Photodynamic therapeutic efficacy of symmetrical diiodinated squaraine in in vivo skin cancer models

Background: Photodynamic therapy (PDT) has clinical approval for use as a minimally invasive therapeutic procedure that is able to exert selective cytotoxic activity toward malignant cells. The dye selected for our study, symmetrical diiodinated squaraine, is one of the newly developed photosensitizers. The study is designed to determine the efficacy of PDT mediated by symmetrical diiodinated squaraine in skin tumor induced Swiss albino mice.

Methods: Skin tumor was induced in mice with dimethyl benzanthracene (DMBA) and croton oil. After squaraine administration to the tumor mice, photodynamic treatment of tumors was performed using a 1000W halogen lamp corresponding to the light dose of 100J/cm². The mice were euthanized and skin flaps and tumor tissues from the back of mice were excised for biochemical studies. The biochemical parameters analyzed include some relevant tumor markers for epithelial tissues, inflammatory markers and markers of apoptosis. The gene expression studies were done by RT-PCR.

Results: After two weeks of the treatment, there was significant inflammation. However at 90days after PDT, the parameters reverted to near-normal values. All marker parameters of tumor progression brought back to normal levels by PDT. Increased caspase-3 activity in PDT treated group shows that cell death might have occurred by apoptosis. The gene expression profile confirms the results.

Conclusions: The results of the whole study show the therapeutic efficacy and apoptosis mediated tumor destruction by squaraine PDT.