Date of Award

2020

Embargo Period

8-14-2025

Document Type

Thesis - MUSC Only

Degree Name

Master of Biomedical Science

Department

Cell and Molecular Pharmacology and Experimental Therapeutics

College

College of Graduate Studies

First Advisor

Danyelle Townsend

Second Advisor

Kenneth D. Tew

Third Advisor

Steven A. Rosenzweig

Fourth Advisor

Robin C. Muise-Helmericks

Abstract

Tumor heterogeneity, including metabolic heterogeneity, is a major challenge to developing effective anticancer therapeutics. Alterations in metabolism and mitochondrial bioenergetics are one of the emerging hallmarks of cancer. Much cancer research has been devoted to the Warburg effect (increase of aerobic glycolysis), increased reliance on glutamine, and the lipogenic phenotype (increase in fatty acid synthesis). Recently fatty acid oxidation (FAO) has gained more attention as a potential target for chemotherapeutics. Carnitine palmitoyltransferase 1 (CPT1) is a key regulator of mitochondrial FAO and its enzymatic activity is responsible for allowing fatty acids into the mitochondria to be oxidized. All other respiratory substrates, including pyruvate from glycolysis and glutamine, as well as ADP/ATP, enter mitochondria through the Voltage Dependent Anion Channel (VDAC). Once inside mitochondria, these fuels are catabolized to generate mitochondrial membrane potential (ΔΨm) which drives ATP formation. This thesis focuses on mitochondrial ΔΨm as an observably heterogeneous facet of mitochondrial metabolism and explores some possible mechanisms underlying ΔΨm heterogeneity, with a focus on FA oxidation in HepG2 cells, a hepatocellular carcinoma cell line. Data presented within suggests that ΔΨm heterogeneity is independent of heterogeneity of plasma membrane potential and phase of the cell cycle. In a single cell transcriptomics study, cells with high ΔΨm were found to have higher expression of genes associated with FAO, including CPT1A, while genes associated with glycolysis, glutaminolysis, and de novo FA synthesis were unchanged. In a separate qPCR study on cells sorted by low or high ΔΨm using flow cytometry, higher CPT1A gene expression was observed in cells with higher ΔΨm., though the difference was not statistically significant. The hypothesis proposed herein is that some cancer cells preferentially utilize FAs over glucose and glutamine for mitochondrial ATP generation and thus maintain a higher ΔΨm by higher levels of mitochondrial FAO. This differential utilization could be regulated not only by higher expression of CPT1A, but higher amount of interaction between CPT1 and VDAC through VDAC-CPT1-ACSL complexes. The third chapter proposes how to test this hypothesis to determine how upregulation of mitochondrial FA oxidation by CPT1 may contribute to metabolic heterogeneity in cancer.

Rights

All rights reserved. Copyright is held by the author.

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Available for download on Thursday, August 14, 2025

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