Inducement Of Anti-Melanoma Growth And Metastasis And Immune Response By Tumor Polypeptide Loaded Thin Shell Hollow Mesoporous Silica Nanoparticles

[Background]Malignant melanoma is a highly malignant and lethal tumor.Tumor polypeptide vaccine of melanoma is an immunotherapy method with strong specificity and low side effects,but the vaccine composed of melanoma related antigen alone is not stable enough in vivo,the phagocytosis of antigen-presenting cells is not enough,and the anti-tumor immune response is not strong.Using nanoparticles as both carrier and adjuvant to deliver tumor antigen may be a very promising method.NPs can improve the stability of polypeptide antigen in vivo and increase the phagocytosis of antigen by antigen presentation cells.At the same time,some NPs have been proved to have adjuvant effect and can nonspecifically improve the anti-tumor immune response of antigen.Therefore,the application of NPs will be a very promising strategy and method in the future to achieve anti-melanoma through improving immunity.Hollow mesoporous silica nanoparticles is a kind of nanoparticles with high safety and confirmed to have a certain immune adjuvant effect.The research shows that hollow mesoporous silica has better immune adjuvant effect than solid mesoporous silica.However,the immune response rate of existing HMSNs is still very low for anti-tumor immune response.[Objective]This study intends to further prepare tthin shell HMSNs by polyethyleneimine etching method both as nano carrier and adjuvant of melanoma antigen,so as to ensure higher biosafety and obtain higher specific anti-tumor immune response level.[Methods]1.THMSNs were prepared by PEI etching method and characterized.We encapsulated Trp2 with THMSNs to prepare melanoma polypeptide vaccine(Trp2@THMSNs).The drug loading efficiency and drug release curve were studied.The in vitro and in vivo biocompatibility of Trp2@THMSNs were evaluated.2.The phagocytosis efficiency of DCs was studied.Further,we studied the maturation of DCs,the proliferation and activation of T cells and the level of memory immunity,induced by Trp2@THMSNs.3.We used Trp2@THMSNs and TAA@THMSNs to investigate the antitumor effects of tumor in the in situ tumor model and the tumor recurrence and metastasis model,respectively.[Results]1.We successfully synthesized THMSNs by PEI etching method.Compared with HMSNs,THMSNs have thinner wall thickness,positive charge,better antigen loading ability and more lasting antigen release ability,and THMSNs show good biosafety in vivo and in vitro.2.Compared with HMSNs,THMSNs can promote the phagocytosis of melanoma antigen by DCs,the maturation level of DCs in vivo and in vitro,and the proliferation and activation of T cells in vivo.The content of PEI and the thinner shell stucture both contributed to the enhancement of adjuvant effect of THMSNs.3.In the orthotopic tumor model,THMSNs loaded melanoma specific antigen(Trp2)can significantly inhibit the occurrence and development of melanoma.Also,the proportion of IFN-γ~+in CD3~+CD4~+T cells in spleen and tumor of mice of Trp2@THMSNs was significantly higher than that of other groups,which further verified the antitumor adjuvant effect of THMSNs.In the tumor recurrence and metastasis model,HMSNs loaded melanoma whole antigen(TAA)can significantly inhibit the recurrence and metastasis of melamoma.The levels of memory cells in CD4~+and CD8~+T cells in TAA-THMSNs group were significantly increased.[Conclusions]In summary,PEI incorporated THMSNs with thin shell hollow mesoporous structure have been successfully fabricated and demonstrated as promising antigen vehicles with improved adjuvant effect for cancer vaccines.Overall,THMSNs which have no significant side effects,have been proved to remarkably enhance anti-cancer immune responses and are believed to be great hopeful vehicles and adjuvants in the formation of cancer vaccines.