Association of ras p21 with differentiation of epidermal keratinocytes in proliferating skin diseases.

We examined the localization of DNA replicating cells and ras oncogene product p21 positive cells in proliferating skin diseases, such as psoriasis vulgaris, lichen planus, verruca vulgaris, verruca plana juvenilis and seborrheic keratosis. ras p21-positive cells were found rather in the differentiated layers than in the proliferating layers of the epidermis. We indicate that the expression of ras p21 can be associated with the differentiation of epidermal keratinocytes not only in tumor tissues but also in inflammatory skin disease.