Therapeutic potential of targeting ceramide/glucosylceramide pathway in cancer

Using ultrasound and microbubble to enhance the effects of conventional cancer therapies in clinical settings

It has been demonstrated in preclinical research that the administration of microbubbles with ultrasound can augment the proapoptotic sphingolipid pathway and enhance chemotherapy or radiation therapy-induced vascular endothelial disruption resulting in enhanced tumor cell death. Specifically, ultrasound-stimulated microbubbles (USMB) can increase blood vessel permeability facilitating the release of therapeutic substances in the target area. USMB can also serve as a potential radiation enhancing therapy as USMB exposure increases tumor cell death significantly as observed in preclinical models. Clinical studies have found the combination of USMB and these existing cancer therapies to be safe and also to be associated with greater tumor responses. USMB-based treatment can be applicable in a clinical setting using either ultrasound imaging or magnetic resonance imaging (MRI) guidance for precise treatment. In the latter, the ultrasound device is integrated into the MRI system platform for sonication to facilitate microbubble stimulation. In this review, we concisely present findings related to USMB and existing cancer therapies (chemotherapy and radiation therapy) in clinical trial settings. The possible underlying mechanism involved in USMB-enhanced chemotherapy or radiotherapy enhancement is also discussed. Lastly, the study concludes with some limitations and an examination of the future direction of these combined therapies.

SC134-TCB Targeting Fucosyl-GM1, a T Cell-Engaging Antibody with Potent Antitumor Activity in Preclinical Small Cell Lung Cancer Models

Small cell lung cancer (SCLC) is an aggressive disease with limited treatment options. Fucosyl-GM1 (FucGM1) is a glycolipid overexpressed in the majority of SCLC tumors but virtually absent from normal healthy tissues. In this study, we validate a FucGM1-targeting T cell-redirecting bispecific (TCB) antibody for the treatment of SCLC. More than 80% of patient-derived xenograft tissues of SCLC expressed FucGM1, whereas only three normal human tissues: pituitary, thymus, and skin expressed low and focal FucGM1. A FucGM1-targeting TCB (SC134-TCB), based on the Fc-silenced humanized SC134 antibody, exhibited nanomolar efficiency in FucGM1 glycolipid and SCLC cell surface binding. SC134-TCB showed potent ex vivo killing of SCLC cell lines with donor-dependent EC50 ranging from 7.2 pmol/L up to 211.0 pmol/L, effectively activating T cells, with picomolar efficiency, coinciding with target-dependent cytokine production such as IFNγ, IL2, and TNFα and robust proliferation of both CD4 and CD8 T cells. The ex vivo SC134-TCB tumor controlling activity translated into an effective in vivo anti-DMS79 tumor therapy, resulting in 100% tumor-free survival in a human peripheral blood mononuclear cell admixed setting and 40% overall survival (55% tumor growth inhibition) with systemically administered human peripheral blood mononuclear cells. Combination treatment with atezolizumab further enhanced survival and tumor growth inhibition (up to 73%). A 10-fold SC134-TCB dose reduction maintained the strong in vivo antitumor impact, translating into 70% overall survival (P < 0.0001). Whole-blood incubation with SC134-TCB, as well as healthy human primary cells analysis, revealed no target-independent cytokine production. SC134-TCB presents an attractive candidate to deliver an effective immunotherapy treatment option for patients with SCLC.

Development of an advanced liquid chromatography-tandem mass spectrometry measurement system for simultaneous sphingolipid analysis

Mass spectrometry-based lipidomics approaches offer valuable tools for the detection and quantification of various lipid species, including sphingolipids. The present study aimed to develop a new method to simultaneously detect various sphingolipid species that applies to diverse biological samples. We developed and validated a measurement system by employing a single-column liquid chromatography-mass spectrometry system utilizing a normal-phase separation mode with positive ionization. The measurement system provided precision with a coefficient of variant below 20% for sphingolipids in all types of samples, and we observed good linearity in diluted serum samples. This system can measure the following sphingolipids: sphingosine 1-phosphate (S1P), sphingosine (Sph), dihydroS1P (dhS1P), dihydroSph (dhSph), ceramide 1-phosphate (Cer1P), hexosylceramide (HexCer), lactosylceramide (LacCer), dh-ceramide, deoxy-ceramide, deoxy-dh-ceramide, and sphingomyelin (SM). By measuring these sphingolipids in cell lysates where S1P lyase expression level was modulated, we could observe significant and dynamic modulations of sphingolipids in a comprehensive manner. Our newly established and validated measurement system can simultaneously measure many kinds of sphingolipids in biological samples. It holds great promise as a valuable tool for laboratory testing applications to detect overall modulations of sphingolipids, which have been proposed to be involved in pathogenesis processes in a series of elegant basic research studies.

Ceramides and their roles in programmed cell death

Programmed cell death plays a crucial role in maintaining the homeostasis and integrity of multicellular organisms, and its dysregulation contributes to the pathogenesis of many diseases. Programmed cell death is regulated by a range of macromolecules and low-molecular messengers, including ceramides. Endogenous ceramides have different functions, that are influenced by their localization and the presence of their target molecules. This article provides an overview of the current understanding of ceramides and their impact on various types of programmed cell death, including apoptosis, anoikis, macroautophagy and mitophagy, and necroptosis. Moreover, it highlights the emergence of dihydroceramides as a new class of bioactive sphingolipids and their downstream targets as well as their future roles in cancer cell growth, drug resistance and tumor metastasis.

