Hereditary diffuse gastric cancer: laparoscopic surgical approach associated to rare mutattion of CDH1 gene

Mutational landscape of gastric adenocarcinoma in Latin America: A genetic approach for precision medicine

Latin-America (LATAM) is the second region in gastric cancer incidence; gastric adenocarcinoma (GA) represents 95% of all cases. We provide a mutational landscape of GA highlighting a) germline pathogenic variants associated with hereditary GA, b) germline risk variants associated with sporadic GA, and c) somatic variants present in sporadic GA in LATAM, and analyze how this landscape can be applied for precision medicine. We found that Brazil, Chile, Colombia, Mexico, Peru, and Venezuela are the countries with more published studies from LATAM explicitly related to GA. Our analysis displayed that different germline pathogenic variants for the CDH1 gene have been identified for hereditary GA in Brazilian, Chilean, Colombian, and Mexican populations. An increased risk of developing somatic GA is associated with the following germline risk variants: IL-4, IL-8, TNF-α, PTGS2, NFKB1, RAF1, KRAS and MAPK1 in Brazilian; IL-10 in Chilean; IL-10 in Colombian; EGFR and ERRB2 in Mexican, TCF7L2 and Chr8q24 in Venezuelan population. The path from mutational landscape to precision medicine requires four development levels: 1) Data compilation, 2) Data analysis and integration, 3) Development and approval of clinical approaches, and 4) Population benefits. Generating local genomic information is the initial padlock to overcome to generate and apply precision medicine.

Laparoscopic Prophylactic Total Gastrectomy for Hereditary Diffuse Gastric Cancer in CDH1 Mutation Carriers

Background: Patients with hereditary diffuse gastric cancer (HDGC) and germline mutations in the E-cadherin gene, CDH1, have a very high cumulative lifetime risk of developing diffuse gastric cancer. In these patients, it is formally recommended to perform a prophylactic total gastrectomy (PTG). Materials and Methods: We analyzed the course of patients with HDGC who have undergone PTG in our institution. Pedigree analysis, preoperative screening results, operative course, postoperative data, and complete stomach pathologic examination were performed in all patients. Results: Seven patients with confirmed CDH1 mutation underwent PTG, five were women, and average age was 27 years (range 17-42). Signet ring cell carcinoma was found in 1 patient in the preoperative surveillance endoscopic biopsies. Laparoscopic PTG was performed in all patients. There were two complications, an intestinal obstruction that required reintervention and an asymptomatic esophagojejunal anastomosis leak that resolved with conservative treatment. In all gastrectomy specimens, intramucosal signet ring cell carcinoma foci limited to the lamina propria were found (range 1-31), 83.5% were in the body-fundus region. The mean follow-up was 28.5 months (range 8-72). The mean weight loss was 9% (range 2-18). Postoperative symptoms associated with Dumping syndrome were the most frequent. All the patients reported of being very satisfied with the procedure and of having a better quality of life than expected before the procedure. Conclusion: Laparoscopic PTG is an excellent resource to prevent the development of advanced diffuse gastric cancer (DGC) in patients with HDGC with CDH1 mutation. The procedure was well tolerated with a high satisfaction rate and very good functional results. It should be considered in these patients due to the high risk of developing advanced DGC and the lack of effective and reliable surveillance studies.

Significance of E-cadherin Gene Mutations in Patients With Hereditary Diffuse Gastric Cancer Syndrome: A Systematic Review

Gastric cancer is the third-most fatal cancer in the world. Though over the years, we saw patients mostly with intestinal type accounting for the highest mortality rate, the recent rise of the diffuse form with germline E-cadherin (CDH1) mutations has added a whole new level of interest to study in detail about the association between CDH1 and diffuse gastric cancer (DGC). This introduced a set guideline formulated by Internal Gastric Cancer Linkage Consortium (IGCLC) for patients with family history of diffuse gastric cancer and invasive lobular breast cancer (ILBC). The analysis of this link was also important to set proper management protocol for patients who were CDH1 mutation carriers which now involves genetic counselling, endoscopic surveillance and screening and prophylactic total gastrectomy (PTG). The study was conducted in accordance to the 'PRISMA guidelines for reporting systematic review and meta-analysis'. Peer-reviewed studies were included from the PubMed database and relevant articles were selected to be included in the study. Appropriate inclusion/exclusion criteria with free full text English articles were applied while selecting the articles. A total of 10 studies on review with different study populations showed that of the 42 patients who were diagnosed with diffuse gastric cancer, 88% of them showed a positive germline E-cadherin gene mutation and 100% of the CDH1 mutation carriers showed microscopic changes of signet ring cell adenocarcinoma of the stomach. The beneficial effects of PTG with better survival rates and low mortality rates has outweighed other treatment modalities. Laparoscopic approach has proved to be more useful and a safer approach for gastrectomy surgeries with better post-operative management. The need for prophylactic mastectomy is also increased in the recent times and thus this requires a new set of guidelines for ILBC patients with hereditary diffuse gastric cancer (HDGC) syndrome.

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.

