Reinforced immunotherapy of M1 macrophage-derived exosomes with CEL on TNBC via regulating macrophage functions

Triple-negative breast cancer (TNBC) demonstrates poor prognosis due to its heterogeneity-related biological barrier, immunosuppressive tumor microenvironment (TME) and escape of cancer cells on immune surveillance. Exosomes are membrane-encased vehicles with properties of inter- and intra-cellular communication and regulation for therapeutic use, even as drug vehicles. M1 macrophage-derived exosomes (M1-Exos) can communicate with adjacent M2 macrophages and reprogram them to M1 subtypes to reshape TME. Celastrol (CEL) is a highly promising natural antitumor drug and plays an important role in immunotherapy but with high toxicity and low water solubility.

This work aims to provide reinforced immunotherapy to reshape tumor immunosuppressive microenvironment of TNBC by employing M1-Exos as a nanoscale co-delivery vehicle for CEL, offering increased tumor targeting and antitumor efficacy while reducing systemic toxicity to achieve improved treatment outcomes.

A versatile combinatorial delivery system, tLyP-1-M1-Exos/CEL, was engineered by modifying tLyP-1 peptide and loading CEL to M1-Exos, then the size distribution, morphological features were characterized by transmission electron microscope, nanoparticle tracking analysis, and biomarkers were characterized by western blot. The efficacy and mechanism were assessed using CCK-8, qPCR, immunofluorescence, in vivo fluorescence imaging system, flow cytometry, western blot, H&E staining and other methods at cellular level and in nude mice.

The synthesized tLyP-1-M1-Exos/CEL exhibited specific tumor-targeting ability, greater tumor-suppressing properties and lower toxicity. The expression of M1 markers was upregulated and the expression of M2 markers was downregulated in M2-phenotype macrophages co-incubated with tLyP-1-M1-Exos/CEL. tLyP-1-M1-Exos/CEL decreased the expression of MHC I by inhibiting IRF1-CIITA signal pathway, making tumor cells more susceptible to be phagocytosed by macrophages.

Our study showed a reinforced immunotherapy that the synthesized tLyP-1-M1-Exos/CEL could not only reverse M2 macrophages into M1 to reshape immunosuppressive TME but also decrease the expression of MHC Ⅰ on tumor surface to enhance macrophage phagocytic autoimmunity.