Nowell credits his ultimate discovery of the so-called Philadelphia chromosome to an accident he made while cleaning a research slide. While working in a laboratory at UP studying samples of
chronic myeloid leukemia, he happened to wash his slides with tap water instead of a laboratory solution. When he then studied the slides under his microscope, he saw that the water had caused the cells'
chromosomes to expand. This was unusual, but since at that time chromosomes were not considered part of the cancer-causing puzzle, he could have disregarded the anomaly. Instead, he decided to investigate (he said later, "I didn’t know anything about chromosomes, but it seemed a shame to throw this away.") He partnered with
David Hungerford (1927-1993), a graduate student at the
Fox Chase Cancer Center in Philadelphia. Analyzing the white blood cells of patients with this particular form of leukemia, Hungerford consistently noticed that the
Chromosome 22 was noticeably short. The finding was a turning point. Until then, most scientists believed viruses to be the cause of cancer. This new avenue of research fueled decades of scientific research that produced monumental steps in the treatment of cancer. Gradually, technology improved enough to allow scientists to visualize the genetic material in greater detail.
Janet D. Rowley, a University of Chicago researcher, determined the chromosome to result from a translocation, in which portions of two chromosomes exchange places, causing cells to turn malignant.
Alfred G. Knudson Jr., a geneticist at Fox Chase, made further progress linking genetics and cancer. In 1998, Nowell, Rowley and Knudson received
Lasker Awards for their combined work in this area. At present, drugs have been developed that hold chronic myeloid leukemia in remission for years. ==University of Pennsylvania career==