Medicago Sativa Defensin1 as a tumor sensitizer for improving chemotherapy: translation from anti-fungal agent to a potential anti-cancer agent

Plant defensins including Medicago Sativa defensin 1 (MsDef1) are cysteine-rich antifungal peptides which are known for potent broad-spectrum antifungal activity against bacterial or fungal pathogens of plants. The antimicrobial activities of these cationic defensins are attributed to their capacity to bind to cell membranes to create potentially structural defects tin the cell membranes to interact with intracellular target (s) and mediates cytotoxic effects. Our earlier work identified Glucosylceramide (GlcCer) of fungus F. graminearum as a potential target for biological activity. Multi-drug resistant (MDR) cancer cells overexpress GlcCer on the surface of plasma membrane. Hence, MsDef1 may have a potential to bind to GlcCer of MDR cancer cells to induce cell death. We have characterized the three-dimensional structure of MsDef1 and the solution dynamics using of 15N-labeled MsDef1 nuclear magnetic resonance (NMR) spectroscopy which showed that GlcCer binds MsDef1 at two specific sites on the peptide molecule. The ability of MsDef1 to permeate MDR cancer cells was demonstrated by measuring the release of apoptotic ceramide in drug resistant MCF-7R cells. It was also shown that MsDef1 activated dual cell death pathways ceramide and Apoptosis Stimulating Kinase ASK1 by disintegrating GlcCer and oxidizing tumor specific biomarker thioredoxin (Trx) respectively. As a result, MsDef1 sensitizes MDR cancer cells to evoke a better response from Doxorubicin, a front-line chemotherapy for triple negative breast cancer (TNBC) treatment. The combination of MsDef1 and Doxorubicin induced 5 to10-fold greater apoptosis in vitro MDR cells MDA-MB-231R compared to either MsDef1 or Doxorubicin alone. Confocal microscopy revealed that MsDef1 facilitates a) influx of Doxorubicin in MDR cancer cells, b) preferential uptake by MDR cells but not by normal fibroblasts and breast epithelial cells (MCF-10A). These results suggest that MsDef1 targets MDR cancer cells and may find utility as a neoadjuvant chemotherapy. Hence, the extension of antifungal properties of MsDef1 to cancer my result in addressing the MDR problems in cancer.

Emerging Roles of Ceramides in Breast Cancer Biology and Therapy

One of the classic hallmarks of cancer is the imbalance between elevated cell proliferation and reduced cell death. Ceramide, a bioactive sphingolipid that can regulate this balance, has long been implicated in cancer. While the effects of ceramide on cell death and therapeutic efficacy are well established, emerging evidence indicates that ceramide turnover to downstream sphingolipids, such as sphingomyelin, hexosylceramides, sphingosine-1-phosphate, and ceramide-1-phosphate, is equally important in driving pro-tumorigenic phenotypes, such as proliferation, survival, migration, stemness, and therapy resistance. The complex and dynamic sphingolipid network has been extensively studied in several cancers, including breast cancer, to find key sphingolipidomic alterations that can be exploited to develop new therapeutic strategies to improve patient outcomes. Here, we review how the current literature shapes our understanding of how ceramide synthesis and turnover are altered in breast cancer and how these changes offer potential strategies to improve breast cancer therapy.

Total synthesis of ceramides and β-O-glucosylceramides via intramolecular fatty acyl group migration

Fatty acyl group utilized as both protection and migratory group for the synthesis of ceramides and glucosylceramides.

Lipidomic landscape in cancer: Actionable insights for membrane-based therapy and diagnoses

Cancer cells display altered cellular lipid metabolism, including disruption in endogenous lipid synthesis, storage, and exogenous uptake for membrane biogenesis and functions. Altered lipid metabolism and, consequently, lipid composition impacts cellular function by affecting membrane structure and properties, such as fluidity, rigidity, membrane dynamics, and lateral organization. Herein, we provide an overview of lipid membranes and how their properties affect cellular functions. We also detail how the rewiring of lipid metabolism impacts the lipidomic landscape of cancer cell membranes and influences the characteristics of cancer cells. Furthermore, we discuss how the altered cancer lipidome provides cues for developing lipid-inspired innovative therapeutic and diagnostic strategies while improving our limited understanding of the role of lipids in cancer initiation and progression. We also present the arcade of membrane characterization techniques to cement their relevance in cancer diagnosis and monitoring of treatment response.

Alterations in complex lipids in tumor tissue of patients with colorectal cancer

Background

Accumulating evidence indicates alterations in lipid metabolism and lipid composition in neoplastic tissue. Earlier nuclear magnetic resonance studies showed that the contents of major lipid groups, such as triacylglycerols, phospholipids and cholesterol, are changed in colon cancer tissue.

Methods

In this study, a more detailed analysis of lipids in cancer and tumor adjacent tissues from colorectal cancer patients, using liquid chromatography–mass spectrometry, allowed for comparison of 199 different lipids between cancer tissue and tumor adjacent tissue using principal component analysis.

Results

Significant differences were found in 67 lipid compounds between the two types of tissue; many of these lipid compounds are bioactive lipids such as ceramides, lysophospholipids or sterols and can influence the development of cancer. Additionally, increased levels of phospholipids and sphingolipids were present, which are major components of the cell membrane, and increases in these lipids can lead to changes in cell membrane properties.

Conclusions

This study showed that many complex lipids are significantly increased or decreased in colon cancer tissue, reflecting significant alterations in lipid metabolism. This knowledge can be used for the selection of potential molecular targets of novel anticancer strategies based on the modulation of lipid metabolism and the composition of the cell membrane in colorectal cancer cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-021-01512-x.

Ceramide glycosylation and related enzymes in cancer signaling and therapy

Ceramides, the core of the sphingolipid metabolism, draw wide attention as tumor suppressor, and act directly on mitochondria to trigger apoptotic cell death. Ceramide-based therapies are being developed by using promote ceramide generating agents. The ceramide metabolism balance is regulated by multifaceted factors in cancer development. Ceramide metabolic enzymes can increase the elimination of ceramide and counteract the anti-tumor effects of ceramide. However, recent research showed that these metabolic enzymes were highly expressed in several cancers. Especially ceramide glycosyltransferases, they catalyze ceramide glycosylation and synthesis the skeleton of glycosphingolipids (GSLs), play an important role in regulating tumor progression and have a significant correlation with the poor prognosis of cancer patients. To further understand the biological characteristics of ceramide metabolism in tumor, this review focuses on the role of ceramide glycosylation and related enzymes in cancer signaling and therapy. Besides, the research on multidrug resistance and potential inhibitors of ceramide glycosyltransferases are also discussed. Advance study on the structure of ceramide glycosyltransferases and ceramide glycosylation signaling pathway will open the path to new therapies and treatments.

