IMMUNOHISTOCHEMICAL DETECTION OF NUCLEOLAR PROTEIN P120 IN PARAFFIN-EMBEDDED TISSUES

The monoclonal antibody FB-2 recognizes the antigen p120-kDa protein ( p120), associated with the nucleolar matrix. p120 has originally been reported as expressed and detectable in malignant and non-neoplastic p roliferating cells, but not in most normal resting tissues and benign tumours. In the present study, a reliable immunostaining method was us ed to detect p120 on formalin-fixed, paraffin wax-embedded tissue, tes ting it on 148 samples from different neoplastic and non-neoplastic ti ssues from different organs (breast, colon, lung, prostate, bladder, l ymph nodes, skin, tongue and liver). The immunostaining was performed after the application of a specific antigen-unmasking protocol based o n six consecutive cycles of microwave oven heating. Under these retrie val conditions, p120 antigen was clearly detectable, not only in hyper plastic and malignant cells, but also in stromal and normal non-prolif erating cells of all the tissues evaluated. Our results show that the nucleolar protein p120 can be detected by routine immunohistochemistry in formalin-fixed, paraffin-embedded tissue and is expressed in all n ucleated cells under any biological condition.