title: Molecular detection of SS18-SSX fusion gene transcripts by cRNA in situ hybridization in synovial sarcoma using formalin-fixed, paraffin-embedded tumor tissue specimens.
abstract: SS18-SSX fusion genes resulting from a chromosomal translocation t(X;18)(p11.2;q11.2) are a genetic hallmark of synovial sarcoma. Although such cytogenetic or molecular aberrations have mostly been detected by fluorescence in situ hybridization or reverse transcription-polymerase chain reaction, the expression of SS18-SSX has been poorly investigated at a cellular or tissue level. In this study, biotinylated tyramide (BT)-based in situ hybridization (ISH) was performed to detect SS18-SSX transcripts using formalin-fixed, paraffin-embedded tissues from 15 synovial sarcomas. Digoxigenin-labeled cRNA probes flanking the fusion points of SS18-SSX1 and SS18-SSX2 were generated by in vitro transcription, and hybridized signals were detected by a streptavidin-biotin complex method after chemical enhancement with BT. The localizations of signals were compared with the immunohistochemical expressions of epithelial or neuroectodermal markers and those of cell adhesion including cytokeratins (CAM5.2, AE1/AE3, CK7), epithelial membrane antigen, E-cadherin, beta-catenin, c-erbB-2 (HER2/neu), CD56, and claudin-1. The ISH signals of the SS18-SSX transcripts were identified in 13 synovial sarcomas, and their fusion types correlated with those determined by reverse transcription-polymerase chain reaction. In biphasic tumors, the ISH signals tended to localize to epithelial areas, whereas spindle-cell areas or monophasic fibrous tumors showed a less intense or focal expression pattern. Notably, the expression patterns of AE1/AE3, CK7, and c-erbB-2 often colocalized with the ISH signals (7 of 11 cases positive for each marker). Our results suggest that BT-based ISH can be used as a molecular technique for the detection of SS18-SSX using formalin-fixed, paraffin-embedded tissues.
authors.affiliation: Department of Pathology and Oncology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
authors.forename: Shuichi
authors.initials: S
authors.lastname: Kanemitsu
authors.forename: Masanori
authors.initials: M
authors.lastname: Hisaoka
authors.forename: Shohei
authors.initials: S
authors.lastname: Shimajiri
authors.forename: Atsuji
authors.initials: A
authors.lastname: Matsuyama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hashimoto
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis; D005260:Female; D005557:Formaldehyde / Q000737:chemistry; D006801:Humans; D017403:In Situ Hybridization / Q000379:methods; D008297:Male; D008875:Middle Aged; D009363:Neoplasm Proteins / Q000235:genetics*; D050596:Oncogene Fusion; D016612:Paraffin Embedding; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D015347:RNA Probes / Q000737:chemistry; D018075:RNA, Complementary / Q000032:analysis*; D012097:Repressor Proteins / Q000235:genetics*; D013584:Sarcoma, Synovial / Q000737:chemistry / Q000235:genetics* / Q000473:pathology; D014158:Transcription, Genetic
chemical_list: D014408:Biomarkers, Tumor; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D015347:RNA Probes; D018075:RNA, Complementary; D012097:Repressor Proteins; C093961:SS18 protein, human; C093962:synovial sarcoma X breakpoint proteins; D005557:Formaldehyde