencies of SNVs were as follows: PTEN (11.7%) in breast cancer, CDKN2A (11.1 and 9.6%) in pancreas and head and neck cancers, and ATM (18.0 and 11.1%) in liver and esophageal cancers. MDM2 expression was decreased or increased in patients with mutant or wild-type TP53, respectively. CDKN1A expression was increased with mutant TP53 in head and neck cancers. Moreover, TP63 overexpression was characteristically observed in squamous cell carcinomas of the lung, esophagus, and head and neck region. Additionally, overexpression of TP63 and TP73 was frequently observed in thymomas. Our results reveal a spectrum of genomic alterations in the TP53 pathway that is characteristic of many tumor types, and these data may be useful in the trials of targeted therapies.

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.

Tumor cell enrichment by tissue suspension improves sensitivity to copy number variation in diffuse gastric cancer with low tumor content.

The detection of copy number variations (CNVs) and somatic mutations in cancer is important for the selection of specific drugs for patients with cancer. In cancers with sporadic tumor cells, low tumor content prevents the accurate detection of somatic alterations using targeted sequencing. To efficiently identify CNVs, we performed tumor cell enrichment using tissue suspensions of formalin-fixed paraffin-embedded (FFPE) tissue sections with low tumor cell content. Tumor-enriched and residual fractions were separated from FFPE tissue suspensions of intestinal and diffuse-type gastric cancers containing sporadic tumor cells, and targeted sequencing was performed on 225 cancer-related genes. Sequencing of a targeted panel of cancer-related genes using tumor-enriched fractions increased the number of detectable CNVs and the copy number of amplified genes. Furthermore, CNV analysis using the normal cell-enriched residual fraction as a reference for CNV scoring allowed targeted sequencing to detect CNV characteristics of diffuse-type gastric cancer with low tumor content. Our approach improves the CNV detection rate in targeted sequencing with tumor enrichment and the accuracy of CNV detection in archival samples without paired blood.

Prostate stem cell antigen, a presumable organ-dependent tumor suppressor gene, is down-regulated in gallbladder carcinogenesis.

Gallbladder cancer (GBC) is relatively rare but has a high mortality rate. One candidate molecule which might be involved in GBC development is prostate stem cell antigen (PSCA), a glycosylphosphatidylinositol-anchored cell surface antigen with a tissue-specific pattern of expression in the epithelium of several organs, such as the prostate, stomach, bladder, and gallbladder. It is up-regulated in a number of cancers including prostate, urinary bladder, and pancreatic cancers, while it is down-regulated in esophageal and gastric cancers, suggesting that PSCA has an oncogenic activity in the former but a tumor suppressor activity in the latter. However, the precise function of PSCA and the regulatory mechanism for its expression in normal and cancer cells are yet to be determined. In this study, immunohistochemical analyses with a specific antibody revealed that PSCA is down-regulated in non-neoplastic gallbladder lesions such as cholesterolosis, cholecystolithiasis, and cholecystitis (9/17; 53%), and also in adenocarcinoma (40/44; 91%), a common neoplasm in gallbladder. Analyses of the DNA methylation status in the GBC cell lines by bisulfite-Pyrosequencing and a reporter assay for the PSCA promoter activity suggested that the down-regulation is explained, at least partly, by DNA methylation. Moreover, colony formation assay revealed that PSCA has cell-proliferation inhibition activity in the GBC cell lines, which was also observed in vivo. These lines of in vivo and in vitro evidence suggest that PSCA is acting as a tumor suppressor in GBC development.

Genomic landscape of pancreatic cancer in the Japanese version of the Cancer Genome Atlas.

