Structure-function analysis of the glioma targeting NFL-TBS.40-63 peptide corresponding to the tubulin-binding site on the light neurofilament subunit

Glioblastoma-targeted, local and sustained drug delivery system based on an unconventional lipid nanocapsule hydrogel

The objective of this work was to develop an implantable therapeutic hydrogel that will ensure continuity in treatment between surgery and radiochemotherapy for patients with glioblastoma (GBM). A hydrogel of self-associated gemcitabine-loaded lipid nanocapsules (LNC) has shown therapeutic efficacy in vivo in murine GBM resection models. To improve the targeting of GBM cells, the NFL-TBS.40-63 peptide (NFL), was associated with LNC. The LNC-based hydrogels were formulated with the NFL. The peptide was totally and instantaneously adsorbed at the LNC surface, without modifying the hydrogel mechanical properties, and remained adsorbed to the LNC surface after the hydrogel dissolution. In vitro studies on GBM cell lines showed a faster internalization of the LNC and enhanced cytotoxicity, in the presence of NFL. Finally, in vivo studies in the murine GBM resection model proved that the gemcitabine-loaded LNC with adsorbed NFL could target the non-resected GBM cells and significantly delay or even inhibit the apparition of recurrences.

Cell penetrating peptide (CPP) gold(iii) - complex - bioconjugates: from chemical design to interaction with cancer cells for nanomedicine applications

This study promotes an innovative synthesis of a nanotheragnostic scaffold capable of targeting and destroying pancreatic cancer cells (PDAC) using the Biotinylated NFL-TBS.40-63 peptide (BIOT-NFL), known to enter various glioblastoma cancer cells (GBM) where it specifically destroys their microtubule network. This recently proposed methodology (P7391FR00-50481 LIV) applied to other peptides VIM (Vimentin) and TAT (Twin-Arginine Translocation) (CPP peptides) has many advantages, such as targeted selective internalization and high stability under experimental conditions, modulated by steric and chemical configurations of peptides. The successful interaction of peptides on gold surfaces has been confirmed by UV-visible, dynamic light scattering (DLS), Zeta potential (ZP) and Raman spectroscopy analyses. The cellular internalization in pancreatic ductal adenocarcinoma (PDAC; MIA PACA-2) and GBM (F98) cells was monitored by transmission electron microscopy (TEM) and showed a better cellular internalization in the presence of peptides with gold nanoparticles. In this work, we also evaluated the power of these hybrid peptide-nanoparticles as photothermal agents after cancer cell internalization. These findings envisage novel perspectives for the development of high peptide-nanotheragnostics.

Characterization of Biological Material Adsorption to the Surface of Nanoparticles without a Prior Separation Step: a Case Study of Glioblastoma-Targeting Peptide and Lipid Nanocapsules

Purpose

Current preclinical therapeutic strategies involving nanomedicine require increasingly sophisticated nanosystems and the characterization of the complexity of such nanoassemblies is becoming a major issue. Accurate characterization is often the factor that can accelerate the translational approaches of nanomedicines and their pharmaceutical development to reach the clinic faster. We conducted a case study involving the adsorption of the NFL-TBS.40–63 (NFL) peptide (derived from neurofilaments) to the surface of lipid nanocapsules (LNCs) (a combined nanosystem used to target glioblastoma cells) to develop an analytical approach combining the separation and the quantification in a single step, leading to the characterization of the proportion of free peptide and thus the proportion of peptide adsorbed to the lipid nanocapsule surface.

Methods

LNC suspensions, NFL peptide solution and LNC/NFL peptide mixtures were characterized using a Size-Exclusion Chromatography method (with a chromatographic apparatus). In addition, this method was compared to centrifugal-filtration devices, currently used in literature for this case study.

Results

Combining the steps for separation and characterization in one single sequence improved the accuracy and robustness of the data and led to reproducible results. Moreover the data deviation observed for the centrifugal-filtration devices demonstrated the limits for this increasingly used characterization approach, explained by the poor separation quality and highlighting the importance for the method optimization. The high potential of the technique was shown, proving that H-bond and/or electrostatic interactions mediate adsorption of the NFL peptide to the surface of LNCs.

Conclusions

Used only as a characterization tool, the process using chromatographic apparatus is less time and solvent consuming than classical Size-Exclusion Chromatography columns only used for separation. It could be a promising tool for the scientific community for characterizing the interactions of other combinations of nanosystems and active biological agents.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11095-021-03034-8.

