For years it’s been widely recognized as a successful medication in the treatment of irregular heart rhythms. Now studies show digoxin [di-JOX-in] might also be a cancer-fighting agent.

Published in the Proceedings of the National Academy of Sciences, the report indicates that because digoxin reduces levels of a protein that helps cancer cells survive, the afflicted cells die. Researchers demonstrated this by treating prostate cancer cells in a laboratory setting with digoxin and then observing significantly slower cell growth than in those not treated. Three days later there were fewer cancer cells and many cells had stopped growing altogether, compared with untreated cells.

Researchers then tested laboratory animals, injecting digoxin into mice with tumors. In the untreated mice, tumors could be felt after only nine days. But in those injected with digoxin, fifteen to twenty-eight days passed before the tumors grew big enough to be felt.

The researchers also looked at levels of the protein and noted that in the tumors of treated mice, the amount present was lower compared with the amount found in untreated mice. They concluded, therefore, that it was digoxin that reduced protein levels, slowing tumor growth.

Digoxin has been investigated before. In one study of nine-thousand patients taking digoxin, a strong correlation was found between high levels of the drug and a lower risk of leukemia, lymphoma, and kidney and urinary tract cancers.

Future research will compare digoxin’s cancer-fighting ability with its classic characteristic of regulating heart rhythm to hopefully improve both capabilities.