Researchers have described how a common genetic variation may be involved in the development of prostate cancer. The variant occurs in a gene known to be involved in prostate function. The study, which included a team of researchers at the National Cancer Institute (NCI), part of the National Institutes of Health, uncovered how a small change in the DNA of the gene impacts the biology of prostate cancer risk. The study was published online April 20, 2009, in Proceedings of the National Academy of Sciences.

Differences in the sequence of DNA among individuals are called genetic variations, and some known variations have been associated with an increased risk of certain diseases, such as prostate cancer. The most common type of genetic variation is a change in a single nucleotide, or base, which is one of the building blocks of DNA. Such single-nucleotide polymorphisms (SNPs) are used in genome-wide association studies of large numbers of individuals with and without a disease to identify DNA regions that are associated with the disease. Although previous studies have identified regions of the genome that are associated with prostate cancer risk, this study was one of the first to explain the biological mechanism underlying the difference in risk among individuals.

Recently, two independent genome-wide association studies of chromosomal regions associated with prostate cancer risk identified a SNP located in a region of chromosome 10 that plays a role in the expression of the gene MSMB. This gene produces a protein that is a potential biomarker for prostate cancer and may also act as a tumor suppressor protein. Previous research has shown that the expression of MSMB declines progressively as prostate cancer advances from early to late stages.
In the new study, the team investigated how the SNP may be related to MSMB function and the development of prostate cancer. They first verified that the SNP is associated with prostate cancer risk. To do so, they compared a region of chromosome 10 that included the SNP and MSMB in blood samples collected from 6,118 men with prostate cancer and 6,105 men without prostate cancer from NCI's Cancer Genetic Markers of Susceptibility (CGEMS) project. This analysis confirmed the strong association of the SNP with prostate cancer.

The team next examined how the two identified variants, or alleles, of the SNP affected the expression of MSMB. The SNP is found as either a C allele or a T allele. This means that some people may have a thymine (T) base at that place in their DNA, whereas other people have a cytosine (C) at that location.

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