Sphingosine kinase 1 regulates the Akt/FOXO3a/Bim pathway and contributes to apoptosis resistance in glioma cells

The Role of ALDH1A1 in Glioblastoma Proliferation and Invasion

High-grade gliomas, including glioblastoma multiforme (GBM), continue to be a leading aggressive brain tumor in adults, marked by its rapid growth and invasive nature. Aldehyde dehydrogenase 1 family, member A1 (ALDH1A1), an enzyme, plays a significant role in tumor progression, yet its function in high-grade gliomas is still poorly investigated. In this study, we evaluated ALDH1A1 levels in clinical samples of GBM. We also assessed the prognostic significance of ALDH1A1 expression in GBM and LGG (low grade glioma) patients using TCGA (The Cancer Genome Atlas) database analysis. The MTT and transwell assays were utilized to examine cell growth and the invasive capability of U87 cells, respectively. We quantitatively examined markers for cell proliferation (Ki-67 and cyclin D1) and invasion (MMP2 and 9). A Western blot test was conducted to determine the downstream signaling of ALDH1A1. We found a notable increase in ALDH1A1 expression in high-grade gliomas compared to their low-grade counterparts. U87 cells that overexpressed ALDH1A1 showed increased cell growth and invasion. We found that ALDH1A1 promotes the phosphorylation of AKT, and inhibiting AKT phosphorylation mitigates the ALDH1A1's effects on tumor growth and migration. In summary, our findings suggest ALDH1A1 as a potential therapeutic target for GBM treatment.

Sphingosine 1-Phosphate Stimulates ER to Golgi Ceramide Traffic to Promote Survival in T98G Glioma Cells

Glioblastoma multiforme is the most common and fatal brain tumor among human cancers. Ceramide (Cer) and Sphingosine 1-phosphate (S1P) have emerged as bioeffector molecules that control several biological processes involved in both cancer development and resistance. Cer acts as a tumor suppressor, inhibiting cancer progression, promoting apoptosis, enhancing immunotherapy and sensitizing cells to chemotherapy. In contrast, S1P functions as an onco-promoter molecule, increasing proliferation, survival, invasiveness, and resistance to drug-induced apoptosis. The pro-survival PI3K/Akt pathway is a recognized downstream target of S1P, and we have previously demonstrated that in glioma cells it also improves Cer transport and metabolism towards complex sphingolipids in glioma cells. Here, we first examined the possibility that, in T98G glioma cells, S1P may regulate Cer metabolism through PI3K/Akt signaling. Our research showed that exogenous S1P increases the rate of vesicular trafficking of Cer from the endoplasmic reticulum (ER) to the Golgi apparatus through S1P receptor-mediated activation of the PI3K/Akt pathway. Interestingly, the effect of S1P results in cell protection against toxicity arising from Cer accumulation in the ER, highlighting the role of S1P as a survival factor to escape from the Cer-generating cell death response.

Forkhead box transcription factors (FOXOs and FOXM1) in glioma: from molecular mechanisms to therapeutics

Glioma is the most aggressive and malignant type of primary brain tumor, comprises the majority of central nervous system deaths, and is categorized into different subgroups according to its histological characteristics, including astrocytomas, oligodendrogliomas, glioblastoma multiforme (GBM), and mixed tumors. The forkhead box (FOX) transcription factors comprise a collection of proteins that play various roles in numerous complex molecular cascades and have been discovered to be differentially expressed in distinct glioma subtypes. FOXM1 and FOXOs have been recognized as crucial transcription factors in tumor cells, including glioma cells. Accumulating data indicates that FOXM1 acts as an oncogene in various types of cancers, and a significant part of studies has investigated its function in glioma. Although recent studies considered FOXO subgroups as tumor suppressors, there are pieces of evidence that they may have an oncogenic role. This review will discuss the subtle functions of FOXOs and FOXM1 in gliomas, dissecting their regulatory network with other proteins, microRNAs and their role in glioma progression, including stem cell differentiation and therapy resistance/sensitivity, alongside highlighting recent pharmacological progress for modulating their expression.

Mammalian cells internalize bacteriophages and use them as a resource to enhance cellular growth and survival

There is a growing appreciation that the direct interaction between bacteriophages and the mammalian host can facilitate diverse and unexplored symbioses. Yet the impact these bacteriophages may have on mammalian cellular and immunological processes is poorly understood. Here, we applied highly purified phage T4, free from bacterial by-products and endotoxins to mammalian cells and analyzed the cellular responses using luciferase reporter and antibody microarray assays. Phage preparations were applied in vitro to either A549 lung epithelial cells, MDCK-I kidney cells, or primary mouse bone marrow derived macrophages with the phage-free supernatant serving as a comparative control. Highly purified T4 phages were rapidly internalized by mammalian cells and accumulated within macropinosomes but did not activate the inflammatory DNA response TLR9 or cGAS-STING pathways. Following 8 hours of incubation with T4 phage, whole cell lysates were analyzed via antibody microarray that detected expression and phosphorylation levels of human signaling proteins. T4 phage application led to the activation of AKT-dependent pathways, resulting in an increase in cell metabolism, survival, and actin reorganization, the last being critical for macropinocytosis and potentially regulating a positive feedback loop to drive further phage internalization. T4 phages additionally down-regulated CDK1 and its downstream effectors, leading to an inhibition of cell cycle progression and an increase in cellular growth through a prolonged G1 phase. These interactions demonstrate that highly purified T4 phages do not activate DNA-mediated inflammatory pathways but do trigger protein phosphorylation cascades that promote cellular growth and survival. We conclude that mammalian cells are internalizing bacteriophages as a resource to promote cellular growth and metabolism.

The CNS-penetrating taxane drug TPI 287 potentiates antiglioma activity of the AURKA inhibitor alisertib in vivo

INTRODUCTION

Glioblastoma (GBM) has a very poor prognosis despite current treatment. We previously found cytotoxic synergy between the AURKA inhibitor alisertib and the CNS-penetrating taxane TPI 287 against GBM tumor cells in vitro.

METHODS

We used an orthotopic human GBM xenograft mouse model to test if TPI 287 potentiates alisertib in vivo. Western blotting, immunohistochemistry, siRNA knockdown, annexin V binding, and 3-dimensional Matrigel invasion assays were used to investigate potential mechanisms of alisertib and TPI 287 treatment interactions.

RESULTS

Alisertib + TPI 287 combination therapy significantly prolonged animal survival compared to vehicle (p = 0.011), but only marginally compared to alisertib alone. Alisertib, TPI 287, and combined alisertib + TPI 287 reduced animal tumor volume compared to vehicle-treated controls. This was statistically significant for the combination therapy at 4 weeks (p < 0.0001). Alisertib + TPI 287 treatment decreased anti-apoptotic Bcl-2 protein levels in vivo and in vitro. Expression of the pro-apoptotic protein Bak was significantly increased by combination treatment (p < 0.0001). Pro-apoptotic Bim and Bak knockdown by siRNA decreased apoptosis by alisertib + TPI 287 in GB9, GB30, and U87 cells (p = 0.0005 to 0.0381). Although alisertib and TPI 287 significantly reduced GBM cell invasion (p < 0.0001), their combination was no more effective than TPI 287 alone.

CONCLUSIONS

Results suggest that apoptosis is the dominant mechanism of potentiation of GBM growth inhibition by alisertib + TPI 287, in part through effects on Bcl-2 family proteins, providing a rationale for further laboratory testing of an AURKA inhibitor plus TPI 287 as a potential therapy against GBM.

