Development of a Polymeric Nanoparticle Formulation to Overcome Multidrug Resistance of Cancer via a Multifunctional Therapy

Student: Lilian van Vlerken
Department: Pharmaceutical Sciences
Advisor: Mansoor Amiji

Abstract

Figure 1: Localization of nanoparticles inside cells.

Nanotechnology is a very useful tool in the design of drug delivery systems to combat many diseases, where these nano-platforms can aide in target specific localization, controlled release, and multifunctionalization of the therapy. The use of nanoparticles, colloidal carriers of submicronic (<1 ï¿m) size is particularly of use in the delivery of therapeutics to tumors. Resulting from the rapid growth of a tumor mass, many tumors present with fenestrated vasculature and poor lymphatic drainage, resulting in an enhanced permeability and retention (EPR) effect. Long circulating nanoparticles can extravasate through these fenestrations to accumulate, and deposit their drug load, specifically at the tumor site.

Figure 2: Occurance of apoptosis in MDR breast cancer cells, previously resistant to cell death, with experimental therapy.

A great challenge to cancer therapy is the development of cross-resistance to a multitude of chemotherapeutic agents, termed multidrug resistance (MDR). It is believed that the development of MDR in a small subset of cancer cells is the reason for tumor survival despite invasive chemotherapy, a phenomenon that is particularly taxing in the treatment of breast and ovarian cancer, where MDR develops in half of the clinical cases. Although MDR is known to arise through alterations of several cellular processes in the cancer cell, recent research suggests the importance of alterations in apoptotic (programmed cell death) signaling, rendering the MDR cell impervious to cell death resulting from chemotherapy. This project is aimed at overcoming MDR through a therapeutic strategy that uses polymeric nanoparticles to carry and co-administer an MDR modulator, involved in mending the alterations in apoptotic signaling, with a classical chemotherapeutic to re-sensitize MDR cancers to chemotherapy.

Objective: The development of multidrug resistance (MDR) in many tumor types is a major barrier to successful anti-cancer therapy. One of the mechanisms that leads to such chemoresistance is inhibition of apoptotic signaling in MDR cancer cells through glycosylation of the apoptotic mediator ceramide. The purpose of this study was to investigate whether MDR could be reverted by co-administering exogenous C6-ceramide with a chemotherapeutic (paclitaxel), co-encapsulated in polymeric nanoparticles to produce a multifunctional anticancer therapy.

Experimental Methods: The experimental approach involved testing efficacy of the therapeutic strategy by quantifiying % cell death of drug sensitive vs. multidrug resistant cancer cells in response to the nanoparticle treatment compared to conventional treatments. Next, apoptotic activity in response to paclitaxel/ceramide co-therapy was quantified using a commercially available apoptosis assay. Lastly, intracellular nanoparticle accumulation and localization was observed by fluorescent microscopy.

Results: Results indicate that nanoparticle delivery of the co-therapy reduces chemoresistance of the MDR cells to paclitaxel 100-fold, to produce a chemosensitivity profile in the MDR cells that is similar to their drug-sensitive counterpart cell-line. Co-therapy of ceramide with paclitaxel appeared to increase apoptotic activity 2 fold in the MDR cells, suggesting that delivery of exogenous ceramide reinstates the apoptotic signal to resensitize MDR cells to chemotherapy.

Conclusions: Altogether, co-administering paclitaxel with ceramide, delivered in polymeric nanoparticles appears to greatly re-sensitize drug resistant ovarian tumor cells to chemotherapy. The results demonstrate the great potential for clinical use of this therapeutic strategy to overcome MDR.