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.
plate 2
plate 3
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.
2
_______
THREE HUNDRED WORDS
At the time of their discovery, David Hungerford was spending about ten hours a day looking at fly chromosomes, and Peter Nowell had just returned to the University of Pennsylvania. Nowell had originally started working in the pathology lab there as a summer job in 1950. A cocky and charismatic med student, Nowell had felt certain that, given the chance, he could “solve this cancer problem” in a matter of months. But that summer he got married, and the Phillies were on their way to winning the pennant, distractions that, he says, delayed his plans to cure cancer.
But those few summer months were enough for Nowell to understand just how vast a territory he’d entered into as a cancer researcher. “I really knew very little about the specifics of things,” he would say later. “In those days, it was true of pretty much everybody.” He decided to take an internship for a year with a hematologist at a nearby hospital. It was there that he had his first serious education about cancers of the blood—how devastating and how complicated these diseases really were.
plate 6
There were the leukemias that took over the white blood cells, with chronic versions that progressed slowly and acute versions that led to rapid destruction of the immune system. White blood cells, which fight infections, normally numbered 4,000 to 10,000 per microliter of blood. Leukemia patients typically had counts in the hundreds of thousands per microliter. The lymphomas, Nowell learned, poisoned the lymph, another infection-fighting part of the immune system concentrated primarily in bean-shaped nodes throughout the body. Lymphoma could pass from one node to another, like a fungus spreading through a forest. Multiple myeloma targeted the plasma—the yellow-colored liquid that holds red blood cells, white blood cells, and platelets in suspension as they course throughout the body—hardening the fluid into tumors inside the marrow and softening bones.
These were the so-called liquid cancers, or hematologic malignancies. For cancer researchers, they were often easier to study because of their accessibility. It was much simpler to draw fluid out from a vein than to cut a patient open to excavate a solid tumor buried deep inside the body. But being able to get at the cancer hadn’t led to more significant advances in treatment. When Nowell was in medical school, most types of liquid cancers were still incurable.
On rounds, he saw the victims of these harsh diseases. They brought to life the horrors of cancer more than any squashed cell ever had. A young person getting his first palpable glimpse at death, Nowell saw how shallow he’d been when he first arrived at Penn. Humbled, he realized that cancer was a beast the world had been wrestling for centuries, and against which few meaningful strides had been made.
Then, just when he was feeling a surge of dedication to the long haul of cancer research rise up in him, Nowell was drafted into the military. He was sent to San Francisco to work at the US Radiology Defense Laboratory, where he was assigned to a team studying the potential effects of radiation. The government wanted to know the possible dangers associated with the fallout from nuclear testing in the Pacific. The risks to people included diminished numbers of red and white blood cells circulating in the body in the short term and, in the long term, leukemia and other malignancies. Again, the horrors of cancer were made ever more apparent to him—this time, even more so as he witnessed the man-made devastation.
In 1956, Nowell returned to Penn, as determined as ever to solve this cancer problem.
Hungerford, on the other hand, had no desire to cure cancer. It just wasn’t his way as a scientist. He had taken the more scholarly PhD route, and the driving force behind all of his work was a love of observation—to look, to record what he saw, and to share those findings with anyone else who might be interested. Compared with Nowell’s passion, Hungerford’s approach could seem cold and distant to their colleagues. But Hungerford was happy to record their observations for the simple reason that observations should be recorded. “He just liked to look through the microscope and see the thing,” said Alice. He felt no ownership of his ideas, and he had no need for recognition. He just wanted to do the work of science; that was his role in the world. It was what made him feel alive.
Nowell and Hungerford’s discovery of “the minute chromosome” was published in 1960. The report consists of three brief paragraphs in a scientific journal, without even the typical list of references that scientific papers have, set indiscriminately among a few other reports of the month. “It’s three hundred words,” said Emil Freireich, a leukemia doctor responsible for many major therapeutic advances, and a towering figure in the world of cancer medicine. “And it revolutionized everything.”
WHEN NOWELL AND Hungerford published their third scientific paper documenting the truncated chromosome in a large number of patients, with reports from groups at universities around the world confirming the phenomenon, the minute chromosome was renamed the “Philadelphia chromosome” in recognition of the city where it had been discovered.
