WASHINGTON, Oct. 19 (Xinhua) -- One to 10 gene mutations on average are needed for a cancer to emerge, a new study said Thursday.
The results, published in the U.S. journal Cell, also showed the number of mutations driving cancer varies considerably across different cancer types.
For example, about four mutations per patient on average drive liver cancers, whereas colorectal cancers typically require 10 or so driver mutations.
"We have addressed a long-standing question in cancer research that has been debated since the 1950s: how many mutations are needed for a normal cell to turn into a cancer cell?" Peter Campbell, lead author from the Wellcome Trust Sanger Institute in Britain, said in a statement.
"The answer is -- a small handful," Campbell said.
The findings were based on a study of 7,664 tumours across 29 different cancers using a technique adapted from the field of evolution.
One of the striking findings was that mutations are usually well-tolerated by cells in the body.
This was surprising because mutations that individuals inherit from their parents are often poorly tolerated, and are generally lost from the human species over time.
In the body's cells, however, as a cancer develops, nearly all mutations persist without impacting on the survival of the cell.
In the study, the researchers also revealed that around half of these key mutations driving cancer occur in genes that are not yet identified as cancer genes.
"There is already much insight into the most important genes involved in cancer; but there are many more genes yet to be discovered," said Inigo Martincorena, first author from the Wellcome Trust Sanger Institute.
"We will need to bring together even larger numbers of cancers studied by DNA sequencing, into the tens of thousands, to find these elusive genes."
