Targeting the ceramide system in cancer

The Interplay between Oxidative Stress and Sphingolipid Metabolism in Endometrial Cancer

Endometrial cancer is one of the most common malignancies in women. Sphingolipids, a group of lipids, play a key role in cancer biology. Cancer cells often exhibit abnormal redox homeostasis characterized by elevated levels of reactive oxygen species (ROS). Emerging evidence suggests that ceramides are involved in inhibiting proliferation and inducing apoptosis through ROS production. However, there is no data on the relationship between sphingolipid metabolism and oxidative status in endometrial cancer. The present study aims to assess the content of individual sphingolipids and oxidative status in healthy women and those with endometrial cancer. Sphingolipid analysis was performed using mass spectrometry. Total oxidative status (TOS) and total antioxidant capacity (TAC) were assessed colorimetrically. Our results showed a significant increase in the levels of all measured sphingolipids in cancer tissues compared to healthy endometrium. Additionally, a significant decrease in the S1P/ceramide ratio (sphingolipid rheostat) was observed in cancer patients, particularly for C14:0-Cer, C16:0-Cer, C18:1-Cer, C22:0-Cer, and C24:0-Cer. Furthermore, increased TOS and decreased TAC were found in cancer patients compared to healthy women. Significant correlations were observed between the levels of individual sphingolipids and oxidative status, with the strongest correlation noted between C22:0-Cer and TOS (r = 0.64). We conclude that endometrial cancer is characterized by profound changes in sphingolipid metabolism, contributing to oxidative dysregulation and tumor progression.

Metabolomics analyses reveal the crucial role of ERK in regulating metabolic pathways associated with the proliferation of human cutaneous T-cell lymphoma cells treated with Glabridin

Cutaneous T-cell lymphomas (CTC) are a heterogeneous group of T-cell lymphoproliferative malignancies of the skin with limited treatment options, increased resistance and remission. Metabolic reprogramming is vital in orchestrating the uncontrolled growth and proliferation of cancer cells. Importantly, deregulated signalling plays a significant role in metabolic reprogramming. Considering the crucial role of metabolic reprogramming in cancer-cell growth and proliferation, target identification and the development of novel and multi-targeting agents are imperative. The present study explores the underlying mechanisms and metabolic signalling pathways associated with Glabridin mediated anti-cancer actions in CTCL. Our results show that Glabridin significantly inhibits the growth of CTCL cells through induction of programmed cell death (PCD) such as apoptosis, autophagy and necrosis. Interestingly, results further show that Glabridin induces PCD in CTCL cells by targeting MAPK signalling pathways, particularly the activation of ERK. Further, Glabridin also sensitized CTCL cells to the anti-cancer drug, bortezomib. Importantly, LC-MS-based metabolomics analyses further showed that Glabridin targeted multiple metabolites and metabolic pathways intricately involved in cancer cell growth and proliferation in an ERK-dependent fashion. Overall, our findings revealed that Glabridin induces PCD and attenuates the expression of regulatory proteins and metabolites involved in orchestrating the uncontrolled proliferation of CTCL cells through ERK activation. Therefore, Glabridin possesses important features of an ideal anti-cancer agent.

Fanning the Flames of Endoplasmic Reticulum (ER) Stress: Can Sphingolipid Metabolism Be Targeted to Enhance ER Stress-Associated Immunogenic Cell Death in Cancer?

The three arms of the unfolded protein response (UPR) surveil the luminal environment of the endoplasmic reticulum (ER) and transmit information through the lipid bilayer to the cytoplasm to alert the cell of stress conditions within the ER lumen. That same lipid bilayer is the site of de novo synthesis of phospholipids and sphingolipids. Thus, it is no surprise that lipids are modulated by and are modulators of ER stress. Given that sphingolipids have both prosurvival and proapoptotic effects, they also exert opposing effects on life/death decisions in the face of prolonged ER stress detected by the UPR. In this review, we will focus on several recent studies that demonstrate how sphingolipids affect each arm of the UPR. We will also discuss the role of sphingolipids in the process of immunogenic cell death downstream of the protein kinase RNA-like endoplasmic reticulum kinase (PERK)/eukaryotic initiating factor 2α (eIF2α) arm of the UPR. Furthermore, we will discuss strategies to target the sphingolipid metabolic pathway that could potentially act synergistically with agents that induce ER stress as novel anticancer treatments. SIGNIFICANCE STATEMENT: This review provides the readers with a brief discussion of the sphingolipid metabolic pathway and the unfolded protein response. The primary focus of the review is the mechanism(s) by which sphingolipids modulate the endoplasmic reticulum (ER) stress response pathways and the critical role of sphingolipids in the process of immunogenic cell death associated with the ER stress response.

Lipids as Targets for Renal Cell Carcinoma Therapy

Kidney cancer is among the top ten most common cancers to date. Within the kidney, renal cell carcinoma (RCC) is the most common solid lesion occurring. While various risk factors are suspected, including unhealthy lifestyle, age, and ethnicity, genetic mutations seem to be a key risk factor. In particular, mutations in the von Hippel-Lindau gene (Vhl) have attracted a lot of interest since this gene regulates the hypoxia inducible transcription factors HIF-1α and HIF-2α, which in turn drive the transcription of many genes that are important for renal cancer growth and progression, including genes involved in lipid metabolism and signaling. Recent data suggest that HIF-1/2 are themselves regulated by bioactive lipids which make the connection between lipids and renal cancer obvious. This review will summarize the effects and contributions of the different classes of bioactive lipids, including sphingolipids, glycosphingolipids, eicosanoids, free fatty acids, cannabinoids, and cholesterol to renal carcinoma progression. Novel pharmacological strategies interfering with lipid signaling to treat renal cancer will be highlighted.

A method for quantifying hepatic and intestinal ceramides on mice by UPLC-MS/MS

BACKGROUND

Ceramide is one type of sphingolipids, is associated with the occurrence of metabolic diseases, including obesity, diabetes, cardiovascular disease, cancer, and nonalcoholic fatty liver disease. Dihydroceramide, the direct precursors of ceramide, which is converted to ceramide with the dihydroceramide desaturase, is recently regarded as involving in various biological processes and metabolic diseases. The liver and gut ceramide levels are interactional in pathophysiological condition, quantifying hepatic and intestinal ceramide levels become indispensable. The aim of this study is to establish a rapid method for the determination of ceramides including dihydroceramides in liver and small intestinal tissues for researching the mechanisms of ceramide related diseases.

METHODS

The levels of Cer d18:1/2:0, Cer d18:1/6:0, Cer d18:1/12:0, Cer d18:1/14:0, Cer d18:1/16:0, Cer d18:1/17:0, Cer d18:1/18:0, Cer d18:1/20:0, Cer d18:1/22:0, Cer d18:1/24:1, Cer d18:1/24:0, dHCer d18:0/12:0, dHCer d18:0/14:0, dHCer d18:0/16:0, dHCer d18:0/18:0, dHCer d18:0/24:1 and dHCer d18:0/24:0 in mice liver and small intestine were directly quantified by ultra-high performance liquid chromatography-tandem mass spectrometry after methanol extraction. In detail, liver or small intestine tissues were thoroughly homogenized with methanol. The resultant ceramides were separated on a Waters BEH C18 column using gradient elution within 10 min. Positive electrospray ionization with multiple reaction monitoring was applied to detect. In the end, the levels of ceramides in mice liver and small intestine tissues were quantified by this developed method.

