Application Of Multifunctional Nano-delivery System To Improve Tumor Microenvironment In Combined Therapy Of Melanom

Cancer has become the second greatest health threat among the world.Melanoma,which is highly malignant and easy to metastasize and gain drug resistance,cannot be eliminated by single therapy.Treatments combination of different forms of therapies can further improve the efficacy compared with single therapy.The nano-delivery system is an ideal platform for treatment integration.Using nanotechnology,different types of therapeutic drugs can be assembled into nanoparticles and generate multifunctional nanomaterials for tumor combination therapy.However,Tumor microenvironment(TME)induces immune escape because of its hypoxia and immunosuppression.Reversing TME is helpful to recruit and activate anti-tumor immune cells and enhance immune response.In this study,we investigated TMEremodeling strategies for improving immunotherapy based on nano-delivery systems,including:Immunogenic cell death(ICD)of tumor by chemotherapy and Photodynamic therapy(PDT)to transform "cold tumor" into immunogenic "hot tumor";as well as directly regulating intratumoral immune components(immune cells or cytokines).Firstly.we combined chemotherapy with PDT,TME and light dual responsive mitochondrial targeted prodrug nanoparticles(TPPAD NPs)were designed to deliver both DOX(a type of chemotherapy drugs),and PheoA(a type of photosensitizers),for enhancing the antitumor effect.TPPAD NPs,prepared through electrostatic interaction,could simultaneously deliver DOX and PheoA to the tumor site due to passive targeting effect.TPPAD NPs could release drugs in a designed mode with pH sensitivity and deliver drugs to the targeted organelle(mitochondria).With laser irradiation,the amount of High Mobility Group Protein B1(HMGB-1)and Adenosine triphosphate(ATP)released by TPPAD NPs group was significantly increased,indicating that TPPAD NP-based PDT could induce ICD of the tumor cells.The activation of DCs and the reversion of TME was confirmed by Transwell.The tumor-inhibition rates of DOX,TPPAD NPs without light irradiation,and TPPAD NPs with light irradiation were 13%,53%and 73%,respectively,indicating that combination treatments could inhibit the growth of melanoma in mice.TPPAN NP with pH sensitivity,which could target mitochondria and combine with PDT,appeared to be a simple but smart nano-delivery system.TME can inhibit the function of DCs.The efficacy of DC vaccine can be improved by increasing the maturity of DCs and the level of T helper cells 1(Thl).IL-12 makes DCs and T cells form a positive feedback loop,and obtains activated CD8+Tc and Th1 cells,which proliferate with the present of IL-2,thus enhancing the immune efficacy of tumor.Clinical use of cytokines alone has low efficiency and high toxicity.Above all,using nano-delivery system combined with DC vaccine and cytokine therapy can augment systemic antitumor immune reaction and improve the antitumor effect against melanoma.We proposed that DC vaccine modified with cytokine-loaded silica nanoparticles could synergize with immunotherapy.Firstly,IL-12 and IL-2 were successfully adsorbed into the as-synthesized mesoporous SiO2-NH2.IL-12 could help to construct a positive feedback circuit of DCs and T cells to activate CD8+Tc and Th1 cells,while IL-2 could promote the proliferation of activated T cells and enhance antitumor activity.The synthetic SiO2 was characterized by high cytokine loading capacity and entrapment efficiency(EE%)(EEIL-2%=99.6%and EEIL-12%=83.6%).Confocal laser scanning microscope showed,maleimide modified cytokine loaded SiO2 NPs,which were covalently grafted on the surface of mature DCs with no effect on the cell viability,could release cytokines around DCs.This strategy could not only minimize the systemic toxicity but increase the bioavailability of cytokines.Its long-term antitumor protection was further validated in B16 tumor-bearing mice model.To sum up,we developed two nano-delivery systems to modulate TME with enhanced efficacy and safety.We synergized chemotherapy and PDT,and cytokine loaded SiO2 NPs to transform DC vaccine for the synergistic immunotherapy of tumors,in order to guide the design of nano delivery systems for amplified effects of antitumor immunotherapy.