Ph.D Thesis


Ph.D StudentYael Lupu
SubjectElucidating the Mechanism of Interactions of Nano-Ghosts
with the Tumor Niche
DepartmentDepartment of Biotechnology and Food Engineering
Supervisor Full Professors Machluf Marcelle


Abstract

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Drug delivery systems are being developed in order to overcome various barriers in cancer treatment. The overall aim of these systems is to balance between the toxicities and side effects of anti-cancer therapeutics and their efficacy. However, delivery systems developed till today still fail to achieve this delicate balance, due to lack of specificity. Most delivery systems rely on passive targeting, the enhanced permeability and retention effect at the tumor. Current studies attempt to increase specificity by active targeting methods. However, all actively targeted platforms developed till today did not introduce a significant and valuable benefit to the traditional passively targeted systems. Other approaches explored for cancer treatment use geneticaly engineered mesenchymal stem cells (MSCs). MSCs have unique immunological properties and show selective migration towards sites of cancer, putting them in the focus of many studies which demonstrated their ability to serve as targeted delivery vehicles for gene and drug delivery1-3.

In our lab we have developed a new targeted delivery system for cancer therapy which is composed from the cell membrane of MSCs. We have produced cell derived vesicles, which are termed nano-ghosts (NGs), that present the surface molecules of the MSCs. We hypothesize that these NGs are naturally designed to interact with tumor cells by virtue of the proteins presereved on their surface. Therefore, the main goal of the present research was to study and characterize the interactions of the NGs with the tumor. In the current research, NGs were produced by a modified methodology and were characterized for their physical and biological characteristics. NGs were found to be spherical, nano-sized vesicles partly preserving MSCs common markers including many adhesion molecules. In-vitro, NGs were non-cytotoxic with higher uptake by cancer cells compared to primary endothelial cells, proving their selectivity. NGs ability to deliver different active agents (sTRAIL, EDTA) was used to prove that NGs interactions with cancer cells are surface interactions leading to further internalization by fusion and energy dependent endocytosis. NGs-cell interactions were also shown to be partly mediated by integrins, specifically integrin β1 and intra-cellular adhesion molecule-1 (ICAM-1). In addition, stimulation of the MSCs prior to NGs production increased cancer cellar uptake and resulted in a different uptake by cells of the tumor niche that could enable more specific tumor targeting. In-vivo studies with a murine model demonstrated that IP administrated NGs had lower bioavailability compared to IV administrated NGs and that stimulation by pro-inflammatory cytokines significantly increased the tumor targeting of the NGs. However, in the in-vivo scenery, integrins were shown to be more involved in NGs-extracellular matrix interactions rather than in NGs-cancer cell interactions.

By elucidating the mechanism of interactions between NGs and cancer cells, including other cells in the tumor niche, we proved the ability of the NGs to deliver drugs targeting intra- and extra-cellular compartments. Understanding the effect of stimulation of the MSCs prior to NGs production and identifying specific targeting moieties will allow us better programing of our NGs targeting abilities towards more specific compartments of the tumor niche.