Role of Sphingolipids and Metabolizing Enzymes in Hematological Malignancies

A Novel Family of Lysosomotropic Tetracyclic Compounds for Treating Leukemia

Acute myeloid leukemia (AML) is a heterogeneous hematological cancer characterized by poor prognosis and frequent relapses. Aside from specific mutation-related changes, in AML, the overall function of lysosomes and mitochondria is drastically altered to fulfill the elevated biomass and bioenergetic demands. On the basis of previous results, in silico drug discovery screening was used to identify a new family of lysosome-/mitochondria-targeting compounds. These novel tetracyclic hits, with a cationic amphiphilic structure, specifically eradicate leukemic cells by inducing both mitochondrial damage and apoptosis, and simultaneous lysosomal membrane leakiness. Lysosomal leakiness does not only elicit canonical lysosome-dependent cell death, but also activates the terminal differentiation of AML cells through the Ca²⁺-TFEB-MYC signaling axis. In addition to being an effective monotherapy, its combination with the chemotherapeutic arsenic trioxide (ATO) used in other types of leukemia is highly synergistic in AML cells, widening the therapeutic window of the treatment. Moreover, the compounds are effective in a wide panel of cancer cell lines and possess adequate pharmacological properties rendering them promising drug candidates for the treatment of AML and other neoplasias.

Advancements on the Multifaceted Roles of Sphingolipids in Hematological Malignancies

Dysregulation of sphingolipid metabolism plays a complex role in hematological malignancies, beginning with the first historical link between sphingolipids and apoptosis discovered in HL-60 leukemic cells. Numerous manuscripts have reviewed the field including the early discoveries that jumpstarted the studies. Many studies discussed here support a role for sphingolipids, such as ceramide, in combinatorial therapeutic regimens to enhance anti-leukemic effects and reduce resistance to standard therapies. Additionally, inhibitors of specific nodes of the sphingolipid pathway, such as sphingosine kinase inhibitors, significantly reduce leukemic cell survival in various types of leukemias. Acid ceramidase inhibitors have also shown promising results in acute myeloid leukemia. As the field moves rapidly, here we aim to expand the body of literature discussed in previously published reviews by focusing on advances reported in the latter part of the last decade.

The role of selenoprotein P in the determining the sensitivity of cervical cancer patients to concurrent chemoradiotherapy: A metabonomics-based analysis

BACKGROUND

The effect of selenoprotein P (SELENOP) levels on the sensitivity of cervical cancer patients to concurrent chemoradiotherapy (CCRT) has not been reported. In this study, the effects of the variations in plasma SELENOP levels on the sensitivity of cervical cancer patients to CCRT were investigated using metabonomics.

METHODS

Two patient groups were evaluated, i.e., the case group: 11 patients with intermediate to advanced primary squamous cervical cancer, who developed resistance against CCRT, and the sensitivity group: 11 patients who did not develop resistance were matched in a 1:1 ratio (controls). Blood samples were collected before and after CCRT, and the plasma SELENOP levels were measured by ELISA. The different metabolites present in the plasma were analyzed by UPLC-MS-MS.

RESULTS

SELENOP levels exhibited a significant reduction in both the resistant and sensitive groups after CCRT (F = 50.705, P < 0.001), and interaction effects between sensitivity and pre-and post-treatment on SELENOP levels were observed (F = 7.414, P = 0.013). Further, a more significant reduction in the SELENOP levels was observed in the CCRT-resistant group (mean reduction, 0.028 µg/mL; P < 0.001) than in the sensitive group (mean reduction, 0.013 µg/mL; P = 0.006). Four metabolic biomarkers, i.e., C18, C19, C20 sphingomyelin, and phosphatidylcholine 20:2/22:6, were shown to be differentially expressed between the resistant and sensitive groups pre-and post-treatment. C20 sphingomyelin levels exhibited a significant correlation with SELENOP levels (r = -0.326, P = 0.031).

CONCLUSION

The levels of plasma SELENOP in the CCRT-resistant group decreased significantly, suggesting that SELENOP might affect the sensitivity by modulating lipid synthesis and metabolism.

Effect of a Functional Phospholipid Metabolome-Protein Association Pathway on the Mechanism of COVID-19 Disease Progression

This study aimed to explore the clinical practice of phospholipid metabolic pathways in COVID-19. In this study, 48 COVID-19 patients and 17 healthy controls were included. Patients were divided into mild (n=40) and severe (n=8) according to their severity. Phospholipid metabolites, TCA circulating metabolites, eicosanoid metabolites, and closely associated enzymes and transfer proteins were detected in the plasma of all individuals using metabolomics and proteomics assays, respectively. 30 of the 33 metabolites found differed significantly (P<0.05) between patients and healthy controls (P<0.05), with D-dimmer significantly correlated with all of the lysophospholipid metabolites (LysoPE, LysoPC, LysoPI and LPA). In particular, we found that phosphatidylinositol (PI) and phosphatidylcholine (PC) could identify patients from healthy controls (AUC 0.771 and 0.745, respectively) and that the severity of the patients could be determined (AUC 0.663 and 0.809, respectively). The last measurement before discharge also revealed significant changes in both PI and PC. For the first time, our study explores the significance of the phospholipid metabolic system in COVID-19 patients. Based on molecular pathway mechanisms, three important phospholipid pathways related to Ceramide-Malate acid (Cer-SM), Lysophospholipid (LPs), and membrane function were established. Clinical values discovered included the role of Cer in maintaining the inflammatory internal environment, the modulation of procoagulant LPA by upstream fibrinolytic metabolites, and the role of PI and PC in predicting disease aggravation.

