A commonly-used heart drug derived from the foxglove plant can “dissolve” clusters of breast cancer cells to prevent the disease spreading, a study suggests.
Certain tumour types release cancer cells into the blood which can cluster together and settle into other organs, causing further tumours known as metastases.
Around 60,000 women are thought to live with secondary breast cancer caused by this process in the UK.
Swiss researchers investigated the effect of cardiac medication digoxin in nine patients with metastatic breast cancer who took a daily low dose for one week.
They found that the number of cancerous cells per cluster decreased significantly by an average of 2.2 cells.
The researchers, from ETH Zurich, the University Hospitals of Basel and Zurich, and the Basel-Land Cantonal Hospital, said smaller clusters were less likely to spread cancer.
Study leader Professor Nicola Aceto, an expert in molecular oncology at ETH Zurich, said: “Breast cancer metastasis depends on circulating tumour cell clusters.
“The larger they are, the more successful they are.”
Digoxin is derived from the highly toxic foxglove plant and usually used for heart conditions such as heart failure and abnormal heart rhythm.
It is thought to work against cancerous cells by targeting their Achilles’ heel – sodium-potassium pumps located in the membranes of tumour cells which are responsible for transporting sodium out of the cells and potassium into them.
Digoxin blocks these ion pumps so the cells absorb more calcium from the outside of the cell membrane. This weakens the cohesion of the cancer cells in the cluster, causing them to fall apart.
However, digoxin alone cannot eliminate the existing tumour and the drugs would need to be used in combination to kill the cells.
Researchers now plan to develop new molecules based on digoxin that are even more effective at dissolving the clusters.
The findings were published int he journal Nature Medicine.
