Recently, the succinate dehydrogenase subunit B gene, SDHB, has emerged as a novel tumor suppressor. In this study, we have examined the genetic and epigenetic alterations of the SDHB gene in sporadic gastric adenocarcinomas in order to investigate if the SDHB gene is involved in gastric carcinogenesis. The expression of SDHB proteins was also examined with immunohistochemistry and Western blot in 184 and eight gastric cancers, respectively. There was loss or reduced expression of SDHB in 45 (24.5%) of the 184 gastric cancers. Statistically, altered expression of SDHB was not associated with clinicopathological parameters, including tumor differentiation, location, depth of invasion, and lymph node metastasis (P > 0.05). Western blot analysis showed a reduced expression of SDHB in four (50.0%) of the eight paired gastric cancer tissues. Genetic analysis showed one missense mutation, GCC --> ACC (Ala --> Thr) at codon 29. In addition, promoter hypermethylation was not detected in the gastric cancer samples. This is the first investigation of the genetic and protein expression analysis of the SDHB gene in gastric cancers. Our results suggest that genetic, epigenetic, and protein expression pattern alterations of the SDHB gene might play a minor role in the development or progression of gastric cancers.

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