RESULTS

The limits of detection and quantification of 11 ceramides and 6 dihydroceramides were 0.01-0.5 ng/mL and 0.02-1 ng/mL, respectively, and all detected ceramides had good linearities (R² > 0.997). The extraction recoveries of ceramides at three levels were within 82.32%-115.24% in the liver and within 83.21%-118.70% in the small intestine. The relative standard deviations of intra- and inter-day precision were all within 15%. The extracting solutions of the liver and small intestine could be stably stored in the autosampler 24 h at 10 °C, the lyophilized liver and small intestine for ceramides quantification could be stably stored at least 1 week at -80 °C. The ceramides and dihydroceramides in normal mice liver and small intestinal tissues analyzed by the developed method indicated that the detected 9 ceramide and 5 dihydroceramides levels were significantly different, in which Cer d18:1/16:0, Cer d18:1/22:0, Cer d18:1/24:1, Cer d18:1/24:0 and dHCer d18:0/24:1 are the main components in the liver, whereas Cer d18:1/16:0 and dHCer d18:0/16:0 accounts for the majority of proportion in the intestinal tissues.

CONCLUSION

A simple and rapid method for the quantification of 11 ceramides and 6 dihydroceramides in the animal tissues was developed and applied. The compositions of ceramides in two tissues suggested that the compositional features should to be considered when exploring the biomarkers or molecular mechanisms.

Targeting sphingosine kinase 1/2 by a novel dual inhibitor SKI-349 suppresses non-small cell lung cancer cell growth

Sphingosine kinase 1 (SphK1) and sphingosine kinase (SphK2) are both important therapeutic targets of non-small cell lung cancer (NSCLC). SKI-349 is a novel, highly efficient and small molecular SphK1/2 dual inhibitor. Here in primary human NSCLC cells and immortalized cell lines, SKI-349 potently inhibited cell proliferation, cell cycle progression, migration and viability. The dual inhibitor induced mitochondrial depolarization and apoptosis activation in NSCLC cells, but it was non-cytotoxic to human lung epithelial cells. SKI-349 inhibited SphK activity and induced ceramide accumulation in primary NSCLC cells, without affecting SphK1/2 expression. SKI-349-induced NSCLC cell death was attenuated by sphingosine-1-phosphate and by the SphK activator K6PC-5, but was potentiated by the short-chain ceramide C6. Moreover, SKI-349 induced Akt-mTOR inactivation, JNK activation, and oxidative injury in primary NSCLC cells. In addition, SKI-349 decreased bromodomain-containing protein 4 (BRD4) expression and downregulated BRD4-dependent genes (Myc, cyclin D1 and Klf4) in primary NSCLC cells. At last, SKI-349 (10 mg/kg) administration inhibited NSCLC xenograft growth in nude mice. Akt-mTOR inhibition, JNK activation, oxidative injury and BRD4 downregulation were detected in SKI-349-treated NSCLC xenograft tissues. Taken together, targeting SphK1/2 by SKI-349 potently inhibits NSCLC cell growth in vitro and in vivo.

Comprehensive review on signaling pathways of dietary saponins in cancer cells suppression

Nutrigenomics utilizes high-throughput genomic technologies to reveal changes in gene and protein levels. Excitingly, ever-growing body of scientific findings has provided sufficient evidence about the interplay between diet and genes. Cutting-edge research and advancements in genomics, epigenetics and metabolomics have deepened our understanding on the role of dietary factors in the inhibition of carcinogenesis and metastasis. Dietary saponins, a type of triterpene glycosides, are generally found in Platycodon grandifloras, Dioscorea oppositifolia, asparagus, legumes, and sea cucumber. Wealth of information has started to shed light on pleiotropic mechanistic roles of dietary saponins in cancer prevention and inhibition. In this review, we have attempted to summarize the in vitro research of dietary saponins in the last two decades by searching common databases such as Google Scholar, PubMed, Scopus, and Web of Science. The results showed that dietary saponins exerted anti-cancer activities via regulation of apoptosis, autophagy, arrest cell cycle, anti-proliferation, anti-metastasis, and anti-angiogenesis, by regulation of several critical signaling pathways, including MAPK, PI3K/Akt/mTOR, NF-κB, and VEGF/VEGFR. However, there is no data about the dosage of dietary saponins for practical anti-cancer effects in human bodies. Extensive clinical studies are needed to confirm the effectiveness of dietary saponins for further commercial and medical applications.

Neutral sphingomyelinase-2 and cardiometabolic diseases

Sphingolipids, in particular ceramides, play vital role in pathophysiological processes linked to metabolic syndrome, with implications in the development of insulin resistance, pancreatic ß-cell dysfunction, type 2 diabetes, atherosclerosis, inflammation, nonalcoholic steatohepatitis, and cancer. Ceramides are produced by the hydrolysis of sphingomyelin, catalyzed by different sphingomyelinases, including neutral sphingomyelinase 2 (nSMase2), whose dysregulation appears to underlie many of the inflammation-related pathologies. In this review, we discuss the current knowledge on the biochemistry of nSMase2 and ceramide production and its regulation by inflammatory cytokines, with particular reference to cardiometabolic diseases. nSMase2 contribution to pathogenic processes appears to involve cyclical feed-forward interaction with proinflammatory cytokines, such as TNF-α and IL-1ß, which activate nSMase2 and the production of ceramides, that in turn triggers the synthesis and release of inflammatory cytokines. We elaborate these pathogenic interactions at the molecular level and discuss the potential therapeutic benefits of inhibiting nSMase2 against inflammation-driven cardiometabolic diseases.

Cancer stem cells and ceramide signaling: the cutting edges of immunotherapy

The multipotent, self renewing "cancer stem cells" (CSCs), a small population within tumor microenvironment facilitates transformed cells to grow and propagate within the body. The CSCs are discovered as resistant to the chemotherapeutic drug with distinct immunological characteristics. In recent years, immunologically targeting CSCs have emerged as an integral part of effective and successful cancer therapy. CSCs notably exhibit dysregulation in conventional sub-cellular sphingolipid metabolism. Recently, ceramide decaying enzymes have been shown to activate alternative ceramide signaling pathways leading to reduction in efficacy of the chemotherapeutic drugs. Therefore, a control over ceramide mediated modulations of CSCs offers an attractive dimension of effective cancer treatment strategy in future. In this review, we focused on the recent findings on broad spectrum of ceramide mediated signaling in CSCs within the tumor niche and their role in potential cancer immunotherapy.

