FTY720, a synthetic compound from Isaria sinclairii, inhibits proliferation and induces apoptosis in pancreatic cancer cells

Sphingosine-1-Phosphate Inhibition Increases Endoplasmic Reticulum Stress to Enhance Oxaliplatin Sensitivity in Pancreatic Cancer

Background

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer resistant to current therapies, including oxaliplatin (Oxa). Growing evidence supports the ability of cancers to harness sphingolipid metabolism for survival. Sphingosine-1-phosphate (S1P) is an anti-apoptotic, pro-survival mediator that can influence cellular functions such as endoplasmic reticulum (ER) stress. We hypothesize that PDAC drives dysregulated sphingolipid metabolism and that S1P inhibition can enhance ER stress to improve therapeutic response to Oxa in PDAC.

Methods

RNA sequencing data of sphingolipid mediators from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression Project (GTEx) datasets were analyzed. Murine and human PDAC cell lines were treated with small interfering RNA (siRNA) against sphingosine kinase-2 (SPHK2) or ABC294640 (ABC) and incubated with combinations of vehicle control or Oxa. In an orthotopic syngeneic KPC PDAC model, tumors were treated with either vehicle control, Oxa, ABC, or combination therapy.

Results

RNA sequencing analysis revealed multiple significantly differentially expressed sphingolipid mediators (P < 0.05). In vitro, both siRNA knockdown of SPHK2 and ABC sensitized cells to Oxa therapy (P < 0.05), and induced eukaryotic initiation factor 2α (eIF2α) and protein kinase RNA-like endoplasmic reticulum kinase (PERK) phosphorylation, hallmarks of ER stress. In vitro therapy also increased extracellular high mobility group box 1 (HMGB1) release (P < 0.05), necessary for immunogenic cell death (ICD). In vivo combination therapy increased apoptotic markers as well as the intensity of HMGB1 staining compared to control (P < 0.05).

Conclusions

Our evidence suggests that sphingolipid metabolism is dysregulated in PDAC. Furthermore, S1P inhibition can sensitize PDAC to Oxa therapy through increasing ER stress and can potentiate ICD induction. This highlights a potential therapeutic target for chemosensitizing PDAC as well as an adjunct for future chemoimmunotherapy strategies.

Simultaneous targeting of mitochondrial Kv1.3 and lysosomal acid sphingomyelinase amplifies killing of pancreatic ductal adenocarcinoma cells in vitro and in vivo

Pancreas ductal adenocarcinoma (PDAC) remains a malignant tumor with very poor prognosis and low 5-year overall survival. Here, we aimed to simultaneously target mitochondria and lysosomes as a new treatment paradigm of malignant pancreas cancer in vitro and in vivo. We demonstrate that the clinically used sphingosine analog FTY-720 together with PAPTP, an inhibitor of mitochondrial Kv1.3, induce death of pancreas cancer cells in vitro and in vivo. The combination of both drugs results in a marked inhibition of the acid sphingomyelinase and accumulation of cellular sphingomyelin in vitro and in vivo in orthotopic and flank pancreas cancers. Mechanistically, PAPTP and FTY-720 cause a disruption of both mitochondria and lysosomes, an alteration of mitochondrial bioenergetics and accumulation of cytoplasmic Ca²⁺, events that collectively mediate cell death. Our findings point to an unexpected cross-talk between lysosomes and mitochondria mediated by sphingolipid metabolism. We show that the combination of PAPTP and FTY-720 induces massive death of pancreas cancer cells, thereby leading to a substantially delayed and reduced PDAC growth in vivo. KEY MESSAGES: FTY-720 inhibits acid sphingomyelinase in pancreas cancer cells (PDAC). FTY-720 induces sphingomyelin accumulation and lysosomal dysfunction. The mitochondrial Kv1.3 inhibitor PAPTP disrupts mitochondrial functions. PAPTP and FTY-720 synergistically kill PDAC in vitro. The combination of FTY-720 and PAPTP greatly delays PDAC growth in vivo.

Transcriptomic Analysis Insight into the Immune Modulation during the Interaction of Ophiocordyceps sinensis and Hepialus xiaojinensis

Ophiocordyceps sinensis (Berk.) is an entomopathogenic fungus that can infect the larva of the ghost moth, Hepialus xiaojinensis, causing mummification after more than one year. This prolonged infection provides a valuable model for studying the immunological interplay between an insect host and a pathogenic fungus. A comparative transcriptome analysis of pre-infection (L) and one-year post-infection (IL) larvae was performed to investigate the immune response in the host. Here, a total of 59,668 unigenes were obtained using Illumina Sequencing in IL and L. Among the 345 identified immune-related genes, 83 out of 86 immune-related differentially expressed genes (DEGs) had a much higher expression in IL than in L. Furthermore, the immune-related DEGs were classified as pathogen recognition receptors (PRRs), signal modulators or transductors, and immune effector molecules. Serpins and protease inhibitors were found to be upregulated in the late phase of infection, suppressing the host’s immune response. Based on the above analysis, the expression levels of most immune-related genes would return to the baseline with the immune response being repressed in the late phase of infection, leading to the fungal immunological tolerance after prolonged infection. Meanwhile, the transcriptomes of IL and the mummified larva (ML) were compared to explore O. sinensis invasion. A total of 1408 novel genes were identified, with 162 of them annotated with putative functions. The gene families likely implicated in O. sinensis pathogenicity have been identified, primarily including serine carboxypeptidase, peroxidase, metalloprotease peptidase, aminopeptidases, cytochrome P450, and oxidoreductase. Furthermore, quantitative real-time PCR (qPCR) was used to assess the expression levels of some critical genes that were involved in immune response and fungal pathogenicity. The results showed that their expression levels were consistent with the transcriptomes. Taken together, our findings offered a comprehensive and precise transcriptome study to understand the immune defense in H. xiaojinensis and O. sinensis invasion, which would accelerate the large-scale artificial cultivation of this medicinal fungus.

