Immunohistochemical analysis of p53 protein in transplant recipients with Kaposi's sarcoma

Kaposi's sarcoma (KS) is a proliferative process of suspected viral aetiology associated with immune deficiency. In transplanted patients, lesions regress on discontinuation of immunosuppressive therapy. The purpose of this work was to analyse the expression of the p53 oncosuppressor gene product, a proliferation regulator overexpressed in both malignant and non-malignant conditions, with the aim of better qualifying KS proliferation characteristics.

We analysed p53 expression in a group of transplanted, cyclosporin A-treated, KS patients by immunohistochemistry, utilizing the DO-7 (with and without the antigen retrieval pretreatment), and the PAb 240 monoclonal anti-p53 antibodies, the latter of which is able to detect a mutated epitope, and evaluating staining intensity and localization, whether cytoplasmic or nuclear.

Seventy five percent of KS lesions from transplanted patients presented both nuclear and cytoplasmic positive p53 immunostaining with DO-7 antibody, thus demonstrating a presumably functional inactivation; one case also presented immunoreactivity with the PAb 240 antibody.

On the basis of the results obtained and in the presence of lesion regression upon immunosuppression withdrawal, it may be concluded that KS in transplanted patients can be considered a non-malignant proliferative process, and that the cytoplasmic expression of p53 may stand for a functional inactivation pattern.