Analysis of SYT-SSX fusion transcripts and bcl-2 expression and phosphorylation status in synovial sarcoma.

Abstract

Synovial sarcomas (SS) are characterized by a chromosomal translocation t(X;18)(p11.2;q11.2) which usually fuses the SYT gene from chromosome 18 to SSX1 or SSX2 genes on chromosome X. Also, a variant SYT-SSX4 fusion gene has recently been shown in a single SS case. In addition to these cytogenetic changes, bcl-2 expression, as assessed by immunohistochemistry, has been reported to be an almost general constitutive alteration of SS. In the present work, we analyze a series of 36 SS surgical samples (from 34 patients) by RT-PCR for the presence of the SYT-SSX1 or the SYT-SSX2 fusion transcript. The analysis was extended to SYT-SSX4 on SYT-SSX1-negative and SYT-SSX2-negative cases only. Our results showed a significant correlation between the SYT-SSX2 fusion and the monophasic SS histologic subtype. SYT-SSX1 fusion transcripts were present in both monophasic and biphasic tumors. The SYT-SSX4 fusion type was detected in a single monophasic SS. In the same series of SS cases, we also confirmed and extended the previously reported constitutive expression of bcl-2 protein, by using both immunohistochemical and western blot analysis. Moreover, we demonstrated that the BCL-2 gene is not rearranged or amplified at genomic level, indicating that the high levels of bcl-2 expression observed in SS might result from transcriptional activation of the gene and/or protein stabilization. Finally, we show that bcl-2 is not phosphorylated in tumors from patients who had been preoperatively treated with radio/chemotherapy, in tumors from untreated patients, or in an SS cell line (CME-1) after in vitro treatment with cytotoxic concentrations of DNA-damaging agents or taxanes. These data indicate that SS cells are unable to activate an apoptosis pathway involving bcl-2 phosphorylation/inactivation and may provide a possible explanation for the limited effectiveness of conventional pharmacological treatments of this tumor type.

• Authors: T Mancuso, A Mezzelani, C Riva, A Fabbri, L Dal Bo, G Sampietro, P Perego, P Casali, F Zunino, G Sozzi, M A Pierotti, S Pilotti
• Journal: Laboratory investigation; a journal of technical methods and pathology (Lab Invest) Vol. 80 Issue 6 Pg. 805-13 (Jun 2000) ISSN: 0023-6837 [Print] United States
• PMID: 10879732 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Biomarkers, Tumor
• Oncogene Proteins, Fusion
• Proto-Oncogene Proteins c-bcl-2
• SYT-SSX fusion protein

Topics

• Adolescent
• Adult
• Aged
• Biomarkers, Tumor (analysis, genetics)
• Chromosomes, Human, Pair 18
• Female
• Gene Rearrangement
• Genes, bcl-2
• Humans
• Male
• Middle Aged
• Neoplasm Recurrence, Local (genetics, surgery)
• Oncogene Proteins, Fusion (analysis, genetics)
• Phosphorylation
• Proto-Oncogene Proteins c-bcl-2 (metabolism)
• Reverse Transcriptase Polymerase Chain Reaction
• Sarcoma (genetics, pathology, surgery)
• Synovial Membrane
• Transcription, Genetic
• X Chromosome