November 3, 2008

Researchers Identify Gene That Raises Lung Cancer Risk

An international team of researchers reported on Sunday they have identified two genetic variations that appear to increase a person's risk of developing lung cancer by up to 60 percent.

Those researchers also identified another gene in April that raised lung cancer risk and said their latest finding was relevant for both smokers and non-smokers.

Paul Brennan, a cancer epidemiologist at the World Health Organization's International Agency for Research on Cancer, noted that they are looking at differences in the DNA that makes people more or less likely to develop lung cancer.

"The idea is if you can identify genes then that might indicate why people develop lung cancer."

The American Cancer Society said lung cancer is the leading cause of cancer death in men and the second leading cause of cancer death among women worldwide, with about 975,000 men and 376,000 women forecast to die annually.

Although smoking is the leading risk factor, scientists are looking to genetics to help explain why some long-time smokers never develop the disease and why some non-smokers do.

For the study, researchers from 18 countries analyzed genetic mutations in more than 15,000 people -- 6,000 with lung cancer and 9,000 without the disease.

A region on the fifth chromosome was discovered containing two genes -- TERT and CRR9. Scientists say the variations possibly boost the likelihood of lung cancer by as much as 60 percent.

"We are looking at versions of genes that everybody has," Brennan said.

Brennan said they don't know much about CRR9, but pinpointing the TERT gene is promising because it activates an enzyme called telomerase, which is key to aging and cancer.

Cancer is caused by defects in DNA, the basic genetic material. All chromosomes, which carry the DNA, also have little caps on each end called telomeres.

These telomeres become a little more frayed each time a cell divides. When they are too worn out, the cell dies.

But cancerous cells produce telomerase, which can renew the telomeres and lets the cells reproduce out of control, eventually to form a tumor.

Brennan added that implicating the TERT gene in a specific cancer can help lead to a better understanding of how cancer develops and boost the design of new drugs to stop tumors.

"The principle is there," he said. "If one can identify what goes wrong, it may be possible to identify targeted drugs."

The study was published in the journal Nature Genetics.


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