Mutations indicate predisposition to blood cancers
Credit: Graham Colm
Two teams of researchers have identified somatic mutations that increase the likelihood a person will develop a hematologic malignancy.
This “pre-malignant” stage was detected simply by sequencing DNA from blood samples.
The researchers found that subjects carrying certain mutations had more than 10 times the risk of developing a hematologic malignancy than individuals without the mutations. And the risk increased with age.
Steven McCarroll, PhD, of Harvard Medical School in Boston, Massachusetts, and Benjamin Ebert, MD, PhD, also of Harvard Medical School, reported these findings in NEJM.
Both research teams looked at somatic mutations in DNA samples collected from the blood of subjects who had not been diagnosed with cancer or blood disorders.
Taking two very different approaches, the teams found that a surprising percentage of individuals had acquired a subset of the somatic mutations present in hematologic malignancies. And subjects with the mutations were more likely to develop these cancers.
This pre-malignant state was rare in individuals under the age of 40. But it appeared with increasing frequency with each decade of life, ultimately appearing in more than 10% of individuals over the age of 70.
The researchers believe these early mutations lie in wait for follow-on, cooperating mutations that, when they occur in the same cells as the earlier mutations, drive the cells toward cancer. The majority of mutations occurred in just 3 genes: DNMT3A, TET2, and ASXL1.
Dr Ebert’s group
Dr Ebert and his colleagues had hypothesized that, since hematologic malignancies increase with age, it might be possible to detect early somatic mutations that could be initiating the disease process, and these mutations might increase with age.
The researchers looked specifically at 160 genes known to be recurrently mutated in hematologic malignancies, using genetic data derived from approximately 17,000 blood samples originally obtained for studies on the genetics of type 2 diabetes.
The team found a roughly 11-fold increase in the risk of hematologic malignancy among subjects with the subset of somatic mutations linked to blood cancers. And there was a clear association between age and the frequency of these mutations.
Men were slightly more likely to have the mutations than women, and Hispanics were slightly less likely to have the mutations than other racial/ethnic groups.
The researchers also found an association between the presence of this pre-malignant state and the risk of overall mortality independent of malignancy. Individuals with the mutations had a higher risk of type 2 diabetes, coronary heart disease, and ischemic stroke as well.
However, additional research will be needed to determine the nature of these associations.
Dr McCarroll’s group
Dr McCarroll and his colleagues discovered the same phenomenon while trying to determine whether somatic mutations contribute to the risk of developing schizophrenia.
The team studied roughly 12,000 DNA samples from patients with schizophrenia and bipolar disorder, as well as healthy controls, searching across the whole genome at all of the protein-coding genes for patterns in somatic mutations.
The somatic mutations were concentrated in a handful of genes that turned out to be cancer genes.
So the researchers used electronic medical records to follow the patients’ medical histories, finding that subjects with these acquired mutations had a nearly 13-fold higher risk of developing a hematologic malignancy than subjects without the mutations.
The team conducted follow-up analyses on tumor samples from 2 patients who had progressed from this pre-malignant state to cancer. In both cases, the cancer developed from the same cells that had harbored the initiating mutations years earlier.
