A novel FISH assay for SS18-SSX fusion type in synovial sarcoma.
Synovial sarcoma is a morphologically, clinically and genetically distinct entity that accounts for 5-10% of all soft tissue sarcomas. The t(X;18)(p11.2;q11.2) is the cytogenetic hallmark of synovial sarcoma and is present in more than 90% of the cases. It produces three types of fusion gene formed in part by SS18 from chromosome 18 and by SSX1, SSX2 or, rarely, SSX4 from the X chromosome. The SS18-SSX fusions do not seem to occur in other tumor types, and it has been shown that in synovial sarcoma a clear correlation exists between the type of fusion gene and histologic subtype and, more importantly, clinical outcome. Previous analyses regarding the type of fusion genes have been based on PCR amplification of the fusion transcript, requiring access to good-quality RNA. In order to obtain an alternative tool to diagnose and follow this malignancy, we developed a fluorescence in situ hybridization (FISH) assay that could distinguish between the two most common fusion genes, that is, SS18-SSX1 and SS18-SSX2. The specificity of the selected bacterial artificial chromosome clones used in the detection of these fusion genes, as well as the sensitivity of the analysis in metaphase and interphase cells, was examined in a series of 28 synovial sarcoma samples with known fusion gene status. In all samples, the type of fusion was correctly identified by FISH. Thus, the assay described here should be useful for clarifying unresolved chromosome markers and for identifying fusion gene status in samples from which RNA of sufficient quality for PCR could not be extracted.
Surace
Cecilia
C
Department of Clinical Genetics, Lund University Hospital, Lund, Sweden.
Panagopoulos
Ioannis
I
Pålsson
Eva
E
Rocchi
Mariano
M
Mandahl
Nils
N
Mertens
Fredrik
F
D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism; D019677:Artificial Gene Fusion; D022202:Chromosomes, Artificial, Bacterial; D004273:DNA, Neoplasm / Q000032:analysis; D005260:Female; D005819:Genetic Markers; D006801:Humans; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*; D008297:Male; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D015514:Oncogene Proteins, Fusion / Q000235:genetics* / Q000378:metabolism; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D013584:Sarcoma, Synovial / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D012983:Soft Tissue Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D032681:Spectral Karyotyping
D000951:Antigens, Neoplasm; D004273:DNA, Neoplasm; D005819:Genetic Markers; D009363:Neoplasm Proteins; D015514:Oncogene Proteins, Fusion; D011506:Proteins; D011518:Proto-Oncogene Proteins; D012097:Repressor Proteins; C093961:SS18 protein, human; C587877:SS18-SSX1 fusion protein; C093962:synovial sarcoma X breakpoint proteins