Date of Graduation

5-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Biomedical Engineering

Advisor/Mentor

Muldoon, Timothy J.

Committee Member

Erf, Gisela F.

Second Committee Member

Quinn, Kyle P.

Third Committee Member

Rajaram, Narasimhan

Fourth Committee Member

Song, Young Hye

Keywords

Cancer Biology; Macrophages; Metabolism

Abstract

Macrophages are a subset of immune cells with a variety of functions that are abundant in numerous tumor types such as colorectal and breast cancer. It has been suggested that macrophages may serve an important function as immune mediators in tumor behavior; however, macrophage activity is complex and remains not completely understood. The overall goal of this dissertation was to explore and exploit tumor-associated macrophage phagocytic function and the changes in their interactions with cancer cells in an in vitro mouse model and in 2D and 3D in vitro culture models. First, we wanted to better understand macrophage behavior under the various polarization states through longitudinal monitoring of metabolic and phagocytic effects of a murine macrophage cell line after exposure to various cytokine stimuli. Overall, the results of these studies indicate that autofluorescence imaging of endogenous metabolic cofactors can be a reliable method for monitoring the temporal and spatial dynamics of macrophage metabolism as they undergo activation after stimulation with cytokines as well as performing functions such as phagocytosis. Next, we created a 3D in vitro culture model that accurately resembled a 3D solid tumor while creating a novel analysis method to evaluate changes in multicellular spheroid structure and metabolism across spheroid micro-regions. Overall, the results of this study show that 3D multicellular spheroid models can provide a reliable solution for studying tumor biology, allowing for the evaluation of discrete changes across all spheroid microregions. Finally, we used the multicellular spheroid model as a preclinical model to test the effects of various therapeutic regimens (chemotherapy, immune checkpoint inhibitors, and phagocytosis checkpoints) to increase clinical understanding of combined regimens to off-set the side effects of traditional chemotherapy while stimulating immunogenic cell death. Results show that the combination of two immune checkpoint inhibitors in addition to a chemotherapy agent reduced spheroid growth (~46%), and reduced M2 macrophage expression and cellular proliferation while modulating cellular metabolism, ICD hallmarks, and phagocytic function. Overall, this study not only quantified microregional metabolic and structural changes in a simulated spheroid model but also quantified changes in ICD hallmarks and macrophage functional behavior. It was also found that relationships between spheroid structure and ICD hallmarks could exist after exposure to the combinatory regimen of immune checkpoint inhibitors and an ICD inducer.

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Available for download on Wednesday, June 17, 2026

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