DNA change can forecast cancer
A risk for a diseased prostate can predict other maladies, too
Hawaii and California researchers have found a key change in DNA increases the risk for prostate, colorectal and possibly other cancers.
"It would be quite remarkable if we find one particular defect increases the risk for a number of different cancers," Dr. Laurence Kolonel, University of Hawaii Cancer Research Center deputy director and program director for epidemiology, said in an interview.
"It doesn't mean this would be the only explanation, but it could be a contributing factor," he added.
Researchers at the University of Southern California's Keck School of Medicine led the study, reported in the April edition of Nature Genetics and its July 8 online edition.
Dr. Loic Le Marchand, Cancer Research Center of Hawaii researcher and professor, and Jennifer Yamamoto, formerly with CRCH, were co-authors of the study.
The scientists said one of seven genetic risk factors previously identified as increasing the probability of developing prostate cancer also increases the probability of developing colorectal cancer.
"This is an important finding because, for the first time, a common genetic risk factor for multiple cancers has been identified," lead author Christopher Haiman, Keck School of Medicine assistant professor of preventive medicine, said in a news release.
"There appears to be something fundamental occurring in this region that influences not only colorectal and prostate cancer, but perhaps cancers in general," he said.
That region on chromosome 8, one of 23 pairs of human chromosomes, does not have any known genes, Kolonel said. "So we don't know why mutations in that area of the chromosome would increase the risk for prostate cancer. But obviously, we and others have to find out what's going on in that area of the chromosome to account for why prostate cancer has increased."
Perhaps there is a gene in that area that has not been identified yet, he said. Or, a more likely possibility is that a regulator gene is controlling a gene outside the region, he said.
"It's really interesting," Kolonel said, "because it's an area on a chromosome which was identified as being important in the risk of prostate cancer several months ago, and it's been very hard to find any underlying genetic basis for prostate cancer."
Kolonel said the findings could "open up some new biology. ... We'll be learning about regions in the genome that don't contain any known genes, at least at this time." A lot of DNA has been called "junk DNA," with no function, he pointed out. "Maybe it is not so junk."
The USC and UH researchers and others are looking at the chromosome to see if the same genetic risk factors related to prostate and colorectal cancer are also associated with breast or any other cancers, Kolonel said.
Another recently published USC study identified variants in the same chromosomal region having a predictive role for the risk of developing breast cancer.
For the colorectal cancer study, the researchers genotyped six of the seven genetic risk factors identified as increasing prostate cancer risks.
They analyzed samples from 1,807 invasive colorectal cancer cases and 5,511 controls.
Samples came from five groups -- blacks, Japanese Americans, native Hawaiians, Latinos and European Americans -- included in the Multiethnic Cohort Study.
Kolonel and Brian Henderson, dean of the Keck School of Medicine, created the epidemiological study of more than 215,000 people from Hawaii and Los Angeles in 1993.
Henderson, co-author of the colorectal cancer study, said identifying genetic risk factors related to prostate and colorectal cancer risks "brings us closer to our long-term goal of developing a model that more precisely pinpoints who is at greater risk for developing colorectal, prostate and other cancers."