Genetic Gastric Cancer Susceptibility in the International Clinical Cancer Genomics Community Research Network

Upper Gastrointestinal Cancers and the Role of Genetic Testing

Beyond the few established hereditary cancer syndromes with an upper gastrointestinal cancer component, there is increasing recognition of the contribution of novel pathogenic germline variants (gPVs) to upper gastrointestinal carcinogenesis. The detection of gPVs has potential implications for novel treatment approaches of the index cancer patient as well as long-term implications for surveillance and risk-reducing measures for cancer survivors and far-reaching implications for the patients' family. With widespread availability of multigene panel testing, new associations may be identified with germline-somatic integration being critical to determining true causality of novel gPVs. Comprehensive cancer care should incorporate both somatic and germline testing.

Prevalence and spectrum of cancer predisposition germline mutations in young patients with the common late-onset cancers

BACKGROUND

Pathogenic germline variants (PGVs) can play a vital role in the oncogenesis process in carriers. Previous studies have recognized that PGVs contribute to early onset of tumorigenesis in certain cancer types, for example, colorectal cancer and breast cancer. However, the reported prevalence data of cancer-associated PGVs were highly inconsistent due to nonuniform patient cohorts, sequencing methods, and prominent difficulties in pathogenicity interpretation of variants. In addition to the above difficulties, due to the rarity of cases, the prevalence of cancer PGV carriers in young cancer patients affected by late-onset cancer types has not been comprehensively evaluated to date.

METHODS

A total of 131 young cancer patients (1-29 years old at diagnosis) were enrolled in this study. The patients were affected by six common late-onset cancer types, namely, lung cancer, liver cancer, colorectal cancer, gastric cancer, renal cancer, and head-neck cancer. Cancer PGVs were identified and analyzed. based on NGS-based targeted sequencing followed by bioinformatic screening and strict further evaluations of variant pathogenicity.

RESULTS

Twenty-three cancer PGVs in 21 patients were identified, resulting in an overall PGV prevalence of 16.0% across the six included cancer types, which was approximately double the prevalence reported in a previous pancancer study. Nine of the 23 PGVs are novel, thus expanding the cancer PGV spectrum. Seven of the 23 (30.4%) PGVs are potential therapeutic targets of olaparib, with potential implications for clinical manipulation. Additionally, a small prevalence of somatic mutations of some classic cancer hallmark genes in young patients, in contrast to all-age patients, was revealed.

CONCLUSION

This study demonstrates the high prevalence of PGVs in young cancer patients with the common late-onset cancers and the potentially significant clinical implications of cancer PGVs, the findings highlight the value of PGV screening in young patients across lung cancer, liver cancer, colorectal cancer, gastric cancer, renal cancer, or head-neck cancer.

Frequency of CDH1, CTNNA1 and CTNND1 Germline Variants in Families with Diffuse and Mixed Gastric Cancer

The most well-characterized hereditary form of gastric cancer is hereditary diffuse gastric cancer (HDGC), an autosomal dominant syndrome characterized by an increased risk of diffuse gastric and lobular breast cancer. HDGC is predominantly caused by germline pathogenic variants in the CDH1 gene, and more rarely in the CTNNA1 gene. Furthermore, the International Gastric Cancer Linkage Consortium (IGCLC) guidelines do not clarify whether or not mixed gastric cancer (with a diffuse component) should be considered in the HDGC genetic testing criteria. We aimed to evaluate the contribution of CTNNA1 and CTNND1 germline variants to HDGC. Additionally, we also intended to compare the frequencies of CDH1 and CTNNA1 (and eventually CTNND1) germline variants between patients with diffuse and mixed gastric carcinomas to evaluate if genetic testing for these genes should or should not be considered in patients with the latter. We analyzed the CDH1 gene in 67 cases affected with early-onset/familial mixed gastric carcinomas and the CTNNA1 and CTNND1 genes in 208 cases with diffuse or mixed gastric cancer who had tested negative for CDH1 pathogenic germline variants. A deleterious CTNNA1 germline variant was found in 0.7% (1/141) of diffuse gastric cancer patients meeting the 2020 IGCLC criteria, as compared to the rate of 2.8% of CDH1 deleterious variants found by us in this setting. No deleterious variants were found in CTNND1, but six variants of uncertain significance were identified in this gene. We did not find any pathogenic CDH1, CTNNA1 or CTNND1 variant in index patients with early-onset/familial mixed gastric cancer, so there is no evidence that supports including this tumor type in the testing criteria for germline variants in these genes. The role of the CTNND1 gene in inherited gastric cancer predisposition is still unclear.

Cancer stem cell-mediated drug resistance: A comprehensive gene expression profile analysis in breast cancer

Breast cancer is the most frequently diagnosed malignancy in women and a major public health concern. In the current report, differential expression of the breast cancer resistance promoting genes with a focus on breast cancer stem cell related elements as well as the correlation of their mRNAs with various clinicopathologic characteristics, including molecular subtypes, tumor grade/stage, and methylation status, have been investigated using METABRIC and TCGA datasets. To achieve this goal, we downloaded gene expression data of breast cancer patients from TCGA and METABRIC. Then, statistical analyses were used to assess the correlation between the expression levels of stem cell related drug resistant genes and methylation status, tumor grades, various molecular subtypes, and some cancer hallmark gene sets such as immune evasion, metastasis, and angiogenesis. According to the results of this study, a number of stem cell related drug resistant genes are deregulated in breast cancer patients. Furthermore, we observe negative correlations between methylation of resistance genes and mRNA expression. There is a significant difference in the expression of resistance-promoting genes between different molecular subtypes. As mRNA expression and DNA methylation are clearly related, DNA methylation might be a mechanism that regulates these genes in breast cancer cells. As indicated by the differential expression of resistance-promoting genes among various breast cancer molecular subtypes, these genes may function differently in different subtypes of breast cancer. In conclusion, significant deregulation of resistance-promoting factors indicates that these genes may play a significant role in the development of breast cancer.

Immunotherapy for Peritoneal Carcinomatosis: Challenges and Prospective Outcomes

Peritoneal metastasis, also known as peritoneal carcinomatosis (PC), is a refractory cancer that is typically resistant to conventional therapies. The typical treatment for PC is a combination of cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). Recently, research in this area has seen significant advances, particularly in immunotherapy as an alternative therapy for PC, which is very encouraging. Catumaxomab is a trifunctional antibody intraperitoneal (IP) immunotherapy authorized in Europe that can be used to diminish malignant ascites by targeting EpCAM. Intraperitoneal (IP) immunotherapy breaks immunological tolerance to treat peritoneal illness. Increasing T-cell responses and vaccination against tumor-associated antigens are two methods of treatment. CAR-T cells, vaccine-based therapeutics, dendritic cells (DCs) in combination with pro-inflammatory cytokines and NKs, adoptive cell transfer, and immune checkpoint inhibitors are promising treatments for PC. Carcinoembryonic antigen-expressing tumors are suppressed by IP administration of CAR-T cells. This reaction was strengthened by anti-PD-L1 or anti-Gr1. When paired with CD137 co-stimulatory signaling, CAR-T cells for folate receptor cancers made it easier for T-cell tumors to find their way to and stay alive in the body.

