Researchers at the University of North Carolina (UNC) have discovered that a common lab molecule, used to label DNA, can trigger a runaway process that eventually leads to cell death. But the team says this could have a positive use too, as a potential cancer treatment.

The molecule in question is known as 5-ethynyl-2′-deoxyuridine (EdU), which was designed as a chemical stand-in for thymidine, a key nucleoside in DNA. The advantage of EdU over the natural version or other alternatives is that it has a receptor that fluorescent molecules can easily bind to, allowing scientists to label DNA and track changes during processes like cell division.

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However, EdU was known to be moderately toxic to cells, although the specific mechanism for that effect hadn’t been identified. In previous work the UNC team noticed that DNA that had been labeled with EdU seemed to invoke a repair response, even in the absence of triggers that normally damage DNA. So for the new study they investigated why that occurs, and found that it creates a feedback loop that can ultimately end with the death of a cell.

Read more: New Atlas