FTY720 for cancer therapy (Review). Oncol Rep. 2013;30:2571-2578. [PMID: 24100923 DOI: 10.3892/or.2013.2765]

Potential applications of ferroptosis inducers and regulatory molecules in hematological malignancy therapy

Ferroptosis, a novel form of iron-dependent cell death, has emerged as a potential avenue for promoting tumor cell death by causing cell membrane rupture and the accumulation of lipid peroxides (LPO) in the cell. Since its discovery in 2012, extensive research has been conducted to explore the mechanism of ferroptosis inducers, including erastin, sulfasalazine, and sorafenib. These compounds inhibit system XC-, while Ras-selective lethal small molecule 3 (RSL3) and FION2 specifically target GPX4 to promote ferroptosis. Therefore, targeting ferroptosis presents a promising therapeutic approach for malignant tumors. While the study of ferroptosis in solid tumors has made significant progress, there is limited information available on its role in hematological tumors. This review aims to summarize the molecular mechanisms of ferroptosis inducers and discuss their clinical applications in hematological malignancies. Furthermore, the identification of non-coding RNAs (ncRNAs) and genes that regulate key molecules in the ferroptosis pathway could provide new targets and establish a molecular theoretical foundation for exploring novel ferroptosis inducers in hematological malignancies.

Temozolomide Resistance in Glioblastoma by NRF2: Protecting the Evil

The transcription factor NRF2 is constitutively active in glioblastoma, a highly aggressive brain tumor subtype with poor prognosis. Temozolomide (TMZ) is the primary chemotherapeutic agent for this type of tumor treatment, but resistance to this drug is often observed. This review highlights the research that is demonstrating how NRF2 hyperactivation creates an environment that favors the survival of malignant cells and protects against oxidative stress and TMZ. Mechanistically, NRF2 increases drug detoxification, autophagy, DNA repair, and decreases drug accumulation and apoptotic signaling. Our review also presents potential strategies for targeting NRF2 as an adjuvant therapy to overcome TMZ chemoresistance in glioblastoma. Specific molecular pathways, including MAPKs, GSK3β, βTRCP, PI3K, AKT, and GBP, that modulate NRF2 expression leading to TMZ resistance are discussed, along with the importance of identifying NRF2 modulators to reverse TMZ resistance and develop new therapeutic targets. Despite the significant progress in understanding the role of NRF2 in GBM, there are still unanswered questions regarding its regulation and downstream effects. Future research should focus on elucidating the precise mechanisms by which NRF2 mediates resistance to TMZ, and identifying potential novel targets for therapeutic intervention.

Immunomodulatory drug fingolimod (FTY720) restricts the growth of opportunistic yeast Candida albicans in vitro and in a mouse candidiasis model

Fingolimod (FTY720) is a drug derived from the fungicidal compound myriocin. As it was unclear whether FTY720 has antifungal effects as well, we aimed to characterize its effect on Candida albicans in vitro and in a mouse candidiasis model. First, antifungal susceptibility testing was performed in vitro. Then, a randomized, six-arm, parallel, open-label trial was conducted on 48 mice receiving oral FTY720 (0.3 mg/kg/day), intraperitoneal C. albicans inoculation, or placebo with different combinations and chorological patterns. The outcome measures of the trial included serum concentrations of interleukin-10 and interferon-gamma, absolute lymphocyte counts, and fungal burden values in the mice's livers, kidneys, and vaginas. Broth microdilution assay revealed FTY720's minimum inhibitory concentration (MIC99) to be 0.25 mg/mL for C. albicans. The infected mice treated with FTY720 showed lower fungal burden values than the ones not treated with FTY720 (p<0.05). As expected, the mice treated with FTY720 showed a less-inflammatory immune profile compared to the ones not treated with FTY720. We hypothesize that FTY720 synergizes the host's innate immune functions by inducing the production of reactive oxygen species. Further studies are warranted to unveil the mechanistic explanations of our observations and clarify further aspects of repurposing FTY720 for clinical antifungal usage.

Determining the Anticancer Activity of Sphingosine Kinase Inhibitors Containing Heteroatoms in Their Tail Structure

Sphingosine kinase (SK) enzyme, a central player of sphingolipid rheostat, catalyzes the phosphorylation of sphingosine to the bioactive lipid mediator sphingosine 1 phosphate (S1P), which regulates cancer cell proliferation, migration, differentiation, and angiogenesis through its extracellular five G protein-coupled S1P receptors (S1PR_1–5). Recently, several research studies on SK inhibitors have taken place in order use them for the development of novel anticancer-targeted therapy. In this study, we designed and synthesized analog derivatives of known SK1 inhibitors, namely RB005 and PF-543, by introducing heteroatoms at their tail structure, as well as investigated their anticancer activities and pharmacokinetic parameters in vitro. Compounds 1–20 of RB005 and PF-543 derivatives containing an aliphatic chain or a tail structure of benzenesulfonyl were synthesized. All compounds of set 1 (1–10) effectively reduced cell viability in both HT29 and HCT116 cells, whereas set 2 derivatives (11–20) showed poor anticancer effect. Compound 10, having the highest cytotoxic effect (48 h, HT29 IC₅₀ = 6.223 µM, HCT116 IC₅₀ = 8.694 µM), induced HT29 and HCT116 cell death in a concentration-dependent manner through the mitochondrial apoptotic pathway, which was demonstrated by increased annexin V-FITC level, and increased apoptotic marker cleaved caspase-3 and cleaved PARP. Compound 10 inhibited SK1 by 20%, and, thus, the S1P level decreased by 42%. Unlike the apoptosis efficacy, the SK1 inhibitory effect and selectivity of the PF-543 derivative were superior to that of the RB005 analog. As a result, compounds with an aliphatic chain tail exhibited stronger apoptotic effects. However, this ability was not proportional to the degree of SK inhibition. Compound 10 increased the protein phosphatase 2A (PP2A) activity (1.73 fold) similar to FTY720 (1.65 fold) and RB005 (1.59 fold), whereas compounds 11 and 13 had no effect on PP2A activation. Since the PP2A activity increased in compounds with an aliphatic chain tail, it can be suggested that PP2A activation has an important effect on anticancer and SK inhibitory activities.

Differential Expression of the Sphingolipid Pathway Is Associated with Sensitivity to the PP2A Activator FTY720 in Colorectal Cancer Cell Lines

Protein phosphatase 2A (PP2A) is a ubiquitously expressed intracellular serine/threonine phosphatase. Deregulation of PP2A is a common event associated with adenocarcinomas of the colon and rectum. We have previously shown that breast cancer cell lines are sensitive to the PP2A activator FTY720, and that sensitivity is predicted by high Aurora kinase A (AURKA) mRNA expression. In this study, we hypothesized that high relative AURKA expression could predict sensitivity to FTY720-induced apoptosis in colorectal cancer (CRC). The CRC cell lines NCI H716, COLO320DM, DLD-1, SW480, and HT-29 show a high relative AURKA expression as compared to LS411N, T84, HCT116, SW48, and LOVO. Following viability assays, LS411N, T84, HCT116, and SW480 were shown to be sensitive to FTY720, whereas DLD-1 and HT-29 were non-sensitive. Hence, AURKA mRNA expression does not predict sensitivity to FTY720 in CRC cell lines. Differentially expressed genes (DEGs) were obtained by comparing the sensitive CRC cell lines (LS411N and HCT116) against the non-sensitive (HT-29 and DLD-1). We found that 253 genes were significantly altered in expression, and upregulation of CERS4, PPP2R2C, GNAZ, PRKCG, BCL2, MAPK12, and MAPK11 suggests the involvement of the sphingolipid signaling pathway, known to be activated by phosphorylated-FTY720. In conclusion, although AURKA expression did not predict sensitivity to FTY720, it is evident that specific CRC cell lines are sensitive to 5 µM FTY720, potentially because of the differential expression of genes involved in the sphingolipid pathway.