The Role of CTNNA1 in Malignancies: An Updated Review

Catenin alpha 1 (CTNNA1), encoding α-catenin, is involved in several physiological activities, such as adherens junction synthesis and signal transduction. Recent studies have suggested additional functions for CTNNA1 malignancies. This review systematically summarizes the varying functions of CTNNA1 in different tumors and briefly describes the diverse pathways and mechanisms involved in different types of tumors. CTNNA1 is abnormally expressed in leukemia and solid tumor such as cancers of digestive system, genitourinary system and breast, and it's related to the occurrence, development, and prognosis of tumors. In addition, the possible physiological processes involving CTNNA1, such as methylation, miRNA interference, or regulatory axes, similar to those of CDH1, SETD2, and hsa-miR-30d-5p/GJA1 are also summarized here. The precise mechanism of CTNNA1 in most cancers remains uncertain; hence, additional pre-clinical studies of CTNNA1 are warranted for potential early tumor diagnosis, prognosis, and treatment.

First estimates of diffuse gastric cancer risks for carriers of CTNNA1 germline pathogenic variants

BACKGROUND

Pathogenic variants (PV) of CTNNA1 are found in families fulfilling criteria for hereditary diffuse gastric cancer (HDGC) but no risk estimates were available until now. The aim of this study is to evaluate diffuse gastric cancer (DGC) risks for carriers of germline CTNNA1 PV.

METHODS

Data from published CTNNA1 families were updated and new families were identified through international collaborations. The cumulative risk of DGC by age for PV carriers was estimated with the genotype restricted likelihood (GRL) method, taking into account non-genotyped individuals and conditioning on all observed phenotypes and genotypes of the index case to obtain unbiased estimates. A non-parametric (NP) and the Weibull functions were used to model the shape of penetrance function with the GRL. Kaplan-Meier incidence curve and standardised incidence ratios were also computed. A 'leave-one-out' strategy was used to evaluate estimate uncertainty.

RESULTS

Thirteen families with 46 carriers of PV were included. The cumulative risks of DGC at 80 years for carriers of CTNNA1 PV are 49% and 57%, respectively with the Weibull GRL and NP GRL methods. Risk ratios to population incidence reach particularly high values at early ages and decrease with age. At 40 years, they are equal to 65 and 833, respectively with the Weibull GRL and NP GRL.

CONCLUSION

This is the largest series of CTNNA1 families that provides the first risk estimates of GC. These data will help to improve management and surveillance for these patients and support inclusion of CTNNA1 in germline testing panels.

Clonal Hematopoiesis and Mosaicism Revealed by a Multi-Tissue Analysis of Constitutional TP53 Status

BACKGROUND

Though germline TP53 pathogenic/likely pathogenic variants (PV) are associated with Li-Fraumeni syndrome, many detected by multigene panels represent aberrant clonal expansion (ACE), most due to clonal hematopoiesis (CH). Discerning ACE/CH from germline variants and postzygotic mosaicism (PZM) is critically needed for risk assessment and management.

METHODS

Participants in the Li-Fraumeni & TP53 Understanding & Progress (LiFT UP) study with a TP53 PV were eligible. Demographics, personal/family cancer history, and clinical laboratory test reports were obtained. DNA from multiple tissues was analyzed using a custom QIAseq assay (ACE panel) that included TP53 and other CH-associated genes; the ACE panel and eyebrow follicles were assessed in a workflow to discern TP53 PV clinical categories.

RESULTS

Among 134 participants there was a significant difference for the age at diagnosis (P < 0.001), component cancers (P = 0.007), and clinical testing criteria (P < 0.001), comparing germline with PZM or ACE. ACE panel analysis of DNA from 55 sets of eyebrow follicles (mean 1.4 ug) and 36 formalin-fixed, paraffin imbedded tissues demonstrated low variance (SE, 3%; P = 0.993) for TP53 variant allele fraction, with no significant difference (P = 0.965) between tissue types, and detected CH gene PVs. Of 55 multi-tissue cases, germline status was confirmed for 20, PZM in seven, ACE for 25, and three were indeterminate. Additional CH variants were detected in six ACE and two germline cases.

CONCLUSIONS

We demonstrated an effective approach and tools for discerning germline TP53 status.

IMPACT

Discernment of PZM and TP53-driven CH increases diagnostic accuracy and enables risk-appropriate care.

Identification of a Five-Gene Panel to Assess Prognosis for Gastric Cancer

Methods

Two datasets were used as training and validation cohorts to establish the predictive model. We used three types of screening criteria: background analysis, pathway analysis, and functional analysis provided by the cBioportal website. Fisher's exact test and multivariable logistic regression were performed to screen out related genes. Furthermore, we performed receiver operating characteristic (ROC) and Kaplan–Meier curve analyses to evaluate the correlation between the selected genes and overall survival.

Result

We screened five genes (KNL1, NRXN1, C6, CCDC169-SOHLH2, and TTN) that were highly related to recurrence of GC. The area under the receiver operating characteristic (ROC) curve was 0.813, which was much higher than that of the baseline model (AUC = 0.699). This result suggested that the mutation of five selected genes had a significant effect on the prediction of recurrence compared with other factors (age, stages, history, etc.). Furthermore, the Kaplan-Meier estimator also revealed that the mutation of five genes positively correlated with patient survival.

Conclusions

The patients who have mutations in these five genes may experience longer survival than those who do not have mutations. This five-gene panel will likely be a practical tool for prognostic evaluation and will provide another possible way for clinicians to determine therapy.