Role of Sphingolipids in Multiple Myeloma Progression, Drug Resistance, and Their Potential as Therapeutic Targets

Multiple myeloma (MM) is an incapacitating hematological malignancy characterized by accumulation of cancerous plasma cells in the bone marrow (BM) and production of an abnormal monoclonal protein (M-protein). The BM microenvironment has a key role in myeloma development by facilitating the growth of the aberrant plasma cells, which eventually interfere with the homeostasis of the bone cells, exacerbating osteolysis and inhibiting osteoblast differentiation. Recent recognition that metabolic reprograming has a major role in tumor growth and adaptation to specific changes in the microenvironmental niche have led to consideration of the role of sphingolipids and the enzymes that control their biosynthesis and degradation as critical mediators of cancer since these bioactive lipids have been directly linked to the control of cell growth, proliferation, and apoptosis, among other cellular functions. In this review, we present the recent progress of the research investigating the biological implications of sphingolipid metabolism alterations in the regulation of myeloma development and its progression from the pre-malignant stage and discuss the roles of sphingolipids in in MM migration and adhesion, survival and proliferation, as well as angiogenesis and invasion. We introduce the current knowledge regarding the role of sphingolipids as mediators of the immune response and drug-resistance in MM and tackle the new developments suggesting the manipulation of the sphingolipid network as a novel therapeutic direction for MM.

Serum Abnormal Metabolites for Evaluating Therapeutic Response and Prognosis of Patients With Multiple Myeloma

Aims

To evaluate abnormal metabolites related to treatment response and prognosis of multiple myeloma (MM) patients through ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS).

Methods

Forty-six symptomatic MM patients were included in this study who had a prior high level of positive monoclonal proteins before receiving targeted therapy with bortezomib-based regimens. UPLC-MS along with traditional immunofixation was performed on MM diagnostic samples and effective serum samples, and UPLC-MS was used to target valuable metabolic markers related to M protein.MM patients were segregated into pre-therapy (pre-T) and post-therapy (post-T) groups according to the response after chemotherapy. A monoclonal protein could be detected at baseline in 33 newly diagnosed MM (NDMM), 13 refractory and relapsed MM (RRMM) patients and 20 healthy controls (HC) by immunofixation.

Results

Between pre-T and post-T patients, the data showed that 32, 28 and 3 different metabolites were significantly correlated with M protein in IgG, IgA and light chain-type MM, respectively. These identified metabolites were significantly enriched in arginine and proline metabolism as well as glycerophospholipid metabolism pathways. Among them, PC (19:0/22:2) was displayed to increase significantly and consistently with M protein in each subtype of MM after treatment, which obviously indicated that it was related to the treatment response of MM. Further survival analysis of metabolic markers found that aspartic acid, LysoPE (16:0), SM (d18:1/17:0), PC (18:0/24:1), PC (16:0/16:0), TG (18:1/18:1/22:5) and LysoPE (18:2) reaching a certain cutoff value may be associated with shorter progression free survival (PFS). Finally, Cox multivariate regression analysis identified three factors were independent prognostic factors of MM. Moreover, there were significantly different in PC (19:0/22:2) and in aspartic acid between MM patients and healthy people.

Conclusion

This work identified significant metabolic disorders in 46 pairs off pre- and post-therapy MM patients, specifically in arginine, proline and glycerophospholipid pathways. The abnormal metabolites have the potential to serve as new biomarkers for evaluating treatment response and prognosis, as well as early monitoring of disease activity. Therefore, these systematic studies on abnormal metabolites as biomarkers for diagnosis and treatment will provide the evidence for future precise treatment of MM.

Nuclear Ceramide Is Associated with Ataxia Telangiectasia Mutated Activation in the Neocarzinostatin-Induced Apoptosis of Lymphoblastoid Cells

Ceramide is a bioactive sphingolipid that mediates ionizing radiation- and chemotherapy-induced apoptosis. Neocarzinostatin (NCS) is a genotoxic anti-cancer drug that induces apoptosis in response to DNA double-strand breaks (DSBs) through ataxia telangiectasia mutated (ATM) activation. However, the involvement of ceramide in NCS-evoked nuclear events such as DSB-activated ATM has not been clarified. Here, we found that nuclear ceramide increased by NCS-mediated apoptosis through the enhanced assembly of ATM and the meiotic recombination 11/double-strand break repair/Nijmengen breakage syndrome 1 (MRN) complex proteins in human lymphoblastoid L-39 cells. NCS induced an increase of ceramide production through activation of neutral sphingomyelinase (nSMase) and suppression of sphingomyelin synthase (SMS) upstream of DSB-mediated ATM activation. In ATM-deficient lymphoblastoid AT-59 cells compared with L-39 cells, NCS treatment showed a decrease of apoptosis even though ceramide increase and DSBs were observed. Expression of wild-type ATM, but not the kinase-dead mutant ATM, in AT-59 cells increased NCS-induced apoptosis despite similar ceramide accumulation. Interestingly, NCS increased ceramide content in the nucleus through nSMase activation and SMS suppression and promoted colocalization of ceramide with phosphorylated ATM and foci of MRN complex. Inhibition of ceramide generation by the overexpression of SMS suppressed NCS-induced apoptosis through the inhibition of ATM activation and assembly of the MRN complex. In addition, inhibition of ceramide increased by the nSMase inhibitor GW4869 prevented NCS-mediated activation of the ATM. Therefore, our findings suggest the involvement of the nuclear ceramide with ATM activation in NCS-mediated apoptosis. SIGNIFICANCE STATEMENT: This study demonstrates that regulation of ceramide with neutral sphingomyelinase and sphingomyelin synthase in the nucleus in double-strand break-mimetic agent neocarzinostatin (NCS)-induced apoptosis. This study also showed that ceramide increase in the nucleus plays a role in NCS-induced apoptosis through activation of the ataxia telangiectasia mutated/meiotic recombination 11/double-strand break repair/Nijmengen breakage syndrome 1 complex in human lymphoblastoid cells.

