Photosynthetic microorganisms coupled photodynamic therapy for enhanced antitumor immune effect

The ideal photodynamic therapy (PDT) should effectively remove the primary tumor, and produce a stronger immune memory effect to inhibit the tumor recurrence and tumor metastasis. However, limited by the hypoxic and immunosuppressive microenvironment, the PDT efficiency is apparently low. Here, Chlorella (Chl.) is exploited to enhance local effect by producing oxygen to reverse hypoxia, and release adjuvants to reverse immunosuppressive microenvironment to enhance abscopal effect afterwards. Results from different animal models indicated that Chl. could enhance local effect and PDT related immune response. Ultimately, Chl. coupled PDT elicited anti-tumor effects toward established primary tumors (inhibition rate: 90%) and abscopal tumors (75%), controlled the challenged tumors (100%) and alleviated metastatic tumors (90%). This Chl. coupled PDT strategy can also produce a stronger anti-tumor immune memory effect. Overall, this Chl. coupled PDT strategy generates enhanced local tumor killing, boosts PDT-induced immune responses and promotes anti-tumor immune memory effect, which may be a great progress for realizing systemic effect of PDT.