Gastric cancer genetic predisposition and clinical presentations: Established heritable causes and potential candidate genes

Tumour risk syndromes (TRS) are characterized by an increased risk of early-onset cancers in a familial context. High cancer risk is mostly driven by loss-of-function variants in a single cancer-associated gene. Presently, predisposition to diffuse gastric cancer (DGC) is explained by CDH1 and CTNNA1 pathogenic and likely pathogenic variants (P/LP), causing Hereditary Diffuse Gastric Cancer (HDGC); while APC promoter 1B single nucleotide variants predispose to Gastric Adenocarcinoma and Proximal Polyposis of the Stomach (GAPPS). Familial Intestinal Gastric Cancer (FIGC), recognized as a GC-predisposing disease, remains understudied and genetically unsolved. GC can also occur in the spectrum of other TRS. Identification of heritable causes allows defining diagnostic testing criteria, helps to clinically classify GC families into the appropriate TRS, and allows performing pre-symptomatic testing identifying at-risk individuals for downstream surveillance, risk reduction and/or treatment. However, most of HDGC, some GAPPS, and most FIGC patients/families remain unsolved, expecting a heritable factor to be discovered. The missing heritability in GC-associated tumour risk syndromes (GC-TRS) is likely explained not by a single major gene, but by a diversity of genes, some, predisposing to other TRS. This would gain support if GC-enriched small families or apparently isolated early-onset GC cases were hiding a family history compatible with another TRS. Herein, we revisited current knowledge on GC-TRS, and searched in the literature for individuals/families bearing P/LP variants predisposing for other TRS, but whose probands display a clinical presentation and/or family history also fitting GC-TRS criteria. We found 27 families with family history compatible with HDGC or FIGC, harbouring 28 P/LP variants in 16 TRS-associated genes, mainly associated with DNA repair. PALB2 or BRCA2 were the most frequently mutated candidate genes in individuals with family history compatible with HDGC and FIGC, respectively. Consolidation of PALB2 and BRCA2 as HDGC- or FIGC-associated genes, respectively, holds promise and worth additional research. This analysis further highlighted the influence, that proband's choice and small or unreported family history have, for a correct TRS diagnosis, genetic screening, and disease management. In this review, we provide a rational for identification of particularly relevant candidate genes in GC-TRS.

Immunotherapy for Peritoneal Metastases from Gastric Cancer: Rationale, Current Practice and Ongoing Trials

Peritoneal metastases from gastric cancer play a key role in the fatal prognosis of the disease. The lack of efficacy of actual therapeutic approaches together with the outcomes achieved with checkpoint inhibitors in gastric cancer compel us to address the current state-of-the-art immunotherapy treatment of peritoneal dissemination. The immunogenicity of the peritoneum has been described to be particularly active at omentum and peritoneal lymph nodes. Also, both innate and acquired immunity seems to be involved at different molecular levels. Recent works show PDL1 expression being less present at the peritoneal level; however, some clinical trials have begun to yield results. For example, the ATTRACTION-2 trial has demonstrated the activity of Nivolumab in heavily pretreated patients even though peritoneal metastases were diagnosed in a 30% of them. Despite positive results in the metastatic setting, peritoneal responses to systemic checkpoint inhibitors remains unclear, therefore, new strategies for intraperitoneal immunotherapy are being proposed for different ongoing clinical trials.

Genetic epidemiology of BRCA1- and BRCA2-associated cancer across Latin America

The prevalence and contribution of BRCA1/2 (BRCA) pathogenic variants (PVs) to the cancer burden in Latin America are not well understood. This study aims to address this disparity. BRCA analyses were performed on prospectively enrolled Latin American Clinical Cancer Genomics Community Research Network participants via a combination of methods: a Hispanic Mutation Panel (HISPANEL) on MassARRAY; semiconductor sequencing; and copy number variant (CNV) detection. BRCA PV probability was calculated using BRCAPRO. Among 1,627 participants (95.2% with cancer), we detected 236 (14.5%) BRCA PVs; 160 BRCA1 (31% CNVs); 76 BRCA2 PV frequency varied by country: 26% Brazil, 9% Colombia, 13% Peru, and 17% Mexico. Recurrent PVs (seen ≥3 times), some region-specific, represented 42.8% (101/236) of PVs. There was no ClinVar entry for 14% (17/125) of unique PVs, and 57% (111/196) of unique VUS. The area under the ROC curve for BRCAPRO was 0.76. In summary, we implemented a low-cost BRCA testing strategy and documented a significant burden of non-ClinVar reported BRCA PVs among Latin Americans. There are recurrent, population-specific PVs and CNVs, and we note that the BRCAPRO mutation probability model performs adequately. This study helps address the gap in our understanding of BRCA-associated cancer in Latin America.

Germline mutations and age at onset of lung adenocarcinoma

BACKGROUND

To identify additional at-risk groups for lung cancer screening, which targets persons with a long history of smoking and thereby misses younger or nonsmoking cases, the authors evaluated germline pathogenic variants (PVs) in patients with lung adenocarcinoma for an association with an accelerated onset.

METHODS

The authors assembled a retrospective cohort (1999-2018) of oncogenetic clinic patients with lung adenocarcinoma. Eligibility required a family history of cancer, data on smoking, and a germline biospecimen to screen via a multigene panel. Germline PVs (TP53/EGFR, BRCA2, other Fanconi anemia [FA] pathway genes, and non-FA DNA repair genes) were interrogated for associations with the age at diagnosis via an accelerated failure time model.

RESULTS

Subjects (n = 187; age, 28-89 years; female, 72.7%; Hispanic, 11.8%) included smokers (minimum of 5 pack-years; n = 65) and nonsmokers (lighter ever smokers [n = 18] and never smokers [n = 104]). Overall, 26.7% of the subjects carried 1 to 2 germline PVs: TP53 (n = 5), EGFR (n = 2), BRCA2 (n = 6), another FA gene (n = 11), or another DNA repair gene (n = 28). After adjustment for smoking, sex, and ethnicity, the diagnosis of lung adenocarcinoma was accelerated 12.2 years (95% confidence interval [CI], 2.5-20.6 years) by BRCA2 PVs, 9.0 years (95% CI, 0.5-16.5 years) by TP53/EGFR PVs, and 6.1 years (95% CI, -1.0 to 12.6 years) by PVs in other FA genes. PVs in other DNA repair genes showed no association. Germline associations did not vary by smoking.

CONCLUSIONS

Among lung adenocarcinoma cases, germline PVs (TP53, EGFR, BRCA2, and possibly other FA genes) may be associated with an earlier onset. With further study, the criteria for lung cancer screening may need to include carriers of high-risk PVs, and findings could influence precision therapy and reduce lung cancer mortality by earlier stage diagnosis.

A multicenter study assessing the prevalence of germline genetic alterations in Chinese gastric-cancer patients

BACKGROUND

Approximately 10% of patients with gastric cancer (GC) have a genetic predisposition toward the disease. However, there is scant knowledge regarding germline mutations in predisposing genes in the Chinese GC population. This study aimed to determine the spectrum and distribution of predisposing gene mutations among Chinese GC patients known to have hereditary high-risk factors for cancer.

METHODS

A total of 40 GC patients from 40 families were recruited from seven medical institutions in China. Next-generation sequencing was performed on 171 genes associated with cancer predisposition. For probands carrying pathogenic/likely pathogenic germline variants, Sanger sequencing was applied to validate the variants in the probands as well as their relatives.