Sphingolipids in Hematopoiesis: Exploring Their Role in Lineage Commitment

Sphingolipids, associated enzymes, and the sphingolipid pathway are implicated in complex, multifaceted roles impacting several cell functions, such as cellular homeostasis, apoptosis, cell differentiation, and more through intrinsic and autocrine/paracrine mechanisms. Given this broad range of functions, it comes as no surprise that a large body of evidence points to important functions of sphingolipids in hematopoiesis. As the understanding of the processes that regulate hematopoiesis and of the specific characteristics that define each type of hematopoietic cells is being continuously refined, the understanding of the roles of sphingolipid metabolism in hematopoietic lineage commitment is also evolving. Recent findings indicate that sphingolipid alterations can modulate lineage commitment from stem cells all the way to megakaryocytic, erythroid, myeloid, and lymphoid cells. For instance, recent evidence points to the ability of de novo sphingolipids to regulate the stemness of hematopoietic stem cells while a substantial body of literature implicates various sphingolipids in specialized terminal differentiation, such as thrombopoiesis. This review provides a comprehensive discussion focused on the mechanisms that link sphingolipids to the commitment of hematopoietic cells to the different lineages, also highlighting yet to be resolved questions.

New Therapeutic Approaches for Acute Myeloid Leukaemia

Acute myeloid leukaemia (AML) is a genetically heterogeneous haematopoietic neoplasm characterised by the accumulation of transformed immature blood progenitors in bone marrow. Since 1973, the backbone treatment has relied on the combination of cytarabine and an anthracycline, followed by allogeneic haematopoietic transplant if eligible. Therefore, the treatment decisions have largely revolved around chemotherapy drug intensity. Despite advances in our understanding of the underlying biology over the past decades, AML remains a therapeutic challenge as the overall survival is poor and treatment options are limited for relapsed/refractory AML or for unfit patients. After four decades without substantial changes, eight new noncytostatic drugs have been granted approval: vyxeos, enasidenib, gilteritinib, glasdegib, gemtuzumab ozogamicin, ivosidenib, midostaurin, and venetoclax. Despite promising preliminary results, some indications are based on early efficacy data, obtained in single-arm nonrandomised trials, highlighting the necessity for further validation in extended clinical trials. Interestingly, several druggable targets have been identified recently, associated with specific target-directed drugs. Based on the preclinical data available, great impact on clinical outcomes for patients with AML is expected, potentially increasing the therapeutic landscape for this disease.

Cytokine Levels at Birth in Children Who Developed Acute Lymphoblastic Leukemia

BACKGROUND

Prenatal immune development may play an important role in the etiology of childhood acute lymphoblastic leukemia (ALL).

METHODS

Seven cytokines, IL1β, IL4, IL6, IL8, GM-CSF, TNFα, and VEGF, were analyzed in blood spots collected at birth from 1,020 ALL cases and 1,003 controls participating in the California Childhood Leukemia Study. ORs and 95% confidence intervals (95% CI) associated with an interquartile range increment in cytokine levels were calculated using logistic regression, adjusting for sociodemographic and birth characteristics.

RESULTS

We found that patients with ALL were born with higher levels of a group of correlated cytokines than controls [IL1β: OR of 1.18 (95% confidence interval [CI], 1.03-1.35); IL8: 1.19 (1.03-1.38); TNFα: 1.15 (1.01-1.30); VEGF: 1.16 (1.01-1.33)], especially among children of Latina mothers (ORs from 1.31 to 1.40) and for ALL with high hyperdiploidy (ORs as high as 1.27). We found that neonatal cytokine levels were correlated with neonatal levels of endogenous metabolites which had been previously associated with ALL risk; however, there was no evidence that the cytokines were mediating the relationship between these metabolites and ALL risk.

CONCLUSIONS

We posit that children born with altered cytokine levels are set on a trajectory towards an increased risk for subsequent aberrant immune reactions that can initiate ALL.

IMPACT

This is the first study to evaluate the interplay between levels of immunomodulatory cytokines at birth, prenatal exposures, and the risk of childhood ALL.

Serum sphingomyelin species profile is altered in hematologic malignancies

Sphingomyelin (SM) plays key roles in regulating cell membrane fluidity and in intracellular signal transduction. However, little is known as to whether alterations in SM concentration or SM species distribution are linked pathological conditions. The present study examined SM concentrations and species profiles in serum taken from patients with hematologic malignancies. Serum was collected from normal subjects and from patients with B-cell lymphoma, myelodysplastic syndrome (MDS), acute myeloid leukemia (AML) and acute lymphatic leukemia/ lymphoblastic lymphoma (ALL/LBL). Serum SM species distribution was analyzed using electrospray ionization mass spectrometry/ mass spectrometry (ESI MS/MS). Serum lipids concentration were measured using enzymatic assays. Normal and hematologic malignancy sera were similar in terms of total serum SM and phosphatidylcholine (PC) concentrations and SM/PC ratio. However, all hematologic malignancy sera had lower levels of SM species containing saturated odd chain fatty acids (OCFAs) in the side chain compared to normal serum. In addition, the proportion of SM species with saturated (C20 and C22) and mono unsaturated fatty acids (C18, C20, C22) were lower in MDS patient serum compared to normal serum. The present study revealed that the serum SM species profile in patients with hematologic malignancies differed from that of normal subjects despite total serum SM and PC concentrations and SM/PC ratios being similar between the various cancer groups and the normal group.

