Altered expression of the cyclin D1 and retinoblastoma genes in human esophageal cancer

DNA from four human esophageal carcinoma cell lines and 50 primary esophageal carcinomas, taken from various countries for expansion of the cyclin D1 gene, were examined. About 36 of the 50 carcinomas were examined by immunohistochemistry for cyclin D1 and retinoblastoma (RB) protein expression. Approximately 16 tumors and 2 cell lines exhibited a three to ten fold expansion in cyclin D1 gene. During evolution of tumors through reduced RB gene expression or through enhanced cyclin D1 gene expression, the restrictive influence of RB on cell cycle development can be removed.