Drug and Solute Transporters in Mediating Resistance to Novel Therapeutics in Multiple Myeloma

Multiple myeloma remains an incurable malignancy of plasma cells. Novel therapies, notably proteasome inhibitors and immunomodulatory drugs, have improved the survival of multiple myeloma patients; however, patients either present with, or develop resistance to, these therapies. Resistance to traditional chemotherapeutic agents can be caused by cellular drug efflux via adenosine triphosphate (ATP)-binding cassette (ABC) transporters, but it is still not clear whether these transporters mediate resistance to proteasome inhibitors and immunomodulatory drugs in multiple myeloma. Solute carrier (SLC) transporters also play a role in cancer drug resistance due to changes in cell homeostasis caused by their abnormal expression and changes in the solutes they transport. In this review, we evaluate resistance to novel therapies used to treat multiple myeloma, as mediated by drug and solute transporters.

Restoration of ceramide de novo synthesis by the synthetic retinoid ST1926 as it induces adult T-cell leukemia cell death

Ceramide (Cer) is a bioactive cellular lipid with compartmentalized and tightly regulated levels. Distinct metabolic pathways lead to the generation of Cer species with distinguishable roles in oncogenesis. Deregulation of Cer pathways has emerged as an important mechanism for acquired chemotherapeutic resistance. Adult T-cell leukemia (ATL) cells are defective in Cer synthesis. ATL is an aggressive neoplasm that develops following infection with human T-cell lymphotropic virus-1 (HTLV-1) where the viral oncogene Tax contributes to the pathogenesis of the disease. ATL cells, resistant to all-trans-retinoic acid, are sensitive to pharmacologically achievable concentrations of the synthetic retinoid ST1926. We studied the effects of ST1926 on Cer pathways in ATL cells. ST1926 treatment resulted in early Tax oncoprotein degradation in HTLV-1-treated cells. ST1926 induced cell death and a dose- and time-dependent accumulation of Cer in malignant T cells. The kinetics and degree of Cer production showed an early response upon ST1926 treatment. ST1926 enhanced de novo Cer synthesis via activation of ceramide synthase CerS(s) without inhibiting dihydroceramide desaturase, thereby accumulating Cer rather than the less bioactive dihydroceramide. Using labeling experiments with the unnatural 17-carbon sphinganine and measuring the generated Cer species, we showed that ST1926 preferentially induces the activities of a distinct set of CerS(s). We detected a delay in cell death response and interruption of Cer generation in response to ST1926 in Molt-4 cells overexpressing Bcl-2. These results highlight the potential role of ST1926 in inducing Cer levels, thus lowering the threshold for cell death in ATL cells.

Real-time lipid patterns to classify viable and necrotic liver tumors

Real-time tissue classifiers based on molecular patterns are emerging tools for fast tumor diagnosis. Here, we used rapid evaporative ionization mass spectrometry (REIMS) and multivariate statistical analysis (principal component analysis-linear discriminant analysis) to classify tissues with subsequent comparison to gold standard histopathology. We explored whether REIMS lipid patterns can identify human liver tumors and improve the rapid characterization of their underlying metabolic features. REIMS-based classification of liver parenchyma (LP), hepatocellular carcinoma (HCC), and metastatic adenocarcinoma (MAC) reached an accuracy of 98.3%. Lipid patterns of LP were more similar to those of HCC than to those of MAC and allowed clear distinction between primary and metastatic liver tumors. HCC lipid patterns were more heterogeneous than those of MAC, which is consistent with the variation seen in the histopathological phenotype. A common ceramide pattern discriminated necrotic from viable tumor in MAC with 92.9% accuracy and in other human tumors. Targeted analysis of ceramide and related sphingolipid mass features in necrotic tissues may provide a new classification of tumor cell death based on metabolic shifts. Real-time lipid patterns may have a role in future clinical decision-making in cancer precision medicine.

Identification of the Interactions Interference Between the PH and START Domain of CERT by Limonoid and HPA Inhibitors

The multi domain ceramide transfer protein (CERT) which contains the domains START and PH, is a protein that allows the transport of ceramide from the endoplasmic reticulum to the Golgi and so it plays a major role in sphingolipid metabolism. Recently, the crystal structure of the PH-START complex has been released, suggesting an inhibitory action of START to the binding of the PH domain to the Golgi apparatus and thus limiting the CERT activity. Our study presents a combination of docking and molecular dynamic simulations of N-(3-hydroxy-1-hydroxymethyl-3-phenylpropyl)alkanamides (HPA) analogs and limonoids compounds known to inhibit CERT. Through our computational study, we compared the binding affinity of 14 ligands at both domains (START and PH) and also at the START-PH interface, including several mutations known to play a role in the CERT’s activity. At the difference of HPA compounds, limonoids have a stronger binding affinity for the START-PH interface. Furthermore, 2 inhibitors (HPA-12 and isogedunin) were investigated through molecular dynamic (MD) simulations. 50 ns of molecular dynamic simulations have displayed the stability of isogedunin as well as keys residues in the binding of this molecule at the interface of the PH-START complex. Therefore, this study suggests a novel inhibitory mechanism of CERT for limonoid compounds involving the stabilization of the START-PH interface. This could help to develop new and potentially more selective inhibitors of this transporter, which is a potent target in cancer therapy.

