One day Nowell took a shortcut around the usual scientific procedure. “Pete was in a hurry, as young men tend to be,” Alice Hungerford, David’s wife, would recount years later. Instead of following a more rigorous cleaning method, Nowell washed a sample of white blood cells under some tap water. He dropped the rinsed cells onto the slide and was amazed by what he saw through the microscope. The tap water, it turned out, was hypotonic—a low-pressure solution that caused the cells to swell, like a deflated raft being blown up with too much air.
With the cells ballooned like that, Nowell could see something else equally surprising. It turned out that a bean extract he’d applied to help clot the red blood cells (making them easier to remove from a sample) had also stimulated division in the white cells. Captured in the midst of dividing, the cells were at their most expanded. Because the tap water had further expanded the size of the cell, the chromosomes had more room to spread out and were suddenly easier to see and count. No one was looking at chromosomes this way. Nowell hadn’t known it was possible. Then again, he knew nothing about genes and had little interest in genetics. But he kept the slide, figuring someone out there might be interested in taking a look.
The genetics community was small then, and the number of people in the Philadelphia area interested in genetic research could be counted on one hand. Hungerford heard about Nowell’s slide. The two began working together. For years, Nowell prepared slides that Hungerford would study under the scope. They perfected the hypotonic solution, still used in molecular genetics today, and figured out how to air-dry slides to help the cells spread out even more. But they saw nothing noteworthy.
Then, in 1959, three years after they’d met, there it was: an abnormally small arm of a worm-shaped chromosome inside a cell of a person with CML. With the chromosomes splayed in the squashed cell, Hungerford could clearly see that one was too small. A piece of it was missing. They looked at blood samples from six other CML patients and found the same abnormality.
Stunned, Hungerford snapped the camera shutter. He would not live to see the significance of the picture he’d just taken. In 1959, the effect that a single photograph showing a single mutant chromosome would have on the lives of countless patients and on the future of cancer treatment was entirely unsuspected.
“Until we stumbled over this Philadelphia chromosome, there was really no evidence that cancer might be due to genetic change,” Nowell, now 79, said decades later. This photograph would become the lasting portrayal of a moment when everything changed for cancer and medicine as a whole. It was the as-yet unrecognized starting point for the modern era of targeting cancer at its root cause.