Researchers said they had discovered a type of tumour cell which spreads cancer from organ to organ.
Spanish scientists announced Wednesday they may have identified a way to stop cancer from spreading, at least in mice, and said it could be linked to eating fat.
Writing in the journal Nature, the team said they had discovered a type of tumour cell which spreads cancer from organ to organ -- a process known as metastasis, which is what makes the disease so deadly.
They also found that the cells carry a receptor, dubbed CD36, known to regulate the uptake of fats.
In experiments with mice given human tumours, metastasis was "significantly reduced" by using antibodies to block the CD36 receptor, the researchers said.
This worked for human mouth, skin and breast cancer.
In some rodents, metastatic cells were completely wiped out, said the team, enthusing that "things like this don't happen every day".
Receptors are protein molecules on cells which receive instruction-carrying chemical signals from outside.
In further tests, mice with CD36-rich cells and fed a high-fat diet developed more, and larger, metastases than their cousins on normal diets, the researchers said.
Metastasis happens when cancer cells break free from a tumour and travel through the blood or lymphatic system to establish new colonies elsewhere in the body.
An estimated 90 percent of cancer deaths happen due to metastasis, the research team said.
Not all cancer cells do this, however, and being able to identify and kill the ones that will travel is a top priority in cancer research.
The latest findings make CD36 a possible target for anti-cancer drugs, the researchers said.
But they stressed the discovery was a "long way" from finding application in human medicine.
The antibody used in the experiments does not yet exist in a format fit for human use.
"Ours is a new step that we hope in the future will not only contribute to our better understanding of how and why tumours generate metastasis, but also to devise ways to attack these metastatic cells," study leader Salvador Aznar Benitah of the Institute for Research in Biomedicine in Barcelona told AFP.
"We are developing new blocking antibodies for human use that we hope to be able to test in a relatively short period of time (between four and ten years) in patients," he explained by email.
More work is needed to confirm the role of fat and diet in cancer metastasis in humans, added Benitah.
"But these results are certainly a warning sign, since they strongly indicate that metastatic cells are exquisitely sensitive to the fatty acids we consume in our diets."
Outside experts described the findings as "significant" but said it was too early to understand the implications for human cancer.
"Mouse models give us important clues to understanding biology, but the findings in mice do not always transfer to humans," said Paul Pharaoh, professor of cancer epidemiology at the University of Cambridge.
As for the fat link, observers underlined that human and mouse diets were nothing alike.
"There is no evidence that adopting a low-fat diet or excluding certain fats will help slow the spread of cancer in patients," said Emma Smith of Cancer Research UK.
Cancer patients need many calories to cope with the physical toll taken by therapy.