Molecular Classification of Genes Associated with Hypoxic Lipid Metabolism in Pancreatic Cancer

Abnormal lipid metabolism often occurs under hypoxic microenvironment, which is an important energy supplement for cancer cell proliferation and metastasis. We aimed to explore the lipid metabolism characteristics and gene expression features of pancreatic ductal adenocarcinoma (PDAC) related to hypoxia and identify biomarkers for molecular classification based on hypoxic lipid metabolism that are evaluable for PDAC prognosis and therapy. The multiple datasets were analyzed integratively, including corresponding clinical information of samples. PDAC possesses a distinct metabolic profile and oxygen level compared with normal pancreatic tissues, according to the bioinformatics methods. In addition, a study on untargeted metabolomics using Ultra Performance Liquid Chromatography Tandem Mass Spectrometry(UPLC-MS) revealed lipid metabolites differences affected by oxygen. Analysis of PDAC gene expression profiling in The Cancer Genome Atlas (TCGA) revealed that the sphingolipid process correlates closely with HIF1α. According to the characters of HIF-1 and sphingolipid, samples can be clustered into three subgroups using non-negative matrix factorization clustering. In cluster2, patients had an increased survival time. Relatively high MUC16 mutation arises in cluster2 and may positively influence the cancer survival rates. This study explored the expression pattern of lipid metabolism under hypoxia microenvironment in PDAC. On the basis of metabolic signatures, we identified the prognosis subtypes linking lipid metabolism to hypoxia. The classifications may be conducive to developing personalized treatment programs targeting metabolic profiles.

Molecular Pharmacology and Novel Potential Therapeutic Applications of Fingolimod

Fingolimod is a well-tolerated, highly effective disease-modifying therapy successfully utilized in the management of multiple sclerosis. The active metabolite, fingolimod-phosphate, acts on sphingosine-1-phosphate receptors (S1PRs) to bring about an array of pharmacological effects. While being initially recognized as a novel agent that can profoundly reduce T-cell numbers in circulation and the CNS, thereby suppressing inflammation and MS, there is now rapidly increasing knowledge on its previously unrecognized molecular and potential therapeutic effects in diverse pathological conditions. In addition to exerting inhibitory effects on sphingolipid pathway enzymes, fingolimod also inhibits histone deacetylases, transient receptor potential cation channel subfamily M member 7 (TRMP7), cytosolic phospholipase A2α (cPLA2α), reduces lysophosphatidic acid (LPA) plasma levels, and activates protein phosphatase 2A (PP2A). Furthermore, fingolimod induces apoptosis, autophagy, cell cycle arrest, epigenetic regulations, macrophages M1/M2 shift and enhances BDNF expression. According to recent evidence, fingolimod modulates a range of other molecular pathways deeply rooted in disease initiation or progression. Experimental reports have firmly associated the drug with potentially beneficial therapeutic effects in immunomodulatory diseases, CNS injuries, and diseases including Alzheimer's disease (AD), Parkinson's disease (PD), epilepsy, and even cancer. Attractive pharmacological effects, relative safety, favorable pharmacokinetics, and positive experimental data have collectively led to its testing in clinical trials. Based on the recent reports, fingolimod may soon find its way as an adjunct therapy in various disparate pathological conditions. This review summarizes the up-to-date knowledge about molecular pharmacology and potential therapeutic uses of fingolimod.

Modulators of TRPM7 and its potential as a drug target for brain tumours

TRPM7 is a non-selective divalent cation channel with an alpha-kinase domain. Corresponding with its broad expression, TRPM7 has a role in a wide range of cell functions, including proliferation, migration, and survival. Growing evidence shows that TRPM7 is also aberrantly expressed in various cancers, including brain cancers. Because ion channels have widespread tissue distribution and result in extensive physiological consequences when dysfunctional, these proteins can be compelling drug targets. In fact, ion channels comprise the third-largest drug target type, following enzymes and receptors. Literature has shown that suppression of TRPM7 results in inhibition of migration, invasion, and proliferation in several human brain tumours. Therefore, TRPM7 presents a potential target for therapeutic brain tumour interventions. This article reviews current literature on TRPM7 as a potential drug target in the context of brain tumours and provides an overview of various selective and non-selective modulators of the channel relevant to pharmacology, oncology, and ion channel function.

Targeting Sphingolipids for Cancer Therapy

Sphingolipids are an extensive class of lipids with different functions in the cell, ranging from proliferation to cell death. Sphingolipids are modified in multiple cancers and are responsible for tumor proliferation, progression, and metastasis. Several inhibitors or activators of sphingolipid signaling, such as fenretinide, safingol, ABC294640, ceramide nanoliposomes (CNLs), SKI-II, α-galactosylceramide, fingolimod, and sonepcizumab, have been described. The objective of this review was to analyze the results from preclinical and clinical trials of these drugs for the treatment of cancer. Sphingolipid-targeting drugs have been tested alone or in combination with chemotherapy, exhibiting antitumor activity alone and in synergism with chemotherapy in vitro and in vivo. As a consequence of treatments, the most frequent mechanism of cell death is apoptosis, followed by autophagy. Aslthough all these drugs have produced good results in preclinical studies of multiple cancers, the outcomes of clinical trials have not been similar. The most effective drugs are fenretinide and α-galactosylceramide (α-GalCer). In contrast, minor adverse effects restricted to a few subjects and hepatic toxicity have been observed in clinical trials of ABC294640 and safingol, respectively. In the case of CNLs, SKI-II, fingolimod and sonepcizumab there are some limitations and absence of enough clinical studies to demonstrate a benefit. The effectiveness or lack of a major therapeutic effect of sphingolipid modulation by some drugs as a cancer therapy and other aspects related to their mechanism of action are discussed in this review.