PKCζ mediated anti-proliferative effect of C2 ceramide on neutralization of the tumor microenvironment and melanoma regression

Immunotherapy, which has advantages over chemotherapy due to lesser toxicity and higher specificity, is on the rise to treat cancer. Recently, pro-apoptotic glycolipid, ceramide has emerged as a key regulator in cancer immunotherapy. The present study elucidated the potential anti-melanoma efficacy of cell-permeable, exogenous C2 ceramide on cell death and amelioration of tumor microenvironment (TME). We, for the first time, demonstrated that C2 ceramide triggered apoptosis of melanoma cells by augmenting PKCζ along with pro-inflammatory cytokines and signaling factors. C2 ceramide showed a PKCζ-mediated tumor-suppressive role in melanoma without exhibiting hepatotoxicity and nephrotoxicity. Moreover, PKCζ was revealed as one of the key regulators of Akt and ceramide during C2 ceramide-mediated apoptosis. C2 ceramide was effective in repolarization of M2 macrophage phenotype and reduction of angiogenic factors such as VEGF, VEGFR1, VEGFR2, HIF1α. Interestingly, PKCζ knockdown attenuated C2 ceramide-mediated inhibition of melanoma progression. Restoration of the Th1 type TME by C2 ceramide enhanced cytotoxic T cell-mediated killing of melanoma cells. Altogether, the study unraveled that C2 ceramide-induced PKCζ was associated with favorable immune cell functioning in TME leading to melanoma regression. Thus, our findings explored a novel mechanistic insight into C2 ceramide as a promising immunotherapeutic agent in melanoma treatment.

Role of Neutral Sphingomyelinase-2 (NSM 2) in the Control of T Cell Plasma Membrane Lipid Composition and Cholesterol Homeostasis

The activity of neutral sphingomyelinase-2 (NSM2) to catalyze the conversion of sphingomyelin (SM) to ceramide and phosphocholine at the cytosolic leaflet of plasma membrane (PM) is important in T cell receptor (TCR) signaling. We recently identified PKCζ as a major NSM2 downstream effector which regulates microtubular polarization. It remained, however, unclear to what extent NSM2 activity affected overall composition of PM lipids and downstream effector lipids in antigen stimulated T cells. Here, we provide a detailed lipidomics analyses on PM fractions isolated from TCR stimulated wild type and NSM2 deficient (ΔNSM) Jurkat T cells. This revealed that in addition to that of sphingolipids, NSM2 depletion also affected concentrations of many other lipids. In particular, NSM2 ablation resulted in increase of lyso-phosphatidylcholine (LPC) and lyso-phosphatidylethanolamine (LPE) which both govern PM biophysical properties. Crucially, TCR dependent upregulation of the important T cell signaling lipid diacylglycerol (DAG), which is fundamental for activation of conventional and novel PKCs, was abolished in ΔNSM cells. Moreover, NSM2 activity was found to play an important role in PM cholesterol transport to the endoplasmic reticulum (ER) and production of cholesteryl esters (CE) there. Most importantly, CE accumulation was essential to sustain human T cell proliferation. Accordingly, inhibition of CE generating enzymes, the cholesterol acetyltransferases ACAT1/SOAT1 and ACAT2/SOAT2, impaired TCR driven expansion of both CD4⁺ and CD8⁺ T cells. In summary, our study reveals an important role of NSM2 in regulating T cell functions by its multiple effects on PM lipids and cholesterol homeostasis.

Role of Acid Sphingomyelinase and Ceramide in Mechano-Acoustic Enhancement of Tumor Radiation Responses

Background

High-dose radiotherapy (>8-10 Gy) causes rapid endothelial cell death via acid sphingomyelinase (ASMase)-induced ceramide production, resulting in biologically significant enhancement of tumor responses. To further augment or solicit similar effects at low radiation doses, we used genetic and chemical approaches to evaluate mechano-acoustic activation of the ASMase-ceramide pathway by ultrasound-stimulated microbubbles (USMB).

Methods

Experiments were carried out in wild-type and acid sphingomyelinase (asmase) knockout mice implanted with fibrosarcoma xenografts. A cohort of wild-type mice received the ASMase-ceramide pathway inhibitor sphingosine-1-phosphate (S1P). Mice were treated with varying radiation doses, with or without a priori USMB exposure at different microbubble concentrations. Treatment response was assessed with quantitative 3D Doppler ultrasound and immunohistochemistry at baseline, and at three, 24, and 72 hours after treatment, with three to five mice per treatment group at each time point. All statistical tests were two-sided.

Results

Results confirmed an interaction between USMB and ionizing radiation at 24 hours (P < .001), with a decrease in tumor perfusion of up to 46.5% by three hours following radiation and USMB. This peaked at 24 hours, persisting for up to 72 hours, and was accompanied by extensive tumor cell death. In contrast, statistically nonsignificant and minimal tumor responses were noted in S1P-treated and asmase knockout mice for all treatments.

Conclusions

This work is the first to confirm the involvement of the ASMase-ceramide pathway in mechanotransductive vascular targeting using USMB. Results also confirm that an acute vascular effect is driving this form of enhanced radiation response, and that it can be elicited at low radiation doses (<8-10 Gy) by a priori USMB exposure.

Long and Very-Long-Chain Ceramides Correlate with A More Aggressive Behavior in Skull Base Chordoma Patients

BACKGROUND

Skull base chordomas are rare tumors arising from notochord. Sphingolipids analysis is a promising approach in molecular oncology, and it has never been applied in chordomas. Our aim is to investigate chordoma behavior and the role of ceramides.

METHODS

Ceramides were extracted and evaluated by liquid chromatography and mass spectrometry in a cohort of patients with a skull base chordoma. Clinical data were also collected and correlated with ceramide levels. Linear regression and correlation analyses were conducted.

RESULTS

Analyzing the association between ceramides level and MIB-1, total ceramides and dihydroceramides showed a strong association (r = 0.7257 and r = 0.6733, respectively) with MIB-1 staining (p = 0.0033 and p = 0.0083, respectively). Among the single ceramide species, Cer C24:1 (r = 0.8814, p ≤ 0.0001), DHCer C24:1 (r = 0.8429, p = 0.0002) and DHCer C18:0 (r = 0.9426, p ≤ 0.0001) showed a significant correlation with MIB-1.

CONCLUSION

Our lipid analysis showed ceramides to be promising tumoral biomarkers in skull base chordomas. Long- and very-long-chain ceramides, such as Cer C24:1 and DHCer C24:1, may be related to a prolonged tumor survival and aggressiveness, and the understanding of their effective biological role will hopefully shed light on the mechanisms of chordoma radio-resistance, tendency to recur, and use of agents targeting ceramide metabolism.

Role of Ceramides in Drug Delivery

Ceramides belong to the sphingolipid group of lipids, which serve as both intracellular and intercellular messengers and as regulatory molecules that play essential roles in signal transduction, inflammation, angiogenesis, and metabolic disorders such as diabetes, neurodegenerative diseases, and cancer cell degeneration. Ceramides also play an important structural role in cell membranes by increasing their rigidity, creating micro-domains (rafts and caveolae), and altering membrane permeability; all these events are involved in the cell signaling. Ceramides constitute approximately half of the lipid composition in the human skin contributing to barrier function as well as epidermal signaling as they affect both proliferation and apoptosis of keratinocytes. Incorporation of ceramides in topical preparations as functional lipids appears to alter skin barrier functions. Ceramides also appear to enhance the bioavailability of drugs by acting as lipid delivery systems. They appear to regulate the ocular inflammation signaling, and external ceramides have shown relief in the anterior and posterior eye disorders. Ceramides play a structural role in liposome formulations and enhance the cellular uptake of amphiphilic drugs, such as chemotherapies. This review presents an overview of the various biological functions of ceramides, and their utility in topical, oral, ocular, and chemotherapeutic drug delivery.

