α-catenin expression is decreased in human gastric cancers and in the gastric mucosa of first degree relatives

Background and aims-The role of altered cell adhesion is critical for the development of epithelial cancers. E-cadherin plays an important role in the maintenance of cell-cell adhesion and its function is thought to be regulated by its associated cytoplasmic proteins, such as alpha-catenin and beta-catenin. To determine the role of alpha-catenin expression in gastric carcinogenesis, we studied its expression in human gastric cancer and in the gastric mucosa of first degree relatives with no clinical disease. Methods-alpha-Catenin expression was assessed by immunohistochemical analysis and reverse transcriptase-polymerase chain reaction (RT-PCR) using gastric tissue specimens from patients with gastric cancer and from the gastric mucosa of first degree relatives of gastric cancer patients and healthy controls. Results-mRNA levels of alpha-catenin were reduced or absent in 13 of 19 gastric cancer tissues, which differed significantly from levels found in the tumour free gastric mucosa of cancer patients (p<0.05). Of the cancer samples with altered alpha-catenin mRNA levels, alpha-catenin expression was negative in seven and decreased in six cases. Interestingly, decreased alpha-catenin mRNA expression also occurred in the mucosa of the corpus (11/18) and antrum (4/18) of first degree relatives. In the corpus biopsies alpha-catenin expression was more often decreased or lost compared with the antrum biopsies in first degree relatives and healthy controls (p<0.05). Immunohistochemical analysis revealed membranous expression of alpha-catenin in gastric cancer cells and the non-malignant gastric epithelium. However, some cancers also exhibited loss of membranous staining. Generally, loss or downregulation of alpha-catenin mRNA in the gastric mucosa was associated with Helicobacter pylori infection (p<0.05). Conclusion-Our findings suggest that loss or downregulation of alpha-catenin expression may be an early event in gastric carcinogenesis and may be associated with H pylori infection.