INGR-modified Liposomes For Tumor Vascular Targeting And Tumor Tissue Penetrating Delivery In The Treatment Of Glioblastoma

The anti-tumor effect of active targeting nano drug delivery system has been hampered by the tumor vascular barrier and tumor stroma barrier during the in vivo delivery.In this study,to overcome the two barriers,we used iNGR,a tumor-penetrating peptide,to modify the liposomes to increase their accumulation and penetration in tumor tissues.The structure of iNGR was composed of a vascular homing motif,a tissue penetration motif(R/KXXR/K),and a protease recognition site[1].For one thing,it can specifically recognize tumor blood vessels mediated by the receptor CD 13,which is over-expressed on the neovascular endothelial cells of glioma,especially in the pathological state.For another,it can be cut by specific enzyme near the tumor into iNGRt peptide(CRNGR sequence),which can specifically penetrate through tumor vessels and into the deep tumor tissues and be internalized by glioblastoma cells.This function is based on the specific interaction between iNGRt and its receptor NRP-1 overexpressed on the tumor vessels and glioblastoma cells[2].Therefore,the tumor vessel targeting and tumor penetrating ability may allow iNGR to be able to overcome the tumor vascular barrier and tumor stroma barrier.Firstly,iNGR-modified liposomes(iNGR-LS)were prepared in this work,which showed vesicle sizes of around 100 nm and narrow size distribution.iNGR-LS exhibited remarkably increased cellular internalization by U87MG tumor cells and HUVECs(Human Umbilical Vein Endothelial Cells)than unmodified liposomes(LS)as evidenced by the cellular uptake test.The in vivo imaging study confirmed that iNGR modification significantly increased the liposome accumulation in subcutaneous tumor tissues of animal model.The immunofluorescence staining analysis proved that iNGR-LS could penetrate through tumor blood vessels and into the deep tumor tissues.The cytotoxicity of iNGR-modified doxorubicin-loaded liposomes(iNGR-LS/DOX)on U87MG and HUVECs cells in vitro was considerably increased compared with that of unmodified doxorubicin-loaded liposomes(LS/DOX).The iNGR-LS/DOX also showed significantly(p<0.05)stronger growth inhibitory effect on tumor than LS/DOX,which should be attributed to the increased tumor accumulation and penetration mediated by iNGR.This study proved that iNGR peptides modification may be an effective strategy for improving the transport of liposomes in tumor tissue and enhancing their anti-tumor effect.