Photodynamic Therapy of the Murine LM3 Tumor Using Meso-Tetra (4-N,N,N-Trimethylanilinium) Porphine

Photodynamic therapy (PDT) of cancer is based on the cytotoxicity induced by a photosensitizer in the presence of oxygen and visible light, resulting in cell death and tumor regression. This work describes the response of the murine LM3 tumor to PDT using meso-tetra (4-N,N,N-trimethylanilinium) porphine (TMAP). BALB/c mice with intradermal LM3 tumors were subjected to intravenous injection of TMAP (4 mg/kg) followed 24 h later by blue-red light irradiation (λmax: 419, 457, 650 nm) for 60 min (total dose: 290 J/cm(2)) on depilated and glycerol-covered skin over the tumor of anesthetized animals. Control (drug alone, light alone) and PDT treatments (drug + light) were performed once and repeated 48 h later. No significant differences were found between untreated tumors and tumors only treated with TMAP or light. PDT-treated tumors showed almost total but transitory tumor regression (from 3 mm to less than 1 mm) in 8/9 animals, whereas no regression was found in 1/9. PDT response was heterogeneous and each tumor showed different regression and growth delay. The survival of PDT-treated animals was significantly higher than that of TMAP and light controls, showing a lower number of lung metastasis but increased tumor-draining lymph node metastasis. Repeated treatment and reduction of tissue light scattering by glycerol could be useful approaches in studies on PDT of cancer.