The study is reported June 30 in the journal Nature.
The researchers studied ovarian tumors from 500 patients with serous adenocarcinoma. This is the most common form of ovarian cancer and accounts for about 85 percent of deaths from the disease. The researchers sequenced the protein-coding genes in more than 300 of the tumors and carried out additional genetic studies on nearly 175 tumors.
“For the first time, we are able to take a close look at the genetic changes that underlie ovarian cancer,” says co-author Richard K. Wilson, PhD, director of Washington University’s Genome Institute. “We have compiled a short list of mutations that occur commonly in ovarian tumors as well as a much longer list of mutations that occur much less frequently. This new knowledge sets the stage for future discoveries to help improve the diagnosis and treatment of this devastating disease.”
Wilson and his colleagues at The Genome Institute also are sequencing the entire genomes of ovarian cancer patients and their tumors. This ongoing work is expected to provide a more complete understanding of the full spectrum of mutations involved in ovarian cancer.
In the current study, the researchers confirmed that mutations in a single gene, TP53, are present in more than 96 percent of all ovarian serous adenocarcinomas. The gene produces a protein that normally prevents cancer from developing, and mutations in the gene contribute to the uncontrolled growth of ovarian cells. In addition, the researchers discovered a multitude of less-frequent mutations in other genes.
“This landmark study is producing impressive insights into the biology of this type of cancer,” said National Institutes of Health (NIH) Director Francis Collins, MD, PhD. “It will significantly empower the cancer research community to make additional discoveries that will help us treat women with this deadly disease. It also illustrates the power of what’s to come from our investment in TCGA.”
The TCGA researchers also established how sets of genes are expressed in a fashion that can predict patient survival. They identified patterns of gene expression associated with poor survival and others associated with better survival.
To identify opportunities for targeted treatment, the investigators searched for existing drugs that might inhibit genes thought to play a role in ovarian cancer. The search identified 68 genes that could be targeted by existing U.S. Food and Drug Administration-approved or experimental therapeutic compounds.
The researchers also found that 50 percent of tumors might be responsive to drugs that exploit the genetic instability of the tumors and induce the cancer cells to die.
Mutations in BRCA1 and BRCA2 genes, which are associated with some forms of breast cancer, also increase the risk of ovarian cancer. In this study, approximately 21 percent of the tumors showed mutations in these genes. Analysis of these tumors confirmed observations that patients with mutated BRCA1 and BRCA2 genes have better survival odds than patients without mutations in these genes.
TCGA, launched in 2006, is a comprehensive effort to accelerate the understanding of the molecular basis of cancer through large-scale genome sequencing and other genetic technologies. The project is funded by the National Cancer Institute (NCI) and the National Human Genome Research Institute (NHGRI). Data is available to the research community through the TCGA database.