sirolimus and Sarcoma--Synovial

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.

Topics: Antibodies, Monoclonal; Antineoplastic Agents; Bevacizumab; Everolimus; Humans; Indazoles; Indoles; Molecular Targeted Therapy; Niacinamide; Phenylurea Compounds; Pyrimidines; Pyrroles; Receptors, Vascular Endothelial Growth Factor; Sarcoma; Sarcoma, Synovial; Sirolimus; Sorafenib; Sulfonamides; Sunitinib; TOR Serine-Threonine Kinases

We examined efficacy of the mTOR inhibitor RAD001 to seek novel therapies for synovial sarcoma (SS). Although RAD001 had significant anti-tumor effects, its sensitivity differed among cell lines. Phospho-receptor tyrosine kinase (RTK) array analyses revealed c-MET phosphorylation in highly mTOR inhibitor-sensitive cells and PDGFRα (which induces intrinsic resistance to mTOR inhibitor) activation in less sensitive cells. Combined treatment with RAD001 and the PDGFR inhibitor pazopanib showed anti-tumor effects in xenograft models with less sensitive cells. Thus, evaluating activated RTKs in clinical samples may predict sensitivity to mTOR inhibitors, raising the possibility of a tailored therapy for SS.

Topics: Animals; Antineoplastic Agents; Cell Division; Cell Line, Tumor; Everolimus; Female; Humans; Mice; Mice, Inbred BALB C; Phosphorylation; Proto-Oncogene Proteins c-akt; Receptor Protein-Tyrosine Kinases; Receptor, Platelet-Derived Growth Factor alpha; Sarcoma, Synovial; Sirolimus; TOR Serine-Threonine Kinases

Curative treatments for patients with metastatic synovial sarcoma (SS) do not exist, and such patients have a poor prognosis. We explored combinations of molecularly-targeted and cytotoxic agents to identify synergistic treatment combinations in SS cells.. Two SS cell lines (HS-SY-II and SYO-I) were treated with single agents or combinations of molecularly targeted therapies (HDAC inhibitor, vorinostat; mTOR inhibitor, ridaforolimus) and cytotoxic agents. After 72 hours, cell viability was measured using the MTS cell proliferation assay. Combination Indices (CI) were calculated to determine whether each combination was synergistic, additive, or antagonistic. Western Blot analysis assessed alterations in total and phospho-AKT protein levels in response to drug treatment.. We determined the single-agent IC50 for ridaforolimus, vorinostat, doxorubicin, and melphalan in HS-SY-II and SYO-I. Synergism was apparent in cells co-treated with ridaforolimus and vorinostat: CI was 0.28 and 0.63 in HS-SY-II and SYO-I, respectively. Ridaforolimus/doxorubicin and ridaforolimus/melphalan exhibited synergism in both cell lines. An additive effect was observed with combination of vorinostat/doxorubicin in both cell lines. Vorinostat/melphalan was synergistic in HS-SY-II and additive in SYO-I. Western blot analysis demonstrated that ridaforolimus increased pAKT-ser473 levels; this effect was abrogated by vorinostat co-treatment.. The combination of ridaforolimus and vorinostat demonstrates in vitro synergism in SS. Addition of vorinostat abrogated ridaforolimus-induced AKT activation. Since AKT activation is a possible mechanism of resistance to mTOR inhibitors, adding vorinostat (or another HDAC inhibitor) may be a route to circumvent AKT-mediated resistance to mTOR inhibitors.

Topics: Antineoplastic Combined Chemotherapy Protocols; Cell Line, Tumor; Cell Survival; Dose-Response Relationship, Drug; Doxorubicin; Drug Synergism; Enzyme Activation; Histone Deacetylase Inhibitors; Humans; Hydroxamic Acids; Inhibitory Concentration 50; Melphalan; Molecular Targeted Therapy; Phosphorylation; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Sarcoma, Synovial; Sirolimus; TOR Serine-Threonine Kinases; Vorinostat

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.

Topics: Animals; Antibodies, Monoclonal; Antibodies, Monoclonal, Humanized; Antineoplastic Agents; Benzamides; Cell Line, Tumor; Enzyme Activation; Gene Expression Regulation, Neoplastic; Humans; Imatinib Mesylate; Mechanistic Target of Rapamycin Complex 1; Mice; Molecular Targeted Therapy; Multiprotein Complexes; Oncogene Proteins, Fusion; Phosphatidylinositol 3-Kinases; Phosphorylation; Piperazines; Proteins; Proto-Oncogene Proteins c-akt; Pyrimidines; Receptor, Platelet-Derived Growth Factor alpha; Sarcoma, Synovial; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases; Transcription, Genetic