RESULTS

According to sequencing results, 25.0% (10/40) of the patients carried a combined total of 10 pathogenic or likely pathogenic germline variants involving nine different genes: CDH1 (n = 1), MLH1 (n = 1), MSH2 (n = 1), CHEK2 (n = 1), BLM (n = 1), EXT2 (n = 1), PALB2 (n = 1), ERCC2 (n = 1), and SPINK1 (n = 2). In addition, 129 variants of uncertain significance were identified in 27 patients.

CONCLUSIONS

This study indicates that approximately one in every four Chinese GC patients with hereditary high risk factors may harbor pathogenic/likely pathogenic germline alterations in cancer-susceptibility genes. The results further indicate a unique genetic background for GC among Chinese patients.

A Novel, Likely Pathogenic MAX Germline Variant in a Patient With Unilateral Pheochromocytoma

Context

Inherited MYC-associated factor X (MAX) gene pathogenic variants (PVs) increase risk for pheochromocytomas (PCCs) and/or paragangliomas (PGLs) in adults and children. There is little clinical experience with such mutations.

Objective

This report highlights an important approach.

Methods

Clinical assessment, including blood chemistry, imaging studies, and genetic testing were performed.

Results

A 38-year-old Hispanic woman was diagnosed with PCC in 2015, treated with adrenalectomy, and referred to endocrinology clinic. Notably, she presented to her primary care physician 3 years earlier complaining of left flank pain, intermittent diaphoresis, and holocranial severe headache. We confirmed severe hypertension (180/100 mm Hg) over multiple antihypertensive regimens. Biochemical and radiological studies workup revealed high plasma metanephrine of 255 pg/mL (normal range, < 65 pg/mL) and plasma normetanephrine of 240 pg/mL (normal range, < 196 pg/mL). A noncontrast computed tomography scan of the abdomen revealed a 4.2 × 4.3 × 4.9-cm, round-shaped and heterogenous contrast enhancement of the left adrenal gland, and a 2-mm nonobstructive left kidney stone. A presumptive diagnosis of secondary hypertension was made. After pharmacological therapy, laparoscopic left adrenalectomy was performed and confirmed the diagnosis of pheochromocytoma. Based on her age, family history, and a high suspicion for genetic etiology, genetic testing was performed that revealed the presence of a novel likely pathogenic variant involving a splice consensus sequence in the MAX gene, designated c0.64-2A > G.

Conclusion

The phenotype of MAX PV-related disease and paraganglioma are highlighted. The novel c0.64-2A > G mutation is reported here and should be considered in the diagnostic workup of similar cases.

Cancer stem cell marker DCLK1 reprograms small extracellular vesicles toward migratory phenotype in gastric cancer cells

Doublecortin-like kinase 1 (DCLK1) is a putative cancer stem cell marker, a promising diagnostic and prognostic maker for malignant tumors and a proposed driver gene for gastric cancer (GC). DCLK1 overexpression in a majority of solid cancers correlates with lymph node metastases, advanced disease and overall poor-prognosis. In cancer cells, DCLK1 expression has been shown to promote epithelial-to-mesenchymal transition (EMT), driving disruption of cell-cell adhesion, cell migration and invasion. Here, we report that DCLK1 influences small extracellular vesicle (sEV/exosome) biogenesis in a kinase-dependent manner. sEVs isolated from DCLK1 overexpressing human GC cell line MKN1 (MKN1^OE -sEVs), promote the migration of parental (non-transfected) MKN1 cells (MKN1^PAR ). Quantitative proteome analysis of MKN1^OE -sEVs revealed enrichment in migratory and adhesion regulators (STRAP, CORO1B, BCAM, COL3A, CCN1) in comparison to MKN1^PAR -sEVs. Moreover, using DCLK1-IN-1, a specific small molecule inhibitor of DCLK1, we reversed the increase in sEV size and concentration in contrast to other EV subtypes, as well as kinase-dependent cargo selection of proteins involved in EV biogenesis (KTN1, CHMP1A, MYO1G) and migration and adhesion processes (STRAP, CCN1). Our findings highlight a specific role of DCLK1-kinase dependent cargo selection for sEVs and shed new light on its role as a regulator of signaling in gastric tumorigenesis.

Status of CHEK2 and p53 in patients with early-onset and conventional gastric cancer

Gastric cancer (GC) is the fourth most common cause of cancer-associated death. Based on the age at diagnosis, GC is divided into early-onset GC (EOGC; ≤45 years) and conventional GC (CGC; >45 years). Mutations in the cell cycle checkpoint kinase 2 (CHEK2) and TP53 genes are associated with several types of cancer; however, their genetic defects in GC remain poorly understood. The aim of the present study was to determine the subcellular distribution of the CHEK2 protein and its redistribution following DNA damage, to improve the understanding of the DNA damage response. Genetic alterations and patterns of expression of CHEK2 and p53 proteins were investigated to identify potential biological markers and indicators of GC development. Additionally, the affected signaling pathways and their clinical importance in GC development and associated syndromes were investigated. A total of 196 GC samples (89 CGC and 107 EOGC samples) were used in the present study. DNA from 53 samples (18 CGC and 35 EOGC samples) was sequenced using targeted next-generation sequencing technology to identify and compare common and rare mutations associated with GC. Subsequently, the cytoplasmic and nuclear expression levels of CHEK2, phosphorylated (p)-CHEK2 at threonine 68 and p53 in GC tissues were determined via immunohistochemistry. Sequencing resulted in the identification of 63 single nucleotide polymorphisms (SNPs) in the CHEK2 gene amongst 5 different variants, and the intron variant c.319+379A>G was the most common SNP. In the TP53 gene, 57 different alterations were detected amongst 9 variant types, and the missense variant c.215C>G was the most common. Nuclear CHEK2 expression was high in both the EOGC and CGC subtypes. However, the prevalence of cytoplasmic CHEK2 expression (P<0.001) and nuclear p-CHEK2 expression (P=0.011) was significantly higher in CGC compared with in EOGC tissues. There was a statistically significant difference between high and low cytoplasmic CHEK2 expression in patients with p53-positive EOGC compared with in patients with p53-positive CGC (P=0.002). The present study was designed to determine the association between CHEK2 and p53 expression patterns in patients with EOGC and CGC, as well as genetic alterations in the CHEK2 and TP53 genes.

