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School of Medicine
On the Shoulders of Giants
Meet four Johns Hopkins “greats” who made seminal contributions in the early years of the school of medicine—and their contemporary counterparts who have grabbed the baton to move their fields forward farther still. Our final installment in a yearlong series.
Illustrations by Peter Strain
Heroes of Hypertension
Caroline Thomas and Erin Michos
The name Caroline Bedell Thomas, M.D. ’30 (1904–97), is practically synonymous with the Johns Hopkins Precursors Study she designed in 1946, which is still following a cohort of former Johns Hopkins medical students to elucidate risk factors for hypertension and heart disease.
While prospective studies are widely used today, the utility of this approach was questioned by many in Thomas’ day, but she correctly believed it could reveal risk factors for life-threatening disorders decades before symptoms surfaced. With almost half of the study’s subjects still participating, the Precursors Study is the longest-running project of its kind in the nation. Even more important, Thomas’ vision became a model for many impactful studies to come.
From 1948 through 1964, Thomas enrolled 1,337 students, mostly young, white males. Such a homogenous group wouldn’t be acceptable today, but it fortuitously limited confounding factors, enhancing the accuracy of her correlations. Each participant was subjected to a series of physical exams, including electrocardiograms, stress tests and assessment of serum cholesterol levels, plus an 11-page questionnaire about eating and lifestyle habits, family history, and psychosocial characteristics, such as stress, anger and depression.
“It’s hard [today] to appreciate how forward-thinking Thomas was. She asked about every factor we’re still studying: alcohol, smoking, coffee, blood pressure,” says Erin Michos, associate director of preventive cardiology for Johns Hopkins’ Ciccarone Center for the Prevention of Heart Disease.
Thomas and her small staff mailed annual follow-up questionnaires for 40 years as the young doctors aged. Over time, risk factors emerged. Many are common knowledge today, like her 1956 paper that identified high cholesterol as a predictor of heart disease. Ultimately, she published dozens of papers from the study, many outside her field of cardiology, due to her insightful questions. In 1986, at the age of 82, she finally passed the baton to colleagues; today, Joseph Gallo, professor of mental health at the Johns Hopkins Bloomberg School of Public Health, directs the study.
“I would have liked to have met Dr. Thomas,” says Michos. “Beyond her impact on medicine, she was a pioneer for women, being only the third woman to reach full professorship at the Johns Hopkins University School of Medicine, in 1970.”
Michos follows closely in Thomas’ footsteps by using data from two large cohort studies to search for novel risk factors for cardiovascular disease. “Cardiovascular disease is the No. 1 cause of death in developed countries,” she says, “but 80 percent of cases are thought to be preventable with lifestyle changes and early intervention.”
The data Michos studies come from men and women of Caucasian, African, Hispanic and Chinese descent, and is made possible by the latest technology: CT scans to assess coronary artery calcium, skin patches that monitor arrhythmias and, of course, genomics.
One novel biomarker for inflammation, GlycA, which is measured by nuclear magnetic resonance (NMR), has recently captured her attention. (Inflammation fuels the growth of plaques in artery walls and makes them more likely to rupture and cause a heart attack.) During the NMR process, GlycA breaks off of a sugar decorating several proteins involved in systemic inflammation.
“GlycA levels are actually a composite of multiple components of the inflammatory process,” says Michos. And since GlycA’s levels show less day-to-day variation than other inflammatory markers, she and others in the field believe they could better predict which individuals need preventive measures.
Michos knows, as Thomas did, that the best intervention is prevention.
Battlers of Blindness
Arnall Patz and Akrit Sodhi
When doctors Arnall Patz and Leroy Hoeck applied for funding around 1949 from the National Institutes of Health (NIH) to study blindness in premature babies, they were soundly rejected. The duo’s idea was that too much of a good thing—pure oxygen—was causing retinopathy and subsequent blindness in many premature babies.
“These guys are going to kill a lot of babies … to test a wild idea,” complained the grant reviewers. It may have been wild, but they had seen shrunken blood vessels in postmortem evaluations of premature babies, and they knew that retinal arteries narrow in adults breathing pure oxygen.
Patz (1920–2010), still in training at Washington, D.C.’s Gallinger Municipal Hospital, was undeterred by the rejection and instead got his brother to fund the project. With that loan, Patz and Hoeck embarked on what was likely the first randomized controlled trial in ophthalmology. The result: The eyesight of thousands of babies was saved with safe-but-lower doses of oxygen, and a Lasker Award was bestowed on Patz in 1956 by Helen Keller.