Strategies for Targeting Serine/Threonine Protein Phosphatases with Small Molecules in Cancer

Among numerous posttranslational regulation patterns, phosphorylation is reversibly controlled by the balance of kinases and phosphatases. The major form of cellular signaling involves the reversible phosphorylation of proteins on tyrosine, serine, or threonine residues. However, altered phosphorylation levels are found in diverse diseases, including cancer, making kinases and phosphatases ideal drug targets. In contrast to the success of prosperous kinase inhibitors, design of small molecules targeting phosphatase is struggling due to past bias and difficulty. This is especially true for serine/threonine phosphatases, one of the largest phosphatase families. From this perspective, we aim to provide insights into serine/threonine phosphatases and the small molecules targeting these proteins for drug development, especially in cancer. Through highlighting the modulation strategies, we aim to provide basic principles for the design of small molecules and future perspectives for the application of drugs targeting serine/threonine phosphatases.

Induction of Lysosomal Membrane Permeabilization Is a Major Event of FTY720-Mediated Non-Apoptotic Cell Death in Human Glioma Cells

Simple Summary

FTY720, a sphingosine-1-phosphate (S1P) analog, is a potent immunosuppressant for the treatment of multiple sclerosis. In addition to being an immune modulator, FTY720 also features antitumor activity in several cancer models, but the molecular mechanisms are unclear. Here, we extended our research to analyze the signaling pathways mediating FTY720-induced cell death. FTY720 did not induce apoptotic cell death, autophagy, paraptosis, or necroptosis in glioma cells. Interestingly, FTY720 accumulated in lysosomes, resulting in the induction of lysosomal membrane permeabilization (LMP). Inhibition of LMP by overexpression of HSP70 and cathepsin inhibitors blocked FTY720-induced cell death. These data suggest that FTY720 induces cell death induced by LMP in glioma cells.

Abstract

FTY720, a sphingosine-1-phosphate (S1P) receptor modulator, is a synthetic compound produced by the modification of a metabolite from I. sinclairii. Here, we found that FTY720 induced non-apoptotic cell death in human glioma cells (U251MG, U87MG, and U118MG). FTY720 (10 µM) dramatically induced cytoplasmic vacuolation in glioma cells. However, FTY720-mediated vacuolation and cell death are not associated with autophagy. Genetic or pharmacological inhibition of autophagy did not inhibit FTY720-induced cell death. Herein, we detected that FTY720-induced cytoplasmic vacuoles were stained with lysotracker red, and FTY720 induced lysosomal membrane permeabilization (LMP). Interestingly, cathepsin inhibitors (E64D and pepstatin A) and ectopic expression of heat shock protein 70 (HSP70), which is an endogenous inhibitor of LMP, markedly inhibited FTY720-induced cell death. Our results demonstrated that FTY720 induced non-apoptotic cell death via the induction of LMP in human glioma cells.

GPCRs in pancreatic adenocarcinoma: Contributors to tumour biology and novel therapeutic targets

Pancreatic cancer has one of the highest mortality rates (5-year survival ~9%) among cancers. Pancreatic adenocarcinoma (PAAD) is the most common (>80%) and the most lethal type of pancreatic cancer. A need exists for new approaches to treat pancreatic adenocarcinoma. GPCRs, the largest family of cell-surface receptors and drug targets, account for ~35% of approved drugs. Recent studies have revealed roles for GPCRs in PAAD cells and cells in the tumour micro-environment. This review assesses current information regarding GPCRs in PAAD by summarizing omics data for GPCRs expression in PAAD. The PAAD "GPCRome" includes GPCRs with approved agents, thereby offering potential for their repurposing/repositioning. We then reviewed the evidence for functional roles of specific GPCRs in PAAD. We also highlight gaps in understanding the contribution of GPCRs to PAAD biology and identify several GPCRs that may be novel therapeutic targets for future work in search of GPCR-targeted drugs to treat PAAD tumours.

Secondary metabolites (SMs) of Isaria cicadae and Isaria tenuipes

Both Isaria cicadae and Isaria tenuipes are important entomopathogenic fungi used in health foods and traditional herbal medicines in East Asia. However, the safety concerns for both fungal species have been attracting significant attention. Thus, surveying their secondary metabolites (SMs) will be beneficial to improving the safety of their fungal products. In the case of I. cicadae, its SMs mainly include nucleosides, amino acids, beauvericins, myriocin, and oosporein. In contrast, trichothecene derivatives, isariotins, cyclopenta benzopyrans and PKs, are found in the case of I. tenuipes. Among them, beauvericins, myriocin, oosporein and many trichothecene derivatives are toxic compounds. The toxicity and side effects of the fungal products may be related to these SMs. Thus, to ensure the safety of fungal products, the residues standards of SMs need to be reported. Furthermore, methods for the detection of their SMs and biological identification of their strains must be considered. This review gives new insight into the secondary metabolites of medical and edible fungi.

Investigation of PP2A and Its Endogenous Inhibitors in Neuroblastoma Cell Survival and Tumor Growth

High-risk neuroblastoma continues to carry a poor prognosis. Nearly 50% of these tumors relapse following extensive treatment regimens. Protein phosphatase 2A (PP2A), a tumor suppressor, has been shown to be downregulated in many human cancers via multiple mechanisms including upregulation of its endogenous inhibitors, I2PP2A or CIP2A. We hypothesized that inhibition of the endogenous PP2A inhibitors or activation of PP2A would decrease tumorigenicity in human neuroblastoma cells. Four human neuroblastoma cell lines were utilized. Expression of PP2A and its endogenous inhibitors I2PP2A and CIP2A was confirmed by immunoblotting. PP2A activation was measured via phosphatase activation assay. Multiple parallel methods including siRNA inhibition of the endogenous PP2A inhibitors and pharmacologic activation of PP2A were utilized. Cell viability, proliferation, migration, and invasion assays were performed. In vivo studies were utilized to determine the effects of PP2A activation on neuroblastoma tumor growth. Inhibition of the endogenous inhibitors of PP2A or pharmacologic activation of PP2A with the PP2A activator FTY720 led to decreased neuroblastoma cell viability, proliferation, migration, and invasion. Treatment of mice bearing SK-N-AS or SK-N-BE(2) neuroblastoma tumors with FTY720 resulted in a significant decrease in tumor growth compared to vehicle-treated animals. In conclusion, activation of PP2A may provide a novel therapeutic target for neuroblastoma.

