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

The retinoblastoma gene (RB) is a typical tumor-suppressor gene. Inactivation of RB has been shown in a variety of human cancers, including esophageal squamous-cell carcinomas. In the present study, samples of normal esophageal squamous epithelium (n = 10), severe squamous-cell dysplasias (n = 19), carcinomas in situ (n = 14), invasive squamous-cell carcinomas (n = 172), and 2 continuous esophageal-carcinoma cell lines were immunohistochemically analyzed for pRb expression. The specificity of immunostaining was tested by Western-blot analysis of pRb expression in the cell lines. In normal esophageal epithelium, nuclear pRb expression was restricted to the parabasal cell layer, whereas, in a considerable portion of severe dysplasias and carcinomas in situ, 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 was not correlated with pT category, pN category or tumor grade. In the univariate survival analysis, patients with pRb-negative tumors showed lower 2-year 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 detected by immunohistochemistry in a high percentage of squamous-cell carcinomas of the esophagus and its precursor lesions. However, expression of the pRb protein has no significant impact on the prognosis. Int. J. Cancer (Pred. Oncol.) 84:618-622, 1999.