Detection of myxoid liposarcoma-associated FUS-DDIT3 rearrangement variants including a newly identified breakpoint using an optimized RT-PCR assay.
Myxoid/round cell liposarcoma is characterized by the recurrent translocations t(12;16)(q13;p11) and, less commonly, t(12;22)(q13;q12), which fuse FUS or EWSR1, respectively, to DDIT3 on chromosome 12. Although a number of different variant breakpoints have been described, greater than 90% of all cases have one of the three different FUS-DDIT3 fusions, which may have clinical significance. To identify the individual breakpoints, a sequence-specific assay such as reverse transcription-PCR (RT-PCR) is needed. In this study, we optimized primer design to develop an RT-PCR assay for the detection of the most common translocations in formalin-fixed paraffin-embedded tissue specimens. We compared our assay with primers previously published for testing formalin-fixed paraffin-embedded specimens and achieved the most consistent results with our primers. We obtained RNA from 32 MLS cases, of which 27 carried one of the three common FUS-DDIT3 chimeric transcript types. Four of the negative cases were from very small biopsies with very low RNA concentration. One case was consistently negative by RT-PCR, but showed a FUS rearrangement by fluorescent in situ hybridization, suggesting that it may harbor one of the rarer FUS-DDIT3 chimeric types. In addition to the common fusions, our assay also identified a novel FUS-DDIT3 fusion between exon 9 of FUS and exon 3 of DDIT3 in one of the cases.
Powers
Martin P
MP
Division of Molecular Pathology, Department of Pathology, Baylor College of Medicine and Texas Children's Hospital, Houston, TX 77030, USA.
Wang
Wei-Lien
WL
Hernandez
Vivian S
VS
Patel
Kayuri S
KS
Lev
Dina C
DC
Lazar
Alexander J
AJ
López-Terrada
Dolores H
DH
D056905:Chromosome Breakpoints; D017931:DNA Primers; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D018208:Liposarcoma, Myxoid / Q000235:genetics*; D015514:Oncogene Proteins, Fusion / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods*; D014178:Translocation, Genetic
D017931:DNA Primers; C532377:FUS-DDIT3 fusion protein, human; D015514:Oncogene Proteins, Fusion