Combination treatment with arsenic trioxide and phytosphingosine enhances apoptotic cell death in arsenic trioxide-resistant cancer cells

A 'Chiron' approach to novel phytosphingosine mimetics based on a cascade [3,3]-sigmatropic rearrangement

Straightforward access to enantiomerically pure 3,4-diamino-3,4-dideoxyphytosphingosines, as novel analogues of natural d-ribo-phytosphingosine was accomplished, starting from two available chirons: dimethyl l-tartrate and d-isoascorbic acid. A sequential Overman rearrangement followed by late-stage introduction of the alkyl side chain moiety via olefin cross-metathesis is the cornerstone of this approach. The preliminary evaluation study of the synthesised sphingomimetics, based on their ability to inhibit a proliferation of human cancer cells, showed promising cytotoxicity against Jurkat and HeLa cells for (2R,3R,4S)-2,3,4-triaminooctadecan-1-ol trihydrochloride.

Identification of Therapeutic Targets for Medulloblastoma by Tissue-Specific Genome-Scale Metabolic Model

Medulloblastoma (MB), occurring in the cerebellum, is the most common childhood brain tumor. Because conventional methods decline life quality and endanger children with detrimental side effects, computer models are needed to imitate the characteristics of cancer cells and uncover effective therapeutic targets with minimum toxic effects on healthy cells. In this study, metabolic changes specific to MB were captured by the genome-scale metabolic brain model integrated with transcriptome data. To determine the roles of sphingolipid metabolism in proliferation and metastasis in the cancer cell, 79 reactions were incorporated into the MB model. The pathways employed by MB without a carbon source and the link between metastasis and the Warburg effect were examined in detail. To reveal therapeutic targets for MB, biomass-coupled reactions, the essential genes/gene products, and the antimetabolites, which might deplete the use of metabolites in cells by triggering competitive inhibition, were determined. As a result, interfering with the enzymes associated with fatty acid synthesis (FAs) and the mevalonate pathway in cholesterol synthesis, suppressing cardiolipin production, and tumor-supporting sphingolipid metabolites might be effective therapeutic approaches for MB. Moreover, decreasing the activity of succinate synthesis and GABA-catalyzing enzymes concurrently might be a promising strategy for metastatic MB.

The Mechanism of Interaction Between Gold Nanoparticles and Human Dermal Fibroblasts Based on Integrative Analysis of Transcriptomics and Metabolomics Data

The aim of this paper was to combine transcriptomics and metabolomics to analyze the mechanism of gold nanoparticles (GNPs) on human dermal fibroblasts (HDFs). First, 20-nm GNPs were prepared, and the differentially expressed genes in HDFs were subsequently screened by transcriptome sequencing technology after 4, 8, and 24 h of treatment with GNPs. By comparing the metabolic pathways in which the metabolites obtained in a previous study were involved, the pathways involving both genes and metabolites were filtered, and the differentially expressed genes and metabolites with upstream and downstream relationships were screened out. The gene–metabolite–metabolic pathway network was further constructed, and the functions of metabolic pathways, genes and metabolites in the important network were analyzed and experimentally verified. The results of transcriptome sequencing experiments showed that 1904, 1216 and 489 genes were differentially expressed in HDFs after 4, 8 and 24 h of treatment with GNPs, and these genes were involved in 270, 235 and 163 biological pathways, respectively. Through the comparison and analysis of the metabolic pathways affected by the metabolites, 7, 3 and 2 metabolic pathways with genes and metabolites exhibiting upstream and downstream relationships were identified. Through analysis of the gene–metabolite–metabolic pathway network, 4 important metabolic pathways, 9 genes and 7 metabolites were identified. Combined with the results of verification experiments on oxidative stress, apoptosis, the cell cycle, the cytoskeleton and cell adhesion, it was found that GNPs regulated the synthesis of downstream metabolites through upstream genes in important metabolic pathways. GNPs inhibited oxidative stress and thus did not induce significant apoptosis, but they exerted effects on several cellular functions, including arresting the cell cycle and affecting the cytoskeleton and cell adhesion.

Cerebrospinal fluid-based metabolomics to characterize different types of brain tumors

BACKGROUND

Brain tumors cause significant morbidity and mortality due to rapid progression and high recurrence risks. Reliable biomarkers to improve diagnosis thereof are desirable.

OBJECTIVE

This work aimed to identify panels of biomarkers for diagnostic purposes using cerebrospinal fluid (CSF)-based metabolomics.