Targeting the Sphingosine Kinase/Sphingosine-1-Phosphate Signaling Axis in Drug Discovery for Cancer Therapy

Sphingolipid metabolites have emerged as critical players in the regulation of various physiological processes. Ceramide and sphingosine induce cell growth arrest and apoptosis, whereas sphingosine-1-phosphate (S1P) promotes cell proliferation and survival. Here, we present an overview of sphingolipid metabolism and the compartmentalization of various sphingolipid metabolites. In addition, the sphingolipid rheostat, a fine metabolic balance between ceramide and S1P, is discussed. Sphingosine kinase (SphK) catalyzes the synthesis of S1P from sphingosine and modulates several cellular processes and is found to be essentially involved in various pathophysiological conditions. The regulation and biological functions of SphK isoforms are discussed. The functions of S1P, along with its receptors, are further highlighted. The up-regulation of SphK is observed in various cancer types and is also linked to radio- and chemoresistance and poor prognosis in cancer patients. Implications of the SphK/S1P signaling axis in human pathologies and its inhibition are discussed in detail. Overall, this review highlights current findings on the SphK/S1P signaling axis from multiple angles, including their functional role, mechanism of activation, involvement in various human malignancies, and inhibitor molecules that may be used in cancer therapy.

Sphingosine Kinase 1 Signaling in Breast Cancer: A Potential Target to Tackle Breast Cancer Stem Cells

Sphingosine kinases (SPHKs) are conserved lipid enzymes that catalyze the formation of sphingosine-1-phosphate (S1P) through ATP-dependent phosphorylation of sphingosine. Two distinct SPHK isoforms, namely SPHK1 and SPHK2, have been identified to date, and the former has been implicated for its oncogenic roles in cancer development and progression. While SPHK1 signaling axis has been extensively studied in non-stem breast cancer cells, recent evidence has emerged to suggest a role of SPHK1 in regulating cancer stem cells (CSCs). With the clinical implications of CSCs in disease relapse and metastasis, it is believed that therapeutic approaches that can eradicate both non-stem cancer cells and CSCs could be a key to cancer cure. In this review, we first explore the oncogenic functions of sphingosine kinase 1 in human cancers and summarize current research findings of SPHK1 signaling with a focus on breast cancer. We also discuss the therapeutic potentials and perspectives of targeting SPHK1 signaling in breast cancer and cancer stem cells. We aim to offer new insights and inspire future studies looking further into the regulatory functions of SPHK1 in CSC-driven tumorigenesis, uncovering novel therapeutic avenues of using SPHK1-targeted therapy in the treatment of CSC-enriched refractory cancers.

FTY720 induces ferroptosis and autophagy via PP2A/AMPK pathway in multiple myeloma cells

AIMS

Multiple myeloma (MM) is the second hematological plasma cell malignany and sensitive to fingolimod (FTY720), a novel immunosuppressant. Previous study shows FTY720-induced apoptosis and autophagy can cause cell death in MM cells, however, the high death rate cannot fully be explained. The study aims to investigate further mechanism of how FTY720 kills MM cells.

MATERIALS AND METHODS

Experiments are performed on 25 human primary cell samples and two MM cell lines by flow cytometry, fluorescence microscopy, and transmission electron microscopy. Expressions of relative factors are tested by qRT-PCR or western blot.

KEY FINDINGS

Ferroptosis-specific inhibitors, deferoxamine mesylate (DFOM) and ferropstatin-1 (Fer-1), reverse FTY720-induced cell death in MM cells. Glutathione peroxidase 4 (GPX4) and soluble carrier family 7 member 11 (SLC7A11), key regulators of ferroptosis, are highly expressed in primary MM cells and can be decreased by FTY720 at the mRNA and protein level in MM cells. In addition, FTY720 induces other characteristic changes of ferroptosis. Furthermore, FTY720 can dephosphorylate AMP-activated protein kinase subunit ɑ (AMPKɑ) at the Thr172 site by activating protein phosphatase 2A (PP2A) and reduce the expression of phosphorylated eukaryotic elongation factor 2 (eEF2), finally cause MM cell death. Using LB-100, a PP2A inhibitor, AICAR, an agonist of AMPK, and bafilomycin A1 (Baf-A1), an autophagy inhibitor, we discover that FTY720 induces ferroptosis and autophagy through the PP2A/AMPK pathway, and ferroptosis and autophagy can reinforce each other.

SIGNIFICANCE

These results provide a new perspective on the treatment of MM.

Inhibitors of Ceramide- and Sphingosine-Metabolizing Enzymes as Sensitizers in Radiotherapy and Chemotherapy for Head and Neck Squamous Cell Carcinoma

In the treatment of advanced head and neck squamous cell carcinoma (HNSCC), including oral SCC, radiotherapy is a commonly performed therapeutic modality. The combined use of radiotherapy with chemotherapy improves therapeutic effects, but it also increases adverse events. Ceramide, a central molecule in sphingolipid metabolism and signaling pathways, mediates antiproliferative responses, and its level increases in response to radiotherapy and chemotherapy. However, when ceramide is metabolized, prosurvival factors, such as sphingosine-1-phosphate (S1P), ceramide-1-phosphate (C1P), and glucosylceramide, are produced, reducing the antitumor effects of ceramide. The activities of ceramide- and sphingosine-metabolizing enzymes are also associated with radio- and chemo-resistance. Ceramide analogs and low molecular-weight compounds targeting these enzymes exert anticancer effects. Synthetic ceramides and a therapeutic approach using ultrasound have also been developed. Inhibitors of ceramide- and sphingosine-metabolizing enzymes and synthetic ceramides can function as sensitizers of radiotherapy and chemotherapy for HNSCC.

Verification of the Necessity of the Tolyl Group of PF-543 for Sphingosine Kinase 1 Inhibitory Activity

PF-543, the most potent sphingosine kinase (SK) inhibitor, does not demonstrate effective anticancer activity in some cancer cells, unlike other known SK1 inhibitors. PF-543 has a non-lipid structure with a unique toluene backbone; however, the importance of this structure remains unclear. Therefore, the purpose of this study was to investigate changes in SK inhibitory and anticancer activities and to explore the role of the tolyl group structure of PF-543 through various modifications. We transformed the methyl group of PF-543 into hydrogen, fluorine, and hydroxy. PF-543 derivatives in which the methyl group was substituted by hydrogen and fluorine (compound 5) demonstrated SK1 inhibitory and anticancer activities similar to PF-543. Moreover, we performed molecular modeling studies of PF-543 and compound 5. To assess the metabolic stability of PF-543 and compound 5, we determined their degree of degradation using the liver microsomes of four different animal species (human, dog, rat, and mouse). However, both PF-543 and compound 5 showed poor microsomal stability. Therefore, for the medical applications of PF-543, the structural modifications of its other parts may be necessary. Our results provide important information for the design of additional PF-543 analogs.

