Inhibition of PDT-induced PGE2 surge for enhanced photo-immunotherapy

Nowadays, photodynamic therapy (PDT) offers a non-invasive tumor treatment with high safety profiles and minimal side effects, implying a promising clinical application for patients with malignant tumors. However, the lack of efficacy in metastasis and recurrence still notably limits its application. To solve this problem, one promising strategy is to improve the immune response activated by PDT. Unfortunately, tumor cells derived PGE2 could create immunosuppressive microenvironments and impair the function of multiple immune cells, leading to a failure of immune system activation. Moreover, our research revealed the up-regulation of Ptgs2 in tumor cells after the PDT process, which is associated with a series of pro-tumor effects, including proliferation, invasion, metastasis, apoptotic resistance, and immune evasion. Consequently, controlling the PGE2 surge induced by PDT is crucial for optimizing the efficacy of photo-immunotherapy. Therefore, we combined the regulation of the COX2-PGE2 axis with PDT. The addition of COX inhibitors (COX-Is) could improve the efficiency of PDT, reduce the immunosuppressive effect of PGE2, and help dying tumor cells activate the immune system. Herein, a tumor-targeted nano-delivery platform (FI@T-Lipo) was developed using advanced microfluidic technology. FI@T-Lipo based PDT showed a systemic therapeutic effect in triple negative breast cancer through reclaiming the anti-tumor effect of the immune system under COX2-PGE2 blockage. In a word, we developed an in-situ tumor vaccination strategy based on COX-Is enhanced PDT, which could alleviate intra-tumoral immune suppression and boost immune system activation. Our study offers a promising modality for advancing clinical treatment strategies for metastatic malignant tumors.