EVEN a cancer gene may have a good side. A study of people with African ancestry has revealed that a gene associated with cancer shows a pattern of variability that suggests it benefits carriers.

Alkes Price at the Harvard School of Public Health and Gaurav Bhatia at the Massachusetts Institute of Technology studied the genomes of more than 12,000 African-Americans, Nigerians and Gambians. They were broadly similar, but sections of DNA within four genes were remarkably variable between populations.

“They really stood out,” says Bhatia. Such variation implies that the four genes have evolved separately in each population in response to local pressures. In three of the genes, that evolution is known to have improved local resistance to malaria. The fourth gene, unexpectedly, turned out to be PSCA – a gene whose activity is strongly associated with bladder and prostate cancer (The American Journal of Human Genetics, DOI: 10.1016/j.ajhg.2011.07.025).

“We presume this mutation also confers some benefit to those who carry it,” says Price, although he adds that it’s not yet clear what those benefits are.