Metal-Organic Framework-Based Scaffold Vaccines For Reinforced Colorectal Cancer Immunotherapy

Objective:Cancer immunotherapy opens up a new avenue for cancer therapy via orchestrating the patient’s immune system to activate specific antitumor responses.Among them,cancer vaccines have been vigorously developed due to their unique advantages of easy large-scale production and good safety.However,limited lymph node（LN）transport and antigen cross-presentation result in suboptimal antitumor T cell responses,severely dampening their clinical transformation.Therefore,there is an urgent need to develop an efficient vaccine delivery system.Biomaterials are widely used in vaccine delivery by using personalized designs for tailor-made immune responses.In contrast with nanovaccines that are highly dependent on LN transport and enrichment,scaffold vaccines can not only be regarded as"one-shot"treatment to improve patient compliance,but also form an in situ immune niche for dendritic cell（DC）spatiotemporal modulation（recruitment,activation,and LN migration）.Metal-organic framework（MOF）not only own unique advantages of molecular modularity,structural tenability,and intrinsic porosity,but also release metal ions that can be used as adjuvants for immune activation,providing more possibilities for scaffold vaccines.Although MOF microscale scaffolds are expected to improve LN transport and antigen cross-presentation,antigen molecules are easily degraded by lysosomal proteases in DCs,greatly impairing cross-presentation efficiency.Recent studies have shown that Ythdf1 enhances antigen degradation and limits antigen cross-presentation in lysosomes by promoting the translation of m6A-modified cathepsin m RNA.Therefore,Ythdf1 can be used as a potential target to enhance the cross-presentation of antigens.Based on this,we developed a microscale bimetallic manganese/zirconium-MOF loaded with Ythdf1-targeted biomimetic nanovaccines for boosting DC modulation and cross-presentation,expecting for reinforced colorectal cancer immunotherapy.Methods:To prepare scaffold vaccines with certain biological stability,a microscale Zr-MOF was synthesized by a hydrothermal method using porphyrin ligand and zirconium dichlorooxide,and then Zr-MOF was transformed into Mn/Zr-MOF via metal ion exchange reaction.Meanwhile,a plasmid encoding short hair-pinned RNA against Ythdf1（shY1）was constructed.Sh Y1 was blended with liposome-decorated tumor cell membranes,self-assembled,and repeatedly squeezed to form Ythdf1-targeted biomimetic nanovaccine（shY1-CM）.Finally,Mn/Zr-MOF absorbed shY1-CM by electrostatic adsorption or van der Waals forces,obtaining MOF-based scaffold vaccine（Mn/Zr-MOF-shY1-CM）.We evaluated the physicochemical properties of the scaffold vaccine through a series of experiments to explore the antitumor response and mechanism in vivo and in vitro.Results:The microscale MOF-based scaffold vaccine with certain biological stability and sustainable drug release was successfully constructed.The scaffold vaccine was self-assembled and stacked in situ to form a three-dimensional immune niche,and completed the spatiotemporal DC modulation,including recruitment（especially DC1 subtype）,activation,and lymph node migration.Sh Y1-CM downregulated the expression of Ythdf1 in DC,reduced lysosomal cathepsin activity,and promoted antigen cross-presentation.Meanwhile,Mn/Zr-MOF sustainably released Mn²⁺,activated c Gas-Sting signaling pathway,triggering enhanced anti-tumor responses.In animal models,the scaffold vaccine effectively prevented the occurrence of melanoma and colorectal cancer,and significantly inhibited the recurrence and metastasis of colorectal cancer after surgery.Furthermore,strong immune memory responses generated by the scaffold vaccine suppresses metachronous colorectal cancer liver metastasis.Conclusions:In this study,a microscale bimetallic manganese/zirconium-MOF loaded with Ythdf1-targeted biomimetic nanovaccines（Mn/Zr-MOF-shY1-CM）was successfully constructed,which effectively promoted the spatialtemporal regulation and antigen cross-presentation of DC.In animal models,the vaccine exhibited robust and versatile immunoprevention efficacy against tumors and synergized with immune checkpoint blockade（ICB）immunotherapy for suppressing postoperative CRC relapse.Furthermore,strong immune memory responses generated by Mn/Zr-MOF-shY1-CM/ICB eradicated metachronous colorectal cancer liver metastasis.Collectively,this approach presented a versatile and efficacious platform for developing personalized scaffold vaccines.