In vivo efficacy of a novel liposomal formulation of safingol in the treatment of acute myeloid leukemia

Sphingolipids and Lymphomas: A Double-Edged Sword

Lymphomas are a highly heterogeneous group of hematological neoplasms. Given their ethiopathogenic complexity, their classification and management can become difficult tasks; therefore, new approaches are continuously being sought. Metabolic reprogramming at the lipid level is a hot topic in cancer research, and sphingolipidomics has gained particular focus in this area due to the bioactive nature of molecules such as sphingoid bases, sphingosine-1-phosphate, ceramides, sphingomyelin, cerebrosides, globosides, and gangliosides. Sphingolipid metabolism has become especially exciting because they are involved in virtually every cellular process through an extremely intricate metabolic web; in fact, no two sphingolipids share the same fate. Unsurprisingly, a disruption at this level is a recurrent mechanism in lymphomagenesis, dissemination, and chemoresistance, which means potential biomarkers and therapeutical targets might be hiding within these pathways. Many comprehensive reviews describing their role in cancer exist, but because most research has been conducted in solid malignancies, evidence in lymphomagenesis is somewhat limited. In this review, we summarize key aspects of sphingolipid biochemistry and discuss their known impact in cancer biology, with a particular focus on lymphomas and possible therapeutical strategies against them.

Targeting Sphingolipids for Cancer Therapy

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

Targeting Approaches of Nanomedicines in Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a hematological malignancy, which is commonly associated with high incidence and mortality among adult patients. The standard induction regimen for AML has been substantially unchanged over the past 40 years, for which novel nanomedicines have represented a promising strategy in AML therapies. Despite developments of multiple nanoparticles formulated with drugs or genes, less there is not much information available about approaches in AML is available. This review presents an overview of nanomedicines currently being evaluated in AML. First, it briefly summarized conventional chemotherapies in use. Second, nanomedicines presently ongoing in clinical trials or preclinical researches were classified and described, with illustrative examples from recent literatures. Finally, limitations and potential safety issues concerns in clinical translation of AML treatment were discussed as well.

Hydrophilic interaction liquid chromatography-tandem mass spectrometric approach for simultaneous determination of safingol and D-erythro-sphinganine in human plasma

A simple and specific hydrophilic interaction liquid chromatography-tandem mass spectrometry (HILIC-MS/MS) method was developed for the simultaneous determination of C18-L-threo-sphinganine (safingol, an anti-neoplastic in phase I trials) and its diastereomer, C18-D-erythro-sphinganine (sphinganine), in human plasma. Sample pretreatment involved a protein precipitation with methanol using 25 μL aliquots of plasma. Chromatographic separation of the diastereomers and C17-D-erythro-sphinganine, an internal standard, was achieved on a Xbridge HILIC (3.5 μm, 100 × 2.1 mm) using isocratic elution with the mobile phase of 2 mM ammonium bicarbonate in water (pH 8.3) and acetonitrile at a flow rate of 0.3 mL/min. Electrospray ionization (ESI) mass spectrometry was operated in the positive ion mode with multiple reaction monitoring (MRM). The calibration curves obtained were linear over the concentration range of 0.2-100 ng/mL with a lower limit of quantification of 0.2 ng/mL. The relative standard deviation of intra-day and inter-day precision was below 8.27%, and the accuracy ranged from 92.23 to 110.06%. The extraction recoveries were found to be higher than 93.22% and IS-normalized matrix effect was higher than 90.92%. The analytes were stable for the durations of the stability studies. The validated method was successfully applied to the analyses of pharmacokinetic samples from patients treated with safingol and all-trans-N-(4-hydroxyphenyl)retinamide; (fenretinide, 4-HPR) in a current phase I clinical trial (SPOC-2010-002, ClinicalTrials.gov Identifier: NCT01553071).

Is LukS-PV a novel experimental therapy for leukemia?

