Catherine J. Wu, MD (Damon Runyon Clinical Investigator ‘07-‘12), Matthew L. Meyerson, MD, PhD (Damon Runyon Fellow ‘95-‘98), and colleagues at Dana-Farber Cancer Institute, Boston, and the Broad Institute, Cambridge, demonstrated how genetic mutations evolve over time in chronic lymphocytic leukemia (CLL) cells. The researchers used next-generation gene-sequencing technology to monitor genetic changes in tissue samples from cancer patients, demonstrating that subsets of cells in each tumor contain different genetic makeup. These genetic mutations can predict how patients respond to different therapies and whether CLL will recur after treatment. The studies, published in the journal Cell, are likely to be important for development of improved therapies.