Background: Pancreatic cancer (PC) is one of the most aggressive cancers worldwide. Although many studies have investigated genomic alterations, the genomic landscape of Japanese PC patients has not been fully elucidated. Methods: We used whole-exome sequencing, cancer gene panel deep-sequencing, and microarray gene expression profiling data derived from the Japanese version of the Cancer Genome Atlas (JCGA) in 93 PC cases. Results: Somatic driver mutations were identified in 65.6% of samples in 19 genes. The median tumor mutation burden (TMB) value was 0.24 Muts/Mb (interquartile range, 0.15-0.64 Muts/Mb). The commonly mutated genes were KRAS (58%), TP53 (40%), CDKN2A (10%), SMAD4 (10%), FGFR2 (9%), and PKHD1 (9%). Frequent germline variation genes were BRCA1 (8%), CDH1 (5%), MET (5%), MSH6 (5%), and TEK (5%). Frequent chromosomal arm alterations included copy number gains in 2q (42%), 7q (24%), and 3q (24%), and copy number losses in 19p (62%), 19q (47%), 12q (34%), and 7q (30%). A prognostic analysis according to the presence of driver mutations showed that overall survival (OS) in the driver mutation-positive group was significantly worse in comparison to that of the driver mutation-negative group (median, 23.1 vs 46.7 mo; P = .010). A Cox proportional hazards analysis for OS identified driver mutation (hazard ratio [HR], 1.89; P = .025) and lymph node metastasis (HR, 3.27; P = .002) as independent prognostic factors. Conclusion: The present results from the JCGA dataset constitute a fundamental resource for genomic medicine for PC patients, especially in Japan.

A Cross-sectional Study of Regret in Cancer Patients After Sharing Test Results for Pathogenic Germline Variants of Hereditary Cancers With Relatives.

BACKGROUND: Research on whole genome/exome sequencing is increasing worldwide. However, challenges are emerging in relation to receiving germline pathogenic variant results and sharing them with relatives. OBJECTIVE: The aim of this study was to investigate the occurrence of and reasoning related to regret among patients with cancer who shared single-gene testing results and whole exome sequencing with family members. METHODS: This was a single-center, cross-sectional study. The Decision Regret Scale was administered, and descriptive questionnaires were used with 21 patients with cancer. RESULTS: Eight patients were classified as having no regret, 9 patients were classified as having mild regret, and 4 patients were classified as having moderate to strong regret. Reasons patients felt that sharing was the right decision included the following: to allow relatives and children to take preventive measures, the need for both parties to be aware of and ready for the hereditary transmission of cancer, and the need to be able to discuss the situation with others. On the other hand, some patients did not think it was a good decision to share the information because of the associated anxiety. CONCLUSIONS: Regret over sharing test results for pathogenic germline variants of hereditary cancers with relatives tended to be low. The main reason was that patients believed that they were able to benefit others by sharing. IMPLICATIONS FOR PRACTICE: Healthcare professionals need to understand the postsharing perceptions and experiences of patients and support them throughout the sharing process.

Comparative analysis of tumor content estimation methods based on simu- lated tumor samples identified their impact on somatic variant detection in cancer whole genome sequencing.

Whole genome sequencing (WGS) in cancer genomics has become widespread with recent technological innovations, and the amount and types of information obtained from WGS are increasing rapidly. Appropriate interpretation of results is becoming increasingly important in clinical applications. This study aimed to evaluate the accuracy of tumor content estimation and its impact on somatic variant detection, using 100 simulated tumor samples covering 10-100% tumor content constructed from the sequencing data of cell line models. Extensive analysis revealed that the estimation results varied among computational analytical methods. Notably, there was a large discrepancy in low tumor content (≤ 30%). The reproducibility decreased in cases wherein chromosome-scale copy number changes were observed in normal cells. The minimum tumor content required to detect somatic alterations was estimated to be 10-30%. Identification of whole genome doubling was achieved with the lowest tumor content, followed by single nucleotide variation/insertion or deletion, structural variation, and copy number variation. Tumor content had a significantly higher impact on the false negatives than the false positives in variant calls. Results should be interpreted cautiously for samples wherein tumor content is a concern. These results can form the basis of developing important guidelines for evaluating cancer WGS.

Impact of somatic mutations and transcriptomic alterations on cancer aneuploidy.

