Lyn activity protects mice from DSS colitis and regulates the production of IL-22 from innate lymphoid cells

Intestinal homeostasis requires a complex balance of interactions between diverse resident microbial communities, the intestinal epithelium, and the underlying immune system. We show that the Lyn tyrosine kinase, a critical regulator of immune cell function and pattern-recognition receptor (PRR) responses, has a key role in controlling gastrointestinal inflammation. Lyn⁻/⁻ mice were highly susceptible to dextran sulfate sodium (DSS)-induced colitis, whereas Lyn gain-of-function (Lyn(up)) mice exhibited attenuated colitis during acute and chronic models of disease. Lyn(up) mice were hypersensitive to lipopolysaccharide (LPS), driving enhanced production of cytokines and factors associated with intestinal barrier function, including interleukin (IL)-22. Oral administration of LPS was sufficient to protect antibiotic-treated Lyn(up) but not wild-type mice from DSS, highlighting how Lyn-dependent changes in the nature/magnitude of PRR responses can impact intestinal health. Furthermore, protection from DSS-induced colitis and increased IL-22 production in response to LPS did not depend on the adaptive immune system, with increased innate lymphoid cell-derived IL-22 correlating with Lyn activity in dendritic cells. These data reveal a key role for Lyn in the regulation of innate immune responses and control of intestinal inflammation.

CDH1/E-cadherin germline mutations in early-onset gastric cancer

BACKGROUND

Gastric cancer remains a leading cause of cancer deaths worldwide. Genetic factors, including germline mutations in E-cadherin (CDH1, MIM#192090) in hereditary diffuse gastric cancer (HDGC, MIM#137215), are implicated in this disease. Family studies have reported CDH1 germline mutations in HDGC but the role of CDH1 germline mutations in the general population remains unclear.

AIMS

To examine the frequency of CDH1 germline mutations in a population-based series of early-onset gastric cancer (EOGC <50 years old).

METHODS

211 cases of EOGC were identified in Central-East Ontario region from 1989 to 1993, with archival material and histological confirmation of non-intestinal type gastric cancer available for 81 subjects. Eligible cases were analysed for CDH1 germline mutations by single-strand conformation polymorphism, variants were sequenced, and tumours from cases with functional mutations were stained for E-cadherin (HECD-1) using immunohistochemistry.

RESULTS

1155 (89%) of 1296 polymerase chain reactions amplified successfully. One new germline deletion (nt41delT) was identified in a 30-year-old patient with isolated cell gastric cancer. The overall frequency of germline CDH1 mutations was 1.3% (1/81) for EOGC and 2.8% (1/36) for early-onset isolated cell gastric cancer.

CONCLUSION

This is the first population-based study, in a low-incidence region, of genetic predisposition to gastric cancer. Combined with our previous report of germline hMLH1 mutations in two other subjects from this series, it is suggested that 2-3% of EOCG cases in North Americans may be owing to high-risk genetic mutations. These data should inform cancer geneticists on the utility of searching for specific genetic mutations in EOGC.