A group of Italian researchers have discovered that tiny molecules called microRNAs (miRNAs) from zebrafish embryos can slow down the spread of aggressive breast cancer, according to a study published in the International Journal of Molecular Sciences on April 17, 2025.
These findings could potentially apply to many types of cancer, offering a new way to fight the disease by making cancer cells less harmful. In simple terms, the study shows that these zebrafish molecules can change how cancer cells behave, making them less likely to move and invade other parts of the body. Cancer cells often act like they’re on the move, breaking away from their original spot to spread to other parts of the body. This movement is driven by a system in the cells called the PI3K pathway, which acts like a gas pedal, pushing the cells to grow and move. The zebrafish extracts contain a specific miRNA called miR-218-5p, which acts like a brake. It slows down the PI3K system, calming the cancer cells. This leads to changes inside the cells: they stop forming structures that help them move, and they start sticking together like normal cells, forming a tissue-like structure. The extracts also boost a protein called p53, which helps stop cancer growth, and lower another protein called TCTP, which cancer cells use to keep growing.
The study focused on extracts from zebrafish embryos, which are tiny developing fish used in research because they share many genes with humans—about 70 to 82% of their genes are similar to ours. The researchers took these embryos at different growth stages, from early (5 hours after fertilization) to later stages (19 hours), and collected their miRNAs, which are small molecules that control how genes work. They tested these extracts on a tough type of breast cancer called triple-negative breast cancer (TNBC) and on normal breast cells made to act cancerous with a chemical called TGF-β1. The results showed that the extracts, especially from later embryo stages, stopped cancer cells from growing quickly, moving, and invading other tissues.

The study found that after 96 hours of treatment, the breast cancer cells moved 78% less and invaded 45–55% less compared to untreated cells. They also looked more like normal cells, with stronger connections between them, thanks to proteins called E-cadherin and β-catenin. These changes make the cancer cells less dangerous, as if they’re being reprogrammed to act less like cancer and more like healthy cells.

Could this work for all cancers? In theory, yes, for many types, because the PI3K pathway is a common driver in cancers like lung, colon, prostate, ovarian, and pancreatic cancer. This pathway helps cancer cells grow and spread, so slowing it down with miR-218-5p could help in these cancers too.

This research is promising because it suggests a new way to fight cancer by using nature’s own molecules to calm cancer cells down. While it’s too early to say it will work for every cancer, the findings open the door to testing this approach in other types, like lung or prostate cancer, where similar processes drive the disease. More studies are needed to make sure these miRNAs are safe and effective in people, but the idea of using fish embryo molecules to reprogram cancer cells is a step forward.

Source.