Photodynamic therapy for human oral squamous cell carcinoma and xenografts using a new photosensitizer, PAD-S31.

BACKGROUND AND OBJECTIVES: Photodynamic therapy (PDT) is a novel and promising cancer treatment that employs a combination of photosensitizer and visible light. We examined the effect of PDT using a new photosensitizer, PAD-S31, and the 670-nm diode laser in human oral squamous cell carcinomas (SCC). STUDY DESIGN/MATERIALS AND METHODS: SAS and HSC-4 cell lines were used in all the experiments. Cell viability was determined by a modified MTT assay. Two methods were used for the determination of apoptosis in human oral SCC cells: TUNEL assay and detection of fragmented mono- and oligo-nucleosomes by ELISA. Xenografts of human oral SCC cells were generated in KSN S1c nude mice. RESULTS: In vitro PDT using PAD-S31 and the 670-nm diode laser showed cytotoxicity that was a function of laser energy, drug concentration, and time to the SAS and HSC-4 cell lines. On the other hand, PAD-S31 without irradiation had no effect on cell viability. The combinated use of PAD-S31 and the laser irradiation showed excellent anti-tumor activity against tumor xenografts without severe side effects. PDT-mediated cell death occurred predominantly by apoptosis in vitro and in vivo. CONCLUSIONS: The present study demonstrates that PAD-S31 may serve as a potent photosensitizer for PDT. Furthermore, it is expected that this therapy will be clinically useful for the treatment of patients with oral carcinoma.