The Role of Micro RNAs in Regulating PI3K/AKT Signaling Pathways in Glioblastoma

Glioblastoma is a type of brain cancer with aggressive and invasive nature. Such features result from increased proliferation and migration and also poor apoptosis of glioma cells leading to resistance to current treatments such as chemotherapy and radiotherapy. In recent studies, micro RNAs have been introduced as a novel target for treating glioblastoma via regulation of apoptotic signaling pathway, remarkably PI3K/AKT, which affect cellular functions and blockage or progression of the tumor. In this review, we focus on PI3K/AKT signaling pathway and other related apoptotic processes contributing to glioblastoma and investigate the role of micro RNAs interfering in apoptosis, invasion and proliferation of glioma through such apoptotic processes pathways. Databases NCBI, PubMed, and Web of Science were searched for published English articles using keywords such as 'miRNA OR microRNA', 'Glioblastoma', 'apoptotic pathways', 'PI3K and AKT', 'Caspase signaling Pathway' and 'Notch pathway'. Most articles were published from 7 May 2015 to 16 June 2020. This study focused on PI3K/AKT signaling pathway affecting glioma cells in separated subparts. Also, other related apoptotic pathways as the Caspase cycle and Notch have been also investigated. Nearly 40 miRNAs were found as tumor suppressors or onco-miRNA, and their targets, which regulated subcomponents participating in proliferation, invasion, and apoptosis of the tumoral cells. Our review reveals that miRNAs affect key molecules in signaling apoptotic pathways, partly PI3K/AKT, making them potential therapeutic targets to overcome the tumor. However, their utility as a novel treatment for glioblastoma requires further examination and investigation.

Is Sphingosine-1-Phosphate a Regulator of Tumor Vascular Functionality?

Simple Summary

Despite substantial theoretical and experimental support for using vascular normalization as cancer therapy, effectively achieving this strategy in the clinic remains complex. In the present paper, we propose a novel potential approach for the induction of tumor vascular normalization, reduction of hypoxia, and improvement of conventional treatment in cancer patients. This approach consists of the pharmacological modulation of a patient’s plasma S1P levels which through a PDGF signaling can enhance tumor vasculature functionality and reduce hypoxia. This approach is proposed following a clinical observation in pancreatic adenocarcinoma patients and pre-clinical data in different in vivo tumor models, and is supported by a review of the literature describing the biological role of S1P in vascular functionality regulation.

Abstract

Increasing evidence indicates that tumor vasculature normalization could be an appropriate strategy to increase therapies’ efficacy in solid tumors by decreasing hypoxia and improving drug delivery. We searched for a novel approach that reduces hypoxia and enhances chemotherapy efficacy in pancreatic adenocarcinoma which is characterized by disrupted blood vasculature associated with poor patient survival. Clinical significance of plasma levels of the angiogenic lipid sphingosine-1-phosphate (S1P) was assessed at baseline in 175 patients. High plasma S1P concentration was found to be a favorable prognostic/predictive marker in advanced/metastatic pancreatic adenocarcinoma patients treated by gemcitabine alone but not in patients receiving a combination gemcitabine and PDGFR-inhibitor. In pancreatic adenocarcinoma PDX models, oral administration of an S1P lyase inhibitor (LX2931) significantly increased plasma S1P levels, decreased tumor expression of the hypoxia marker (CA IX), and enhanced chemotherapy efficacy when combined with gemcitabine treatment. The direct effect of S1P on tumor oxygenation was assessed by administration of S1P onto tumor-grafted CAM model and measuring intra-tumoral pO2 using a tissue oxygen monitor. S1P increased pO2 in a tumor-CAM model. Thus, increasing plasma S1P is a promising strategy to decrease tumor hypoxia and enhance therapy efficacy in solid tumors. S1P may act as a tumor vasculature normalizer.

The Role of Sphingolipid Signaling in Oxidative Lung Injury and Pathogenesis of Bronchopulmonary Dysplasia

Premature infants are born with developing lungs burdened by surfactant deficiency and a dearth of antioxidant defense systems. Survival rate of such infants has significantly improved due to advances in care involving mechanical ventilation and oxygen supplementation. However, a significant subset of such survivors develops the chronic lung disease, Bronchopulmonary dysplasia (BPD), characterized by enlarged, simplified alveoli and deformed airways. Among a host of factors contributing to the pathogenesis is oxidative damage induced by exposure of the developing lungs to hyperoxia. Recent data indicate that hyperoxia induces aberrant sphingolipid signaling, leading to mitochondrial dysfunction and abnormal reactive oxygen species (ROS) formation (ROS). The role of sphingolipids such as ceramides and sphingosine 1-phosphate (S1P), in the development of BPD emerged in the last decade. Both ceramide and S1P are elevated in tracheal aspirates of premature infants of <32 weeks gestational age developing BPD. This was faithfully reflected in the murine models of hyperoxia and BPD, where there is an increased expression of sphingolipid metabolites both in lung tissue and bronchoalveolar lavage. Treatment of neonatal pups with a sphingosine kinase1 specific inhibitor, PF543, resulted in protection against BPD as neonates, accompanied by improved lung function and reduced airway remodeling as adults. This was accompanied by reduced mitochondrial ROS formation. S1P receptor1 induced by hyperoxia also aggravates BPD, revealing another potential druggable target in this pathway for BPD. In this review we aim to provide a detailed description on the role played by sphingolipid signaling in hyperoxia induced lung injury and BPD.

Interaction of microRNAs with sphingosine kinases, sphingosine-1 phosphate, and sphingosine-1 phosphate receptors in cancer

Sphingosine-1-phosphate (S1P), a pleiotropic lipid mediator, participates in various cellular processes during tumorigenesis, including cell proliferation, survival, drug resistance, metastasis, and angiogenesis. S1P is formed by two sphingosine kinases (SphKs), SphK1 and SphK2. The intracellularly produced S1P is delivered to the extracellular space by ATP-binding cassette (ABC) transporters and spinster homolog 2 (SPNS2), where it binds to five transmembrane G protein-coupled receptors to mediate its oncogenic functions (S1PR1-S1PR5). MicroRNAs (miRNAs) are small non-coding RNAs, 21-25 nucleotides in length, that play numerous crucial roles in cancer, such as tumor initiation, progression, apoptosis, metastasis, and angiogenesis via binding to the 3'-untranslated region (3'-UTR) of the target mRNA. There is growing evidence that various miRNAs modulate tumorigenesis by regulating the expression of SphKs, and S1P receptors. We have reviewed various roles of miRNAs, SphKs, S1P, and S1P receptors (S1PRs) in malignancies and how notable miRNAs like miR-101, miR-125b, miR-128, and miR-506, miR-1246, miR-21, miR-126, miR499a, miR20a-5p, miR-140-5p, miR-224, miR-137, miR-183-5p, miR-194, miR181b, miR136, and miR-675-3p, modulate S1P signaling. These tumorigenesis modulating miRNAs are involved in different cancers including breast, gastric, hepatocellular carcinoma, prostate, colorectal, cervical, ovarian, and lung cancer via cell proliferation, invasion, angiogenesis, apoptosis, metastasis, immune evasion, chemoresistance, and chemosensitivity. Therefore, understanding the interaction of SphKs, S1P, and S1P receptors with miRNAs in human malignancies will lead to better insights for miRNA-based cancer therapy.