An okadaic acid fragment analogue prevents nicotine-induced resistance to cisplatin by recovering PP2A activity in non-small cell lung cancer cells

We herein report the design, synthesis, and functional impact of an okadaic acid (OA) small analogue, ITH12680, which restores the activity of phosphoprotein phosphatase 2A (PP2A), whose deficient activity has been implicated in nicotine-mediated tumor progression and chemoresistance in non-small cell lung cancer (NSCLC). For its design, we paid attention to the structure of the PP2A-OA complex, where the C16-C38 OA fragment confers PP2A affinity and selectivity, but it is not involved in the inhibitory effect. Confirming this hypothesis, PP2A activity was not inhibited by ITH12680. By contrast, the compound partially restored OA-exerted PP2A inhibition in vitro. Moreover, flow cytometry and immunoblotting experiments revealed that ITH12680 reversed nicotine-induced cisplatin resistance in NSCLC cells, as it prevented nicotine-induced reduction of Bax expression and inhibited nicotine-mediated activation of cell survival and proliferation kinases, Akt and ERK1/2. Our findings suggest that the rescue of nicotine-inhibited PP2A activity could diminish the resistance to cisplatin treatment observed in NSCLC patients who continue smoking.

S1PR2 inhibitors potently reverse 5-FU resistance by downregulating DPD expression in colorectal cancer

In this study, S1PR2 was reckoned as a brand-new GPCR target for designing inhibitors to reverse 5-FU resistance. Herein a series of pyrrolidine pyrazoles as the S1PR2 inhibitors were designed, synthesized and evaluated for their activities of anti-FU-resistance. Among them, the most promising compound JTE-013, exhibited excellent inhibition on DPD expression and potent anti-FU-resistance activity in various human cancer cell lines, along with the in vivo HCT116^DPD cells xenograft model, in which the inhibition rate of 5-FU was greatly increased from 13.01%-75.87%. The underlying mechanism was uncovered that JTE-013 demonstrated an anti-FU-resistance activity by blocking S1PR2 internalization to the endoplasmic reticulum (ER), which inhibited the degradation of 5-FU into α-fluoro-β-alanine (FBAL) by downregulating tumoral DPD expression. Overall, JTE-013 could serve as the lead compound for the discovery of new anti-FU-resistance drugs. SIGNIFICANCE: This study provides novel insights that S1PR2 inhibitors could sensitize 5-FU therapy in colorectal cancer.

Multiple Sclerosis and Cancer: The Ying-Yang Effect of Disease Modifying Therapies

Over the past two decades, the field of multiple sclerosis (MS) has been transformed by the rapidly expanding arsenal of new disease modifying therapies (DMTs). Current DMTs for MS aim to modulate innate and adaptive immune responses toward a less inflammatory phenotype. Since the immune system is also critical for identifying and eliminating malignant cells, immunosuppression from DMTs may predictably increase the risk of cancer development in MS patients. Compared with healthy controls, patients with autoimmune conditions, such as MS, may already have a higher risk of developing certain malignancies and this risk may further be magnified by DMT treatments. For those patients who develop both MS and cancer, these comorbid presentations create a challenge for clinicians on how to therapeutically address management of cancer in the context of MS autoimmunity. As there are currently no accepted guidelines for managing MS patients with prior history of or newly developed malignancy, we undertook this review to evaluate the molecular mechanisms of current DMTs and their potential for instigating and treating cancer in patients living with MS.

Synthesis and Biological Evaluation of BODIPY-PF-543

Sphingosine-1-phosphate (S1P) regulates the proliferation of various cells and promotes the growth of cancer cells. Sphingosine kinase (SK), which transforms sphingosine into S1P, has two isotypes: SK1 and SK2. To date, both isotypes are known to be involved in the proliferation of cancer cells. PF-543, an SK1 inhibitor developed by Pfizer, strongly inhibits SK1. However, despite its strong SK1 inhibitory effect, PF-543 shows low anticancer activity in vitro. Therefore, additional biological evidence on the anticancer activity of SK1 inhibitor is required. The present study aimed to investigate the intracellular localization of PF-543 and identify its association with anticancer activity by introducing a fluoroprobe into PF-543. Boron–dipyrromethene (BODIPY)-introduced PF-543 has a similar SK1 inhibitory effect as PF-543. These results indicate that the introduction of BODIPY does not significantly affect the inhibitory effect of SK1. In confocal microscopy after BODIPY-PF-543 treatment, the compound was mainly located in the cytosol of the cells. This study demonstrated the possibility of introducing fluorescent material into an SK inhibitor and designing a synthesized compound that is permeable to cells while maintaining the SK inhibitory effect.

Synthesis and Biological Evaluation of PF-543 Derivative Containing Aliphatic Side Chain

The PF-543 is known as a potent and selective inhibitor of sphingosine kinase (SK) 1 amongst all the SK inhibitors known to date. In a recently reported study by Pfizer on the synthesis of PF-543 derivatives and the SK inhibitory effects, the introduction of propyl moiety into sulfonyl group of PF-543 in the case of 26b revealed an excellent result of 1.7 nM of IC₅₀ of SK1, suggesting the potential substitution of chain structure for benzenesulfonyl structure. In the present work, we aimed for identification of antitumor activity and inhibitory effects of PF-543 derivative containing aliphatic long chain (similar to known SK inhibitors) on SK1. The synthesized compound 2 exhibited an inhibitory effect on SK1 in a manner similar to that of PF-543; the PF-543 derivative manifested similar antitumor activity on HT29, HCT116 (colorectal cancer cell line), and AGS (gastric cancer cell line) cells. Also, from the docking study conducted with PF-543 and compound 2, it was apparent that the aliphatic chain in compound 2 could probably replace benzenesulfonyl structure of PF-543.

PP2A activation alone and in combination with cisplatin decreases cell growth and tumor formation in human HuH6 hepatoblastoma cells

Despite an increase in incidence, treatments for hepatoblastoma remain virtually unchanged for the past 20 years, emphasizing the need for novel therapeutics. FTY720 (fingolimod) is an immunomodulator approved for use in multiple sclerosis in children that has been demonstrated to have anti-cancer properties in multiple cancer types. We have demonstrated that FTY720 activates PP2A in hepatoblastoma, but does not do so via inhibition of the endogenous inhibitors, CIP2A and I2PP2A, as previously observed in other cancers. PP2A activation in hepatoblastoma decreased cell viability, proliferation, and motility and induced apoptosis. In a subcutaneous xenograft model, FTY720 decreased tumor growth. FTY720 in combination with the standard chemotherapeutic, cisplatin, decreased proliferation in a synergistic manner. Finally, animals bearing subcutaneous hepatoblastoma xenografts treated with FTY720 and cisplatin in combination had significantly decreased tumor growth compared to those treated with either drug alone. These findings show that targeting PP2A with FTY70 shows promise in the treatment of hepatoblastoma and that combining FTY720 with cisplatin may be a novel and effective strategy to better treat this devastating pediatric liver tumor.