8-Hydroxydaidzein, an Isoflavone from Fermented Soybean, Induces Autophagy, Apoptosis, Differentiation, and Degradation of Oncoprotein BCR-ABL in K562 Cells

8-Hydroxydaidzein (8-OHD, 7,8,4'-trihydoxyisoflavone) is a hydroxylated derivative of daidzein isolated from fermented soybean products. The aim of this study is to investigate the anti-proliferative effects and the underlying mechanisms of 8-OHD in K562 human chronic myeloid leukemia (CML) cells. We found that 8-OHD induced reactive oxygen species (ROS) overproduction and cell cycle arrest at the S phase by upregulating p21Cip1 and downregulating cyclin D2 (CCND2) and cyclin-dependent kinase 6 (CDK6) expression. 8-OHD also induced autophagy, caspase-7-dependent apoptosis, and the degradation of BCR-ABL oncoprotein. 8-OHD promoted Early Growth Response 1 (EGR1)-mediated megakaryocytic differentiation as an increased expression of marker genes, CD61 and CD42b, and the formation of multi-lobulated nuclei in enlarged K562 cells. A microarray-based transcriptome analysis revealed a total of 3174 differentially expressed genes (DEGs) after 8-OHD (100 μM) treatment for 48 h. Bioinformatics analysis of DEGs showed that hemopoiesis, cell cycle regulation, nuclear factor-κB (NF-κB), and mitogen-activated protein kinase (MAPK) and Janus kinase/signal transducers and activators of transcription (JAK-STAT)-mediated apoptosis/anti-apoptosis networks were significantly regulated by 8-OHD. Western blot analysis confirmed that 8-OHD significantly induced the activation of MAPK and NF-κB signaling pathways, both of which may be responsible, at least in part, for the stimulation of apoptosis, autophagy, and differentiation in K562 cells. This is the first report on the anti-CML effects of 8-OHD and the combination of experimental and in silico analyses could provide a better understanding for the development of 8-OHD on CML therapy.

Bioactive lipids in inflammatory bowel diseases - From pathophysiological alterations to therapeutic opportunities

Inflammatory bowel diseases (IBDs), such as Crohn's disease and ulcerative colitis, are lifelong diseases that remain challenging to treat. IBDs are characterized by alterations in intestinal barrier function and dysregulation of the innate and adaptive immunity. An increasing number of lipids are found to be important regulators of inflammation and immunity as well as gut physiology. Therefore, the study of lipid mediators in IBDs is expected to improve our understanding of disease pathogenesis and lead to novel therapeutic opportunities. Here, through selected examples - such as fatty acids, specialized proresolving mediators, lysophospholipids, endocannabinoids, and oxysterols - we discuss how lipid signaling is involved in IBD physiopathology and how modulating lipid signaling pathways could affect IBDs.

Sphingolipid metabolism determines the therapeutic efficacy of nanoliposomal ceramide in acute myeloid leukemia

Distinct sphingolipid metabolism of AML with MDS-related changes defines unique sensitivity to nanoliposomal C6-ceramide. Vinblastine alters sphingolipid metabolism to enhance the sensitivity of AML to nanoliposomal C6-ceramide.

Ceramide/Sphingomyelin Rheostat Regulated by Sphingomyelin Synthases and Chronic Diseases in Murine Models

Ceramide and sphingomyelin (SM) are major components of the double membrane-bound sphingolipids. Ceramide is an essential bioactive lipid involved in numerous cell processes including apoptosis, necrosis, and autophagy-dependent cell death. Inversely, SM regulates opposite cellular processes such as proliferation and migration by changing receptor-mediated signal transduction in the lipid microdomain. SM is generated through a transfer of phosphocholine from phosphatidylcholine to ceramide by SM synthases (SMSs). Research during the past several decades has revealed that the ceramide/SM balance in cellular membranes regulated by SMSs is important to decide the cell fate, survival, and proliferation. In addition, recent experimental studies utilizing SMS knockout mice and murine disease models provide evidence that SMS-regulated ceramide/SM balance is involved in human diseases. Here, we review the basic structural and functional characteristics of SMSs and focus on their cellular functions through the regulation of ceramide/SM balance in membrane microdomains. In addition, we present the pathological or physiological implications of SMSs by analyzing their role in SMS-knockout mice and human disease models. This review finally presents evidence indicating that the regulation of ceramide/SM balance through SMS could be a therapeutic target for human disorders.

Ceramide and Sphingosine 1-Phosphate in Liver Diseases

The liver is an important organ in the regulation of glucose and lipid metabolism. It is responsible for systemic energy homeostasis. When energy need exceeds the storage capacity in the liver, fatty acids are shunted into nonoxidative sphingolipid biosynthesis, which increases the level of cellular ceramides. Accumulation of ceramides alters substrate utilization from glucose to lipids, activates triglyceride storage, and results in the development of both insulin resistance and hepatosteatosis, increasing the likelihood of major metabolic diseases. Another sphingolipid metabolite, sphingosine 1-phosphate (S1P) is a bioactive signaling molecule that acts via S1P-specific G protein coupled receptors. It regulates many cellular and physiological events. Since an increase in plasma S1P is associated with obesity, it seems reasonable that recent studies have provided evidence that S1P is linked to lipid pathophysiology, including hepatosteatosis and fibrosis. Herein, we review recent findings on ceramides and S1P in obesity-mediated liver diseases and the therapeutic potential of these sphingolipid metabolites.

Navigating the Role of CD1d/Invariant Natural Killer T-cell/Glycolipid Immune Axis in Multiple Myeloma Evolution: Therapeutic Implications

Multiple myeloma (MM) is an incurable B-cell malignancy. The immunotherapeutic approach for MM therapy is evolving. The Cd1d/invariant natural killer T-cell/glycolipid immune axis belongs to the innate immunity, and we have highlighted role in myeloma pathogenesis in the present study. The recent development of the chimeric antigen receptor (CAR19)-invariant natural killer T-cells resulted in our renewed interest in this immune system and offer new perspectives for future anti-MM immunotherapies.