Ceramide-Graphene Oxide Nanoparticles Enhance Cytotoxicity and Decrease HCC Xenograft Development: A Novel Approach for Targeted Cancer Therapy

Despite substantial efforts to develop novel therapeutic strategies for treating hepatocellular carcinoma (HCC), the effectiveness and specificity of available drugs still require further improvement. Previous work has shown that exogenous ceramide can play a key role in inducing the apoptotic death of cancer cells, however, the poor water-solubility of this compound has hampered its use for cancer treatment. In the present study, we used polyethylene glycol (PEG) and polyethylenimine (PEI) co-conjugated ultra-small nano-GO (NGO-PEG-PEI) loaded with C6-ceramide (NGO-PEG-PEI/Cer) as a strategy for HCC treatment. We assessed the biological role of NGO-PEG-PEI/Cer, and we assessed its antitumor efficacy against HCC both in vitro and in vivo in combination with the chemotherapeutic drug sorafenib. We found that NGO-PEG-PEI significantly enhanced the cellular uptake of C6-ceramide. By investigating the mechanism of cellular delivery, we determined that the internalization of NGO-PEG-PEI/Cer progressed primarily via a clathrin-mediated mechanism. The combination of NGO-PEG-PEI/Cer and sorafenib exhibited synergy between these two drugs. Further work revealed that NGO-PEG-PEI/Cer may play a role in subverting multidrug resistance (MDR) in HCC cells by inactivating MDR and Akt signaling. NGO-PEG-PEI/Cer also significantly inhibited tumor growth and improved survival times in vivo, and the synergetic effect of NGO-PEG-PEI/Cer combined with sorafenib was also observed in drug-resistant HCC xenografts. In conclusion, our NGO-PEG-PEI nanocomposite is an effective nano-platform for loading C6-ceramide for therapeutic use in treating HCC, exhibiting high cancer cell killing potency in this tumor model. The NGO-PEG-PEI/Cer/sorafenib combination additionally represents a promising potential therapeutic strategy for the treatment of drug-resistant HCC.

A biplot correlation range for group-wise metabolite selection in mass spectrometry

Background

Analytic methods are available to acquire extensive metabolic information in a cost-effective manner for personalized medicine, yet disease risk and diagnosis mostly rely upon individual biomarkers based on statistical principles of false discovery rate and correlation. Due to functional redundancies and multiple layers of regulation in complex biologic systems, individual biomarkers, while useful, are inherently limited in disease characterization. Data reduction and discriminant analysis tools such as principal component analysis (PCA), partial least squares (PLS), or orthogonal PLS (O-PLS) provide approaches to separate the metabolic phenotypes, but do not offer a statistical basis for selection of group-wise metabolites as contributors to metabolic phenotypes.

Methods

We present a dimensionality-reduction based approach termed ‘biplot correlation range (BCR)’ that uses biplot correlation analysis with direct orthogonal signal correction and PLS to provide the group-wise selection of metabolic markers contributing to metabolic phenotypes.

Results

Using a simulated multiple-layer system that often arises in complex biologic systems, we show the feasibility and superiority of the proposed approach in comparison of existing approaches based on false discovery rate and correlation. To demonstrate the proposed method in a real-life dataset, we used LC-MS based metabolomics to determine spectrum of metabolites present in liver mitochondria from wild-type (WT) mice and thioredoxin-2 transgenic (TG) mice. We select discriminatory variables in terms of increased score in the direction of class identity using BCR. The results show that BCR provides means to identify metabolites contributing to class separation in a manner that a statistical method by false discovery rate or statistical total correlation spectroscopy can hardly find in complex data analysis for predictive health and personalized medicine.

Electronic supplementary material

The online version of this article (10.1186/s13040-019-0191-2) contains supplementary material, which is available to authorized users.

Mitochondrial quality control as a key determinant of cell survival

Mitochondria are the energy producing dynamic double-membraned organelles essential for cellular and organismal survival. A multitude of intra- and extra-cellular signals involved in the regulation of energy metabolism and cell fate determination converge on mitochondria to promote or prevent cell survival by modulating mitochondrial function and structure. Mitochondrial fitness is maintained by mitophagy, a pathway of selective degradation of dysfunctional organelles. Mitophagy impairment and altered clearance results in increased levels of dysfunctional and structurally aberrant mitochondria, changes in energy production, loss of responsiveness to intra- and extra-cellular signals and ultimately cell death. The decline of mitochondrial function and homeostasis with age is reported to be central to age-related pathologies. Here we discuss the molecular mechanisms controlling mitochondrial dynamics, mitophagy and cell death signalling and how their perturbation may contribute to ageing and age-related illness.

Toward stimulating apoptosis in human lung adenocarcinoma cells by novel nano-carmofur compound treatment

Lung cancer is one of the common and most fatal diseases worldwide. It has a high incidence in both men and women, in Turkey. Current antineoplastic drugs are reported to have limitations such as narrow therapeutic index and selectivity, toxicity, and antiproliferative effects on cancer cells. Thus, this study was aimed to investigate the potential cytotoxic, antiproliferative and apoptosis-triggering effects of a newly developed SLN-Carmofur compound on human lung adenocarcinoma A549 cells. The results of this study have shown that SLN-Carmofur significantly decreased the viability of A549 cells in a dose-dependent manner by short-time application. The IC50 value of the agent caused chromatin condensation, fragmentation of the nuclei, and holes on cytoskeleton; moreover, it altered the ultrastructure of the exposed cells with clear signs of apoptosis. Taken all our results together, it is indicated that SLN-Carmofur may be proposed for further research for drug development for cancer therapy, depending on the valuable potential in stimulating apoptosis in cancer cells.

Novel glucosylceramide synthase inhibitor based prodrug copolymer micelles for delivery of anticancer agents

In order to improve the efficacy of chemotherapy for cancers, we have developed a novel prodrug micellar formulation to co-deliver ceramide-generating anticancer agents and ceramide degradation inhibitor (PPMP). The prodrug nanocarrier is based on a well-defined POEG-b-PPPMP diblock copolymer. The hydrophilic block of POEG-b-PPPMP is POEG, and the hydrophobic block is composed of a number of PPMP units, which could work synergistically with loaded anticancer drugs. POEG-b-PPPMP was readily synthesized via a one-step reversible addition-fragment transfer (RAFT) polymerization from a PPMP monomer. The newly synthesized polymers were self-assembled into micelles and served as a carrier for several hydrophobic anticancer drugs including DOX, PTX and C6-ceramide. POEG-b-PPPMP prodrug polymer exhibited intrinsic antitumor activity in vitro and in vivo. In addition, POEG-b-PPPMP prodrug polymer was comparable to free PPMP in selectively enhancing the production of pro-apoptotic ceramide species as well as down-regulating the mRNA expression of GCS. DOX-loaded POEG-b-PPPMP micelles exhibited an excellent stability of 42 days at 4 °C. Moreover, DOX loaded in POEG-b-PPPMP micelles showed higher levels of cytotoxicity than DOX loaded in a pharmacologically inert polymer (POEG-b-POM) and Doxil formulation in several tumor cell lines. Consistently, in a 4T1.2 murine breast cancer model, the tumor inhibition followed the order of DOX/POEG-b-PPPMP > DOX/POEG-b-POM ≥ Doxil > POEG-b-PPPMP > POEG-b-POM. Our data suggest that POEG-b-PPPMP micelles are a promising dual-functional carrier that warrants more studies in the future.

