We should be able to put together a picture of the factors that convert a normal prostate into the most common cancer in men

Dr Jeffrey Trent

According to the Cancer Research Campaign, prostate cancer is likely to become the most common form of the disease in the developed world by the year 2020.

It is thought that about one in 10 cases of the disease is inherited.

Complicated system

The new breakthrough has been made by a team of researchers from the US National Human Genome Research Institute.

Researcher Dr Jeffrey Trent said: "The new finding presents a tantalizing clue about the workings of the complex genetic machinery that leads to this common cancer."

This is the first time that a single gene has been shown to influence inherited prostate cancer

Dr Simon Gamble

Previous research has identified a region of the human chromosome one as the place where genes linked to prostate cancer are most likely to be found.

The new study has pinpointed a gene found in this region called ribonuclease L.

The gene normally helps to keep cells healthy by defending them from viruses.

It also triggers cells that are about to become cancerous to commit suicide.

However, it appears that a defective version of this gene has no such ability, leaving cancerous cells to multiply unchecked.

The scientists screened DNA from 26 families prone to prostate cancer and found two families in which brothers with the disease had inherited defective copies of the gene.

Such inherited mutations are uncommon in the general population.

More genes

Lead researcher Dr John Carpten said that mutations of just one gene would not be enough to explain all forms of inherited prostate cancer.

He said: "This is not the only gene involved in prostate cancer.

"We know that mutations in any number of genes can lead to the development of prostate cancer, and this gene possibly represents a new member in the repertoire of prostate cancer genes."

Dr Trent agreed that it was likely that multiple genes were involved in prostate cancer.

He said: "As we identify them, we should be able to put together a picture of the factors that convert a normal prostate into the most common cancer in men."

Exciting discovery

Dr Simon Gamble, of the Prostate Cancer Charity, told BBC News Online: "This is the first time that a single gene has been shown to influence inherited prostate cancer.

"It is a very exciting discovery for two reasons, firstly it gives us a new insight into how prostate cancer grows and this may allow us to work out new ways of treating the disease.

"Secondly it is very important for predicting and detecting prostate cancer in families where the disease is common."

Dr Gamble said the discovery could make it possible to check men with the versions of the gene that contribute to prostate cancer on a regular basis for the first signs of the disease.

"This means that they are likely to be diagnosed before the disease has become advanced, which in turn means there is a much better chance of curing the cancer.

"There is probably a lot more work to be done, but this is the equivalent to finding the familial breast cancer gene and may have a great impact on saving lives in the future."

The research is published in the journal Nature Genetics.