Minnesota Gene Pool Blog

Nicholas Wade reports in The New York Times today that scientists may be close to the end of the discovery phase in the quest for finding and characterizing genomic elements important in the etiology of breast cancer. These discoveries are the result of applying whole gene association analytical techniques to the problem.

Together with already known genes, the discovery means that a sizable fraction of the overall genetic risk of breast cancer may now have been accounted for, researchers say, and much of the rest could be captured in a few years.

The findings do not point to any new treatment and are too little understood to serve as the basis of a diagnostic test. But they are a critical step toward understanding the biology of breast cancer, scientists say, from which new treatments should emerge.

This last is especially important. Understanding the biology of breast cancer and other chronic diseases is likely the most important outcome of the Human Genome Project and will almost certainly have the greatest impact on prevention and treatment of this common condition. However, in the meantime, there may be opportunities to develop tools to help identify which women are at increased risk:

A team lead by Simon N. Stacey of DeCode Genetics reports that 25 percent of women of European descent carry one copy of a DNA variant on the second of the 23 human chromosomes, conferring a 44 percent greater risk of breast cancer than for women without it, and that 7 percent of women have inherited two copies, with a 64 percent greater risk.

However, not everybody is as enthusiastic about the implications of this new discovery. Mary Claire King, a researcher who was instrumental in discovering the first major gene associated with a predisposition for breast and ovarian cancer, BRCA1, comments:

Mary-Claire King, a biologist at the University of Washington in Seattle who pioneered the search for the BRCA1 cancer gene, criticized the statistical basis of the studies and suggested they should not have been published until the biological significance of the suspect sites had been established.

“I believe the motivation to publish based on so little biological or genetic evidence,� Dr. King said, “is that an enormous amount of money has been put into these efforts and hence the need to see positive results is huge.�

Dr. King’s principal criticism of the statistics of the three studies is that when 500,000 sites of variation are tested all at once for association with disease, many may come out positive just by chance, not because of any real link.

This will be a very interesting area to watch for further developments in the near future. The original reports are published online in Nature Genetics. You can read more about this here and here.