Establishment of multiplex RT-PCR to detect fusion genes for the diagnosis of Ewing sarcoma

Background Detection of the tumor-specific EWSR1/FUS-ETS fusion gene is essential to diagnose Ewing sarcoma. Reverse transcription-polymerase chain reaction (RT-PCR) and fluorescence in situ hybridization are commonly used to detect the fusion gene, and assays using next-generation sequencing have recently been reported. However, at least 28 fusion transcript variants have been reported, making rapid and accurate detection difficult. Methods We constructed two sets of multiplex PCR assays and evaluated their utility using cell lines and clinical samples. Results EWSR1/FUS-ETS was detected in five of six tumors by the first set, and in all six tumors by the second set. The fusion gene detected only by the latter was EWSR1-ERG, which completely lacked exon 7 of EWSR1. The fusion had a short N-terminal region of EWSR1 and showed pathologically atypical features. Conclusions We developed multiplex RT-PCR assays to detect EWSR1-ETS and FUS-ETS simultaneously. These assays will aid the rapid and accurate diagnosis of Ewing sarcoma. In addition, variants of EWSR1/FUS-ETS with a short N-terminal region that may have been previously missed can be easily detected.

Automated summary

Two sets of multiplex PCR assays were developed to detect EWSR1-ETS and FUS-ETS fusion genes simultaneously, aiding in the rapid and accurate diagnosis of Ewing sarcoma. The second set detected the EWSR1-ERG fusion gene, which displayed pathologically atypical features.