EXPRESSION OF NUCLEOPHOSMIN B23 IN NORMAL AND NEOPLASTIC COLORECTAL MUCOSA/

Nucleophosmin/B23 is a 38 kD molecular phosphoprotein involved in ribo some assembly and transport, In view of the fact that nucleophosmin/B2 3 appears to be more abundant in tumour cells than in normal cells, th e mRNA expression and immunohistochemical localization of nucleophosmi n/B23 were investigated in 19 samples of non-neoplastic mucosa, six ad enomas, and 16 adenocarcinomas of the colorectum. Northern blot analys is revealed that nucleophosmin/B23 mRNA is expressed at a higher level in adenomas and carcinomas than in non-neoplastic mucosa of the color ectum, Immunohistochemical staining of formalin-fixed, paraffin-embedd ed tissue sections after microwave antigen retrieval, using a nucleoph osmin/B23-specific monoclonal antibody, showed almost exclusively diff use nuclear reactivity of a majority of the epithelial cells in non-ne oplastic mucosa: in adenomas, reactivity was almost exclusively nucleo lar and in carcinomas, nuclear as well as nucleolar staining was obser ved, During mitosis, the immunoreactivity of nucleophosmin/B23 appears in the cytoplasm, The results indicate that the expression of nucleop hosmin/B23 is higher in neoplastic than in non-neoplastic colorectal m ucosa, Furthermore, the pattern of nucleophosmin/B23 expression shifts from nuclear to nucleolar early in the adenoma-carcinoma sequence, Th e exact function of nucleophosmin/B23 in colorectal carcinogenesis rem ains to be determined.