Targeting the Sonic Hedgehog Pathway in Keratocystic Odontogenic Tumor

Abstract

Background: Keratocystic odontogenic tumors (KCOT) have a high rate of recurrence and very limited treatment options beyond surgery. Results: Cyclopamine, a smoothened antagonist, reduced KCOT cell viability and signaling components of the hedgehog and NOTCH signaling pathways. Conclusion: Hedgehog signaling mediates KCOT cell survival. Significance: Inhibitors of hedgehog signaling may be valuable in the treatment of KCOT. Keratocystic odontogenic tumors (KCOT) may occur sporadically or associated with the nevoid basal cell carcinoma syndrome. It is a benign aggressive tumor of odontogenic epithelial origin with a high rate of recurrence. A primary human keratocystic odontogenic tumor cell population, KCOT-1, has been established from a tumor explant culture. The KCOT-1 cells were characterized by growth rate, gene expression profiles of major tooth enamel matrix proteins (EMPs), amelogenin (AMELX), enamelin (ENAM), ameloblastin (AMBN), amelotin (AMTN), tumor-related proteins enamelysin (MMP-20), kallikrein-4 (KLK-4), and odontogenic ameloblast-associated protein (ODAM) using quantitative real-time reverse transcriptionpolymerase chain reaction. Cytokeratin 14 (CK14) was examined by immunohistochemistry. In addition, expression of the members of the sonic hedgehog (SHH) pathway, SHH, patched (PTCH-1), smoothened (SMO), GLI-1, and GLI-2 and of the NOTCH signaling pathway, NOTCH-1, NOTCH-2, NOTCH-3, JAG-2 (Jagged-2), and Delta-like-1 (DLL-1) were evaluated. KCOT-1 cells were treated with SMO antagonist cyclopamine. We found that cyclopamine significantly arrested the growth of KCOT-1 cells in a dose-dependent manner and that the effects of cyclopamine were abolished by adding SHH protein. The protein expression of the SHH pathway was down-regulated by cyclopamine, further confirming that cyclopamine inhibits the SHH signaling pathway; SHH downregulation correlated with the down-regulation of the NOTCH signaling pathway as well. In conclusion, using an established KCOT-1 cell population, we characterized the gene expression profiles related to the EMPs, SHH, and NOTCH signaling pathway and confirmed that cyclopamine significantly arrested the growth of KCOT-1 cells and may be a viable agent as a novel therapeutic. Keratocystic odontogenic tumor (KCOT), 3 previously