Although the studies on the pathogenesis and prognosis of leukemia have made revolutionary progress, the long-term survival remains unsatisfactory. Alternative techniques are being developed to target leukemia. Several decades after researchers' work, a variety of bacteria toxins are being explored as potential anti-leukemia agents, either to provide direct effects or to deliver therapeutic proteins to leukemia. LukS-PV, a component of Panton-Valentine Leukocidin secreted by S. aureus, has been tested in acute myeloid leukemia as a novel experimental strategy. Further researches about the targeting mechanisms of LukS-PV are required to make it a complete therapeutic approach for leukemia treatment. The function of this article is to provide clinicians and experimentalists with a chronological and comprehensive appraisal of use of LukS-PV as an experimental strategy for leukemia therapy.

Layer-by-layer assembly of liposomal nanoparticles with PEGylated polyelectrolytes enhances systemic delivery of multiple anticancer drugs

Layer-by-layer (LbL)-engineered nanoparticles (NPs) are a promising group of therapeutic carriers used in an increasing number of biomedical applications. The present study uses a controlled LbL process to create a multidrug-loaded nanoplatform capable of promoting blood circulation time, biodistribution profile and controlling drug release in the dynamic systemic environment. LbL assembly is achieved by sequential deposition of poly-l-lysine (PLL) and poly(ethylene glycol)-block-poly(l-aspartic acid) (PEG-b-PLD) on liposomal nanoparticles (LbL-LNPs). This generates spherical and stable multilayered NPs ∼240nm in size, enabling effective systemic administration. The numerous functional groups and compartments in the polyelectrolyte shell and core facilitate loading with doxorubicin and mitoxantrone. The nanoarchitecture effectively controls burst release, providing different release kinetics for each drug. LbL-LNPs are pH-sensitive, indicating that intracellular drug release can be increased by the acidic milieu of cancer cells. We further demonstrate that the LbL nanoarchitecture significantly reduces the elimination rates of both drugs tested and markedly extends their systemic circulation times, paving the way for efficacious tumor drug delivery. Because this delivery system accommodates multiple drugs, improves drug half-life and diminishes burst release, it provides an exciting platform with remarkable potential for combination therapeutics in cancer therapy.

Liposomal codelivery of a synergistic combination of bioactive lipids in the treatment of acute myeloid leukemia

Aim: The aim of this work was to develop a liposomal formulation to facilitate delivery of a synergistic safingol/C2-ceramide combination in the treatment of acute myeloid leukemia (AML). Materials & methods: Liposomes were prepared using the extrusion method and the bioactive lipids were encapsulated passively. Drug concentrations were determined by liquid chromatography tandem mass spectrometry. Antileukemic activity was evaluated using human leukemic cell lines, patient samples and U937 leukemic xenograft models. Results: A stable liposome formulation was developed to coencapsulate safingol and C2-ceramide at 1:1 molar ratio with >90% encapsulation efficiency. The liposomal safingol/C2-ceramide was effective in AML cell lines, patient samples and murine xenograft models of AML, compared with liposomal safingol or liposomal C2-ceramide alone despite a dose reduction of 33%. Conclusion: Our study provided proof-of-concept evidence to deliver synergistic combination of bioactive lipid to achieve complete remission in AML.

Original submitted: 27 February 2013; Revised submitted: 25 June 2013

Definition of PKC-α, CDK6, and MET as therapeutic targets in triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a highly heterogeneous and recurrent subtype of breast cancer that lacks an effective targeted therapy. To identify candidate therapeutic targets, we profiled global gene expression in TNBC and breast tumor-initiating cells with a patient survival dataset. Eight TNBC-related kinases were found to be overexpressed in TNBC cells with stem-like properties. Among them, expression of PKC-α, MET, and CDK6 correlated with poorer survival outcomes. In cases coexpressing two of these three kinases, survival rates were lower than in cases where only one of these kinases was expressed. In functional tests, two-drug combinations targeting these three kinases inhibited TNBC cell proliferation and tumorigenic potential in a cooperative manner. A combination of PKC-α-MET inhibitors also attenuated tumor growth in a cooperative manner in vivo. Our findings define three kinases critical for TNBC growth and offer a preclinical rationale for their candidacy as effective therapeutic targets in treating TNBC.

