Inhibitory and immunological effects induced by the combination of photodynamic therapy and dendritic cells on mouse transplanted hepatoma.

Objective: To investigate the anti-tumor and immune efficacy of photodynamic immune-therapy (PIT), the combination of photodynamic therapy and dendritic cells (DC), on murine Heps hepatoma.

Methods: DCs were derived from syngeneic mouse bone marrow and then labeled with DAPI in vitro. The hepatoma model was established by subcutaneous inoculation with Heps cells in one hundred and twenty-eight mice. They were then divided into four groups at random: control group, PDT group, DC group and PIT group. Tumors in the control group were injected with normal saline. Mice in the PDT group were injected with the photosensitizer Deuteporfin 24 h before irradiation. Mice in the DC group were injected with DAPI labeled dendritic cells intratumorally. Mice in the PIT group were further given an injection of DCs after photoirradiation. Tumor growth and survival time were recorded after treatment. Fluorescence of tumor draining lymph nodes was evaluated under fluorescence microscope. Cytotoxic activity of splenocytes was tested by standard lactate dehydrogenase (lactate dehydrogenase, LDH) release assay.

Results: (1) Tumor growth was significantly slowed down in the PDT and PIT group compared to the control group (P<0.01). (2) The mean survival time was significantly prolonged in the PDT and PIT group. (3) The number of fluorescent cells in the draining lymph nodes from DC group was higher than that of the PIT group. (4) The anti-tumor activity of splenocytes in the PDT and PIT group was significantly higher than that of the DC and control groups (P<0.01, P<0.01).

Conclusions: The present study suggests that PDT can inhibit tumor growth and induce anti-tumour immune response. The combination of PDT induced by Deuteporfiin and dendritic cell is capable of amplifying the antitumor immune response.