Overexpression of p27^BBP in head and neck carcinomas and their lymph node metastases

Background. p27^BBP is a regulator of ribosome assembly and an essential nuclear and cytoplasmic component of eukaryotes. Methods. We investigated the immunochemical distribution of p27^BBP in head and neck carcinomas, in the associated normal mucosa, and in regional lymph nodes. Results. p27^BBP is detectable in mucosal cells but is overexpressed in carcinomas, highly concentrated in large polymorphous nucleoli, and even larger and more evident in lymph node metastatic foci. Western blotting confirms increased p27^BBP in carcinomas versus normal mucosa and also in metastatic versus normal lymph nodes. The overexpression of p27 ^BBP corresponds to mRNA upregulation in carcinomas. Unexpectedly, a 52-kDa band specifically reacting with antibodies to p27^BBP was observed in several carcinomas. Conclusions. p27^BBP alterations are common events in the transition to malignancy and are probably involved in squamous carcinoma progression. Immune reagents raised to p27^BBP may provide additional diagnostic tools for surgical pathology of tumor boundaries and lymph nodes. The 52-kDa band may represent an abnormal form of p27 ^BBP expressed by transformed airway epithelia.