New Insights Into Targeting Membrane Lipids for Cancer Therapy

Modulation of membrane lipid composition and organization is currently developing as an effective therapeutic strategy against a wide range of diseases, including cancer. This field, known as membrane-lipid therapy, has risen from new discoveries on the complex organization of lipids and between lipids and proteins in the plasma membranes. Membrane microdomains present in the membrane of all eukaryotic cells, known as lipid rafts, have been recognized as an important concentrating platform for protein receptors involved in the regulation of intracellular signaling, apoptosis, redox balance and immune response. The difference in lipid composition between the cellular membranes of healthy cells and tumor cells allows for the development of novel therapies based on targeting membrane lipids in cancer cells to increase sensitivity to chemotherapeutic agents and consequently defeat multidrug resistance. In the current manuscript strategies based on influencing cholesterol/sphingolipids content will be presented together with innovative ones, more focused in changing biophysical properties of the membrane bilayer without affecting the composition of its constituents.

Inhibition of glycosphingolipid biosynthesis reverts multidrug resistance by differentially modulating ABC transporters in chronic myeloid leukemias

Multidrug resistance (MDR) in cancer arises from cross-resistance to structurally- and functionally-divergent chemotherapeutic drugs. In particular, MDR is characterized by increased expression and activity of ATP-binding cassette (ABC) superfamily transporters. Sphingolipids are substrates of ABC proteins in cell signaling, membrane biosynthesis, and inflammation, for example, and their products can favor cancer progression. Glucosylceramide (GlcCer) is a ubiquitous glycosphingolipid (GSL) generated by glucosylceramide synthase, a key regulatory enzyme encoded by the UDP-glucose ceramide glucosyltransferase (UGCG) gene. Stressed cells increase de novo biosynthesis of ceramides, which return to sub-toxic levels after UGCG mediates incorporation into GlcCer. Given that cancer cells seem to mobilize UGCG and have increased GSL content for ceramide clearance, which ultimately contributes to chemotherapy failure, here we investigated how inhibition of GSL biosynthesis affects the MDR phenotype of chronic myeloid leukemias. We found that MDR is associated with higher UGCG expression and with a complex GSL profile. UGCG inhibition with the ceramide analog d-threo-1-(3,4,-ethylenedioxy)phenyl-2-palmitoylamino-3-pyrrolidino-1-propanol (EtDO-P4) greatly reduced GSL and monosialotetrahexosylganglioside levels, and co-treatment with standard chemotherapeutics sensitized cells to mitochondrial membrane potential loss and apoptosis. ABC subfamily B member 1 (ABCB1) expression was reduced, and ABCC-mediated efflux activity was modulated by competition with nonglycosylated ceramides. Consistently, inhibition of ABCC-mediated transport reduced the efflux of exogenous C₆-ceramide. Overall, UGCG inhibition impaired the malignant glycophenotype of MDR leukemias, which typically overcomes drug resistance through distinct mechanisms. This work sheds light on the involvement of GSL in chemotherapy failure, and its findings suggest that targeted GSL modulation could help manage MDR leukemias.

Glucosylceramide synthase silencing combined with the receptor tyrosine kinase inhibitor axitinib as a new multimodal strategy for glioblastoma

A great deal of evidence revealing that lipid metabolism is drastically altered during tumorigenesis has been accumulated. In this work, glucosylceramide synthase (GCS) was targeted, using RNA interference technology (siRNAs), in U87 and DBTRG human glioblastoma (GBM) cells, as in both cell types GCS showed to be overexpressed with respect to normal human astrocytes. The efficacy of a combined therapy to tackle GBM, allying GCS silencing to the new generation chemotherapeutics sunitinib and axitinib, or to the alkylating drugs etoposide and temozolomide, is evaluated here for the first time. With this purpose, studies addressing GBM cell viability and proliferation, cell cycle and apoptosis were performed, which revealed that combination of GCS silencing with axitinib treatment represents a promising therapeutic approach. The reduction of cell viability induced by this combined therapy is proposed to be mediated by excessive production of reactive oxygen species. This work, identifying GCS as a key molecular target to increase GBM susceptibility to a new generation chemotherapeutic, opens windows to the development of innovative strategies to halt GBM recurrence after surgical resection.

Development of a Label-Free LC-MS/MS-Based Glucosylceramide Synthase Assay and Its Application to Inhibitors Screening for Ceramide-Related Diseases

Ceramide metabolism is known to be an essential etiology for various diseases, such as atopic dermatitis and Gaucher disease. Glucosylceramide synthase (GCS) is a key enzyme for the synthesis of glucosylceramide (GlcCer), which is a main ceramide metabolism pathway in mammalian cells. In this article, we developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to determine GCS activity using synthetic non-natural sphingolipid C8-ceramide as a substrate. The reaction products, C8-GlcCer for GCS, could be separated on a C18 column by reverse-phase high-performance liquid chromatography (HPLC). Quantification was conducted using the multiple reaction monitoring (MRM) mode to monitor the precursor-to-product ion transitions of m/z 588.6 → 264.4 for C8-GlcCer at positive ionization mode. The calibration curve was established over the range of 0.625–160 ng/mL, and the correlation coefficient was larger than 0.999. This method was successfully applied to detect GCS in the human hepatocellular carcinoma cell line (HepG2 cells) and mouse peripheral blood mononuclear cells. We also evaluated the inhibition degree of a known GCS inhibitor 1-phenyl-2-decanoylamino-3-morpholino-1-propanol (PDMP) on GCS enzymatic activity and proved that this method could be successfully applied to GCS inhibitor screening of preventive and therapeutic drugs for ceramide metabolism diseases, such as atopic dermatitis and Gaucher disease.

Selective Targeting of the Interconversion between Glucosylceramide and Ceramide by Scaffold Tailoring of Iminosugar Inhibitors

A series of simple C-alkyl pyrrolidines already known as cytotoxic inhibitors of ceramide glucosylation in melanoma cells can be converted into their corresponding 6-membered analogues by means of a simple ring expansion. This study illustrated how an isomerisation from iminosugar pyrrolidine toward piperidine could invert their targeting from glucosylceramide (GlcCer) formation toward GlcCer hydrolysis. Thus, we found that the 5-membered ring derivatives did not inhibit the hydrolysis reaction of GlcCer catalysed by lysosomal β-glucocerebrosidase (GBA). On the other hand, the ring-expanded C-alkyl piperidine isomers, non-cytotoxic and inactive regarding ceramide glucosylation, revealed to be potent inhibitors of GBA. A molecular docking study showed that the positions of the piperidine ring of the compound 6b and its analogous 2-O-heptyl DIX 8 were similar to that of isofagomine. Furthermore, compound 6b promoted mutant GBA enhancements over 3-fold equivalent to that of the related O-Hept DIX 8 belonging to one of the most potent iminosugar-based pharmacological chaperone series reported to date.

