Construction And Antitumor Study Of Polymer Nanovaccine-based Combination Immunotherapy

Tumor is becoming more aggressive in the recent years and seriously threatens people’s life and health.It has been the central theme to develop the novel and effective antitumor therapies.Unlike the traditional therapies,tumor immunotherapy mainly activates patients’ own immune system to fight against tumor cells,having gained the most attention nowadays.Among them,tumor vaccines have been extensively explored owing to their high specificity,low costs and relatively low side effects.However,the current clinical trials of tumor vaccines often showed limited efficacy due to the poor T cell responses in vivo and the tumor suppressive microenvironments.Thus,this study has focused on these two key problems to improve the efficacy of the tumor vaccines.On the one hand,we introduced the polymeric carriers to develop the tumor nanovaccines and "in situ vaccines"for the T cell responses enhancement.On the other hand,the various strategies were combined to regulate the tumor suppressive microenvironment,aiming to achieve the synergistic antitumor outcomes.According to the aforementioned studies,we firstly designed the tumor nanovaccines and ECM scavenger combined two-barreled strategy.Next,to achieve personalized immunotherapy,we developed the tumor "in situ vaccines" and local mild heat combined integrative two-barreled treatments.Furthermore,to enhance the antitumor efficacy,we further combined PD pathway blockade to explore the three-barreled immunological strategy and realize the superior antitumor effect in vivo at final.Firstly,to induce the robust T cell responses,we designed a "minimalist" tumor nanovaccines.The negative charged CaCO3 was absorbed with positive charged PEI through simple electrostatic interactions to form a dual-functional vaccine carrier PEI/CaCO3.Subsequently,the antigen OVA and adjuvant CpG were directly absorbed onto PEI/CaCO3 particles to prepare PEI/CaCO3/OVA/CpG nanovaccines(NVs).PEI/CaCO3 could not only act as a vaccine carrier that robustly enhanced the cellular uptake of OVA and CpG,but also worked as an underlying adjuvant to activate BMDCs.Therefore,the formed NVs realized the significant enhancement of both the BMDCs activation and the specific responses of T cells in vivo.In addition,to regulate the immunosuppressive microenvironment,we further combined the gene-mediated ECM scavenger,which was realized by developing the pH responsive pSpam1@NPs to achieve a high HAase expression within tumors.Thus,the HAase further degraded the ECM to not only promote the infiltration of immune cells,but also relieve the tumor hypoxia to modulate the immunosuppressive microenvironment.Finally,highly enhanced antitumor efficacy and tumor re-challenge prevention were achieved by such two-barreled strategy in B16F10-OVA bearing mice.To achieve personalized immunotherapy and avoid the complicated process for the identification and prediction of tumor specific antigens,we further developed the"in situ tumor vaccines".By encapsulating two chemo drugs,mitoxantrone(MTO)and gambogic acid(GA)into PLG-g-mPEG via electrostatic interactions and hydrophobic stack to form nanomicelle MG@NNPs,which elicited tumors immunogenic cell death,thus translating the tumor cells into in situ vaccines to activate the immune systems.Furthermore,to reverse the tumor suppressive microenvironment,we utilized photothermal behavior of MG@NPs to generate mild heat(43℃)within tumors under manually controlled NIR irradiation,which was verified to enhance the blood vessels and relieve tumor hypoxia to further regulate the MDSCs infiltration and the TAMs polarization.Such facile nanodrugs provided an ambidextrous approach to combine tumor "in situ vaccines" and local mild heat to realize the personalize immunotherapy.Finally,this integrative two-barreled strategy achieved the robust local and systemic antitumor immune responses to control both local and abscopal 4T1 tumors growth.Following the integrative two-barreled treatments,we observed the obvious enhanced PD-L1 expression within tumors.Therefore,to overcome the immunologic tolerance induced by PD-L1 upregulation and improve the antitumor outcomes,we further combined anti-PD-L1 therapy to develop the three-barreled strategy for tumor inhibition.At final,we proved that "in situ vaccines" and local mild heat treatments could provide an immune supportive microenvironment to boost anti-PD-L1 therapy for synergistic suppression of advanced 4T1 tumors,not only through promoting the primary responses but also inhibiting the adaptive resistance to anti-PD therapy for tumor relapse prevention.This study might improve the applicability of tumor vaccines,and offer a new concept for the development of the clinical tumor vaccine-based combined therapies.