Fludarabine-resistance associates with ceramide metabolism and leukemia stem cell development in chronic lymphocytic leukemia

Fludarabine (flu) -containing regimens such as flu, cyclophosphamide and rituximab have been established as one of the standard first line therapy in medically-fit chronic lymphocytic leukemia (CLL) patients. Therefore, flu-refractory (primary flu-insensitivity or flu-caused relapse) remains a major problem causing treatment failure for CLL patients. We isolated the peripheral blood mononuclear cells (PBMCs) from CLL patients and treated with flu to find flu-refractory cases, and established flu-resistant clonal cells to study molecular mechanism of flu-resistance. By comparing parental MEC-2 cells, a human CLL cell line, we found that flu-resistant clonal cells were significantly increased lethal dose 50 of flu concentration, and up-regulated expression of P-glycoprotein, a drug-resistant marker, glucosylceramide synthase (GCS), an enzyme that can convert ceramide to glucosylceramide, and CD34, a leukemia stem cell marker. Overexpression of GCS leads to promptly elimination of cellular ceramide levels and accumulation of glucosylceramide, which reduces apoptosis and promotes survival and proliferation of flu-resistant clonal cells. Furthermore, we demonstrated that the accumulation of glucosylceramide can be blocked by PDMP to restore flu-sensitivity in flu-resistant clonal cells. We also found that elevating glucosylceramide levels in flu-resistant clonal cells was associated with up-regulation of GCS and CD34 expression. Importantly, overexpression of GCS or CD34 was also determined in flu-refractory PBMCs. Our results show that flu-resistance is associated with the alteration of ceramide metabolism and the development of leukemia stem cell-like cells. The flu-resistance can be reversed by GCS inhibition as a novel strategy for overcoming drug resistance.

Ceramide Metabolism Balance, a Multifaceted Factor in Critical Steps of Breast Cancer Development

Ceramides are key lipids in energetic-metabolic pathways and signaling cascades, modulating critical physiological functions in cells. While synthesis of ceramides is performed in endoplasmic reticulum (ER), which is altered under overnutrition conditions, proteins associated with ceramide metabolism are located on membrane arrangement of mitochondria and ER (MAMs). However, ceramide accumulation in meta-inflammation, condition that associates obesity with a chronic low-grade inflammatory state, favors the deregulation of pathways such as insulin signaling, and induces structural rearrangements on mitochondrial membrane, modifying its permeability and altering the flux of ions and other molecules. Considering the wide biological processes in which sphingolipids are implicated, they have been associated with diseases that present abnormalities in their energetic metabolism, such as breast cancer. In this sense, sphingolipids could modulate various cell features, such as growth, proliferation, survival, senescence, and apoptosis in cancer progression; moreover, ceramide metabolism is associated to chemotherapy resistance, and regulation of metastasis. Cell–cell communication mediated by exosomes and lipoproteins has become relevant in the transport of several sphingolipids. Therefore, in this work we performed a comprehensive analysis of the state of the art about the multifaceted roles of ceramides, specifically the deregulation of ceramide metabolism pathways, being a key factor that could modulate neoplastic processes development. Under specific conditions, sphingolipids perform important functions in several cellular processes, and depending on the preponderant species and cellular and/or tissue status can inhibit or promote the development of metabolic and potentially breast cancer disease.

Consequences of blunting the mevalonate pathway in cancer identified by a pluri-omics approach

We have previously shown that the combination of statins and taxanes was a powerful trigger of HGT-1 human gastric cancer cells’ apoptosis¹. Importantly, several genes involved in the “Central carbon metabolism pathway in cancer”, as reported in the Kyoto Encyclopedia of Genes and Genomes, were either up- (ACLY, ERBB2, GCK, MYC, PGM, PKFB2, SLC1A5, SLC7A5, SLC16A3,) or down- (IDH, MDH1, OGDH, P53, PDK) regulated in response to the drug association. In the present study, we conducted non-targeted metabolomics and lipidomics analyses by complementary methods and cross-platform initiatives, namely mass spectrometry (GC-MS, LC-MS) and nuclear magnetic resonance (NMR), to analyze the changes resulting from these treatments. We identified several altered biochemical pathways involved in the anabolism and disposition of amino acids, sugars, and lipids. Using the Cytoscape environment with, as an input, the identified biochemical marker changes, we distinguished the functional links between pathways. Finally, looking at the overlap between metabolomics/lipidomics and transcriptome changes, we identified correlations between gene expression modifications and changes in metabolites/lipids. Among the metabolites commonly detected by all types of platforms, glutamine was the most induced (6–7-fold), pointing to an important metabolic adaptation of cancer cells. Taken together, our results demonstrated that combining robust biochemical and molecular approaches was efficient to identify both altered metabolic pathways and overlapping gene expression alterations in human gastric cancer cells engaging into apoptosis following blunting the cholesterol synthesis pathway.

In Vitro Liquid Extraction Surface Analysis Mass Spectrometry (ivLESA-MS) for Direct Metabolic Analysis of Adherent Cells in Culture

Conventional metabolomic methods include extensive sample preparation steps and long analytical run times, increasing the likelihood of processing artifacts and limiting high throughput applications. We present here in vitro liquid extraction surface analysis mass spectrometry (ivLESA-MS), a variation on LESA-MS, performed directly on adherent cells grown in 96-well cell culture plates. To accomplish this, culture medium was aspirated immediately prior to analysis, and metabolites were extracted using LESA from the cell monolayer surface, followed by nano-electrospray ionization and MS analysis in negative ion mode. We applied this platform to characterize and compare lipidomic profiles of multiple breast cancer cell lines growing in culture (MCF-7, ZR-75-1, MDA-MB-453, and MDA-MB-231) and revealed distinct and reproducible lipidomic signatures between the cell lines. Additionally, we demonstrated time-dependent processing artifacts, underscoring the importance of immediate analysis. ivLESA-MS represents a rapid in vitro metabolomic method, which precludes the need for quenching, cell harvesting, sample preparation, and chromatography, significantly shortening preparation and analysis time while minimizing processing artifacts. This method could be further adapted to test drugs in vitro in a high throughput manner.

Serum sphingolipidomic analyses reveal an upregulation of C16-ceramide and sphingosine-1-phosphate in hepatocellular carcinoma

We have recently shown that major alterations of serum sphingolipid metabolites in chronic liver disease associate significantly with the stage of liver fibrosis in corresponding patients. In the current study we assessed via mass spectrometry serum concentrations of sphingolipid metabolites in a series of 122 patients with hepatocellular carcinoma (HCC) compared to an age- and sex-matched series of 127 patients with cirrhosis. We observed a highly significant upregulation of long and very long chain ceramides (C16-C24) in the serum of patients with HCC as compared to patients with cirrhosis (P < 0.001). Accordingly, dihydro-ceramides, synthetic precursors of ceramides and notably sphingosine, sphingosine-1-phosphate (S1P) and sphinganine-1-phosphate (SA1P) were upregulated in patients with HCC (P < 0.001). Especially the diagnostic accuracy of C16-ceramide and S1P, assessed by receiver operating curve (ROC) analysis, showed a higher area under the curve (AUC) value as compared to alpha fetoprotein (AFP) (0.999 and 0.985 versus 0.823, P < 0.001 respectively). In conclusion, serum levels of sphingolipid metabolites show a significant upregulation in patients with HCC as compared to patients with cirrhosis. Particularly C16-ceramide and S1P may serve as novel diagnostic markers for the identification of HCC in patients with liver diseases. Our data justify further investigations on the role of sphingolipids in HCC.

