Researchers have created transgenic mice that have altered susceptibilities to developing cancer by knocking out a single gene.
The research in DNA structures called telomeres raises the prospect of a new approach to treating skin cancer in humans.
These structures, which hang from the ends of chromosomes, gradually wear away during the life of a cell until they reach a critical length that makes the chromosomes unstable and precipitates death. Cancer cells, it appears, gain their immortality by constantly repairing their fraying telomeres using an enzyme called telomerase.
The genes necessary to create this enzyme are present in all cells, but seem to be expressed only in sperm cells and cancer cells.
Maria Blasco, who has led research at the National Centre of Biotechnology in Madrid, found that by knocking out a gene called terc, which is involved in the production of telomerase, cancer cells were prevented from making the enzyme.
Transgenic mice produced in this way became resistant to developing tumours.
"The only way to test the importance of a gene in vivo is to genetically modify a mouse and see what effect this has. You can then speculate that the same effect may also happen in humans," Dr Blasco said.
This technique relies on fundamental similarities in genetics and biochemistry between mice and humans. Such studies can direct medical researchers towards potential therapies.
A boom in this kind of experiment is predicted as scientists use the human genome sequence and its murine equivalent, expected by the end of the year, to identify genes likely to be useful, and testable, targets.