MN ANTIGEN EXPRESSION IN NORMAL, PRENEOPLASTIC, AND NEOPLASTIC ESOPHAGUS - A CLINICOPATHOLOGICAL STUDY OF A NEW CANCER-ASSOCIATED BIOMARKER

Recently, a novel tumor-associated protein, termed MN, has been descri bed in carcinomas of the uterine cervix, where its expression has been shown to be associated with malignant transformation. Because maligna nt transformation in the esophagus develops through a dysplasia-carcin oma sequence similar to that which occurs in the cervix, this study wa s performed to evaluate MN expression in normal, preneoplastic, and ne oplastic tissues of the esophagus. Esophageal tumor resection specimen s from 27 patients (12 squamous cell carcinomas, one multifocal squamo us dysplasia, 10 Barrett's-associated adenocarcinomas, two Barrett's e sophagus with dysplasia, two adenosquamous carcinomas) were immunohist ochemically stained with a monoclonal antibody (clone M75) directed ag ainst the MN antigen. The localization of MN antigen, as well as the p roportion of positively stained cells, were determined in sections of normal, dysplastic, and carcinomatous tissues, The staining characteri stics were correlated with the pathological features of the tumors. We ak intracellular MN expression was detected only in the basal cells of normal squamous epithelium, However, inflamed and reactive squamous e pithelium showed increased staining in the basal layer and in the over lying mature squamous cells. MN expression was significantly increased in dysplastic squamous epithelium (P < .001). All esophageal squamous cell carcinomas (100%) stained positively for MN antigen, where the p attern of staining was predominantly membranous. However, the degree o f MN staining did not correlate with any of the pathological features of the tumors. In Barrett's epithelium, MN stained positively in all t ypes of metaplastic cells and showed no difference in dysplastic epith elium. in contrast to squamous cell carcinomas, only 80% of esophageal adenocarcinomas were positive for MN, but the degree of MN expression was inversely correlated with histological tumor differentiation (P < .015). The results of this study suggest that (1) the tumor-associate d MN antigen may play a role in proliferation and regeneration in esop hageal squamous epithelium, and (2) loss of MN expression may be relat ed to cancer progression in Barrett's-associated adenocarcinomas. Copy right (C) 1997 by W.B. Saunders Company.