The chimeric transcript SYT-SSX is generated as a result of reciprocal translocation t(X;18), which is the primary cytogenetic abnormality found in, and appears to be specific for, synovial sarcoma. We performed a reverse transcriptase-polymerase chain reaction (RT-PCR) for SYT-SSX transcripts in a series of 84 tumors (61 soft tissue tumors and 23 bone tumors), including a variety of histologic types, to assess its usefulness in molecular diagnosis. Ten synovial sarcomas, three tumors initially unclassified, and one malignant peripheral nerve sheath tumor contained the chimeric transcripts. A review of the original slides and additional examination showed that a diagnosis of synovial sarcoma was appropriate for these cases. Additionally, in situ hybridization with an SSX1 probe indicated that the chimeric transcripts exist not only in the cells of special components but also in cells showing a variety of histologic patterns. Therefore, RT-PCR can be considered a useful molecular biological technique that can provide objective evidence for diagnosis of synovial sarcoma. Northern blot analysis with an SSX1 probe also detected chimeric SYT-SSX transcripts in the synovial sarcoma cases. The additional smaller bands, however, were also detected in six peripheral primitive neuroectodermal tumors (pPNETs) and one embryonal rhabdomyosarcoma. In five of these pPNETs, other bands ranging in size from 2.0 to 2.2 kb were also found, and it seems possible that these bands might represent novel karyotypic aberrations and/or splicing variants of SSX.
Macrophage migration inhibitory factor (MIF) is a cytokine that mediates inflammatory processes in a variety of tissues. In this study, we examined the expression of MIF mRNA in the mouse osteoblastic cell line MC3T3-E1, whose proliferation is promoted by various growth factors. In the subconfluent state, transforming growth factor-beta, basic fibroblast growth factor, insulin-like growth factor-II, and fetal calf serum markedly upregulated MIF mRNA expression. The upregulation of MIF mRNA was less extensive when the cells were stimulated by the same growth factors in the overconfluent state. We also investigated the expression of MIF mRNA through a whole cell cycle from G0 phase when the osteoblastic cells were synchronized by serum starvation. The MIF mRNA expression, which gradually increased from the G0 and reached its maximum at the S phase, was nonperiodic. Moreover, human recombinant MIF upregulated the expression of urokinase plasminogen activator inhibitor-1 (PAI-1) precursor mRNA in human osteoblastic Saos-2 cells. Plasminogen activator (PA) is known to play an important role in bone metabolism, for example, in activation of procollagenase or growth factors indirectly via the formation of plasmin, and in mitogenic activity for osteoblastic cells. Our results suggest that MIF modulates the proliferation of osteoblasts and, moreover, bone tissue remodeling through the PA and plasmin system.
Clear cell sarcoma (CCS), a rare tumour of deep soft tissues, often has a t(12; 22) (q13; q12) translocation that induces the formation of a hybrid EWS/ATF-1 gene. To investigate these alterations further, we established a new continuous cell line directly from a CCS taken from a 9-year-old girl. The cultures were characterized with respect to morphological, ultrastructural, immunohistochemical and karyotypical features and were tested by reverse transcription PCR (RT-PCR) for chimaeric EWS/ATF-1 transcripts. The continuous cell line, designated KAO, is tumorigenic in nude mice, and the resultant tumours resemble the primary CCS. The tumour cells and the cultured cells have melanosomes in their cytoplasm and are immunoreactive with the melanoma-specific antibody HMB45, but do not express S-100 protein. The cultured CCS cells have the t(12; 22)(q13; q12) translocation and express the hybrid EWS/ATF-1 gene. No transcripts of the hybrid gene were detected in a malignant cutaneous melanoma tested simultaneously. Although CCS and malignant melanoma are morphologically related, the present results suggest that their geneses differ at the chromosome and molecular levels. They also indicate that chromosome analysis and detection of fusion EWS/ATF-1 transcripts may be useful adjuvant tools for the diagnosis of CCS.
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