Ubiquitination Destabilizes Protein Sphingosine Kinase 2 to Regulate Glioma Malignancy

Gliomas are the most common and lethal malignant tumor in the central nervous system. The tumor oncogene sphingosine kinase 2 (SphK2) was previously found to be upregulated in glioma tissues and enhance glioma cell epithelial-to-mesenchymal transition through the AKT/β-catenin pathway. Nevertheless, ubiquitination of SphK2 protein has yet to be well elucidated. In this study, mass spectrometry analysis was performed to identify proteins that interacted with SphK2 protein. Co-immunoprecipitation (co-IP) and immunoblotting (IB) were used to prove the specific interaction between SphK2 protein and the neural precursor cell-expressed developmentally downregulated 4-like (NEDD4L) protein. Fluorescence microscopy was used for detecting the distribution of related proteins. Ubiquitylation assay was utilized to characterize that SphK2 was ubiquitylated by NEDD4L. Cell viability assay, flow cytometry assay, and transwell invasion assay were performed to illustrate the roles of NEDD4L-mediated SphK2 ubiquitination in glioma viability, apoptosis, and invasion, respectively. We found that NEDD4L directly interacted with SphK2 and ubiquinated it for degradation. Ubiquitination of SphK2 mediated by NEDD4L overexpression suppressed glioma cell viability and invasion but promoted glioma apoptosis. Knockdown of NEDD4L presented opposite results. Moreover, further results suggested that ubiquitination of SphK2 regulated glioma malignancy via the AKT/β-catenin pathway. in vivo assay also supported the above findings. This study reveals that NEDD4L mediates SphK2 ubiquitination to regulate glioma malignancy and may provide some meaningful suggestions for glioma treatment.

Physiological and pathological functions of sphingolipids in pregnancy

Signaling by the bioactive sphingolipid, sphingosine 1-phosphate (S1P), and its precursors are emerging areas in pregnancy research. S1P and ceramide levels increase towards end of gestation, suggesting a physiological role in parturition. However, high levels of circulating S1P and ceramide are correlated with pregnancy disorders such as preeclampsia, gestational diabetes mellitus and intrauterine growth restriction. Expression of placental and decidual enzymes that metabolize S1P and S1P receptors are also dysregulated during pregnancy complications. In this review, we provide an in-depth examination of the signaling mechanism of S1P and ceramide in various reproductive tissues during gestation. These factors determine implantation and early pregnancy success by modulating corpus luteum function from progesterone production to luteolysis through to apoptosis. We also highlight the role of S1P through receptor signaling in inducing decidualization and angiogenesis in the decidua, as well as regulating extravillous trophoblast migration to anchor the placenta into the uterine wall. Recent advances on the role of the S1P:ceramide rheostat in controlling the fate of villous trophoblasts and the role of S1P as a negative regulator of trophoblast syncytialization to a multinucleated placental barrier are discussed. This review also explores the role of S1P in anti-inflammatory and pro-inflammatory signaling, its role as a vasoconstrictor, and the effects of S1P metabolizing enzymes and receptors in pregnancy.

The role of the sphingolipid pathway in liver fibrosis: an emerging new potential target for novel therapies

Sphingolipids (SL) are a family of bioactive lipids and a major cellular membrane structural component. SLs include three main compounds: ceramide (Cer), sphingosine (Sp), and sphingosine-1-phosphate (S-1P), all of which have emerging roles in biological functions in cells, especially in the liver. They are under investigation in various liver diseases, including cirrhosis and end-stage liver disease. In this review, we provide an overview on the role of SLs in liver pathobiology and focus on their potential role in the development of hepatic fibrosis. We describe recent evidence and suggest SLs are a promising potential therapeutic target for the treatment of liver disease and fibrosis.

Sphingosine-1-Phosphate in the Tumor Microenvironment: A Signaling Hub Regulating Cancer Hallmarks

As a key hub of malignant properties, the cancer microenvironment plays a crucial role intimately connected to tumor properties. Accumulating evidence supports that the lysophospholipid sphingosine-1-phosphate acts as a key signal in the cancer extracellular milieu. In this review, we have a particular focus on glioblastoma, representative of a highly aggressive and deleterious neoplasm in humans. First, we highlight recent advances and emerging concepts for how tumor cells and different recruited normal cells contribute to the sphingosine-1-phosphate enrichment in the cancer microenvironment. Then, we describe and discuss how sphingosine-1-phosphate signaling contributes to favor cancer hallmarks including enhancement of proliferation, stemness, invasion, death resistance, angiogenesis, immune evasion and, possibly, aberrant metabolism. We also discuss the potential of how sphingosine-1-phosphate control mechanisms are coordinated across distinct cancer microenvironments. Further progress in understanding the role of S1P signaling in cancer will depend crucially on increasing knowledge of its participation in the tumor microenvironment.

Immunohistochemical Characterization of Procaspase-3 Overexpression as a Druggable Target With PAC-1, a Procaspase-3 Activator, in Canine and Human Brain Cancers

Gliomas and meningiomas are the most common brain neoplasms affecting both humans and canines, and identifying druggable targets conserved across multiple brain cancer histologies and comparative species could broadly improve treatment outcomes. While satisfactory cure rates for low grade, non-invasive brain cancers are achievable with conventional therapies including surgery and radiation, the management of non-resectable or recurrent brain tumors remains problematic and necessitates the discovery of novel therapies that could be accelerated through a comparative approach, such as the inclusion of pet dogs with naturally-occurring brain cancers. Evidence supports procaspase-3 as a druggable brain cancer target with PAC-1, a pro-apoptotic, small molecule activator of procaspase-3 that crosses the blood-brain barrier. Procaspase-3 is frequently overexpressed in malignantly transformed tissues and provides a preferential target for inducing cancer cell apoptosis. While preliminary evidence supports procaspase-3 as a viable target in preclinical models, with PAC-1 demonstrating activity in rodent models and dogs with spontaneous brain tumors, the broader applicability of procaspase-3 as a target in human brain cancers, as well as the comparability of procaspase-3 expressions between differing species, requires further investigation. As such, a large-scale validation of procaspase-3 as a druggable target was undertaken across 651 human and canine brain tumors. Relative to normal brain tissues, procaspase-3 was overexpressed in histologically diverse cancerous brain tissues, supporting procaspase-3 as a broad and conserved therapeutic target. Additionally, procaspase-3 expressing glioma and meningioma cell lines were sensitive to the apoptotic effects of PAC-1 at biologically relevant exposures achievable in cancer patients. Importantly, the clinical relevance of procaspase-3 as a potential prognostic variable was demonstrated in human astrocytomas of variable histologic grades and associated clinical outcomes, whereby tumoral procaspase-3 expression was negatively correlated with survival; findings which suggest that PAC-1 might provide the greatest benefit for patients with the most guarded prognoses.

LncRNA DUXAP9-206 directly binds with Cbl-b to augment EGFR signaling and promotes non-small cell lung cancer progression

Long noncoding RNAs (lncRNAs) are involved in the pathology of various tumours, including non‐small cell lung cancer (NSCLC). However, the underlying molecular mechanisms of their specific association with NSCLC have not been fully elucidated. Here, we report that a cytoplasmic lncRNA, DUXAP9‐206 is overexpressed in NSCLC cells and closely related to NSCLC clinical features and poor patient survival. We reveal that DUXAP9‐206 induced NSCLC cell proliferation and metastasis by directly interacting with Cbl‐b, an E3 ubiquitin ligase, and reducing the degradation of epidermal growth factor receptor (EGFR) and thereby augmenting EGFR signaling in NSCLC. Notably, correlations between DUXAP9‐206 and activated EGFR signaling were also validated in NSCLC patient specimens. Collectively, our findings reveal the novel molecular mechanisms of DUXAP9‐206 in mediating the progression of NSCLC and DUXAP9‐206 may serve as a potential target for NSCLC therapy.

