Oral squamous cell carcinoma (OSCC) is amenable to pathogenetic examination because the regions surrounding primary tumors (adjacent mucosa) and even distant oral mucosa of the cancer patients often are characterized by foci of dysplasia, carcinoma in situ, and/or OSCC. The Principal Investigator and others have observed frequent alterations in chromosomal band 9p21, including p16/CDKN2 gene alterations, in OSCC and other squamous cell carcinomas of the head and neck by cytogenetic and molecular genetic analysis. The p16 gene (CDKN2) encodes a G1 cyclin- dependent kinase inhibitor which regulates cell cycle progression in eukaryotes. Inactivation would lead to loss of an early cell cycle checkpoint with subsequent loss of regulation of cellular proliferation. 9p21 is unusual in its high frequency of homozygous deletion (as opposed to mutation and/or loss of heterozygosity [LOH]). Coordinated inactivation of CDKN2 and a cassette of flanking genes by deletion or methylation may be unique to this region, and may play a significant role in the pathogenesis of OSCC. The Principal investigator and her colleagues propose to test the hypothesis that genetic (and/or epigenetic) alterations in 9p21 are early events in oral carcinogenesis, and serve as useful markers for the early detection of cancer. They propose to do so through a systematic hierarchical analysis of 9p21 alterations. This research group will analyze OSCC, adjacent oral mucosa which has a high likelihood of dysplasia), and contralateral oral mucosa which is also at risk) from OSCC patients undergoing surgical resection at the University of Pittsburgh affiliated hospitals using the following techniques: 1) fluorescence in situ hybridization (FISH) to determine 9p21 copy number and identify deletions on a cell by cell basis using a p16 probe, 2) LOH for microsatellite repeats within and around the p16 gene, 3)mutational analysis of CDKN2, 4) characterization of the methylation pattern of the p16 gene, and 5) examination of the p16 expression pattern in tumor sections by immunocytochemistry. This prospective, targeted transnational genetic investigation will explore the relationship between specific 9p21 alterations and personal and clinical characteristics and should lead to a better understanding of the biology of oral cancer. The results are expected to provide a firm foundation for multicenter studies aimed at confirming the utility of these genes as markers of disease risk, unrecognized early disease and/or prognosis.
