CBE PhD Thesis Defense: “Comparative analysis of aneuploidy in suspension cancer lines and solid tumors: insights from single cell sequencing approaches”

Aneuploidy, a cancer hallmark, has intrigued researchers due to its near-universal presence in cancer. However, studying its impact is challenging due to the involvement of numerous genes and the difficulty in creating suitable models. Advances in sequencing technology and the vast data available in the Cancer Genome Atlas (TCGA) enabled us to use the p53-null suspension cancer cell line, THP-1, as a model to explore genomic instability in hematopoietic cancer. We aimed to understand why non-adherent cancers typically exhibit lower aneuploidy levels compared to solid tumors. Through an examination of the spindle assembly checkpoint (SAC) and the application of physical and chemical perturbations, we discovered that suspension cancer lines displayed no discernible differences in SAC functionality or sensitivity to external perturbations compared to solid tumors. Notably, chemical perturbations led to the emergence of copy number variations (CNVs) that provided proliferative advantages to daughter cells. Introduction of p53 into THP-1 did not rescue aneuploidy levels, aligning with previous research suggesting its upstream role in suppressing aneuploidy. However, the introduction of p53 did restore downstream p21 pathways, which are known to suppress cancer cell proliferation. Interestingly, the expected growth suppression was found to be independent of p21 levels. Furthermore, the engineered THP-1 exhibited reduced p53 levels after treatment with reversine and etoposide, unlike adherent cancer cells. These findings indicate distinct p53 pathways in liquid cancer lines that ensure genomic integrity. For future CNV analysis, we introduced the live cell ChReporter, enabling non-invasive tracing of CNV status without compromising cell viability.