OVEREXPRESSION OF P53 TUMOR-SUPPRESSOR PROTEIN IN POROKERATOSIS

Background: p53 is a tumor suppressor nucleoprotein. Mutations of the p53 gene have been found in a variety of malignant neoplasms. Wild-typ e p53 has a short half-life, possibly only 20 to 30 minutes, and is no t present in the nucleus at levels that are detectable with routine im munohistochemical techniques. Mutant p53 has a longer half-life, and i s readily detectable with immunoperoxidase staining. Results: We studi ed 17 specimens from patients with either porokeratosis of Mibelli or actinic porokeratosis, using immunoperoxidase staining with an antibod y directed against the p53. There was staining of lesional keratinocyt e nuclei in 16 of 17 specimens, limited in most cases to the zone betw een carnoid lamellae. Staining for proliferating cell nuclear antigen was increased above background levels in only six of 13 specimens. Con clusions: The finding of p53 immunoperoxidase staining in porokeratosi s suggests genetic mutation, as occurs in other cutaneous keratinocyti c neoplasms, and the lack of corresponding proliferating cell nuclear antigen expression in many specimens indicates that p53 overexpression is not simply a reflection of increased cellular proliferation.