Bcl-2 but not Bax expression is associated with apoptosis in normal and transformed squamous epithelium.

Aberrant regulation of apoptosis may contribute to tumorigenesis. Relative levels of apoptosis regulatory proteins, such as Bcl-2 and Bax as well as interactions of these proteins with other gene products, may contribute to the rate of apoptosis in neoplasia. We examined Bcl-2 expression in 104 squamous cell carcinomas of the head and neck, as well as histologically normal mucosa several centimeters away from the tumor, and in control normal mucosa from patients without cancer. Immunohistochemistry and immunoblotting demonstrated Bcl-2 expression in 30% (31 of 104) of squamous cell carcinoma, with an increase in Bcl-2 protein levels compared with control normal mucosa from noncancer patients. Bcl-2-positive tumors demonstrated a 5-fold decrease in the number of apoptotic cells compared with Bcl-2-negative tumors. Bcl-2 protein expression was associated with poorly differentiated tumor grade but was not correlated with Bax expression or patient survival. These findings demonstrate that Bcl-2 contributes to apoptosis in normal and transformed squamous epithelium.