Objectives: To examine the expression of sphingosine kinase (SPK) levels in patients with head and neck squamous cell carcinoma (HNSCC) at different clinical stages. To demonstrate that SPK inhibition leads to higher levels of ceramide in HNSCC cells, which enhances irradiation-induced apoptosis and also inhibits tumor invasion and migration.
Design: Expression of SPK was determined by Western blot, real-time polymerase chain reaction (RT-PCR), and immunohistochemical staining from fresh and archival tissues and HNSCC cell lines. Sphingosine kinase siRNA was tested to block the tumor growth invasiveness and migration of HNSCC. Ceramide levels and effect of irradiation on tumor and normal cells were studied.