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 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.
Mancuso
T
T
Division of Anatomic Pathology and Cytology, Istituto Nazionale per lo Studio e la Cura dei Tumori, Milano, Italy.
Mezzelani
A
A
Riva
C
C
Fabbri
A
A
Dal Bo
L
L
Sampietro
G
G
Perego
P
P
Casali
P
P
Zunino
F
F
Sozzi
G
G
Pierotti
M A
MA
Pilotti
S
S
D000293:Adolescent; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis / Q000235:genetics*; D002887:Chromosomes, Human, Pair 18; D005260:Female; D015321:Gene Rearrangement; D019254:Genes, bcl-2; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000235:genetics / Q000601:surgery; D015514:Oncogene Proteins, Fusion / Q000032:analysis / Q000235:genetics*; D010766:Phosphorylation; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012509:Sarcoma / Q000235:genetics* / Q000473:pathology / Q000601:surgery; D013583:Synovial Membrane; D014158:Transcription, Genetic; D014960:X Chromosome
D014408:Biomarkers, Tumor; D015514:Oncogene Proteins, Fusion; D019253:Proto-Oncogene Proteins c-bcl-2; C116512:SYT-SSX fusion protein