Targeting S1PR1/STAT3 loop abrogates desmoplasia and chemosensitizes pancreatic cancer to gemcitabine

Rationale: Pancreatic cancer is associated with poor prognosis with a 5-year survival rate of less than 6%. Approximately 90% of pancreatic cancer patients harbor somatic mutations in the KRAS gene. Multiple lines of evidence suggest a persistent activation of STAT3 in KRAS-driven oncogenesis contributing to desmoplasia and gemcitabine resistance. Sphingosine 1-phosphate receptor 1 (S1PR1) is an integral component of tumor progression and maintains an activated state of STAT3. FTY720 is an approved drug for multiple sclerosis and acts as a functional antagonist for S1PR1. Here we explored the potential utility of FTY720 to target S1PR1/STAT3 and other major signaling pathways in pancreatic cancer, and sought proof-of-principle for repurposing FTY720 for the treatment of pancreatic cancer. Methods: We examined the activity of FTY720 in the proliferation, apoptosis, and cell cycle assays in human and mouse pancreatic cancer model systems. Further, we studied the efficacy of using a combination of FTY720 and gemcitabine as opposed to individual agents in vitro as well as in vivoResults: Treatment of human and mouse pancreatic cancer cells with FTY720 resulted in inhibition of growth, increased apoptosis, and cell cycle arrest. FTY720 in combination with gemcitabine breached the mitochondrial membrane potential, altered the S1PR1-STAT3 loop, and inhibited epithelial to mesenchymal (EMT) transition. Data from murine models exhibited a marked reduction in the tumor size, increased apoptosis, inhibited NF-κB, S1PR1/STAT3, Shh signaling and desmoplasia, modulated the expression of gemcitabine-metabolizing transport enzymes, and restored the expression of tumor suppressor gene PP2A. Conclusion: Taken together, our results established FTY720 as a propitious molecule, which increases the efficacy of gemcitabine and represents a promising agent in the management of pancreatic cancer.

FTY720 Decreases Tumorigenesis in Group 3 Medulloblastoma Patient-Derived Xenografts

Group 3 tumors account for 28% of medulloblastomas and have the worst prognosis. FTY720, an immunosuppressant currently approved for treatment of multiple sclerosis, has shown antitumor effects in several human cancer cell lines. We hypothesized that treatment with FTY720 (fingolimod) would decrease tumorigenicity in medulloblastoma patient-derived xenografts (PDXs). Three Group 3 medulloblastoma PDXs (D341, D384 and D425) were utilized. Expression of PP2A and its endogenous inhibitors I2PP2A and CIP2A was detected by immunohistochemistry and immunoblotting. PP2A activation was measured via phosphatase activation kit. Cell viability, proliferation, migration and invasion assays were performed after treatment with FTY720. Cell cycle analysis was completed using flow cytometry. A flank model using D425 human medulloblastoma PDX cells was used to assess the in vivo effects of FTY720. FTY720 activated PP2A and led to decreased medulloblastoma PDX cell viability, proliferation, migration and invasion and G1 cell cycle arrest in all three PDXs. FTY720 treatment of mice bearing D425 medulloblastoma PDX tumors resulted in a significant decrease in tumor growth compared to vehicle treated animals. FTY720 decreased viability, proliferation, and motility in Group 3 medulloblastoma PDX cells and significantly decreased tumor growth in vivo. These results suggest that FTY720 should be investigated further as a potential therapeutic agent for medulloblastoma.

The emerging role of FTY720 (Fingolimod) in cancer treatment

FTY720 (Fingolimod) is a clinically approved immunomodulating therapy for multiple sclerosis that sequesters T-cells to lymph nodes through functional antagonism of sphingosine-1-phosphate 1 receptor. FTY720 also demonstrates a proven efficacy in multiple in vitro and in vivo cancer models, suggesting a potential therapeutic role in cancer patients. A potential anticancer mechanism of FTY720 is through the inhibition of sphingosine kinase 1, a proto-oncogene with in vitro and clinical cancer association. In addition, FTY720's anticancer properties may be attributable to actions on several other molecular targets. This study focuses on reviewing the emerging evidence regarding the anticancer properties and molecular targets of FTY720. While the clinical transition of FTY720 is currently limited by its immune suppression effects, studies aiming at FTY720 delivery and release together with identifying its key synergetic combinations and relevant patient subsets may lead to its rapid introduction into the clinic.

Concise Review: Pancreatic Cancer and Bone Marrow-Derived Stem Cells

Pancreatic adenocarcinoma remains one of the most challenging diseases of modern gastroenterology, and, even though considerable effort has been put into understanding its pathogenesis, the exact molecular mechanisms underlying the development and/or systemic progression of this malignancy still remain unclear. Recently, much attention has been paid to the potential role of bone marrow-derived stem cells (BMSCs) in this malignancy. Hence, herein, we comprehensively review the most recent discoveries and current achievements and concepts in this field. Specifically, we discuss the significance of identifying pancreatic cancer stem cells and novel therapeutic approaches involving molecular interference of their metabolism. We also describe advances in the current understanding of the biochemical and molecular mechanisms responsible for BMSC mobilization during pancreatic cancer development and systemic spread. Finally, we summarize experimental, translational, and/or clinical evidence regarding the contribution of bone marrow-derived mesenchymal stem cells, endothelial progenitor cells, hematopoietic stem/progenitor cells, and pancreatic stellate cells in pancreatic cancer development/progression. We also present their potential therapeutic value for the treatment of this deadly malignancy in humans.

