Sonodynamic therapy-assisted immunotherapy: A novel modality for cancer treatment

Sonodynamic therapy (SDT), which is based on photodynamic therapy (PDT), is a new cancer treatment modality. Unlike PDT, which has poor tissue penetration, ultrasound can penetrate deeply into tissues and largely target tumor tissue to mediate the cytotoxicity of sonosensitizers. We hypothesize that, similar to PDT, SDT may perform effectively as a cancer vaccine. Thus, we developed a therapeutic strategy to explore whether SDT can eliminate primary tumors, inhibit metastases, and prevent tumor relapse. In the present study, we found that HiPorfin (HPD)-induced SDT killed tumor cells, promoted calreticulin expression on the cell surface and elicited immune responses. Meanwhile, we observed that SDT induced functional antitumor vaccination and abscopal effects in H22 tumor-bearing mice. Furthermore, this strategy conferred an immunological memory, which could protect against tumor recurrence after the elimination of the initial tumor. These results showed important effects of SDT on immune responses.