Análise molecular dos genes HRPT2 e CICLINA D1 na displasia fibrosa, no fibroma ossificante e no osteossarcoma dos maxilares

Abstract

Fibrous dysplasia (FD), ossifying fibroma (OF), and osteosarcoma (OS) are examples of bone-related lesions. Recent studies have already shown genetic alterations of the HRPT2 tumor suppressor gene in sporadic and syndromic OF. The present study first sought to raise the hypothesis of whether or not similar alterations would in fact represent one of the underlying genetic alterations of both FD and OS. This study investigated alterations of the HRPT2/ parafibromin at the DNA level (using the loss of heterozygosity analysis - LOH), at the mRNA level (through RT-PCR, direct sequencing, and qRT-PCR), and in proteins through immunohistochemistry(IHC) in a set of OF, FD, and OS cases. In vitro studies pointed toward the inhibition of cyclin D1 as a mechanism of HRPT2 to produce antiproliferative effects. Thus, cyclin D1 expression through qRT-PCR and IHC was also investigated. LOH at 1q25.3 was assessed by using 2 microsatellite markers: D1S384 and D1S461. The LOH of HRPT2 was found in 3 FD, 6 OF, and 2 OS cases. However, this did not prove to be associated with alterations in the mRNA transcription or protein expression of the gene. The HRPT2 mutation was found only in the OF (primary and recurrent lesion). This mutation commonly leads to the formation of a truncated protein; however, in this case, it caused no alteration in the transcription of the HRPT2 and cyclin D1 genes. In addition, this study found a positive correlation between the mRNA transcription of HRPT2 and cyclin D1, which was not observed between parafibromin and cyclin D1 protein immunostaining. In conclusion, this studys results emphasize that DNA alterations of the HRPT2 gene can be detected in OF as well as in FD and OS, but the mutation or LOH of this gene does not necessarily impact mRNA or protein expression.