Session 4 : Molecular mechanisms of resistance

Defining mechanisms of genomic evolution in cancer

Alterations in chromosomal content and structure including aneuploidy and DNA copy number variations are a defining feature of nearly all cancer types. Despite this, very little is known about the mechanisms that cause these aberrations to accumulate, and what their functional significance is to cancer development and therapy resistance. To tackle these two fundamental challenges, we take several approaches combining cell biology and genomics: First, to define the mechanisms that cause chromosomal instability and aneuploidy in cancer we take the approach of characterising the acute (after one cell cycle) genomic alterations that occur as a result of specific chromosomal instability mechanisms (for example replication stress, or mitotic dysfunction). In this way we aim to ultimately track backwards from cancer chromosomal alterations to decipher their origin. Second, we track the genomic alterations at the single cell level in cancer cells as they grow – giving insights into patterns of ongoing genome evolution over and above what is revealed by traditional static population whole genome sequencing. Lastly, to aid in determining the functional consequences of specific chromosomal alterations we recently developed a new tool to induce specific chromosomes to mis-segregate during mitosis: Nuclease-dead Cas9-based recruitment of kinetochore seeding proteins to a non-centromeric region of chromosomes creates a functionally dicentric chromosome with a high propensity to fail chromosome segregation. Using this tool we and others have been able to begin to study the impact of specific chromosomal alterations on cellular behaviour.