ABERRANT BCL-2 PROTEIN EXPRESSION PROVIDES A POSSIBLE MECHANISM OF NEOPLASTIC CELL-GROWTH IN CUTANEOUS BASAL-CELL CARCINOMA

The bcl-2 proto-oncogene encodes a protein that protects cells from programmed cell death (apoptosis). High levels of this protein confer a growth advantage to neoplastic cells even in the absence of a high mitotic rate. This gene is involved in the interchromosomal 14;18 translocation, an abnormality present in more than two-thirds of follicular lymphomas and in about 25% of other non-Hodgkin's lymphomas of the lymph nodes. A recent study also demonstrated the presence of high levels of bcl-2 protein in solid tumors such as squamous cell carcinomas of the lung and related it to a better prognosis. We analyzed bcl-2 protein expression in 20 cases each of basal- and squamous-cell carcinoma and in 5 biopsy specimens of normal skin, using a monoclonal anti-bcl-2 protein antibody with a standard 3-step immunoperoxidase technique on routinely fixed, paraffin-embedded tissue sections. Normal skin showed positive staining of the majority of keratinocytes in the epidermal basal layer. Bcl-2 positivity was also observed within the outer root sheath and the mesenchymal cells of the follicular papillae, the clear cells of the eccrine glands, and in some melanocytes at the dermo-epidermal junction. Neoplastic cells in all cases of basal-cell carcinoma showed a positive cytoplasmic reaction for bcl-2. All biopsy specimens of squamous-cell carcinoma were negative. Expression of bcl-2 protein could also be observed in the majority of peri- and intratumoral lymphocytes in both basal-cell carcinoma and squamous-cell carcinoma. Our results indicate that protection from apoptosis mediated by bcl-2 protein may be involved in the neoplastic growth mechanism of basal-cell carcinoma. Further studies are required to detect the molecular basis of bcl-2 protein overexpression in these tumors.