Modulation of hematoporphyrin derivative-sensitized phototherapy with corynebacterium parvum in murine transitional cell carcinoma.

The interaction of photodynamic therapy (PDT) with hematoporphyrin derivative (Hpd) and immunotherapy with Corynebacterium parvum (CP) was studied in a murine transitional cell carcinoma (MBT-2) model. C3H/He mice were transplanted subcutaneously in the hind limb with 2.5 X 10(5) tumor cells. One day after transplantation, mice were randomized into groups to receive saline (control), PDT, CP 25 micrograms, CP 250 micrograms, CP 25 micrograms + PDT, and CP 250 micrograms + PDT. PDT was administered by intraperitoneal (IP) injection of Hpd (12.5 micrograms/g body weight), followed twenty-four hours later by photoirradiation. CP was given intralesionally at the same time as IP injection of Hpd (24 hours before photoirradiation). A low dose of CP (25 micrograms) was shown to enhance the effect of PDT while PDT reduced the benefit obtained with high dose of CP (250 micrograms). In a second series of experiments, CP (250 micrograms) treatment after photoirradiation was shown to give significantly greater benefit than CP treatment before photoirradiation. The study thus indicates that the effectiveness of combined immunophototherapy is dependent on the sequence of the combination and its intricate relationship with the dosage of CP. The enhancement of PDT by low dose of CP in this model suggests the usefulness of this combined immunophototherapy in enhancing tumor control and in lessening deleterious side effects.