PHOTODYNAMIC THERAPY OF HUMAN SQUAMOUS-CELL CARCINOMA IN-VITRO AND INXENOGRAFTS IN NUDE-MICE

Photodynamic therapy (PDT) of cancer is an experimental tumor therapy which is based on the combined use of a systemically administered phot osensitizer to a tumor-bearing host and local illumination of the lesi on by a high-intensity visible light source, typically a tunable argon dye laser. Human squamous cell carcinoma (HSCC) is the most frequentl y encountered malignancy of the head and neck. In this study, response s of HSCC cells to PDT were examined in in vitro and in vivo systems. In in vitro studies, the HSCC cells showed a positive photodynamic res ponse with Photofrin-II(R) (Pf-II), chloroaluminum phthalocyanine tetr asulfonate (AlPcTS), and a newly synthesized silicon phthalocyanine (S iPc IV). Single cell suspension of HSCC injected subcutaneously on the back of athymic nude mice resulted in a well-circumscribed tumor mass . The animals required a low tumor dose for the successful establishme nt of a tumor. The tumor was minimally immunogenic and showed neither macroscopic signs of early metastasis to lung, kidney, liver, or splee n nor evidence of surrounding erythema, fluctuation, or tenderness unt il the late stages of necrosis. Intraperitoneal administration of AlPc TS or SiPc IV to tumor-bearing mice resulted in rapid uptake of the ph otosensitizers in liver, skin, and tumor tissue. Twenty-four hours fol lowing the intraperitoneal administration of AlPcTS or SiPc IV to tumo r-bearing animals, the tumor to normal skin ratio of the photosensitiz er was 1.6 or 1.5, respectively. Administration of Pf-II (5 mg/kg) to tumor-bearing animals followed 24 hours later by irradiation of the tu mor (135 J/cm2, 630 nm light from an argon pumped-dye laser) resulted in greater than 80% ablation in tumor volume 24 hours post-PDT. These characteristics make this tumor model system suitable for PDT studies of human tumor cells in vitro as well as in vivo.