Aneuploidy has been recognized as one of hallmark of tumorigenesis since the early 20th century. Recent developments in structural variation analysis in the human genome have revealed the diversity of aneuploidy in cancer. However, the effects of gene mutation and expression in tumors on aneuploidy remain poorly understood. Here, we performed whole exome analysis of over 5,000 Japanese cancer cases and investigated the impact of somatic mutations and gene expression alterations on aneuploidy. First, we evaluated tumor content and genomic alterations that could influence aneuploidy. Next, we compared the aneuploidy frequency in 18 cancer types and observed that TP53 mutations were associated with the aneuploidy on specific chromosomes in colorectal and gastric cancers. Finally, we used expression analysis to isolate pathways involved in aneuploidy accumulation from tumors without TP53 mutations. Chromosomal instability and cell cycle aberration were associated with aneuploidy in TP53 wild-type tumors, and 26 commonly upregulated genes were identified in aneuploidy-high solid tumors without TP53 mutations. Among them, two cancer-related genes (CENPA and PBK) were involved in aneuploidy. Our integrated analysis revealed that both TP53 mutations and transcriptomic alterations independent of somatic mutations affect aneuploidy accumulation. Our findings will facilitate further understanding of diverse aneuploidies in the tumorigenesis.

Whole-genome and Epigenomic Landscapes of Malignant Gastrointestinal Stromal Tumors Harboring KIT Exon 11 557-558 Deletion Mutations.

Gastrointestinal stromal tumors (GIST) with KIT exon 11 deletions involving in codons 557-558 (KIT Δ557-558) exhibit higher proliferation rates and shorter disease-free survival times compared with GISTs with other KIT exon 11 mutations. We analyzed 30 GIST cases and observed genomic instability and global DNA hypomethylation only in high-risk malignant GISTs with KIT Δ557-558. Whole-genome sequencing revealed that the high-risk malignant GISTs with KIT Δ557-558 (12 cases) had more structural variations (SV), single-nucleotide variants, and insertions and deletions compared with the low-risk, less malignant GISTs with KIT Δ557-558 (six cases) and the high-risk (six cases) or low-risk (6 cases) GISTs with other KIT exon 11 mutations. The malignant GISTs with KIT Δ557-558 showed higher frequency and significance in copy number (CN) reduction on chromosome arms 9p and 22q, and 50% of them had LOH or CN-dependent expression reduction in CDKN2A. In addition, SVs with driver potential were detected in 75% of them, in which AKT3 and MGMT were recurrently identified. Genome-wide DNA methylation and gene expression analyses showed global intergenic DNA hypomethylation, SNAI2 upregulation, and higher expression signatures, including p53 inactivation and chromosomal instability, as characteristics of malignant GISTs with KIT Δ557-558 that distinguished them from other GISTs. These genomic and epigenomic profiling results revealed that KIT Δ557-558 mutations are associated with increased genomic instability in malignant GISTs. Significance: We present genomic and epigenomic insights into the malignant progression of GISTs with KIT exon 11 deletions involving in 557-558, demonstrating their unique chromosomal instability and global intergenic DNA hypomethylation.

Molecular genetic positioning of small intestine and papilla of Vater carcinomas including clinicopathological classification.

BACKGROUND: Small intestine carcinoma (SIC) cases in Japan have recently been treated with chemotherapy according to colorectal carcinoma classification, while papilla of Vater carcinoma (PVC) cases according to cholangiocarcinoma (CHC) classification. However, few research reports support the molecular genetic validity of these therapeutic choices. PATIENTS AND METHODS: Here, we investigated the clinicopathological and molecular genetic factors of SIC and PVC. We used the data from the Japanese version of The Cancer Genome Atlas. Additionally, molecular genetic data on gastric adenocarcinoma (GAD), colorectal adenocarcinoma (CRAD), pancreatic ductal adenocarcinoma (PDAC), and CHC were also referred to. RESULTS: This study consisted of tumor samples from 12 patients of SIC and three patients of PVC treated from January 2014 to March 2019. Among them, six patients had pancreatic invasion. t-Distributed stochastic neighbor embedding analysis showed that the gene expression pattern of SIC was similar not only to those of GAD and CRAD, but also to that of PDAC in the pancreatic invasion patients. In addition, PVC resembled the GAD, CRAD, and PDAC, rather than the CHC. The molecular genetic characteristics of the six patients with pancreatic invasion were: one had high microsatellite instability, two had a TP53 driver mutation, and three had tumor mutation burden values <1 mutation/Mb with no driver mutation. CONCLUSIONS: In this study, the extensive gene expression profiling of organ carcinomas newly suggests that SIC or PVC may resemble GAD, CRAD, and PDAC. In addition, the data demonstrate that pancreatic invasive patients may be classified into several subtypes using molecular genetic factors.