Identification of New Genes Involved in Germline Predisposition to Early-Onset Gastric Cancer

The genetic cause for several families with gastric cancer (GC) aggregation is unclear, with marked relevance in early-onset patients. We aimed to identify new candidate genes involved in GC germline predisposition. Whole-exome sequencing (WES) of germline samples was performed in 20 early-onset GC patients without previous germline mutation identified. WES was also performed in nine tumor samples to analyze the somatic profile using SigProfilerExtractor tool. Sequencing germline data were filtered to select those variants with plausible pathogenicity, rare frequency and previously involved in cancer. Then, a manual filtering was performed to prioritize genes according to current knowledge and function. These genetic variants were prevalidated with Integrative Genomics Viewer 2.8.2 (IGV). Subsequently, a further selection step was carried out according to function and information obtained from tumor samples. After IGV and selection step, 58 genetic variants in 52 different candidate genes were validated by Sanger sequencing. Among them, APC, FAT4, CTNND1 and TLR2 seem to be the most promising genes because of their role in hereditary cancer syndromes, tumor suppression, cell adhesion and Helicobacter pylori recognition, respectively. These encouraging results represent the open door to the identification of new genes involved in GC germline predisposition.

Hydrogen inhibits the proliferation and migration of gastric cancer cells by modulating lncRNA MALAT1/miR-124-3p/EZH2 axis

Background

Gastric cancer is one of the most prevalent and deadly malignancies without efficient treatment option. This study aimed to investigate the effect of hydrogen gas on the behavior of gastric cancer cells.

Methods

Gastric cancer cell lines MGC-803 and BGC-823 were treated with or without H₂ /O₂ gas mixture (66.7%:33.3% v/v). Proliferation and migration were assessed by MTT and scratch wound healing assays respectively. The expression of lncRNA MALAT1, miR-124-3p, and EZH2 was analyzed by real-time quantitative PCR and/or western blot. Tumor growth was estimated using xenograft mouse model.

Results

H₂ gas significantly inhibited gastric tumor growth in vivo and the proliferation, migration, and lncRNA MALAT1 and EZH2 expression of gastric cancer cells while upregulated miR-124-3p expression. LncRNA MALAT1 overexpression abolished all the aforementioned effects of H₂. LncRNA MALAT1 and miR-124-3p reciprocally inhibited the expression of each other. MiR-124-3p mimics abrogated lncRNA MALAT1 promoted EZH2 expression and gastric cancer cell proliferation and migration.

Conclusions

These data demonstrated that H₂ might be developed as a therapeutics of gastric cancer and lncRNA MALAT1/miR-124-3p/EZH2 axis could be a target for intervention.

Establish a Scoring Model for High-Risk Population of Gastric Cancer and Study on the Pattern of Opportunistic Screening

Objective

To investigate and study the related risk factors of gastric cancer (GC) patients, to establish a high-risk scoring model of GC by multiple logistic regression analysis, and to explore the establishment of a GC screening mode with clinical opportunistic screening as the main method, and by using the pattern of opportunistic screening to establish the screening of high-risk GC patients and the choice of screening methods in the clinical outpatient work.

Methods

Collected the epidemiological questionnaire of 99 GC cases and 284 non-GC patients (other chronic gastric diseases and normal) diagnosed by the General Hospital of Ningxia Medical University from October 2017 to March 2019. Serum pepsinogen (PG) levels were measured by enzyme-linked immunosorbent assay (ELISA) and confirmed Helicobacter pylori (Hp) infection in gastric mucosa tissues by Giemsa staining. Determined the high-risk factors and established a scoring model through unconditional logistic regression model analysis, and the ROC curve determined the cut-off value. Then, we followed up 26 patients of nongastric cancer patients constituted a validation group, which validated the model.

Results

The high-risk factors of GC included age ≥ 55, male, drinking cellar or well water, family history of GC, Hp infection, PGI ≤ 43.6 μg/L, and PGI/PGII ≤ 2.1. Established the high-risk model: Y = A × age + 30 × gender + 30 × drinking water + 30 × Hp infection + 50 × family history of GC + B × PG level. The ROC curve determined that the cut-off value for high-risk GC population was ≥155, and the area under the curve (AUC) was 0.875, the sensitivity and specificity were 87.9% and 71.5%.

Conclusions

According to the risk factors of GC, using statistical methods can establish a high-risk scoring model of GC, and the score ≥ 155 is divided into the screening cut-off value for high-risk GC population. Using this model for clinical outpatient GC screening is cost-effective and has high sensitivity and specificity.

Molecular biology and immunology of gastric cancer peritoneal metastasis

Peritoneal metastases occur in 55-60% of patients with gastric cancer (GC) and are associated with a 2% 5-year overall survival rate. There are limited treatment options for these patients, and no targeted therapy or immunotherapy is available. Rational therapeutic targets remain to be found. In this review, we present the published literature and our own recent experience in molecular biology to identify important molecules and signaling pathways as well as cellular immunity involved in the peritoneal metastasis of GC. We also suggest potential novel strategies for improving the outcomes of GC patients with peritoneal metastasis.

Molecular characteristics of synchronous multiple gastric cancer

Rationale: Multiple gastric cancer (MGC) is characterized by the presence of more than two different tumors in the stomach. However, the clonal relationship and carcinogenesis of MGC remain unclear. We investigated the clonal relationship and role of germline mutations in the carcinogenesis of MGC.

Methods: We gathered 16 multiple gastric cancer patients. Thirty-three tumor samples and sixteen normal gastric tissue or blood samples were obtained from January 2016 to December 2017. We also conducted analyses for 208 gastric cancer and 49 esophagogastric junction cancer (GC-EGJ) tumors from TCGA. DNA extraction from our samples was conducted for whole-exome sequencing (WES).

Results: Tumor mutation burden (TMB) was not statistically significant within database and our data in the GC-EGJ (P=0.0591) and GC groups (P=0.3113). The mutation spectrum and signatures also showed uniform distributions in GC and GC-EGJ groups within our data and TCGA database. Among sixteen patients, four were identified as monoclonal, in which 11, 10, 26 and 6 somatic mutations were shared within different tumors of P7, P8, P9 and P16, respectively. However, no common mutation between different tumors of the same patient was found among the other 12 patients. After identifying predisposing genes, we found that germline MSH2 and NCOR2 mutations were significantly dominant in 8/12 and 10/12 of genetic MGC patients. Additionally, all patients were identified with MSH2 mutations in cancer samples of those genetic MGC patients. Taking genetic MGCs as a whole, we identified that TP53 were significantly mutated in 14 of 25 tumor samples.

Main conclusions: WES analyses are suggestive of monoclonal and polyclonal origin of MGC, which may promote the classification of MGC into genetic and metastatic MGC. For patients with genetic MGC, germline MSH2 X314_splice variants may contribute to carcinogenesis, thus prompting the consideration of more radical surgery and/or anti-PD-1/PD-L1 therapy.

