A single gene may protect its carrier against a variety of cancers, according to new research.
The gene may protect against various cancers
Two variants of the B-MYB gene carried by up to half of the world's population are found less often in people with cancer, the journal Oncogene reports.
The Institute of Child Health's Dr Arturo Sala said it might prove a "key player" in cancer.
Charity Cancer Research UK said that further research might explain how it might help prevent the disease.
Other research had already pointed to B-MYB having a role in the spread and development of cancer.
It has been found to be over-active in many different types of cancer.
The latest research, funded by SPARKS and the Neuroblastoma Society, looked at more than 400 patients with either colon cancer, a brain tumour called neuroblastoma, or chronic myeloid leukaemia.
Their version of the B-MYB gene was analysed and compared to the versions found in 230 "controls" - volunteers with no known cancer.
They found that the cancer patients were half as likely to carry the gene variants in question compared with the controls.
Dr Sala said: "This would suggest that we have found a key player in the genetic influences in cancer. Although the results are statistically significant, we would certainly want to see the scale of the effect confirmed in a much larger study.
"People who carry these gene variants might well be protected against cancer."
The percentage of people in the population who carry the potentially beneficial variants varies between ethnic groups.
As many as 50% of people in Africa may carry it, and perhaps slightly fewer in Europe and the US.
It is one of the most commonly held gene variants so far which has been found to be potentially protective against cancer.
Henry Scowcroft, Cancer Research UK's senior scientific information officer said: "There's a huge effort going on around the world to identify the genetic variations that affect people's risks of cancer, and Cancer Research UK is heavily involved with this work.
"If confirmed in larger studies, the existence of a genetic variant that can reduce the chances of cancer in people who carry it is very exciting.
"Discovering exactly how it might protect against the disease could allow researchers to explore new avenues of cancer prevention. But it's still early days."