Perturbing the Dynamics and Organization of Cell Membrane Components: A New Paradigm for Cancer-Targeted Therapies

Cancer is a multi-process disease where different mechanisms exist in parallel to ensure cell survival and constant adaptation to the extracellular environment. To adapt rapidly, cancer cells re-arrange their plasma membranes to sustain proliferation, avoid apoptosis and resist anticancer drugs. In this review, we discuss novel approaches based on the modifications and manipulations that new classes of molecules can exert in the plasma membrane lateral organization and order of cancer cells, affecting growth factor signaling, invasiveness, and drug resistance. Furthermore, we present azurin, an anticancer protein from bacterial origin, as a new approach in the development of therapeutic strategies that target the cell membrane to improve the existing standard therapies.

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.

Sphingolipid metabolism and drug resistance in ovarian cancer

Despite progress in understanding molecular aberrations that contribute to the development and progression of ovarian cancer, virtually all patients succumb to drug resistant disease at relapse. Emerging data implicate bioactive sphingolipids and regulation of sphingolipid metabolism as components of response to chemotherapy or development of resistance. Increases in cytosolic ceramide induce apoptosis in response to therapy with multiple classes of chemotherapeutic agents. Aberrations in sphingolipid metabolism that accelerate the catabolism of ceramide or that prevent the production and accumulation of ceramide contribute to resistance to standard of care platinum- and taxane-based agents. The aim of this review is to highlight current literature and research investigating the influence of the sphingolipids and enzymes that comprise the sphingosine-1-phosphate pathway on the progression of ovarian cancer. The focus of the review is on the utility of sphingolipid-centric therapeutics as a mechanism to circumvent drug resistance in this tumor type.

Small-Molecule Modulation of Lipid-Dependent Cellular Processes against Cancer: Fats on the Gunpoint

Lipid cell membrane composed of various distinct lipids and proteins act as a platform to assemble various signaling complexes regulating innumerous cellular processes which are strongly downregulated or altered in cancer cells emphasizing the still-underestimated critical function of lipid biomolecules in cancer initiation and progression. In this review, we outline the current understanding of how membrane lipids act as signaling hot spots by generating distinct membrane microdomains called rafts to initiate various cellular processes and their modulation in cancer phenotypes. We elucidate tangible drug targets and pathways all amenable to small-molecule perturbation. Ranging from targeting membrane rafts organization/reorganization to rewiring lipid metabolism and lipid sorting in cancer, the work summarized here represents critical intervention points being attempted for lipid-based anticancer therapy and future directions.

Pharmacophore Identification and Scaffold Exploration to Discover Novel, Potent, and Chemically Stable Inhibitors of Acid Ceramidase in Melanoma Cells

Acid ceramidase (AC) hydrolyzes ceramides, which are central lipid messengers for metabolism and signaling of sphingolipids. A growing body of evidence links deregulation of sphingolipids to several diseases, including cancer. Indeed, AC expression is abnormally high in melanoma cells. AC inhibition may thus be key to treating malignant melanoma. Here, we have used a systematic scaffold exploration to design a general pharmacophore for AC inhibition. This pharmacophore comprises a 6 + 5 fused ring heterocycle linked to an aliphatic substituent via a urea moiety. We have thus identified the novel benzimidazole derivatives 10, 21, 27, and 30, which are highly potent AC inhibitors. Their chemical and metabolic stabilities are comparable or superior to those of previously reported AC inhibitors. Moreover, they are potent against endogenous AC in intact melanoma cells. These novel inhibitors merit further characterization and can serve as a promising starting point for the discovery of new antimelanoma therapeutics.

Recent advances in understanding noroviruses

Noroviruses are the leading cause of acute gastroenteritis around the world. An individual living in the United States is estimated to develop norovirus infection five times in his or her lifetime. Despite this, there is currently no antiviral or vaccine to combat the infection, in large part because of the historical lack of cell culture and small animal models. However, the last few years of norovirus research were marked by a number of ground-breaking advances that have overcome technical barriers and uncovered novel aspects of norovirus biology. Foremost among them was the development of two different in vitro culture systems for human noroviruses. Underappreciated was the notion that noroviruses infect cells of the immune system as well as epithelial cells within the gastrointestinal tract and that human norovirus infection of enterocytes requires or is promoted by the presence of bile acids. Furthermore, two proteinaceous receptors are now recognized for murine norovirus, marking the first discovery of a functional receptor for any norovirus. Recent work further points to a role for certain bacteria, including those found in the gut microbiome, as potential modulators of norovirus infection in the host, emphasizing the importance of interactions with organisms from other kingdoms of life for viral pathogenesis. Lastly, we will highlight the adaptation of drop-based microfluidics to norovirus research, as this technology has the potential to reveal novel insights into virus evolution. This review aims to summarize these new findings while also including possible future directions.