Importance of sphingosine kinase (SphK) as a target in developing cancer therapeutics and recent developments in the synthesis of novel SphK inhibitors

Sphingosine kinase (SphK) is an oncogenic lipid kinase that regulates the sphingolipid metabolic pathway that has been shown to play a role in numerous hyperproliferative/inflammatory diseases. The SphK isoforms (SphK1 and SphK2) catalyze the conversion of the proapoptotic substrate d-erythrosphingosine to the promitogenic/migratory product sphingosine 1-phosphate (S1P). Accumulation of S1P has been linked to the development/progression of cancer and various other diseases including, but not limited to, asthma, inflammatory bowel disease, rheumatoid arthritis, and diabetic nephropathy. SphK therefore represents a potential new target for developing novel therapeutics for cancer and other diseases. This finding has stimulated the development and evaluation of numerous SphK inhibitors over the past decade or so. In this review, we highlight the recent advancement in the field of SphK inhibitors including SphK1 and SphK2 specific inhibitors. Both sphingolipid based and nolipidic small molecule inhibitors and their importance in treatment of cancer and other diseases are discussed.

The therapeutic potential of nanoscale sphingolipid technologies

Nanotechnologies, while small in size, widen the scope of drug delivery options for compounds with problematic pharmacokinetics, such as bioactive sphingolipids. We describe the development of historical sphingolipid nanotechnologies, such as nanoliposomes, and project future uses for a broad repertoire of nanoscale sphingolipid therapy formulations. In particular, we describe sphingo-nanotherapies for treatment of cancer, inflammatory disease, and cardiovascular disease. We conclude with a discussion of the challenges associated with regulatory approval, scale-up, and development of these nanotechnology therapies for clinical applications.

Efficacious hepatoma-targeted nanomedicine self-assembled from galactopeptide and doxorubicin driven by two-stage physical interactions

Polymers bearing pendant galactosyl group are attractive for targeted intracellular antitumor drug delivery to hepatoma cells (e.g. HepG2 and SMMC7721 cells) with asialoglycoprotein receptor (ASGP-R). Herein, a series of galactopeptides was synthesized through ring-opening polymerization of L-glutamate N-carboxyanhydride, deprotection of benzyl group and subsequent Huisgens cycloaddition "click" reaction with azide-modified galactosyl group. The copolypeptides were revealed to have excellent hemocompatibilities, and cell and tissue compatibilities, which rendered their potential for drug delivery applications. The hepatoma-targeted micellar nanoparticle (i.e. nanomedicine) was fabricated by cooperative self-assembly of galactopeptide and doxorubicin (DOX) induced by two-stage physical interactions. In vitro DOX release from nanomedicine was accelerated in the intracellular acidic condition. Through the recognition between galactose ligand and ASGP-R of HepG2 cells, the endocytosis of galactosylated nanomedicine was significantly promoted, which was demonstrated by confocal laser scanning microscopy and flow cytometry. Remarkably, the galactose-decorated nanomedicine retained much higher antitumor activity toward HepG2 cells in contrast to the nanomedicine without galactosyl group in vitro and in vivo. The above superiorities indicated that the galactosylated nanomedicine possessed great promising for hepatoma-targeted chemotherapy.

The multilayer nanoparticles formed by layer by layer approach for cancer-targeting therapy

The multilayer nanoparticles (NPs) were prepared for cancer-targeting therapy using the layer by layer approach. When drug-loaded Pluronic NPs were mixed with vesicles (liposomes) in the aqueous medium, Pluronic NPs were incorporated into the vesicles to form the vesicle NPs. Then, the multilayer NPs were formed by freeze-drying the vesicle NPs in a Pluronic aqueous solution. The morphology and size distribution of the multilayer NPs were observed using a TEM and a particle size analyzer. In order to apply the multilayer NPs as a delivery system for docetaxel (DTX), which is a model anticancer drug, the release pattern of the DTX was observed and the tumor growth was monitored by injecting the multilayer NPs into the tail veins of tumor (squamous cell carcinoma)-bearing mice. The cytotoxicity of free DTX (commercial DTX formulation (Taxotere®)) and the multilayer NPs was evaluated using MTT assay. We also evaluated the tumor targeting ability of the multilayer NPs using magnetic resonance imaging. The multilayer NPs showed excellent tumor targetability and antitumor efficacy in tumor-bearing mice, caused by the enhanced permeation and retention (EPR) effect. These results suggest that the multilayer NPs could be a potential drug delivery system for cancer-targeting therapy.