TLR7/8 Agonist Loaded Metal-Organic Framework Nanoparticles Inducing Cell Pyroptosis And Augmented Anti-Tumor Immunotherapy

Cancer treatment has always been a major problem in the medical community,especially breast cancer,which has overtaken lung cancer as the highest incidence of cancer in the world.At present,traditional methods of surgery,chemotherapy and radiotherapy are difficult to eradicate the lesion,leaving them vulnerable to recurrence after surgery.Many new treatments have been developed as technology has advanced,including chemodynamic,photodynamic therapy,photothermal therapy,gene therapy and immunotherapy.Chemodynamic(CDT)refers to in-situ therapies that use Fenton or Fenton-like reactions to produce reactive oxygen species(ROS)in the weakly acidic conditions in tumors.ROS produced by CDT in tumor tissues can be used to activate NLRP3 and release activated caspase-1 to induce pyroptosis.Pyroptosis,a novel immune-related programmed death mode(PCD),is capable of releasing tumor-associated antigens and damage-associated molecular patterns(DAMPs),inducing immunogenic cell death(ICD),promoting DC cell maturation to initiate anti-tumor immune response and inhibit tumor growth.However,pyroptosis,as a mode of pro-inflammatory cell death,with the increase of IL-1β activation,would amplify the inflammatory response and form a tumor inflammatory microenvironment,providing a favourable setting for tumor growth and leading to tumor proliferation,invasion,metastasis,angiogenesis and immune escape.As an immune adjuvant,R848 not only stimulate immune system,but also regulate immunosuppressive cells and reshape immunosuppressive tumor microenvironment by "turning enemy into friend".By combining pyroptosis with immune adjuvant R848,loaded R848 can synergistically boost DC cell maturation while also downregulate immunosuppressive cells(MDSCs and M2 macrophages)to improve the immunosuppressive microenvironment.The combination of the two can not only enhance the anti-tumor effect,but it can also trigger strong innate and adaptive antitumor immunity at the same time to amplify the killing effect on tumor cells,leading to the elimination of tumor cells.Based on this,we designed an acid-reactive organometallic nanodrug delivery system FeMn@R@H.To form FeMn@R nanoparticles,R848,a proven anti-tumor immunomodulator,was loaded with FeMn nanoorganometallic skeletons.FeMn@R was crosslinked with HA to form FeMn@R@H nanoparticles,which was a uniform rhomboidal negative charge structure with a particle size of 190.8 nm and had good stability in vitro.In addition,it can produce ROS in a responsive manner in acidic tumor environment.The cytotoxicity and function of 4T1 breast cancer cells were studied.The results show that the endocytosis of FeMn@R@H is time-dependent,and ROS generation can be induced through Chemodynamic in cells to activate NLRP3 inflammator-mediated pyroptosis,resulting in cell swelling and rupture,release of cell contents(LDH).At the same time,the release of DAMPs induces ICD effect to produce powerful killing effect on tumor cells.Subsequently,a 4T1 breast cancer model was established in Balb/c mice to evalute the antitumor efficacy and antitumor immune effect of FeMn@R@H in vivo.The results showed that FeMn@R@H could effectively reach the tumor site and achieve tumor killing in tumor-bearing mice.Furthermore,in vivo ICD effect studies and immunological analysis confirmed that FeMn@R@H can enhance immune response and promote tumor inhibitory effect by combining pyroptosis and anti-tumor immunotherapy to promote DC maturation,polarize immunosuppressive cells MDSCs and TAM,and reduce the frequency of immunosuppressive cells(MDSCs and M2 macrophages).