Deficiency of sphingomyelin synthase 2 prolongs survival by the inhibition of lymphoma infiltration through ICAM-1 reduction

The tumor microenvironment (TME) formation involving host cells and cancer cells through cell adhesion molecules (CAMs) is essential for the multiple steps of cancer metastasis and growth. Sphingomyelin synthase 2 (SMS2) is involved in inflammatory diseases such as obesity and diabetes mellitus by regulation of the SM/ceramide balance. However, the involvement of SMS2 in TME formation and metastasis is largely unknown. Here, we report that SMS2-deficient (SMS2-KO) mice show suppressed the EL4 cell infiltration to liver and prolonged survival time. ICAM-1 was identified as a candidate for the inhibition of TME formation in immortalized mouse embryonic fibroblasts (tMEFs) from mRNA array analysis for CAMs. Reduced SM/ceramide balance in SMS2-KO tMEFs suppressed the attachment of EL4 cells through transcriptional reduction of ICAM-1 by the inhibition of NF-κB activation. TNF-α-induced NF-κB activation and subsequent induction of ICAM-1 were suppressed in SMS2-KO tMEFs but restored by SMS2 re-introduction. In the EL4 cell infiltration mouse model, EL4 injection increased ICAM-1 expression in WT liver but not in SMS2-KO mouse liver. Therefore, inhibition of SMS2 may be a therapeutic target to suppress the infiltration of malignant lymphoma.

Association of serum sphingomyelin profile with clinical outcomes in patients with lower respiratory tract infections: results of an observational, prospective 6-year follow-up study

Background Sphingolipids - the structural cell membrane components - and their metabolites are involved in signal transduction and participate in the regulation of immunity. We investigated the prognostic implications of sphingolipid metabolic profiling on mortality in a large cohort of patients with lower respiratory tract infections (LRTIs). Methods We measured 15 different sphingomyelin (SM) types in patients with LRTIs from a previous Swiss multicenter trial that examined the impact of procalcitonin-guided antibiotic therapy on total antibiotic use and rates and duration of hospitalization. Primary and secondary end points were adverse outcomes - defined as death or intensive care unit admission within 30 days - and 6-year mortality. Results Of 360 patients, 8.9% experienced an adverse outcome within 30 days and 46% died within 6 years. Levels of all SM types were significantly lower in pneumonia patients vs. those with chronic obstructive pulmonary disease (COPD) exacerbation (p<0.0001 for all comparisons). Sphingomyelin subspecies SM (OH) C22:1 and SM (OH) C22:2 were associated with lower risk for short-term adverse outcomes (sex-, gender- and comorbidity-adjusted odds ratios [OR]: 0.036; 95% confidence interval [CI], 0.002-0.600; p=0.021 and 0.037; 95% CI, 0.001-0.848; p=0.039, respectively). We found no significant associations with 6-year mortality for any SM. Conclusions Circulating sphingolipid levels are lower in inflammatory conditions such as pneumonia and correlate with adverse short-term outcomes. Further characterization of the physiological, pathophysiological and metabolic roles of sphingolipids under inflammatory conditions may facilitate understanding of their roles in infectious disease.

Ins and Outs of Interpreting Lipidomic Results

Membrane lipids are essential for life; however, research on how cells regulate cell lipid composition has been falling behind for quite some time. One reason was the difficulty in establishing analytical methods able to cope with the cell lipid repertoire. Development of a diversity of mass spectrometry-based technologies, including imaging mass spectrometry, has helped to demonstrate beyond doubt that the cell lipidome is not only greatly cell type dependent but also highly sensitive to any pathophysiological alteration such as differentiation or tumorigenesis. Interestingly, the current popularization of metabolomic studies among numerous disciplines has led many researchers to rediscover lipids. Hence, it is important to underscore the peculiarities of these metabolites and their metabolism, which are both radically different from protein and nucleic acid metabolism. Once differences in lipid composition have been established, researchers face a rather complex scenario, to investigate the signaling pathways and molecular mechanisms accounting for their results. Thus, a detail often overlooked, but of crucial relevance, is the complex networks of enzymes involved in controlling the level of each one of the lipid species present in the cell. In most cases, these enzymes are redundant and promiscuous, complicating any study on lipid metabolism, since the modification of one particular lipid enzyme impacts simultaneously on many species. Altogether, this review aims to describe the difficulties in delving into the regulatory mechanisms tailoring the lipidome at the activity, genetic, and epigenetic level, while conveying the numerous, stimulating, and sometimes unexpected research opportunities afforded by this type of studies.

Ceramide Suppresses Influenza A Virus Replication In Vitro

Annual influenza outbreaks are associated with significant morbidity and mortality worldwide despite the availability of seasonal vaccines. Influenza pathogenesis depends on the manipulation of host cell signaling to promote virus replication. Ceramide is a sphingosine-derived lipid that regulates diverse cellular processes. Studies highlighted the differential role of ceramide de novo biosynthesis on the propagation of various viruses. Whether ceramide plays, a role in influenza virus replication is not known. In this study, we assessed the potential interplay between the influenza A (IAV) and ceramide biosynthesis pathways. The accumulation of ceramide in human lung epithelial cells infected with influenza A/H1N1 virus strains was evaluated using thin-layer chromatography and/or confocal microscopy. Virus replication was assessed upon the regulation of the de novo ceramide biosynthesis pathway. A significant increase in ceramide accumulation was observed in cells infected with IAV in a dose- and time-dependent manner. Inoculating the cells with UV-inactivated IAV did not result in ceramide accumulation in the cells, suggesting that the induction of ceramide required an active virus replication. Inhibiting de novo ceramide significantly decreased ceramide accumulation and enhanced virus replication. The addition of exogenous C₆-ceramide prior to infection mediated an increase in cellular ceramide levels and significantly attenuated IAV replication and reduced viral titers (≈1 log10 PFU/ml unit). Therefore, our data demonstrate that ceramide accumulation through de novo biosynthesis pathway plays a protective and antiviral role against IAV infection. These findings propose new avenues for development of antiviral molecules and strategies.IMPORTANCE Understanding the effect of sphingolipid metabolism on viral pathogenesis provide important insights into the development of therapeutic strategies against microbial infections. In this study, we demonstrate a critical role of ceramide during influenza A virus infection. We demonstrate that ceramide produced through de novo biosynthesis possess an antiviral role. These observations unlock new opportunities for the development of novel antiviral therapies against influenza.

