Mechanical Confinement and Heat as Drivers of Aneuploidy in Cancer

Aneuploidy, defined as an abnormal number of chromosomes, is a hallmark of human cancers and contributes to tumor evolution, heterogeneity, and therapeutic resistance. While classically attributed to chromosome mis-segregation during mitosis, emerging evidence indicates that diverse physical and physiological stresses in the tumor microenvironment also shape genomic stability across the cell cycle. In this dissertation, I primarily investigate how mechanical drive heritable chromosome losses. I also extend these findings to other tumor-relevant stressors, particularly heat shock and lipid accumulation. In Chapter 1, I provide a brief overview of aneuploidy, outlining the role of the cell cycle, its role in cancer progression, and its clinical implications. In Chapter 2, I examine how mechanical confinement, a physiologically relevant feature of solid tumors, perturbs mitotic cells. Using a chromosome reporter system, I show that confinement disrupts prometaphase progression, generates delayed micronuclei, and leads to heritable chromosome losses These effects phenocopy nocodazole, a microtubule inhibitor, and transcriptional analysis identifies confinement-induced dysregulation of mitotic programs. These results introduce the concept of a mitotic memory, in which transient mechanical stress on mitotic cells leaves lasting genetic changes. In Chapter 3, I extend my studies on chromosomal instability to other stressors. Hyperthermia destabilizes the mitotic spindle, induces abnormal spindle morphologies, and produces a linear increase in heritable chromosome losses and micronuclei across multiple cancer cell lines. In contrast, lipid droplet accumulation delays the cell cycle and reduces chromosome losses, yet still perturbs spindle integrity. Both stresses generate co-localized colonies of chromosome losses and gains, with gains consistently lagging behind losses, supporting a model in which micronuclei harbor nascent gains. Overall, by showing how confinement, heat, and fat act through overlapping and distinct mechanisms to affect genome stability, this work expands our understanding of the mechanisms of chromosomal instability.

Author dc:creator

• Phan, Steven

Advisor dc:contributor.advisor

• Discher, Dennis, E

• Biology
• Biochemistry, Biophysics, and Structural Biology
• Medical Sciences

Language dc:language.iso

en

Repository record dc:identifier.uri

https://repository.upenn.edu/handle/20.500.14332/62295

OAI identifier oai:identifier

oai:repository.upenn.edu:20.500.14332/62295