UC Irvine

The dynamic evolution of tumors starts with the sequential accumulation of DNA mutations that culminate in a cellular transformation event, this marks the beginning of cancer. Dysregulated cell proliferation and faulty DNA repair pathways further hinder normal cellular control mechanisms that maintain healthy tissues, promoting the accumulation of more mutations that eventually escalate into a malignant tumor. Tumor heterogeneity emerges from the acquisition of multiple cancer phenotypes with unique mutational landscapes and by non-genetic transcriptional mechanisms that confer alternate cancer behaviors. This dissertation addresses a longstanding hypothesis that multiple tumor clones co-existing in a single patient can contribute distinct cancer behaviors that shape the tumor microenvironment and collectively promote tumor progression. Using the SW480 patient derived colorectal cancer cell line, we show that this culture is a well-preserved example of a heterogeneous cancer cell line that can be maintained and studied in vitro over long periods of time. We discover two morphologically and transcriptionally disparate SW480 cell subtypes that represent binary cancer stem cell phenotypes found amongst colorectal cancer (CRC) patients. These two subtypes significantly align with multiple classification schemes of human CRC and solid cancers in general. We reveal overarching patterns of inflammation and extracellular matrix deposition in tumors created by the distinct SW480 subtypes and we define their influence on tumor microenvironment cellular compositions at single cell resolution. The datasets generated in this body of work provide the most appropriate and up-to-date transcriptomic data on SW480 cells that correlate with patient-relevant binary signatures of CRC stemness. Additionally, orthotopic xenograft models provided a unique view into the different stages of tumor-induced wounding phenotypes within the intestinal epithelium and identified a highly invasive CRC subtype. As a whole, we show how distinctive behaviors of SW480 subtypes can converge to support metastasis. Finally, we identify different drug inhibitor strategies that can interconvert SW480 subtypes in vitro and we predict how these change the tumor landscape in vivo. This emphasizes the importance of understanding tumor heterogeneity in a patient-by-patient basis as it is a major confounding factor for metastatic disease and chemotherapeutic relapse.