Frequency of CDH1 germline variants and contribution of dietary habits in early age onset gastric cancer patients in Brazil

INTRODUCTION

The contribution of CDH1 germline variants to gastric cancer burden among young adults is unknown in Brazil. We aimed to evaluate the frequency of CDH1 germline variants and the diet/lifestyle habits in early age onset gastric cancer (EOGC, ≤ 55 years old) patients.

METHODOLOGY

From 2013 to 2015, a total of 88 unrelated and consecutive patients diagnosed with EOGC were enrolled. All CDH1 exons and intronic boundaries were sequenced, and large genomic rearrangements were screened by MLPA. CDH1 transcription analysis was performed for variants that could potentially induce an effect on splicing. The diet and lifestyle habits of EOGC patients were compared to Brazilian population diet and lifestyle, obtained from governmental databases.

RESULTS

Of 88 patients, the mean age at EOGC diagnosis was 39 years and 55% fulfilled the criteria for hereditary diffuse gastric cancer. The majority of the tumors were diffuse (74%) and poorly differentiated (80%). In total, 4 novel missense variants of uncertain significance (VUS) were identified: c.313T>A, c.387G>T, c.1676G>A, and c.1806C>A. The MLPA results revealed no rearrangements and CDH1 transcription analysis for variants of interest were inconclusive. EOGC patients had a higher red (OR:2.6, 95%CI:1.4-4.9) and processed (OR:3.1, 95%CI:1.6-6.0) meat intake and higher fruit consumption (OR:0.4, 95%IC:0.3-0.7) compared to eating habits of the Brazilian population.

CONCLUSIONS

No unequivocal pathogenic germline CDH1 variants were identified in Brazilian EOGC patients. Dietary habits may be associated with the EOGC development.

Pathological features of total gastrectomy specimens from asymptomatic hereditary diffuse gastric cancer patients and implications for clinical management

Hereditary diffuse gastric cancer (HDGC) is an autosomal dominant syndrome characterised by multigenerational diffuse gastric cancer, and is mainly caused by germline alterations in the CDH1 gene. Currently, endoscopy has limited diagnostic accuracy, and total gastrectomy (TG) is the treatment of choice for asymptomatic CDH1 carriers. In this study, we aimed to obtain a better understanding of HDGC syndrome by exploring the histopathological findings of TG specimens from asymptomatic HDGC patients. A comprehensive literature review was carried out, searching for TGs performed in asymptomatic HDGC patients. Fourteen unpublished cases, analysed in our institution, were also included. The series encompassed 174 CDH1 carriers. Preoperative endoscopic biopsies were positive in 28.3%. A macroscopic lesion was apparent in 11.7% of TGs. Histopathological analysis revealed intraepithelial lesions and/or intramucosal signet ring cell carcinoma in 87.9% of TGs. When we explored the type of protocol used for handling the specimens, we found that microscopic cancer foci were detected in 95.3% of TGs when a total-embedding protocol (assessment of the totality of gastric mucosa) was applied, and only in 62.5% when no specific protocol was used (P < 0.001). Helicobacter pylori infection was found in 23.4% cases. In conclusion, a thorough histopathological examination of gastric mucosa remains the gold standard for detection of cancer foci in HDGC gastrectomy specimens, requiring experienced pathologists for an accurate diagnosis. A better understanding of the natural history of HDGC will enable better clinical management of HDGC patients, particularly regarding the optimal timing for the performance of TG.

Transcriptome profiling of cancer tissues in Chinese patients with gastric cancer by high-throughput sequencing

Gastric cancer (GC) is the fifth most common malignancy and the third leading cause of cancer-associated mortality worldwide. Therefore, there is a requirement to identify sufficiently sensitive biomarkers for GC. Genome-wide screening of transcriptome dysregulation among cancerous and normal tissues may provide insights into the underlying molecular mechanisms of GC initiation and progression. At present, high-throughput sequencing techniques have begun to innovate biomedical studies. The RNA-seq method has become an advanced approach in medical studies; it is capable of the accurate detection of gene expression levels. The present study used RNA-seq to evaluate the transcriptional changes between tumor and matched normal samples, and these changes were confirmed by differentially expressed genes in larger samples using the results of sequencing. In total, the upregulation of 28 mRNAs and downregulation of 22 mRNAs between cancerous and normal tissue samples were identified. Subsequently, five differentially expressed genes were selected to verify in large samples and cadherin-1 (CDH1) was selected to detect protein expression levels. The results revealed that CDH1, cyclooxygenase-2 and matrix metalloproteinase genes had significantly higher expression levels, whereas the expression levels of dermatopontin and transforming growth factor β receptor 2 were decreased in GC samples. In particular, CDH1 demonstrated a 36-fold higher expression level in cancer tissues. The western blotting results also revealed high CDH1 expression levels in the validation cohorts. Furthermore, these genes are highly enriched in certain gene ontology categories, including the digestive system process, secretion and digestion. The present study provided a preliminary survey of the transcriptome of Chinese patients with GC, which may improve the detection of aberrant gene expression in GC and the understanding of the mechanisms of tumorigenesis.