Prostate cancer in African-American men is associated with specific changes in the IL-16 gene

A new study establishes the association of IL-16 with prostate cancer in men of both African and European descent. Previously identified changes in the gene for IL-16, an immune system protein, were associated with prostate cancer in men of European descent. But the same changes in the gene's coded sequence - called "polymorphisms" - did not confer the same risk in African Americans. Doubt was cast on IL-16's role in prostate cancer when researchers were unable to confirm that the IL-16 polymorphisms identified in whites were also important risk factors in African Americans. Researchers used a technique called imputation - a type of statistical extrapolation - that allowed them to see new patterns of association and identify new places in the gene to look for polymorphisms. They found changes elsewhere in the IL-16 gene that were associated with prostate cancer and were unique to African Americans. Polymorphisms result from DNA mutations and emerge in the ancestral history of different populations. People of African descent are much more genetically diverse than whites making the search for polymorphisms associated with disease more difficult. Although the effect of the particular changes to the gene appear to be different in men of African versus European descent, it is likely that several of the polymorphisms in the gene alter the function of the IL-16 protein.