Early-onset Diffuse Gastric Cancer Research Articles

Characterization of a Recurrent Germ Line Mutation of the E-Cadherin Gene: Implications for Genetic Testing and Clinical Management

To identify germ line CDH1 mutations in hereditary diffuse gastric cancer (HDGC) families and develop guidelines for management of at risk individuals. We ascertained 31 HDGC previously unreported families, including 10 isolated early-onset diffuse gastric cancer (DGC) cases. Screening for CDH1 germ line mutations was done by denaturing high-performance liquid chromatography and automated DNA sequencing. We identified eight inactivating and one missense CDH1 germ line mutation. The missense mutation conferred in vitro loss of protein function. Two families had the previously described 1003C>T nonsense mutation. Haplotype analysis revealed this to be a recurrent and not a founder mutation. Thirty-six percent (5 of 14) of the families with a documented DGC diagnosed before the age of 50 and other cases of gastric cancer carried CDH1 germ line mutations. Two of 10 isolated cases of DGC in individuals ages <35 years harbored CDH1 germ line mutations. One mutation positive family was ascertained through a family history of lobular breast cancer (LBC) and another through an individual with both DGC and LBC. Occult DGC was identified in five of six prophylactic gastrectomies done on asymptomatic, endoscopically negative 1003C>T mutation carriers. In addition to families with a strong history of early-onset DGC, CDH1 mutation screening should be offered to isolated cases of DGC in individuals ages <35 years and for families with multiple cases of LBC, with any history of DGC or unspecified GI malignancies. Prophylactic gastrectomy is potentially a lifesaving procedure and clinical breast screening is recommended for asymptomatic mutation carriers.

Genetic Screening for Familial Gastric Cancer

Approximately 10% of gastric cancer cases show familial clustering but only 1-3% of gastric carcinomas arise as a result of inherited gastric cancer predisposition syndromes. Direct proof that Hereditary Gastric Cancer a genetic disease with a germline gene defect has come from the demonstration of co-segregation of germline E-cadherin (CDH1) mutations with early onset diffuse gastric cancer in families with an autosomal dominant pattern of inheritance (HDGC). E-cadherin is a transmembrane calcium-dependent cell-adhesion molecule involved in cell-junction formation and the maintenance of epithelial integrity. In this review, we describe frequency and type of CDH1 mutations in sporadic and familial gastric cancer. Further we demonstrate the functional significance of some CDH1 germline missense mutations found in HDGC. We also discuss the CDH1 polymorphisms that have been associated to gastric cancer. We report other types of malignancies associated to HDGC, besides diffuse gastric cancer. Moreover, we review the data available on putative alternative candidate genes screened in familial gastric cancer. Finally, we briefly discuss the role of low-penetrance genes and Helicobacter pylori in gastric cancer. This knowledge is a fundamental step towards accurate genetic counselling, in which a highly specialised pre-symptomatic therapeutic intervention should be offered.

Mutations of the human E-cadherin (CDH1) gene.

The cell-cell adhesion molecule E-cadherin is well known to act as a strong invasion suppressor in experimental tumor cell systems. Frequent inactivating mutations have been identified for the E-cadherin gene (CDH1) in diffuse gastric cancers and lobular breast cancers. To date, 69 somatic mutations have been reported comprising, in addition to few missense mutations, mainly splice site mutations and truncation mutations caused by insertions, deletions, and nonsense mutations. Interestingly, there is a major difference in mutation type between diffuse gastric and infiltrative lobular breast cancers. In diffuse gastric tumors, the predominant defects are exon skippings, which cause in-frame deletions. By contrast, most mutations found in infiltrating lobular breast cancers are out-of-frame mutations, which are predicted to yield secreted truncated E-cadherin fragments. In most cases, these mutations do occur in combination with loss of heterozygosity (LOH) of the wild-type allele. Inactivating germline mutations of E-cadherin were recently reported for families with early-onset diffuse gastric cancer. Also, at the early stages of sporadic lobular breast and diffuse gastric cancers, E-cadherin mutations were detected, suggesting loss of growth control by such mutations and defining E-cadherin as a true tumor suppressor for these particular tumor types.