PTEN/MMAC1 expression in esophageal squamous cell carcinomas

The PTEN/MMAC1 gene at 10q23.3 is a novel tumor suppressor gene candidate. Various kinds of tumors have mutations in this gene. However, in some cance rs PTEN/MMAC1 gene may be inactivated by mechanisms other than gene deletio n and mutation, including promoter methylation or translational modificatio n. The aim of this study was to determine whether there are abnormalities i n the expression of PTEN/MMAC1 gene in esophageal cancer. Reverse transcrip tion polymerase chain reaction and Western blot were used to examine PTEN/M MAC1 expression in human esophageal squamous cell lines and normal cultured esophageal epithelial cells. Immunohistochemical staining was carried out to detect PTEN/MMAC1 expression in surgically resected esophageal squamous cell carcinomas and normal esophageal epithelium. All 30 esophageal cancer cell lines (KYSE series) and normal cultured esophageal epithelial cells ex pressed PTEN/MMAC1 mRNA. Western blot analysis confirmed that all the cell lines expressed PTEN/MMAC1 protein and there was no difference in expressio n level. Immunohistochemical study showed that the PTEN/MMAC1 protein was l ocalized dominantly in the cytoplasm and strongly stained in all 42 surgica lly resected esophageal squamous cell carcinomas and normal esophageal epit helium. PTEN/MMAC1 is rarely associated with esophageal squamous cell carci noma carcinogenesis.