When his training was finished, Patz began his career at Johns Hopkins as a part-time faculty member in 1955, joining full time in 1970. Around then, he initiated a project with engineers at the Johns Hopkins Applied Physics Laboratory. Using materials on hand, including a pingpong ball, they built the world’s second argon laser photocoagulator. Patz hoped it would prevent the growth of leaky, abnormal blood vessels causing blindness in people with diabetes—a condition known as proliferative diabetic retinopathy, the most common cause of blindness in working-age Americans.
The instrument delivered blue light through an articulated arm and modified ophthalmoscope to the retina, coagulating the oxygen-starved tissue and causing the adjacent leaky blood vessels to recede. Though lasering the retina usually caused some loss of peripheral and nighttime vision, the procedure became the standard for many disorders of the eye’s vasculature, like age-related macular degeneration, saving the sight of countless patients.
Now researchers at the Wilmer Eye Institute are trying to treat retinopathy with more precision and fewer side effects using molecules. Akrit Sodhi is at the forefront of work to reverse the body’s sight-stealing reactions to retinal suffocation. He is building on the work of Johns Hopkins’ Gregg Semenza, who discovered the protein hypoxia-inducible factor (HIF) in 1992.
Semenza’s subsequent research showed that HIF responds to low oxygen levels by ramping up genes such as vascular endothelial growth factor (VEGF) that promote blood vessel growth.
Unfortunately, the new vessels are too abundant and permeable; they flood the retina with fluid, not oxygen, causing blindness. Sodhi says eye injections of an anti-VEGF drug halt symptoms and preserve sight in many, so they’re now more common than laser treatments for retinopathies. But the shots are uncomfortable, inconvenient and don’t work adequately for most patients.
So he is seeking a better solution, in part by trying to get HIF and VEGF down to physiologic levels without shutting them off completely, since they do some good things along with the bad.
His lab is also looking for new molecular targets. Recently, they demonstrated that the signaling molecule angiopoietin-like 4 (ANGPL4) promotes vascular permeability and pathologic blood vessel growth in the eyes of people with diabetes. Sodhi hopes that inhibiting ANGPL4 or its receptor could become the next standard treatment—carrying on Patz’s honored tradition.
Trailblazers in Scleroderma
William Osler and Ami Shah
"In its more aggravated forms, diffuse scleroderma is one of the most terrible of all human ills,” wrote the first physician-in-chief of The Johns Hopkins Hospital, William Osler (1849–1919). He likened scleroderma to the fate of Tithonus, prince of Troy, whom Zeus granted immortality but without the accompaniment of eternal youth: “Like Tithonus, to ‘wither slowly,’ and like him to be ‘beaten down and marred and wasted’ until one is literally a mummy, encased in an ever-shrinking, slowly contracting skin of steel, is a fate not pictured in any tragedy, ancient or modern.”
When Osler wrote those words in a journal article in 1898, he had already seen eight patients with the disease, whose name means “hard skin.” But he described the malady in his classic textbook, written in 1892, before the opening of the Johns Hopkins University School of Medicine. Though he had only seen one patient at that point, he was familiar with the medical literature and recognized scleroderma as a chronic, progressive disease that could be limited or diffuse in nature. He classified it, as others did, as a disease of the nervous system, “probably dependent upon changes in the arteries of the skin leading to connective tissue overgrowth.”
It took decades for clinicians to recognize the hardening of the internal organs as part of the disease. And scleroderma’s true nature as an autoimmune disease remained hidden until the 1960s.
When Fredrick Wigley joined the Johns Hopkins faculty in 1979, he started a program for scleroderma patients. Like Osler, he carefully recorded the symptoms of the patients he saw. Unlike Osler, he had the ability to store patient samples long term, so he collected blood and DNA from patients, even though he didn’t know what to do with them yet.
In the early 1990s, Antony Rosen, now vice dean for research, joined the rheumatology faculty. With a proclivity for basic science research, he and Wigley made a good team. Rosen believed that autoimmune diseases occur when an underlying susceptibility is triggered by an immunological reaction to an aggressor, like a new tumor. And then Wigley started noticing just that: patients who came down with scleroderma symptoms just before or after a cancer diagnosis.
