sphingosine-1-phosphate and Chondrosarcoma

The malignant bone tumors that are categorized as chondrosarcomas display a high potential for metastasis in late-stage disease. Higher-grade chondrosarcomas contain higher levels of expression of platelet-derived growth factor (PDGF) and its receptor. The phosphorylation of sphingosine by sphingosine kinase enzymes SphK1 and SphK2 generates sphingosine-1-phosphate (S1P), which inhibits human chondrosarcoma cell migration, while SphK1 overexpression suppresses lung metastasis of chondrosarcoma. We sought to determine whether S1P mediates levels of PDGF-A expression and angiogenesis in chondrosarcoma. Surprisingly, our investigations found that treatment of chondrosarcoma cells with S1P and transfecting them with SphK1 cDNA increased PDGF-A expression and induced angiogenesis of endothelial progenitor cells (EPCs). Ras, Raf, MEK, ERK and AP-1 inhibitors and their small interfering RNAs (siRNAs) inhibited S1P-induced PDGF-A expression and EPC angiogenesis. Our results indicate that S1P promotes the expression of PDGF-A in chondrosarcoma via the Ras/Raf/MEK/ERK/AP-1 signaling cascade and stimulates EPC angiogenesis.

Topics: Cell Line, Tumor; Chondrosarcoma; Extracellular Signal-Regulated MAP Kinases; Gene Expression Regulation, Neoplastic; Humans; Lysophospholipids; MAP Kinase Kinase 1; Neovascularization, Pathologic; Platelet-Derived Growth Factor; raf Kinases; ras Proteins; Sphingosine; Transcription Factor AP-1

Chondrosarcoma is the second most common primary malignancy form of bone cancer, exhibiting resistance to chemotherapy and radiation therapy as well as developing high metastasis ability in late-stage tumors. Thus, understanding the metastatic processes of chondrosarcoma is considered a strategy for the treatment of this disease. Sphingosine 1-phosphate (S1P), a bioactive sphingolipid, is produced intracellularly by sphingosine kinase (SphK) and is regarded as a second signaling molecule that regulates inflammation, proliferation, angiogenesis, and metastasis. However, the effect of S1P on chondrosarcoma remains uncertain. As demonstrated by the transwell, immunoblotting, and real-time PCR analyses, we found that S1P inhibited cell migration and MMP-2 expression through the upregulation of the tissue inhibitor of metalloproteinase-3 (TIMP-3) expression in human chondrosarcoma cells. Additionally, we also showed that microRNA (miRNA)-101, which targets the 3' untranslated region (3'UTR) of TIMP-3, decreased significantly following S1P treatment. After transfection with miR-101 mimics, the S1P-regulated cell migration and TIMP-3 expression were both reversed. Furthermore, we also showed that the S1P-inhibited cell migration is mediated through the c-Src/MEK/ERK signaling axis. Meanwhile, the in vivo study indicated that overexpression of SphK1 decreases chondrosarcoma metastasis to the lungs. Our results illustrate the clinical significance between SphK1, TIMP-3, and miR-101 in human chondrosarcoma patients. Taken together, our results suggest that S1P and miR-101 may prove to be potential therapeutic targets for future chondrosarcoma treatment.

Topics: Animals; Bone Neoplasms; Cell Line, Tumor; Chondrosarcoma; Down-Regulation; Gene Expression Regulation, Neoplastic; Humans; Lysophospholipids; MAP Kinase Signaling System; Matrix Metalloproteinase 2; Mice, SCID; MicroRNAs; Neoplasm Metastasis; Sphingosine; Tissue Inhibitor of Metalloproteinase-3; Up-Regulation