The sphingosine kinase-1/sphingosine-1-phosphate axis in cancer: Potential target for anticancer therapy

Sphingolipid metabolites, such as ceramide, sphingosine and sphingosine-1-phosphate (S1P), play many important roles in cellular activities. Ceramide and sphingosine inhibit cell proliferation and induce cell apoptosis while S1P has the opposite effect. Maintaining a metabolic balance of sphingolipids is essential for growth and development of cells. Sphingosine kinase (SPHK) is an important regulator for keeping this balance. It controls the level of S1P and plays important roles in proliferation, migration, and invasion of cancer cells and tumor angiogenesis. There are two isoenzymes of sphingosine kinase, SPHK1 and SPHK2. SPHK1 is ubiquitously expressed in most cancers where it promotes survival and proliferation, while SPHK2 is restricted to only certain tissues and its functions are not well characterized. SPHK1 is currently considered as a novel target for the treatment of cancers. Targeting SPHK1 would provide new strategies for cancer treatment and improve the prognosis of cancer patients. Here we review and summarize the current research findings on the SPHK1-S1P axis in cancer from many aspects including structure, expression, regulation, mechanism, and potential inhibitors.

Transcriptomic analysis of lung tissues after hUC-MSCs and FTY720 treatment of lipopolysaccharide-induced acute lung injury in mouse models

Acute lung injury and acute respiratory distress syndrome (ALI/ARDS) refer to acute and progressive hypoxic respiratory failure caused by non-cardiogenic factors, which is a common condition occurring in critically ill patients with widespread pulmonary inflammation. Use of a single medication or target cannot treat ALI/ARDS. Mesenchymal stem cells (MSCs) and FTY720, as an analogue of sphingosine-1-phosphate (S1P), can mitigate lipopolysaccharide (LPS)-induced inflammatory lung injury. In this investigation, the clinical efficacy of MSCs alone, FTY720 alone, and a MSC and FTY720 combination in the treatment of LPS-induced lung injury was evaluated in mouse models. The experimental results demonstrated that both MSCs and FTY720 alleviate lung injuries in mice. The combined application of MSCs and FTY720 yielded higher clinical efficacy in mitigating lung injuries compared with use of MSCs or FTY720 alone. Transcriptomic analysis was performed using an Agilent gene expression chip. By analyzing the differences in gene expression of lung tissues between treated and non-treated ALI/ARDS mice, Gene Ontology and Pathway terms related to ALI/ARDS treatment were identified. Moreover, the target genes which might play a pivotal role in the treatment of ALI/ARDS were also detected, thus providing a theoretical basis for multi-target or multi-drug combined treatment of ALI/ARDS and lay a solid foundation for clinical treatment of ALI/ARDS.

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.

MicroRNA 26b promotes colorectal cancer metastasis by downregulating phosphatase and tensin homolog and wingless-type MMTV integration site family member 5A

Invasion and metastasis are crucially important factors in the survival of malignant tumors. Epithelial-mesenchymal transition (EMT) is an early step in metastatic progression and the presence of cancer stem cells is closely related to tumor survival, proliferation, metastasis, and recurrence. Herein we report that ectopic overexpression of microRNA 26b (miR-26b) in colorectal cancer (CRC) cell lines promoted EMT and stem cell-like phenotypes in vitro. Furthermore, miR-26b directly targeted and suppressed multiple tumor suppressors, including phosphatase and tensin homolog (PTEN) and wingless-type MMTV integration site family member 5A (WNT5A). Notably, miR-26b is markedly upregulated in tumor samples from patients with lymphatic metastases. These results indicate that miR-26b promotes CRC metastasis by downregulating PTEN and WNT5A, and may represent a therapeutic target for metastatic CRC.

MicroRNA-370 suppresses the progression and proliferation of human astrocytoma and glioblastoma by negatively regulating β-catenin and causing activation of FOXO3a

Certain microRNAs (miRs) regulate the progression and metastasis of various cancer types. In the present study, the role of miR-370 in the progression and proliferation of human astrocytoma and glioblastoma cells was assessed and the underlying molecular mechanism was investigated. miR-370 levels in clinical specimens of human glioma and peritumoral tissues were determined by reverse-transcription quantitative PCR. Oligonucleotide mimics and inhibitors were transfected into the U-251MG human astrocytoma cell line and the and U-87MG glioblastoma cell line and the cell viability of was determined by an MTT assay. The expression of β-catenin and forkhead box protein (FOX)O3a was determined by western blot analysis. The results revealed that the expression of miR-370 in human glioma tissues was significantly decreased compared with that in peritumoral tissues. The miR-370 levels in patients with grade III/IV gliomas were significantly decreased compared with those in grade I/II. Transfection with miR-370 mimics inhibited the proliferation of U-251MG and U-87MG cells. Furthermore, the miR-370 levels were negatively correlated with β-catenin and positively correlated with nuclear FOXO3a. In conclusion, miR-370 inhibited the proliferation of human glioma cells by regulating the levels of β-catenin and the activation of FOXO3a, suggesting that miR-370 was a tumor suppressor in the progression of human astrocytoma and glioblastoma cells.

Sphingosine kinase 1 mediates diabetic renal fibrosis via NF-κB signaling pathway: involvement of CK2α

Sphingosine kinase 1 (SphK1) plays a pivotal role in regulating diabetic renal fibrotic factors such as fibronectin (FN) and intercellular adhesion molecule-1 (ICAM-1). Especially, activation of SphK1 is closely linked to the body inflammatory reaction. Casein kinase 2α subunit (CK2α), a protein kinase related to inflammatory reaction, influences diabetic renal fibrosis and expressions of FN and ICAM-1 via NF-κB pathway. However, the mechanism by which SphK1 mediates diabetic renal fibrosis has not yet fully elucidated. The current study is aimed to investigate if SphK1 mediates diabetic renal fibrotic pathological process via inflammatory pathway and activation of CK2α. The following findings were observed: (1) Expressions of SphK1 were upregulated in kidneys of diabetic mice and rats; (2) Knockdown of SphK1 expression suppressed high glucose (HG)-induced NF-κB nuclear translocation and expressions of FN and ICAM-1; (3) Compared with C57 diabetic mice, SphK1-/- diabetic mice exhibited less renal fibrotic lesions, FN accumulation and NF-κB nuclear accumulation in glomeruli of kidneys; (4) SphK1 mediated phosphorylation of CK2α, while CK2α knockdown depressed SphK1-induced activation of NF-κB pathway. This study indicates the essential role of SphK1 in regulating activation of CK2α and diabetic renal fibrotic pathological process via NF-κB.

Icariside II induces cell cycle arrest and apoptosis in human glioblastoma cells through suppressing Akt activation and potentiating FOXO3a activity

Glioblastoma multiforme (GBM) is the most common primary malignant brain tumor, and currently chemotherapeutic options for GBM are very limited. Given the poor prognosis, the development of novel anti-GBM agents is quite urgent. Using two human glioma cells (U87 and A172 cells), we demonstrated that Icariside II (ICA II), an active flavonoid compound derived from Epimedium koreanum, could inhibit GBM cell growth in a dose dependent manner. Wound healing data suggested that ICA II also inhibited the migration of human glioma cells. Mechanistically, ICA II induced apoptosis and cell cycle arrest, and this cytotoxic effect was dependent on the reduction of Forkhead box O3a(FOXO3a) phosphorylation mediated by Akt and the enrichment of nuclear FOXO3a, which initiated the transcription of p21/p27. Importantly, the cytotoxic effect induced by ICA II could be reversed by silencing the expression of FOXO3a, suggesting the critical role of FOXO3a in this process. Taken together, we propose ICA II as a potential novel anti-GBM candidate with a mechanism of inhibiting cell proliferation and inducing apoptosis through suppressing Akt activation and potentiating FOXO3a activity.