Targeting Phospholipid Metabolism in Cancer

All cancers tested so far display abnormal choline and ethanolamine phospholipid metabolism, which has been detected with numerous magnetic resonance spectroscopy (MRS) approaches in cells, animal models of cancer, as well as the tumors of cancer patients. Since the discovery of this metabolic hallmark of cancer, many studies have been performed to elucidate the molecular origins of deregulated choline metabolism, to identify targets for cancer treatment, and to develop MRS approaches that detect choline and ethanolamine compounds for clinical use in diagnosis and treatment monitoring. Several enzymes in choline, and recently also ethanolamine, phospholipid metabolism have been identified, and their evaluation has shown that they are involved in carcinogenesis and tumor progression. Several already established enzymes as well as a number of emerging enzymes in phospholipid metabolism can be used as treatment targets for anticancer therapy, either alone or in combination with other chemotherapeutic approaches. This review summarizes the current knowledge of established and relatively novel targets in phospholipid metabolism of cancer, covering choline kinase α, phosphatidylcholine-specific phospholipase D1, phosphatidylcholine-specific phospholipase C, sphingomyelinases, choline transporters, glycerophosphodiesterases, phosphatidylethanolamine N-methyltransferase, and ethanolamine kinase. These enzymes are discussed in terms of their roles in oncogenic transformation, tumor progression, and crucial cancer cell properties such as fast proliferation, migration, and invasion. Their potential as treatment targets are evaluated based on the current literature.

Liposomal C6 Ceramide Activates Protein Phosphatase 1 to Inhibit Melanoma Cells

Melanoma is one common skin cancer. In the present study, the potential anti-melanoma activity by a liposomal C6 ceramide was tested in vitro. We showed that the liposomal C6 (ceramide) was cytotoxic and anti-proliferative against a panel of human melanoma cell lines (SK-Mel2, WM-266.4 and A-375 and WM-115). In addition, liposomal C6 induced caspase-dependent apoptotic death in the melanoma cells. Reversely, its cytotoxicity was attenuated by several caspase inhibitors. Intriguingly, liposomal C6 was non-cytotoxic to B10BR mouse melanocytes and primary human melanocytes. Molecularly, liposomal C6 activated protein phosphatase 1 (PP1) to inactivate Akt-mammalian target of rapamycin (mTOR) signaling in melanoma cells. On the other hand, PP1 shRNA knockdown or exogenous expression of constitutively activate Akt1 (CA-Akt1) restored Akt-mTOR activation and significantly attenuated liposomal C6-mediated cytotoxicity and apoptosis in melanoma cells. Our results suggest that liposomal C6 activates PP1 to inhibit melanoma cells.

Short-chain C6 ceramide sensitizes AT406-induced anti-pancreatic cancer cell activity

Our previous study has shown that AT406, a first-in-class small molecular antagonist of IAPs (inhibitor of apoptosis proteins), inhibits pancreatic cancer cell proliferation in vitro and in vivo. The aim of this research is to increase AT406's sensitivity by adding short-chain C6 ceramide. We show that co-treatment of C6 ceramide dramatically potentiated AT406-induced caspase/apoptosis activation and cytotoxicity in established (Panc-1 and Mia-PaCa-2 lines) and primary human pancreatic cancer cells. Reversely, caspase inhibitors largely attenuated C6 ceramide plus AT406-induced above cancer cell death. Molecularly, C6 ceramide downregulated Bcl-2 to increase AT406's sensitivity in pancreatic cancer cells. Intriguingly, C6 ceramide-mediated AT406 sensitization was nullified with Bcl-2 shRNA knockdown or pretreatment of the Bcl-2 inhibitor ABT-737. In vivo, liposomal C6 ceramide plus AT406 co-administration dramatically inhibited Panc-1 xenograft tumor growth in severe combined immunodeficient (SCID) mice. The combined anti-tumor activity was significantly more potent than either single treatment. Expressions of IAPs (cIAP1/XIAP) and Bcl-2 were downregulated in Panc-1 xenografts with the co-administration. Together, we demonstrate that C6 ceramide sensitizes AT406-mediated anti-pancreatic cancer cell activity possibly via downregulating Bcl-2.

Ceranib-2-induced suicidal erythrocyte death

Ceramide is known to trigger apoptosis of nucleated cells and eryptosis of erythrocytes. Eryptosis is characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Besides ceramide, stimulators of eryptosis include increase of cytosolic Ca(2+) -activity ([Ca(2+) ]i ) and oxidative stress. Ceramide is degraded by acid ceramidase and inhibition of the enzyme similarly triggers apoptosis. The present study explored, whether ceramidase inhibitor Ceranib-2 induces eryptosis. Flow cytometry was employed to quantify phosphatidylserine-exposure at the cell surface from annexin-V-binding, cell volume from forward scatter, [Ca(2+) ]i from Fluo3-fluorescence, reactive oxygen species (ROS) from DCF dependent fluorescence, and ceramide abundance utilizing specific antibodies. Hemolysis was estimated from hemoglobin concentration in the supernatant. A 48 h exposure of human erythrocytes to Ceranib-2 significantly increased the percentage of annexin-V-binding cells (≥50 μM) and the percentage of hemolytic cells (≥10 μM) without significantly modifying forward scatter. Ceranib-2 significantly increased Fluo3-fluorescence, DCF fluorescence and ceramide abundance. The effect of Ceranib-2 on annexin-V-binding was not significantly blunted by removal of extracellular Ca(2+) . Ceranib-2 triggers phospholipid scrambling of the erythrocyte cell membrane, an effect at least in part due to increase of ceramide abundance and induction of oxidative stress, but not dependent on Ca(2+) entry. Copyright © 2016 John Wiley & Sons, Ltd.

Inhibition of ceramide glucosylation sensitizes lung cancer cells to ABC294640, a first-in-class small molecule SphK2 inhibitor

Sphingosine kinase 2 (SphK2) is proposed as a novel oncotarget for lung cancer. Here, we studied the anti-lung cancer cell activity by ABC294640, a first-in-class SphK2 inhibitor. We showed that ABC294640 suppressed growth of primary and A549 human lung cancer cells, but sparing SphK2-low lung epithelial cells. Inhibition of SphK2 by ABC294640 increased ceramide accumulation, but decreased pro-survival sphingosine-1-phosphate (S1P) content, leading to lung cancer cell apoptosis activation. Significantly, we show that glucosylceramide synthase (GCS) might be a major resistance factor of ABC294640. The GCS inhibitor 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) or GCS shRNA/siRNA knockdown facilitated ABC294640-induced ceramide production and lung cancer cell apoptosis. Reversely, forced overexpression of GCS reduced ABC294640's sensitivity, resulting in decreased ceramide accumulation and apoptosis induction in A549 cells. These findings provide further evidences to support that targeting SphK2 by ABC294640 may be a rational treatment option for lung cancer. Ceramide glucosylation inhibition may further sensitize lung cancer cells to ABC294640.

