Fas and WAF1 expression in esophageal squamous cell carcinomas.

The Fas/FasL system plays an important role in the regulation of tumor apoptosis. This study examined the correlation between the expression levels of Fas and WAF1 with the clinicopathological characteristics of esophageal squamous cell carcinoma (SCC) tumors. Paraffin-embedded sections from 19 surgically resected primary esophageal squamous cell carcinomas were examined by immunohistochemistry. At low expression levels (5% to 24%), a 4-fold higher expression of Fas relative to WAF1 expression was observed. High expression levels (50% to 74%) of Fas were not recorded, whereas such levels of expression for WAF1 were retained in a proportion of cells >20%. Proteins WAF1 and Fas were both expressed in all lesions of SCCs. Lesions showing high expression levels of WAF1 have a high degree of differentiation, but a sample that expresses WAF1 and belongs to the morphology I category probably has a medium degree of differentiation.