Combined cytotoxic action of paclitaxel and ceramide against the human Tu138 head and neck squamous carcinoma cell line

Purpose: Paclitaxel, a chemotherapeutic agent used in the treatment of reca lcitrant ovarian and breast as well as other neoplasms, is being investigat ed for the treatment of squamous cell carcinoma of the head and neck. Our p revious studies have demonstrated that exogenously added ceramide enhances apoptosis in paclitaxel-exposed human leukemic cells. in this study, we sho wed that exogenous ceramide augmented paclitaxel-induced apoptosis in Tu138 cells in vitro when added simultaneously in combination with the paclitaxe l. Methods: The combined cytotoxic effects of paclitaxel and ceramide expos ure against Tu138 cells were assessed by an MTT dye assay, cell cycle analy sis, TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end la beling) assay, and isobologram analysis for synergistic activity. Results: The MTT dye assay results indicated augmentation of time- and concentration -dependent paclitaxel-mediated cell cytotoxicity by simultaneouss ceramide treatment. Paclitaxel treatment of Tu138 cells also resulted in an accumula tion of cells in the G(2)-M phase of the cell cycle. This paclitaxel-mediat ed G(2)-M phase accumulation decreased significantly with the addition of c eramide, indicating that combined paclitaxel/ceramide treatment resulted in the elimination of Tu138 cells from the S and/or G(2)-M phases of the cell cycle. Furthermore, ceramide enhancement of paclitaxel-mediated apoptosis was also detected by the TUNEL assay. Conclusion: Our results suggest that paclitaxel/ceramide combination therapy may be an attractive alternative to conventional methods of chemotherapy for head and neck cancer, and should be further explored.