Assessing the contribution of HRPT2 to the pathogenesis of jaw fibrous dysplasia, ossifying fibroma, and osteosarcoma.

Objective To investigate HRPT2 in jaw ossifying fibroma (OF), fibrous dysplasia (FD), and osteosarcoma (OS). Study Design We combined microsatellite loss of heterozygosity (LOH), HRPT2 sequence alterations at the mRNA level by reverse-transcription polymerase chain reaction (PCR), cDNA sequencing, and quantitative PCR (qPCR) and immunohistochemistry (IHC) in a total of 19 OF, 15 FD, and 9 OS. Because HRPT2 (parafibromin) interacts with cyclin D1, we investigated cyclin D1 expression with the use of qPCR and IHC. Results LOH was detected in 3/5 FD, 6/9 OF, and 2/2 OS heterozygous samples. LOH was not associated with decreased mRNA levels or HRPT2 protein expression except for 1 OF which harbored an inactivating mutation. However, this tumor did not display altered transcription or protein levels of HRPT2 nor cyclin compared with the other OF. Conclusions The contribution of HRPT2 inactivation to the pathogenesis of OF, FD, and OS is marginal at best and may be limited to progression rather than tumor initiation.