January 01, 2017
Much of what we know about prostate cancer comes from studies that primarily involved white men. Brady scientists have led the way in discovering that the disease is not the same in African American men.
It turns out that there are different genetic alterations in prostate cancer based on race. Several years ago, Brady scientists discovered that a tumor suppressor gene (which helps fight cancer) called PTEN is commonly lost in prostate cancer; moreover, when it is knocked out, the cancer tends to be more deadly. So striking was this finding that pathologist Tamara Lotan, M.D., and colleagues recently developed a simple, inexpensive test to look for the absence of PTEN in prostate tumors. To validate the test’s accuracy, Lotan’s lab teamed up with investigators from the Harvard School of Public Health to show in a large, population-based study that PTEN loss is associated with death from prostate cancer; their results were published in 2016 in the Journal of the National Cancer Institute (JNCI). “This test is available at the Johns Hopkins Hospital and is being used in selected prostate biopsies to help predict how aggressively the tumor is likely to behave,” says Lotan.
However: “It is important to note that most studies of PTEN have occurred in white men of European ancestry,” Lotan says. “Though African-American men have a higher risk of death from prostate cancer, it is unknown whether they might have a higher rate of some of the same genetic changes that have been linked to aggressive disease in white men.”
To address this question, Lotan and Brady resident Jeff Tosoian, M.D., M.P.H., compared the frequency of PTEN loss in African-American men and white men who underwent radical prostatectomy. They found that PTEN was lost significantly less oftenin African-American men — in 18 percent, as compared to 34 percent of white men. However, “similar to what we have seen in white men, the African American men who had PTEN loss had a risk of developing metastatic disease that was nearly four times higher than that of men who did not have PTEN loss.” Lotan suspects that different genetic aberrations — the loss of another protective gene, perhaps — may be involved in African American men. “Additional research is needed to identify these alterations, and to develop interventions aimed at each tumor’s genetic basis,” she notes, “leading us into an era of precision medicine.”