OVEREXPRESSION OF THE P53 TUMOR-SUPPRESSOR GENE-PRODUCT IN ESOPHAGEALAND GASTRIC CARCINOMAS

Purpose. p53 protein has been reported as frequently overexpressed in esophageal and gastric carcinomas. However, the correlation between p5 3 protein expression and clinico-pathological features of the turners is debated in this heterogeneous group Of cancers. The aim of this stu dy was to establish the prevalence of p53 protein overexpression in a series of resected esophageal squamous carcinomas (n = 78), adenocarci nomas developed on Barrett's esophagus (n = 20), adenocarcinomas of th e cardia (n = 36), and adenocarcinomas of the antrum (n = 30), and to correlate this expression with the clinico-pathological and flow-cytom etric characteristics of the tumors. Methods. Immunohistochemical stai ning was performed on frozen sections with a monoclonal antibody direc ted against wild type and mutated p53 protein (Pab 1801). An adjacent frozen specimen was used for flow cytometric determination of the DNA- ploidy and S phase fraction. Results. p53 protein nuclear expression w as detected in 76% of esophageal squamous carcinomas, in 75% of adenoc arcinomas developed in Barretts esophagus, in 56% of adenocarcinomas o f the cardia, and in 27% of adenocarcinomas of the antrum. Only the nu mber of positive adenocarcinomas of the antrum was significantly lower when compared to the other three types of tumors (p = 0.001). No sign ificant correlation was observed between p53 protein expression and mo st of the clinicopathological and flow-cytometric parameters (sex, age , tobacco smoking, chronic alcohol consumption, size of the tumor, gra de of differentiation, depth of infiltration, presence of lymph node m etastases, UICC stage, DNA-ploidy, S phase fraction). p53 protein expr ession was more frequent in Lauren's intestinal adenocarcinomas (67%) when compared to the diffuse type tumors (24%) (p = 0.002). Conclusion s. Our results confirm that overexpression of p53 protein is a common feature of esophageal and gastric carcinomas. The high prevalence of p 53 protein overexpression found in cardiac adenocarcinoma when compare d to antral adenocarcinoma reinforces the hypothesis of distinct carci nogenetic mechanisms in these two cancers. In particular the lack of c orrelation between p53 expression arid tumor stage suggests that p53 p rotein overexpression is an early event in these tumors.