Enhanced expression of hydroxylated ceramide in well-differentiated endometrial adenocarcinoma

Based on our previous analysis of neutral glycolipids in the human endometrium, the present authors already reported that the concentrations of glucosylceramide, lactosylceramide and globotriaosylceramide (Gb₃Cer), in which both fatty acids and sphingosines in the ceramides are hydroxylated, exhibit a marked increase during the luteal phase of the menstrual cycle. It is also well known that poorly differentiated endometrial adenocarcinoma exhibits a more rapid progression and a worse response to therapy than well-differentiated endometrial adenocarcinoma. To examine the molecular background of well-differentiated and poorly differentiated cancers, the levels of neutral glycolipids in tumor tissues from endometrial carcinoma displaying different degrees of differentiation were measured. The composition of neutral glycolipids in tumor tissues was determined, and ceramide structures that were specifically expressed in well-differentiated endometrial carcinomas were investigated using biochemical analytical methods, including lipid extraction, enzyme digestion, thin-layer chromatography (TLC), gas-liquid chromatography and mass spectrometry. Well-differentiated adenocarcinoma contained numerous structurally unknown glycolipids that exhibited slower migration than globotetraosylceramide (Gb₄Cer). In the case of Gb₃Cer, three bands appeared on TLC in well-differentiated cancer, but only two bands appeared in the poorly-differentiated cancer. This difference was associated with the fatty acid composition of ceramide, since non-hydroxy fatty acids with ≥20 carbon atoms were increased in well-differentiated cancer, while α-hydroxy fatty acids were increased in poorly differentiated cancer. Similarly, there were two bands on TLC of Gb₄Cer from well-differentiated cancer, but only one band in poorly differentiated cancer, and the long-chain base of ceramide was observed to contain phytosphingosine in well-differentiated cancer. It was demonstrated in endometrial cancer that the structure of ceramide molecules changes with the extent of tumor differentiation. These findings suggest that hydroxylated ceramides contribute to the well-differentiated phenotype of endometrial adenocarcinoma.

Cell membrane modulation as adjuvant in cancer therapy

Cancer is a complex disease involving numerous biological processes, which can exist in parallel, can be complementary, or are engaged when needed and as such can replace each other. This redundancy in possibilities cancer cells have, are fundamental to failure of therapy. However, intrinsic features of tumor cells and tumors as a whole provide also opportunities for therapy. Here we discuss the unique and specific makeup and arrangement of cell membranes of tumor cells and how these may help treatment. Interestingly, knowledge on cell membranes and associated structures is present already for decades, while application of membrane modification and manipulation as part of cancer therapy is lagging. Recent developments of scientific tools concerning lipids and lipid metabolism, opened new and previously unknown aspects of tumor cells and indicate possible differences in lipid composition and membrane function of tumor cells compared to healthy cells. This field, coined Lipidomics, demonstrates the importance of lipid components in cell membrane in several illnesses. Important alterations in cancer, and specially in resistant cancer cells compared to normal cells, opened the door to new therapeutic strategies. Moreover, the ability to modulate membrane components and/or properties has become a reality. Here, developments in cancer-related Lipidomics and strategies to interfere specifically with cancer cell membranes and how these affect cancer treatment are discussed. We hypothesize that combination of lipid or membrane targeted strategies with available care to improve chemotherapy, radiotherapy and immunotherapy will bring the much needed change in treatment in the years to come.

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.

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.

Glucose availability and glycolytic metabolism dictate glycosphingolipid levels

Cancer therapeutics has seen an emergence and re-emergence of two metabolic fields in recent years, those of bioactive sphingolipids and glycolytic metabolism. Anaerobic glycolysis and its implications in cancer have been at the forefront of cancer research for over 90 years. More recently, the role of sphingolipids in cancer cell metabolism has gained recognition, notably ceramide's essential role in programmed cell death and the role of the glucosylceramide synthase (GCS) in chemotherapeutic resistance. Despite this knowledge, a direct link between these two fields has yet to be definitively drawn. Herein, we show that in a model of highly glycolytic cells, generation of the glycosphingolipid (GSL) glucosylceramide (GlcCer) by GCS was elevated in response to increased glucose availability, while glucose deprivation diminished GSL levels. This effect was likely substrate dependent, independent of both GCS levels and activity. Conversely, leukemia cells with elevated GSLs showed a significant change in GCS activity, but no change in glucose uptake or GCS expression. In a leukemia cell line with elevated GlcCer, treatment with inhibitors of glycolysis or the pentose phosphate pathway (PPP) significantly decreased GlcCer levels. When combined with pre-clinical inhibitor ABT-263, this effect was augmented and production of pro-apoptotic sphingolipid ceramide increased. Taken together, we have shown that there exists a definitive link between glucose metabolism and GSL production, laying the groundwork for connecting two distinct yet essential metabolic fields in cancer research. Furthermore, we have proposed a novel combination therapeutic option targeting two metabolic vulnerabilities for the treatment of leukemia.

Tissue biomarkers of drug efficacy: case studies using a MALDI-MSI workflow

MALDI MS imaging (MALDI-MSI) offers a capability to not only evaluate the distribution, localization and metabolism of drugs within tissues but also allow correlative tissue measurement of the effect of the drug on biomolecules in the targeted pathway. Particularly for MALDI-MSI, lipid molecules are readily detectable within tissues. Case study examples are provided for two different drugs targeting the sphingosine-1-phosphate/ceramide nexus in tumor xenograft tissues. A workflow combining high-resolution MALDI-MSI with on-tissue confirmation of targeted compounds using a structural library and on-tissue enzymatic digestion strategy is described. Representative images of drug metabolite distribution that correlate to an increase or decrease in sphingosine-1-phosphate or ceramide species are provided.

Elisidepsin Interacts Directly with Glycosylceramides in the Plasma Membrane of Tumor Cells to Induce Necrotic Cell Death

Plasma membrane integrity is essential for cell life. Any major break on it immediately induces the death of the affected cell. Different molecules were described as disrupting this cell structure and thus showing antitumor activity. We have previously defined that elisidepsin (Irvalec^®, PM02734) inserts and self-organizes in the plasma membrane of tumor cells, inducing a rapid loss of membrane integrity, cell permeabilization and necrotic death. Here we show that, in sensitive HCT-116 colorectal cells, all these effects are consequence of the interaction of elisidepsin with glycosylceramides in the cell membrane. Of note, an elisidepsin-resistant subline (HCT-116-Irv) presented reduced levels of glycosylceramides and no accumulation of elisidepsin in the plasma membrane. Consequently, drug treatment did not induce the characteristic necrotic cell death. Furthermore, GM95, a mutant derivative from B16 mouse melanoma cells lacking ceramide glucosyltransferase (UGCG) activity and thus the synthesis of glycosylceramides, was also resistant to elisidepsin. Over-expression of UGCG gene in these deficient cells restored glycosylceramides synthesis, rendering them sensitive to elisidepsin, at a similar level than parental B16 cells. These results indicate that glycosylceramides act as membrane targets of elisidepsin, facilitating its insertion in the plasma membrane and the subsequent membrane permeabilization that leads to drug-induced cell death. They also indicate that cell membrane lipids are a plausible target for antineoplastic therapy.