After scientists across the world found the abnormal chromosome in their own CML cell samples, many set to work on finding other such mutants. At first, researchers thought that this chromosome was the first drop in what would soon become a waterfall of genetic mutations linked to cancer, and, they hoped, some meaningful advancement for cancer treatment. In scientific journals, the chromosome was referred to as Ph1, an abbreviation that left space for other mutation discoveries to come—Ph2, Ph3, and so on—with researchers in other cities then following suit. But further cancer-linked mutations proved elusive. No others were found, in Philadelphia or anywhere else. Ph1, as it is still often called, was found in a small percentage of samples from patients with other types of leukemia, acute lymphoblastic leukemia and acute myeloid leukemia (AML), but the link was not nearly as strong as that seen in CML. There w
as a brief stir over an abnormality spotted by some New Zealand researchers—the “Christchurch chromosome,” people called it—but that soon turned out to be a false alarm. Whatever mutations were found appeared much more rarely than the Philadelphia chromosome did in CML. Those tenuous links hardly seemed the stuff of cancer cures.
And so enthusiasm over the Philadelphia chromosome waned, mainly because no one knew what to do with the information. “In the early years, the medical community did not care about human chromosomes,” recalled Alice Hungerford, who met David when she took a job in his lab. It was like seeing a bright spot in the night sky with no knowledge of planets and solar systems. Despite the obvious connection between CML and the Philadelphia chromosome, there was very little suspicion of a causative link between genetic abnormalities and cancer. There was no technology to look any further into the mutation. In fact, it wasn’t even called a mutation; it was considered a deletion. Nowell and Hungerford resisted the notion that the piece of chromosome was completely gone from the cell. They knew that such a deletion would likely be lethal. But they had no explanation for what else could have happened. A piece of genetic material had vanished. Why had it disappeared? Did the change somehow cause leukemia, or did leukemia somehow cause the change?
These were questions for another decade. Knowing the standard number of chromosomes had enabled geneticists to create a universal number language. But the view afforded by the technology at the time was so coarse that at first Nowell and Hungerford couldn’t even tell which chromosome the abnormality was located on. Eventually it became clear that the deletion was from one of the two copies of chromosome 22, but that was still an incomplete description. Chromosome 22 looked an awful lot like chromosome 21 and sometimes even the Y chromosome present in males. Later, methods for staining specific chromosomes would allow for a much more discriminating study. But in 1960, these techniques were unknown. Whatever questions scientists had about the Philadelphia chromosome, there weren’t any that could be answered.
NOWELL AND HUNGERFORD’S collaboration also reached a standstill. It was as if they had come together just to find the Philadelphia chromosome, and now, having done so, needed to move on. Nowell continued to pursue cancer research, and would ultimately spend his entire career in the same laboratory. His early success garnered him a rare lifetime government research grant. The money enabled him to pursue cancer research without the pressure to churn out publications or complete grant applications every few years, a highly limiting factor on lab research today. “I had it easy,” Nowell recalled toward the end of his years at Penn, his hair as white as his lab coat. “As my wife used to say, I just assumed there was a closet with green pieces of paper in it.” Nowell’s grant left him free to continue research without worry about making discoveries.
Although he never again struck gold with a serendipitous discovery, Nowell contributed to important theories about how tumors evolve. He was an early adopter of the notion that tumors accrue mutations over time, a key component of modern anticancer drug development. As he put it, cancer works like a tree. A branch off the trunk is the first mutation, and every subsequent twig represents further changes to the DNA. In the end, a cell that started off just a bit different from normal accrues multiple oddities, each one enabling it to better survive in the body, and each one a potential target for a new drug. This phenomenon is at the heart of current cancer research, as scientists sift through the dozens, sometimes hundreds, of genetic abnormalities for the ones that are advancing the deadly cells.
Hungerford’s life took quite a different turn. In 1971, he was diagnosed with multiple sclerosis. Not wanting to suffer the pity of his peers, Hungerford kept his disease a secret, telling only Nowell, who had become his friend and now confidant. When Hungerford’s treatments and condition diminished his productivity, colleagues and grant reviewers assumed he was either lazy or untalented. His funding gradually decreased, and eventually his lab at Fox Chase Cancer Center, where he’d worked since before meeting Nowell, was shut down. Devastated, Hungerford never stepped behind the microscope again. “He did not pick up a scientific journal after that,” says Alice. “It broke his heart.” A longtime smoker, Hungerford died of lung cancer in 1993 at the age of 66.