METHODS

A cohort of 163 histologically-proven patients with brain disorders was involved. Comprehensive CSF-based metabolomics was achieved by liquid chromatography-quadrupole time-of-flight spectrometric (LC-Q/TOF-MS) and multivariate statistical analyses. The diagnostic performance of the metabolic markers was evaluated using receiver operating characteristic curves.

RESULTS

A total of 508 ion features were detected by the LC-Q/TOF-MS analysis, of which 27 metabolites were selected as diagnostic markers to discriminate different brain tumor types. The area under the curve (AUC) was 0.91 for lung adenocarcinoma patients with brain metastases (MBT) vs. lung adenocarcinoma patients without brain metastases (NMBT), 0.83 for primary central nervous system lymphoma (PCNSL) vs. secondary central nervous system involvement of systemic lymphoma (SCNSL), 0.77 for PCNSL vs. MBT, 0.87 for SCNSL vs. MBT, 0.86 for MBT vs. nontumorous brain diseases (NT), and 0.80 for PCNSL vs. NT. Perturbed metabolic pathways between the comparisons related mainly to amino acids and citrate metabolism.

CONCLUSIONS

CSF-based metabolomics to a large extent reliably identifies significant metabolic differences between different brain tumors and shows great potential for diagnosis of brain tumors.

Phytosphingosine exhibits an anti-epithelial-mesenchymal transition function by the inhibition of EGFR signaling in human breast cancer cells

The lack of effective anti-metastatic drugs for the eradication of breast cancer stem cells within tumors, which are often resistant to chemotherapy and radiotherapy, creates a major obstacle during metastatic breast cancer therapy. Although D-ribo-phytosphingosine (PHS) is well known to activate protein kinase (MAPK)-mediated apoptosis, its possible role towards the metastasis signaling mechanisms underlying the epithelial-mesenchymal transition (EMT) remains largely unknown. In this report, we investigate the anti-metastatic potential of the natural sphingolipid PHS for the targeting of breast cancer cells as well as breast stem-like cells in vitro. We showed that PHS led to suppression of migratory potential, spheroid formation, CD44^high/CD24^low subpopulation as well as stem cell- and EMT-associated protein expression in basal type highly malignant breast cancer cell lines. In addition, PHS-based inhibition of EMT was attributable to the downregulation of the EGFR/JAK1/STAT3 signaling axis, as validated by immunoprecipitation assays and breast tumorigenesis mice models. This study demonstrate that PHS can target metastatic tumors with dual specificity (EMT and cancer stem-like cells) and therefore may be serve as a promising candidate for breast cancer treatments.

SurvivinT34A increases the therapeutic efficacy of arsenic trioxide in mouse hepatocellular carcinoma models

Arsenic trioxide (ATO) has demonstrated clinical efficacy in acute promyelocytic leukemia (APL) and in vitro activity in various solid tumors. As2O3 as single agent exhibits poor efficacy for treatment of hepatocellular carcinoma (HCC) in phase II trial, suggesting that new modalities of treatment with enhanced therapeutic effect and alleviated toxicity are needed for application of As2O3 on patients with HCC. Survivin is the strongest inhibitor of apoptosis protein over-expressed in tumors, which has been proposed as an attractive target for new anticancer interventions. Disruption of survivin by the plasmid encoding the phosphorylation-defective mouse survivin threonine 34→alanine mutant (Msurvivin T34A plasmid) has proved a promising strategy for suppressing a variety of murine cancer. In the present study, we attempted to test Msurvivin T34A and arsenic trioxide (ATO) on a cell line and mice bearing subcutaneous tumors, with regard to their effects and mechanisms. We observed that the co-treatment with surivinT34A and ATO significantly enhanced the antitumor activity by induction of apoptosis in Hepa1-6 tumor cells in vitro, compared with control groups. The synergistic apoptosis-inducing effect of combination of these two drugs resulted in elevation of reactive oxygen species (ROS) level which could be antagonized by the antioxidant N-acetyl-l-cysteine. The combination treatment induced ROS-dependent collapse of the mitochondrial membrane potential. Moreover, the tumor growth in vivo was also remarkably inhibited by combination of surivinT34A and ATO when compared with control groups. Our findings demonstrate that the combination of surivinT34A and ATO exerted synergistic antitumor effects, providing a new perspective for clinical treatment of HCC.

