Expression of the apoptosis-suppressing protein Bcl-2 in non-melanoma skin cancer.

Basal cell carcinoma (BCC) is typically a slow-growing malignant tumour, composed of cells similar to those in the basal area of the epidermis. We investigated the expression of bcl-2 (B-cell leukaemia/lymphoma-2) in BCC, and also in squamous cell carcinoma (SCC) of the skin. The proto-oncogene bcl-2 encodes a protein which inhibits programmed cell death (apoptosis). The protein is expressed in basal cells in normal human epithelium, but not in the suprabasal cell layers. Immunohistochemical localization using a monoclonal anti-Bcl-2 antibody revealed bcl-2 expression in all the BCCs (15 patients). SCCs did not express bcl-2 (five patients). The positive Bcl-2 staining of BCC tumour cells supports the hypothesis that BCCs originate from the basal layer of the epidermis. The bcl-2 expression of BCC tumour cells also suggests a neoplastic transformation caused by extended cell survival rather than increased cell proliferation. This type of neoplastic growth is possibly associated with less aggressive tumour behaviour.