The expression of phosphatase and tensin homolog (PTEN ), a tumor suppressor gene, is frequently downregulated in gastric carcinomas due to mutation, loss of heterozygosity, and promoter hypermethylation. However, it is unknown if additional mechanisms may account for the down-regulation of PTEN expression. While neuronal precursor cell-expressed developmentally down-regulated 4-1 (NEDD4-1) is believed to be a potential dual regulator of PTEN, there are conflicting reports regarding their interaction. To gain further insight into the role of NEDD4-1 and its association with PTEN in gastric carcinoma development, we measured the protein expression of NEDD4-1 and PTEN in gastric mucosae with various pathological lesions and found that NEDD4-1 increased from normal gastric mucosa to intestinal metaplasia and decreased from dysplasia to gastric carcinoma. These changes did not correlate with PTEN expression changes during gastric carcinogenesis. Moreover, we found similar results in protein levels in the primary tumors and adjacent non-tumorous tissues. These results differ from a previous report showing that expression of NEDD4-1 is up-regulated in gastric carcinomas, and show a more complex pattern of NEDD4-1 gene expression during gastric carcinogenesis. The expression of phosphatase and tensin homolog (PTEN), a tumor suppressor gene, is frequently downregulated in gastric carcinomas due to mutation, loss of heterozygosity, and promoter hypermethylation. However, it is unknown if additional mechanisms may account for the down-regulation of PTEN expression. While neuronal precursor cell-expressed developmentally down-regulated 4-1 (NEDD4-1) is believed to be a potential dual regulator of PTEN, there are conflicting reports regarding their interaction. To gain further insight into the role of NEDD4- 1 and its association with PTEN in gastric carcinoma development, we measured the protein expression of NEDD4-1 and PTEN in gastric mucosae with various pathological lesions and found that NEDD4-1 increased from normal gastric mucosa to intestinal metaplasia and decreased from dysplasia to gastric carcinoma These changes did not correlate with PTEN expression changes during gastric carcinogenesis. Moreover, we found similar results in protei n levels in the primary tumors and adjacent non-tumorous tissues. These results differ from a previous report showing that expression of NEDD4-1 is up-regulated in gastric carcinomas, and show a more complex pattern of NEDD4-1 gene expression during gastric carcinogenesis .