A combination of the fatty oils found in fish and a commonly used anaesthetic may form the basis of effective new drugs to treat breast cancer.
Oily fish has many health benefits
Researchers from Indiana University mixed compounds from omega-3 fatty acids with the anaesthetic propofol.
Together they appeared to reduce the growth of breast cancer cells, their ability to spread around the body and to form secondary tumours.
The research is published in the journal Breast Cancer Research.
The Indiana team studied the effect of two omega-3 fatty acids - docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).
Both have a minimal effect on cancer cells when applied alone.
But the researchers combined them with propofol, which was already known to inhibit cancer cell migration in a limited way.
They found that both the propofol-DHA and propofol-EPA combinations had a much more pronounced effect.
Not only did they block cell migration and the ability to adhere to potential new tumour sites, they also triggered some cells to commit suicide.
It is thought the fatty acids help to increase the absorption of propofol by the cancer cells.
Lead researcher Professor Rafat Siddiqui said it might eventually be possible to develop a patch or ointment containing the combination drug.
He told the BBC News website: "We would like to synthesize these compounds in larger quantities to use on animals in future studies so that we can test their effectiveness as a potential anti-cancer drug.
Omega-3 fatty acids, which are found in oily fish such as tuna, salmon, herring, sardines and mackerel, are already known to have many positive health benefits.
They are commonly recommended for maintaining a healthy heart, as they are known to reduce cholesterol levels.
Research suggests they may also protect against arthritis, lupus, and asthma and help people with bipolar disorder.
Dr Sarah Rawlings, of the charity Breakthrough Breast Cancer, said: "The potential of mixing these two compounds to enhance their anti-cancer properties is interesting.
"However, this research was carried out in cells and we don't yet know what the effect will be in women with breast cancer."
Ed Yong, of Cancer Research UK, echoed those comments, describing the findings as "promising".
Scientists from the Methodist Research Institute and Clarian Health Partners also worked on the study.