Clinical Relevance of the SYT-SSX Fusion Gene in Synovial Sarcoma

Abstract

Recent molecular analyses have reported that the specific translocation t(X;18) (p11.2;q11.2) in synovial sarcoma induces the fusion of the SYT gene on chromosome 18 to either of two duplicated genes on chromosome X, SSX1 or SSX2. As a result, two types of fusion genes SYT-SSX1 and SYT-SSX2, whose products play major roles in tumorigenesis, are formed. However, the precise function of the fusion genes is still unclear. To determine clinical relevance of the SYT-SSX fusion genes, we analyzed the fusion transcripts in 13 synovial sarcomas by reverse transcription-polymerase chain reaction (RT-PCR) and also determined the subtype by restriction enzyme assay. These molecular results were compared with certain clinical features of the tumors. The SYT-SSX fusion transcript was detected in the majority of the cases (11 / 13) with synovial sarcoma, suggesting that it is a useful diagnostic marker. The subtype analysis showed that only the recurrent tumors expressed SYT-SSX2. This may indicate that there are some biological differences between the two subtypes, such as transforming activity. On this basis, SYT-SSX2 may correlate with the progressive character of this tumor and could be a predictor of prognosis.