Alterations in the retinoblastoma pathway of cell cycle control in parathyroid tumors

Mutations in proto-oncogenes and tumor suppressor genes have been associate d with tumor development and/or progression in many neoplasms. It has been reported that parathyroid tumors have deletions affecting the retinoblastom a gene (RB), and overexpression of cyclin D1 (Cyc D1). The aim of the prese nt study was to evaluate the alterations in the components of the pRB pathw ay in parathyroid adenomas and parathyroid aggressive tumors, including pat terns of expression of pRB, Cyc D1, and p16/INK4A. Paired normal and tumor DNA from 4 parathyroid adenomas and 5 aggressive tumors were analyzed for l oss of heterozygosity (LOH) at the RE locus. The expression of pRB, Cyc D1 and p16 was studied in 4 adenomas and 5 aggressive tumors. RE LOH was found in 1 of 6 adenomas, and in 1 of 2 informative aggressive tumors. Immunohis tochemical analysis revealed undetectable PRE in 4 of 5 aggressive tumors a nd presence of pRB in all adenomas. Conversely, Cyc D1 expression was found in 3 of 4 aggressive tumors, but was undetectable in the adenomas. Express ion of p16 was identified only in one aggressive tumor. Thus, alterations i n the pRB pathway seem to prevail in the aggressive form of parathyroid neo plasms. Our results warrant further investigation of these cell cycle regul ators in order to determine their potential role as tumor markers in parath yroid tumors.