Scientists Found Cancer-Causing DNA in Stem Cells Given to Patients

For decades, stem cells have offered rich potential, promising an age of "regenerative medicine." They're being used to in early-stage treatment for Parkinson's disease, macular degeneration, hearing loss, arthritis, and paralysis, among others, with new applications (impotence?) appearing seemingly all the time. They're generally hailed as a motherlode for medical treatment, even as some unregulated clinics cross the line from research into dangerous hype.

But a recent letter in the journal Nature shows that some of the stem cell lines used in these therapies have been found to contain cancer-causing mutations. That raises the concern that patients treated with the cells could face a real risk of developing cancer—though that hasn't happened so far.

To reach that conclusion, Harvard scientists examined 140 stem cell lines, most of which were registered with the National Institutes of Health; each line is a collection of identical stem cells that's reproduced and provided to researchers. They performed DNA sequencing and found that five lines had cells with a cancer-causing mutation, specifically in the TP53 gene. Of those five, at least two have been used in clinical trials of experimental treatments. It's not known how many people received them.

This news doesn't mean that stem cell research is irrevocably damaged—and it isn't even the first time such mutations have been discovered. As STAT News notes, a similar study in 2011 found the same mutation, examining only a single line. Five out of 140 is also a small number, though that would probably matter little to anyone who developed cancer as a result.

But it does suggest the need for more research, and the development of safeguards. Right now, Food and Drug Administration doesn't require DNA sequencing of stem cells. Speaking to STAT, Jeanne Loring, the biologist who'd previously discovered the mutation, said even in the absence of regulations, researchers need to do right by their patients. "We need to use the tools we have to make sure we don't screw up somebody we're trying to cure, by giving them cancer," she said.

Ultimately, stem cell therapy is still in its early days; its tools are still in development. Finding these mutations is a reminder that pioneering researchers will need to be diligent when it comes to keeping their patients safe.

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