In this study, the research team genotyped 40 candidate genes known to be important for synthesis and metabolism of cholesterol in people who participated in a population case-control study of colorectal cancer in northern Israel. Included were 1,780 colon cancer patients and 1,863 people who did not have colorectal cancer, and many of the participants, who were predominantly Caucasian, had used statins for a long time. In the initial study, statin use was associated with a 50 percent relative risk of developing colorectal cancer in this population.
Included in the 40 genes were six SNPs, or DNA sequences, within the HMGCR gene, which produces a critical enzyme involved in formation of cholesterol.
They found one SNP within HMGCR that was associated with statin protection against colorectal cancer. A follow-up pharmacogenetic analysis showed that the protective association was significantly stronger among individuals with what they dubbed the "A" SNP allele, or variant, compared with people who had a "T" variant. Because a person inherits two variants, one from each parent, the stronger colorectal cancer protection came from individuals with the A/A HMGCR genotype, compared with those with the T/T genotype. Individuals with an A/T genotype had intermediate protection against colorectal cancer -- levels that varied between that seen for A/A and T/T genotypes.
Since genetic variants occur in different frequencies in different populations a lot of medical research that does not control for genetic variants ends up producing conflicting results depending on the genetic endowment of experimental subjects.
ďItís the exact same mechanism for lowering cholesterol as it is for lowering colon cancer risk. This is true only for those people who are actually taking statins. The gene test by itself doesnít predict whether youíre at an increased risk of colon cancer; it predicts only how well statins lower the risk,Ē Gruber says.
The researchers point out that itís easy to know if statins are successfully lowering cholesterol, but their effect on colorectal cancer prevention is not as apparent. Thatís where a gene test would come in.
Statins also cause harmful side effects in some users. If genetic testing can flag who will have bad reactions to statins and also who will have the most cancer reduction benefits then the argument for taking statins will become stronger for some while at the same time becoming much weaker for others.
This is part of a larger pattern in increased value from genetic testing. In just 5 years I expect the number of potential benefits from genetic testing to become very compelling.
|Share |||Randall Parker, 2010 April 21 11:38 PM Aging Genetics|