In search of constrained FTY720 and phytosphingosine analogs as dual acting anticancer agents targeting metabolic and epigenetic pathways

A series of compounds containing pyrrolidine and pyrrolizidine cores with appended hydrophobic substituents were prepared as constrained analogs of FTY720 and phytosphingosine. The effect of these compounds on the viability of cancer cells, on downregulation of the nutrient transport systems, and on their ability to cause vacuolation was studied. An attempt to inhibit HDACs with some phosphate esters of our analogs was thwarted by our failure to reproduce the reported inhibitory action of FTY720-phosphate.

Dual functions of ARP101 in targeting membrane type-1 matrix metalloproteinase: Impact on U87 glioblastoma cell invasion and autophagy signaling

Membrane type-1 matrix metalloproteinase (MT1-MMP) possesses both extracellular proteolytic and intracellular signal-transducing functions in tumorigenesis. An imbalance in MT1-MMP expression and/or function triggers a metastatic, invasive, and therapy resistance phenotype. MT1-MMP is involved in extracellular matrix (ECM) proteolysis, activation of latent MMPs, as well as in autophagy signaling in human hepatoma and glioblastoma cells. A low autophagy index in tumorigenesis has been inferred by recent studies where autophagic capacity was decreased during tumor progression. Here, we establish ARP101 as a dual-function small-molecule inhibitor against MT1-MMP ECM hydrolysis and autophagy signal-transducing functions in a model of grade IV glioblastoma cells. ARP101 inhibited concanavalin-A-mediated proMMP-2 activation into MMP-2, as well as MT1-MMP auto-proteolytic processing. When overexpressing recombinant Wt MT1-MMP, ARP101 inhibited proMMP-2 activation and triggered the formation of MT1-MMP oligomers that required trafficking to the plasma membrane. ARP101 further induced cell autophagy as reflected by increased formation of acidic vacuole organelles, LC3 puncta, and autophagy-related protein ATG9 transcription. These were all significantly reversed upon siRNA-mediated gene silencing of MT1-MMP. ARP101 can thus concomitantly inhibit MT1-MMP extracellular catalytic function and exploit its intracellular transducing signal function to trigger autophagy-mediated cell death in U87 glioblastoma cancer cells.

Synthesis of Novel FTY720 Analogs with Anticancer Activity through PP2A Activation

FTY720 inhibits various cancers through PP2A activation. The structure of FTY720 is also used as a basic structure for the design of sphingosine kinase (SK) inhibitors. We have synthesized derivatives using an amide chain in FTY720 with a phenyl backbone, and then compounds were screened by an MTT cell viability assay. The PP2A activity of compound 7 was examined. The phosphorylation levels of AKT and ERK, downstream targets of PP2A, in the presence of compound 7, were determined. Compound 7 may exhibit anticancer effects through PP2A activation rather than the mechanism by inhibition of SK1 in cancer cells. In the docking study of compound 7 and PP2A, the amide chain of compound 7 showed an interaction with Asn61 that was different from FTY720, which is expected to affect the activity of the compound.

Fingolimod interrupts the cross talk between estrogen metabolism and sphingolipid metabolism within prostate cancer cells

Sphingolipids are critical regulators of tumor microenvironments and play an important role in estrogen-dependent cancers. Estrogen and estrogen metabolites were found to be involved in prostate cancer. Fingolimod (FTY720) is a sphingokinase-1 (SphK1) inhibitor with anticancer properties against various tumor cell types. Herein, we investigated the interference of FTY720 with the cross talk between sphingolipid metabolism and estrogen metabolism within prostate cancer cells. FTY720 showed cytotoxic antiproliferative effects against androgen-dependent and -independent prostate cancer cells with IC₅₀ ranging from 3.0 ± 0.3 to 6.8 ± 1.7 μM. Exposure of prostate cancer cells to FTY720 resulted in a dramatic decrease in the concentration of estradiol, estrone, 4-hydroxyestradiol and 16α-hydroxyestrone compared to control cells. However, FTY720 significantly increased the concentration of 2-methoxyestrone and 2-methoxyestradiol within prostate cancer cells. This was mirrored by significant downregulating of the expression of estrogen and catechol estrogen-synthesizing enzymes (CYP19, CYP1A1 and CYP1B1) within prostate cancer cells. On the other hand, FTY720 significantly upregulated the expression of catechol estrogen-detoxifying enzyme (COMT). Additionally, FTY720 abolished estrogen-stimulated expression of ERα and basal expression of ERβ within prostate cancer cells. Furthermore, FTY720 suppressed the expression of the ER-downstream regulated genes, CXCR4 and cyclin D1. Reciprocally, it was found that estradiol and catechol estrogens significantly induced the expression of SphK1 while methoxylated catechol estrogen suppressed its expression within prostate cancer cells in a dose-dependent manner. Current research has highlighted the hazardous influence of the estrogenic component to prostate cancer. We found that fingolimod (FTY720) could modulate the estrogenic micromilieu and interrupt its cross talk with sphingolipid metabolism.

More than Just an Immunosuppressant: The Emerging Role of FTY720 as a Novel Inducer of ROS and Apoptosis

Fingolimod hydrochloride (FTY720) is a first-in-class of sphingosine-1-phosphate (S1P) receptor modulator approved to treat multiple sclerosis by its phosphorylated form (FTY720-P). Recently, a novel role of FTY720 as a potential anticancer drug has emerged. One of the anticancer mechanisms of FTY720 involves the induction of reactive oxygen species (ROS) and subsequent apoptosis, which is largely independent of its property as an S1P modulator. ROS have been considered as a double-edged sword in tumor initiation/progression. Intriguingly, prooxidant therapies have attracted much attention due to its efficacy in cancer treatment. These strategies include diverse chemotherapeutic agents and molecular targeted drugs such as sulfasalazine which inhibits the CD44v-xCT (cystine transporter) axis. In this review, we introduce our recent discoveries using a chemical genomics approach to uncover a signaling network relevant to FTY720-mediated ROS signaling and apoptosis, thereby proposing new potential targets for combination therapy as a means to enhance the antitumor efficacy of FTY720 as a ROS generator. We extend our knowledge by summarizing various measures targeting the vulnerability of cancer cells' defense mechanisms against oxidative stress. Future directions that may lead to the best use of FTY720 and ROS-targeted strategies as a promising cancer treatment are also discussed.

Non-immunosuppressive triazole-based small molecule induces anticancer activity against human hormone-refractory prostate cancers: the role in inhibition of PI3K/AKT/mTOR and c-Myc signaling pathways

A series of triazole-based small molecules that mimic FTY720-mediated anticancer activity but minimize its immunosuppressive effect have been produced. SPS-7 is the most effective derivative displaying higher activity than FTY720 in anti-proliferation against human hormone-refractory prostate cancer (HRPC). It induced G1 arrest of cell cycle and subsequent apoptosis in thymidine block-mediated synchronization model. The data were supported by a decrease of cyclin D1 expression, a dramatic increase of p21 expression and an associated decrease in RB phosphorylation. c-Myc overexpression replenished protein levels of cyclin D1 indicating that c-Myc was responsible for cell cycle regulation. PI3K/Akt/mTOR signaling pathways through p70S6K- and 4EBP1-mediated translational regulation are critical to cell proliferation and survival. SPS-7 significantly inhibited this translational pathway. Overexpression of Myr-Akt (constitutively active Akt) completely abolished SPS-7-induced inhibitory effect on mTOR/p70S6K/4EBP1 signaling and c-Myc protein expression, suggesting that PI3K/Akt serves as a key upstream regulator. SPS-7 also demonstrated substantial anti-tumor efficacy in an in vivo xenograft study using PC-3 mouse model. Notably, FTY720 but not SPS-7 induced a significant immunosuppressive effect as evidenced by depletion of marginal zone B cells, down-regulation of sphingosine-1-phosphate receptors and a decrease in peripheral blood lymphocytes. In conclusion, the data suggest that SPS-7 is not an immunosuppressant while induces anticancer effect against HRPC through inhibition of Akt/mTOR/p70S6K pathwaysthat down-regulate protein levels of both c-Myc and cyclin D1, leading to G1 arrest of cell cycle and subsequent apoptosis. The data also indicate the potential of SPS-7 since PI3K/Akt signalingis responsive for the genomic alterations in prostate cancer.

