Only a small proportion of men who carry the high-risk alleles will develop the disease. The key now, the researchers say, is to find out what modifies the genetic risks and pushes one individual toward cancer while another remains disease-free. By using the newly-discovered genetic risk factors as a lens, Nathanson and Kanetsky believe they may now be able to reveal critical environmental factors that would otherwise be lost in cloud of confounding information.

"We are very interested in how genes and environmental factors work together to increase one's risk," Nathanson says. "Now that we know something about the genetics, we hope to now build a better model of who is at risk by looking at gene-environment interactions."

Additionally, the new findings may begin to explain why white men are more often diagnosed with testicular cancer than African American men. KITLG is involved in pigmentation “ “ and the version of this gene associated with testicular cancer is common in the white population but much less common in the black population.

Finally, Nathanson says the findings show that previous models of testicular cancer formation are correct and underscore why men with testicular cancer may also have fertility problems. "Researchers have postulated testicular cancer was a disorder of germ cell development or maturation, and they were right," she says. "The KITLG gene is critical for germ cell development and maturation."

med.upenn/