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Next-generation sequencing detects rare fusion genes in sarcoma tumours

Fox Chase Cancer Center researchers have determined that RNA-based next generation sequencing picks up gene fusions in sarcoma tumours that traditional gene testing may not.

These findings have been published in the journal Medicine (Baltimore).

Sarcoma is a type of cancer in the bones and in connective tissue such as fat and muscle.

“More than 80 percent of sarcoma types have two genes grouped together called fusion genes,” said Shuanzeng Wei, MD, PhD, assistant professor in the Department of Pathology at Fox Chase.

Different sarcomas can have specific fusion genes which can be used as diagnostic markers.

Traditional tests such as fluorescence in situ hybridisation (FISH), DNA-based next-generation sequencing, or polymerase chain reaction analysis may not catch all fusion genes in a tumour.

For example, FISH analysis may require running multiple tests to determine sarcoma type.

“But running one RNA sequencing analysis identifies all fusion genes in a sarcoma tumour, some of which may be unknown new fusion genes,” said Wei. “If we know exactly what type of sarcoma the patient has, we can then design a specific target treatment in a clinical trial instead of general chemotherapy or radiation.”

The researchers obtained six sarcoma specimens from patients at Fox Chase who had previously been diagnosed with sarcoma using immunophenotyping or FISH analysis.

The researchers then performed RNA sequencing and confirmed the gene fusions in five of the samples.

In the sixth sarcoma specimen, from a woman with a cervical spine tumour, the researchers discovered a rare fusion gene, EWSR1-PATZ1.

Physicians at another institution had previously diagnosed the patient with low-grade spindle and small round cell neoplasm/sarcoma.

When Wei and his team performed a chromosome microarray analysis, they found no chromosome abnormality in the tumour.

However, after RNA sequencing, they discovered the rare fusion gene and re-diagnosed the patient with a low-grade glioneural tumour.

“RNA sequencing is not used for clinical purposes yet, but very soon it will be,” said Wei. “Hopefully, it will help accurately diagnose sarcoma and better manage the patients at our institution.”

Source: Fox Chase Cancer Center

Credit: ecancer.org