Gene fusion detection in formalin-fixed paraffin-embedded benign fibrous histiocytomas using fluorescence in situ hybridization and RNA sequencing

Lab Invest. 2015 Sep;95(9):1071-6. doi: 10.1038/labinvest.2015.83. Epub 2015 Jun 29.

Abstract

Benign fibrous histiocytomas (FH) can be subdivided into several morphological and clinical subgroups. Recently, gene fusions involving either one of two protein kinase C genes (PRKCB and PRKCD) or the ALK gene were described in FH. We here wanted to evaluate the frequency of PRKCB and PRKCD gene fusions in FH. Using interphase fluorescence in situ hybridization on sections from formalin-fixed paraffin-embedded (FFPE) tumors, 36 cases could be analyzed. PRKCB or PRKCD rearrangements were seen in five tumors: 1/7 regular, 0/3 aneurysmal, 0/6 cellular, 2/7 epithelioid, 0/1 atypical, 2/10 deep, and 0/2 metastatic lesions. We also evaluated the status of the ALK gene in selected cases, finding rearrangements in 3/7 epithelioid and 0/1 atypical lesions. To assess the gene fusion status of FH further, deep sequencing of RNA (RNA-Seq) was performed on FFPE tissue from eight cases with unknown gene fusion status, as well as on two FH and six soft tissue sarcomas with known gene fusions; of the latter eight positive controls, the expected fusion transcript was found in all but one, while 2/8 FH with unknown genetic status showed fusion transcripts, including a novel KIRREL/PRKCA chimera. Thus, also a third member of the PRKC family is involved in FH tumorigenesis. We conclude that gene fusions involving PRKC genes occur in several morphological (regular, cellular, aneurysmal, epithelioid) and clinical (cutaneous, deep) subsets of FH, but they seem to account for only a minority of the cases. In epithelioid lesions, however, rearrangements of PRKC or ALK were seen, as mutually exclusive events, in the majority (5/7) of cases. Finally, the study also shows that RNA-Seq is a promising tool for identifying gene fusions in FFPE tissues.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anaplastic Lymphoma Kinase
  • DNA Primers / genetics
  • Formaldehyde
  • Gene Fusion / genetics*
  • Gene Rearrangement / genetics*
  • Histiocytoma, Benign Fibrous / genetics
  • Histiocytoma, Benign Fibrous / pathology*
  • Histological Techniques
  • Humans
  • In Situ Hybridization, Fluorescence / methods
  • Protein Kinase C beta / genetics*
  • Protein Kinase C beta / metabolism
  • Protein Kinase C-delta / genetics*
  • Protein Kinase C-delta / metabolism
  • Receptor Protein-Tyrosine Kinases / genetics*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sarcoma / genetics
  • Sarcoma / pathology*
  • Sequence Analysis, RNA / methods
  • Tissue Fixation

Substances

  • DNA Primers
  • Formaldehyde
  • ALK protein, human
  • Anaplastic Lymphoma Kinase
  • Receptor Protein-Tyrosine Kinases
  • PRKCB protein, human
  • PRKCD protein, human
  • Protein Kinase C beta
  • Protein Kinase C-delta