| Despite significant advances in the diagnosis and treatment of head and neck cancer, the survival rate of patients has not changed significantly during the last decade suggesting that novel therapeutic approaches are worth investigation. In this project, we investigate the use of FasL gene therapy in combination with acid ceramidase (AC) inhibitors as a new promising modality for the treatment of head and neck cancer. We first demonstrate the in vitro and in vivo efficacy of FasL gene therapy for the treatment of head and neck squamous cell carcinoma (HNSCC). Next, we show that the ceramide metabolizing enzyme AC is over-expressed in 70% of head and neck squamous cell tumors and that AC over-expression increases resistance to Fas-induced cell killing. Conversely, AC inhibition using specific AC siRNA sensitizes the head and neck cancer cell line SCC-1 to Fas-induced apoptosis. We also introduce a new family of lysosomotropic acid ceramidase inhibitors (LCL 204 and its analogues) developed at the lipidomics core at the Medical University of South Carolina. We demonstrate that these small molecule inhibitors lead to acid ceramidase inhibition in cancer cell lines in vitro and in head and neck tumor tissues in nude mice experiments. Importantly, the lysosomotropic acid ceramidase dosage used to inhibit acid ceramidase is also shown to be non-toxic in vivo as confirmed by their minimal effects on bone marrow, liver and kidney functions. Finally, pretreatment with LCL 204 significantly enhances FasL gene therapy effect on HNSCC cell lines as confirmed by in-vitro cytotoxicity, apoptotic assays, and in vivo xenographs tumor growth and survival. In summary, this work demonstrates critical roles for acid ceramidase in head and neck cancer therapy and that combination of lysosomotropic acid ceramidase inhibitors with FasL gene therapy may become a new treatment option for advanced stage head and neck cancer worthy of a clinical trial. |
