cyclin-d1 and sphingosine-kinase

Epithelial ovarian cancer is the most common and lethal gynecological cancer in USA and around the world, causing major mortality annually. In the current study, we investigated the potential anti-ovarian cancer activity of WYE-132, a mammalian target of rapamycin (mTOR) complex 1/2 (mTORC1/2) dual inhibitor. Our results showed that WYE-132 potently inhibited proliferation of primary and established human ovarian cancer cells. Meanwhile, WYE-132 induced caspase-dependent apoptosis in ovarian cancer cells. At the molecular level, WYE-132 blocked mTORC1/2 activation and inhibited expression of mTOR-regulated genes (cyclin D1 and hypoxia-inducible factor 1α). Interestingly, introducing a constitutively active AKT (caAKT), which restored mTORC1/2 activation in WYE-132-treated ovarian cancer cells, only mitigated (but not abolished) WYE-132-mediated growth inhibition and apoptosis. Further studies showed that WYE-132 inhibited sphingosine kinase-1 (SphK1) activity, leading to pro-apoptotic ceramide production in ovarian cancer cells. Meanwhile, WYE-132-induced cytotoxicity against ovarian cancer cells was inhibited by sphingosine-1-phosphate (S1P) but was aggravated by SphK1 inhibitor SKI-II or C6 ceramide. In vivo, WYE-132 inhibited ovarian cancer cell growth, and its activity was further enhanced when co-administrated with paclitaxel (Taxol). These results demonstrate that WYE-132 inhibits ovarian cancer cell proliferation through mTOR-dependent and mTOR-independent mechanisms and indicate a potential value of WYE-132 in ovarian cancer treatment.

Topics: Animals; Apoptosis; Caspase 3; Cell Line, Tumor; Cell Proliferation; Cyclin D1; Enzyme Inhibitors; Female; Humans; Hypoxia-Inducible Factor 1, alpha Subunit; Mechanistic Target of Rapamycin Complex 1; Mechanistic Target of Rapamycin Complex 2; Mice; Mice, Nude; Middle Aged; Multiprotein Complexes; Neoplasm Transplantation; Ovarian Neoplasms; Paclitaxel; Phenylurea Compounds; Phosphotransferases (Alcohol Group Acceptor); Pyrazoles; TOR Serine-Threonine Kinases

Lipid metabolism is crucially involved with the promotion of malignant progression and metastasis in various cancers. Growing evidence suggests that many types of cancers express high levels of sphingosine kinase 1 (Sphk1), which is known to mediate cell proliferation We hypothesized that Sphk1/sphingosine-1-phosphate (S1P) signaling contributes to tumor progression. In MCF10A and MCF10A-Sphk1 breast epithelial cells, we used TNF-α to activate the Sphk1/S1P pathway and the measured expression levels of NF-κBp65 and cyclin D1 mRNA and protein in the presence and absence of an NF-κB-p65 inhibitor. Chromatin immunoprecipitation assays were performed to determine whether NF-κB-p65 binds to the cyclin D1 promoter. We found that overexpression of Sphk1 induced NF-κB-p65 activation, increased expression of cyclin D1, shortened the cell division cycle, and thus promoted proliferation of breast epithelial cells. These findings provide insight into the mechanism by which an Sphk1/NF-κB-p65/cyclin D1 signaling pathway mediates cell proliferation.

Topics: Binding Sites; Cell Cycle; Cell Line; Cell Proliferation; Cyclin D1; Epithelial Cells; Female; Humans; Lysophospholipids; Mammary Glands, Human; Phosphotransferases (Alcohol Group Acceptor); Promoter Regions, Genetic; Signal Transduction; Sphingosine; Time Factors; Transcription Factor RelA; Transcription, Genetic

Two isoforms of sphingosine kinase, SK1 and SK2, catalyze the formation of the bioactive lipid sphingosine 1-phosphate (S1P) in mammalian cells. We have previously shown that treatment of androgen-sensitive LNCaP prostate cancer cells with a non-selective SK isoform inhibitor, 2-(p-hydroxyanilino)-4-(p-chlorophenyl)thiazole (SKi), induces the proteasomal degradation of SK1. This is concomitant with a significant increase in C22:0-ceramide and sphingosine levels and a reduction in S1P levels, resulting in the apoptosis of LNCaP cells. In contrast, we show here that a SK2-selective inhibitor, (R)-FTY720 methyl ether (ROME), increases sphingosine and decreases S1P levels but has no effect on ceramide levels and does not induce apoptosis in LNCaP cells. We also show that several glycolytic metabolites and (R)-S-lactoylglutathione are increased upon treatment of LNCaP cells with SKi, which induces the proteasomal degradation of c-Myc. These changes reflect an indirect antagonism of the Warburg effect. LNCaP cells also respond to SKi by diverting glucose 6-phosphate into the pentose phosphate pathway to provide NADPH, which serves as an antioxidant to counter an oxidative stress response. SKi also promotes the formation of a novel pro-apoptotic molecule called diadenosine 5',5'''-P(1),P(3)-triphosphate (Ap3A), which binds to the tumor suppressor fragile histidine triad protein (FHIT). In contrast, the SK2-selective inhibitor, ROME, induces a reduction in some glycolytic metabolites and does not affect oxidative stress. We conclude that SK1 functions to increase the stability of c-Myc and suppresses Ap3A formation, which might maintain the Warburg effect and cell survival, while SK2 exhibits a non-overlapping function.