CDH1 Mutation Distribution and Type Suggests Genetic Differences between the Etiology of Orofacial Clefting and Gastric Cancer

Pathogenic variants in CDH1, encoding epithelial cadherin (E-cadherin), have been implicated in hereditary diffuse gastric cancer (HDGC), lobular breast cancer, and both syndromic and non-syndromic cleft lip/palate (CL/P). Despite the large number of CDH1 mutations described, the nature of the phenotypic consequence of such mutations is currently not able to be predicted, creating significant challenges for genetic counselling. This study collates the phenotype and molecular data for available CDH1 variants that have been classified, using the American College of Medical Genetics and Genomics criteria, as at least ‘likely pathogenic’, and correlates their molecular and structural characteristics to phenotype. We demonstrate that CDH1 variant type and location differ between HDGC and CL/P, and that there is clustering of CL/P variants within linker regions between the extracellular domains of the cadherin protein. While these differences do not provide for exact prediction of the phenotype for a given mutation, they may contribute to more accurate assessments of risk for HDGC or CL/P for individuals with specific CDH1 variants.

Hereditary gastric cancer: what's new? Update 2013-2018

Around 10-20% of gastric cancer patients have relatives with a diagnosis of GC and in 1-3% of patients a genetic cause can be confirmed. Histopathologically, GC is classified into intestinal-type, with glandular growth, and diffuse-type with poorly cohesive growth pattern often with signet ring cells. Familial or hereditary GC is classified into hereditary diffuse GC (HDGC), familial intestinal GC (FIGC) and polyposis forms. This review focuses on recent research findings and new concepts of hereditary GC.

Identification of c.1531C>T Pathogenic Variant in the CDH1 Gene as a Novel Germline Mutation of Hereditary Diffuse Gastric Cancer

Germline pathogenic variants in the CDH1 gene are a well-established cause of hereditary diffuse gastric cancer (HDGC) syndrome. The aim of this study was to characterize CDH1 mutations associated with HDGC from Chile, a country with one of the highest incidence and mortality rates in the world for gastric cancer (GC). Here, we prospectively include probands with family history/early onset of diffuse-type of GC. The whole coding sequence of the CDH1 gene was sequenced from genomic DNA in all patients, and a multidisciplinary team managed each family member with a pathogenic sequence variant. Thirty-six cases were included (median age 44 years/male 50%). Twenty-seven (75%) patients had diffuse-type GC at ≤50 years of age and 19 (53%) had first or second-degree family members with a history of HDGC. Two cases (5.5%) carried a non-synonymous germline sequence variant in the CDH1 gene: (a) The c.88C>A missense variant was found in a family with three diffuse-type GC cases; and (b) c.1531C>T a nonsense pathogenic variant was identified in a 22-year-old proband with no previous family history of HDGC. Of note, six family members carry the same nonsense pathogenic variant. Prophylactic gastrectomy in the proband's sister revealed stage I signet-ring cell carcinoma. The finding of 1531C>T pathogenic variant in the CDH1 in proband with no previous family history of HDGC warrants further study to uncover familial clustering of disease in CDH1 negative patients. This finding may be particularly relevant in high incidence countries, such as the case in this report.

Multigene Panel Testing Increases the Number of Loci Associated with Gastric Cancer Predisposition

The main gene involved in gastric cancer (GC) predisposition is CDH1, the pathogenic variants of which are associated with diffuse-type gastric cancer (DGC) and lobular breast cancer (LBC). CDH1 only explains a fraction (10–50%) of patients suspected of DGC/LBC genetic predisposition. To identify novel susceptibility genes, thus improving the management of families at risk, we performed a multigene panel testing on selected patients. We searched for germline pathogenic variants in 94 cancer-related genes in 96 GC or LBC Italian patients with early-onset and/or family history of GC. We found CDH1 pathogenic variants in 10.4% of patients. In 11.5% of cases, we identified loss-of-function variants in BRCA1, BRCA2, PALB2, and ATM breast/ovarian cancer susceptibility genes, as well as in MSH2, PMS2, BMPR1A, PRF1, and BLM genes. In 78.1% of patients, we did not find any variants with clear-cut clinical significance; however, 37.3% of these cases harbored rare missense variants predicted to be damaging by bioinformatics tools. Multigene panel testing decreased the number of patients that would have otherwise remained genetically unexplained. Besides CDH1, our results demonstrated that GC pathogenic variants are distributed across a number of susceptibility genes and reinforced the emerging link between gastric and breast cancer predisposition.

Genetics of gastric cancer: what do we know about the genetic risks?

An appreciable number of patients with gastric cancer have an underlying hereditary cancer susceptibility syndrome as the cause of their gastric cancer, particularly those with early onset gastric cancer or a family history of gastric or other cancers. Pathogenic germline variants in specific genes account for the known gastric cancer predisposition syndromes. Germline genetic testing can identify individuals and their family members who carry inherited pathogenic gene variants, and thus have increased risk of developing gastric or other cancers. Ideally, germline pathogenic variants can be identified in family members before the onset of disease, when early detection or prevention strategies can be implemented most effectively to decrease gastric cancer- related morbidity and mortality. This article reviews some of the currently known gastric cancer predisposition syndromes and their associated cancer risks. We also discuss current research and advances in the field of genetic gastric cancer susceptibility.

Crosstalk Between DNA Damage and Inflammation in the Multiple Steps of Gastric Carcinogenesis

Over the last years, intensive investigations in molecular biology and cell physiology extended tremendously the knowledge about the association of inflammation and cancer. In frame of this paradigm, the human pathogen Helicobacter pylori triggers gastritis and gastric ulcer disease, and contributes to the development of gastric cancer. Mechanisms, by which the bacteria-induced inflammation in gastric mucosa leads to intestinal metaplasia and carcinoma, are represented in this review. An altered cell-signaling response and increased production of free radicals by epithelial and immune cells account for the accumulation of DNA damage in gastric mucosa, if infection stays untreated. Host genetics and environmental factors, especially diet, can accelerate the process, which offers the opportunity of intervention based on a balanced nutrition. It is supposed that inflammation might influence stem- or progenitor cells in gastric tissue predisposing for metaplasia or tumor relapse. Herein, DNA is strongly mutated and labile, which restricts therapy options. Thus, the understanding of the mechanisms that underlie gastric carcinogenesis will be of preeminent importance for the development of strategies for screening and early detection. As most gastric cancer patients face late-stage disease with a poor overall survival, the development of multi-targeted therapeutic intervention strategies is a major challenge for the future.

