How Rowley Revolutionized Cancer Research

The University of Chicago’s Janet Rowley, MD, laid the groundwork for cancer genetics by showing that certain forms of leukemia occur because end-pieces of chromosomes break off and switch places.

Before her 1972 discovery, scientists knew that genes in cancer cells had numerous mutations. But it was not yet clear that those mutations caused malignancy, and that specific mutations led to particular types of cancer.

Those insights, which flowed from Rowley’s work, are among the pillars of modern cancer research.

Rowley credits a then-new technique of staining chromosomes to reveal patterns of “bands” with enabling her to see something no one else had seen.

“Whereas previous to that time, chromosomes would stain uniformly and you could distinguish them by their size and shape but not much else,” Rowley recalled in a 2009 interview given prior to her receiving the Presidential Medal of Freedom, the United States’ highest civilian award.

Armed with this new technology, Rowley scrutinized thousands of chromosomes from Medical Center patients with chronic myelogenous leukemia (CML).

Not long before, scientists in Philadelphia discovered that one of the chromosomes in CML cells was shorter than normal, and scientists assumed that it had lost part of its DNA. This chromosome was dubbed the “Philadelphia” chromosome.

The new banding enabled Rowley to see that the part missing from the Philadelphia chromosome was actually attached to another chromosome, and that a bit of that chromosome was attached to the Philadelphia chromosome. In other words, chromosome pieces were breaking off and switching places, “translocating.”

When Rowley and her colleagues found other translocations, and succeeded in identifying each with a specific kind of cancer, researchers around the world joined in the chase. For the first time, types of cancer could be distinguished by specific genetic mutations. The view of cancer, how to study it, and how to treat it had been revolutionized.