New extracellular factors in glioblastoma multiforme development: neurotensin, growth differentiation factor-15, sphingosine-1-phosphate and cytomegalovirus infection

Recent years have seen considerable progress in understanding the biochemistry of cancer. For example, more significance is now assigned to the tumor microenvironment, especially with regard to intercellular signaling in the tumor niche which depends on many factors secreted by tumor cells. In addition, great progress has been made in understanding the influence of factors such as neurotensin, growth differentiation factor-15 (GDF-15), sphingosine-1-phosphate (S1P), and infection with cytomegalovirus (CMV) on the 'hallmarks of cancer' in glioblastoma multiforme. Therefore, in the present work we describe the influence of these factors on the proliferation and apoptosis of neoplastic cells, cancer stem cells, angiogenesis, migration and invasion, and cancer immune evasion in a glioblastoma multiforme tumor. In particular, we discuss the effect of neurotensin, GDF-15, S1P (including the drug FTY720), and infection with CMV on tumor-associated macrophages (TAM), microglial cells, neutrophil and regulatory T cells (T_reg), on the tumor microenvironment. In order to better understand the role of the aforementioned factors in tumoral processes, we outline the latest models of intratumoral heterogeneity in glioblastoma multiforme. Based on the most recent reports, we discuss the problems of multi-drug therapy in treating glioblastoma multiforme.

Signaling pathway involved in the inhibitory effect of FTY720P on the Na+/K+ ATPase in HepG2 cells

The Na+/K+ ATPase modulates the activity of many transporters in the liver, and maintains the ionic constancy of the intracellular milieu, preserving thus normal functioning of hepatocytes. Previous work showed that FTY720P, a sphingosine one phosphate receptor agonist used in the treatment of multiple sclerosis, exerts in HepG2 cells, an inhibitory effect on the activity of the ATPase, mediated via PGE2. This study is an attempt to identify the signaling molecules involved downstream of the prostaglandin. The activity of the ATPase was assayed by measuring the amount of inorganic phosphate liberated in presence and absence of ouabain, a specific inhibitor of the enzyme. The effect of FTY720P and PGE2 disappeared completely in presence of PF-04418948, a blocker of EP2 receptors, RpcAMP, an inhibitor of PKA, PD98059, an inhibitor of ERK, as well as in presence of PTIO, a nitric oxide synthase inhibitor, but was mimicked by butaprost, an EP2 agonist, dbcAMP, a cell permeable cAMP analogue, and SNAP1,a nitric oxide generator. PGE2 and dbcAMP increased the expression of phosphorylated ERK but not total ERK. This increase did not appear however in presence of PTIO, indicating that PKA is upstream of NO. It was concluded that FTY 720P induces PGE2 release which activates NOS leading to NO production and ERK activation. ERK then inhibits directly or indirectly the Na+/K+ ATPase.

A genome-wide screen for FTY720-sensitive mutants reveals genes required for ROS homeostasis

Fingolimod hydrochloride (FTY720), a sphingosine-1-phosphate (S1P) analogue, is an approved immune modulator for the treatment of multiple sclerosis (MS). Notably, in addition to its well-known mode of action as an S1P modulator, accumulating evidence suggests that FTY720 induces apoptosis in various cancer cells via reactive oxygen species (ROS) generation. Although the involvement of multiple signaling molecules, such as JNK (Jun N-terminal kinase), Akt (alpha serine/threonine-protein kinase) and Sphk has been reported, the exact mechanisms how FTY720 induces cell growth inhibition and the functional relationship between FTY720 and these signaling pathways remain elusive. Our previous reports using the fission yeast Schizosaccharomyces pombe as a model system to elucidate FTY720-mediated signaling pathways revealed that FTY720 induces an increase in intracellular Ca²⁺ concentrations and ROS generation, which resulted in the activation of the transcriptional responses downstream of Ca²⁺/calcineurin signaling and stress-activated MAPK signaling, respectively. Here, we performed a genome-wide screening for genes whose deletion induces FTY720-sensitive growth in S. pombe and identified 49 genes. These gene products are related to the biological processes involved in metabolic processes, transport, transcription, translation, chromatin organization, cytoskeleton organization and intracellular signal transduction. Notably, most of the FTY720-sensitive deletion cells exhibited NAC-remedial FTY720 sensitivities and dysregulated ROS homeostasis. Our results revealed a novel gene network involving ROS homeostasis and the possible mechanisms of the FTY720 toxicity.

A novel intracellular pH-responsive formulation for FTY720 based on PEGylated graphene oxide nano-sheets

OBJECTIVE

This study was performed to investigate a novel pH-responsive nanocarrier based on modified nano graphene oxide (nGO) to promote the acid-triggered intracellular release of a poorly soluble drug, FTY720.

METHODS

To synthesize a drug conjugated to modified nGO, first the polyethylene glycol (PEG) was conjugated to nGO, then the produced PEG-nGO was functionalized with the anticancer drug, FTY720, through amide bonding. It was characterized by the scanning electron microscopy (SEM), the atomic force microscopy (AFM), the Fourier transform infrared (FTIR) spectroscopy and the UV-vis spectroscopy. In vitro drug release of the FTY720-conjugated PEG-nGO was evaluated at pH 7.4 and 4.6 PBS at 37 °C. Furthermore, the antineoplastic action of unloaded and drug-loaded carrier against the human breast adenocarcinoma cell line MCF7 was explored using MTT and BrdU assays.

RESULTS

Characterization methods indicated successful drug deposition on the surface of nGO. In vitro, drug release results revealed a significantly faster release of FTY720 from PEG-nGO at acidic pH, compared with physiological pH. The proliferation assays proved that the unloaded nGO had no significant cytotoxicity against MCF7 cells, while free FTY720- and FTY720-loaded PEG-nGO had an approximately equal cytotoxic effect on the MCF7 cells. It was found that the extended release characteristic of FTY720 was well fitted to Korsmeyer-Peppas model and the release profile of FTY720 from PEG-nGO is diffusion controlled.

CONCLUSION

PEGylated GO can act as a pH-responsive drug carrier to improve the efficacy of anticancer drug delivery.

