Immunohistochemical detection of p21WAF1/CIP1 and p53 proteins in formalin-fixed paraffin-embedded tissue sections of squamous cell carcinoma of the skin.

Thirty-two cases of squamous cell carcinoma (SCC) of the skin were investigated as to the expression of p53 and p21 (WAF1/CIP1) using an immunohistochemical method. These cases were surgically resected or biopsied, tissue samples were then fixed in formalin and embedded in paraffin in the conventional way. Microwave heating was used for antigen retrieval. The primary monoclonal anti-p21 antibody and the monoclonal antibody against p53 were employed. The labeled-streptoavidin-biotin-peroxidase method was used for immunohistochemical staining. Of these, 30 cases showed overexpression of p53 staining, but normal epidermal cells were free of stain. p21 positive cells were detected faintly in the middle layer cells of normal epidermis. Of these, 30 cases showed overexpression of p21 staining. The staining pattern of p53 and p21 showed intratumoral heterogeneity in SCC. In general, there was the inverse relationship between p21 and p53 staining in tumors, namely p53 positive cells were p21 negative and vice versa. However, some of the tumor cells expressed both genes simultaneously. This study supports a hypothesis that p21 expression is regulated by p53, and that it is also regulated by an additional pathway(s) in SCC.