SIGNIFICANCE

Different bone marrow-derived stem cell populations contribute to the development and/or progression of pancreatic cancer, and they might also be a promising "weapon" that can be used for anticancer treatments in humans. Even though the exact role of these stem cells in pancreatic cancer development and/or progression in humans still remains unclear, this concept continues to drive a completely novel scientific avenue in pancreatic cancer research and gives rise to innovative ideas regarding novel therapeutic modalities that can be safely offered to patients.

Fingolimod therapy modulates circulating B cell composition, increases B regulatory subsets and production of IL-10 and TGFβ in patients with Multiple Sclerosis

Fingolimod, an oral therapeutic agent approved for patients with relapsing-remitting Multiple Sclerosis (MS), has been shown to prevent lymphocyte egress from secondary lymphoid tissues; however the specific drug effect on B cells in fingolimod-treated patients remains to be fully elucidated. We present here a comprehensive analysis on the proportions of B cell subsets in the periphery, and the levels of activation, functional surface markers and cytokine profile of B cells in MS patients, following initiation of fingolimod therapy, using flow cytometry and cytokine bead array. Fingolimod therapy increased the ratio of naïve to memory cells, elevated the percentage of plasma cells and highly increased the proportion of transitional B cells as well as additional regulatory subsets, including: IL10(+), CD25(+) and CD5(+) B cells. The percentage of activated CD69(+) cells was highly elevated in the remaining circulating B cells, which produced increased levels of IL10, TGFβ, IL6, IL4, LTα, TNFα and IFNγ cytokines, with an overall increased ratio of TGFβ to pro-inflammatory cytokines. Furthermore, fingolimod therapy reduced ICAM-1(+) cells, suggesting a possible reduction in antigen-presenting capacity. Phosphorylated-fingolimod was shown in vitro to reduce S1PR1 RNA and protein, to slightly increase viability and to activate anti-apoptotic Bcl2 in transformed B cells of patients with MS. In conclusion, fingolimod therapy modulates significantly the composition of circulating B cells, promoting regulatory subsets and an anti-inflammatory cytokine repertoire.

FTY720 enhances TRAIL-mediated apoptosis by up-regulating DR5 and down-regulating Mcl-1 in cancer cells

FTY720, Fingolimod, is a functional antagonist to the sphingosine-1-phosphate (S1P) receptor and an inhibitor of sphingosine kinase 1. Here, we showed that a combination of FTY720 and TRAIL induced apoptosis in human renal, breast, and colon carcinoma cells. Most importantly, this combination had no effect on normal cells. Furthermore, the combined treatment with FTY720 and TRAIL reduced tumor growth in xenograft models. FTY720 up-regulated death receptor (DR)5 at post-translational level. Knockdown of DR5 markedly blocked apoptosis induced by the combined treatment. FTY720 also inhibited Mcl-1 expression at the post-translational level. Over-expression of Mcl-1 blocked apoptosis induced by FTY720 and TRAIL. Interestingly, phospho-FTY720 and inhibitors of sphingosine kinase failed to enhance TRAIL-induced apoptosis. Thus, FTY720 enables TRAIL-induced apoptosis through up-regulation of DR5 and down-regulation of Mcl-1 in human cancer cells.

Sphingosine kinase 1 is overexpressed and promotes adrenocortical carcinoma progression

Adrenocortical carcinoma (ACC) is a rare endocrine tumor with a very poor prognosis. Sphingosine kinase 1 (SphK1), an oncogenic kinase, has previously been found to be upregulated in various cancers. However, the role of the SphK1 in ACC has not been investigated. In this study, SphK1 mRNA and protein expression levels as well as clinicopathological significance were evaluated in ACC samples. In vitro siRNA knockdown of SphK1 in two ACC cell lines (H295R and SW13) was used to determine its effect on cellular proliferation and invasion. In addition, we further evaluated the effect of SphK1 antagonist fingolimod (FTY720) in ACC in vitro and in vivo, as a single agent or in combination with mitotane, and attempted to explore its anticarcinogenic mechanisms. Our results show a significant over-expression of SphK1 mRNA and protein expression in the carcinomas compared with adenomas (P < 0.01 for all comparisons). Functionally, knockdown of SphK1 gene expression in ACC cell lines significantly decreased cell proliferation and invasion. FTY720 could result in a decreased cell proliferation and induction of apoptosis, and the combination of mitotane and FTY720 resulted in a greater anti-proliferative effect over single agent treatment in SW13 cells. Furthermore, FTY720 could markedly inhibit tumor growth in ACC xenografts. SphK1 expression is functionally associated to cellular proliferation, apoptosis, invasion and mitotane sensitivity of ACC. Our data suggest that SphK1 might be a potential therapeutic target for the treatment of ACC.

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.

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.

