A novel genetic anomaly was identified in a 44-year-old woman with solitary fibrous tumor who enrolled in a clinical sequencing program that included whole-exome and transcriptome sequencing. This anomaly provides an important clue to improving how this cancer is diagnosed and treated. Solitary fibrous tumor is a rare cancer that is seen only in a few hundred people each year.
The tumor’s genome was sequenced through a new program called MI-ONCOSEQ, which is designed to identify genetic mutations in tumors that might be targeted with new therapies being tested in clinical trials. The sequencing also allows researchers to find new mutations.
In this case, an unusual occurrence of two genes—NAB2 and STAT6—fused together. This is the first time this gene fusion has been identified.
“In most cases, mutations are identified because we see them happening again and again. Here, we had only one case of this. We knew NAB2-STAT6 was important because integrated sequencing ruled out all the known cancer genes. That allowed us to focus on what had been changed,” said lead study author Dan R. Robinson, PhD, research fellow at the University of Michigan Comprehensive Cancer Center.
Once the research team found the aberration, they examined 51 other tumor samples from benign and cancerous solitary fibrous tumors, looking for the NAB2-STAT6 fusion. It showed up in every one of the samples, as described in Nature Genetics (2013; doi:10.1038/ng.2509).
“Genetic sequencing is extremely important with rare tumors,” said study co-author Scott Schuetze, MD, also of the University of Michigan. “Models of rare cancers to study in the laboratory are either not available or very limited. The sequencing helps us to learn more about the disease that we can use to develop better treatments or to help diagnose the cancer in others.”
The NAB2-STAT6 fusion may prove to be a difficult target for therapies, but researchers believe they may be able to attack the growth signaling cycle that leads to this gene fusion.
“Understanding the changes induced in the cell by the NAB2-STAT6 gene fusion will help us to select novel drugs to study in patients with advanced solitary fibrous tumors. Currently this is a disease for which there are no good drug therapies available and patients are in great need of better treatments,” Schuetze said.
No treatments or clinical trials are currently available based on these findings. Additional testing in the laboratory is needed to assess the best way to target NAB2-STAT6. The gene fusion could also potentially be used to help identify solitary fibrous tumors in cases where a diagnosis is challenging.