Mice carrying a gene which appears to make them invulnerable to cancer may hold the key to safer and more effective treatments for humans. The new breed, created with a more active Par-4" gene, did not develop tumours, and even lived longer, said the journal Cancer Research. University of Kentucky researchers said a human cancer treatment was possible. Par-4 was originally discovered in the early 1990s working inside human prostate cancers, and is believed to have a role in "programmed cell death", the body's own system for rooting out and destroying damaged or faulty cells. The Kentucky team used an existing mouse breed known to be more vulnerable to cancers to test whether Par-4 could be used to fight them. They introduced the gene to mouse eggs, and it was active in both the resulting pups - and their own offspring. The mice with active Par-4 did not develop cancers, and lived slightly longer than those without the gene. Dr Vivek Rangnekar, who led the research, said that the gene offered a potential way, unlike most other cancer treatments, of destroying cancer cells without harming normal cells. "When a cancer patient goes to the clinic, they undergo chemotherapy or radiation and there are potential side effects associated with these treatments. We are thinking of this as a holistic approach that not only would get rid of the tumour, but not harm the organism as a whole." A spokesman for Cancer Research UK said: "Although at an early stage, research like this allows us to understand more about the faulty genes involved in cancer and throws open new avenues to explore for cancer treatment. It's important to remember that this work has only been done using genetically engineered mice, and more research is needed before we'll know if it can be translated to humans."