Berbamine enhances the antineoplastic activity of gemcitabine in pancreatic cancer cells by activating transforming growth factor-β/Smad signaling

Drug-resistance to gemcitabine chemotherapy in pancreatic cancer is still an unsolved problem. Combinations of other chemotherapy drugs with gemcitabine have been shown to increase the efficacy of gemcitabine-based treatment. In this study, the effect of berbamine on the antitumor activity of gemcitabine was evaluated in human pancreatic cancer cell lines Bxpc-3 and Panc-1, and the underlying mechanisms were explored. Our results demonstrated that berbamine exhibited a time- and dose-dependent inhibitory effect in the pancreatic cancer cell lines. Berbamine enhanced gemcitabine-induced cell growth inhibition and apoptosis in these cells. Combined treatment of berbamine and gemcitabine resulted in down-regulation of anti-apoptotic proteins (Bcl-2, Bcl-xL) and up-regulation of pro-apoptotic proteins (Bax, Bid). More importantly, berbamine treatment in combination with gemcitabine activated the transforming growth factor-β/Smad (TGF-β/Smad) signaling pathway, as a result of a decrease in Smad7 and an increase in transforming growth factor-β receptor II (TβRII) expression. Changes in downstream targets of Smad7, such as up-regulation of p21 and down-regulation of c-Myc and Cyclin D1 were also observed. Therefore, berbamine could enhance the antitumor activity of gemcitabine by inhibiting cell growth and inducing apoptosis, possibly through the regulation of the expression of apoptosis-related proteins and the activation of TGF-β/Smad signaling pathway. Our study indicates that berbamine may be a promising candidate to be used in combination with gemcitabine for pancreatic cancer treatment.

A review of ceramide analogs as potential anticancer agents

Ceramide serves as a central mediator in sphingolipid metabolism and signaling pathways, regulating many fundamental cellular responses. It is referred to as a 'tumor suppressor lipid', since it powerfully potentiates signaling events that drive apoptosis, cell cycle arrest, and autophagic responses. In the typical cancer cell, ceramide levels and signaling are usually suppressed by overexpression of ceramide-metabolizing enzymes or downregulation of ceramide-generating enzymes. However, chemotherapeutic drugs as well as radiotherapy increase intracellular ceramide levels, while exogenously treating cancer cells with short-chain ceramides leads to anticancer effects. All evidence currently points to the fact that the upregulation of ceramide levels is a promising anticancer strategy. In this review, we exhibit many anticancer ceramide analogs as downstream receptor agonists and ceramide-metabolizing enzyme inhibitors.

Overexpression of the pp32r1 (ANP32C) oncogene or its functional mutant pp32r1Y140H confers enhanced resistance to FTY720 (Finguimod)

pp32r1 (ANP32C) is oncogenic and has been shown to be overexpressed in tumors of the breast, prostate, and pancreas. In this work we show that pp32 family proteins are able to bind to the sphingosine analog FTY720 (Finguimod). Molecular docking studies highlight that a conserved residue F136 is likely to be a key determinant of the FTY720 binding site on the pp32 leucine-rich repeat domain. Transduction of the renal carcinoma cell line ACHN or cervical cancer cell line HeLa with lentivirus expressing the oncogenic family member pp32r1 or a pp32r1Y140H functional mutant illustrated an enhanced resistance to FTY720 induced apoptosis. These findings highlight that certain cancers overexpressing pp32r1 or pp32r1 mutants are likely to demonstrate enhanced resistance to FTY720 treatment.

Therapeutic potential of targeting SK1 in human cancers

Sphingosine kinase 1 (SK1) is a lipid enzyme with oncogenic properties that converts the proapoptotic lipids ceramide and sphingosine into the antiapoptotic lipid sphingosine-1-phosphate and activates the signal transduction pathways that lead to cell proliferation, migration, the activation of the inflammatory response, and the impairment of apoptosis. There is compelling evidence that SK1 activation contributes to cancer progression leading to increased oncogenic transformation, tumor growth, resistance to therapies, tumor neovascularization, and metastatic spread. High levels of SK1 expression or activity have been associated with a poor prognosis in several human cancers. Recent studies using cancer cell and mouse models demonstrate a significant potential for SK1-targeting therapies to synergize with the effects of chemotherapy and radiotherapy; however, until recently the absence of clinically applicable SK1 inhibitors has limited the translation of these findings into patients. With the recent discovery of SK1 inhibiting properties of a clinically approved drug FTY720 (Fingolimod), SK1 has gained significant attention from both clinicians and the pharmaceutical industry and it is hoped that trials of newly developed SK1 inhibitors may follow soon. This review provides an overview of the SK1 signaling, its relevance to cancer progression, and the potential clinical significance of targeting SK1 for improved local or systemic control of human cancers.

Bufalin enhances the antitumor effect of gemcitabine in pancreatic cancer

Bufalin, an active component of the Chinese medicine chan'su, has been reported to have an inhibitory effect on the growth of various types of cancer cells. In the present study, we investigated whether gemcitabine combined with bufalin enhanced the antitumor efficacy in pancreatic cancer. Three pancreatic cancer cell lines (Bxpc-3, Mia PaCa-2 and Panc-1) were treated with gemcitabine and/or bufalin in vitro. The combination treatment demonstrated greater inhibition of cellular growth and apoptosis. The activity of apoptosis signal-regulating kinase 1 (ASK1)/JNK was upregulated in gemcitabine-induced apoptosis when combined with bufalin. We also observed that tumor growth was significantly inhibited by the combination therapy in a tumor-bearing mouse model, and upregulation of ASK1 activity was validated by immunohistochemical staining. These results suggest that bufalin may be a potential chemotherapeutic agent for pancreatic cancer, which could enhance the antitumor efficacy of gemcitabine when used in combination, possibly through the activation of ASK1/JNK.

