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 recalcitrant ovarian and breast as well as other neoplasms, is being investigated for the treatment of squamous cell carcinoma of the head and neck. Our previous studies have demonstrated that exogenously added ceramide enhances apoptosis in paclitaxel-exposed human leukemic cells. in this study, we showed that exogenous ceramide augmented paclitaxel-induced apoptosis in Tu138 cells in vitro when added simultaneously in combination with the paclitaxel. Methods: The combined cytotoxic effects of paclitaxel and ceramide exposure against Tu138 cells were assessed by an MTT dye assay, cell cycle analysis, TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling) 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 accumulation of cells in the G(2)-M phase of the cell cycle. This paclitaxel-mediated G(2)-M phase accumulation decreased significantly with the addition of ceramide, 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.