Glucosylceramide synthase induces multidrug resistance by regulating bcl-2 expression in human colon cancer cells

AIM: To investigate the relationship between glucosylceramide synthase (GCS) and bcl-2 in human colon cell line HCT-8 and multidrug resistant (MDR) cell line HCT-8/VCR, in order to explore their role in multidrug resistance of colon cancer cells.

METHODS: The study contained three groups: normally cultured HCT-8 cells (group A), HCT-8/VCR cells treated with VCR to maintain the drug resistance (group B), and HCT-8/VCR cells treated with VCR and inhibitor of GCS (PPMP) (group C). Expression of GCS, bcl-2, and extracellular regulated protein kinases (ERK) proteins was detected by Western blot. Expression of GCS, bcl-2, and ERK mRNAs was tested by real-time quantitative PCR (qRT-PCR).

RESULTS: Compared with HCT-8 cell line, expression of GCS, ERK and bcl-2 proteins and mRNAs was higher in MDR cell line. After treatment with PPMP, expression of those proteins and mRNAs were obviously restrained in HCT-8/VCR cell line.

CONCLUSION: GCS induces multidrug resistance by regulating the expression of bcl-2, and this process may involve ERK signaling pathway. The inhibitor of GCS (PPMP) can inhibit the expression of bcl-2 and reverse multidrug resistance in human colon cancer cell line.

C6 ceramide sensitizes the anti-hepatocellular carcinoma (HCC) activity by AZD-8055, a novel mTORC1/2 dual inhibitor

Aberrant activation of mammalian target of rapamycin (mTOR) plays pivotal roles in promoting hepatocellular carcinoma (HCC) tumorigenesis and chemoresistance. Here, we tested the potential anti-HCC activity by a novel mTOR complex 1/2 (mTORC1/2) dual inhibitor AZD-8055 and, more importantly, the potential AZD-8055 sensitization effect by a cell-permeable short-chain ceramide (C6). We showed that AZD-8055 mainly exerted moderate cytotoxic effect against a panel of HCC cell lines (HepG2, Hep3B, and SMMC-7721). Co-treatment of C6 ceramide remarkably augmented AZD-8055-induced HCC cytotoxicity. Meanwhile, C6 ceramide dramatically potentiated AZD-8055-induced HCC cell apoptotic death. Further studies demonstrated that AZD-8055 and C6 ceramide synergistically induced anti-survival and pro-apoptotic activity in primary cultured human HCC cells, but not in the non-cancerous human hepatocytes. Signaling studies showed that AZD-8055 and C6 ceramide synergistically suppressed Akt-mTOR complex 1/2 cascade activation. In vivo, AZD-8055 oral administration suppressed HepG2 hepatoma xenograft growth in nude mice, while moderately improving mice survival. Its anti-tumor activity was dramatically potentiated with co-administration of a liposome-packed C6 ceramide. Together, these results demonstrate that concurrent targeting mTORC1/2 by AZD-8055 exerts anti-tumor ability in preclinical HCC models, and its activity is further sensitized with co-administration of C6 ceramide.

Lipid metabolic reprogramming in cancer cells

Many human diseases, including metabolic, immune and central nervous system disorders, as well as cancer, are the consequence of an alteration in lipid metabolic enzymes and their pathways. This illustrates the fundamental role played by lipids in maintaining membrane homeostasis and normal function in healthy cells. We reviewed the major lipid dysfunctions occurring during tumor development, as determined using systems biology approaches. In it, we provide detailed insight into the essential roles exerted by specific lipids in mediating intracellular oncogenic signaling, endoplasmic reticulum stress and bidirectional crosstalk between cells of the tumor microenvironment and cancer cells. Finally, we summarize the advances in ongoing research aimed at exploiting the dependency of cancer cells on lipids to abolish tumor progression.

Preclinical Evaluation of Liposomal C8 Ceramide as a Potent anti-Hepatocellular Carcinoma Agent

Hepatocellular carcinoma (HCC) remains a global health threat. The search for novel anti-HCC agents is urgent. In the current study, we synthesized a liposomal C8 ceramide, and analyzed its anti-tumor activity in pre-clinical HCC models. The liposomal C8 (ceramide) potently inhibited HCC cell (HepG2, SMMC-7721 and Huh-7 lines) survival and proliferation, more efficiently than free C8 ceramide. Yet, non-cancerous HL7702 human hepatocytes were resistant to the liposomal C8 treatment. Liposomal C8 activated caspase-dependent apoptosis in HCC cells, and HCC cytotoxicity by liposomal C8 was significantly attenuated with co-treatment of caspase inhibitors. At the molecular level, we showed that liposomal C8 activated ASK1 (apoptosis signal-regulating kinase 1)-JNK (Jun N-terminal protein kinase) signaling in HCC cells. On the other hand, JNK pharmacological inhibition or dominant negative mutation, as well as ASK1 shRNA-knockdown remarkably inhibited liposomal C8-induced apoptosis in HCC cells. Further studies showed that liposomal C8 inhibited AKT-mTOR (mammalian target of rapamycin) activation in HCC cells. Restoring AKT-mTOR activation by introducing a constitutively-active AKT alleviated HepG2 cytotoxicity by liposomal C8. In vivo, intravenous (i.v.) injection of liposomal C8 significantly inhibited HepG2 xenograft growth in severe combined immuno-deficient (SCID) mice, and mice survival was significantly improved. These preclinical results suggest that liposomal C8 could be further studied as a valuable anti-HCC agent.

Ultrasound-stimulated microbubble enhancement of radiation treatments: endothelial cell function and mechanism

Endothelial cell death caused by novel microbubble-enhanced ultrasound cancer therapy leads to secondary tumour cell death. In order to characterize and optimize these treatments, the molecular mechanisms resulting from the interaction with endothelial cells were investigated here.

Endothelial cells (HUVEC) were treated with ultrasound-stimulated microbubbles (US/MB), radiation (XRT), or a combination of US/MB+XRT. Effects on cells were evaluated at 0, 3, 6, and 24 hours after treatment. Experiments took place in the presence of modulators of sphingolipid-based signalling including ceramide, fumonisin B1, monensin, and sphingosine-1-phosphate. Experimental outcomes were evaluated using histology, TUNEL, clonogenic survival methods, immuno-fluorescence, electron microscopy, and endothelial cell blood-vessel-like tube forming assays.

Fewer cells survived after treatment using US/MB+XRT compared to either the control or XRT. The functional ability to form tubes was only reduced in the US/ MB+XRT condition in the control, the ceramide, and the sphingosine-1-phosphate treated groups. The combined treatment had no effect on tube forming ability in either the fumonisin B1 or in the monensin exposed groups, since both interfere with ceramide production at different cellular sites.

In summary, experimental results supported the role of ceramide signalling as a key element in cell death initiation with treatments using US/MB+XRT to target endothelial cells.

