Gd-metallofullerenol drug delivery system mediated macrophage polarization enhances the efficiency of chemotherapy

Abstract

Treatment of solid tumors by chemotherapy is usually failed in clinical because of its low effectiveness and side effects. Stimulation of immune system in vivo to fight cancer has been proved to be a pleasant complementary to systemic chemotherapy. Herein, we have developed a combination cancer therapy strategy by using polymer nanoparticles to deliver Gd-metallofullerenol and doxorubicin simultaneously. The Gd-metallofullerenol provoked the Th1 immune response by regulating the M1 macrophage polarization and the doxorubicin realized direct tumor cells killing by its cytotoxic effect. Also, the Gd-metallofullerenol as part of component in delivery system enhances the encapsulation efficiency of doxorubicin in polymer cargo for potential passive tumor target. The biocompatible and reliable method by combining nanoparticle-induced immune modulation and chemotherapy triggers systemic antitumor immune responses for the synergistic inhibition of tumor growth in vivo. The integration of Gd-metallofullerenol and doxorubicin with potentially complementary functions in one nanoplatform may provide new opportunities to improve cancer treatments.

Introduction

Treatment of solid tumors by chemotherapy is usually failed in clinical because of the low effectiveness and side effects of chemodrugs [1]. Recent years' success of cancer immunotherapy, including monoclonal antibodies, cancer vaccines, adoptive cancer therapy and immune checkpoint therapy, has revolutionized traditional cancer treatment [[2], [3], [4]]. Manipulating of immune response in the tumor microenvironment becomes a powerful method for cancer treatment. However, challenges still exist in cancer immunotherapy [5]. Conventional cancer immunotherapeutic drugs with specific proteins or small molecular, whose therapeutic effect varies greatly in different patients because of the tumor heterogeneity with different antigen expression levels [6]. Also, the main components of traditional immunotherapy usually lose their bioactivity or target and lead to fail in vivo [7]. Preliminary evidences indicated that there will be promising synergistic effects when combining other types of therapies with immunotherapy [[8], [9], [10]].

As is now principally recognized, nanoparticle-based drug delivery system has the capacity to improve cancer treatment by packaging and protecting chemodrugs, and delivering them to the target cells [11,12]. Polymer nanoparticles usually offer great advantages by delivering a higher concentration of chemodrugs to tumor microenvironment [13]. However, the encapsulation of some hydrophilic drugs in polymer carriers is still not up to scratch. Researchers have developed nanoscale liposomal polymeric gels co-delivery TGF-β inhibitor and immunostimulatory IL-2 to increase the survival of tumor-bearing mice [14]. Also, Toll-like-receptor-7 agonist and indocyanine green were co-encapsulated by traditional poly(lactic-co-glycolic) acid (PLGA) polymer cargo to generate immunological responses in tumor metastasis inhibition [15]. However, the chemotherapeutics seldom co-delivered with the immunomodulatory protein due to the intricacy of manipulating the different pharmacokinetics of small molecule and protein without external force.

Macrophage is a fundamental part of the innate immune defense mechanisms and an essential component of tumor microenvironment [16]. It can be characterized as pro-inflammatory M1 or anti-inflammatory M2 macrophage [17,18]. M1 macrophage secretes pro-inflammatory cytokines promote specific immunity to provoke antitumor immunity by inducing T cell recruitment and activation, while M2 macrophages produce anti-inflammatory cytokines which would support tumorigenesis [[19], [20], [21]]. Accumulating evidences have assumed that some specific nanoparticles, like iron oxide and polymer, have implication in macrophage polarization [[22], [23], [24]]. Fullerene derivatives, including fullerenol [C₆₀(OH)₂₂] and Gd-metallofullerenol [Gd@C₈₂(OH)₂₂], have also been reported as efficient immunoadjuvants for HIV-1 DNA vaccines and cancer therapeutic agents [25,26]. In our previous studies, Fullerene and its derivatives have been identified as imaging agents [27], metalloproteinase inhibitors [28] and radical scavengers [29]. Also, both fullerenol and Gd-metallofullerenol nanoparticles can arouse both strong immune responses and highly delivery capacity against malignant disease [30,31]. Nevertheless, the role of Gd-metallofullerenol mediated immune response in cancer treatment especially combining with chemodrugs is remained obscure.

Herein, we developed a co-delivery nanosystem which utilized PEG-PLGA polymer to envelop Gd-metallofullerenol and Dox drug that realized combined cancer treatment with chemo-toxic effect and immunomodulation. Via this elaborate design, the Dox treatment effectiveness was significantly enhanced in vivo. By regulating the ratio of M2 to M1 phenotype in tumor microenvironment, Gd-metallofullerenol nanoparticles achieved the immune modulation with potential anti-tumor activity and significantly improved the encapsulation efficiency of Dox in polymer cargo. Furthermore, the combined delivery of Dox and Gd-metallofullerenol attained synergistic anti-tumor effect of chemo-immunotherapy. Therefore, our strategy that combining Gd-metallofullerenol immune-provoking with chemotherapy will be benefit for improving the effectiveness of cancer therapy.