Testicular Cancer

Testicular Cancer

Gene for Testicular Cancer discovered

A consortium of international scientists said they have located the first gene for susceptibility to testicular cancer. British researchers who led the study said the gene dubbed TGCT1 on chromosome X is inherited from the mother and can increase a man's risk of testicular cancer by up to 50 times. The finding brings scientists a step closer to finding the gene, which could lead to earlier detection, treatment and cure of the most common cancer among young men. "What we have achieved is the localization of the first testicular cancer susceptibility gene."

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"This work will be facilitated enormously by the newly emerging genome sequence, the first draft of which we expect to see late this year," Stratton added, referring to the Human Genome Project, which will map all the genes in the human body.

Testicular cancer affects about one in 500 men and is most common among men aged 25 to 29. The disease has increased steadily since the 1930s. Cases in Denmark, which along with Switzerland and Norway have the highest rates in the world, have trebled. Familial testicular cancer accounts for an estimated 20% of cases, so scientists know that other genes are also involved.

Doctors also suspect that environmental factors and exposure to higher levels of the female hormone estrogen in the womb are contributing factors to the increase in the disease. The scientists working for the International Testicular Cancer Linkage Consortium located the TGCT1 gene by studying 134 families worldwide with two or more cases of the disease. It is found in a third of families with a history of the disorder. The finding, which is the culmination of 10 years of research, is published in the journal Nature Genetics. In addition to improving detection and treatment of testicular cancer, which has a 90% to 95% cure rate if found early, Stratton said the discovery has wider implications for other cancers with higher death rates.

"Testicular cancer is unusual because of its high cure rate. By finding out more about the molecular biology of the underlying causes and its pathogenesis, we hope to be able to work out why it is so curable," he said. "The implications of that may be that we can see why other cancers, which are not so curable, are different." Risk factors for testicular cancer include a family history of the disease and malformed or undescended testicles. There is also a higher incidence among first-born sons and non-identical twins. Exercise may increase testicular cancer risk.

Teenage boys who exercise regularly and those with physically demanding jobs in their 20s may be more likely to develop testicular cancer than their less active counterparts, Canadian researchers report. The most common cancer in men 15 to 35 years old, testicular cancer rates have increased in many countries over the past 20 years.

To arrive at their findings, the researchers compared data on 212 men with testicular cancer and 251 similar, cancer-free men. The study subjects filled out questionnaires identifying the frequency of "moderate" or "strenuous" exercise during different life periods. Moderate exercise refers to brisk walking or gardening while strenuous exercise referred to any exercise lasting for at least 20 minutes.

Reporting their findings in the January issue of the American Journal of Epidemiology, Drs. Nancy Kreiger and Anil Srivastava of the University of Toronto in Ontario, Canada, found that the more frequently men exercised in their teens, the greater their risk of developing testicular cancer. In addition, men who had moderate or strenuous job demands in their 20s had about a 70% to 85% increased risk of testicular cancer, compared to men who did not work at such jobs during their 20s, the authors note.

The researchers originally speculated that physical activity would lower risk of testicular cancer. "The finding of a harmful effect of physical activity is contrary to that of our original hypothesis," Kreiger and Srivastava write. While exactly how physical activity may increase testicular cancer risk is not known, the investigators suggest that perhaps physical activity during the teen years delays puberty in boys. This may cause changes in levels of male hormones and may somehow increase risk of the cancer.

"Important insights might also be gained from further investigation of the relation between hormone levels and physical activity, particularly with respect to frequency of exercise," they conclude.

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