Expression of proliferating cell nuclear antigen (PCNA) and apoptosis related antigen (LeY) in epithelial skin tumors.

We semiquantitatively analyzed expression of PCNA and LeY in seborrheic keratosis (SK), actinic keratosis (AK), Bowen's disease (BD), and squamous cell carcinoma (SCC), using immunocytochemically stained tissue sections. PCNA expression increased in a stepwise fashion from low levels in normal skin to higher expressions within SK, AK, BD, and SCC. The levels of LeY protein also increased in this order. The PCNA expression pattern shifted from expression limited to the basal and suprabasal cell layers (in normal skin and SK) to expression extending to the upper squamous and granular layers (in AK, BD, and SCC). On the other hand, the pattern of LeY expression shifted from the granular (in normal skin) to the upper squamous (in SK and AK) and suprabasal layers (in BD and SCC). These findings suggest that PCNA expression is related to the degree of cell proliferation and that LeY expression is related to the degree of differentiation or keratinization of tumor cells. In addition, PCNA and LeY show a reciprocal relationship in their expression.