A chemical that nerves use to talk to each other might help show which tumors are the most likely to spread, U.S. a new study suggests.

Gamma amino butyric acid, or GABA, is found at unusually high levels in some aggressive lung, thyroid, and prostate tumors, a team at Washington University School of Medicine in St. Louis found.

“GABA appears to be an indicator of a bad prognosis for these cancers,” Dr. Jeffrey Gordon, who led the study, said in a statement. “Usually these tumors are diagnosed only after they have spread to other parts of the body, but now we have the potential to recognize them before they metastasize.”

Writing in the Proceedings of the National Academy of Sciences, Gordon and colleagues said they used gene chips, which are small arrays that can detect dozens or hundreds of active genes at a time, on mouse cancer cells.

They looked specifically at aggressive neuroendocrine prostate tumors in the genetically engineered mice and found a characteristic “signature” of more than 440 genes in the most aggressive tumors.

Then they moved on to samples from human tumors.

“We took information about what genes were expressed in the mouse tumors, made computer-assisted predictions about what type of metabolism was going on in these abnormal cells compared to their normal noncancerous counterparts, and used new, powerful metabolite detectors to verify that these compounds were actually being made,” graduate student Joseph Ippolito said.

“We then took information gained from the mouse and asked whether the same human genes are expressed in poor prognosis as opposed to good prognosis human tumors.”

They were.

Their findings may change the understanding of some tumors, the researchers said. The cancer cells looked like primitive cells called neural progenitor cells.

This adds to a growing body of evidence that some cancers come not from adult cells gone haywire, but from damage to master cells called stem cells.