Lipid Nanoparticles Vectorized with NFL-TBS.40-63 Peptide Target Oligodendrocytes and Promote Neurotrophin-3 Effects After Demyelination In Vitro

Promoting remyelination in multiple sclerosis is important to prevent axon degeneration, given the lack of curative treatment. Although some growth factors improve this repair, unspecific delivery to cells and potential side effects limit their therapeutic use. Thus, NFL-TBS.40-63 peptide (NFL)-known to enter specifically myelinating oligodendrocytes (OL)-was used to vectorize 100 nm diameter lipid nanoparticles (LNC), and the ability of NFL-LNC to specifically target OL from newborn rat brain was assessed in vitro. Specific uptake of DiD-labeled NFL-LNC by OL characterized by CNP and myelin basic protein was observed by confocal microscopy, as well as DiD colocalization with NFL and with Rab5-a marker of early endosomes. Unvectorized LNC did not significantly penetrate OL and there was no uptake of NFL-LNC by astrocytes. Canonical maturation of OL which extended compacted myelin-like membranes was observed by transmission electron microscopy in cells grown up to 9 days with NFL-LNC. Endocytosis of NFL-LNC appeared to depend on several pathways, as demonstrated by inhibitors. In addition, vectorized NFL-LNC adsorbed on neurotrophin-3 (NT-3) potentiated the proremyelinating effects of NT-3 after demyelination by lysophosphatidyl choline, allowing noticeably decreasing NT-3 concentration. Our results if they were confirmed in vivo suggest that NFL-vectorized LNC appear safe and could be considered as putative carriers for specific drug delivery to OL in order to increase remyelination.

The neurofilament derived-peptide NFL-TBS.40-63 enters in-vitro in human neural stem cells and increases their differentiation

Regenerative medicine is a promising approach to treat neurodegenerative diseases by replacing degenerating cells like neurons or oligodendrocytes. Targeting human neural stem cells directly in the brain is a big challenge in such a strategy. The neurofilament derived NFL-TBS.40-63 peptide has recently been introduced as a novel tool to target neural stem cells. Previous studies showed that this peptide can be internalized by rat neural stem cells in vitro and in vivo, which coincided with lower proliferation and self-renewal capacity and increase of differentiation. In this study, we analyzed the uptake and potential effects of the NFL-TBS.40-63 peptide on human neural stem cells isolated from human fetuses. We showed that the peptide inhibits proliferation and the ability to produce neurospheres in vitro, which is consistent with an increase in cell adhesion and differentiation. These results confirm that the peptide could be a promising molecule to target and manipulate human neural stem cells and thus could serve as a strategic tool for regenerative medicine.

Enhanced and preferential internalization of lipid nanocapsules into human glioblastoma cells: effect of a surface-functionalizing NFL peptide

Increasing intracellular drug concentration using nanocarriers can be a potential strategy to improve efficacy against glioblastoma (GBM). Here, the fluorescent-labelled NFL-TBS·40-63 peptide (fluoNFL) concentration on a lipid nanocapsule (LNC) was studied to enhance nanovector internalization into human GBM cells. LNC surface-functionalization with various fluoNFL concentrations was performed by adsorption. LNC size and surface charge altered gradually with increasing peptide concentration, but their complement protein consumption remained low. Desorption of fluoNFL from the LNC surface was found to be slow. Furthermore, it was observed that the rate and extent of LNC internalization in the U87MG human glioblastoma cells were dependent on the surface-functionalizing fluoNFL concentration. In addition, we showed that the uptake of fluoNFL-functionalized LNCs was preferential towards U87MG cells compared to healthy human astrocytes. The fluoNFL-functionalized LNC internalization into the U87MG cells was energy-dependent and occurred possibly by macropinocytosis and clathrin-mediated and caveolin-mediated endocytosis. A new ferrocifen-type molecule (FcTriOH), as a potent anticancer candidate, was then encapsulated in the LNCs and the functionalization improved its in vitro efficacy compared to other tested formulations against U87MG cells. In the preliminary study, on subcutaneous human GBM tumor model in nude mice, a significant reduction of relative tumor volume was observed at one week after the second intravenous injection with FcTriOH-loaded LNCs. These results showed that enhancing NFL peptide concentration on the LNC surface is a promising approach for increased and preferential nanocarrier internalization into human GBM cells, and the FcTriOH-loaded LNCs are a promising therapy approach for GBM.

The Neurofilament-Derived Peptide NFL-TBS.40-63 Targets Neural Stem Cells and Affects Their Properties

Targeting neural stem cells (NSCs) in the adult brain represents a promising approach for developing new regenerative strategies, because these cells can proliferate, self-renew, and differentiate into new neurons, astrocytes, and oligodendrocytes. Previous work showed that the NFL-TBS.40-63 peptide, corresponding to the sequence of a tubulin-binding site on neurofilaments, can target glioblastoma cells, where it disrupts their microtubules and inhibits their proliferation. We show that this peptide targets NSCs in vitro and in vivo when injected into the cerebrospinal fluid. Although neurosphere formation was not altered by the peptide, the NSC self-renewal capacity and proliferation were reduced and were associated with increased adhesion and differentiation. These results indicate that the NFL-TBS.40-63 peptide represents a new molecular tool to target NSCs to develop new strategies for regenerative medicine and the treatment of brain tumors.