SapC-DOPS nanovesicles as targeted therapy for lung cancer

Lung cancer is the deadliest type of cancer for both men and women. In this study, we evaluate the in vitro and in vivo efficacy of a biotherapeutic agent composed of a lysosomal protein (Saposin C, SapC) and a phospholipid (dioleoylphosphatidylserine, DOPS), which can be assembled into nanovesicles (SapC-DOPS) with selective antitumor activity. SapC-DOPS targets phosphatidylserine, an anionic phospholipid preferentially exposed in the surface of cancer cells and tumor-associated vasculature. Because binding of SapC to phosphatidylserine is favored at acidic pHs, and the latter characterizes the milieu of many solid tumors, we tested the effect of pH on the binding capacity of SapC-DOPS to lung tumor cells. Results showed that SapC-DOPS binding to cancer cells was more pronounced at low pH. Viability assays on a panel of human lung tumor cells showed that SapC-DOPS cytotoxicity was positively correlated with cell surface phosphatidylserine levels, whereas mitochondrial membrane potential measurements were consistent with apoptosis-related cell death. Using a fluorescence tracking method in live mice, we show that SapC-DOPS specifically targets human lung cancer xenografts, and that systemic therapy with SapC-DOPS induces tumor apoptosis and significantly inhibits tumor growth. These results suggest that SapC-DOPS nanovesicles are a promising treatment option for lung cancer.

Analytical methods in sphingolipidomics: Quantitative and profiling approaches in food analysis

In recent years, sphingolipidomics has emerged as an interesting omic science that encompasses the study of the full sphingolipidome characterization, content, structure and activity in cells, tissues or organisms. Like other omics, it has the potential to impact biomarker discovery, drug development and systems biology knowledge. Concretely, dietary food sphingolipids have gained considerable importance due to their extensively reported bioactivity. Because of the complexity of this lipid family and their diversity among foods, powerful analytical methodologies are needed for their study. The analytical tools developed in the past have been improved with the enormous advances made in recent years in mass spectrometry (MS) and chromatography, which allow the convenient and sensitive identification and quantitation of sphingolipid classes and form the basis of current sphingolipidomics methodologies. In addition, novel hyphenated nuclear magnetic resonance (NMR) strategies, new ionization strategies, and MS imaging are outlined as promising technologies to shape the future of sphingolipid analyses. This review traces the analytical methods of sphingolipidomics in food analysis concerning sample extraction, chromatographic separation, the identification and quantification of sphingolipids by MS and their structural elucidation by NMR.

Identification of genes involved in breast cancer and breast cancer stem cells

Breast cancer is the most frequent type of cancer in women. Great progress has been made in its treatment but relapse is common. One hypothesis to account for the high recurrence rates is the presence of cancer stem cells (CSCs), which have the ability to self-renew and differentiate into multiple malignant cell types. This study aimed to determine genes that are expressed in breast cancer and breast CSCs and to investigate their correlation with stemness. RNA was extracted from established breast cancer cell lines and from CSCs derived from five different breast cancer patients. DNA microarray analysis was performed and any upregulated genes were also studied in other cancer types, including colorectal and lung cancer. For genes that were expressed only in breast cancer, knockdown-based experiments were performed. Finally, the gene expression levels of stemness transcription factors were measured. The outcome of the analysis indicated a group of genes that were aberrantly expressed mainly in breast cancer cells with stemness properties. Knockdown experiments confirmed the impact of several of these on NANOG, OCT3/4, and SOX2 transcription factors. It seems that several genes that are not directly related with hormone metabolism and basic signal transduction pathways might have an important role in relapse and disease progression and, thus, can be targeted for new treatment approaches for breast cancer.

WITHDRAWN: Investigating the link of ceramide synthases (CerSes) 4 and 5 in endometrial and colon cancers

The Publisher regrets that this article is an accidental duplication of an article that has already been published, http://dx.doi.org/10.1016/j.yexmp.2015.03.023. The duplicate article has therefore been withdrawn. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

Inhibition of acidic sphingomyelinase reduces established hepatic fibrosis in mice

AIM

Liver fibrosis occurs as a result of several chronic liver diseases and leads to portal hypertension, cirrhosis and liver failure, often requiring liver transplantation. Activated hepatic stellate cells (HSC) are known to contribute to liver fibrosis, but currently there are no effective therapies for the treatment of established liver fibrosis. Activation of the acidic sphingomyelinase (ASM) has been shown to be involved in HSC activation. In the present study we investigated whether treatment with the ASM inhibitor, amitriptyline (TCA), could prevent and/or reverse fibrosis induced in mice by carbon tetrachloride (CCl4 ).

METHODS

Mice were treated with CCl4 for 8 weeks to induce fibrosis. Concurrently, mice received drinking water with or without 180 mg/L TCA.

RESULTS

Mice receiving TCA in the water had decreased hepatic collagen deposition and reduced liver mRNA expression of the fibrogenic mediators, transforming growth factor (TGF)-β1, tissue inhibitor of matrix metalloproteinase-1, collagen and tumor necrosis factor-α. TCA treatment also reduced HSC activation determined by α-smooth muscle actin staining. In a separate set of experiments, mice were treated with CCl4 for 5 weeks prior to treatment with TCA, to test whether TCA had any effect on established fibrosis. Remarkably, in mice with established fibrosis, treatment with TCA significantly reduced collagen deposition, HSC activation, and prevented portal hypertension and improved hepatic architecture. Treatment of isolated HSC in vitro with TCA completely inhibited TGF-β1-induced collagen expression and platelet-derived growth factor-β-β-induced proliferation.

CONCLUSION

The data suggest that ASM is a critical signaling component in HSC for the development of liver fibrosis and represents an important therapeutic target.

Roles and regulation of neutral sphingomyelinase-2 in cellular and pathological processes

Our understanding of the functions of ceramide signaling has advanced tremendously over the past decade. In this review, we focus on the roles and regulation of neutral sphingomyelinase 2 (nSMase2), an enzyme that generates the bioactive lipid ceramide through the hydrolysis of the membrane lipid sphingomyelin. A large body of work has now implicated nSMase2 in a diverse set of cellular functions, physiological processes, and disease pathologies. We discuss different aspects of this enzyme's regulation from transcriptional, post-translational, and biochemical. Furthermore, we highlight nSMase2 involvement in cellular processes including inflammatory signaling, exosome generation, cell growth, and apoptosis, which in turn play important roles in pathologies such as cancer metastasis, Alzheimer's disease, and other organ systems disorders. Lastly, we examine avenues where targeted nSMase2-inhibition may be clinically beneficial in disease scenarios.

Interactions of anticancer drugs with biomembranes: what can we learn from model membranes?

The interactions of anticancer drugs with cell membranes are of primary importance for drug transport, accumulation and activity. However, these interactions are very difficult to investigate because of the complexity of biological membranes. Lipid model membranes have therefore been built to gain insight into the collective role of lipids in drug-membrane interactions. Membranes can act as a barrier for drug molecules, sequester them or conversely may allow them to freely diffuse, thereby modulating the accumulation of drugs into cells. Lipid membranes also affect the ability of the efflux pump Pgp to bind and efflux anticancer drugs from cells. On the other hand, anticancer drugs can alter the structure and properties of lipid membranes, which are expected to influence the functioning of embedded proteins. The relevance of lipid model membranes to assess interactions between anticancer drugs and biomembranes is evidenced.