Photodynamic therapy (
PDT) of
cancer is an experimental
tumor therapy which is based on the combined use of a systematically administered
photosensitizer to a
tumor-bearing host and local illumination of the lesion by a high-intensity visible light source, typically a tunable
argon dye laser. Human
squamous cell carcinoma (HSCC) is the most frequently encountered
malignancy of the head and neck. In this study, responses 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 response with
Photofrin-II (Pf-II),
chloroaluminum phthalocyanine tetrasulfonate (AlPcTS), and a newly synthesized
silicon phthalocyanine (
SiPc 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 establishment of a
tumor. The
tumor was minimally immunogenic and showed neither macroscopic signs of early
metastasis to lung, kidney, liver, or spleen nor evidence of surrounding
erythema, fluctuation, or tenderness until the late stages of
necrosis. Intraperitoneal administration of AlPcTS or
SiPc IV to
tumor-bearing mice resulted in rapid uptake of the
photosensitizers in liver, skin, and
tumor tissue. Twenty-four hours following the intraperitoneal administration of AlPcTS or
SiPc IV to
tumor-bearing animals, the
tumor to normal skin ratio of the
photosensitizer 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
tumor (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.