WASHINGTON — A new study shows how chemical tags on DNA may lead to higher rates of prostate cancer in black men. And estrogen may play a role, researchers reported June 12 at a meeting of the Endocrine Society in Washington, D.C.

“It may be that estrogen can reprogram the genome,” says study coauthor Wan-yee Tang of the University of Cincinnati in Ohio.

In black men, Tang and her colleagues found fewer of the chemical tags, called methyl groups, near the portion of DNA that encodes a gene active in the prostate than the team found in white men. The lack of these epigenetic tags may alter the gene’s activity and upset the balance of other proteins in the cell, making the cell more vulnerable to becoming cancerous, the researchers propose.

Earlier studies have shown that black men face a higher risk of prostate cancer than white men. Black men also have higher average levels of estrogen than white men. And experiments on rats have shown that high doses of estrogen take away methyl groups near the prostate gene PDE4D4, leading to abnormally high levels of the PDE4D4 protein.

Tang and her colleagues compared methyl groups among black and white men on a part of the DNA that controls the activity of PDE4D4. Cancer cells from white men had fewer methyl groups near the PDE4D4 gene than noncancerous cells. In cells from black men, though, both the cancerous and noncancerous cells had fewer methyl groups in the region, meaning that the pattern of methyl groups even in noncancerous cells looked like that of cancerous cells from whites. These methyl groups may be stripped away by higher levels of estrogen in black men, Tang and her colleagues suggest.

PDE4D4 protein keeps another molecule, called cyclic AMP, in check. Abnormal levels of cyclic AMP may ultimately increase the risk of prostate cancer, Tang says.

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