National Cancer Institute
Building upon the successful completion of the Human Genome Project and applying its insights to cancer diagnosis, treatment, and prevention will require new tools that empower and connect the entire cancer enterprise. In addition to traditional single investigator/laboratory projects, NCI supports large projects that involve multi-disciplinary and multi-institutional teams of scientists. Both types of projects play critical and interconnected roles towards a single goal: rapidly translating new findings into effective new clinical practices.
Genome-wide association studies involve rapidly scanning a collection of known genetic markers across the complete genomes of many people to find genetic variations that are associated with a particular disease. By using regularly spaced genetic markers across the genome, researchers can rapidly hone in on areas that are altered in people with a particular form of cancer, identify the specific genetic changes, and develop better strategies to detect, treat, and prevent the disease.
Deciphering the human genome sequence was a watershed event early this decade, providing a fundamental blue-print for beginning to understand the genetic contributions to human health and disease, including cancer. However, what truly matters is to understand the effects of various differences on an individual's risk of developing cancer, on drug effectiveness for their tumor, and on their susceptibility to side effects. These genetic changes can also be used as markers for monitoring the progression of cancer. Although the technology for sequencing each person's genome remains prohibitively expensive, the work of many scientists—including those at NCI—has resulted in a catalog of common genetic variations across the human population (The International HapMap) that can be used as "landmarks" to quickly identify genetic elements relevant to cancer and therapy.
This new approach, known collectively as Genome-Wide Association Studies (GWAS), is resulting in a flood of data about the underlying molecular contributions to different forms of cancer and other diseases, and it is opening up exciting new opportunities for discovering and developing therapeutic interventions that go to the root causes rather than just the symptoms of cancer.
NCI is leading the application of this exciting new technology, known as whole genome association studies, to cancer in several different initiatives.
To carry out a genome-wide association study, researchers analyze the DNA of two groups of participants: people with the disease being studied and similar people without the disease. Each person's complete set of DNA, or genome, is placed on tiny chips and scanned on automated laboratory machines, which quickly survey each participant's genome for strategically selected markers of genetic variation, which are called single nucleotide polymorphisms, or SNPs.
If certain genetic variations are found more frequently in people with the disease compared to people without disease, the variations are said to be "associated" with the disease. The associated genetic variations can serve as powerful pointers to the region of the human genome where the disease-causing problem resides.
However, the associated variants themselves may not directly cause the disease. They may just be "tagging along" with the actual causal variants. For this reason, researchers need to take additional steps, such as sequencing DNA base pairs in that particular region of the genome, to identify the exact genetic change involved in the disease.