FTY720 Induces Autophagy-Associated Apoptosis in Human Oral Squamous Carcinoma Cells, in Part, through a Reactive Oxygen Species/Mcl-1-Dependent Mechanism

In this study, we interrogated the mechanism by which the immunosuppressant FTY720 mediates anticancer effects in oral squamous cell carcinoma (OSCC) cells. FTY720 differentially suppressed the viability of the OSCC cell lines SCC4, SCC25, and SCC2095 with IC₅₀ values of 6.1, 6.3, and 4.5 μM, respectively. This antiproliferative effect was attributable to the ability of FTY720 to induce caspase-dependent apoptosis. Mechanistic evidence suggests that FTY720-induced apoptosis was associated with its ability to inhibit Akt-NF-κB signaling, to facilitate the proteasomal degradation of the antiapoptotic protein Mcl-1, and to increase reactive oxygen species (ROS) generation. Both overexpression of Mcl-1 and inhibition of ROS partially protected cells from FTY720-induced caspase-9 activation, PARP cleavage and cytotoxicity. In addition, FTY720 induced autophagy in OSCC cells, as manifested by LC3B-II conversion, decreased p62 expression, and accumulation of autophagosomes. Inhibition of autophagy by bafilomycin A1 protected cells from FTY720-induced apoptosis. Together, these findings suggest an intricate interplay between autophagy and apoptosis in mediating the tumor-suppressive effect in OSCC cells, which underlies the translational potential of FTY720 in fostering new therapeutic strategies for OSCC.

Sphingosine-1-Phosphate Receptor-1 Promotes Environment-Mediated and Acquired Chemoresistance

Drug resistance is a major barrier for the development of effective and durable cancer therapies. Overcoming this challenge requires further defining the cellular and molecular mechanisms underlying drug resistance, both acquired and environment-mediated drug resistance (EMDR). Here, using neuroblastoma (NB), a childhood cancer with high incidence of recurrence due to resistance to chemotherapy, as a model we show that human bone marrow-mesenchymal stromal cells induce tumor expression of sphingosine-1-phosphate receptor-1 (S1PR1), leading to their resistance to chemotherapy. Targeting S1PR1 by shRNA markedly enhances etoposide-induced apoptosis in NB cells and abrogates EMDR, while overexpression of S1PR1 significantly protects NB cells from multidrug-induced apoptosis via activating JAK-STAT3 signaling. Elevated S1PR1 expression and STAT3 activation are also observed in human NB cells with acquired resistance to etoposide. We show in vitro and in human NB xenograft models that treatment with FTY720, an FDA-approved drug and antagonist of S1PR1, dramatically sensitizes drug-resistant cells to etoposide. In summary, we identify S1PR1 as a critical target for reducing both EMDR and acquired chemoresistance in NB. Mol Cancer Ther; 16(11); 2516-27. ©2017 AACR.

Methods for Testing Immunological Factors

Hypersensitivity reactions can be elicited by various factors: either immunologically induced, i.e., allergic reactions to natural or synthetic compounds mediated by IgE, or non-immunologically induced, i.e., activation of mediator release from cells through direct contact, without the induction of, or the mediation through immune responses. Mediators responsible for hypersensitivity reactions are released from mast cells. An important preformed mediator of allergic reactions found in these cells is histamine. Specific allergens or the calcium ionophore 48/80 induce release of histamine from mast cells. The histamine concentration can be determined with the o-phthalaldehyde reaction.

Development of novel PP2A activators for use in the treatment of acute myeloid leukaemia

The synthesis and biological evaluation of new cytotoxic analogs of AAL(S) are reported. Our findings identify key structural motifs required for anti-cancer effects.

Macrolactone Nuiapolide, Isolated from a Hawaiian Marine Cyanobacterium, Exhibits Anti-Chemotactic Activity

A new bioactive macrolactone, nuiapolide (1) was identified from a marine cyanobacterium collected off the coast of Niihau, near Lehua Rock. The natural product exhibits anti-chemotactic activity at concentrations as low as 1.3 μM against Jurkat cells, cancerous T lymphocytes, and induces a G2/M phase cell cycle shift. Structural characterization of the natural product revealed the compound to be a 40-membered macrolactone with nine hydroxyl functional groups and a rare tert-butyl carbinol residue.

The antineoplastic properties of FTY720: evidence for the repurposing of fingolimod

Almost all drugs approved for use in humans possess potentially beneficial 'off-target' effects in addition to their principal activity. In some cases this has allowed for the relatively rapid repurposing of drugs for other indications. In this review we focus on the potential for re-purposing FTY720 (also known as fingolimod, Gilenya(™)), an immunomodulatory drug recently approved for the treatment of multiple sclerosis (MS). The therapeutic benefit of FTY720 in MS is largely attributed to the immunosuppressive effects that result from its modulation of sphingosine 1-phosphate receptor signalling. However, this drug has also been shown to inhibit other cancer-associated signal transduction pathways in part because of its structural similarity to sphingosine, and consequently shows efficacy as an anti-cancer agent both in vitro and in vivo. Here, we review the effects of FTY720 on signal transduction pathways and cancer-related cellular processes, and discuss its potential use as an anti-cancer drug.

Association of Sphingosine-1-phosphate (S1P)/S1P Receptor-1 Pathway with Cell Proliferation and Survival in Canine Hemangiosarcoma

Background

Sphingosine‐1‐phosphate (S1P) is a key biolipid signaling molecule that regulates cell growth and survival, but it has not been studied in tumors from dogs.

Hypothesis/Objectives

S1P/S1P₁ signaling will contribute to the progression of hemangiosarcoma (HSA).

Animals

Thirteen spontaneous HSA tissues, 9 HSA cell lines, 8 nonmalignant tissues, including 6 splenic hematomas and 2 livers with vacuolar degeneration, and 1 endothelial cell line derived from a dog with splenic hematoma were used.

Methods

This was a retrospective case series and in vitro study. Samples were obtained as part of medically necessary diagnostic procedures. Microarray, qRT‐PCR, immunohistochemistry, and immunoblotting were performed to examine S1P₁ expression. S1P concentrations were measured by high‐performance liquid chromatography/mass spectrometry. S1P signaling was evaluated by intracellular Ca²⁺ mobilization; proliferation and survival were evaluated using the MTS assay and Annexin V staining.

Results

Canine HSA cells expressed higher levels of S1P₁mRNA than nonmalignant endothelial cells. S1P₁ protein was present in HSA tissues and cell lines. HSA cells appeared to produce low levels of S1P, but they selectively consumed S1P from the culture media. Exogenous S1P induced an increase in intracellular calcium as well as increased proliferation and viability of HSA cells. Prolonged treatment with FTY720, an inhibitor of S1P₁, decreased S1P₁ protein expression and induced apoptosis of HSA cells.

Conclusions and clinical importance

S1P/S1P₁ signaling pathway functions to maintain HSA cell viability and proliferation. The data suggest that S1P₁ or the S1P pathway in general could be targets for therapeutic intervention for dogs with HSA.

