Medical Device Daily Washington Writer

GAITHERSBURG, Maryland — Medical researchers are beginning to unlock the genetic secrets of common diseases, such as asthma, diabetes, heart disease and cancer, by using genome-wide association studies (GWASs), an approach that involves rapidly scanning markers across the complete sets of genomes of many people to find genetic variations associated with a particular disease.

GWASs allow investigators to integrate, query, report and analyze significant associations between genetic variations and disease, drug response or other clinical outcomes. Such research is laying the groundwork for personalized medicine, experts from the National Cancer Institute (NCI) said during a seminar last week.

"We are in a very exciting boom time of discovery," said Stephen Chanock, chief of the NCI's Laboratory of Translational Genomics.

However, he said, GWASs are "just the start. It is not the end. It's not even the beginning of the end. Some would say it is the beginning of the beginning."

The NCI's Cancer Genetic Markers of Susceptibility (CGEMS) has been conducting scans of the entire human genome to identify common, inherited gene mutations that increase the risks for breast and prostate cancers.

The CGEMS study is using cases and controls from well-designed epidemiological studies to generate genotypes on more than 500,000 genetic variants.

In conducting a GWAS, investigators obtain DNA, usually from blood samples or harvested cells from swabbing the inside of the mouth, from people with the disease being studied and those without the condition. The DNA sample is scanned by automated laboratory machines, which survey each study participant's genome for strategically selected markers of genetic variation, or single nucleotide polymorphisms (SNPs), Chanock explained.

The genetic variations that are significantly more frequent in people with the disease are deemed as associated variations, which can be pointers to the region of the human genome where the disease-causing problem may reside. However, the associated variants may not directly cause the disease, which is why researchers take additional steps, such as sequencing DNA base pairs from the region of the genome to identify the exact genetic change involved in the disease.

Chanock noted that a big breakthrough for cancer research came in 2007 when GWASs demonstrated that an SNP in a region of chromosome 8, known as 8q24, was associated with prostate cancer risk.

GWASs have now identified more than 200 common marker alleles associated with over 70 common diseases, according to NCI researchers.

Patricia Hartge, deputy director of the NCI's Epidemiology and Biostatistics Program, noted that 8q24 also has been linked to breast and colon cancers.

In addition to the CGEMS prostate and breast cancers GWAS projects, NCI also is examining pancreatic cancer using the studies in a project known as PanScan.

The PanScan project involves a group of investigators from 12 prospective epidemiologic cohorts and one case-control study who are conducting whole genome scans of common genetic variants in order to identify markers of susceptibility to pancreatic cancer.

The PanScan researchers expect to publish their findings soon, Hartge said.

Sholom Wacholder, a senior investigator at NCI's Biostatistics Branch, noted that GWASs are a "radical departure" from traditional ways of conducting research.

But, he said, while GWASs represent a rapid advance in knowledge of genetic causes of disease, the science is not yet there in terms of fully predicting an individual's risk based on the studies.

"I don't think we are there yet," Wacholder said.

Therefore, he said, the public must be patient while awaiting the benefits of disease prevention and treatment based on GWASs. "We just need a little bit of time," he said.

GWASs in themselves do not provide the complete answers for curing cancers and other diseases, Chanock said. Rather, he said, they provide "more knowledge of where we need to expand our efforts."

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