Phytosphingosine promotes megakaryocytic differentiation of myeloid leukemia cells

We report that phytosphingosine, a sphingolipid found in many organisms and implicated in cellular signaling, promotes megakaryocytic differentiation of myeloid leukemia cells. Specifically, phytosphingosine induced several hallmark changes associated with megakaryopoiesis from K562 and HEL cells including cell cycle arrest, cell size increase and polyploidization. We also confirmed that cell type specific markers of megakaryocytes, CD41a and CD42b are induced by phytosphingosine. Phospholipids with highly similar structures were unable to induce similar changes, indicating that the activity of phytosphingosine is highly specific. Although phytosphingosine is known to activate p38 mitogen-activated protein kinase (MAPK)-mediated apoptosis, the signaling mechanisms involved in megakaryopoiesis appear to be distinct. In sum, we present another model for dissecting molecular details of megakaryocytic differentiation which in large part remains obscure. [BMB Reports 2015; 48(12): 691-695]

Arsenic trioxide and triptolide synergistically induce apoptosis in the SKM‑1 human myelodysplastic syndrome cell line

Although certain combination therapies comprising arsenic trioxide (As₂O₃) with other agents exist for the treatment of several types of human cancer, few As₂O₃ combination therapies are clinically effective for myelodysplastic syndromes (MDS). Triptolide (TL) may be an effective therapeutic agent for the treatment of MDS. However, to date, there is no combination therapy for MDS with As₂O₃ and TL. Therefore, the aim of the present study was to investigate this combination therapy on the apoptosis of MDS SKM-1 cells. The MDS SKM-1 cells were treated with As₂O₃, TL or the two in combination at various concentrations, or were mock-treated. Cell viability, cell apoptosis, levels of reactive oxygen species (ROS) and the expression of the cell apoptosis-associated genes, B cell lymphoma-2 (Bcl-2), Bcl-2-associated X protein (Bax) and caspase-3, were determined using an MTT assay, flow cytometric analysis of annexin V-fluorescein isothiocyanate/propidium iodide double-stained cells, flow cytometic analysis of intracellular 2′,7′-dichlorodihydrofluorescein diacetate fluorescence and reverse transcription-quantitative polymerase chain reaction analysis, respectively. Combination index (CI) analysis was performed to determine whether effects were synergistic (CI<1). The combination treatment was found to synergistically inhibit MDS SKM-1 cell growth, induce cell apoptosis, increase ROS levels, upregulate the expression levels of Bax and caspase-3, and downregulate the mRNA expression of Bcl-2. In conclusion, the combination treatment of As₂O₃ and TL synergistically induced apoptosis in the MDS SKM-1 cells.

Arsenic trioxide synergistically potentiates the cytotoxic effect of fludarabine in chronic lymphocytic leukemia cells by further inactivating the Akt and ERK signaling pathways

CLL remains an incurable disease, making it crucial to continue searching for new therapies efficient in all CLL cases. We have studied the effect of combining arsenic trioxide (ATO) with fludarabine, a frontline drug in CLL. We have found a synergistic interaction between 1 μM ATO and 5 μM fludarabine that significantly enhanced the cytotoxic effect of the individual drugs. Importantly, ATO sensitized fludarabine-resistant cells to the action of this drug. The mechanism behind this effect included the downregulation of phospho-Akt, phospho-ERK, and the Mcl-1/Bim and Bcl-2/Bax ratios. The combination of ATO and fludarabine partially overcame the survival effect induced by co-culturing CLL cells with stromal cells. Therefore, low concentrations of ATO combined with fludarabine may be an efficient therapeutic strategy in CLL patients.

Metformin sensitizes hepatocellular carcinoma to arsenic trioxide-induced apoptosis by downregulating Bcl2 expression

Hepatocellular carcinoma (HCC) is a highly malignant tumor that can evolve rapidly to acquire resistance to conventional chemotherapies. Arsenic trioxide (ATO) is a traditional Asian medicine, and a phase II study has shown that treatment with ATO alone was not effective against HCC. Bcl2 is an antiapoptotic protein that regulates chemotherapy in HCC. Metformin is reported to decrease Bcl2 expression, and the purpose of this study was to verify whether metformin could potentiate the anti-HCC efficacy of ATO in vitro. In the present study, we used metformin and ATO alone or in combination and then tested proliferation, apoptosis, and Bcl2 level of HCC cells. The results showed that metformin enhanced both the proliferation-inhibiting and apoptosis-inducing effects of ATO on HCC cell lines HepG2 and BEL7402. Furthermore, this activity proceeded via a mechanism involving metformin-induced downregulation of Bcl2. A combination of ATO and metformin is therefore a potentially promising approach for HCC therapy.

