Nanotherapeutic platform-mediated cholesterol metabolism regulation for boosting antitumor chemo-immunotherapy

Chemotherapy, as one of the most commonly used treatments for tumors, has been confirmed to induce immunogenic cell death (ICD) of tumor cells, which could activate a robust antitumor immune response. However, the elevated cholesterol level in the tumor microenvironment (TME) promotes the activation and proliferation of myeloid-derived suppressor cells (MDSCs), which would inhibit the antitumor effect, thereby reducing the therapeutic performance of chemo-immunotherapy. Here, a poly(lactide-co-glycolide acid) (PLGA)-based nanotherapeutic platform (COD/MTO@PLGA@FA) is rationally designed by co-loading mitoxantrone (MTO) and cholesterol oxidase (COD) for boosting chemo-immunotherapy. Specifically, the designed COD/MTO@PLGA@FA would respond to the acidic TME to rapidly release MTO and COD, respectively. Thus, the free MTO could kill tumor cells directly and induce potent ICD, thereby activating the antitumor immune response. Meanwhile, the released COD could downregulate the expression of PD-1 on tumor-infiltrating CD8(+) T cells by consuming cholesterol in TME, thereby reversing the exhausted state of tumor-infiltrating CD8(+) T cells. Particularly, the reduction of cholesterol levels in TME would also inhibit the activation of MDSCs, further remodeling the immunosuppressive TME. In combination with anti-programmed death-ligand 1 antibody (alpha PD-L1), COD/MTO@PLGA@FA could significantly inhibit the growth of tumors, providing a practical strategy to enhance chemotherapy and highlighting new opportunities for chemo-immunotherapy.