Advisory Committee Chair
Mk Sewell-Loftin
Advisory Committee Members
Jennifer Pollock
Jillian Richter
Palaniappan Sethu
Renata Jaskula-Sztul
Document Type
Dissertation
Date of Award
1-1-2025
Degree Name by School
Doctor of Philosophy (PhD) School of Engineering
Abstract
Cancer progression relies on blood vessel growth; without vasculature, tumors would be limited to less than 200µm in diameter. With this reasoning, several cancer therapies have been developed that target the process of angiogenesis, or the growth of vessels off pre-existing vasculature. These treatments target the major promoters of angiogenesis, vascular endothelial growth factor (VEGF) and VEGF receptor 2 (VEGFR-2); however, anti-angiogenic therapies are not effective by themselves. This is likely due to mechanoactivation of VEGFR-2 through physical alterations in the tumor microenvironment (TME). One prevalent mechanical change is increased strain on surrounding cells and matrix due to highly contractile cancer-associated fibroblasts (CAFs) present in the TME. In this project, we applied strain to endothelial cells (ECs) through a 2D Flexcell system or in 3D through CAFs or magnetic beads. This allowed us to determine the molecular and functional effects of strain on ECs in the context of angiogenesis in the TME. For molecular studies, we focused on VEGFR-2 expression and phosphorylation at Y1054/Y1059 and Y1214. We observed that the application of 2D strain caused increased phosphorylation of both sites, indicating activation of the VEGFR-2 pathway. To further study the roles of these residues, we developed EC CRISPR/Cas9 mutants with Y1054 or Y1214 being changed to phenylalanine (Y1054F, Y1214F), which is not phosphorylatable. We discovered that in 3D microtissue studies, these mutant ECs developed significantly less vasculature compared to control lines. Our functional studies utilized three-chamber microfluidic devices to analyze angiogenesis, and we determined that cell-free strain through embedded magnetic beds promoted angiogenesis, which result was lost in Y1054F and Y1214F lines. Through this project, we demonstrate that strain can cause VEGFR-2 phosphorylation, which is likely the cause of increased angiogenesis. Y1054 and Y1214 are both required for normal vessel growth, suggesting potential targets of future cancer treatments. Tumor mechanics should be taken into consideration when developing novel anti-angiogenic therapies due to mechanoactivation of the VEGFR-2 pathway which may overcome common treatments used today.
Recommended Citation
Johnson, Bronte, "Mechanoactivation of VEGFR-2 Promotes Angiogenesis in the Tumor Microenvironment" (2025). All ETDs from UAB. 6850.
https://digitalcommons.library.uab.edu/etd-collection/6850
Comments
etdadmin_upload_1134413