Targeting the conversion of ceramide to sphingosine 1-phosphate as a novel strategy for cancer therapy

Mechanism of glycosaminoglycan-mediated bone and joint disease: implications for the mucopolysaccharidoses and other connective tissue diseases

We have previously shown that glycosaminoglycan (GAG) storage in animal models of the mucopolysaccharidoses (MPS) leads to inflammation and apoptosis within cartilage. We have now extended these findings to synovial tissue and further explored the mechanism underlying GAG-mediated disease. Analysis of MPS rats, cats, and/or dogs revealed that MPS synovial fibroblasts and fluid displayed elevated expression of numerous inflammatory molecules, including several proteins important for lipopolysaccharide signaling (eg, Toll-like receptor 4 and lipoprotein-binding protein). The expression of tumor necrosis factor, in particular, was elevated up to 50-fold, leading to up-regulation of the osteoclast survival factor, receptor activator of nuclear factor-kappaB ligand, and the appearance of multinucleated osteoclast-like cells in the MPS bone marrow. Treatment of normal synovial fibroblasts with GAGs also led to production of the prosurvival lipid sphingosine-1-phosphate, resulting in enhanced cell proliferation, consistent with the hyperplastic synovial tissue observed in MPS patients. In contrast, GAG treatment of normal chondrocytes led to production of the proapoptotic lipid ceramide, confirming the enhanced cell death we had previously observed in MPS cartilage. These findings have important implications for the pathogenesis and treatment of MPS and have further defined the mechanism of GAG-stimulated disease.

Microarray analysis of altered sphingolipid metabolism reveals prognostic significance of sphingosine kinase 1 in breast cancer

Beside their structural role for the cell membrane the family of sphingolipids act as effector molecules in signal transduction with links to various aspects of cancer initiation, progression and treatment response. The "sphingolipid rheostat" balances between apoptosis inducing ceramid and growth promoting sphingosine-1-phosphate. We analyzed gene expression of 43 proteins from this pathway in different subtypes of breast cancer using microarray data of 1,269 tumor samples (test set n=171; validation sets n=1098) and observed significant differences for several genes. Sphingosine kinase 1 (SPHK1), ceramide galactosyltransferase (UGT8), and Ganglioside GD3-Synthase (ST8SIA1) displayed higher expression among ER negative tumors. In contrast, glucosylceramidsynthase (GCS), dihydroceramidsynthases (LASS4, LASS 6) and acid ceramidase (ASAH1) were higher expressed in ER positive samples. Survival analysis revealed a worse outcome of patients with high SPHK1 expression. To avoid a confounding effect of the ER status we also restricted the analysis to 750 patients with ER positive tumors. Again a worse outcome was observed for tumors displaying high SPHK1 expression. While 75.8+/-1.9% of the patients with tumors low in SPHK1 expression were free of metastasis at 5 years, this was the case for only 64.9+/-3.6% of patients with tumors displaying high SPHK1 expression (P=0.008). Immunohistochemistry identified the carcinoma cells as the major source of SPHK1 expression in the tumor. The correlation of SPHK1 with a poor prognosis as well as its high expression among ER negative tumors are in line with the antiapoptotic and proliferative properties of its product sphingosine-1-phosphate. Targeting of the sphingolipid rheostat may thus open new treatment options.