Treatment-Induced Temporal Changes Of Singlet Oxygen Can Indicate Photodynamic Responses In Solid Tongue Cancer Model

Objective singlet oxygen (¹O₂) generated in photodynamic therapy (PDT) plays a very important role in killing tumor cells. Using a new near-infrare photomultiplier tube system (NIR-PMT), we measured the temporal changes of ¹O₂ induced by various PDT conditions, and utilized it for predicting long-term response to treatment.Methods Human oral squamous cell carcinoma cell line HSC-3 was used as cell model, and 5-ALA was adopted as photosensitizer. PDT was performed under low- to high- laser conditions, and the consequent ¹O₂ was monitored in real time for both in vitro and in vivo. We further investigated the relationships between ¹O₂ production and tumor death, and established the optimal laser conditions. Subsequently, an animal PDT was made based on the established conditions, and the tumor growth was recorded in 90 days after treatment. A long-term response to PDT for solid tongue tumor was investigated.Results ¹O₂ production showed a clear laser output (fluence and fluence-rate)-dependence during PDT. In the same exposure time, high laser output can generate large amount of ¹O₂, and results in the strong photodynamic effects. Although the solid tumor conducted with optimal PDT conditions showed a significant size decline <90 days after treatment, compared to the controls, we still observed a slightly re-growth in two big tumors.Conclusion The present studies established ¹O₂ as an indicator for optimal irradiation during PDT, and showed a relationship between the ¹O₂ production and photodynamic effects. Although it showed a strong anti-tumor effect on solid tongue tumor model, it was suggested that 5-ALA induced PDT might be more effective for small tumor of oral cavity.