Multifunctional Liposomes Remodeling Tumor Immune Microenvironment For Tumor Chemoimmunotherapy

Immunotherapy has emerged as an effective clinical strategy for the treatment of cancer by initiating the tumor immune cycle to kill tumor cells.Many tumor cells are weakly immunogenic,resulting in the inability to activate the immune system to produce cytotoxic T lymphocytes,leaving the tumor tissue in a state of cold tumor.The chemotherapeutic drug Doxorubicin(DOX)not only kills tumor cells,but also causes tumor cell ICD and recruits immature DCs,which trigger their maturation.Resiquimod(R848),an agonist of Toll-like receptor 7/8(TLR7/8),which further trigger the maturation of DCs to activate T-cell responses that converting cold tumors to hot tumors.However,in the treatment of solid tumors,even though the ICD effect is induced,promoting the maturation of DCs and activating the T-cell response,the tumor immunosuppressive microenvironment prevents the generated T cells from infiltrating into the tumor.Among them,tumor-associated fibroblasts(CAFs)are the host cells that constitute the tumor microenvironment and the dense collagen and hyaluronic acid produced by them constitute a physical barrier to T cell infiltration.On the other hand,CAFs release a variety of immunosuppressive factors,such as TGF-β and VEGF-A,which recruit regulatory T cells(Tregs)and other immunosuppressive cells to affect occurrence,development and immunotherapy of tumors.In order to improve weak tumor immunogenicity and tumor immunosuppressive microenvironment,we prepared a p H-responsive nanoliposome(DP/R/L@Lip)containing losartan(LOS),immunoadjuvants R848 and small dendritic macromolecules loaded with DOX(DP).The liposome was accumulated into tumor tissue via EPR effect.Due to the stimulation of acid environment in tumor tissue,the nanocarrier disintegrated and small molecule LOS,immune adjuvant R848 and DP have been released.DP rely on their size advantages to penetrate into the depth of tumor tissue and be swallowed by tumor cells.Then,under the stimulation of reduced glutathione in tumor cells,DOX was released to promote the immunogenicity death of tumor cells and initiate the immune response of tumor tissues.At the same time,the T cell response was activated under the synergistic effect of the adjuvant R848,which was equivalent to the effect of an in situ vaccine,and further enhanced the immune response of tumor.Finally,LOS promotes the transformation of tumor tissue from immunosuppressive microenvironment to immunopotentiating microenvironment by reshaping CAFs,and removes the biological barrier of T cell infiltration and the activated T cells rapidly respond to immunopotentiating tumor microenvironment to play an anti-tumor role.First,the successful synthesis of DP nanoparticles was verified by 1H-NMR.The hydrated particle size of DP/R/L@Lip was 136 ± 10.4 nm,and the encapsulated drug was rapidly released at p H 6.5 and high GSH concentration.Next,cellular assays demonstrated that DP/R/L@Lip had the strongest penetration ability in tumor spheroids and induced immunogenic cell death in 4T1 cells,promoting the maturation of DCs.The induction success of CAFs was identified in vitro as well as the ability of LOS to inhibit the activity of CAFs was confirmed.Finally,the in situ mouse 4T1 breast cancer model was established,and the in vivo experimental results demonstrated that DP/R/L@Lip could induce the maximum immunogenic cell death,enhance the maturation of DCs,promote the infiltration of T cells,and improve the immunosuppressive microenvironment,thus having the optimal anti-tumor efficacy with the tumor suppression rate of 90.4 ± 7.07%.