3
_______
INVESTIGATING A CHICKEN VIRUS
Like the seed that withstands a drought only to bud with the first touch of rain, further investigation of the Philadelphia chromosome would lay dormant until the early 1970s. The blossoming of the research was largely driven by technology, and in the early 1960s, the tools needed to parse the meaning of this chromosome were nonexistent. They were still more than a decade away.
In the meantime, a second thread of research was ongoing, one that would eventually connect to the Philadelphia chromosome, but in a wholly unexpected way. This was a story not of genes but of viruses.
Almost hidden away on New York’s Upper East Side, Rockefeller University, founded in 1901, thrums with a quiet, brainy intensity that has led to countless scientific discoveries. Twenty-four Nobel Prize winners have graduated or conducted research there. Lab work at Rockefeller has led to breakthroughs in understanding hepatitis B, obesity, diabetes, cancer, skin diseases, infectious diseases, and other ailments and puzzles. In its first decade, when it was still called the Rockefeller Institute for Medical Research, a man named Peyton Rous studied lymphocytes, white blood cells that flow throughout the body and gather in small clusters, known as lymph nodes, in the underarms and other regions of the body.
Rous, born in 1879, and his two siblings were raised by his single mother in Baltimore, Maryland. After her husband died, she’d resisted the temptation to return to her home state of Texas, where family could help raise the children. Instead, she stayed in Baltimore, believing that the city would afford her children the best possible education. It was not school but the wildflowers he encountered on his frequent walks through the woods near his home that first bent Rous toward science. A month-by-month chronicle of the flowers he observed on those walks, printed in the Baltimore Sun, was his first published paper.
After earning his medical degree at Johns Hopkins, Rous decided to focus on medical research instead of a medical practice. He’d worked as a pathologist at the University of Michigan from 1906 to 1908, work that included a 1907 stint in Dresden, Germany, where, he would later write, there was “no hint of war in the air.” He joined Rockefeller as a laboratory researcher in 1909. In September of that year, after a few scant weeks on the job, Rous received a visit from a Long Island farmer, her arthritic hands carrying a Barred Plymouth Rock hen, a common domesticated chicken. A large tumor was sticking out of its breast, poking through its striped feathers. The chicken, “a strong, young hen,” Rous would say in the 1910 paper he published about this work, was about fifteen months old, the tumor about two months. Its owner wanted Rous to remove the hardened malignancy.
Rous agreed, and a few days later Rockefeller Institute had its first- ever chicken surgery. On the first day of October, Rous numbed the hen with ether and sliced into its belly. He removed most of the irregular, globular mass, its yellowish-pink tissue crumbling under Rous’s knife. The operation was not successful: The hen died a month later from remnants of the tumor spreading in the tissues around its abdomen. But the excised tumor created a lasting legacy.
plate 5
Not wanting to waste the opportunity, Rous decided to take a closer look at the excised tumor. He removed a portion and ground it up finely, then forced the crushed mass through an extremely fine filter, one that would prevent the passage of chicken matter or bacteria to the other side. The theory was that the resulting filtrate would contain only the elements that were directly relevant to the growth of cancer. When the extract was injected into other fowl, the animals developed the same knobby tumor within weeks of inoculation. The cancer was transmissible. There was only one explanation for this transmissible chicken cancer: the underlying cause had to be a virus.
Rous was not the first to show a connection between viruses and cancer. An Italian scientist in the 1840s had observed that nuns in Verona got cervical cancer only rarely, whereas married women experienced it more frequently. The culprit—human papilloma virus—would not be identified until 1983, but it was clear then that some contagious element had to be at play. Just a year before Rous was presented with his famous chicken, two Danish scientists had shown that a certain type of bird leukemia had the same infectious quality, but the discovery was largely ignored because that leukemia was not recognized as a malignancy at the time. A type of lung cancer seen in sheep was known to be transmissible in the 1800s, and an infectious anemia virus had been found in horses in the early 1900s. But none of these had the impact of what would come to be called the Rous sarcoma virus, or RSV. His was the first concrete demonstration that cancer could be triggered by an infection.
Yet it wasn’t until the 1960s that RSV would really enter the cancer research limelight. At the time, interest in viruses as vectors for passing cancer was on the rise for two reasons. First, there was mounting suspicion—based on the sarcomas like the one Rous had seen and other animal cancers—that viruses cause human cancer. If animals got cancer this way, why not people? Medical research was desperate for any glimmer of understanding about the genesis of cancer, and what with their invisibility and skills of invasion, viruses seemed like a feasible answer.
The Philadelphia Chromosome Page 3
