Investigating the Regulation of Epithelial-Mesenchymal Transition through Fibronectin-Mediated TGF-β1 Mechanotransduction using in vitro models of Triple-Negative Breast Cancer

Author

Michael M. Sofroniou, Virginia Commonwealth UniversityFollow

Author ORCID Identifier

https://orcid.org/0000-0002-9380-5806

Defense Date

2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Biomedical Engineering

First Advisor

Christopher A. Lemmon, Ph.D.

Second Advisor

Rebecca L. Heise, Ph.D.

Third Advisor

Paula D. Bos, Ph.D.

Fourth Advisor

Priscilla Y. Hwang, Ph.D.

Fifth Advisor

Gregory S. Walsh, Ph.D.

Abstract

TGF-β1 is a potent regulator of epithelial-mesenchymal transtion (EMT), a cellular
transdifferentation process that promotes cellular motility and matrix remodeling, critical to tumorigenesis and metastasis. TGF-β1-induced EMT promotes the assembly of FN, which synergistically binds latent TGF-β1 to aid in its activation. The purpose of of this work is to further probe the effects of autocrine TGF-β1 signaling during EMT progression by utilizing CRISPR-Cas9 deletion of the TGFB1 gene in in vitro models of triple-negative breast cancer. The studies outlined in this work demonstrate that autocrine TGF-β1 maintains a baseline level of mesenchymal marker expression. It also functions to desensitize TGF-β receptors, reducing their capacity to signal from sharp, excessive boluses of active TGF-β1, while still
potentiating further TGF-β1 signaling for EMT progression. We also highlight a a key
difference in FN assembly capacity across malignancy, with TGF-β1^low epithelial cells, that can readily create small FN thin fibrils, while TGF-β1^high TNBC cells, which secrete higher levels of FN, do not assemble them into FN matrices nearly as readily. Autocrine TGF-β1 is critical for the assembly of FN fibrils, particularly in TGF-β1^low epithelial cells. Wedemonstrate that even empty LAP, the complex used to hold the TGF-β1 dimer latent in the ECM, has the ability to induce some degree of FN assembly. Lastly, through extended EMT-induction, we demonstrate how TGF-β1 is critical for the irreversible commitment to a mesenchymal phenotype. The body of this details the just how tightly autocrine TGF-β1 regulates EMT-associated processes, but also highlights an important facet of growth-factor signaling regulation by the ECM. Future experimentation to more thoroughly understand the growth-factor-ECM signaling axes will help inform the identification of future targets for therapeutic intervention, not only in triple-negative breast cancer, but in a host of other
solid tumors and and fibrotic disease states.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

5-7-2024