Scientists have identified several genetic risk factors for prostate cancer, shedding new light on the cause of a leading worldwide cancer killer among men that hits U.S. blacks especially hard.
“The importance of it is that this is the first real evidence of the genetic basis of prostate cancer,” said Dr. Brian Henderson, dean of the Keck School of Medicine at the University of Southern California and one of the researchers of the study released on Sunday.
“It gives us the first real insight we’ve had into the cause of this disease and how we might do something about it,” Henderson added.
The researchers described seven genetic risk factors — DNA sequences present in some people but not others — bunched in a relatively small region of one of the human chromosomes, chromosome 8, that reliably predicted one’s probability of developing prostate cancer.
Five were newly discovered and two confirmed earlier findings.
The prostate, about the size of a walnut, is a gland below a man’s bladder that produces fluid for semen. According to the American Cancer Society, prostate cancer is the second leading cause of cancer deaths in men, behind lung cancer.
Pinpointing these genetic risk factors could be an important step toward helping explain the higher prevalence in U.S. blacks compared to whites, the researchers said.
Black men are twice as likely to die of the disease, and nearly all of the risk factors were seen most frequently in blacks involved in the study.
Henderson said the disease’s greater prevalence among blacks had hinted at some sort of a genetic basis for it.
The findings also could lead to ways to sort out who is at highest risk by finding if a man has one of the genetic risk factors, and for early diagnosis of the disease, the researchers said.
Prostate cancer death rates are falling in part because screening is allowing it to be found earlier when it is more treatable.
‘It's not all genetic’
“We do believe there is a genetic basis. Of course, it’s not all genetic. There are also going to be other lifestyle and environmental factors as well,” said Christopher Haiman, a USC preventive medicine professor.
“But our findings here in this study suggest that a large fraction of the disparity between African Americans and other populations could be due to genetic variation in this region,” Haiman said.
About two-thirds of cases are in men over age 65. The American Cancer Society said men who eat a lot of red meat or high-fat dairy products appear to have higher risk.
The three teams of researchers — one led by scientists at Harvard University and USC, one by Icelandic company deCODE genetics Inc. and one by the National Cancer Institute, part of the U.S. National Institutes of Health — presented their findings in the journal Nature Genetics.
The researchers examined genetic information on thousands of men with and without prostate cancer.
Harvard geneticist David Reich said that until last year, when deCODE published narrower earlier findings, there had been no confirmed genetic risk factors for prostate cancer.
“I think it’s likely there are other genetic risk factors either in this section of the genome or elsewhere that we and others have not yet identified,” Reich said.
“It’s only the beginning of the story,” Reich added.
Haiman said the researchers do not yet fully understand the biological mechanism through which the genetic variants influence risk for prostate cancer.