The Anticancer Effect and Mechanism of Photodynamic Therapy Using 9-Hydroxypheophorbide-alpha and 630 nm Diode Laser on Heterotransplanted Squamous Cell Carcinoma of Head and Neck

Kim, Han Gyun; Chung, Phil Sang; Kim, Se Hyung; Lee, Sang Hun; Rhee, Chung Ku

Abstract

BACKGROUND AND OBJECTIVES
The 9-Hydroxypheophorbide-alpha(9-HpbD-alpha) is a new photosensitizer, derived from a plant in water. We conducted a series of experiments in vivo to evaluate the anticancer effect and mechanism of photodynamic therapy using 9-HpbD-alpha and 630 nm diode laser on squamous cell carcinoma. MATERIALS AND METHOD: SNU-1041 cell line was heterotransplanted into the subcutaneous space of nude mouse. When the tumors grew up to 400 mm3, the animals were randomly seperated into 4 groups: Group I (n=5) of the normal control group;Group II (n=10), which received interstitial injection of 0.007 microgram/mm3 of 9-HpbD-alpha;Group III (n=10), which received irradiation with 1.6 J/mm3 of light using diode laser;Group IV (n=10), which received interstitial injection of 0.007 microgram/mm3 of 9-HpbD-alpha followed by irradiation with 1.6 J/mm3 of light 6 hours after the injection. After photodynamic therapy (PDT), tumor tissue was harvested for histopathologic study under light microscopy and transmission electron microscope (TEM). RESULTS: PDT group (Group IV) showed significant remission rate (70 %), compared to control group (p<0.05). The microscopic findings of the tumor section were characterized by massive necrosis and some apoptotic cells among the normal cells. TEM showed different morphologic changes between necrotic and apoptotic cells. These findings were considered as the evidence of direct cytotoxicity of PDT using 9-HpbD-alpha and 630 nm diode laser. CONCLUSION: The results suggest that therapy using PDT, 9-HpbD-alpha and diode laser shows an anticancer effect. Its therapeutic mechanism appears to be based on necrosis that is caused by direct cytotoxicity.