sphingosine-kinase and Ovarian-Neoplasms

Ovarian cancer is the most lethal gynaecological malignancy. It is commonly diagnosed at advanced stage when it has metastasised to the abdominal cavity and treatment becomes very challenging. While current standard therapy involving debulking surgery and platinum + taxane-based chemotherapy is associated with high response rates initially, the large majority of patients relapse and ultimately succumb to chemotherapy-resistant disease. In order to improve survival novel strategies for early detection and therapeutics against treatment-refractory disease are urgently needed. A promising new target against ovarian cancer is the sphingolipid pathway which is commonly hijacked in cancer to support cell proliferation and survival and has been shown to promote chemoresistance and metastasis in a wide range of malignant neoplasms. In particular, the sphingosine kinase 1-sphingosine 1-phosphate receptor 1 axis has been shown to be altered in ovarian cancer in multiple ways and therefore represents an attractive therapeutic target. Here we review the roles of sphingolipids in ovarian cancer progression, metastasis and chemoresistance, highlighting novel strategies to target this pathway that represent potential avenues to improve patient survival.

Topics: Animals; Female; Humans; Lysophospholipids; Neoplasm Proteins; Ovarian Neoplasms; Phosphotransferases (Alcohol Group Acceptor); Signal Transduction; Sphingosine; Sphingosine-1-Phosphate Receptors

Adipocytes, active facilitators of epithelial ovarian cancer (EOC) growth, have been implicated in the link between obesity and EOC. However, the current understanding of the mechanisms underlying adipocyte-induced EOC cell proliferation remains incomplete.. We provide the first evidence showing that sphingosine kinase (SphK) 1 is critical for adipocyte-induced EOC cell proliferation. Adipocytes are capable of activating SphK1, which then leads to extracellular signal-regulated kinase (ERK) phosphorylation. Moreover, adipocyte-induced SphK1 activation is ERK dependent. Furthermore, sphingosine 1-phosphate receptor (S1PR) 1 and S1PR3, key components of the SphK1 signalling pathway, participate in adipocyte-mediated growth-promoting action in EOC cells.. Our study reveals a previously unrecognized role of SphK1 in adipocyte-induced growth-promoting action in EOC, suggesting a new target for EOC therapy.

Topics: 3T3-L1 Cells; Adipocytes; Animals; Carcinoma, Ovarian Epithelial; Cell Culture Techniques; Cell Proliferation; Female; Humans; Mice; Ovarian Neoplasms; Phosphotransferases (Alcohol Group Acceptor); Transfection

Follicle-stimulating hormone (FSH) is closely related to the pathogenesis and progression of epithelial ovarian cancer (EOC). However, until now, knowledge relating to FSH-driven signalling pathways that lead to the growth of EOC remained incomplete. We sought to explore whether sphingosine kinase (SphK) could mediate FSH-induced ovarian cancer cell proliferation and which pathway might be involved in this process. The expression of phospho-SphK1 and phospho-SphK2 was detected in sections of EOC tissues by Immunohistochemical staining, and clinical significances were analyzed by statistical analysis. EOC cells were treated with FSH or/and SKI-II. CCK8 assays and colony formation assays were used to investigate cell proliferation. Western blot was carried out to detect protein expression in EOC cell line after treated with FSH. Here, for the first time, we provide evidence that high expression levels of phospho-SphK1 and phospho-SphK2 were both prognostic indicators of overall survival (OS) in EOC. Additionally, the expression levels of both phospho-SphK1 and phospho-SphK2 were closely correlated with the expression level of follicle-stimulating hormone receptor (FSHR) in ovarian cancer tissues. FSH stimulated the phosphorylation of both SphK1 and SphK2 and was able to regulate the survival and growth of ovarian cancer cells by activating SphK1 and SphK2 through ERK1/2. Both isoenzymes of SphK were equally responsible for FSH-induced cell proliferation of EOC. Both Erk1/2 and Akt activation play important roles in mediating FSH-induced cell proliferation after phosphorylation of SphK. Moreover, our data demonstrated that S1P receptor 1 (S1PR1) and S1PR3, key components of the SphK signalling system, were involved in FSH-mediated proliferation of EOC. Taken together, the results of the current study revealed that SphK is an essential mediator in FSH-induced proliferation of ovarian cancer cells in EOC, which indicates a new signalling pathway that controls FSH-mediated growth in EOC and suggests a new strategy that pharmaceutically targets both isoenzymes of SphK for the management of ovarian cancer.