Sphingosine kinase 1 overexpression contributes to sunitinib resistance in clear cell renal cell carcinoma

Sphingosine kinase 1 (SphK1) is the major source of the bioactive lipid and GPCR agonist sphingosine 1-phosphate (S1P). Although alterations in SphK1 expression and activity have been detected in various human malignancies, its potential molecular mechanisms in the development and sunitinib resistance of clear cell renal cell carcinoma (ccRCC) remain obscure. In this study, we aim to evaluate the clinical significance of SphK1 and to explore the therapeutic implications of combination approach for ccRCC patients. We identify upregulation of SphK1 significantly associated with poor prognosis of large cohort of ccRCC patients, which contributing to cell proliferation, colony formation, migration and survival. Suppression of SphK1 activity either by shRNA or pharmacologic inhibitior FTY720 suppresses cell growth in vitro and in vivo. A comprehensive phosphoprotein antibody array reveals that SphK1 overexpression promoted RCC progression by regulating the Akt/mTOR pathway. Moreover, FTY720 administration enhanced tumor growth inhibition effect of sunitinib treatment on RCC cells in vitro and in vivo. Our results unraveled that increased SphK1 kinase activation defines an important mechanism for sunitinib resistance, therefore contributes to tumour development and represents therapeutic targets for ccRCC.

Ceramide synthase-6 confers resistance to chemotherapy by binding to CD95/Fas in T-cell acute lymphoblastic leukemia

Ceramide synthases (CERS) produce ceramides which are key intermediators in the biosynthesis of complex sphingolipids and play an important role in cell proliferation, differentiation, apoptosis and senescence. CERS6 is an isoform of ceramide synthases known to generate ceramides with C16 acyl chain (C₁₆-Cer). CERS6 and C₁₆-Cer levels were significantly higher in acute lymphoblastic leukemia (ALL) cells in comparison to peripheral blood mononuclear cells and T lymphocytes derived from healthy human volunteers. We investigated the role of CERS6 in chemo-resistance in T-ALL cell lines. Stable knockdown of CERS6 in CCRF-CEM and MOLT-4 cells resulted in increased sensitivity to ABT-737, a pan-BCL-2 inhibitor, while CCRF-CEM cells with exogenous CERS6 expression showed resistance to ABT-737 relative to the vector control. The cytotoxic activity of ABT-737 in CERS6 knockdown cells was significantly reduced by the addition of a caspase-8 inhibitor Z-IETD, suggesting that CERS6 alters the cytotoxicity via extrinsic pathway of apoptosis. By co-immunoprecipitation of CERS6 in CCRF-CEM cells, we identified CD95/Fas, a mediator of extrinsic apoptotic pathway, as a novel CERS6 binding partner. In Fas pull-down samples, FADD (Fas-associated protein with death domain) was detected at higher levels in cells with CERS6 knockdown compared with control cells when treated with ABT-737, and this was reversed by the overexpression of CERS6, demonstrating that CERS6 interferes with Fas–FADD DISC assembly. CERS6 may serve as a biomarker in determining the effectiveness of anticancer agents acting via the extrinsic pathway in T-ALL.

Holotoxin A₁ Induces Apoptosis by Activating Acid Sphingomyelinase and Neutral Sphingomyelinase in K562 and Human Primary Leukemia Cells

Marine triterpene glycosides are attractive candidates for the development of anticancer agents. Holotoxin A₁ is a triterpene glycoside found in the edible sea cucumber, Apostichopus (Stichopus) japonicus. We previously showed that cladoloside C₂, the 25(26)-dihydro derivative of holotoxin A₁, induced apoptosis in human leukemia cells by activating ceramide synthase 6. Thus, we hypothesized that holotoxin A₁, which is structurally similar to cladoloside C₂, might induce apoptosis in human leukemia cells through the same molecular mechanism. In this paper, we compared holotoxin A₁ and cladoloside C₂ for killing potency and mechanism of action. We found that holotoxin A₁ induced apoptosis more potently than cladoloside C₂. Moreover, holotoxin A₁-induced apoptosis in K562 cells by activating caspase-8 and caspase-3, but not by activating caspase-9. During holotoxin A₁ induced apoptosis, acid sphingomyelinase (SMase) and neutral SMase were activated in both K562 cells and human primary leukemia cells. Specifically inhibiting acid SMase and neutral SMаse with chemical inhibitors or siRNAs significantly inhibited holotoxin A₁–induced apoptosis. These results indicated that holotoxin A₁ might induce apoptosis by activating acid SMase and neutral SMase. In conclusion, holotoxin A₁ represents a potential anticancer agent for treating leukemia. Moreover, the aglycone structure of marine triterpene glycosides might affect the mechanism involved in inducing apoptosis.

