Scientists have bred a family of "supermice" that are highly resistant to cancer.
Supermice were resilient to cancer
The mice have three instead of two copies of genes that keep cell division in check.
It might be possible in the future to make a drug for humans that would confer the same protection against cancer, the Spanish scientists hope.
The team at the Spanish National Cancer Centre in Madrid report their findings in Genes and Development.
Cell growth and division is normally kept under control by a group of gatekeeper genes called tumour suppressors.
In cancer, cells grow out of control and invade, erode and destroy normal tissue.
Dr Manuel Serrano used DNA technology to breed mice that had an extra copy of part of the tumour suppressor genes called Ink4a/ARF locus.
This locus controls the production of two proteins that together appear to stop most human cancer cells developing.
These 'supermice' were found to be extra resistant to things known to trigger cancer, called carcinogens, in normal mice.
When the animals were exposed to various carcinogens they developed tumours at a much lower rate than normal.
What's more, the presence of the extra copy of the locus and increased cancer resistance had no apparent effect on the lifespan or fertility of the 'supermice'.
Dr Serrano attributes the increased tumour resistance to the modest increase in the levels of the two proteins gained by the extra copy.
He suspects some humans might inherit extra resistance to certain cancers.
He said it might be possible to induce similar tumour protection in humans using a drug, although this would be some time away.
He said: "This may translate in a big benefit regarding cancer susceptibility."
Hazel Nunn of Cancer Research UK said: "As people who inherit a defective copy of this gene are susceptible to cancer, it might be anticipated that an extra working copy would reduce the risk of this disease.
"This is exactly what the research has shown in mice.
"It is very encouraging to have such clear confirmation on which to base future research into how this gene works.
"Ultimately, we hope this knowledge can be developed for the benefit of the cancer patient."