Copy-number alterations and chromosomal translocations are widespread in cancer and frequently causing oncogenic mutations that drive tumorigenesis and therapy resistance. Despite their prevalence, how these alterations arise during tumor development remains a mystery. We have gained significant insight into this question by analyzing alterations in unstable genomes at the single-cell level over one and multiple generations. Our results indicate that even a single broken chromosome in an ancestor cell can cause highly dynamic evolution and generate extensive genetic diversity in the progeny population, giving rise to all forms of alterations in cancer genomes, including focal amplification and deletion, arm-level copy-number changes, and complex rearrangements. We hypothesize that such genetic diversity may fuel the transition from pre-malignancy to cancer and present preliminary evidence from the analyses of Barrett’s Esophagus as a precursor to esophageal adenocarcinoma. Together, our results suggest that a few simple mechanisms of chromosomal evolution may be sufficient to create the enormous complexity of cancer genomes and the evolution of unstable genomes may be not totally random after all.

Learning objectives:

1. What makes an unstable chromosome and how does it trigger genome evolution?
2. How does genome instability and genetic diversity promote tumor development?