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A long voyage: Juanita Merchant’s trip to the top of her field

Yale Medicine Magazine, 2018 - Spring


Juanita L. Merchant, MD ’81, PHD ’84, has spent decades exploring how chronic inflammation and regulatory pathways can lead to cancer in the gastrointestinal tract. In 2017, in recognition of her groundbreaking contributions to her field, she was asked to join the American Academy of Arts and Sciences.

Merchant is the H. Marvin Pollard Professor of Gastrointestinal Sciences, professor of internal medicine, and professor of molecular and integrative physiology at the University of Michigan Medical School.

Last year, she was one of just 223 African-American women to hold the rank of full professor at a United States medical school out of 182,786 faculty, according to the Association of American Medical Colleges. She has earned many other honors, including her election to the Institute of Medicine of the National Academies in 2008.

“It’s been a great ride, and I’ve really enjoyed academics,” said Merchant, who also makes time to mentor underrepresented minority students hoping to blaze their own trails as physician-scholars.

A Los Angeles native and the daughter of an elementary school teacher, Merchant attended public schools and considered becoming a math teacher. But she enjoyed her organic chemistry class at Stanford University so much that she changed her mind in favor of medical school. It was the mid-1970s, and Merchant recalls a mentor who was a woman of color suggesting she pursue both an MD and a PhD.

“You are a minority. You are a woman. If you really want to do academics, you need to do an MD/PhD, so that people will respect you,” Merchant recalled the researcher telling her. “There were no women on faculty, at least in the STEM sciences, then.”

In 1977, Merchant arrived at Yale School of Medicine, where she was the first African-American to earn a dual degree in medicine and cell biology. She worked with Fred Gorelick, MD, the Henry J. and Joan W. Binder Professor of Medicine (digestive diseases) and of Cell Biology, and the two remain close. In 1984 she went on to an internal medicine residency at Massachusetts General Hospital. Three years’ post-residency lab work followed. After a year at UCLA, Merchant accepted a job offer at Michigan, where she has taught, cared for patients, and conducted research since 1991.

Merchant recently demonstrated how Helicobacter pylori infection can contribute to development of gastrointestinal cancer. Her research demonstrates how over time the bacterium destroys the acid-secreting cells of the stomach. This destruction, in turn sends a message to immune cells to turn into a new kind of cell that fosters a permissive environment for cancer.

She also studies the origins of gastrinoma, a type of cancer found in the duodenum or pancreas. These tumors have long been thought to arise from the epithelial cells lining the gut. But Merchant’s group found evidence that they may actually arise from the enteric nervous system—specifically, from the nurse cells that surround gut neurons. If verified, the discovery could lead to totally different therapeutic options.

“Basically, there’s the possibility that we’ve been barking up the wrong tree,” Merchant said. “That really could change the way we approach these tumors.” She is working on a paper describing molecules that could attack the mutations leading to these cancers.

Merchant also discovered a protein that acts to promote colon cancer, as well as to prevent cells from undergoing a normal shutdown process called senescence. Interestingly, this protein is regulated by a butyrate, a substance made by the gut’s natural bacteria from dietary fiber and known to be crucial for the health of colon cells. “That’s why we always encourage patients to eat a healthy diet high in fiber,” she said.

Merchant credits her Yale training with making her “bilingual.”

“The clinician isn’t going to know or necessarily care—because they are so busy—about how a small molecule docks onto some protein,” she said. “I may not understand all the details about the biophysics, but I understand this protein is important in this disease state. ... We, the physician-scientists, being trained in both basic science and clinical medicine—we are the people that really bridge that gap the best.”

Today, Merchant runs a summer program that encourages underrepresented students to consider seeking an MD/PhD. The dual-degree path is tough, and the career seems daunting, she says. But, she added, “I would say on the other side of it, having done my career this way, it’s been worth it.”

Another gap she works to bridge: impostor syndrome, a type of self-doubt that she used to feel herself and that she says she has seen over and over in high-achieving students of color. It can lead them to leave the academic ranks when they might have stayed and thrived had they had some mentorship.

“The system needs to be more sensitized to supporting these students,” she said.

Most of Merchant’s mentors have been white men—of Gorelick, for instance, she recalled, “If he saw I was struggling with this particular assay, he reached out and helped.” She tells students of color that their mentors, too, may not look like them. But as more of them enter academics, she notes, this dynamic should change.