Scientists discover genomic variant that increases risk of brain tumour

ROCHESTER, MN, USA — A study by Mayo Clinic and University of California, San Francisco study has found that people with a "G" (guanine) instead of an "A" (adenine) at a specific spot in their genetic code have a six-fold higher risk of developing certain types of brain tumours.

The study, published online in the journal Nature Genetics, may help researchers identify people at risk of developing certain subtypes of gliomas, which account for about 20 percent of annual brain cancer diagnoses in the U.S.

Researchers still have to confirm whether the spot is the source of tumors, but if it's not, "it is pretty close," says senior author Robert Jenkins, M.D., Ph.D., a pathologist at the Mayo Clinic Cancer Center. "Based on our findings, we are already starting to think about clinical tests that can tell patients with abnormal brain scans what kind of tumor they have, just by testing their blood."

Researchers studying the genomic basis of gliomas observed a portion of chromosome 8 that contained single nucleotide polymorphisms or "SNPs" associated with brain tumors a few years back. Since then, Dr. Jenkins and Margaret Wrensch, Ph.D., professor of neurological surgery at the University of California, San Francisco, have been using a combination of sophisticated genomic techniques to search for the SNP causing brain tumors to form.

Seven SNPs were found be potentially linked to tumor fomration. The SNP called rs55705857 confers a relative risk approaching that is seen with BRCA1, the breast cancer gene. This region was only found through next generation sequencing, the most laborious method used by the researchers. Dr. Jenkins says that experimental and mathematical shortcuts may miss such rare, highly potent gene variants.

Drs. Jenkins and Wrensch found that the "G" guanine version of this SNP was strongly associated with slower growing gliomas.

"Being able to tell people that the mass in their brain is this type of tumor is actually good news, because it has a much better prognosis than other brain tumors," Dr. Jenkins says. "So what is it that predisposes people to develop less aggressive, but still lethal, gliomas? That makes understanding the function of this variant even more important."

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