n-n-dimethylsphingenine and Breast-Neoplasms

FTY720 (fingolimod), a novel immunosuppressant, was found to become biologically activated by phosphorylation into FTY720-1-phosphate (FTY720-P), which is a high-affinity agonist for sphingosine-1-phosphate (sphingosine-1-P)-receptors. FTY720 has also been reported to have a strong antitumor activity. The association between the phosphorylation of FTY720 and the growth inhibition of FTY720 against cancer cells are still not completely understood. In this study, we investigated the effects of FTY720, sphingosine, and their related compounds on the proliferation of human breast cancer cell lines (MCF-7, MDA-MB-231 and Sk-Br-3) and human colon cancer cell lines (HCT-116 and SW620). Non-phosphorylated FTY720, sphingosine and an FTY720 derivative, ISP-I-55, showed significant growth inhibition against these cells, with IC50 values of 5-20 microM at 48 h post-drug treatment. We confirmed that FTY720 induces the activation of a major mitogen-activated protein kinase, JNK, without the activation of p38 and down-regulation of phospho-ERK in MCF-7 breast cancer cells. In contrast, the phosphorylated derivatives, FTY720-P and sphingosine-1-P, as well as a phosphinane FTY720 derivative, cFTY720-P, did not inhibit the growth of the cells in the concentration range of 5-50 microM, whereas FTY720-P and sphingosine-1-P slightly induced the growth of MCF-7 cells. Combining FTY720 with dimethylsphingosine, a sphingosine kinase inhibitor, augmented the inhibitory effect of FTY720. These results indicate that the antiproliferative activity of FTY720 does not result from its phosphorylation, either endogenous or exogenous.

Topics: Antineoplastic Agents; Blotting, Western; Breast Neoplasms; Cell Line, Tumor; Cell Proliferation; Cell Survival; Colonic Neoplasms; Enzyme Inhibitors; Female; Fingolimod Hydrochloride; Humans; Immunosuppressive Agents; Indicators and Reagents; JNK Mitogen-Activated Protein Kinases; Mitogen-Activated Protein Kinases; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); Propylene Glycols; Spectrophotometry, Infrared; Sphingosine

We have demonstrated previously that IGFBP-5 can confer survival against apoptosis induced by ceramide, C2, or a small synthetic arginine-glycine-aspartic acid (RGD)-containing peptide in a direct manner. The endogenous ceramide-induced pathway is normally counter-balanced by survival signals mediated by sphingosine kinase (SK) and protein kinase C (PKC). In order to investigate whether these pathways are involved in the IGFBP-5 survival effect, we have used inhibitors of SK (N, N-di-methyl sphingosine, DMS) and PKC (chelerythrine chloride, CC). The effect of pre-incubating Hs578T breast cancer cells with IGFBP-5 on cell adhesion or on subsequent cell death induced by C2 or RGD was investigated with and without the presence of DMS or CC. Cell death was determined by trypan blue cell counts and apoptosis confirmed by morphological assessment and flow cytometry. Cell attachment was determined by a cell adhesion assay. The presence of IGFBP-5 significantly inhibited cell death induced by C2 or RGD, compared to the triggers of apoptosis alone (P<0.01 in both cases). In the presence of either IGFBP-5, CC or DMS, there was no significant effect on cell death compared to the control. IGFBP-5 in the presence of either inhibitor resulted in a significant increase in cell death; IGFBP-5 also lost its ability to confer survival on C2 and RGD-induced apoptosis and in contrast significantly increased cell death. In the cell adhesion assay, IGFBP-5 significantly increased cell attachment over basal levels. In the presence of either inhibitor the IGFBP-5 effect on cell adhesion was reversed and cell attachment was reduced to below basal levels. These data suggest that IGFBP-5 promotes the attachment and survival of Hs578T cells by modulating the balance between ceramide and opposing survival signals.

Topics: Alkaloids; Apoptosis; Benzophenanthridines; Breast Neoplasms; Cell Adhesion; Cell Survival; Ceramides; Drug Interactions; Enzyme Inhibitors; Epithelial Cells; Humans; Insulin-Like Growth Factor Binding Protein 5; Oligopeptides; Phenanthridines; Phosphotransferases (Alcohol Group Acceptor); Protein Kinase C; Signal Transduction; Sphingosine; Tumor Cells, Cultured