SIGNIFICANCE

In the present study, the NFL-TBS.40-63 peptide targeted neural stem cells in vitro when isolated from the subventricular zone and in vivo when injected into the cerebrospinal fluid present in the lateral ventricle. The in vitro formation of neurospheres was not altered by the peptide; however, at a high concentration of the peptide, the neural stem cell (NSC) self-renewal capacity and proliferation were reduced and associated with increased adhesion and differentiation. These results indicate that the NFL-TBS.40-63 peptide represents a new molecular tool to target NSCs to develop new strategies for regenerative medicine and the treatment of brain tumors.

Roles and potential clinical applications of intermediate filament proteins in brain tumors

Intermediate filament (IF) proteins are cytoplasmic and nuclear cytoskeletal proteins. Of the ~70 IF proteins, nearly 12 are found in the nervous system, where their expression is largely cell-type specific. Astrocytes express glial fibrillary acidic protein (GFAP), whereas different neuron types contain neurofilament proteins, α-internexin, or peripherin. These proteins are often downregulated in brain cancer. In addition, brain cancer cells may also contain vimentin, nestin, and synemin, which are the IF proteins found in neural progenitor cells. In different brain tumor types, the expression of nestin, vimentin, and α-internexin appears to correlate with the clinical outcome. Experimental investigations have also demonstrated that IF proteins have distinct roles in specific brain tumor cell behaviors: nestin, for instance, is important for the proliferation of glioma cells, whereas synemin also affect their mobility. The mechanisms responsible for these effects involve the interaction of IF proteins with specific signaling pathways. Synemin, for instance, positively regulates glioma cell proliferation by antagonizing protein phosphatase 2A. Further evidence for the potential of IF proteins as therapeutic targets derives from animal models showing the influence of IF proteins on tumor growth. Nestin downregulation, for instance, dramatically reduced intracerebral glioma growth. Selective targeted therapies of IFs to date primarily include gene therapy approaches using nestin or GFAP gene promoters to drive transgene expression into glioma cells. Although attempts to identify small molecules specifically antagonizing IF proteins have been unsuccessful to date, it is anticipated that the identification of such compounds will be instrumental in expanding therapeutic approaches for brain tumors.

De novo peptide structure prediction: an overview

Peptide structure identification is an important contribution to the further characterization of the residues involved in functional interactions. De novo structure peptide prediction has, in the past few years, made significant progresses that make reasonable, for peptides up to 50 amino acids, its use for the fast identification of their structural topologies. Here, we introduce some of the concepts underlying approaches of the field, together with their limits.

The OPEP protein model: from single molecules, amyloid formation, crowding and hydrodynamics to DNA/RNA systems

The OPEP coarse-grained protein model has been applied to a wide range of applications since its first release 15 years ago. The model, which combines energetic and structural accuracy and chemical specificity, allows the study of single protein properties, DNA-RNA complexes, amyloid fibril formation and protein suspensions in a crowded environment. Here we first review the current state of the model and the most exciting applications using advanced conformational sampling methods. We then present the current limitations and a perspective on the ongoing developments.

The NFL-TBS.40-63 anti-glioblastoma peptide enters selectively in glioma cells by endocytosis

Glioblastoma are the most frequent and aggressive tumour of the nervous system despite surgical resection associated with chemotherapy and radiotherapy. Recently, we showed that the NFL-TBS.40-63 peptide corresponding to the sequence of a tubulin-binding site of neurofilaments, enters selectively in glioblastoma cells where it blocks microtubule polymerization, inhibits their proliferation, and reduces tumour development in rats bearing glioblastoma (Bocquet et al., 2009; Berges et al., 2012a). Here, we characterized the molecular mechanism responsible for the uptake of NFL-TBS.40-63 peptide by glioblastoma cells. Unlike other cell penetrating peptides (CPPs), which use a balance between endocytosis and direct translocation, the NFL-TBS.40-63 peptide is unable to translocate directly through the membrane when incubated with giant plasma membrane vesicles. Then, using a panel of markers and inhibitors, flow cytometry and confocal microscopy investigations showed that the uptake occurs mainly through endocytosis. Moreover, glycosaminoglycans and αVβ3 integrins are not involved in the NFL-TBS.40-63 peptide recognition and internalization by glioblastoma cells. Finally, the signalling of tyrosine kinase receptors is involved in the peptide uptake, especially via EGFR overexpressed in tumour cells, indicating that the uptake of NFL-TBS.40-63 peptide by glioblastoma cells is related to their abnormally high proliferative activity.