FTY720 normalizes hyperglycemia by stimulating β-cell in vivo regeneration in db/db mice through regulation of cyclin D3 and p57(KIP2)

Loss of insulin-producing β-cell mass is a hallmark of type 2 diabetes in humans and diabetic db/db mice. Pancreatic β-cells can modulate their mass in response to a variety of physiological and pathophysiological cues. There are currently few effective therapeutic approaches targeting β-cell regeneration although some anti-diabetic drugs may positively affect β-cell mass. Here we show that oral administration of FTY720, a sphingosine 1-phosphate (S1P) receptor modulator, to db/db mice normalizes fasting blood glucose by increasing β-cell mass and blood insulin levels without affecting insulin sensitivity. Fasting blood glucose remained normal in the mice even after the drug was withdrawn after 23 weeks of treatment. The islet area in the pancreases of the FTY720-treated db/db mice was more than 2-fold larger than that of the untreated mice after 6 weeks of treatment. Furthermore, BrdU incorporation assays and Ki67 staining demonstrated cell proliferation in the islets and pancreatic duct areas. Finally, islets from the treated mice exhibited a significant decrease in the level of cyclin-dependent kinase inhibitor p57(KIP2) and an increase in the level of cyclin D3 as compared with those of untreated mice, which could be reversed by the inhibition of phosphatidylinositol 3-kinase (PI3K). Our findings reveal a novel network that controls β-cell regeneration in the obesity-diabetes setting by regulating cyclin D3 and p57(KIP2) expression through the S1P signaling pathway. Therapeutic strategies targeting this network may promote in vivo regeneration of β-cells in patients and prevent and/or cure type 2 diabetes.

PTEN- and p53-mediated apoptosis and cell cycle arrest by FTY720 in gastric cancer cells and nude mice

FTY720, a new immunosuppressant, derived from ISP-1, has been studied for its putative anti-cancer properties in the recent years. In this study, we have reported that FTY720 greatly inhibited gastric cancer cell proliferation for the first time, and found this effect was associated with G1 phase cell cycle arrest and apoptosis. Results from our Western blotting and Real-time PCR showed that FTY720 induced obvious PTEN expression in a p53-independent way, consistent with a substantial decrease in p-Akt and MDM2. FTY720 dramatically increased the expression of Cip1/p21, p27, and BH3-only proteins through the accumulation of p53 by PTEN-mediated inhibition of the PI3K/Akt/MDM2 signaling. Suppression of PTEN expression with siRNA significantly reduced the p53 and p21 levels and activated Akt, resulting in decreased apoptosis and increased cell survival. Furthermore, we have observed an additive effect of FTY720 in killing gastric cancer cells when in combination with Cisplatin, partly through PTEN-mediated Akt/MDM2 inhibition. In vivo study has also shown that tumor growth was significantly suppressed after FTY720 treatment. In conclusion, our results suggest that FTY720 induces a significant increase of PTEN, which inhibits p-Akt and MDM2, and then increases the level of p53, thereby inducing G1 phase arrest and apoptosis. We have characterized a novel immunosuppressant, for the first time, which shows potential anti-tumor effects on gastric cancer by PTEN activation through p53-independent mechanism, especially in combination with Cisplatin. This PTEN target-based therapy is worth further investigation and warrants clinical evaluation.

FTY720 and (S)-FTY720 vinylphosphonate inhibit sphingosine kinase 1 and promote its proteasomal degradation in human pulmonary artery smooth muscle, breast cancer and androgen-independent prostate cancer cells

Sphingosine kinase 1 (SK1) is an enzyme that catalyses the phosphorylation of sphingosine to produce the bioactive lipid sphingosine 1-phosphate (S1P). We demonstrate here that FTY720 (Fingolimod) and (S)-FTY720 vinylphosphonate are novel inhibitors of SK1 catalytic activity and induce the proteasomal degradation of this enzyme in human pulmonary artery smooth muscle cells, MCF-7 breast cancer cells and androgen-independent LNCaP-AI prostate cancer cells. Proteasomal degradation of SK1 in response to FTY720 and (S)-FTY720 vinylphosphonate is associated with the down-regulation of the androgen receptor in LNCaP-AI cells. (S)-FTY720 vinylphosphonate also induces the apoptosis of these cells. These findings indicate that SK1 is involved in protecting LNCaP-AI from apoptosis. This protection might be mediated by so-called 'inside-out' signalling by S1P, as LNCaP-AI cells exhibit increased expression of S1P(2/3) receptors and reduced lipid phosphate phosphatase expression (compared with androgen-sensitive LNCaP cells) thereby potentially increasing the bioavailability of S1P at S1P(2/3) receptors.

Targeting sphingolipid metabolism in head and neck cancer: rational therapeutic potentials

IMPORTANCE OF THE FIELD

Ceramide accumulation has been shown to be a conserved mechanism of apoptosis initiation in normal physiological processes as well as in response to cancer treatments. Therefore, it is unsurprising that many cancers develop aberrations of sphingolipid metabolism that prevent the accumulation of ceramide, whether by reduction of ceramide generation or by enhanced ceramide catabolism, particularly dangerous when catabolism leads to generation of pro-tumor sphingosine-1-phosphate and ceramide-1-phosphate. Numerous studies have now implicated dysregulation of sphingolipid metabolism in head and neck cancers.

AREAS COVERED IN THIS REVIEW

This review highlights the importance of sphingolipid metabolism and brings sphingolipid metabolism to the forefront in the investigation of novel therapies for head and neck cancer. It reviews sphingolipid-centric therapies under investigation in preclinical and clinical trials of cancers of the head and neck.

WHAT THE READER WILL GAIN

The roles of sphingolipids and sphingolipid metabolism in cancer are reviewed and the reader will be brought up to date with discoveries in the field of sphingolipid metabolism in head and neck cancer.

TAKE HOME MESSAGE

As treatments for head and neck cancers are currently limited, the potential of targeting sphingolipid metabolism should be taken into consideration as we seek novel ways to combat this group of tumors.

