This article first appeared in the St. Louis Beacon: Scientists at the Genome Institute at Washington University School of Medicine have identified 127 significantly mutated genes that they believe drive the development of cancer. This knowledge has the potential to lay the groundwork for new diagnostic tests and individualized treatment for different types of cancers, says Li Ding, assistant professor of medicine and assistant director at the Genome Institute at Washington University and the paper's senior author.
“By studying more than 3,000 tumors, we can identify genes positive for the development of cancer,” she says. “By combining studies, we can come up with a complete cancer gene set. We can build a common cancer gene panel.”
The findings, published Oct. 16 in Nature, may help physicians better understand the mechanisms by which each patient’s tumor originates and spreads, and inform treatment. The study is part of the Cancer Genome Atlas Pan-Cancer effort, funded by the National Cancer Institute and the National Human Genome Research Institute, both at the National Institutes of Health.
Same mutation, different cancer
Ding and her colleagues studied gene mutations in 12 different types of cancers, including breast, uterine, head and neck, colon and rectum, bladder, kidney, ovary, lung, brain and blood. They found that some mutations occur commonly among many cancers, while others are exclusive to one type of cancer. One example of this is TP53, a well-known mutation on a gene that encodes a protein that suppresses tumor development. TP53 occurred in 42 percent of the tumors sampled, and in different types of cancer, including breast, head and neck, ovarian, acute myeloid leukemia, and kidney cancer.
Because the genome of each individual cancer has on average only two to six mutations, each mutation may contribute significantly to the development of that cancer. That "suggests a small number of driver mutations can initiate a cancer," said Ding. Knowing which mutations a tumor possesses may help physicians to come up with similar ways to treat tumors in these different types of cancers.
Gene mutations and survival outcomes
Researchers also analyzed long term prognosis, and depending on the genome of the tumor, found that specific genetic mutations are correlated with both good and poor outcomes. For example, TP53 was found to be associated with poor prognosis particularly in kidney cancer, head and neck cancer, and acute myeloid leukemia. Conversely, mutations in the Breast Cancer 2 Gene (BRCA2), also a tumor suppressor gene, were found to be correlated with improved outcomes in ovarian cancer, the paper said.
Comparing tumor genome to healthy genome
The researchers found the mutations by sequencing both the patient’s healthy genome and the tumor genome, and then compared the results. Advances in genome sequencing technology over the last few years have made it possible for researchers to analyze DNA on a scale large enough to compare mutations across many different kinds of cancers.
Ding says that she and her group will continue to build on the result they have.
Single diagnostic test for all human cancers
Ding hopes that in the future one single diagnostic test -- containing all cancer genes -- will be developed. “This would provide a more complete picture of what’s going on in a tumor, and that information could be used to make decisions about treatment,” she said.