Overexpression of sphingosine kinase 1 is predictive of poor prognosis in human breast cancer

Sphingosine kinase 1 (SPHK1) is a bioactive lipid mediator that has been identified as a biomarker in various cancers and is considered to play an important role in tumor progression. In the present study, the expression level of SPHK1 was examined in breast cancer clinical specimens, and its association with patient survival was investigated to clarify the clinical significance of SPHK1 in breast cancer. SPHK1 mRNA expression was increased in breast cancer tissues compared with that in matched adjacent breast tissues in 19 of 32 paired tissue specimens (59.4%). Immunohistochemical analysis of 122 breast cancer cases revealed that the expression levels of SPHK1 were upregulated in 64 tumor tissues (52.5%), and increased expression levels of the protein were significantly associated with the presence of lymph node metastasis (P=0.0016), number of positive lymph nodes (P=0.0268) and presence of distant metastasis (P=0.0097). Increased SPHK1 protein expression was also associated with human epidermal growth factor receptor 2 status (P=0.0100), initial symptoms (P=0.0025) and tumor location (P=0.0457). Patients with increased SPHK1 protein expression had shorter overall survival and disease-free survival times compared with patients with lower SPHK1. Univariate and multivariate analyses indicated that high SPHK1 expression may be a poor prognostic factor. These results indicated that SPHK1 may perform an important role in breast cancer and may be a predictive factor in patients with breast cancer.

Reduction of COX-2 through modulating miR-124/SPHK1 axis contributes to the antimetastatic effect of alpinumisoflavone in melanoma

Alpinumisoflavone (AIF) is a naturally occurring flavonoid that is a major bioactive component of the medicinal plant Derris eriocarpa. In this study we evaluated the antimetastatic effect of AIF and investigated the underlying mechanism of action using in vitro and in vivo models of melanoma. We found that AIF impaired the metastatic potential of A375 and SK-MEL-1 human melanoma cells by promoting cell differentiation as assessed by melanin content, protoporphyrin IX accumulation, and tissue transglutaminase activity. In addition, AIF inhibited cell adhesion, migration, and invasion in melanoma cells. We found that AIF treatment decreased cyclooxygenase-2 (COX-2) expression, and COX-2 overexpression attenuated the inhibitory effects of AIF on the metastatic behaviors of melanoma cells. AIF dose-dependently increased microRNA-124 (miR-124) levels and decreased levels of sphingosine kinase 1 (SPHK1), a target of miR-124. In a mouse model of melanoma, AIF suppressed lung metastasis. Taken together, our findings suggest that AIF inhibits metastasis in melanoma by modulating COX-2 expression, at least in part, through targeting the miR-124/SphK1 axis. Our study provides evidence that AIF may be useful as an antimetastatic agent in the treatment of melanoma.

The role of sphingolipid signalling in diabetes‑associated pathologies (Review)

Sphingosine kinase (SphK) is an important signalling enzyme that catalyses the phosphorylation of sphingosine (Sph) to form sphingosine‑1‑phosphate (S1P). The multifunctional lipid, S1P binds to a family of five G protein-coupled receptors (GPCRs). As an intracellular second messenger, S1P activates key signalling cascades responsible for the maintenance of sphingolipid metabolism, and has been implicated in the progression of cancer, and the development of other inflammatory and metabolic diseases. SphK and S1P are critical molecules involved in the regulation of various cellular metabolic processes, such as cell proliferation, survival, apoptosis, adhesion and migration. There is strong evidence supporting the critical roles of SphK and S1P in the progression of diabetes mellitus, including insulin sensitivity and insulin secretion, pancreatic β‑cell apoptosis, and the development of diabetic inflammatory state. In this review, we summarise the current state of knowledge for SphK/S1P signalling effects, associated with the development of insulin resistance, pancreatic β‑cell death and the vascular complications of diabetes mellitus.

Sphingolipids in mitochondria

Sphingolipids are bioactive lipids found in cell membranes that exert a critical role in signal transduction. In recent years, it has become apparent that sphingolipids participate in growth, senescence, differentiation and apoptosis. The anabolism and catabolism of sphingolipids occur in discrete subcellular locations and consist of a strictly regulated and interconnected network, with ceramide as the central hub. Altered sphingolipid metabolism is linked to several human diseases. Hence, an advanced knowledge of how and where sphingolipids are metabolized is of paramount importance in order to understand the role of sphingolipids in cellular functions. In this review, we provide an overview of sphingolipid metabolism. We focus on the distinct pathways of ceramide synthesis, highlighting the mitochondrial ceramide generation, transport of ceramide to mitochondria and its role in the regulation of mitochondrial-mediated apoptosis, mitophagy and implications to disease. We will discuss unanswered questions and exciting future directions. This article is part of a Special Issue entitled: Lipids of Mitochondria edited by Guenther Daum.

Sphingolipids in spinal cord injury

Spinal cord injury (SCI) is a debilitating condition that affects millions of individuals worldwide. Despite progress over the last few decades, the molecular mechanisms of secondary SCI that continue to occur days and weeks after the original trauma remain poorly understood. As a result, current therapies for SCI are only marginally effective. Sphingolipids, a diverse class of bioactive lipids, have been shown to regulate SCI repair and key secondary injury processes such as apoptosis, ischemia and inflammation. This review will discuss the numerous roles of sphingolipids and highlight the potential of sphingolipid-targeted therapies for SCI.

RICTOR involvement in the PI3K/AKT pathway regulation in melanocytes and melanoma

Several studies have highlighted the importance of the PI3K pathway in melanocytes and its frequent over-activation in melanoma. However, little is known about regulation of the PI3K pathway in melanocytic cells. We showed that normal human melanocytes are less sensitive to selective PI3K or mTOR inhibitors than to dual PI3K/mTOR inhibitors. The resistance to PI3K inhibitor was due to a rapid AKT reactivation limiting the inhibitor effect on proliferation. Reactivation of AKT was linked to a feedback mechanism involving the mTORC2 complex and in particular its scaffold protein RICTOR. RICTOR overexpression in melanocytes disrupted the negative feedback, activated the AKT pathway and stimulated clonogenicity highlighting the importance of this feedback to restrict melanocyte proliferation. We found that the RICTOR locus is frequently amplified and overexpressed in melanoma and that RICTOR over-expression in NRAS-transformed melanocytes stimulates their clonogenicity, demonstrating that RICTOR amplification can cooperate with NRAS mutation to stimulate melanoma proliferation. These results show that RICTOR plays a central role in PI3K pathway negative feedback in melanocytes and that its deregulation could be involved in melanoma development.

The SphKs/S1P/S1PR1 axis in immunity and cancer: more ore to be mined

Over the past two decades, huge amounts of research were launched to understand the functions of sphingosine. Many pathways were uncovered that convey the relative functions of biomacromolecules. In this review, we discuss the recent advances of the role of the SphKs/S1P/S1PR1 axis in immunity and cancer. Finally, we investigate the therapeutic potential of new drugs that target S1P signaling in cancer therapy.

Extracellular Vesicles and MicroRNAs: Their Role in Tumorigenicity and Therapy for Brain Tumors

MicroRNAs are small non-coding RNAs which mediate post-transcriptional gene regulation. Recently, microRNAs have also been found to be localized to the extracellular space, often encapsulated in secreted extracellular vesicles (EVs). This tandem of EVs and tissue-specific expressed/secreted microRNAs that can be taken up by neighboring or distant recipient cells, leading to changes in gene expression-suggests a cell-specialized role in physiological and pathological conditions. The complexity of solid tumors and their distinct pathophysiology relies on interactive communications between the various cell types in the neoplasm (tumor, endothelial, or macrophages, for instance). Understanding how such EV/microRNA-mediated communication occurs may actually lead to avenues for therapeutic exploitation and/or intervention, particularly for the most formidable cancers, such as those in the brain. In this review, the role of microRNAs/EVs in brain tumors will be discussed with emphasis on how these molecules could be utilized for tumor therapy.