Traumatic Brain Injury-Induced Neuronal Apoptosis is Reduced Through Modulation of PI3K and Autophagy Pathways in Mouse by FTY720

FTY720 is a synthetic compound produced by modification of metabolite from Isaria sinclairii. It is a novel type of immunosuppressive agent inhibiting lymphocyte egress from secondary lymphoid tissues, thereby causing peripheral lymphopenia. Growing evidences have suggested that apoptosis and autophagy were involved in the secondary brain injury after traumatic brain injury (TBI) although FTY720 exerted neuroprotective effects in a variety of neurological diseases except TBI. The present study was aimed to investigate the role of FTY720 in a mouse model of TBI. In experiment 1, ICR mice were divided into four groups: sham group, TBI group, TBI + vehicle group, and TBI + FTY720 group. And the injured cerebral cortex (including both contused and penumbra) was used for analysis. We found that FTY720 administration after TBI improved neurobehavioral function, alleviated brain edema, accompanied by modulation of apoptotic indicators such as Bcl-2, Bcl-xL, Bax, and cytochrome c. In experiment 2, ICR mice were also divided into four groups: sham group, TBI + vehicle group, TBI + FTY720 group, and TBI + FTY720 + inhibitors group. And the injured cerebral cortex (including both contused and penumbra) was used for analysis. We found that FTY720 increased the expression of phospho-protein kinase B (AKT) and some autophagy markers such as LC3 and Beclin 1. In addition, the apoptosis inhibition effect of FTY720 was partly abrogated by the phosphatidylinositide 3-kinases (PI3K)/AKT pathway inhibitor LY294002 and autophagy inhibitor 3-methyladenine. Collectively, our data provide the first evidence that FTY720 exerted neuroprotective effects after TBI, at least in part, through the activation of PI3K/AKT pathway and autophagy.

The phosphorylated prodrug FTY720 is a histone deacetylase inhibitor that reactivates ERα expression and enhances hormonal therapy for breast cancer

Estrogen receptor-α (ERα)-negative breast cancer is clinically aggressive and does not respond to conventional hormonal therapies. Strategies that lead to re-expression of ERα could sensitize ERα-negative breast cancers to selective ER modulators. FTY720 (fingolimod, Gilenya), a sphingosine analog, is the Food and Drug Administration (FDA)-approved prodrug for treatment of multiple sclerosis that also has anticancer actions that are not yet well understood. We found that FTY720 is phosphorylated in breast cancer cells by nuclear sphingosine kinase 2 and accumulates there. Nuclear FTY720-P is a potent inhibitor of class I histone deacetylases (HDACs) that enhances histone acetylations and regulates expression of a restricted set of genes independently of its known effects on canonical signaling through sphingosine-1-phosphate receptors. High-fat diet (HFD) and obesity, which is now endemic, increase breast cancer risk and have been associated with worse prognosis. HFD accelerated the onset of tumors with more advanced lesions and increased triple-negative spontaneous breast tumors and HDAC activity in MMTV-PyMT transgenic mice. Oral administration of clinically relevant doses of FTY720 suppressed development, progression and aggressiveness of spontaneous breast tumors in these mice, reduced HDAC activity and strikingly reversed HFD-induced loss of estrogen and progesterone receptors in advanced carcinoma. In ERα-negative human and murine breast cancer cells, FTY720 reactivated expression of silenced ERα and sensitized them to tamoxifen. Moreover, treatment with FTY720 also re-expressed ERα and increased therapeutic sensitivity of ERα-negative syngeneic breast tumors to tamoxifen in vivo more potently than a known HDAC inhibitor. Our work suggests that a multipronged attack with FTY720 is a novel combination approach for effective treatment of both conventional hormonal therapy-resistant breast cancer and triple-negative breast cancer.

FTY720 induces autophagy-related apoptosis and necroptosis in human glioblastoma cells

FTY720 is a potent immunosuppressant which has preclinical antitumor efficacy in various cancer models. However, its role in glioblastoma remains unclear. In the present study, we found that FTY720 induced extrinsic apoptosis, necroptosis and autophagy in human glioblastoma cells. Inhibition of autophagy by either RNA interference or chemical inhibitors attenuated FTY720-induced apoptosis and necrosis. Furthermore, autophagy, apoptosis and necrosis induction were dependent on reactive oxygen species-c-Jun N-terminal kinase-protein 53 (ROS-JNK-p53) loop mediated phosphatidylinositide 3-kinases/protein kinase B/mammalian target of rapamycin/p70S6 kinase (PI3K/AKT/mTOR/p70S6K) pathway. In addition, receptor-interacting protein 1 and 3 (RIP1 and RIP3) served as an upstream of ROS-JNK-p53 loop. However, the phosphorylation form of FTY720 induced autophagy but not apoptosis and necroptosis. Finally, the in vitro results were validated in vivo in xenograft mouse of glioblastoma cells. In conclusion, the current study provided novel insights into understanding the mechanisms and functions of FTY720-induced apoptosis, necroptosis and autophagy in human glioblastoma cells.

Involvement of vacuolar H(+)-ATPase in killing of human melanoma cells by the sphingosine kinase analogue FTY720

Targeting the sphingosine 1-phosphate (S1P)/S1P receptor (S1PR) signalling axis is emerging as a promising strategy in the treatment of cancer. However, the effect of such an approach on survival of human melanoma cells remains less understood. Here, we show that the sphingosine analogue FTY720 that functionally antagonises S1PRs kills human melanoma cells through a mechanism involving the vacuolar H(+) -ATPase activity. Moreover, we demonstrate that FTY720-triggered cell death is characterized by features of necrosis and is not dependent on receptor-interacting protein kinase 1 or lysosome cathepsins, nor was it associated with the activation of protein phosphatase 2A. Instead, it is mediated by increased production of reactive oxygen species and is antagonized by activation of autophagy. Collectively, these results suggest that FTY720 and its analogues are promising candidates for further development as new therapeutic agents in the treatment of melanoma.

Deregulation of the PP2A inhibitor SET shows promising therapeutic implications and determines poor clinical outcome in patients with metastatic colorectal cancer

PURPOSE

SET is an endogenous PP2A inhibitor that might represent a novel molecular target for antitumor therapy. The aim of this study was to evaluate the molecular effects of SET deregulation and its potential clinical significance in metastatic colorectal cancer (mCRC).

EXPERIMENTAL DESIGN

We studied the biologic effects of SET on cell growth, colonosphere formation, caspase activity, PP2A activation status, and sensitivity to oxaliplatin and FTY720 treatments. Moreover, we analyzed SET expression by immunostaining in 242 patients with mCRC.

RESULTS

SET deregulation promotes cell growth and colonosphere formation and inhibits PP2A, thereby impairing its antitumor effects. Moreover, SET reduces sensitivity to oxaliplatin in colorectal cancer cell lines, which is restored after FTY720 treatment. SET overexpression was detected in 24.8% (60 of 242) of patients with mCRC and determined significantly shorter overall (8.6 vs. 27 months; P < 0.001) and progression-free survival (7.1 vs. 13.7 months; P < 0.001), and poor response to oxaliplatin-based chemotherapy (P = 0.004). Interestingly, its prognostic value was particularly evident in patients younger than 70 years and in those harboring KRAS mutations.

CONCLUSIONS

SET overexpression is a frequent event in mCRC that plays a potential oncogenic role associated with worse outcome and resistance to oxaliplatin. Moreover, this alteration defines a subgroup of patients who could benefit from therapies containing PP2A activators such as FTY720.

