Expression of Bax and apoptosis-related proteins in human esophageal squamous cell carcinoma including dysplasia

The rate of tumor growth depends on the balance between proliferation and d eath of tumor cells. It is known that Bax, caspase-3, and p53 proteins are death-promoting factors, whereas Bcl-2 protein is a death antagonist. We im munohistochemically examined the expression of Bax and apoptosis-related pr oteins such as caspase-3, p53, and Bcl-2 in 76 patients with human esophage al squamous cell carcinoma (SCC) including dysplasia to determine the relat ionship of expression of each protein to tumor behavior and patients' progn osis. No significant relationships in immunopositivity were found among the se proteins in SCCs. Cytoplasmic Bax expression was exhibited in 63 cases o f SCCs (82.9%). The apoptotic index of caspase-3-positive lesions was signi ficantly higher than that of caspase-3-negative lesions in both dysplasia a nd SCC (P = .016, P = .012). On die other hand, the apoptotic index (1.18%) was significantly correlated with Bax overexpression in dysplasia (P = .00 6), but not in SCC lesions (P = .129). The patients with Bax-positive SCCs were found to have a poor prognosis by the Kaplan-Meier method (P = .043). These findings suggested that Bax expressed in dysplasia may play a role as an apoptotic factor, but that it may be functionally inactive in some canc erous lesions and thus not contribute to suppression of the tumor progressi on hi some cases of human esophageal SCCs.