CONSORT: Sam68 Is Directly Regulated by MiR-204 and Promotes the Self-Renewal Potential of Breast Cancer Cells by Activating the Wnt/Beta-Catenin Signaling Pathway

Breast cancer stem cells (BCSCs) are considered to be responsible for recurrence in breast cancer. The 68 kDa Src-associated protein in mitosis (Sam68) has been linked to the development and progression of breast cancer; however, the posttranscriptional regulation and role of Sam68 in BCSC self-renewal remain unclear.Sam68 was ectopically overexpressed or knocked down using a siRNA; the self-renewal potential of breast cancer cell lines was assessed using flow cytometry, in vitro mammosphere culture and a xenograft model in NOD/SCID mice. Activation of beta-catenin was assessed by immunohistochemical staining, Western blotting, and luciferase reporter gene assays. The ArrayExpress dataset GSE45666 was used to identify conserved microRNAs downregulated in breast cancer; real-time PCR, Western blotting, luciferase reporter assay, and xenografted tumor model were used to confirm miR-204 regulated Sam68.We found that endogenous Sam68 expression correlated positively with the self-renewal potential of breast cancer cell lines. Overexpression of Sam68 promoted, whereas knockdown reduced, breast cancer cell self-renewal potential in vitro and tumorigenicity in vivo. The Wnt/beta-catenin pathway was identified as a functional mediator of Sam68-induced self-renewal in SKBR-3 and MCF-7 cells. Furthermore, miR-204 was found to be frequently downregulated in human breast cancer and confirmed to directly target Sam68; miR-204 inhibited the self-renewal of breast cancer cell lines by targeting and suppressing Sam68.Our study reveals that Sam68 is regulated by miR-204 and may play an important role in the self-renewal of BCSCs via activating the Wnt/beta-catenin pathway. Sam68 may represent a novel therapeutic target for breast cancer.

N-cadherin promotes epithelial-mesenchymal transition and cancer stem cell-like traits via ErbB signaling in prostate cancer cells

N-cadherin has been reported to be upregulated and associated with metastasis and poor prognosis in prostate cancer patients, however the underlying mechanism still remains puzzling. In the present study, we found that upregulation of N-cadherin enhanced, while downregulation of N-cadherin impaired the invasion, migration, and epithelial to mesenchymal transition (EMT) of prostate cancer (PCa) cells. Overexpression of N-cadherin increased the efficiency of colony and tumor spheroid formation and the stemness factor expression (including c-Myc, Klf4, Sox2 and Oct4), and vice versa. Furthermore, microarray analysis and western blot analysis mechanistically proved that N-cadherin activated ErbB signaling pathway by upregulating the expression of Grb2, pShc and pERK1/2. Importantly, the regulation of N-cadherin on EMT and stemness was counteracted by lapatinib, a specific ErbB signaling pathway inhibitor. Collectively, these findings demonstrate that N-cadherin regulates EMT and stemness of PCa cells via activating ErbB signaling pathway, which indicates the pivotal role of N-cadherin/ErbB axis in the metastasis of prostate cancer.

Regulation of Bim in Health and Disease

The BH3-only Bim protein is a major determinant for initiating the intrinsic apoptotic pathway under both physiological and pathophysiological conditions. Tight regulation of its expression and activity at the transcriptional, translational and post-translational levels together with the induction of alternatively spliced isoforms with different pro-apoptotic potential, ensure timely activation of Bim. Under physiological conditions, Bim is essential for shaping immune responses where its absence promotes autoimmunity, while too early Bim induction eliminates cytotoxic T cells prematurely, resulting in chronic inflammation and tumor progression. Enhanced Bim induction in neurons causes neurodegenerative disorders including Alzheimer's, Parkinson's and Huntington's diseases. Moreover, type I diabetes is promoted by genetically predisposed elevation of Bim in β-cells. On the contrary, cancer cells have developed mechanisms that suppress Bim expression necessary for tumor progression and metastasis. This review focuses on the intricate network regulating Bim activity and its involvement in physiological and pathophysiological processes.

Amyloid-β induced astrocytosis and astrocyte death: Implication of FoxO3a-Bim-caspase3 death signaling

Astrocytes, the main element of the homeostatic system in the brain, are affected in various neurological conditions including Alzheimer's disease (AD). A common astrocytic reaction in pathological state is known as astrocytosis which is characterized by a specific change in astrocyte shape due to cytoskeletal remodeling, cytokine secretion and cellular proliferation. Astrocytes also undergo apoptosis in various neurological conditions or in response to toxic insults. AD is pathologically characterized by progressive deposition of amyloid-β (Aβ) in senile plaques, intraneuronal neurofibrillary tangles, synaptic dysfunction and neuron death. Astrocytosis and astrocyte death have been reported in AD brain as well as in response to Aβ in vitro. However, how astrocytes undergo both proliferation and death in response to Aβ remains elusive. In this study, we used primary cultures of cortical astrocytes and exposed them to various doses of oligomeric Aβ. We found that cultured astrocytes proliferate and manifest all signs of astrocytosis at a low dose of Aβ. However, at high dose of Aβ the activated astrocytes undergo apoptosis. Astrocytosis was also noticed in vivo in response to Aβ in the rat brain. Next, we investigated the mechanism of astrocyte apoptosis in response to a high dose of Aβ. We found that death of astrocyte induced by Aβ requires a set of molecules that are instrumental for neuron death in response to Aβ. It involves activation of Forkhead transcription factor Foxo3a, induction of its pro-apoptotic target Bim and activation of its downstream molecule, caspase3. Hence, this study demonstrates that the concentration of Aβ decides whether astrocytes do proliferate or undergo apoptosis via a mechanism that is required for neuron death.

Phosphatase and Tensin Homologue: Novel Regulation by Developmental Signaling

Phosphatase and tensin homologue (PTEN) is a critical cell endogenous inhibitor of phosphoinositide signaling in mammalian cells. PTEN dephosphorylates phosphoinositide trisphosphate (PIP3), and by so doing PTEN has the function of negative regulation of Akt, thereby inhibiting this key intracellular signal transduction pathway. In numerous cell types, PTEN loss-of-function mutations result in unopposed Akt signaling, producing numerous effects on cells. Numerous reports exist regarding mutations in PTEN leading to unregulated Akt and human disease, most notably cancer. However, less is commonly known about nonmutational regulation of PTEN. This review focuses on an emerging literature on the regulation of PTEN at the transcriptional, posttranscriptional, translational, and posttranslational levels. Specifically, a focus is placed on the role developmental signaling pathways play in PTEN regulation; this includes insulin-like growth factor, NOTCH, transforming growth factor, bone morphogenetic protein, wnt, and hedgehog signaling. The regulation of PTEN by developmental mediators affects critical biological processes including neuronal and organ development, stem cell maintenance, cell cycle regulation, inflammation, response to hypoxia, repair and recovery, and cell death and survival. Perturbations of PTEN regulation consequently lead to human diseases such as cancer, chronic inflammatory syndromes, developmental abnormalities, diabetes, and neurodegeneration.

Silencing of miR-21 sensitizes CML CD34+ stem/progenitor cells to imatinib-induced apoptosis by blocking PI3K/AKT pathway

BCR-ABL tyrosine kinase inhibitor imatinib fails to eradicate leukemia stem cells (LSCs), the underlying mechanisms maintaining CML LSCs remain poorly understood. Here, we showed that transient inhibition of miR-21 by antagomiR-21 markedly increased imatinib-induced apoptosis in CML, but not normal CD34+ stem/progenitor cells. Furthermore, PI3K inhibitors also significantly sensitized CML CD34+ cells to imatinib-induced apoptosis. MiR-21 or PI3K inhibitor in combination with imatinib treatment significantly decreased AKT phosphorylation and c-Myc expression than either agent did alone, but did not affect Bim and Bcl-6 expresssion. These findings indicate that miR-21 is required for maintaining the imatinib-resistant phenotype of CML CD34+ cells through PI3K/AKT signaling pathway, thus providing the basis for a promising therapeutic approach to eliminate CML LSCs.

