Researchers from a branch of the National Institute of Health (NIH) have found a set of proteins involved in immunity - supposed to defend the body - that have the bad effect of creating a large number of mutations in DNA. These genetic mutations may be just as powerful as other known causes of cancer in producing tumors in the human body, the researchers say.
The study, published in the journal Nature Genetics, focuses on a group of proteins called APOBEC (short for the tongue-tying chemical name, apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like cytidine deaminases).
In some samples, the researchers note, this protein accounted for 68% of all mutations.
One of the paper's authors, Dr. Dmitry Gordenin, was reported by Medical Xpress as saying that the APOBEC proteins are known to be of benefit, shutting down viruses that attack the body. But he notes that he and his team were surprised to find that they are also a detriment, mutating DNA.
The team from the NIH also worked with colleagues from MIT and Harvard to search for signs of APOBEC mutations in cancers across the entire genome listed in The Cancer Genome Atlas.
Researchers examined 954,247 mutations within 2,680 cancer samples. Almost 70% of mutations resulted from the APOBEC protein in some tumors.
Dr. Steven Roberts, an author of the study, believes that since the immune system - which is influenced by environmental factors - regulates APOBECs, the mutation of them may also be influenced by the world outside the body.
"We hope that determining the environmental link to these mutations will lead to viable cancer prevention strategies," he said.
Gordenin and his team published a study previously in 2012, in which they noted that clustered mutations in cancers can appear as a result of damaged DNA.
Gordenin notes that "The presence of APOBEC clusters in the genome of tumor cells indicates that APOBEC enzymes could also have caused many mutations across the genome."
For future studies, Gordenin and Roberts will focus on why APOBEC mutations appear in some cancer types but not in others.