Researchers look at melanoma-Parkinson's link
Bethany Barnes Wick
Researchers at the University of Arizona are trying to solve a big mystery: Why are Parkinson’s patients more likely to get melanoma — and melanoma patients more likely to get Parkinson’s?
Unraveling the link between diseases “that you think would have nothing to do with each other” could help researchers learn more about Parkinson’s, said Scott Sherman, an associate professor of neurology at the UA.
On the case are scientists from a variety of disciplines who study Parkinson’s and melanoma. Tim Bowden, for example, is a UA professor emeritus of molecular and cellular medicine and a member of the Arizona Cancer Center. He has a long-standing research interest in skin cancer. He’s also a Parkinson’s patient.
Bowden started talking to Sherman, who happens to be his neurologist, and to dermatologist Clara Curiel about a possible connection between the two diseases. Soon, other UA researchers became interested in trying to figure out why the connection exists. Torsten Falk, an assistant professor of neurology, Brian McKay, an associate professor of ophthalmology and vision science, and Lalitha Madhavan, an assistant professor in neurology, brought their expertise to answering the question.
The research is still in its infancy, Bowden said. The study that is the furthest along involves using technology that recently won the Nobel Prize in Physiology or Medicine by inducing pluripotent stem cells. These cells can make any cell in the body, but they’ve been controversial because in the past the only source was fetal tissue.
Obtaining biopsies from melanoma patients isn’t difficult, but you can’t take brain tissue from living Parkinson’s patients. Using induced pluripotent stem cells provides a workaround to biopsying the brain.
The new technology is “simple and beautiful,” Madhavan said. Researchers create brain tissue by regressing a biopsied skin cell back to the point where it could become any type of cell, making it pluripotent. By applying four different factors in a sequence, researchers can turn the clock back on the cell. From there, they can make the cell become any cell they want. The cell remains specific to the patient who donated the biopsy.
“The fact that (the technology) was given the Nobel award indicates that it is a very important technology,” Madhavan said. “It’s really changing the face of science.”
This technology will allow researchers to study the differences and similarities between skin cells from melanoma patients and the Parkinson’s brain cells made from the induced pluripotent stem cells, Madhavan said.
Researchers just finished collecting skin biopsies from patients with Parkinson’s, patients with melanoma and people without either disease. Both Bowden and his wife had biopsies taken.
The bigger picture
On a practical level, Bowden said, it’s important to get the message out to Parkinson’s patients that they should be screened for melanoma. Although melanoma is preventable, it is crucial to catch it early, as there are very few options once it spreads.
Exploring the unexpected connection between Parkinson’s and melanoma could also give scientists an at-risk population to study. The holy grail in Parkinson’s research is finding a way to slow the loss of brain cells, Sherman said. By the time people are diagnosed with Parkinson’s, however, they have already lost 70 percent of the specialized dopamine neurons in the brain.
Losing these cells hinders patients’ movement. “That’s a tough time for us to try to step in to do damage control because a lot of damage has already been done,” Sherman said.
If researchers could figure out who is at risk and develop tests to diagnose a pre-Parkinson’s condition, they might have a better chance of developing a therapy to protect the brain cells early, Sherman said.
Both Parkinson’s and melanoma have complex causes. The one known connection they share is that the cells affected in both diseases are pigmented.
In the past the presence of neuromelanin, a type of pigment, has been dismissed as an unimportant byproduct. That seemingly small connection is something worth revisiting, Sherman said.
The risk for melanoma may not be as simple as developing a sunburn, Sherman said. There may be complex mechanisms at work that link the two diseases.
Exploring those unexpected connections, he said, might give scientists a better understanding of both diseases.