Topics: Carcinoma, Ovarian Epithelial; Cell Line, Tumor; Cell Proliferation; Female; Follicle Stimulating Hormone; Humans; Isoenzymes; Ovarian Neoplasms; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); Signal Transduction

The role of phospholipid signaling in ovarian cancer is poorly understood. Sphingosine-1-phosphate (S1P) is a bioactive metabolite of sphingosine that has been associated with tumor progression through enhanced cell proliferation and motility. Similarly, sphingosine kinases (SPHK), which catalyze the formation of S1P and thus regulate the sphingolipid rheostat, have been reported to promote tumor growth in a variety of cancers. The findings reported here show that exogenous S1P or overexpression of SPHK1 increased proliferation, migration, invasion, and stem-like phenotypes in ovarian cancer cell lines. Likewise, overexpression of SPHK1 markedly enhanced tumor growth in a xenograft model of ovarian cancer, which was associated with elevation of key markers of proliferation and stemness. The diabetes drug, metformin, has been shown to have anticancer effects. Here, we found that ovarian cancer patients taking metformin had significantly reduced serum S1P levels, a finding that was recapitulated when ovarian cancer cells were treated with metformin and analyzed by lipidomics. These findings suggested that in cancer the sphingolipid rheostat may be a novel metabolic target of metformin. In support of this, metformin blocked hypoxia-induced SPHK1, which was associated with inhibited nuclear translocation and transcriptional activity of hypoxia-inducible factors (HIF1α and HIF2α). Further, ovarian cancer cells with high SPHK1 were found to be highly sensitive to the cytotoxic effects of metformin, whereas ovarian cancer cells with low SPHK1 were resistant. Together, the findings reported here show that hypoxia-induced SPHK1 expression and downstream S1P signaling promote ovarian cancer progression and that tumors with high expression of SPHK1 or S1P levels might have increased sensitivity to the cytotoxic effects of metformin. IMPLICATIONS: Metformin targets sphingolipid metabolism through inhibiting SPHK1, thereby impeding ovarian cancer cell migration, proliferation, and self-renewal.

Topics: Animals; Basic Helix-Loop-Helix Transcription Factors; Cell Movement; Female; Humans; Hypoglycemic Agents; Hypoxia-Inducible Factor 1, alpha Subunit; Lysophospholipids; Metformin; Mice; Mice, Nude; Molecular Targeted Therapy; Ovarian Neoplasms; Phosphotransferases (Alcohol Group Acceptor); Sphingosine; Xenograft Model Antitumor Assays

Epithelial ovarian carcinomas account for more than 90% of human ovarian cancers and have become the primary cause of death for gynecological malignancies. Unlimited cell proliferation and resistance to cell apoptosis contribute to the development of ovarian cancers. However, the underlying mechanisms involved in these processes in epithelial ovarian carcinomas are yet poorly understood. In the present study, we examined the Hippo signaling gene expression and investigated the effects of Sphingosine 1-phosphate (S1P) on cell proliferation and the underlying mechanisms in human ovarian cancer cell lines, OVCAR3 and SKOV3. Our results demonstrate that S1P disrupts Hippo signaling by reducing YAP phosphorylation and increasing the expression of CCN1 and CCN2 in both ovarian cancer cells. Furthermore, the increase in CCN1/CCN2 expression contributes to the S1P-induced increase in cancer cell proliferation.

Topics: Active Transport, Cell Nucleus; Cell Cycle Proteins; Cell Line, Tumor; Cell Proliferation; Connective Tissue Growth Factor; Cysteine-Rich Protein 61; Female; Gene Expression Regulation, Neoplastic; Hippo Signaling Pathway; Humans; Lysophospholipids; Nuclear Proteins; Ovarian Neoplasms; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); Prognosis; Protein Serine-Threonine Kinases; Signal Transduction; Sphingosine; Transcription Factors

Sphingosine kinase 1 (SK1) is a key regulator of the cellular balance between proapoptotic and prosurvival sphingolipids. Oncogenic signaling by SK1 relies on its localization to the plasma membrane, which is mediated by the calcium and integrin binding protein CIB1 via its Ca

Topics: Animals; Apoptosis; Biomarkers, Tumor; Calcium-Binding Proteins; Cell Movement; Cell Proliferation; Female; Gene Expression Regulation, Neoplastic; Humans; Mice; Mice, Inbred NOD; Mice, SCID; Neoplasm Invasiveness; Neoplasm Staging; Ovarian Neoplasms; Phosphotransferases (Alcohol Group Acceptor); Prognosis; Tumor Cells, Cultured; Xenograft Model Antitumor Assays

Strong experimental evidence in animal and cellular models supports a pivotal role of sphingosine kinase-1 (SK1) in oncogenesis. In many human cancers, SK1 levels are upregulated and these increases are linked to poor prognosis in patients. Here, by employing untargeted NMR-based metabolomic profiling combined with functional validations, we report the crucial role of SK1 in the metabolic shift known as the Warburg effect in A2780 ovarian cancer cells. Indeed, expression of SK1 induced a high glycolytic rate, characterized by increased levels of lactate along with increased expression of the proton/monocarboxylate symporter MCT1, and decreased oxidative metabolism, associated with the accumulation of intermediates of the tricarboxylic acid cycle and reduction in CO