Activation of sphingosine kinase 2 by endoplasmic reticulum stress ameliorates hepatic steatosis and insulin resistance in mice

The endoplasmic reticulum (ER) is the principal organelle in the cell for protein folding and trafficking, lipid synthesis, and cellular calcium homeostasis. Perturbation of ER function results in activation of the unfolded protein response (UPR) and is implicated in abnormal lipid biosynthesis and development of insulin resistance. In this study, we investigated whether transcription of sphingosine kinase (Sphk)2 is regulated by ER stress-mediated UPR pathways. Sphk2, a major isotype of sphingosine kinase in the liver, was transcriptionally up-regulated by tunicamycin and lipopolysaccharides. Transcriptional regulation of Sphk2 was mediated by activation of activating transcription factor (ATF)4 as demonstrated by promoter assays, immunoblotting, and small interfering RNA analyses. In primary hepatocytes, adenoviral Sphk2 expression elevated cellular sphingosine 1 phosphate (S1P) and activated protein kinase B phosphorylation, with no alteration of insulin receptor substrate phosphorylation. Hepatic overexpression of Sphk2 in mice fed a high-fat diet (HFD) led to elevated S1P and reduced ceramide, sphingomyelin, and glucosylceramide in plasma and liver. Hepatic accumulation of lipid droplets by HFD feeding was reduced by Sphk2-mediated up-regulation of fatty acid (FA) oxidizing genes and increased FA oxidation in liver. In addition, glucose intolerance and insulin resistance were ameliorated by improved hepatic insulin signaling through Sphk2 up-regulation.

CONCLUSION

Sphk2 is transcriptionally up-regulated by acute ER stress through activation of ATF4 and improves perturbed hepatic glucose and FA metabolism.

Switching the sphingolipid rheostat in the treatment of diabetes and cancer comorbidity from a problem to an advantage

Cancer and diabetes are among the most common diseases in western societies. Epidemiological studies have shown that diabetic patients have a significantly higher risk of developing a number of different types of cancers and that individuals with comorbidity (cancer and diabetes/prediabetes) have a poorer prognosis relative to nondiabetic cancer patients. The increasing frequency of comorbidity of cancer and diabetes mellitus, mainly type 2 diabetes, has driven the development of therapeutic interventions that target both disease states. There is strong evidence to suggest that balancing the sphingolipid rheostat, ceramide--sphingosine--sphingosine-1-phosphate (S1P) is crucial in the prevention of diabetes and cancer and sphingosine kinase/S1P modulators are currently under development for the treatment of cancer and diabetes. This paper will highlight some of the complexities inherent in the use of the emerging sphingosine kinase/S1P modulators in the treatment of comorbidity of diabetes and cancer.

High expression of sphingosine kinase 1 is associated with poor prognosis in nasopharyngeal carcinoma

It has been reported that sphingosine kinase 1 (SPHK1), an oncogenic enzyme, was involved in the development and progression of a number of human cancers. However, the role of SPHK1 in nasopharyngeal carcinoma (NPC) is largely unknown. The present study aimed to characterize the expression of SPHK1 in human NPC and evaluate its clinical significance. Real-time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) and Western blot analyses showed that the expression of SPHK1 mRNA and protein in NPC specimens was significantly higher than that in non-tumorous nasopharyngeal mucosa biopsies. Immunohistochemistry (IHC) was conducted to characterize the expression pattern of SPHK1 in 142 archived paraffin-embedded NPC specimens. Statistical analyses revealed that high levels of SPHK1 expression were associated with the clinical stages, locoregional recurrence and distant metastasis of NPC. NPC patients with high levels of SPHK1 expression had shorter survival time, whereas those with lower levels of SPHK1 expression survived longer. Moreover, multivariate analysis suggested that SPHK1 up-regulation was an independent prognostic factor for NPC. Our results suggest for the first time that SPHK1 is involved in the development and progression of NPC, which can be used as a useful prognostic marker for NPC patients and may be an effective target for treating NPC.

MicroRNA expression profiles in rats with selenium deficiency and the possible role of the Wnt/β-catenin signaling pathway in cardiac dysfunction

Selenium deficiency is a causative factor in heart failure and microRNAs (known as miRNAs or miRs) play an important role in numerous cardiovascular diseases. However, the changes of miRNA expression during selenium deficiency and whether selenium deficiency is involved in cardiac dysfunction remain unclear. In the present study, miRNA expression profiling was carried out in normal rats, selenium-deficient rats and selenium-supplemented rats by miRNA microarray. Cardiac function was evaluated by analyzing the plasma brain natriuretic peptide level, echocardiographic parameters and hemodynamic parameters. Cardiac glutathione peroxidase activity was assessed by spectrophotometry. The histological changes were examined by hematoxylin and eosin staining. Electrocardiograph was used to test the arrhythmia. The differentially expressed miRNAs were verified by reverse transcription-polymerase chain reaction. Additionally, the underlying mechanism associated with the Wnt/β-catenin signaling pathway was further explored. The cardiac dysfunction of the rat with selenium deficiency was mainly associated with five upregulated miRNAs, which were miR-374, miR-16, miR-199a-5p, miR-195 and miR-30e*, and three downregulated miRNAs, which were miR-3571, miR-675 and miR-450a*. Among these, the expression of miR-374 was the highest, which may be of vital importance in rats with selenium deficiency. In conclusion, the possible mechanism of selenium deficiency-induced cardiac dysfunction was associated with the Wnt/β-catenin signaling pathway.

Belonging to a network--microRNAs, extracellular vesicles, and the glioblastoma microenvironment

The complexity of glioblastoma multiforme (GBM) and its distinct pathophysiology belong to a unique brain microenvironment and its cellular interactions. Despite extensive evidence of a role for microRNAs in GBM cells, little is known about microRNA-dependent communication between different cellular compartments of the microenvironment that may contribute to the tumor phenotype. While the majority of microRNAs are found intracellularly, a significant number of microRNAs have been observed outside of cells, often encapsulated in secreted extracellular vesicles (EVs). The function of these circulating/secreted microRNAs has not been explored in the context of the brain tumor microenvironment. Establishing how microRNAs are involved in the regulation of oncogenic signaling networks between tumor cells and stroma is likely to add a needed additional layer of complexity to the tumor network, consisting of intercellular communication. More importantly, microRNA/EV signaling may provide an additional therapeutic target for this deadly disease.

Double-negative feedback loop between ZEB2 and miR-145 regulates epithelial-mesenchymal transition and stem cell properties in prostate cancer cells

The invasion and metastasis of tumors are triggered by an epithelial to mesenchymal transition (EMT), which is regulated by microRNAs (miRNAs). EMT also promotes malignant tumor progression and the maintenance of the stem cell property, which endows cancer cells with the capabilities of self-renewal and immortalized proliferation. The transcriptional repressor zinc-finger E-box binding homeobox 2 (ZEB2), as an EMT activator, might be an important promoter of metastasis in some tumors. Here, we report that ZEB2 directly represses the transcription of miR-145, which is a strong repressor of EMT. In turn, ZEB2 is also a direct target of miR-145. Further, our findings show that the downregulation of ZEB2 not only represses invasion, migration, EMT, and the stemness of prostate cancer (PCa) cells, but also suppresses the capability of PC-3 cells to invade bone in vivo. Importantly, the expression level of ZEB2 as revealed by immunohistochemical analysis is positively correlated to bone metastasis, the serum free PSA level, the total PSA level, and the Gleason score in PCa patients and is negatively correlated with miR-145 expression in primary PCa specimens. Thus, our findings demonstrate a double-negative feedback loop between ZEB2 and miR-145 and indicate that the ZEB2/miR-145 double-negative feedback loop plays a significant role in the control of EMT and stem cell properties during the bone metastasis of PCa cells. These results suggest that the double-negative feedback loop between ZEB2 and miR-145 contributes to PCa progression and metastasis and might have therapeutic relevance for the bone metastasis of PCa.

