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

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 SS X1 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 c hanges, bcl-2 expression, as assessed by immunohistochemistry, has been rep orted 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-neg ative cases only. Our results showed a significant correlation between the SYT-SSX2 fusion and the monophasic SS histologic subtype. SYT-SSX1 fusion t ranscripts were present in both monophasic and biphasic tumors. The SYT-SSX 4 fusion type was detected in a single monophasic SS. In the same series of SS cases, we also confirmed and extended the previously reported constitut ive expression of bcl-2 protein, by using both immunohistochemical and west ern blot analysis. Moreover, we demonstrated that the BCL-2 gene is not rea rranged or amplified at genomic level, indicating that the high levels of b cl-2 expression observed in SS might result from transcriptional activation of the gene and/or protein stabilization. Finally, we show that bcl-2 is n ot phosphorylated in tumors from patients who had been preoperatively treat ed 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 unab le to activate an apoptosis pathway involving bcl-2 phosphorylation/inactiv ation and may provide a possible explanation for the limited effectiveness of conventional pharmacological treatments of this tumor type.