Reduced expression of p16 and p27 proteins in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignant tumor with a high incidence i n east Asian countries. Inactivation of cyclin-dependent kinase (CDK) inhib itors (CKIs) and overexpression of G(1) cyclin has been thought to be impor tant for tumor development. To determine whether reduction of CKI (p16 and p27) expression was associated with NPC development, we performed immunohis tochemical staining of NPC specimens from 20 patients. We found that p16 an d p27 proteins were negative in 8 of 20 and 16 of 20 cases, respectively; t hat either p16 or p27 proteins were negative in 17 of 20; and that both p16 and p27 were negative in 7 of 20. Excepting the cases in which both CKIs w ere negative, negativity of p27 alone was statistically higher than that of p16 (9/20 versus 1/20, P = .022), suggesting that the reduction of p27 pro tein is an important event for the multi-step process of NPC development.