Enolase1 overexpression regulates the growth of gastric cancer cells and predicts poor survival

Gastric cancer has become the third most common cancer around the world. In patients with gastric cancer, the 5-year survival rate is still low. However, the mechanism underlying gastric cancer remains largely unknown. As a glycolytic enzyme, enolase 1 (ENO1) is widely expressed in most tissues. The functions of ENO1 have been reported in various types of cancer. Here in this study, we identified that ENO1 promoted the growth of gastric cancer cells through diverse mechanisms. Our immunohistochemical, bioinformatic and Western blot data showed that ENO1 was significantly overexpressed in human gastric cancer cell lines and tissues. The survival analysis revealed that ENO1 overexpression predicted poor survival in the patients suffering gastric cancer. Knockdown of ENO1 expression repressed the rate of proliferation and capacity of colony formation in two human gastric cancer cell lines (MGC-803 and MKN-45). In addition, knockdown of the expression of ENO1 led to the arrest of the cell cycle at the G1 phase and promoted the apoptosis of MKN-45 and MGC-803 cells. The further microarray and bioinformatic analysis revealed that ENO1 regulated the expression of diverse genes, many of which are involved in the progress of cancer. Taken together, our data demonstrated that ENO1 was an oncogene-like factor and might serve as a promising target for the treatment of human gastric cancer.

Geospatial analyses identify regional hot spots of diffuse gastric cancer in rural Central America

BACKGROUND

Geospatial technology has facilitated the discovery of disease distributions and etiology and helped target prevention programs. Globally, gastric cancer is the leading infection-associated cancer, and third leading cause of cancer mortality worldwide, with marked geographic variation. Central and South America have a significant burden, particularly in the mountainous regions. In the context of an ongoing population-based case-control study in Central America, our aim was to examine the spatial epidemiology of gastric cancer subtypes and H. pylori virulence factors.

METHODS

Patients diagnosed with gastric cancer from 2002 to 2013 in western Honduras were identified in the prospective gastric cancer registry at the principal district hospital. Diagnosis was based on endoscopy and confirmatory histopathology. Geospatial methods were applied using the ArcGIS v10.3.1 and SaTScan v9.4.2 platforms to examine regional distributions of the gastric cancer histologic subtypes (Lauren classification), and the H. pylori CagA virulence factor. Getis-Ord-Gi hot spot and Discrete Poisson SaTScan statistics, respectively, were used to explore spatial clustering at the village level (30-50 rural households), with standardization by each village's population. H. pylori and CagA serologic status was determined using the novel H. pylori multiplex assay (DKFZ, Germany).

RESULTS

Three hundred seventy-eight incident cases met the inclusion criteria (mean age 63.7, male 66.3%). Areas of higher gastric cancer incidence were identified. Significant spatial clustering of diffuse histology adenocarcinoma was revealed both by the Getis-Ord-GI* hot spot analysis (P-value < 0.0015; range 0.00003-0.0014; 99%CI), and by the SaTScan statistic (P-value < 0.006; range 0.0026-0.0054). The intestinal subtype was randomly distributed. H. pylori CagA had significant spatial clustering only in association with the diffuse histology cancer hot spot (Getis-Ord-Gi* P value ≤0.001; range 0.0001-0.0010; SaTScan statistic P value 0.0085). In the diffuse gastric cancer hot spot, the lowest age quartile range was 21-46 years, significantly lower than the intestinal cancers (P = 0.024).

CONCLUSIONS

Geospatial methods have identified a significant cluster of incident diffuse type adenocarcinoma cases in rural Central America, suggest of a germline genetic association. Further genomic and geospatial analyses to identify potential spatial patterns of genetic, bacterial, and environmental risk factors may be informative.

Insights into BRCA Cancer Predisposition from Integrated Germline and Somatic Analyses in 7632 Cancers

BACKGROUND

It is often assumed any cancer in a germline BRCA1 or BRCA2 (collectively termed BRCA) mutation carrier was caused by that mutation. It is also often assumed the occurrence of breast or ovarian cancer in an individual with a variant of uncertain significance (VUS) suggests the VUS is pathogenic. These assumptions have profound management implications for cancer patients and healthy individuals.

METHODS

We compared the frequency of BRCA mutations, allele loss, and Signature 3 in 7632 individuals with 28 cancers and 1000 population controls. Because only increased frequency was the focus of the study, all statistical tests were one-sided.

RESULTS

Individuals with breast or ovarian cancer had increased germline BRCA pathogenic mutation frequencies compared to controls (P = 1.0x10-10 and P = 1.4x10-34, respectively). There was no increase in other cancer types. Wild-type allele loss and Signature 3 were statistically significantly higher in breast and ovarian cancers with BRCA mutations compared with other cancers with BRCA mutations (P = 5.1x10-10 and P = 3.7x10-9) and cancers without BRCA mutations (P = 2.8x10-53 and P = 1.0x10-134). There was no difference between non-breast and non-ovarian cancers with BRCA mutations and cancers without BRCA mutations. Allele loss and Signature 3 were statistically significantly higher in breast and ovarian cancers in individuals with BRCA pathogenic mutations compared to those with VUS (P = 3.8x10-17 and P = 1.6x10-8) or benign variants (P = 1.2x10-28 and P = 2.2x10-10). There was no difference between individuals with BRCA VUS and those with benign variants.

CONCLUSIONS

These data show that non-breast and non-ovarian cancers in individuals with germline BRCA pathogenic mutations are often not causally related to the mutation and that BRCA VUS are highly unlikely to be pathogenic. These results should reduce inappropriate management of germline BRCA information.

Genetics and genomics in Peru: Clinical and research perspective

Peruvians currently preserve in their DNA the history of 2.5 million years of human evolution and 150,000 years of migration from Africa to Peru or the Americas. The development of Genetics and Genomics in the clinical and academic field is shown in this review.

Gastric adenocarcinoma and proximal polyposis of the stomach: diagnosis and clinical perspectives

Gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS) is a recently described, rare gastric polyposis syndrome. It is characterized by extensive involvement of the fundus and body of the stomach with fundic gland polyps sparing the antrum and lesser curvature, an autosomal dominant inheritance pattern with incomplete penetrance, and a significant predisposition for the development of gastric adenocarcinoma. Due to the recent discovery of APC promotor IB mutations (c.-191T>C, c.-192A>G, and c.-195A>C), which reduce binding of the transcription factor Yin Yang 1 (YY1) and transcriptional activity of the promotor, as its underlying genetic perturbation, GAPPS has been added to the growing molecular class of APC-associated disorders. Recent reports on family members afflicted by gastric polyposis due to GAPPS have described the development of metastatic cancer or the presence of invasive gastric adenocarcinoma in total gastrectomy specimens after variable periods of endoscopic surveillance emphasizing the need for an improved understanding of the to-date poorly characterized natural history of the syndrome. There are, however, currently no guidelines on screening, timing of prophylactic gastrectomy, or endoscopic surveillance for GAPPS available. In this review, we summarize the clinical, pathological, and genetic aspects of GAPPS as well as management approaches to this rare cancer predisposition syndrome, highlighting the need for early recognition, a multidisciplinary approach, and the creation of prospective family registries and consensus guidelines in the near future.