Sphingosine-1-phosphate and its effect on glucose deprivation/glucose reload stress: from gene expression to neuronal survival

Sphingosine kinase-1 (Sphk1-1, EC 2.7.1.91) is a regulator of pro-survival signalling, and its alterations have been observed in Alzheimer’s disease, brain ischemia and other neurological disorders. In this study we addressed the question whether Sphk1 and its product, sphingosine-1-phosphate (S1P), play a significant role in glucose deprivation (GD)/glucose reload (GR) stress in hippocampal neuronal cells (HT22). It was found that GD (6 h) followed by 24 h of GR evoked enhancement of the free radical level and neuronal HT22 cell death. Moreover, the significantly stronger gene expression for the pro-apoptotic Bax protein and down-regulation of the anti-apoptotic Bcl-2 and Bcl-X_L proteins were observed. Concomitantly, this stress up-regulated: gene expression, protein level and activity of Sphk1. Exogenous S1P at 1 μM concentration and the other agonists of the S1P1 receptor (SEW 2871 and P-FTY720) enhanced HT22 cell viability affected by GD/GR stress. This mechanism is mediated by S1P receptor(s) signalling and by the activation of gene expression for Bcl-2 and Bcl-X_L. Summarising, our data suggest that sphingolipid metabolism may play an important role in the early events that take place in neuronal cell survival/death under GD/GR stress. Our data demonstrate that exogenous S1P, through the activation of specific receptors S1P1 and S1P3 signalling pathways, regulates the gene expression for anti-apoptotic proteins and enhances neuronal cell survival affected by GD/GR stress.

Knockdown of sphingosine kinase 1 inhibits the migration and invasion of human rheumatoid arthritis fibroblast-like synoviocytes by down-regulating the PI3K/AKT activation and MMP-2/9 production in vitro

To investigate the potential regulation of sphingosine kinase 1 (SPHK1) on the migration, invasion, and matrix metalloproteinase (MMP) expression in human rheumatoid arthritis fibroblast-like synoviocytes (RA-FLS). RA-FLS were transfected control siRNA or SPHK1 siRNA. The migration and invasion of unmanipulated control, control siRNA or SPHK1 siRNA- transfected RA-FLS in vitro were measured by the transwell system. The relative levels of SPHK1, PI3K, and AKT as well as AKT phosphorylation in RA-FLS were determined by Western blot. The levels of MMP-2/9 secreted by RA-FLS were detected by ELISA. Knockdown of SPHK1 significantly inhibited the spontaneous migration and invasion of RA-FLS, accompanied by significantly reduced levels of PI3K expression and AKT phosphorylation. Similarly, treatment with LY294002, an inhibitor of the PI3K/AKT pathway, inhibited the migration and invasion of RA-FLS. Knockdown of SPHK1 and treatment with the inhibitor synergistically inhibited the migration and invasion of RA-FLS, by further reducing the levels of PI3K expression and AKT phosphorylation. In addition, knockdown of SPHK1 or treatment with LY294002 inhibited the secretion of MMP-2 and MMP-9, and both synergistically reduced the production of MMP-2 and MMP-9 in RA-FLS in vitro. Knockdown of SPHK1 expression inhibits the PI3K/AKT activation, MMP-2 and MMP-9 expression, and human RA-FLS migration and invasion in vitro. Potentially, SPHK1 may be a novel therapeutic target for RA.

CD28-mediated pro-survival signaling induces chemotherapeutic resistance in multiple myeloma

Chemotherapeutic resistance remains a significant hurdle in the treatment of multiple myeloma (MM) and is significantly mediated by interactions between MM cells and stromal cells of the bone marrow microenvironment. Despite the importance of these interactions, the specific molecules and downstream signaling components involved remain incompletely understood. We have previously shown that the prototypic T-cell costimulatory receptor CD28, which is also expressed on MM cells, is a key mediator of MM survival and apoptotic resistance. Crosslinking CD28 by agonistic antibodies or myeloid dendritic cells (DC; these express the CD28 ligands CD80/CD86) prevents apoptosis caused by chemotherapy or serum withdrawal. We now report that CD28 pro-survival signaling is dependent upon downstream activation of phosphatidyl-inositol 3-kinase/Akt, inactivation of the transcription factor FoxO3a, and decreased expression of the pro-apoptotic molecule Bim. Conversely, blocking the CD28-CD80/CD86 interaction between MM cells and DC in vitro abrogates the DC's ability to protect MM cells against chemotherapy-induced death. Consistent with these observations, in vivo blockade of CD28-CD80/CD86 in the Vk*MYC murine myeloma model sensitizes MM cells to chemotherapy and significantly reduces tumor burden. Taken together, our findings suggest that CD28 is an important mediator of MM survival during stress and can be targeted to overcome chemotherapy resistance.

MiR-503 targets PI3K p85 and IKK-β and suppresses progression of non-small cell lung cancer

A microRNA usually has the ability to coordinately repress multiple target genes and therefore are associated with many pathological conditions such as human cancer. Our understanding of the biological roles of microRNAs in lung cancer, however, remains incomplete. In this study, we identified miR-503 as a tumor-suppressive microRNA in human non-small cell lung carcinoma (NSCLC), whose expression level correlates inversely with overall survival in NSCLC patients. Ectopic expression of miR-503 suppressed tumor cell proliferation and metastasis-related traits in vitro as well as in vivo, supporting a anti-cancer role of the microRNA in NSCLC progression. Mechanistic study revealed that oncogenic PI3K p85 and IKK-β were direct targets of miR-503. Overexpression of either PI3K p85 or IKK-β partially restored the malignant properties of NSCLC cells in the presence of miR-503. Taken together, our data demonstrate miR-503 inhibits the malignant phenotype of NSCLC by targeting PI3K p85 and IKK-β and might play a suppressive role in the pathogenesis of NSCLC, thus providing new insights in developing novel diagnostic and therapeutic approaches.

Sphingosine analog fingolimod (FTY720) increases radiation sensitivity of human breast cancer cells in vitro

Radiotherapy is one of the most effective therapeutic strategies for breast cancer patients, although its efficacy may be reduced by intrinsic radiation resistance of cancer cells. Recent investigations demonstrate a link between cancer cell radio-resistance and activation of sphingosine kinase (SphK1), which plays a key role in the balance of lipid signaling molecules. Sphingosine kinase (SphK1) activity can alter the sphingosine-1-phosphate (S1P)/ceramide ratio leading to an imbalance in the sphingolipid rheostat. Fingolimod (FTY720) is a novel sphingosine analog and a potent immunosuppressive drug that acts as a SphK1 antagonist, inhibits the growth, and induces apoptosis in different human cancer cell lines. We sought to investigate the in vitro radiosensitizing effects of FTY720 on the MDA-MB-361 breast cancer cell line and to assess the effects elicited by radiation and FTY720 combined treatments. We found that FTY720 significantly increased anti-proliferative and pro-apoptotic effects induced by a single dose of ionizing radiation while causing autophagosome accumulation. At the molecular level, FTY720 significantly potentiated radiation effects on perturbation of signaling pathways involved in regulation of cell cycle and apoptosis, such as PI3K/AKT and MAPK. In conclusion, our data highlight a potent radiosensitizing effect of FTY720 on breast cancer cells and provide the basis of novel therapeutic strategies for breast cancer treatment.