MiR-124 acts as a tumor suppressor by inhibiting the expression of sphingosine kinase 1 and its downstream signaling in head and neck squamous cell carcinoma

By analyzing the expression profile of microRNAs in head and neck squamous cell carcinomas (HNSCC), we found that the expression level of miR-124 was 4.59-fold lower in tumors than in normal tissues. To understand its functions, we generated a miR-124-expressing subline (JHU-22^miR124) and a mock vector-transfected subline (JHU-22^vec) by transfecting the mimic of miR-124 into JHU-22 cancer cells. Restored expression of miR-124 in JHU-22^miR124 cells led to reduced cell proliferation, delayed colony formation, and decreased tumor growth, indicating a tumor-suppressive effect of miR-124. Subsequent target search revealed that the 3′-UTR of SphK1 mRNA carries a complementary site for the seed region of miR-124. SphK1 was also detected to be overexpressed in HNSCC cell lines, but down-expressed in JHU-22^miR124 cells and tumor xenografts. These results suggest that SphK1 is a target of miR-124. To confirm this finding, we constructed a 3′-UTR-Luc-SphK1 vector and a binding site-mutated luciferase reporter vector. Co-transfection of 3′-UTR-Luc-SphK1 with miR-124 expression vector exhibited a 9-fold decrease in luciferase activity compared with mutated vector, suggesting that miR-124 inhibits SphK1 activity directly. Further studies on downstream signaling demonstrated accumulation of ceramide, increased expression of the pro-apoptotic Bax, BAD and PARP, decreased expression of the anti-apoptotic Bcl-2 and Bcl-xL, and enhanced expression of cytochrome c and caspase proteins in JHU-22^miR124 compared with JHU-22^vec cells and tumor xenografts. We conclude that miR-124 acts as a tumor suppressor in HNSCC by directly inhibiting SphK1 activity and its downstream signals.

Ceramide Nanoliposomes as a MLKL-Dependent, Necroptosis-Inducing, Chemotherapeutic Reagent in Ovarian Cancer

Ceramides are bioactive lipids that mediate cell death in cancer cells, and ceramide-based therapy is now being tested in dose-escalating phase I clinical trials as a cancer treatment. Multiple nanoscale delivery systems for ceramide have been proposed to overcome the inherent toxicities, poor pharmacokinetics, and difficult biophysics associated with ceramide. Using the ceramide nanoliposomes (CNL), we now investigate the therapeutic efficacy and signaling mechanisms of this nanoscale delivery platform in refractory ovarian cancer. Treatment of ovarian cancer cells with CNL decreased the number of living cells through necroptosis but not apoptosis. Mechanistically, dying SKOV3 ovarian cancer cells exhibit activation of pseudokinase mixed lineage kinase domain-like (MLKL) as evidenced by oligomerization and relocalization to the blebbing membranes, showing necroptotic characteristics. Knockdown of MLKL, but not its upstream protein kinases such as receptor-interacting protein kinases, with siRNA significantly abolished CNL-induced cell death. Monomeric MLKL protein expression inversely correlated with the IC50 values of CNL in distinct ovarian cancer cell lines, suggesting MLKL as a possible determinant for CNL-induced cell death. Finally, systemic CNL administration suppressed metastatic growth in an ovarian cancer cell xenograft model. Taken together, these results suggest that MLKL is a novel pronecroptotic target for ceramide in ovarian cancer models. Mol Cancer Ther; 17(1); 50-59. ©2017 AACR.

Plasma and ovarian tissue sphingolipids profiling in patients with advanced ovarian cancer

PURPOSE

The role of lipids in carcinogenesis through induction of abnormal cell lines in the human body is currently undisputable. Based on the literature, bioactive sphingolipids play an essential role in the development and progression of cancer and are involved in the metastatic process. The aim of this study was to determine the concentration of selected sphingolipids in patients with advanced ovarian cancer (AOC, FIGO III/IV, high grade ovarian cancer).

METHODS

Seventy-four patients with ovarian cancer were enrolled. Plasma concentrations of C16-Cer, C18:1-Cer and C18-Cer were assessed by LC/MS/MS. The content of tissue sphingolipids was measured using a UHPLC/MS/MS.

RESULTS

Plasma concentration of 3 ceramides: C16-Cer, C18:1-Cer and C18-Cer was significantly elevated in women with advanced ovarian cancer compared to control group (P=0.031; 0.022; 0.020; respectively). There were increases in concentration of 5 ceramides: C16-Cer, C18:1-Cer, C18-Cer, C24:1-Cer, C24-Cer (P=0.025; 0.049; 0.032; 0.005; 0.013, respectively) and S1P (P=0.004) in ovarian tissue of women with advanced ovarian cancer compared to healthy individuals. Importantly, significantly higher risk of ovarian cancer when the plasma concentration of C16-Cer>311.88ng/100μl (AUC: 0.76, P=0.0261); C18:1-Cer>4.75ng/100μl (AUC: 0.77, P=0.0160) and C18-Cer>100.76ng/100μl (AUC:0.77, P=0.0136) was noticed.

CONCLUSIONS

Bioactive sphingolipids play an essential role in the development and progression of cancer and they also take part in the process of metastasizing. This study suggests that some sphingolipids can be used as potential biomarkers of advanced ovarian cancer and that they can play an important role in the pathogenesis of this disease.

Anticancer actions of lysosomally targeted inhibitor, LCL521, of acid ceramidase

Acid ceramidase, which catalyzes ceramide hydrolysis to sphingosine and free fatty acid mainly in the lysosome, is being recognized as a potential therapeutic target for cancer. B13 is an effective and selective acid ceramidase inhibitor in vitro, but not as effective in cells due to poor access to the lysosomal compartment. In order to achieve targeting of B13 to the lysosome, we designed lysosomotropic N, N-dimethyl glycine (DMG)-conjugated B13 prodrug LCL521 (1,3-di-DMG-B13). Our previous results indicated the efficient delivery of B13 to the lysosome resulted in augmented effects of LCL521 on cellular acid ceramidase as evaluated by effects on substrate/product levels. Our current studies indicate that functionally, this translated into enhanced inhibition of cell proliferation. Moreover, there were greater synergistic effects of LCL521 with either ionizing radiation or Tamoxifen. Taken together, these results clearly indicate that compartmental targeting for the inhibition of acid ceramidase is an efficient and valuable therapeutic strategy.

