New Genetic Markers for Breast Cancer Discovered

BCRF-funded researcher Kenneth Offit, MD, MPH, who directs the Clinical Genetics Service at Memorial Sloan-Kettering Cancer Center in New York, and his colleagues have discovered a new marker that indicates an increased risk for breast cancer in women of eastern European Jewish ancestry.

The marker is a different from the known breast cancer-associated genes BRCA1 and BRCA2. Whereas women with the BRCA1 and BRCA2 gene mutations have a risk elevated by as much as 20 to 50 times, those with this marker, and others recently discovered, have only a 1.2 to 1.4 increased incidence. "It was a modest, but significant increase," Offit told Science Friday host Ira Flatow on March 7. "We and others working in this field have now looked at thousands of individuals and found 4 or 5 markers that appear to account for some of the cancers we've seen clustering in families."

The new findings, published recently in Proceedings of the National Academy of Sciences (PNAS), are important because researchers in the breast cancer field have observed that about one-half to two-thirds of families in which multiple incidences of breast cancer occur do not carry mutations of the known genes for increased risk, BRCA1 and BRCA2. These newly discovered markers begin to provide an explanation for tracking incidence of cancer within families.

What's to be done with this new information? Well, that's tricky for right now, admits Offit. "If this were a test available to the family of a patient [which it isn't currently], I wouldn't be encouraging them to even want to know this information. The first question will be: 'well what do I do about it?' And it doesn't change what families should be doing. It doesn't change their timing of getting mammograms or MRIs and I wouldn't recommend a surgery based on these tests," Offit explained.

What it boils down to is that Offit and his colleagues, researchers at the National Cancer Institute, and at other centers have added a new layer of understanding to the story of inherited cancers. They are looking to see if these markers act together to increase risk for other types of cancer as well.

Scientists have known for centuries about the hereditary nature of breast cancer. Genes are the inherited packages that affect specific traits in an individual - your eye color, and various other qualities of how you look. Certain inherited genes can also significantly change your predisposition for getting or not getting certain illnesses. But it's still an incomplete picture.

Genomics, on the other hand, is the study of the complete set of hereditary instructions for building, running and maintaining an organism. This makes genomic research more far-reaching than looking at specific genetic changes a person carries. Though each species has its own genome-a human genome is different than an elephant's genome, for example-genomes also belong to individuals. Slight differences between members of each species mean that patterns governing a living body may emerge, patterns broader than a collection of genes. This is what Offit and colleagues have hit upon with their new genetic markers.

"We believe that this is really the beginning of a process of uncovering probably hundreds of markers, not just for breast cancer, but for colon cancer, prostate cancer, diabetes, adult onset blindness and other ailments," Offit described. "Some are trying to directly market these tests today while research still continues, but we feel that in perhaps 5-10 years doctors will be offering entire genome scans for individuals. This is the beginning of an exciting new era."