Investigating Epigenetic Regulation in Obesity-Associated, Lipogenic Triple Negative Breast Cancer Open Access
Townsel-Kelly, Ashley (Fall 2025)
Abstract
Triple Negative Breast Cancer (TNBC) is the most aggressive subtype of breast cancer with poor survival outcomes that disproportionately affect African-American women. Minority communities are also disproportionately affected by Obesity. The convergence of these disease states is supported by clinical data that demonstrate obesity promoting TNBC risk and progression. While the molecular relationship between TNBC and Obesity is an active area of research, limited studies investigate how an obesity-associated microenvironment alters TNBC epigenetic states to promote aggressiveness. Here, we model obesity with adipocyte-conditioned media (ACM) which uses adipocyte-secreted factors (ASFs) to initiate the lipogenic state in TNBC cells. This lipogenic state is evidenced by increased lipid droplet formation, attributed to the exosomal vesicle fraction of ACM. This work aimed to determine how adipocyte-signaling impacts the oncogenic capacity of lipogenic TNBC cells. Our data shows that the lipogenic state promotes TNBC colony formation in a way that persists after removal of ASF-signaling. We also observed decreases in reactive oxygen species (ROS), which suggest adaptive mechanisms to adipocyte-induced cellular stress. These phenotypes are supported by ACM-induced increases in genes that support proliferation, migration, and lipid metabolism rewiring. This work also aimed to determine how ASF-induced chromatin remodeling generates a pro-cancer expression profile. We investigated the contributions of adipocyte-induced metabolic rewiring, particularly changes in epigenetic metabolites and enzymes that serve metabolic and epigenetic functions in lipogenic TNBC cells. These data suggest that lipogenic TNBC cells induce Acetyl-CoA Synthetase 2 (ACSS2) activation during stress responses to promote histone acetylation and open chromatin for the activation of stress balance gene programs. We lastly aimed to gain mechanistic insights into ASF-mediated epigenetic remodeling with the design of an epigenetic reporter system that allowed for live-cell tracking of epigenetic states. Our data demonstrated ASF-induced epigenetic repression which may be attributed to adipocyte-mediated transcription factor deregulation. Together, these data demonstrate how ASFs alter epigenetic states that are influenced by metabolic rewiring to support TNBC aggressiveness. Understanding the adaptive mechanisms of obesity-associated TNBC cells reveal cellular vulnerabilities that can be therapeutically targeted among TNBC patients with Obesity.
Table of Contents
Chapter 1: Introduction to Obesity-Associated Epigenetics in Breast Cancer
1.1 Obesity as a risk factor for Breast Cancer
1.2 Impact of Obesity on Triple Negative Breast Cancer Progression
1.3 Epigenetic Contributions to Breast Cancer
1.4 Establishing an In-Vitro Model for Investigating Obesity-associated, Lipogenic TNBC
1.5 Materials and Methods
1.6 Acknowledgements
1.7 References
Chapter 2: Adipocyte-Signaling Promotes the Oncogenic Potential of Lipogenic TNBC Cells
2.1 Introduction
2.2 Experimental Approach and Results: Investigating Lipogenic TNBC Survival and Stress Balance
2.3 Experimental Approach and Results: Investigating Key Adipocyte-Secreted Factors
2.4 Discussion
2.5 Materials and Methods
2.6 Acknowledgments
2.7 References
Chapter 3: Adipocyte-Signaling Remodels Chromatin to Support a Pro-Oncogenic Transcriptional State
3.1 Introduction
3.2 Adipocyte conditioned media stimulates gene expression changes in TNBC BT-549 cells
3.3 Systems Modeling Reveals Adipocyte-Driven Metabolic and Epigenetic Rewiring in Lipogenic TNBC Cells
3.4 Metabolic Rewiring Supports Open Chromatin States To Support Gene Programs Of Stress Balance
3.5 Adaptive Metabolic Responses Reveal Alternative Oxidative Functions in Lipogenic TNBC Cells
3.6 Discussion
3.7 Materials and Methods
3.8 Acknowledgements
3.9 References
Chapter 4: Mechanistic Insights into Adipocyte-Induced Epigenetic Remodeling
4.1 Introduction
4.2 Tet-TA regulated transgene expression is perturbed in lipogenic TNBC cells
4.3 Characterization of other potential repressive sites in polygenic cells
4.4 Activation of pCMV prior to ACM treatment protects the transgene from full repression
4.5 Conclusion
4.6 Materials and Methods
4.7 Data Availability
4.8 Acknowledgements
4.9 References
Chapter 5: Discussions and Future Directions
5.1 Transcription Factor Dysregulation, Not Chromatin Compaction, May Underlie ACM-mediated Gene Repression
5.2 Future Directions for Investigating Transcription Factor Dysregulation
5.3 Future Directions for Use of the pSBtetTA-YP_CFP Transgenic System in Single-Cell Omics’ and Serum Biosensing
5.4 Materials and Methods
5.5 References
Appendix
Supplemental Figures for Chapter 3
Supplemental Materials and Methods for Chapter 3
Supplemental Figures for Chapter 4
Supplemental Materials and Methods for Chapter 4
Supplemental References for Chapter 4
The Epigenetic Landscape of Breast Cancer, Metabolism, and Obesity
A1.1 Introduction: Chromatin Dynamics in Breast Cancer
A1.2 Obesity-Associated Signaling That Influences Metabolism May Also Influence Epigenetic States in Breast Cancer Epithelial Cells
A1.3 Single Cell-Level Obesity-Linked Epigenetic States and Therapeutic Resistance
A1.4 Obesity-Induced Epigenetic States in Immune Cells Are Linked to Drug Resistance
A1.5 Conclusions: Implications for Epigenetic Therapy
A1.6 References
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