Scientists Find Gene Clue to Prostate Cancer

SOME men may be genetically more prone to the harmful effects of cancer-causing agents, according to a study published in the British Journal of Cancer today* (Tuesday).

US researchers looked at variations in a gene that controls the body's response to carcinogens and hormones natural to the body. They found men with prostate cancer often had a different version of the gene than men who were not affected by the disease.

Scientists believe their findings may hold important clues in understanding what environmental factors may trigger the development of prostate cancer and why some men are more susceptible to the disease than others.

Prostate cancer is the most common cancer in men but the cause of the disease remains a mystery. Variations in incidence rates around the world suggest that environmental factors, as well as genetic differences, may increase the risk of the disease. The high rates of the disease found in developed countries, for example, has been linked to the western diet, particularly its high animal fat content. Other environmental factors that may increase the risk of the disease include, low dietary intake of selenium and exposure to radiation or a chemical called cadmium.

Dr Jianfeng Xu, from the Wake Forest University School of Medicine in North Carolina, says: "Previous research suggests prostate cancer arises in certain individuals due to a combination of genetic and environmental factors. Our study suggests that the genetic make-up of some men leaves them more susceptible to potential carcinogens in the environment or hormones in the body that could trigger the disease."

Dr Xu and his team, in collaboration with Dr William Issac's team at Johns Hopkins University, analysed a gene called CYP1B1, which is thought to play an important role in the development of cancer.

Previous research has suggested certain variations in the gene may increase the risk of smoking-related head and neck cancer, bowel, breast and ovarian cancers.

CYP1B1 normally plays a dual role in the body, and therefore has been suggested to both cause cancer and prevent it. The gene helps the body eliminate environmental chemicals that can cause cancer but can also activate some hormones, turning them into cancer causing agents. This could be particularly relevant to prostate cancer because its development is strongly dependent on hormones such as testosterone.

Researchers think tiny variations in the gene alter its function, with some increasing the cancer causing effects of the gene and others enhancing its ability to prevent cancer.

The team looked separately at 13 variations in CYP1B1 and clusters of these variations commonly found in Caucasian male populations. They compared their frequency in 160 Caucasian men who had inherited prostate cancer, 250 prostate cancer patients without a family history and 220 who did not have the disease.

They found that one cluster of variations in the gene was more common in men with prostate cancer who had no family history of the disease, while another combination appeared more frequently in men who did not have the disease.

Based on this study, scientists now have preliminary evidence that a particular version of the CYP1B1 gene increases the risk of prostate cancer. This information will help them better understand how changes in the gene alter its dual functions in the body, and find ways to stop its cancer causing effects.

Dr Xu says: "This study suggests men with a particular gene variant have an increased risk of prostate cancer. It's an exciting finding because we know the gene interacts with certain cancer-causing chemicals - studying this more closely will bring us closer to finding out what factors in the environment or within the body may trigger the disease."

Professor Alex Markham, Chief Executive of Cancer Research UK, which owns the British Journal of Cancer, says: "Prostate cancer is the commonest cancer in men in the UK, but currently little is known about what causes the disease.

"It's important to find out how genetic and environmental factors combine to cause prostate cancer as, in the future, this will allow us to identify people at high-risk and advise them on ways to prevent the disease."

*British Journal of Cancer Volume 89; Issue 8