Topics: Adenocarcinoma; Animals; Carbon Dioxide; Cell Cycle Proteins; Cell Line, Tumor; Female; Glucose; Glucose Transporter Type 3; Glycolysis; Humans; Lactic Acid; Magnetic Resonance Imaging; Metabolomics; Mitochondria; Oncogene Proteins; Ovarian Neoplasms; Oxidation-Reduction; Phosphotransferases (Alcohol Group Acceptor); Prognosis; Tricarboxylic Acids; Up-Regulation

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

Sphingosine kinase 1 (SPHK1), the enzyme that produces sphingosine 1 phosphate (S1P), is known to be highly expressed in many cancers. However, the role of SPHK1 in cells of the tumor stroma remains unclear. Here, we show that SPHK1 is highly expressed in the tumor stroma of high-grade serous ovarian cancer (HGSC), and is required for the differentiation and tumor promoting function of cancer-associated fibroblasts (CAFs). Knockout or pharmacological inhibition of SPHK1 in ovarian fibroblasts attenuated TGF-β-induced expression of CAF markers, and reduced their ability to promote ovarian cancer cell migration and invasion in a coculture system. Mechanistically, we determined that SPHK1 mediates TGF-β signaling via the transactivation of S1P receptors (S1PR2 and S1PR3), leading to p38 MAPK phosphorylation. The importance of stromal SPHK1 in tumorigenesis was confirmed in vivo, by demonstrating a significant reduction of tumor growth and metastasis in SPHK1 knockout mice. Collectively, these findings demonstrate the potential of SPHK1 inhibition as a novel stroma-targeted therapy in HGSC.

Topics: Animals; Apoptosis; Blotting, Western; Cell Differentiation; Cell Movement; Cell Proliferation; Cystadenocarcinoma, Serous; Female; Fibroblasts; Fluorescent Antibody Technique; Humans; Immunoenzyme Techniques; Lysophospholipids; Mice; Mice, Knockout; Myofibroblasts; Neoplasm Grading; Ovarian Neoplasms; Phosphorylation; Phosphotransferases (Alcohol Group Acceptor); Prognosis; Real-Time Polymerase Chain Reaction; Receptors, Lysosphingolipid; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Signal Transduction; Sphingosine; Survival Rate; Transforming Growth Factor beta; Tumor Cells, Cultured

Sphingosine kinase 1 (SK1) is over-expressed in multiple types of human cancer. SK1 has growth-promoting effects and has been proposed as a potential therapeutic target. We investigated the therapeutic effects of SK1 inhibition in epithelial ovarian carcinoma (EOC). SK1 siRNA or inhibitors were tested in EOC cell lines, including A2780, SKOV3ip1, A2780-CP20, SKOV3-TR, ES2 and RMG2. Cells were treated with SK inhibitor or FTY720, and cell proliferation, apoptosis, angiogenesis and invasion were examined by MTT, FACS, ELISA and wound-healing assays, respectively. In vivo experiments were performed to test the effects of FTY720 on tumor growth in orthotopic mouse xenografts of EOC cell lines A2780 or SKOV3ip1 and a patient-derived xenograft (PDX) model of clear cell ovarian carcinoma (CCC). Blocking SK1 with siRNA or inhibitors significantly reduced proliferation, angiogenesis and invasion, and increased apoptosis in chemosensitive (A2780 and SKOV3ip1) and chemoresistant (A2780-CP20, SKOV3-TR, ES2 and RMG2) EOC cells. SK1 inhibitors also decreased the intracellular enzymatic activity of SK1. Furthermore, FTY720 treatment significantly decreased the in vivo tumor weight in xenograft models of established cell lines (A2780 and SKOV3ip1) and a PDX model for CCC compared to control (p < 0.05). These results support therapeutic targeting of SK1 as a potential new strategy for EOC.

Topics: Adenocarcinoma, Clear Cell; Animals; Carcinoma, Ovarian Epithelial; Cell Line, Tumor; Cell Proliferation; Female; Fingolimod Hydrochloride; Humans; Immunosuppressive Agents; Mice; Mice, Nude; Neoplasm Transplantation; Neoplasms, Glandular and Epithelial; Ovarian Neoplasms; Phosphotransferases (Alcohol Group Acceptor); Propylene Glycols; Protein Kinase Inhibitors; RNA, Small Interfering; Sphingosine; Xenograft Model Antitumor Assays

