One of cancer’s deadliest tricks is its ability to spread to other organs. An existing cardiac drug has now been found to reduce the risk of metastasis by dissolving circulating clusters of breast cancer cells in patients.
Radiation and chemotherapy are effective at combatting cancer, but tumors can “leak” cells into the bloodstream, potentially seeding new tumors elsewhere in the body. This can lead to a kind of Whack-A-Mole game that drastically reduces the chance of a patient’s survival.
Finding ways to attack these circulating tumor cells (CTCs) could prevent new tumors from taking hold, and improve patient outcomes. In 2019, scientists at ETH Zurich tested more than 2,400 substances against CTCs in lab cultures. One of the most promising was a compound called digoxin, originally derived from foxglove.
Now, the team has tested it in human patients with metastatic breast cancer. In a small clinical study, nine patients received low doses of digoxin for one week. Sure enough, the number of cells per circulating cluster was found to decrease by an average of 2.2 cells. That might not sound like much, but the cluster populations are already fairly small, and size directly affects their ability to form new tumors.
“Breast cancer metastasis depends on CTC clusters,” said Nicola Aceto, principal investigator on the study. “The larger they are, the more successful they are.”
It seems that digoxin works by blocking ion pumps in the tumor cell membranes, which causes the cells to absorb too much calcium. This in turn makes the clusters fall apart.
The technique wouldn’t be enough to fight cancer on its own. Instead, it might be paired with radiation or chemotherapy which targets the primary tumor, while digoxin prevents the disease from spreading.
Although the study is small, it’s a promising step and the road to clinical use could be smoother than many. After all, digoxin is already used to treat cardiac conditions like heart failure and atrial fibrillation, so its safety profile is known. Other studies have shown that it could help with weight loss and inflammation.
In future, the researchers plan to develop other versions of the digoxin molecule that might be even more effective, and expand the study to other types of cancers that are prone to metastasizing.
The research was published in the journal Nature Medicine.
Source: ETH Zurich
