Dissertation Defense, Joshua Greenlee, Biomedical Engineering
DISSERTATION DEFENSE
Joshua Dale Greenlee, Biomedical Engineering
*under the direction of Dr. Michael King
“TRAIL Therapy for Exploiting Mechanisms of Drug Resistance and Metastasis in Advanced Colorectal Cancer”
02.23.23 | 9:30am | Light Hall 208 | Zoom
Colorectal cancer (CRC) is the second leading cause of cancer death in the United States, accounting for over 55,000 deaths in 2022. The primary cause of death in CRC is due to metastasis, the process in which cancer cells disseminate and colonize secondary sites in the body. Patients with metastatic CRC have only a 15% 5-year survival, making it one of the most lethal metastatic cancers. This emphasizes the need for more effective anti-metastatic treatments beyond frontline chemotherapy. Tumor Necrosis Factor-alpha related apoptosis inducing ligand (TRAIL) is a protein that initiates apoptosis (programmed cell death) in cells via the binding of transmembrane death receptors. Previous studies have demonstrated TRAIL’s ability to selectively kill cancer cells while sparing healthy cells. This dissertation investigates the use of TRAIL and TRAIL-conjugated nanoparticles as treatments for metastatic CRC. The first part of this dissertation presents the discovery that CRC cells resistant to oxaliplatin chemotherapy become more sensitive to TRAIL-mediated cell death, an unexpected observation. This increased sensitivity is due to augmented death receptor 4 (DR4) localization within tightly packed, cholesterol-enriched regions in the cell membrane known as lipid rafts. This mechanism of DR4 translocation into lipid rafts within oxaliplatin-resistant cells is discovered to be through increased palmitoylation of DR4. Using this knowledge, blood samples from metastatic oxaliplatin-resistant CRC patients were treated with TRAIL-conjugated liposomes, reducing circulating tumor cell viability by 57%. The second part of this work found that metastatic cells are more resistant to fluid shear stress-mediated effects than cells isolated from the primary tumor of the same patient. Additionally, activation of the mechanosensitive ion channel Piezo1 sensitizes CRC cells to TRAIL-mediated cell death via the influx of calcium. The final part of this dissertation establishes a syngeneic orthotopic mouse model of CRC metastasis, laying the groundwork for future in vivo treatment studies with TRAIL-conjugated liposomes. Overall, the studies within this dissertation provide evidence that TRAIL and TRAIL-conjugated nanoparticles can be used to kill chemoresistant and metastatic cancer cells in static environments and the circulation, prompting further preclinical studies.