Research On Hydrogel That Regulates CXCL10 Degradation And Immune Checkpoint For Enhanced Tumor Immunotherapy

In recent years,the immunotherapy method of eliminating tumors by activating T cells is promising.Although cytotoxic T cells are potent against tumor cells,the clinical efficacy of this therapy remains low due to insufficient T cell infiltration in tumors.CXCL10 is a kind of chemokine capable of recruiting T cells and promoting T cell infiltration at tumor sites.However,in vivo CXCL10 can be truncated by the catalysis of dipeptidyl peptidase 4(DPP4),resulting in the loss of CXCL10 activity.Thus,modulation of DPP4 activity is expected to solve the problem of the short half-life of CXCL10.In addition to insufficient T cell infiltration,immune escape due to programmed cell death ligand 1(PD-L1)overexpression on tumor cells significantly inhibits T-cell killing.Based on the above problems,an innovative injectable hydrogel preparation was constructed in this topic.Sodium alginate(SA),which is biocompatible and calcium ions(Ca2+)responsive to the tumor environment,was used as a gel agent,linagliptin was used as a DPP4 inhibitor,and BMS-202 was used as a PD-L1 blocker to construct SA@linagliptin/BMS-202(S@LB)injectable hydrogel,which was combined with CXCL10 to enhance the immune effect of T cells.The physicochemical properties of the preparation were characterized,and its anti-tumor effect was investigated at the cellular and animal levels.The main research content of this topic is as follows:1.S@LB injectable hydrogel was prepared.The needle penetration and gel formation in vitro and in vivo were evaluated.Scanning electron microscope(SEM)observation of the S@LB hydrogel microstructure showed its uniform porous structure,which was conducive to the storage and sustained release of drug molecules.Linagliptin and BMS-202 were encapsulated in the micropores of the hydrogel in the form of particles.2.The role of S@LB at the cellular level was verified using mouse melanoma cell B16F10 as a model.Qualitative and quantitative analysis of PD-L1 on the surface of B16F10 cells showed that S@LB could successfully block extracellular PD-L1 and reverse the immunosuppression caused by PD-L1.The results of qualitative and quantitative analysis of intracellular Ca2+showed that sodium alginate could chelate Ca2+ which was helpful to reduce the supply of PD-L1 from intracellular to extracellular,and played a synergistic role with BMS-202 in cells.3.The anti-tumor effect of S@LB was further verified in mice bearing B16F10 cells.The enzyme activity experiment demonstrated that S@LB had the ability to inhibit DPP4,and the content of CXCL10 in tumor tissues was increased by 56.40%after treatment with S@LB+CXCL10.The increased number of tumor-infiltrating T cells and PD-L1 blockade were further validated using flow cytometry and immunofluorescence imaging.S@LB combined with CXCL10 not only can effectively inhibit the primary tumors,but also produced effective inhibition of the distant tumors.At the same time,it had a good anti-lung metastasis effect and promoted the generation of immune memory effect in vivo.In conclusion,we have designed an injectable hydrogel to facilitate the recruitment of T cells as well as PD-L1 blockade for cancer immunotherapy.Linagliptin and BMS-202 were present as particles in the hydrogel micropores after gelation at the tumor site using SA as the gelating agent.Linagliptin could effectively inhibit DPP4 activity,thereby increasing the content of CXCL10 in the tumor microenvironment and enhancing the recruitment ability of CXCL10 to achieve potent T cell infiltration.Meanwhile,BMS-202 could block PD-L1 and attenuate PD-L1-mediated immune escape of tumor cells.In addition,the combination of hydrogel and CXCL10 showed a potent immunotherapy effect on both primary and distant tumors,and effectively inhibited lung metastasis.We propose a tumor immunotherapy modality that centers around the recruitment of T cells and amplifies their efficacy,providing a novel simple and effective strategy for anti-tumor therapy.