Date of Award

12-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Bioengineering

Committee Member

Jeoung Soo Lee

Committee Member

Frank Alexis

Committee Member

Wen Chen

Committee Member

Wendy Cornett

Committee Member

Matt Gevaert

Abstract

Breast cancer is the most common malignancy and the leading cause of cancer death in women. Systemic breast cancer therapies include 1) hormone therapy, 2) immunotherapy, and 3) chemotherapy. Chemotherapy is commonly used in combination with immunotherapy, achieving synergistic activity by multiple mechanisms specific to the type of breast cancer. However, the efficacy of anticancer drugs has been limited by their toxic side effects in normal cells and drug resistance acquired by cancer cells. Therefore, the development of a novel treatment strategy for the selective delivery of therapeutic agents to breast cancer cells is crucial to improve the therapeutic index and efficacy/toxicity balance. The objective of this project is to develop multi-functional polymeric nanotherapeutics for breast cancer therapy that specifically target malignant cells and provide combinatorial delivery of an anticancer drug and therapeutic nucleic acid designed to reduce the expression of proteins responsible for drug resistance. These multi-functional polymeric nanotherapeutics will consist of three functional components 1) folate (FA) as a targeting moiety to deliver these nanotherapeutics to FA receptor alpha-positive breast cancer cells (FA receptor is over-expressed in 32% of breast cancers), 2) small interfering RNA (siRNA) designed against multidrug resistant protein (ABCB1), a gene responsible for drug resistance in cancer cells, and 3) the chemotherapeutic, Doxorubicin (DOX). The efficacy of these targeted multifunctional nanotherapeutics will be evaluated in FA-receptor alpha positive (FA+) drug resistant breast cancer cells.

To achieve this goal, FA-functionalized polymeric micelle nanoparticles, folate-polyethylenimine-graft-poly (lactide-co-glycolide) (FA-PgP) were designed as a targeted drug and nucleic acid delivery carrier. We synthesized and characterized FA-PgP and demonstrated that the FA-PgP polymeric micelle is a promising carrier for plasmid DNA capable of transfecting breast cancer (MCF-7, MDA-MB-435 Wild Type, and MDA-MB-435 DOX resistant) cells in media containing 10% serum. We also demonstrated that FA-PgP exhibited selectivity by comparing transfection efficiencies in folate receptor alpha positive (MCF-7, MDA-MB-435 Wild Type, and MDA-MB-435 DOX resistant) and negative breast cancer cell lines (MDA-MB-468) in vitro and demonstrated that PgP can deliver pGFP (plasmid encoding green fluorescence protein) and pbGal (plasmid encoding beta- galactosidase gene) as reporter genes efficiently in an athymic Nu/Nu mouse drug resistant breast tumor model. Finally, Doxorubicin loaded FA-PgP was able to induce increased or similar cytotoxicity compared its free drug counterpart in MCF-7 and MDA-MB-435 DOX resistant lines and over a LD50 response in MDA-MB-468 and MDA-MB-435 Wild Type cells. Furthermore, FA-PgP exhibited FA+ related selectivity in all breast cancer cell lines tested. Future work includes utilizing therapeutic siRNAs targeting ABCB1 with FA-PgP to overcome drug resistance in breast cancers.

Available for download on Friday, May 01, 2020

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