Ami Shah ’03, who was doing her fellowship then, picked up the challenge and started studying scleroderma patients with and without cancer. She found that a subset of patients with aggressive scleroderma had an increased risk of cancer around the time of scleroderma onset. And in the blood samples Wigley had been collecting all those years, she and her colleague Livia Casciola-Rosen found a clue: elevated levels of antibodies against RNA polymerase III, or RNAP3, a ubiquitous nuclear protein that transcribes “housekeeping genes.” Antony Rosen and colleagues then analyzed the tumors from these patients and discovered mutations in the RNAP3 gene.
These data suggest that scleroderma begins in these patients when the immune system sees mutated RNAP3 in tumor cells and appropriately attacks it—but then starts attacking normal RNAP3 in healthy cells, triggering autoimmunity.
Shah, now the director of clinical and translational research at the Johns Hopkins Scleroderma Center, says new scleroderma patients are now screened for cancer and RNAP3 antibodies. She is eager to see whether treating underlying cancers improves patients’ scleroderma. “There’s a lot to learn here about the interface between cancer and the immune system,” she says. “We could even discover something that helps everyone with cancer, not just those with scleroderma.” That’s a discovery that would make Osler proud.
Hamilton Smith and Ken Kinzler
In 1982, the food and drug administration approved the use of insulin made by genetically engineered bacteria. In 1986, DNA fingerprinting was first used to exonerate an innocent man. And in 2000, the first draft of the Human Genome Project was completed. The connection? Restriction enzymes—specifically, the type II restriction enzymes that Hamilton Smith ’56, and his graduate student Kent Wilcox, Ph.D. ’74, discovered 50 years ago, in 1968.
The discovery happened by mistake. To get Wilcox started, Smith had devised a simple experiment involving Haemophilus bacteria and DNA from the P22 virus. But when Wilcox tried to collect the P22 DNA, it was gone.
Just the previous week, Smith had presented a paper in a journal club reporting the discovery of bacterial enzymes that “restricted” viruses to flourishing within only certain strains of bacteria. These (type I) “restriction enzymes” recognized viral DNA and cut it into random pieces. So Wilcox surmised that perhaps restriction enzymes had “chewed up” the P22 DNA.
Smith thought Wilcox had botched the experiment, but he did ponder the restriction enzyme idea and came up with a test. The simple experiment they did the next day showed that something in the bacteria could cut P22 DNA. Further experiments showed that “their enzyme” wasn’t cutting randomly but at a very specific sequence.
Enter Smith’s colleague and friend, Daniel Nathans, who saw how the restriction enzyme could be used as a genetic tool. He was the first to use it to cut DNA into fragments and run them through a polyacrylamide gel for analysis. He also used it to map genes in viruses. Today, more than 3,000 type II restriction enzymes are known. Each cuts at a specific sequence, allowing DNA to be cut, copied and pasted like a word processing document. Ultimately, Nathans and Smith shared the 1978 Nobel Prize in Physiology or Medicine, along with Werner Arber, who first posited the enzymes’ existence.
Restriction enzymes quickly became a fixture in biomedical research. “All of the early work we did relied almost exclusively on our ability to use restriction enzymes,” says Kenneth Kinzler, Ph.D. ’88, professor of oncology at the Johns Hopkins Kimmel Cancer Center. He’s referring to the characterization of cancer-causing mutations in the genes APC and TP53 and their networks, which he helped work out with Bert Vogelstein ’74, also of the Kimmel Cancer Center.
In their decades of work together, Kinzler and Vogelstein’s drive to understand the genetics of cancer has led them to develop several technologies that no longer rely on restriction enzymes. Perhaps the most revolutionary is digital PCR (polymerase chain reaction), published in 1999. It was born of their desire to detect and count individual mutations in bits of tumor DNA floating in the bloodstream. With heavy dilution, they could separate each bit of DNA into its own tiny well, where it is replicated until there’s enough to sequence and count.
The same concept, with more sophisticated techniques, is at work in liquid biopsies, which can be used to detect early cancers, direct therapies and monitor for recurrence. Recently, the team devised a liquid biopsy that can simultaneously screen for eight prevalent cancers.
Truly, the possibilities seem endless. And it all started with a stroke of luck and the perceptive mind of Hamilton Smith.
In their decades of work together, Kinzler and Vogelstein’s drive to understand the genetics of cancer has led them to develop several technologies that no longer rely on restriction enzymes.