Topics: Cell Line, Tumor; Ceramides; Cyclin D1; Dinucleoside Phosphates; Enzyme Inhibitors; Glycolysis; Humans; Lysophospholipids; Male; Metabolome; Microtubule-Associated Proteins; Oxidative Stress; Phosphotransferases (Alcohol Group Acceptor); Poly(ADP-ribose) Polymerases; Prostatic Neoplasms; Proto-Oncogene Proteins c-myc; Sphingosine

Resistance to therapies develops rapidly for melanoma leading to more aggressive disease. Therefore, agents are needed that specifically inhibit proteins or pathways controlling the development of this disease, which can be combined, dependent on genes deregulated in a particular patient's tumors. This study shows that elevated sphingosine-1-phosphate (S-1-P) levels resulting from increased activity of sphingosine kinase-1 (SPHK1) occur in advanced melanomas. Targeting SPHK1 using siRNA decreased anchorage-dependent and -independent growth as well as sensitized melanoma cells to apoptosis-inducing agents. Pharmacological SPHK1 inhibitors SKI-I but not SKI-II decreased S-1-P content, elevated ceramide levels, caused a G2-M block and induced apoptotic cell death in melanomas. Targeting SPHK1 using siRNA or the pharmacological agent called SKI-I decreased the levels of pAKT. Furthermore, SKI-I inhibited the expression of CYCLIN D1 protein and increased the activity of caspase-3/7, which in turn led to the degradation of PARP. In animals, SKI-I but not SKI-II retarded melanoma growth by 25-40%. Thus, targeting SPHK1 using siRNAs or SKI-I has therapeutic potential for melanoma treatment either alone or in combination with other targeted agents.

Topics: Animals; Apoptosis; Cell Adhesion; Cell Line, Tumor; Cell Proliferation; Cell Survival; Cyclin D1; Down-Regulation; Fibroblasts; G1 Phase Cell Cycle Checkpoints; Humans; Lysophospholipids; Melanocytes; Melanoma; Mice; Molecular Targeted Therapy; Phosphotransferases (Alcohol Group Acceptor); Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Resting Phase, Cell Cycle; RNA, Small Interfering; Skin Neoplasms; Sphingosine; Staurosporine; Thiazoles; Up-Regulation; Xenograft Model Antitumor Assays

Cerebellar granule cells from sphingosine 1-phosphate (S1P) lyase-deficient mice were used to study the toxicity of this potent sphingolipid metabolite in terminally differentiated postmitotic neurons. Based on earlier findings with the lyase-stable, semi-synthetic, cis-4-methylsphingosine phosphate, we hypothesized that accumulation of S1P above a certain threshold induces neuronal apoptosis. The present studies confirmed this conclusion and further revealed that for S1P to induce apoptosis in lyase-deficient neurons it must also be produced by sphingosine-kinase2 (SK2). These conclusions are based on the finding that incubation of lyase-deficient neurons with either sphingosine or S1P results in a similar elevation in cellular S1P; however, only S1P addition to the culture medium induces apoptosis. This was not due to S1P acting on the S1P receptor but to hydrolysis of S1P to sphingosine that was phosphorylated by the cells, as described before for cis-4-methylsphingosine. Although the cells produced S1P from both exogenously added sphingosine as well as sphingosine derived from exogenous S1P, the S1P from these two sources were not equivalent, because the former was primarily produced by SK1, whereas the latter was mainly formed by SK2 (as also was cis-4-methylsphingosine phosphate), based on studies in neurons lacking SK1 or SK2 activity. Thus, these investigations show that, due to the existence of at least two functionally distinct intracellular origins for S1P, exogenous S1P can be neurotoxic. In this model, S1P accumulated due to a defective lyase, however, this cause of toxicity might also be important in other cases, as illustrated by the neurotoxicity of cis-4-methylsphingosine phosphate.

Topics: Animals; Apoptosis; Caspases; Cell Membrane; Cell Survival; Ceramides; Cyclin D1; Cyclin E; Lysophospholipids; Mass Spectrometry; Mice; Mice, Transgenic; Neurons; Phosphotransferases (Alcohol Group Acceptor); Sphingosine

Sphingosine 1-phosphate (Sph-1-P), a product of sphingomyelin metabolism, can act via a family of cognate G protein-coupled receptors or as an intracellular second messenger for agonists acting through their membrane receptors. In view of the general growth promoting and developmental effects of Sph-1-P on target cells, we hypothesized that it plays a role in adaptation of the uterus to pregnancy. We analyzed its potential role and that of the related lysophospholipid lysophosphatidic acid in the pregnant rat uterus by examining changes in mRNA levels of cognate receptors and enzymes involved in their turnover. Of these, only sphingosine kinase-1 (SphK1) was markedly changed ( approximately 30-fold increase), being localized in the glandular epithelium, vasculature, and the myometrium. Uterine SphK1 mRNA and protein levels paralleled those of serum progesterone, and treatment with progesterone or an antagonist elevated or reduced SphK1 mRNA expression, respectively. Progesterone also increased SphK1 mRNA steady-state levels in a rat myometrial/leiomyoma cell line (ELT3). Overexpressing human SphK1 in these cells resulted in increased levels of the cell cycle regulator cyclin D1 and increased myosin light-chain phosphorylation. Ectopic expression of SphK1 also resulted in increased proliferation rates, possibly in conjunction with increased cyclin D1 expression. These studies suggest that the uterine expression of SphK1 mediates processes involved in growth and differentiation of uterine tissues during pregnancy.

Topics: Animals; bcl-X Protein; Cell Line, Tumor; Cell Proliferation; Cyclin D1; Enzymes; Female; Genes, Dominant; Humans; Immunologic Techniques; Leiomyoma; Lysophospholipids; Mutation; Myometrium; Myosin Light Chains; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); Pregnancy; Pregnancy, Animal; Progesterone; Progestins; Rats; Rats, Sprague-Dawley; Receptors, Lysophospholipid; RNA, Messenger; Signal Transduction; Sphingosine; Uterus