Phenotypic malignant changes and untargeted lipidomic analysis of long-term exposed prostate cancer cells to endocrine disruptors

Endocrine disruptors (EDs) are a class of environmental toxic molecules able to interfere with the normal hormone metabolism. Numerous studies involve EDs exposure to initiation and development of cancers, including prostate cancer. In this work, three different EDs (aldrin, aroclor 1254 and chlorpyrifos (CPF)) were investigated as potential inducers of a malignant phenotype in DU145 prostate cancer cells after a chronic exposure. Epithelial to mesenchymal transition (EMT) induction, proliferation, migration, colony formation and release of metalloproteinase 2 (MMP-2) were analyzed in 50-day exposed cells to the selected EDs. As a result, aldrin and CPF exposure led to an EMT induction (loss of 16% and 14% of E-cadherin levels, respectively, compared to the unexposed cells). Aroclor and CPF presented an increased migration (134% and 126%, respectively), colony formation (204% and 144%, respectively) and MMP-2 release (137% in both cases) compared to the unexposed cells. An untargeted lipidomic analysis was performed to decipher the lipids involved in the observed transformations. As general results, aldrin exposure showed a global decrease in phospholipids and sphingolipids, and aroclor and CPF showed an increase of certain phospholipids, glycosphingolipids as well as a remarkable increase of some cardiolipin species. Furthermore, the three exposures resulted in an increase of some triglyceride species. In conclusion, some significant changes in lipids were identified and thus we postulate that some lipid compounds and lipid metabolic pathways could be involved in the acquisition of the malignant phenotype in exposed prostate cancer cells to the selected EDs.

Δ10(E)-Sphingolipid Desaturase Involved in Fusaruside Mycosynthesis and Stress Adaptation in Fusarium graminearum

Sphingolipids are biologically important and structurally distinct cell membrane components. Fusaruside (1) is a 10,11-unsaturated immunosuppressive fungal sphingolipid with medical potentials for treating liver injury and colitis, but its poor natural abundance bottlenecks its druggability. Here, fusaruside is clarified biosynthetically, and its efficacy-related 10,11-double bond can be generated under the regioselective catalysis of an unprecedented Δ10(E)-sphingolipid desaturase (Δ10(E)-SD). Δ10(E)-SD shares 17.7% amino acid sequence similarity with a C9-unmethylated Δ10-sphingolipid desaturase derived from a marine diatom, and 55.7% with Δ8(E)-SD from Fusarium graminearum. Heterologous expression of Δ10(E)-SD in Pichia pastoris has been established to facilitate a reliable generation of 1 through the Δ10(E)-SD catalyzed desaturation of cerebroside B (2), an abundant fungal sphingolipid. Site directed mutageneses show that the conserved histidines of Δ10(E)-SD are essential for the 10,11-desaturation catalysis, which is also preconditioned by the C9-methylation of the substrate. Moreover, Δ10(E)-SD confers improved survival and faster growth to fungal strains at low temperature and high salinity, in parallel with to higher contents of 1 in the mycelia. Collectively, the investigation describes a new Δ10(E)-sphingolipid desaturase with its heterologous expression fundamentalizing a biotechnological supply of 1, and eases the follow-up clarification of the immunosuppression and stress-tolerance mechanism.

Global profiling of metabolic adaptation to hypoxic stress in human glioblastoma cells

Oncogenetic events and unique phenomena of the tumor microenvironment together induce adaptive metabolic responses that may offer new diagnostic tools and therapeutic targets of cancer. Hypoxia, or low oxygen tension, represents a well-established and universal feature of the tumor microenvironment and has been linked to increased tumor aggressiveness as well as resistance to conventional oncological treatments. Previous studies have provided important insights into hypoxia induced changes of the transcriptome and proteome; however, how this translates into changes at the metabolite level remains to be defined. Here, we have investigated dynamic, time-dependent effects of hypoxia on the cancer cell metabolome across all families of macromolecules, i.e., carbohydrate, protein, lipid and nucleic acid, in human glioblastoma cells. Using GC/MS and LC/MS/MS, 345 and 126 metabolites were identified and quantified in cells and corresponding media, respectively, at short (6 h), intermediate (24 h), and prolonged (48 h) incubation at normoxic or hypoxic (1% O₂) conditions. In conjunction, we performed gene array studies with hypoxic and normoxic cells following short and prolonged incubation. We found that levels of several key metabolites varied with the duration of hypoxic stress. In some cases, metabolic changes corresponded with hypoxic regulation of key pathways at the transcriptional level. Our results provide new insights into the metabolic response of glioblastoma cells to hypoxia, which should stimulate further work aimed at targeting cancer cell adaptive mechanisms to microenvironmental stress.

