HMGB1-mediated autophagy decreases sensitivity to oxymatrine in SW982 human synovial sarcoma cells.

Oxymatrine (OMT) is a type of alkaloid extracted from a traditional Chinese medicinal herb, Sophora flavescens. Although the antitumor activities of OMT have been observed in various cancers, there are no reports regarding the effects of OMT on human synovial sarcoma. In the present study, we analyzed the antitumor activities of OMT in SW982 human synovial sarcoma cells and determine whether high mobility group box protein 1 (HMGB1)-mediated autophagy was associated with its therapeutic effects. We found that OMT exhibited antitumor activity in SW982 cells and facilitated increases in autophagy. Inhibition of autophagy by 3-MA or ATG7 siRNA increased the level of apoptosis, which indicated that OMT-induced autophagy protected cells from the cytotoxicity of OMT. Administration of OMT to SW982 cells increased the expression of HMGB1. When HMGB1 was inhibited via HMGB1-siRNA, OMT-induced autophagy was decreased, and apoptosis was increased. Furthermore, we found that HMGB1-siRNA significantly increased the expression of p-Akt and p-mTOR. OMT-induced autophagy may be mediated by the Akt/mTOR pathway, and HMGB1 plays a vital role in the regulation of autophagy. Therefore, we believe that combining OMT with an inhibitor of autophagy or HMGB1 may make OMT more effective in the treatment of human synovial sarcoma.

Emerging therapeutic targets for synovial sarcoma.

Synovial sarcoma is part of soft tissue sarcomas, an uncommon group of malignant tumors of mesenchymal origin. Unfortunately, a very limited number of useful drugs are active for most advanced synovial sarcoma. These tumors showed VEGF expression, and elevated serum VEGF levels correlate with higher histologic tumor grade. Inhibition of VEGFR was associated with tumor activity in preclinical models of synovial sarcoma and drugs such as sorafenib, pazopanib and bevacizumab have been employed in synovial sarcoma in monotherapy and in combination with chemotherapy. Other targets such as EGFR, HER2, IGFR-1R and mTOR have been exploited, but their inhibition by drugs such as gefitinib, trastuzumab, figitumumab, and temsirolimus, has not resulted in meaningful activity. Newer approaches include CXCR4 inhibition, immune-based therapies (NY-ESO-1), targeting epigenetic misregulation with HDAC inhibitors and targeting developmental pathways such Notch and Hedgehog. This review will summarize achievements and pitfalls of drugs against emerging therapeutic targets for synovial sarcoma.

PDGF receptor alpha is an alternative mediator of rapamycin-induced Akt activation: implications for combination targeted therapy of synovial sarcoma.

Akt activation by the IGF-1 receptor (IGF-1R) has been posited to be a mechanism of intrinsic resistance to mTORC1 inhibitors (rapalogues) for sarcomas. Here we show that rapamycin-induced phosphorylation of Akt can occur in an IGF-1R-independent manner. Analysis of synovial sarcoma cell lines showed that either IGF-1R or the PDGF receptor alpha (PDGFRA) can mediate intrinsic resistance to rapamycin. Repressing expression of PDGFRA or inhibiting its kinase activity in synovial sarcoma cells blocked rapamycin-induced phosphorylation of Akt and decreased tumor cell viability. Expression profiling of clinical tumor samples revealed that PDGFRA was the most highly expressed kinase gene among several sarcoma disease subtypes, suggesting that PDGFRA may be uniquely significant for synovial sarcomas. Tumor biopsy analyses from a synovial sarcoma patient treated with the mTORC1 inhibitor everolimus and PDGFRA inhibitor imatinib mesylate confirmed that this drug combination can impact both mTORC1 and Akt signals in vivo. Together, our findings define mechanistic variations in the intrinsic resistance of synovial sarcomas to rapamycin and suggest therapeutic strategies to address them.

The proto-oncoprotein SYT interacts with SYT-interacting protein/co-activator activator (SIP/CoAA), a human nuclear receptor co-activator with similarity to EWS and TLS/FUS family of proteins.

The proto-oncoprotein SYT is involved in the unique translocation t(X;18) found in synovial sarcoma SYT-SSX fusions. SYT has a conserved N-terminal domain (SNH domain) that interacts with the human paralog of Drosophila Brahma (hBRM) and Brahma-related gene 1 (BRG1) chromatin remodeling proteins and a C-terminal transactivating sequence rich in glutamine, proline, glycine, and tyrosine (QPGY domain). Here we reported the isolation of the ribonucleoprotein SYT-interacting protein/co-activator activator (SIP/CoAA), which specifically binds the QPGY domain of SYT and also the SYT-SSX2 translocation fusion. SIP/CoAA is a general nuclear co-activator and an RNA splicing modulator that contains two RNA recognition motifs and multiple hexapeptide repeats. We showed that the region consisting of the hexapeptide motif (YQ domain) is similar to the hexapeptide repeat domain found in EWS and in TLS/FUS family proteins. The YQ domain also resembles the QPGY region of SYT itself and like all these other domains acts as a transcriptional activator in reporter assays. Most interestingly, the last 84 amino acids adjacent to YQ down-modulate by 25-fold the YQ transactivation of the reporter gene, and both domains are important for SIP/CoAA binding to SYT. In addition, SYT acts together with SIP/CoAA in stimulating estrogen and glucocorticoid receptor-dependent transcriptional activation. Activation is hormone-dependent and requires functional hBRM and/or BRG1. The stimulation is strongly reduced if the N-terminal region of hBRM/BRG1 (amino acids 1-211) is deleted. This region encompasses the SNF11 binding domain (amino acids 156-211), which interacts specifically with SYT in vivo and in vitro.

[Concentration of 99mTc-tin-phosphate complexes in soft tissues]. / Zur Frage der Weichteilkonzentration von 99mTc-Zinn-Phosphat-Komplexen

The concentration of 99mTc-pyrophosphate was determined in the lower extremities of rabbits (normal, abacterial and bacterial affected soft tissues), in osteoarthritis of the hip joint (capsule and muscle) as well as in knee joint effusions. Compared with the 85Sr-concentration, reflecting the calcification capacity, concentrations of 99mTc-pyrophosphate in soft tissues were found to be lower 2 hours p.i., but were up to elevenfold higher 24 hours p.i. These findings should be due to a fixation of 99mTc-pyrophosphate in collagen containing tissues as in the soft tissue tumors (myosarcoma, synvialioma, breast cancer) presented. A mechanism of delayed equilibration could explain augmented uptake in lymph-edema, ascites and effusions in florid osteoarthritis of the knee joint. The possible dependence of 99mTc-pyrophosphate concentration in bone and soft tissue on collagenous contents is discussed.