DOI
https://doi.org/10.25772/V921-9C17
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-β1low epithelial cells, that can readily create small FN thin fibrils, while TGF-β1high 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-β1low 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