Evidence of loss of heterozygosity of the PTCH gene in orthokeratinized odontogenic cyst.

The orthokeratinized odontogenic cyst (OOC) is an odontogenic cyst of unknown etiology. Clinical, histological, and biological differences are reported between keratocystic odontogenic tumor (KOT) and OOC. PTCH is a tumor suppressor gene related to sonic hedgehog (SHH) pathway important in embryological development. Considering that alterations in this pathway have been described in sporadic and nevoid basal cell syndrome-associated KOT, we tested the hypothesis that OOC is also associated with loss of heterozygosity (LOH) of the PTCH gene. Seven samples of OOC and seven of KOT were included in the study. D9S287, D9S196, and D9S127 microsatellite markers located in the region of PTCH gene, at chromosome 9q, were investigated for LOH. There was loss in at least one locus in 5/7 KOT and in 4/7 OOC samples. The present finding demonstrates that, despite the existence of clinical, morphological, immunohistochemical, and biological behavior differences between OOC and KOT, both harbor similar genetic alterations at 9q.