WASHINGTON – Scientists for the first time have decoded the entire genome of a cancer patient, identifying a series of genes never before linked to the type of white blood cell cancer that ultimately killed the woman.
The study, published on Wednesday in the journal Nature, represents a new approach to grasp the genetic underpinning of cancer and pave the way for better treatments, researchers at Washington University School of Medicine in St. Louis said.
The patient was a woman in her 50s who died 23 months after she was diagnosed with acute myeloid leukemia, according to Dr. Timothy Ley, who led the study. Only one in five patients who get this disease, also called AML or acute myelogenous leukemia, live more than five years after diagnosis.
Ley and colleagues aimed to find genetic mutations that might initiate the development of AML. They sequenced the genes in a sample of normal skin tissue from the woman as well as the genes in her tumor cells taken from bone marrow.
The technique is called high-throughput sequencing.
By comparing tumor tissue to normal tissue, they pinpointed 10 mutated genes in the cancerous tissue apparently involved in triggering AML. Previous research had linked two of them to AML, but the rest never before had been implicated.
"The other eight were all things that caught us off guard. They're all new. And they are all in genes that we didn't really have on our radar for this particular kind of cancer. In retrospect, they all make sense," Ley said.
Three of them normally act to suppress tumor growth, four are involved in promoting cell growth and the final one may affect how drugs enter a cell, the researchers said.
"This is the only way we would have found these mutations. There's no other path to get this information. I think it really has begun to tell us how little we know about cancer," Ley added in a telephone interview.
The treatment of AML has changed little in the past two decades because most of the genetic events behind the disease had remained unknown, the researchers said.
"This is the first human cancer genome that's been sequenced. In the past, we've always looked at parts of the genome for mutations. But this is the first time that we've been able to look at everything," Ley said.
A deeper genetic understanding of cancer — now possible with speedier, cheaper DNA sequencing technology — can serve as the foundation for developing more effective ways to diagnose and treat cancer, the researchers said.
"There are probably many, many ways to mutate a small number of genes to get the same result, and we're only looking at the tip of the iceberg in terms of identifying the combinations of genetic mutations that can lead to AML," Richard Wilson, one of the researchers, said in a statement.