Retinoblastoma-protein (pRb) expression and prognosis in squamous-cell carcinomas of the esophagus

The retinoblastoma gene (RB) is a typical tumor-suppressor gene. Inactivati on of RB has been shown in a variety of human cancers, including esophageal squamous-cell carcinomas. In the present study, samples of normal esophage al squamous epithelium (n = 10), severe squamous-cell dysplasias (n = 19), carcinomas in situ (n = 14), invasive squamous-cell carcinomas (n = 172), a nd 2 continuous esophageal-carcinoma cell lines were immunohistochemically analyzed for pRb expression. The specificity of immunostaining was tested b y Western blot analysis of pRb expression in the cell lines. In normal esop hageal epithelium, nuclear pRb expression was restricted to the parabasal c ell layer, whereas, in a considerable portion of severe dysplasias and carc inomas in site, pRb over expression was found. Among carcinomas, 161 of 172 cases showed pRb expression, as did the 2 esophageal-carcinoma cell lines, whereas 11 carcinomas were negative. Expression of pRb among carcinomas wa s not correlated with pT category, pN category or tumor grade. In the univa riate survival analysis, patients with pRb negative tumors showed lower 2-y ear and 5-year survival rates (27.3%/9.1%) than patients with pRb-positive tumors (42.8%/25.8%; not significant). In conclusion, pRb protein can be de tected by immunohistochemistry in a high percentage of squamous-cell carcin omas of the esophagus and its precursor lesions. However, expression of the pRb protein has no significant impact on the prognosis. Int. J. Cancer (Pr ed, Oncol.) 84:618-622, 1999. (C) 1999 Wiley-Liss, Inc.