Abstract 178: Peptide nanofibers: targeted therapies for glioblastoma multiforme
Authors: Leite Diana M. , Zhu Rong , Barbu Eugen , Hinterdorfer Peter , Pilkington Geoffrey J. , Lalatsa Aikaterini 
Published: July 2017

Abstract
Glioblastoma multiforme (GBM) is a malignant brain tumor with poor prognosis due to tumor heterogeneity, poor drug blood-brain barrier (BBB) permeability and targeting. GBM biopsies indicated the overexpression of G-protein coupled receptors (GPCRs) that when activated by neuropeptide agonists result in an antiproliferative effect. However, translation of these neuropeptides into novel therapies for GBM is frustrated by their short half-life (&lt;5 minutes) and inability to cross the BBB. Here, we present a novel strategy based on the lipidization of peptide agonists which results in peptide amphiphiles able to self-assemble into nanofibers that can entrap brain impermeable drugs, possess an enhanced stability to enzymatic degradation, permeate across an all human in vitro BBB model and are able to target GBM cells resulting in a significant antiproliferative effect. Peptide amphiphiles were synthesized using solid-phase peptide synthesis and characterised using pyrene, thioflavin T, circular dichroism and transmission electron microscopy experiments. Nanofibers were loaded with brain impermeable cytotoxic drugs (e.g. paclitaxel) and their stability was studied in biological media (plasma, brain, liver and GBM cell lysates). BBB permeation was studied in an all human in vitro Transwell model. The antiproliferative effect of the nanofibers was evaluated on U-87 MG cells. Targeting of the nanofibers to the GPCR was evaluated using single-molecule force spectroscopy (SMFS). Peptide amphiphiles self-assemble into stable nanofibers at concentrations above 189 μM and are able to solubilize high amounts of paclitaxel (&gt;1.8 mg) ensuring that the resulting nanomedicine can be clinically translatable. Both unloaded- and paclitaxel loaded-nanofibers showed superior stability compared to the parent neuropeptide in the presence of plasma, brain, liver and cell homogenates (&gt;6-fold). Nanofibers elicited a strong antiproliferative effect (IC50: 5.06 μM) resulting in a cell cycle arrest at G2/M in a GPCR positive GBM cell line (U-87 MG). Loading paclitaxel (1nM) within the nanofibers resulted in a synergistic effect evidenced by a decrease in cell survival by 32%. Nanofibers counteracted the forskolin-induced increase of intracellular cAMP levels indicating that the GPCR is linked to the GαI protein known to mediate the antiproliferative effect on GBM. Confocal studies confirmed the internalization of the peptide while SMFS studies supported specific binding of the nanofibers to GPCR on U-87MG cell surface with equivalent binding probability to peptide agonists and increased residence time. Texas Red labelled nanofibers permeate across an in vitro BBB model enabling the permeation of paclitaxel (Papp: 8.45 x10-6 cm/s). Thus, described peptide nanofibers are a novel targeted nanomedicine for GBM therapy able to be clinically translated. In vivo proof of concept studies and pharmacokinetics are under way.
Citation Format: Diana M. Leite, Rong Zhu, Eugen Barbu, Peter Hinterdorfer, Geoffrey J. Pilkington, Aikaterini Lalatsa. Peptide nanofibers: targeted therapies for glioblastoma multiforme [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 178. doi:10.1158/1538-7445.AM2017-178