Biological functionalization of drug delivery carriers to bypass size restrictions of receptor-mediated endocytosis independently from receptor targeting

Targeting of drug carriers to cell-surface receptors involved in endocytosis is commonly used for intracellular drug delivery. However, most endocytic receptors mediate uptake via clathrin or caveolar pathways associated with ≤200-nm vesicles, restricting carrier design. We recently showed that endocytosis mediated by intercellular adhesion molecule 1 (ICAM-1), which differs from clathrin- and caveolae-mediated pathways, allows uptake of nano- and microcarriers in cell culture and in vivo due to recruitment of cellular sphingomyelinases to the plasmalemma. This leads to ceramide generation at carrier binding sites and formation of actin stress-fibers, enabling engulfment and uptake of a wide size-range of carriers. Here we adapted this paradigm to enhance uptake of drug carriers targeted to receptors associated with size-restricted pathways. We coated sphingomyelinase onto model (polystyrene) submicro- and microcarriers targeted to clathrin-associated mannose-6-phosphate receptor. In endothelial cells, this provided ceramide enrichment at the cell surface and actin stress-fiber formation, modifying the uptake pathway and enhancing carrier endocytosis without affecting targeting, endosomal transport, cell-associated degradation, or cell viability. This improvement depended on the carrier size and enzyme dose, and similar results were observed for other receptors (transferrin receptor) and cell types (epithelial cells). This phenomenon also enhanced tissue accumulation of carriers after intravenous injection in mice. Hence, it is possible to maintain targeting toward a selected receptor while bypassing natural size restrictions of its associated endocytic route by functionalization of drug carriers with biological elements mimicking the ICAM-1 pathway. This strategy holds considerable promise to enhance flexibility of design of targeted drug delivery systems.

Reduced glucosylceramide in the mouse model of Fabry disease: correction by successful enzyme replacement therapy

Fabry disease is an X-linked lysosomal storage disease (LSD) caused by deficient activity of α-Galactosidase A (α-Gal A). As a result, glycosphingolipids, mainly globotriaosylceramide (Gb3), progressively accumulate in body fluids and tissues. Studies aiming at the identification of secondary lipid alterations in Fabry disease may be potentially useful for the monitorization of the response to enzyme replacement therapy (ERT) and development of future therapies. The focus of this study was to evaluate if α-Gal A deficiency has an effect on two key groups of molecules of sphingolipids metabolism: glucosylceramides (GlucCers) and ceramides (Cers). Studies performed in a mouse model of Fabry disease showed reduced level of GlucCer and normal level of Cer in plasma, liver, spleen, kidney and heart. Moreover, analysis of GlucCer isoforms in Fabry knockout mice showed that GlucCer isoforms are unequally reduced in different tissues of these animals. ERT had a specific effect on the liver's GlucCer levels of Fabry knockout mice, increasing hepatic GlucCer to the levels observed in wild type mice. In contrast to Fabry knockout mice, plasma of Fabry patients had normal GlucCer and Cer but an increased GlucCer/Cer ratio. This alteration showed a positive correlation with plasma globotriaosylsphingosine (lyso-Gb3) concentration. In conclusion, this work reveals novel secondary lipid imbalances caused by α-Gal A deficiency.

Biophysics of cell membrane lipids in cancer drug resistance: Implications for drug transport and drug delivery with nanoparticles

In this review, we focus on the biophysics of cell membrane lipids, particularly when cancers develop acquired drug resistance, and how biophysical changes in resistant cell membrane influence drug transport and nanoparticle-mediated drug delivery. Recent advances in membrane lipid research show the varied roles of lipids in regulating membrane P-glycoprotein function, membrane trafficking, apoptotic pathways, drug transport, and endocytic functions, particularly endocytosis, the primary mechanism of cellular uptake of nanoparticle-based drug delivery systems. Since acquired drug resistance alters lipid biosynthesis, understanding the role of lipids in cell membrane biophysics and its effect on drug transport is critical for developing effective therapeutic and drug delivery approaches to overcome drug resistance. Here we discuss novel strategies for (a) modulating the biophysical properties of membrane lipids of resistant cells to facilitate drug transport and regain endocytic function and (b) developing effective nanoparticles based on their biophysical interactions with membrane lipids to enhance drug delivery and overcome drug resistance.

High-throughput screen identifies disulfiram as a potential therapeutic for triple-negative breast cancer cells: interaction with IQ motif-containing factors

Triple-negative breast cancer (TNBC) represents an aggressive subtype, for which radiation and chemotherapy are the only options. Here we describe the identification of disulfiram, an FDA-approved drug used to treat alcoholism, as well as the related compound thiram, as the most potent growth inhibitors following high-throughput screens of 3185 compounds against multiple TNBC cell lines. The average IC₅₀ for disulfiram was ~300 nM. Drug affinity responsive target stability (DARTS) analysis identified IQ motif-containing factors IQGAP1 and MYH9 as direct binding targets of disulfiram. Indeed, knockdown of these factors reduced, though did not completely abolish, cell growth. Combination treatment with 4 different drugs commonly used to treat TNBC revealed that disulfiram synergizes most effectively with doxorubicin to inhibit cell growth of TNBC cells. Disulfiram and doxorubicin cooperated to induce cell death as well as cellular senescence, and targeted the ESA⁺/CD24^-/low/CD44⁺ cancer stem cell population. Our results suggest that disulfiram may be repurposed to treat TNBC in combination with doxorubicin.

Acid ceramidase as a therapeutic target in metastatic prostate cancer

Acid ceramidase (AC) catalyzes the hydrolysis of ceramide into sphingosine, in turn a substrate of sphingosine kinases that catalyze its conversion into the mitogenic sphingosine-1-phosphate. AC is expressed at high levels in several tumor types and has been proposed as a cancer therapeutic target. Using a model derived from PC-3 prostate cancer cells, the highly tumorigenic, metastatic, and chemoresistant clone PC-3/Mc expressed higher levels of the AC ASAH1 than the nonmetastatic clone PC-3/S. Stable knockdown of ASAH1 in PC-3/Mc cells caused an accumulation of ceramides, inhibition of clonogenic potential, increased requirement for growth factors, and inhibition of tumorigenesis and lung metastases. We developed de novo ASAH1 inhibitors, which also caused a dose-dependent accumulation of ceramides in PC-3/Mc cells and inhibited their growth and clonogenicity. Finally, immunohistochemical analysis of primary prostate cancer samples showed that higher levels of ASAH1 were associated with more advanced stages of this neoplasia. These observations confirm ASAH1 as a therapeutic target in advanced and chemoresistant forms of prostate cancer and suggest that our new potent and specific AC inhibitors could act by counteracting critical growth properties of these highly aggressive tumor cells.