Date of Graduation

12-2019

Document Type

Thesis

Degree Name

Master of Science in Biomedical Engineering (MSBME)

Degree Level

Graduate

Department

Biomedical Engineering

Advisor/Mentor

Rajaram, Narasimhan

Committee Member

Quinn, Kyle P.

Second Committee Member

Muldoon, Timothy J.

Keywords

Cancer; Imaging; Metabolism

Abstract

Twist transcription factor is often overexpressed in aggressive tumors. Although needed in early embryonic development for organogenesis, Twist is known to induce an epithelial to mesenchymal transition in cells. In cancer, epithelial to mesenchymal transitions can lead to increased motility and invasiveness. It has also been linked to metabolic reprogramming and increased metastatic risk. Furthermore, metabolic preferences can increase proliferation, enhance metastatic potential, and influence the site of metastasis. We hypothesize that Twist directly affects the metabolism of cancer cells. We expect to see in vivo what we have seen in vitro; Twist overexpression should promote a shift away from glycolysis in response to reperfusion.

To study the effects of Twist on metabolism in vivo tumors were grown in the dorsal skinfold window chamber and stressed by exposure to hypoxia. Knowledge of metabolism without information on the oxygen availability is incomplete because cell metabolism naturally shifts between oxidative phosphorylation and glycolysis in response to variations in oxygen availability. Knowing if oxygen is readily available is particularly important when studying cancer metabolism because tumors may have poor vasculature organization due to angiogenesis not keeping up with tumor growth. To know if metabolic changes are due to intrinsic or extrinsic factors hyperspectral imaging was used to determine vascular oxygenation within the tumor. Multiphoton microscopy was used to quantify metabolism on the cellular level by measuring the optical redox ratio as well as the relative contribution ratio of free and bound NADH.

We found the optical redox ratio, vascular oxygenation, and hemoglobin concentration were affected more by hypoxia in the cell line not expressing Twist. This would suggest that Twist does have a direct impact on metabolism within the cell. Because multiphoton imaging was not performed during hypoxia, whether Twist causes quicker metabolic changes or causes resistance to metabolic change remains to be determined.

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