Mingfei Zhang

A stapled peptide antagonist of MDM2 carried by polymeric micelles sensitizes glioblastoma to temozolomide treatment through p53 activation.

Antagonizing MDM2 and MDMX to activate the tumor suppressor protein p53 is an attractive therapeutic paradigm for the treatment of glioblastoma multiforme (GBM). However, challenges remain with respect to the poor ability of p53 activators to efficiently cross the blood-brain barrier and/or blood-brain tumor barrier and to specifically target tumor cells. To circumvent these problems, we developed a cyclic RGD peptide-conjugated poly(ethylene glycol)-co-poly(lactic acid) polymeric micelle (RGD-M) that carried a stapled peptide antagonist of both MDM2 and MDMX (sPMI). The peptide-carrying micelle RGD-M/sPMI was prepared via film-hydration method with high encapsulation efficiency and loading capacity as well as ideal size distribution. Micelle encapsulation dramatically increased the solubility of sPMI, thus alleviating its serum sequestration. In vitro studies showed that RGD-M/sPMI efficiently inhibited the proliferation of glioma cells in the presence of serum by activating the p53 signaling pathway. Further, RGD-M/sPMI exerted potent tumor growth inhibitory activity against human glioblastoma in nude mouse xenograft models. Importantly, the combination of RGD-M/sPMI and temozolomide--a standard chemotherapy drug for GBM increased antitumor efficacy against glioblastoma in experimental animals. Our results validate a combination therapy using p53 activators with temozolomide as a more effective treatment for GBM.

Stapled RGD Peptide Enables Glioma-Targeted Drug Delivery by Overcoming Multiple Barriers

Malignant glioma, the most frequent and aggressive central nervous system (CNS) tumor, severely threatens human health. One reason for its poor prognosis and short survival is the presence of the blood-brain barrier (BBB) and blood-brain tumor barrier (BBTB), which restrict the penetration of therapeutics into the brain at different stages of glioma. Herein, inspired by the peptide stapling technique, we designed a cyclic RGD ligand via an all-hydrocarbon staple (stapled RGD, sRGD) to facilitate BBB penetration while retaining the capacity of BBTB penetration and targeting ability to glioma cells. As expected, sRGD-modified micelles were able to penetrate the in vitro BBB model while retaining the glioma targeted capability. The results of the in vivo imaging studies further revealed that this nanocarrier could not only efficiently transverse the intact BBB of normal mice, but also could specifically target glioma cells of intracranial glioma-bearing nude mice. Furthermore, Paclitaxel-loaded sRGD-modified micelles exhibited improved antiglioma efficacy in vitro and significantly prolonged survival time of glioma-bearing nude mice. Overall, this sRGD peptide showed potency for glioma-targeted drug delivery by overcoming multiple barriers.

Glioma-Targeted Drug Delivery Enabled by a Multifunctional Peptide

The rapid proliferation of glioma relies on vigorous angiogenesis for the supply of essential nutrients; thus, a radical method of antiglioma therapy should include blocking tumor neovasculature formation. A phage display selected heptapeptide, the glioma-initiating cell peptide GICP, was previously reported as a ligand of VAV3 protein (a Rho GTPase guanine nucleotide exchange factor), which is overexpressed on glioma cells and tumor neovasculature. Therefore, GICP holds potential for the multifunctional targeting of glioma (tumor cells and neovasculature). We developed GICP-modified micelle-based paclitaxel delivery systems for antiglioma therapy in vitro and in vivo. GICP and GICP-modified PEG-PLA micelles (GICP-PEG-PLA) could be significantly taken up by U87MG cells, a human cell line derived from malignant gliomas and human umbilical vein endothelial cells (HUVECs). Furthermore, GICP-PEG-PLA micelles demonstrated enhanced penetration in a tumor spheroid model in vitro in comparison to unmodified micelles. In vivo, DiR-loaded GICP-PEG-PLA micelles exhibited superior accumulation in the tumor region by targeting neovasculature and glioma cells in nude mice bearing subcutaneous glioma. When loaded with paclitaxel, GICP-PEG-PLA micelles could more effectively suppress tumor growth and neovasculature formation than unmodified micelles in vivo. Our results indicated that GICP could serve as a promising multifunctional ligand for glioma targeting.

Enhanced Glioblastoma Targeting Ability of Carfilzomib Enabled by a DA7R-Modified Lipid Nanodisk

The robust proliferation of tumors relies on a rich neovasculature for nutrient supplies. Therefore, a basic strategy of tumor targeting therapy should include not only killing regular cancer cells but also blocking tumor neovasculature. D-peptide DA7R, which was previously reported to specifically bind vascular endothelial growth factor receptor 2 (VEGFR2) and neuropilin-1 (NRP-1), could achieve the goal of multitarget recognition. Accordingly, the main purposes of this work were to establish a carfilzomib-loaded lipid nanodisk modified with multifunctional peptide DA7R (DA7R-ND/CFZ) and to evaluate its anti-glioblastoma efficacy in vitro and in vivo. It is testified that the DA7R peptide-conjugated lipid nanodisk can be specifically taken up by U87MG cells and HUVECs. Furthermore, DA7R-ND demonstrated a more enhanced penetration than that of the nonmodified formulation on the tumor spheroid model in vitro and more tumor region accumulation in vivo on the subcutaneous and intracranial tumor-bearing nude mice model. DA7R-ND was shown to co-localize with tumor neovasculature in vivo. When loaded with proteasome inhibitor carfilzomib, the DA7R-decorated nanodisk could remarkably suppress tumor proliferation, extend survival time of nude mice bearing an intracranial tumor, and inhibit neovasculature formation with an efficacy higher than that of the nonmodified nanodisk in vitro and in vivo. The present study verified that the heptapeptide DA7R-conjugated nanodisk is a promising nanocarrier for glioblastoma targeting therapy.

