Selectively targeting tumor-associated macrophages and tumor cells with polymeric micelles for enhanced cancer chemo-immunotherapy

Abstract Tumor-associated macrophage (TAM)-related immunotherapy is a greatly promising strategy that involves altering the immunosuppressive tumor microenvironment with the immunomodulator imiquimod (R837) for enhanced cancer therapy. However, the function of R837 is seriously limited due to poor water solubility and a lack of targeting ability. Here, we developed two types of targeting polymer micelles to separately deliver R837 and the anticancer drug doxorubicin (DOX) to TAMs and tumor cells via intratumoral injection and intravenous injection, respectively, for enhanced cancer chemo-immunotherapy against breast cancer. After these micelles accumulated in the tumor tissues, the immunostimulating micelles released R837, which bound to the TLR-7 receptor on the lysosomal membrane within the TAM, stimulating the maturation of the TAM, thereby causing an antitumor immune response and relieving the immunosuppressive effect in the tumor microenvironment. Simultaneously, the chemotherapeutic micelles released DOX in the cytoplasm of the tumor cells, directly inducing cell death. As a result, a synergistic combination of chemotherapy and immunotherapy was achieved through these nanomedicines, which separately activated the antitumor immune response and inhibited tumor cell growth. Therefore, this strategy is a new avenue for the development of targeting nanomedicines for combination chemo-immunotherapy against malignant cancer.