Exploring the differences between early-onset gastric cancer and traditional-onset gastric cancer

Background

The current study sought to explore the potential clinical, epidemiological and genetic differences between early-onset gastric cancer (E-gastric cancer: defined as 20-39 years) and traditional-onset gastric cancer (T-gastric cancer: defined as ≥40 years).

Methods

Datasets from the following sources were searched: Surveillance, Epidemiology and End Results database [2000-2014], Behavioral Risk Factor Surveillance Survey and the cancer genome atlas (TCGA). Clinicopathological characteristics, trends, and genetic findings were compared between E-gastric cancer and T-gastric cancer. Moreover, correlations with relevant risk factors were sought after.

Results

A total of 95,323 gastric cancer patients were identified in the period from 2000 to 2014. While T-gastric cancer was decreasing during the study period (-1.4; P<0.05), E-gastric cancer was stable during the study period. E-gastric cancer is less prevalent in males (51.1% vs. 61.0%; P<0.0001), and white patients (68.9% vs. 71.4%; P<0.0001). E-gastric cancer patients usually present with poorly differentiated histology (55.3% vs. 48.0%; P<0.0001) as well as more aggressive histological subtypes (e.g., diffuse histology or linitis plastica). No difference can be detected with regards to risk factor correlations between E-gastric cancer and T-gastric cancer. Only four patients with E-gastric cancer were available in the provisional TCGA dataset at the time of the study.

Conclusions

E-gastric cancer is a potentially distinct disease entity with specific clinicopathological and trend patterns compared to conventional T-gastric cancer. Further studies are needed to explore the potential etiologic basis as well as to investigate the clinical consequences of this distinction. The impact of this distinction on minority populations requires further assessment as well.

Resolving gastric cancer aetiology: an update in genetic predisposition

Every year gastric cancer accounts for nearly 1 million new cases and more than 720 000 deaths worldwide. Prognosis is dismal because most patients are diagnosed with advanced disease; as such, gastric cancer outcomes will benefit from better methods for identification of at-risk individuals that can be targeted for early detection. One approach to targeting high-risk populations is to identify individuals who are genetically predisposed to gastric cancer, as up to 15% of all patients report family history of the disease. On the basis of clinical manifestations, three gastric cancer syndromes have been described, but the diagnosis of some of these syndromes is suboptimal and could benefit from genetic information. Over the past decade, genome-wide association and next-generation sequencing studies have identified several low penetrance variants and high-risk genes, considerably increasing our understanding of inherited gastric cancer predisposition. From these studies, PALB2 has emerged as a new familial gastric cancer gene. Furthermore, genetic analyses in patients with sporadic gastric cancer suggest that more than 10% of all cases have pathogenic mutations, a finding of great importance for cancer aetiology. In this Review, we summarise the role of genetics in gastric cancer aetiology and the implications of genetics findings for the prevention of this malignancy.

The effect of Ganoderma lucidum extract on immunological function and identify its anti-tumor immunostimulatory activity based on the biological network

Ganoderma lucidum extract (GLE) has shown positive effects for tumor treatment. However, the molecular mechanism of GLE treatment is unknown. In this study, a Hepa1-6-bearing C57 BL/6 mouse model was established to explore the anti-tumor and immunostimulatory activity of GLE treatment. The results showed that GLE effectively inhibited tumor growth without hepatic/renal toxicity and bone marrow suppression, and might enhancing immunological function. Based on the mRNA profiles of GLE treated and untreated mice, 302 differentially expressed (DE) mRNAs were identified and 6 kernel mRNAs were identified from the established protein-protein interaction (PPI) network. Quantitative RT-PCR and western-blot analysis indicated that 6 mRNAs have had statistically significant differences between the GLE treated and untreated mice. Furthermore, four kernel pathways were isolated from the KEGG-Target network, including the Jak-STAT signaling pathway, T cell receptor signaling pathway, PI3K-Akt signaling pathway, and cytokine-cytokine receptor interaction. Western-blot and cytokine detection results demonstrated that GLE suppressed growth and proliferation of tumors by the Jak-STAT signaling pathway, T cell receptor signaling pathway and PI3K-Akt signaling pathway, but also regulated the expression levels of serum immune cytokines and improved the anti-tumor immunostimulatory activity.

Germline pathogenic variants in PALB2 and other cancer-predisposing genes in families with hereditary diffuse gastric cancer without CDH1 mutation: a whole-exome sequencing study

BACKGROUND

Germline pathogenic variants in the E-cadherin gene (CDH1) are strongly associated with the development of hereditary diffuse gastric cancer. There is a paucity of data to guide risk assessment and management of families with hereditary diffuse gastric cancer that do not carry a CDH1 pathogenic variant, making it difficult to make informed decisions about surveillance and risk-reducing surgery. We aimed to identify new candidate genes associated with predisposition to hereditary diffuse gastric cancer in affected families without pathogenic CDH1 variants.

METHODS

We did whole-exome sequencing on DNA extracted from the blood of 39 individuals (28 individuals diagnosed with hereditary diffuse gastric cancer and 11 unaffected first-degree relatives) in 22 families without pathogenic CDH1 variants. Genes with loss-of-function variants were prioritised using gene-interaction analysis to identify clusters of genes that could be involved in predisposition to hereditary diffuse gastric cancer.

FINDINGS

Protein-affecting germline variants were identified in probands from six families with hereditary diffuse gastric cancer; variants were found in genes known to predispose to cancer and in lesser-studied DNA repair genes. A frameshift deletion in PALB2 was found in one member of a family with a history of gastric and breast cancer. Two different MSH2 variants were identified in two unrelated affected individuals, including one frameshift insertion and one previously described start-codon loss. One family had a unique combination of variants in the DNA repair genes ATR and NBN. Two variants in the DNA repair gene RECQL5 were identified in two unrelated families: one missense variant and a splice-acceptor variant.

INTERPRETATION

The results of this study suggest a role for the known cancer predisposition gene PALB2 in families with hereditary diffuse gastric cancer and no detected pathogenic CDH1 variants. We also identified new candidate genes associated with disease risk in these families.

FUNDING

UK Medical Research Council (Sackler programme), European Research Council under the European Union's Seventh Framework Programme (2007-13), National Institute for Health Research Cambridge Biomedical Research Centre, Experimental Cancer Medicine Centres, and Cancer Research UK.