ABC294640, a selective inhibitor of sphingosine kinase-2, inhibits the formation of sphingosine 1-phosphate (S1P), a signaling lipid implicated in promoting tumor survival. We investigated the anticancer activity of ABC294640 in two ovarian cancer cell lines, BG-1 and Caov-3. ABC294640 dose-dependently inhibited clonogenic survival and cell viability of both ovarian cancer lines in vitro. Using enzyme-linked immunosorbant assays and western blot detection in chemoresistant Caov-3 cells, treatment with ABC294640 alone also potentiated bcl-2-associated X-protein and caspase-9 transcription levels, although it did not significantly increase apoptotic cell death. Interestingly, ABC294640 administered to Caov-3 ovarian cancer cells in conjunction with paclitaxel induced apoptotic cell death through activation of caspase-9. Induction of apoptosis may mediate the anticancer effect of ABC294640 in ovarian cancer, although its precise antitumor mechanism is unclear. Ultimately, through its inhibition of S1P formation and subsequent effects on critical survival signaling cascades, ABC294640 may prove to be a useful adjunct to help re-sensitize tumors to standard therapy.

Topics: Adamantane; Antineoplastic Agents; Apoptosis; bcl-2-Associated X Protein; Cell Line, Tumor; Drug Resistance, Neoplasm; Enzyme Inhibitors; Female; Humans; Ovarian Neoplasms; Phosphotransferases (Alcohol Group Acceptor); Pyridines

Recent published studies suggest that increasing levels of ceramides enhance the chemo-sensitivity of curcumin. Using in vitro approaches, we analyzed the impact of sphingosine kinase-1 (SphK-1) inhibition on ceramide production, and evaluated SphK1 inhibitor II (SKI-II) as a potential curcumin chemo-sensitizer in ovarian cancer cells. We found that SphK1 is overexpressed in ovarian cancer patients' tumor tissues and in cultured ovarian cancer cell lines. Inhibition of SphK1 by SKI-II or by RNA interference (RNAi) knockdown dramatically enhanced curcumin-induced apoptosis and growth inhibition in ovarian cancer cells. SKI-II facilitated curcumin-induced ceramide production, p38 activation and Akt inhibition. Inhibition of p38 by the pharmacological inhibitor (SB 203580), a dominant-negative expression vector, or by RNAi diminished curcumin and SKI-II co-administration-induced ovarian cancer cell apoptosis. In addition, restoring Akt activation introducing a constitutively active Akt, or inhibiting ceramide production by fumonisin B1 also inhibited the curcumin plus SKI-II co-administration-induced in vitro anti-ovarian cancer effect, suggesting that ceramide accumulation, p38 activation and Akt inhibition are downstream effectors. Our findings suggest that low, well-tolerated doses of SKI-II may offer significant improvement to the clinical curcumin treatment of ovarian cancer.

Topics: Apoptosis; Apoptosis Regulatory Proteins; Blotting, Western; Cell Line, Tumor; Cell Proliferation; Ceramides; Curcumin; Enzyme-Linked Immunosorbent Assay; Female; Growth Inhibitors; Humans; Ovarian Neoplasms; Phosphotransferases (Alcohol Group Acceptor); RNA Interference; RNA, Small Interfering; Transfection

A2780 human ovarian carcinoma cells respond to treatment with the synthetic retinoid N-(4-hydroxyphenyl)retinamide (HPR) with the production of dihydroceramide and with a concomitant reduction of cell proliferation and induction of apoptosis. The derived HPR-resistant clonal cell line, A2780/HPR, is less responsive to HPR in terms of dihydroceramide generation. In this report, we show that the production of sphingosine 1-phosphate (S1P) is significantly higher in A2780/HPR versus A2780 cells due to an increased sphingosine kinase (SK) activity and SK-1 mRNA and protein levels. Treatment of A2780 and A2780/HPR cells with a potent and highly selective pharmacological SK inhibitor effectively reduced S1P production and resulted in a marked reduction of cell proliferation. Moreover, A2780/HPR cells treated with a SK inhibitor were sensitized to the cytotoxic effect of HPR, due to an increased dihydroceramide production. On the other hand, the ectopic expression of SK-1 in A2780 cells was sufficient to induce HPR resistance in these cells. Challenge of A2780 and A2780/HPR cells with agonists and antagonists of S1P receptors had no effects on their sensitivity to the drug, suggesting that the role of SK in HPR resistance in these cells is not mediated by the S1P receptors. These data clearly demonstrate a role for SK in determining resistance to HPR in ovarian carcinoma cells, due to its effect in the regulation of intracellular ceramide/S1P ratio, which is critical in the control of cell death and proliferation.

Topics: Antineoplastic Agents; Cell Death; Cell Line, Tumor; Cell Proliferation; Cell Survival; Drug Resistance, Neoplasm; Female; Fenretinide; Humans; Lipids; Mass Spectrometry; Models, Biological; Ovarian Neoplasms; Phosphotransferases (Alcohol Group Acceptor); RNA, Messenger