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

Lab Invest. 2000 Jun;80(6):805-13. doi: 10.1038/labinvest.3780085.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

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

Substances

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