Expression of p16, Rb, and cyclin D1 gene products in oral and laryngeal squamous carcinoma: Biological and clinical implications

Cyclin D1, p16, and Rb genes play a critical role in the regulation of the G1-S transition of the cell cycle and are frequently altered in several neo plastic entities. Analysis of the protein products of these genes by molecu lar and immunohistochemical methods provides information on their functiona l status and allows for the phenotypic evaluation of tumor cells. We perfor med Western blotting and immunohistochemical analysis on tissues from 35 pr imary oral and laryngeal squamous carcinoma specimens with previous molecul ar analysis of the p16 gene and correlated the results with relevant clinic opathologic factors. Our study shows significant concordance between Wester n blotting and immunostaining results for cyclin D1 (P = .01), p16 proteins (P = .01), and Rb (P = .04). Heterogeneous staining of tumor cells and the positivity of non-neoplastic host elements for Rb by immunohistochemistry contributed to the discrepancy noted in some tumors by Western blotting. Si gnificant reciprocal relationship between p16 and Rb proteins was observed (P < .001); in most turners, absence of p16 (89%) and detectable Rb (94%) p roteins were found. Two tumors had negative cyclin D1 expression, and one t hird overexpressed this protein. There was a lack of correlation between cy clin D1 overexpression and the clinicopathologic factors studied. Om result s indicate that the absence of p16 in most of these tumors may constitute a n early tumorigenic event and that the loss of the Rb function plays a mino r role in HNSC. HUM PATHOL 30:1013-1018. Copyright (C) 1999 by WB. Saunders Company.