Efficacy of ZnPcS2P2 photodynamic therapy solely or with tumor vaccines on mouse tumor models.

Background And Objectives: Granulocyte-macrophage colony-stimulating factor (GM-CSF) and B7.1 transduced tumor vaccine cells could induce efficient anti-tumor immune response. It is interesting to study whether they could be an adjuvant to photodynamic therapy (PDT). Recent in vitro study proved that novel photosensitizer ZnPcS2P2 has capability of effective photodynamic killing of leukemic cells. In this preliminary study, we evaluated the photodynamic efficacy of ZnPcS2P2 on two tumor models and the improving anti-tumor efficacy of PDT in combination with GM-CSF gene-transduced vaccine and B7.1 gene-transduced vaccine.

Methods: Nude mice bearing human leukemia xenograft and C57BL/6 mice bearing EL-4 thymic lymphoma were used to evaluate photodynamic efficacy of ZnPcS2P2. The EL-4 thymic lymphoma was used to test the improving anti-tumor efficacy of ZnPcS2P2-PDT in combination with GM-CSF gene-transduced vaccine and B7.1 gene-transduced vaccine. Each vaccine was administered near the tumor bed three times: 2 days before PDT, 0 and 2 days after PDT.

Results: ZnPcS2P2-PDT could significantly reduce tumor growth and prolong the survival time in both tumor models. Improving anti-tumor efficacy of ZnPcS2P2-PDT was demonstrated when utilizing GM-CSF-transduced vaccine and B7.1-transduced vaccine prior to and after ZnPcS2P2-PDT in lymphoma-bearing mice. Twenty-five percent of lymphoma-bearing mice were completely cured with a combination of PDT and vaccine cells.

Conclusions: ZnPcS2P2-PDT may be a beneficial treatment for hemotopoietic malignance. GM-CSF-transduced vaccine and B7.1-transduced vaccine could strengthen ZnPcS2P2-PDT-elicited anti-lymphoma potency.