EXPRESSION OF THE BCL-2 HOMOLOG BAX IN NORMAL HUMAN SKIN, PSORIASIS-VULGARIS AND NONMELANOMA SKIN CANCERS

Bax (bcl-2-associated X protein) is a recently identified member of th e bcl-2 family and one of the principal inducers of apoptosis. We exam ined the distribution of Bax protein in normal human skin and several skin diseases by immunohistochemistry. Bax immunoreactivity was presen t in normal epidermis and its appendages, with the suprabasal compartm ent being stained more strongly than basal keratinocytes. Bax immunost aining was also detected in the epidermis of psoriasis vulgaris and 5 keratoacanthomas examined. We could observe only weak Bax immunoreacti vity in 15 squamous cell carcinomas examined, with the exception of we ll-differentiated tumour islands in two tumours, which expressed immun ostaining for Bax comparable to that of normal suprabasal epidermis, I mmunostaining for Bax was negative in 12 out of 17 basal cell carcinom as and the remaining five tumours showed weak Bax reactivity in tumour cells scattered within tumour masses and in palisading layers of some tumour formations. Western blot analysis confirmed the expression of Bax protein in normal skin, psoriasis vulgaris and squamous cell carci noma as well as the absence of Bax in basal cell carcinoma. Our findin gs suggest that the loss of pro-apoptotic Bax protein in basal cell ca rcinoma and its reduced expression in squamous cell carcinoma might be an important step in the development of these two skin cancers.