Expression of dental/bone matrix proteins in a craniofacial bone tumor

Bone and dentin are collagenous mineralized tissues that are highly similar in both composition and mechanism of formation. Both tissues contain a number of non-collagenous matrix proteins that include dentin matrix protein (Dmp-1), dentin sialophosphoprotein (DSPP) and bone sialoprotein (BSP). These dentin/bone proteins share common structural features and are localized within a gene cluster on human chromosome 4q21. Craniofacial bone tumors seem to reproduce the morphological and inductive mechanisms established during primary embryonic development. Previous studies have shown BSP expression as a predictor marker of tumor progression. However, data are lacking regarding the expression and role of other dentin/bone matrix proteins in bone tumorogenesis. Our hypothesis is that these matrix dentin/bone proteins have important biological functions in craniofacial tumorogenesis, distinct from those roles during normal development. Objectives: To determine the expression pattern of multiple dental/bone matrix proteins in a tumor isolated from a young patient diagnosed with multiple ossifying fibroma/fibrous dysplasia of the mandible, a benign lesion presumably developmental in nature. Methods: Tumor samples were obtained at the time of surgery with informed consent, fixed, embedded in paraffin, and sectioned. Tumor sections were analyzed using immunohistochemistry with polyclonal antibodies against DMP-1, DSP, DSPP, BSP, osteonectin (OSN), osteocalcin, vimentin and keratin. Results: In contrast to the ubiquitous expression pattern of OSN, differences were seen in the expression patterns and levels of staining for the other dental/bone matrix proteins, depending on the stage of cellular differentiation. While BSP strongly labeled osteoblasts and bone matrix, there was predominant staining of DMP-1 in the osteoid, and DSP/DSPP in the osteoblasts. Conclusions: Our study provides preliminary information related to the dentin/bone matrix protein expression patterns in a craniofacial bone tumor that may be relevant for potential new diagnostic and treatment strategies. Support by NIDCR DE11658 (MM).