Immunohistochemical characterization of p57(KIP2) expression in human esophageal squamous cell carcinoma

Functional defects in the CIP/KIP family of cyclin-dependent kinase inhibit ors (CDKIs) have been shown to be associated with human malignancies. We im munohistochemically examined p57KIP2 (p57) expression in 92 patients with h uman esophageal squamous cell carcinoma (SCC) to determine the relationship between this expression and those of cyclin D1 and E. The p57 labeling ind ex (LI) (defined as the percentage of p57-positive cells) in esophageal SCC ; was 43.3 +/- 3.2 % (mean +/- standard error of the mean). In non-neoplast ic esophageal epithelium, p57 staining was more frequently observed in the basal and parabasal cells than in surface layer cells. Immunostaining for c yclin DI and E was observed in 28.2% (28/92) and 32.6% (30/92) of tumors, r espectively The median p57 LI in cyclin D1- positive cases was 66.2, and si gnificantly higher than that in negative cases (31.9%) (p=0.0009). There wa s no significant relationship between p57 LI and cyclin E expression (p=0.1 47). As determined using Kaplan-Meier's method, loss of p57 immunoreactivit y was not a prognostic factor for esophageal SCC (p=0.548). Our in vivo fin dings suggested that p57 protein expression was positively correlated with cyclin D1 expression and that loss of p57 protein expression alone does not affect progression of esophageal SCC.