A novel peptide ligand RAP12 of LRP1 for glioma targeted drug delivery

ABSTRACT The receptor associated protein (RAP) is a 39kDa chaperone protein, binding tightly to low‐density lipoprotein receptor‐related protein‐1 (LRP1) that is overexpressed in glioma, tumor neovasculature, vasculogenic mimicry (VM), the blood–brain barrier (BBB) and the blood–brain tumor barrier (BBTB). Herein, we miniaturized the RAP protein into a short peptide RAP12 (EAKIEKHNHYQK) aiding by computer‐aided peptide design technique. RAP12 contained the essential lysines at the positions 253 and 256. The binding affinity of RAP12 to LRP1 was theoretically and experimentally evaluated. In cellular level, RAP12 could effectively internalize into U87, HUVEC and bEnd.3 cells. When modified on the surface of PEG–PLA micelles (RAP12‐PEG–PLA), RAP12 could effectively facilitate the penetration of micelles through the BBB/BBTB in vitro/vivo. Paclitaxel‐loaded RAP12‐PEG–PLA could remarkably inhibit the growth of glioma cells and the formation of tumor neovasculature and VM, significantly prolong the median survival time of nude mice bearing intracranial glioma in comparison to model mice treated with plain micelles or Taxol. These results suggested that the RAP12 held the potential for multifunctional glioma‐targeted drug delivery.

Nanodisk-based glioma-targeted drug delivery enabled by a stable glycopeptide

ABSTRACT Heptapeptide ATWLPPR (A7R) binds specifically to vascular endothelial growth factor receptor 2 (VEGFR2) and neuropilin‐1 (NRP‐1) overexpressed in glioma cells, exhibiting high potential to achieve glioma targeted drug delivery. However, in vivo application of A7R peptide remains challenging due to the poor proteolytic stability and inaccessibility of A7R to the brain. To tackle these problems, we identified a glycosylated A7R derivative to enhance in vivo stability and brain transport efficacy. Our results showed that glycosylation of peptide could efficiently improve stability in serum, traverse the blood‐brain barrier (BBB) and be uptaken by glioma cells. Furthermore, a novel glioma‐targeted drug delivery system was constructed successfully employing glycopeptide as the targeting moiety and nanodisk as the carrier of paclitaxel (PTX). Physicochemical characterization showed that the nanodisk presented suitable size of 50 nm and adequate loading capacity of PTX. Compared to non‐glycosylated nanodisk, glycopeptide modification could significantly enhance the uptake of disks by brain capillary endothelial cells through glucose transporter 1 (GLUT1). In vivo imaging and glioma fluorescence section results also indicated that nanodisks modified with glycopeptide showed a higher accumulation in glioma. The glycopeptide‐enabled PTX delivery system exhibited superior anti‐glioma efficacy in intracranial glioma xenograft model. These results suggested that glycosylation of peptides provided an efficient pathway to design multifunctional and stable brain targeting ligands. Graphical abstract Figure. No caption available.

Myristic Acid-Modified DA7R Peptide for Whole-Process Glioma-Targeted Drug Delivery

The clinical treatment of aggressive glioma has been a great challenge, mainly because of the complexity of the glioma microenvironment and the existence of the blood-brain tumor barrier (BBTB)/blood-brain barrier (BBB), which severely hampers the effective accumulation of most therapeutic agents in the glioma region. Additionally, vasculogenic mimicry (VM), angiogenesis, and glioma stem cells (GSC) in malignant glioma also lead to the failure of clinical therapy. To address the aforementioned issues, a whole-process glioma-targeted drug delivery strategy was proposed. The DA7R peptide has effective BBTB-penetrating and notable glioma-, angiogenesis-, and VM-targeting abilities. Herein, we designed a myristic acid modified DA7R ligand (MC-DA7R), which combines tumor-homing DA7R with BBB-penetrable MC. MC-DA7R was then immobilized to PEGylated liposomes (MC-DA7R-LS) to form a whole-process glioma-targeting system. MC-DA7R-LS exhibited exceptional internalization in glioma, tumor neovascular, and brain capillary endothelial cells. Enhanced BBTB- and BBB-traversing efficiencies were also observed on MC-DA7R-LS. Ex vivo imaging on brain tumors also demonstrated the feasibility of MC-DA7R-LS in intracranial glioma-homing, whereas the immunofluorescence studies demonstrated its GSC and angiogenesis homing. Furthermore, doxorubicin-loaded MC-DA7R-LS accomplished a remarkable therapeutic outcome, as a result of a synergistic improvement on the glioma microenvironment. Our study highlights the potential of the MC-modified DA7R peptide as a great candidate for the whole-process glioma-targeted drug delivery.