Doctoral Dissertation Defense

Elise Hoover

Biomedical Engineering

Committee Chair: Emily Day

Ammon Pinizzotto Biopharmaceutical Innovation Center, 140AB

Zoom: https://udel.zoom.us/j/92339827776

Zoom Password: nano

Title: Engineering Multimodal Nanoparticles to Combat Triple-Negative Breast Cancer

Abstract: 

Triple-negative breast cancer (TNBC) is an aggressive subtype of cancer that accounts
for about 15-20% of all breast cancer cases and has a poorer short-term prognosis when
compared to other subtypes. Many current chemotherapeutics used to treat TNBC are
nonspecific, and, therefore, cause off-target effects and fail to elicit a robust tumor
response, which results in higher mortality and recurrence rates. Targeted therapy enabled
by nanoparticle (NP)-based drug carriers may prove more effective against TNBC. One
promising target for TNBC is the Wnt pathway, which is a known developmental pathway
that encourages cell proliferation, migration, and cell fate determination and then
transitions to mostly stem cell maintenance in adults. Unfortunately, many cancers,
including TNBC, have found ways to upregulate the canonical, β-catenin dependent Wnt
pathway in order to promote cell proliferation, migration, chemoresistance, and other
oncogenic behaviors. Accordingly, Wnt hyperactivity is strongly correlated with recurrence
and metastasis. One method to both target and therapeutically manipulate TNBC cells is by
coating NPs with antibodies against Frizzled7 (FZD7) receptors in the Wnt pathway, which
are overexpressed in ~70% of TNBC cases but minimally expressed by other cells in the
body. When antibody nanoconjugates bind FZD7 receptors, it prevents their activation by
extracellular Wnt ligands, leading to downstream inhibition of the Wnt signaling pathway.
As TNBC lacks targeted treatment options, the ability to use FZD7-targeted NPs to
specifically target and eliminate TNBC cells is particularly appealing. This thesis develops
methods to coat NPs with FZD7 antibodies and demonstrates their utility in delivering
chemotherapeutic agents or small interfering ribonucleic acid (siRNA) therapeutics to TNBC
cells.
The first aim of this thesis focused on developing NPs coated with anti-FZD7 antibodies
and/or siRNA targeting β-catenin, a downstream protein in the Wnt pathway that is a key

mediator in TNBC’s oncogenesis. The goal of this aim was to investigate optimal parameters
for modifying the surface of poly(lactic-co-glycolic acid) (PLGA) NPs with either antibodies,
siRNA, or both. The second aim of this dissertation investigated the role of FZD7 targeting
on the delivery and efficacy of an encapsulated drug, doxorubicin (DOX). The ability of FZD7-targeted, DOX-loaded NPs to inhibit TNBC cell viability was evaluated in vitro and compared against the effects of DOX delivered freely or in non-targeted NPs. Finally, the third aim of this thesis utilized PLGA NPs to carry both FZD7 antibodies and β-catenin siRNAs to inhibit the Wnt pathway in TNBC cells at both the receptor and effector levels. The RNA
interference effects of this platform were assessed through in vitro assays that measured
TNBC cell viability, migration, drug resistance, and spheroid formation in response to
various treatments.
Collectively, this work demonstrates that antibody-modified polymer NPs can be
designed to target FZD7 receptors that are overexpressed on TNBC cells and provide specific
delivery of diverse therapeutic cargo including chemotherapeutics and siRNAs. Future
research in this field should continue to tailor NP design parameters to achieve optimal
efficacy and safety and validate therapeutic potential in in vivo models of TNBC.