Sphingomyelin generated by sphingomyelin synthase 1 is involved in attachment and infection with Japanese encephalitis virus

Japanese encephalitis virus (JEV) is a mosquito-borne RNA virus which infects target cells via the envelope protein JEV-E. However, its cellular targets are largely unknown. To investigate the role of sphingomyelin (SM) in JEV infection, we utilized SM-deficient immortalized mouse embryonic fibroblasts (tMEF) established from SM synthase 1 (SMS1)/SMS2 double knockout mice. SMS deficiency significantly reduced both intracellular and extracellular JEV levels at 48 h after infection. Furthermore, after 15 min treatment with JEV, the early steps of JEV infection such as attachment and cell entry were also diminished in SMS-deficient tMEFs. The inhibition of JEV attachment and infection were recovered by overexpression of SMS1 but not SMS2, suggesting SMS1 contributes to SM production for JEV attachment and infection. Finally, intraperitoneal injection of JEV into SMS1-deficient mice showed an obvious decrease of JEV infection and its associated pathologies, such as meningitis, lymphocyte infiltration, and elevation of interleukin 6, compared with wild type mice. These results suggest that SMS1-generated SM on the plasma membrane is related in JEV attachment and subsequent infection, and may be a target for inhibition of JEV infection.

Ceramide as a Target of Marine Triterpene Glycosides for Treatment of Human Myeloid Leukemia

Acute myeloid leukemia (AML) is a heterogeneous myeloid clonal disorder exhibiting the accumulation of immature myeloid progenitors in the bone marrow and peripheral blood. Standard AML therapy requires intensive combination chemotherapy, which leads to significant treatment-related toxicity. The search for new, low toxic marine agents, inducing the generation of ceramide in leukemic cells is a new approach to improve the therapy of leukemia. This review focuses on the metabolism of sphingolipids, the role of ceramide in treating leukemia, and the antitumor activity, related to ceramide metabolism, of some marine metabolites, particularly stichoposides, triterpene glycosides extracted from sea cucumbers of the family Stichopodiidae.

Regulation of membrane KCNQ1/KCNE1 channel density by sphingomyelin synthase 1

Sphingomyelin synthase (SMS) catalyzes the conversion of phosphatidylcholine and ceramide to sphingomyelin and diacylglycerol. We previously showed that SMS1 deficiency leads to a reduction in expression of the K(+) channel KCNQ1 in the inner ear (Lu MH, Takemoto M, Watanabe K, Luo H, Nishimura M, Yano M, Tomimoto H, Okazaki T, Oike Y, and Song WJ. J Physiol 590: 4029-4044, 2012), causing hearing loss. However, it remains unknown whether this change in expression is attributable to a cellular process or a systemic effect in the knockout animal. Here, we examined whether manipulation of SMS1 activity affects KCNQ1/KCNE1 currents in individual cells. To this end, we expressed the KCNQ1/KCNE1 channel in human embryonic kidney 293T cells and evaluated the effect of SMS1 manipulations on the channel using whole cell recording. Application of tricyclodecan-9-yl-xanthogenate, a nonspecific inhibitor of SMSs, significantly reduced current density and altered channel voltage dependence. Knockdown of SMS1 by a short hairpin RNA, however, reduced current density alone. Consistent with this, overexpression of SMS1 increased the current density without changing channel properties. Furthermore, application of protein kinase D inhibitors also suppressed current density without changing channel properties; this effect was nonadditive with that of SMS1 short hairpin RNA. These results suggest that SMS1 positively regulates KCNQ1/KCNE1 channel density in a protein kinase D-dependent manner.

Signaling Interplay between Bone Marrow Adipose Tissue and Multiple Myeloma cells

In the year 2000, Hanahan and Weinberg (1) defined the six Hallmarks of Cancer as: self-sufficiency in growth signals, evasion of apoptosis, insensitivity to antigrowth mechanisms, tissue invasion and metastasis, limitless replicative potential, and sustained angiogenesis. Eleven years later, two new Hallmarks were added to the list (avoiding immune destruction and reprograming energy metabolism) and two new tumor characteristics (tumor-promoting inflammation and genome instability and mutation) (2). In multiple myeloma (MM), a destructive cancer of the plasma cell that grows predominantly in the bone marrow (BM), it is clear that all these hallmarks and characteristics are in play, contributing to tumor initiation, drug resistance, disease progression, and relapse. Bone marrow adipose tissue (BMAT) is a newly recognized contributor to MM oncogenesis and disease progression, potentially affecting MM cell metabolism, immune action, inflammation, and influences on angiogenesis. In this review, we discuss the confirmed and hypothetical contributions of BMAT to MM development and disease progression. BMAT has been understudied due to technical challenges and a previous lack of appreciation for the endocrine function of this tissue. In this review, we define the dynamic, responsive, metabolically active BM adipocyte. We then describe how BMAT influences MM in terms of: lipids/metabolism, hypoxia/angiogenesis, paracrine or endocrine signaling, and bone disease. We then discuss the connection between BMAT and systemic inflammation and potential treatments to inhibit the feedback loops between BM adipocytes and MM cells that support MM progression. We aim for researchers to use this review to guide and help prioritize their experiments to develop better treatments or a cure for cancers, such as MM, that associate with and may depend on BMAT.