Scientists at the Memorial Sloan-Kettering Cancer Center in New York say they have identified four genes that make breast cancer spread fast and into the lungs. The four genes work together.
Turning off all four genes at once dramatically reduces the ability of breast tumors to spread - or metastasise - a study in mice showed.
Reporting the results in Nature, the US team said they were planning clinical trials of drugs known to target two of the genes in the set.
Once the cancerous cell breaks free, they travel down the bloodstream to other sites in the body. There is no stopping them thereafter.
Only when this metastatsis process is checked, there is any chance of survival for the patient.
In a series of experiments, Dr Massague of the Memorial Sloan-Kettering Cancer Center identified four of those genes that produce proteins which, in turn, combine to enable the cancer cells to escape into the bloodstream and get into the lungs.
Knocking out each of the genes individually in human cancer cells that had been implanted in mice had a small effect on cancer growth and metastasis.
But remarkably, turning off all four genes at once almost eliminated tumor growth and spread. The tangle of blood vessels that is normally seen in a tumor was greatly reduced.
Injecting cancer cells that had all four genes turned off into the bloodstream of mice also showed that the cells lacked the ability to get into lung tissue.
Two drugs known to inhibit two of the proteins produced by the genes - cetuximab and celecoxib - were also shown to reduce the growth and spread of the breast tumors in mice if used in combination.
Discussions are underway for clinical trials in humans.
Dr Massague, chair of the cancer biology and genetics program at the Sloan Center said: "We found that the combination of these inhibitory drugs was effective even though the drugs individually were not very effective.
"This really nailed the case that if we can inactivate these genes in concert, it will affect metastasis."
"These genes are used together to attract blood vessels and enter the blood stream and then once they reach the lung, they use the same strategy to enter the lungs."
Dr Massague is also looking at which genes promote metastasis to other sites in the body, such as brain and bone and whether the same or similar genes are involved in cancer spread in other cancer types, such as colon cancer.
"It is not known if the same genes are involved in the spread of all cancers, but this work is a great starting point for scientists looking at this important area of research, " said Dr Anthea Martin, cancer information officer at Cancer Research UK.