L-cysteine as a regulator for arsenic-mediated cancer-promoting and anti-cancer effects

Previous studies have shown that activities of tyrosine kinases and secretion of the active form of matrix metalloproteinase-2 (MMP-2) are correlated with promotion of tumor growth, while apoptotic cell death in cancer cells is correlated with anti-cancer effects. Although arsenic has been reported to have both cancer-promoting and anti-cancer effects, the mechanisms of the arsenic-mediated bidirectional effects remain unknown. We examined the effects of arsenic on both proto-oncogene c-RET-transfected NIH3T3 cells with benign characters and oncogenic RET-MEN2A-transfected NIH3T3 cells with malignant characters. Arsenic promoted not only c-RET tyrosine kinase activity but also genetically activated RET-MEN2A kinase activity with promotion of dimer formation of RET proteins. Arsenic also increased secretion of the active form of MMP-2 in both RET-MEN2A-transfectants and c-RET-transfectants. On the other hand, arsenic promoted poly-(ADP-ribose) polymerase (PARP) degradation and cell death in both malignant and non-malignant cells. Interestingly, l-cysteine inhibited the arsenic-mediated tumor-promoting effects (activation of kinases and MMP-2 secretion) but not arsenic-mediated anti-cancer effects (PARP degradation and cell death). Our results suggest redox-linked regulation of arsenic-mediated activities of kinases and MMP-2 secretion but not arsenic-mediated cell death. Our results also suggest that l-cysteine is an ideal supplement that inhibits arsenic-mediated tumor-promoting effects without affecting arsenic-mediated anti-cancer effects.

Arsenic trioxide inhibits cholangiocarcinoma cell growth and induces apoptosis

Arsenic trioxide (As(2)O(3)), an ingredient in many traditional Chinese medicines, has drawn broad attention due to its therapeutic effects on a variety of cancers, including some solid tumors. However, the effects of As(2)O(3) on cholangiocarcinoma have not been reported. In the present study, we demonstrate for the first time that clinically obtainable concentrations of As(2)O(3) inhibit cell growth and induce apoptosis in human cholangiocarcinoma SK-ChA-1 cells. As(2)O(3)-induced apoptosis was partially inhibited by caspase inhibitor and accompanied by changes in the expression of Bcl-2 family proteins, decrease of mitochondrial membrane potential (MMP), release of cytochrome C from mitochondria, activation of caspase-3, caspase-9, and cleavage of poly (ADP-ribose) polymerase (PARP). Thus As(2)O(3) induces apoptosis in SK-ChA-1 cells via mitochondria-mediated, caspases-dependent pathways. As(2)O(3) inhibition of Akt phosphorylation may contribute to As(2)O(3)-mediated cholangiocarcinoma cell growth inhibition and apoptosis induction.

The natural marine anhydrophytosphingosine, Jaspine B, induces apoptosis in melanoma cells by interfering with ceramide metabolism

Marine environment has frequently afforded a variety of biologically active compounds with strong anticancer and cytotoxic properties. In the present study, the mechanism of action of Jaspine B, an anhydrophytosphingosine derivative isolated from the marine sponge Jaspis sp., was investigated. Jaspine B was able to dose- and time-dependently decrease the viability of murine B16 and human SK-Mel28 melanoma cells. On these cells, Jaspine B treatment triggered cell death by typical apoptosis as illustrated by phosphatidylserine externalization, the release of cytochrome c and caspase processing. These effects were associated with increased intracellular ceramide levels owing to perturbed ceramide metabolism. Indeed, Jaspine B exposure strongly inhibited the activity of sphingomyelin synthase (SMS), an enzyme that converts de novo ceramide into the membrane lipid sphingomyelin. Moreover, whereas Jaspine B-induced cell death was enhanced in SMS1-depleted cells, it was strongly inhibited in cells that stably overexpress human SMS1. Finally, the cytotoxic effects of Jaspine B truncated analogs were also shown to be dependent on SMS activity. Altogether, Jaspine B is able to kill melanoma cells by acting on SMS activity and consequently on ceramide formation, and may represent a new class of cytotoxic compounds with potential applications in anticancer melanoma therapy.