Hedgehog targeting by cyclopamine suppresses head and neck squamous cell carcinoma and enhances chemotherapeutic effects.

The hedgehog signaling pathway (HH) is involved in tumorigenesis in a variety of human malignancies. In head and neck squamous cell carcinomas (HNSCC), Hh overexpression was associated with poor prognosis. Therefore, we analyzed the effect of Hh signaling blockade with cyclopamine on colony formation of cells from HNSCC samples. HNSCC biopsies were cultured alone for reference or with serial dilutions of cyclopamine (5-5,000 nM), docetaxel (137.5-550 nM), or cisplatin (1,667-6,667 nM) and their binary combinations. Cytokeratin-positive colonies were counted after fluorescent staining. Cyclopamine concentration-dependently inhibited HNSCC ex vivo [(IC50) at about 500 nM]. In binary combinations, cyclopamine additively enhanced the suppressive effects of cisplatin and docetaxel on HNSCC colony formation. Our findings define SMO--a Hh component- as a potential target in HNSCC and suggest the utility of Hh targeting in future multimodal treatment regimens for HNSCC.