Anti-tumor immunity induced by local photothermal-immunoadjuvant therapy in a poorly immunogenic metastatic tumor model

Abstract

Laser immunotherapy is a novel method developed to treat metastatic tumors. The selective photothermal interaction using a near-infrared laser and indocyanine green destroys living tumor cells while preserving antigenic tissue derived protein. The treated tumor remained in the host as a source of exposed tumor antigens. Working in tandem with the applications of immunoadjuvant, laser immunotherapy has shown to induce an anti-tumor immunity in a metastatic mammary tumor model in rats. To further study the effect of laser immunotherapy, the immunogenicity of the rat model, DMBA-4, was investigated through surgical removal or primary tumors and by tumor immunization using freeze-thaw tumor cell lysates. The surgical removal of the primary tumors did not have any effect on the recurrence of the tumors at the primary sites. The metastases at remote sites also developed after the surgery. In the tumor challenges following the immunization, the immunized rats only had delayed emergence of the primary tumors and the metastases. All the immunized rats died with multiple tumors. The laser immunotherapy cured rats, on the other hand, showed strong tumor resistance in repeated tumor rechallenges. Our results showed that the laser immunotherapy could induce a strong anti-tumor immunity in a poorly immunogenic tumor model. Furthermore, the effect of laser immunotherapy on the metastases at remote sites indicated that this novel method could become an effective method in treating the metastatic tumors.