Fingolimod for the treatment of neurological diseases-state of play and future perspectives

Sphingolipids are a fascinating class of signaling molecules derived from the membrane lipid sphingomyelin. They show abundant expression in the brain. Complex sphingolipids such as glycosphingolipids (gangliosides and cerebrosides) regulate vesicular transport and lysosomal degradation and their dysregulation can lead to storage diseases with a neurological phenotype. More recently, simple sphingolipids such ceramide, sphingosine and sphingosine 1-phosphate (S1P) were discovered to signal in response to many extracellular stimuli. Forming an intricate signaling network, the balance of these readily interchangeable mediators is decisive for cell fate under stressful conditions. The immunomodulator fingolimod is the prodrug of an S1P receptor agonist. Following receptor activation, the drug leads to downregulation of the S1P₁ receptor inducing functional antagonism. As the first drug to modulate the sphingolipid signaling pathway, it was marketed in 2010 for the treatment of multiple sclerosis (MS). At that time, immunomodulation was widely accepted as the key mechanism of fingolimod’s efficacy in MS. But given the excellent passage of this lipophilic compound into the brain and its massive brain accumulation as well as the abundant expression of S1P receptors on brain cells, it is conceivable that fingolimod also affects brain cells directly. Indeed, a seminal study showed that the protective effect of fingolimod in experimental autoimmune encephalitis (EAE), a murine MS model, is lost in mice lacking the S1P₁ receptor on astrocytes, arguing for a specific role of astrocytic S1P signaling in MS. In this review, we discuss the role of sphingolipid mediators and their metabolizing enzymes in neurologic diseases and putative therapeutic strategies arising thereof.

Advances in the management of peritoneal mesothelioma

Malignant peritoneal mesothelioma (PM) is an infrequent disease which has historically been associated with a poor prognosis. Given its long latency period and non-specific symptomatology, a diagnosis of PM can be suggested by occupational exposure history, but ultimately relies heavily on imaging and diagnostic biopsy. Early treatment options including palliative operative debulking, intraperitoneal chemotherapy, and systemic chemotherapy have marginally improved the natural course of the disease with median survival being approximately one year. The advent of cytoreduction (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) has dramatically improved survival outcomes with wide median survival estimates between 2.5 to 9 years; these studies however remain largely heterogeneous, with differing study populations, tumor biology, and specific treatment regimens. More recent investigations have explored extent of cytoreduction, repeated operative intervention, and choice of chemotherapy but have been unable to offer definitive conclusions. CRS and HIPEC remain morbid procedures with complication rates ranging between 30% to 46% in larger series. Accordingly, an increasing interest in identifying molecular targets and developing targeted therapies is emerging. Among such novel targets is sphingosine kinase 1 (SphK1) which regulates the production of sphingosine-1-phosphate, a biologically active lipid implicated in various cancers including malignant mesothelioma. The known action of specific SphK inhibitors may warrant further exploration in peritoneal disease.

FTY720 reduces migration and invasion of human glioblastoma cell lines via inhibiting the PI3K/AKT/mTOR/p70S6K signaling pathway

2-Amino-2-[2-(4-octylphenyl)]-1,3-propanediol hydrochloride (FTY720), a synthetic compound from Isaria sinclairii, has been proven to possess various biological benefits including anti-cancer activity. However, the effects and related mechanisms of FTY720 on the migration and invasion of glioblastoma cells are still unclear. In the present study, we utilized U251MG and U87MG human glioblastoma cell lines to assess the effects of FTY720. We found that FTY720 significantly inhibited migration and invasion of glioblastoma cells. The anti-migration and invasion effects of FTY720 were associated with its down-regulation of matrix metalloproteinase-2 (MMP-2) and MMP-9 while up-regulation of tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2. Furthermore, FTY720 modulated the expression of roundabouts 1 (ROBO1), Rho-associated kinase-1 (ROCK1), and epithelial-to-mesenchymal transition (EMT)-related factors. In addition, the phosphatidylinositide 3-kinases/protein kinase B/mammalian target of rapamycin/p70S6 kinase (PI3K/AKT/mTOR/p70S6K) signaling pathway participated in FTY720-mediated suppression of migration and invasion. Thus, our findings demonstrated that FTY720 reduced glioblastoma cells migration and invasion via multiple signaling pathways, suggesting that FTY720 is a potential therapeutic agent against glioblastoma.

Mollugin induces tumor cell apoptosis and autophagy via the PI3K/AKT/mTOR/p70S6K and ERK signaling pathways

Mollugin, a bioactive phytochemical isolated from Rubia cordifolia L., has shown preclinical anticancer efficacy in various cancer models. However the effects of mollugin in regulating cancer cell survival and death remains undefined. In the present study we found that mollugin exhibited cytotoxicity on various cancer models. The suppression of cell viability was due to the induction of mitochondria apoptosis. In addition, the presence of autophagic hallmarks was observed in mollugin-treated cells. Notably, blockade of autophagy by a chemical inhibitor or RNA interference enhanced the cytotoxicity of mollugin. Further experiments demonstrated that phosphatidylinositide 3-kinases/protein kinase B/mammalian target of rapamycin/p70S6 kinase (PI3K/AKT/mTOR/p70S6K) and extracellular regulated protein kinases (ERK) signaling pathways participated in mollugin-induced autophagy and apoptosis. Together, these findings support further studies of mollugin as candidate for treatment of human cancer cells.

Inhibition of cathepsin S induces autophagy and apoptosis in human glioblastoma cell lines through ROS-mediated PI3K/AKT/mTOR/p70S6K and JNK signaling pathways

Cathepsin S is a lysosomal cysteine protease that is overexpressed in various cancer models and plays important role in tumorigenesis, however the mechanisms are unclear. In the present study, we found that inhibition of cathepsin S induced autophagy and mitochondrial apoptosis in human glioblastoma cells. Blockade of autophagy by either a chemical inhibitor or RNA interference attenuated cathespin S inhibition-induced apoptosis. Furthermore, autophagy and apoptosis induction was dependent on the suppression of phosphatidylinositide 3-kinases/protein kinase B/mammalian target of rapamycin/p70S6 kinase (PI3K/AKT/mTOR/p70S6K) signaling pathway and activation of c-Jun N-terminal kinase (JNK) signaling pathway. In addition, reactive oxygen species (ROS) served as an upstream of PI3K/AKT/mTOR/p70S6K and JNK signaling pathways. In conclusion, the current study revealed that cathepsin S played an important role in the regulation of autophagy and apoptosis in human glioblastoma cells.

Importance of sphingosine kinase (SphK) as a target in developing cancer therapeutics and recent developments in the synthesis of novel SphK inhibitors

Sphingosine kinase (SphK) is an oncogenic lipid kinase that regulates the sphingolipid metabolic pathway that has been shown to play a role in numerous hyperproliferative/inflammatory diseases. The SphK isoforms (SphK1 and SphK2) catalyze the conversion of the proapoptotic substrate d-erythrosphingosine to the promitogenic/migratory product sphingosine 1-phosphate (S1P). Accumulation of S1P has been linked to the development/progression of cancer and various other diseases including, but not limited to, asthma, inflammatory bowel disease, rheumatoid arthritis, and diabetic nephropathy. SphK therefore represents a potential new target for developing novel therapeutics for cancer and other diseases. This finding has stimulated the development and evaluation of numerous SphK inhibitors over the past decade or so. In this review, we highlight the recent advancement in the field of SphK inhibitors including SphK1 and SphK2 specific inhibitors. Both sphingolipid based and nolipidic small molecule inhibitors and their importance in treatment of cancer and other diseases are discussed.