A groundbreaking study published in Nature Medicine highlights a promising new approach to combat the spread of cancer by targeting tumor cell clusters. These clusters, formed by circulating tumor cells (CTCs) in the bloodstream, play a crucial role in the development of metastases. By settling in other organs, these clusters grow into new tumors, making metastasis a major obstacle in cancer treatment.

The research focused on metastatic breast cancer, a condition where metastasis drastically reduces survival rates. The team administered low doses of digoxin—a medication commonly used for heart conditions—to nine patients over the course of a week. The results showed that digoxin significantly reduced the average cluster size by 2.2 cells. While this may seem small, it represents a meaningful reduction, as cluster sizes are typically limited, and fewer cells per cluster mean a lower risk of metastatic spread.

Digoxin’s mechanism is tied to its ability to block sodium-potassium pumps (Na+/K+-ATPases) on tumor cell membranes. This causes cancer cells to absorb more calcium, weakening the bonds between cells in the cluster and causing them to break apart. However, digoxin alone is not a standalone treatment; it must be combined with therapies that kill cancer cells to effectively tackle the disease.

This discovery builds on previous findings from 2019, when researchers screened over 2,400 substances to identify agents capable of breaking apart CTC clusters. Digoxin emerged as a potential candidate. Now, researchers are working on designing new molecules based on digoxin’s properties to create even more effective therapies. ETH spin-off Page Therapeutics is leading efforts to develop these next-generation compounds.

The implications of this research extend beyond breast cancer. Future studies aim to explore whether similar treatments could help prevent metastasis in other cancers known for spreading aggressively, such as prostate, colorectal, pancreatic cancer, and melanoma.

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