Pharmacological manipulation of the akt signaling pathway regulates myxoma virus replication and tropism in human cancer cells

Viruses have evolved an assortment of mechanisms for regulating the Akt signaling pathway to establish a cellular environment more favorable for viral replication. Myxoma virus (MYXV) is a rabbit-specific poxvirus that encodes many immunomodulatory factors, including an ankyrin repeat-containing host range protein termed M-T5 that functions to regulate tropism of MYXV for rabbit lymphocytes and certain human cancer cells. MYXV permissiveness in these human cancer cells is dependent upon the direct interaction between M-T5 and Akt, which has been shown to induce the kinase activity of Akt. In this study, an array of compounds that selectively manipulate Akt signaling was screened and we show that only a subset of Akt inhibitors significantly decreased the ability of MYXV to replicate in previously permissive human cancer cells. Furthermore, reduced viral replication efficiency was correlated with lower levels of phosphorylated Akt. In contrast, the PP2A-specific phosphatase inhibitor okadaic acid promoted increased Akt kinase activation and rescued MYXV replication in human cancer cells that did not previously support viral replication. Finally, phosphorylation of Akt at residue Thr308 was shown to dictate the physical interaction between Akt and M-T5, which then leads to phosphorylation of Ser473 and permits productive MYXV replication in these human cancer cells. The results of this study further characterize the mechanism by which M-T5 exploits the Akt signaling cascade and affirms this interaction as a major tropism determinant that regulates the replication efficiency of MYXV in human cancer cells.

Involvement of p38 mitogen-activated protein kinase pathway in honokiol-induced apoptosis in a human hepatoma cell line (hepG2)

BACKGROUND

Honokiol has been known to have antitumour activity. This study was conducted to evaluate the antiproliferative potential of honokiol against the hepG2 heptocellular cell line and its mechanism of action.

METHODS

hepG2 cells were treated with honokiol of 0-40 microg/ml concentration. The cytotoxic effect of honokiol was determined by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The apoptosis was evaluated by flow cytometry. Western blots were used to analyse the expression of various proteins (procaspase-9, procaspase-3, cleaved caspase-3, cytochrome c, Bcl-2, Bax, Bad, Bcl-X(L) and p38).

RESULTS

Honokiol induced apoptosis with a decreased expression of procaspase-3 and -9 and an increased expression of active caspase-3. Exposure of hepG2 cells to honokiol resulted in the downregulation of Bcl-X(L) and Bcl-2 expression and the release of mitochondrial cytochrome c to the cytosol. In addition, honokiol activated the p38 mitogen-activated protein kinase (MAPK) pathway, and the inhibition of this pathway by SB203580 reduced honokiol-induced apoptosis and activation of caspase-3.

CONCLUSION

Honokiol induces apoptosis of hepG2 human hepatocellular carcinoma cells through activation of the p38 MAPK pathway, and, in turn, activation of caspase-3.

Downregulating sphingosine kinase-1 for cancer therapy

BACKGROUND

The sphingolipids ceramide and sphingosine 1-phosphate (S1P) are key regulators of cell death and proliferation. The subtle balance between their intracellular levels is governed mainly by sphingosine kinase-1, which produces the pro-survival S1P. Sphingosine kinase-1 is an oncogene; is overexpressed in many tumors; protects cancer cells from apoptosis in vitro and in vivo; and its activity is decreased by anticancer therapies. Hence, sphingosine kinase-1 appears to be a target of interest for therapeutic manipulation.

OBJECTIVE

This review considers recent developments regarding the involvement of sphingosine kinase-1 as a therapeutic target for cancer, and describes the pharmacological tools currently available.

RESULTS/CONCLUSION

The studies described provide strong evidence that strategies to kill cancer cells via sphingosine kinase-1 inhibition are valid and could have a favorable therapeutic index.

K6PC-5, a sphingosine kinase activator, induces anti-aging effects in intrinsically aged skin through intracellular Ca2+ signaling

BACKGROUND

Sphingosine-1-phosphate (S1P), a bioactive sphingolipid metabolite, regulates multiple cellular responses such as Ca(2+) signaling, growth, survival, and differentiation. Because sphingosine kinase (SK) is the enzyme directly responsible for the production of S1P, many factors have been identified that regulate its activity and subsequent S1P levels. To date, there are no reports to demonstrate a chemically induced, direct activation of SK.

OBJECTIVE

Here we have studied the effects of K6PC-5 as a newly synthesized SK activator on fibroblast proliferation in both human fibroblasts and aged mouse skin. To demonstrate that K6PC-5 has S1P-mediated action mechanism in fibroblasts, we have measured SK-dependent intracellular Ca(2+) signaling.

METHODS

Fibroblasts were cultured primarily from human foreskin and were used to study the effect of K6PC-5 and S1P on intracellular Ca(2+) signaling and fibroblast proliferation. Changes in intracellular Ca(2+) were detected by fluorescence with fura-2/AM. To study skin anti-aging effects of K6PC-5, we used intrinsically aged hairless mice (56 weeks old).

RESULTS

K6PC-5 promoted fibroblast proliferation and procollagen production in human fibroblasts significantly. K6PC-5 induced intracellular Ca(2+) concentration ([Ca(2+)](i)) oscillations in human fibroblasts. Both dimethylsphingosine and dihydroxysphingosine, SK inhibitors, and the transfection of SK1-siRNA blocked the K6PC-5-induced increases in [Ca(2+)](i), an effect independent of the classical PLC/IP(3)-mediated pathway. The K6PC-5-induced [Ca(2+)](i) oscillations were dependent on thapsigargin-sensitive Ca(2+) stores and Ca(2+) entry. Topical application of K6PC-5 for 2 weeks to intrinsically aged hairless mice enhanced fibroblast proliferation, collagen production, and eventually increased dermal thickness (10%). K6PC-5 also promoted specific epidermal differentiation marker proteins, including involucrin, loricrin, filaggrin, and keratin 5, without any alterations on epidermal barrier function.

CONCLUSION

These results suggest that K6PC-5 acts to regulate fibroblast proliferation through intracellular S1P production, and can further promote keratinocyte differentiation. We anticipate that the regulation of S1P levels may represent a novel approach for the treatment of skin disorders, including skin aging.