Ceramide promotes the death of human cervical tumor cells in the absence of biochemical and morphological markers of apoptosis

In Vitro, In Vivo and In Silico Assessment of the Antimicrobial and Immunomodulatory Effects of a Water Buffalo Cathelicidin (WBCATH) in Experimental Pulmonary Tuberculosis

Tuberculosis (TB) is considered the oldest pandemic in human history. The emergence of multidrug-resistant (MDR) strains is currently considered a serious global health problem. As components of the innate immune response, antimicrobial peptides (AMPs) such as cathelicidins have been proposed to have efficacious antimicrobial activity against Mycobacterium tuberculosis (Mtb). In this work, we assessed a cathelicidin from water buffalo, Bubalus bubalis, (WBCATH), determining in vitro its antitubercular activity (MIC), cytotoxicity and the peptide effect on bacillary loads and cytokines production in infected alveolar macrophages. Our results showed that WBCATH has microbicidal activity against drug-sensitive and MDR Mtb, induces structural mycobacterial damage demonstrated by electron microscopy, improves Mtb killing and induces the production of protective cytokines by murine macrophages. Furthermore, in vivo WBCATH showed decreased bacterial loads in a model of progressive pulmonary TB in BALB/c mice infected with drug-sensitive or MDR mycobacteria. In addition, a synergistic therapeutic effect was observed when first-line antibiotics were administered with WBCATH. These results were supported by computational modeling of the potential effects of WBCATH on the cellular membrane of Mtb. Thus, this water buffalo-derived cathelicidin could be a promising adjuvant therapy for current anti-TB drugs by enhancing a protective immune response and potentially reducing antibiotic treatment duration.

Isolation of Ceramides from Tagetes patula L. Yellow Flowers and Nematicidal Activity of the Fractions and Pure Compounds against Cyst Nematode, Heterodera zeae

Investigation of yellow flower extract of Tagetes patula L. led to the identification of an aggregate of five phytoceramides. Among them, (2R)-2-hydroxy-N-[(2S,3S,4R,8E)-1,3,4-trihydroxyicos-8-en-2-yl]icosanamide, (2R)-2-hydroxy-N-[(2S,3S,4R,8E)-1,3,4-trihydroxyicos-8-en-2-yl]heneicosanamide, (2R)-2-hydroxy-N-[(2S,3S,4R,8E)-1,3,4-trihydroxyicos-8-en-2-yl]docosanamide, and (2R)-2-hydroxy-N-[(2S,3S,4R,8E)-1,3,4-trihydroxyicos-8-en-2-yl]tricosanamide were identified as new compounds and termed as tagetceramides, whereas (2R)-2-hydroxy-N-[(2S,3S,4R,8E)-1,3,4-trihydroxyicos-8-en-2-yl]tetracosanamide was a known ceramide. A steroid (β-sitosterol glucoside) was also isolated from the subsequent fraction. The structures of these compounds were determined on the basis of spectroscopic analyses, as well as chemical method. Several other compounds were also identified by GC/MS analysis. The fractions and some commercial products, a ceramide HFA, β-sitosterol, and stigmasterol were evaluated against an economically important cyst nematode, Heterodera zeae. Ceramide HFA showed 100 % mortality, whereas, β-sitosterol and stigmasterol were 40-50 % active, at 1 % concentration after 24 h of exposure time, while β-sitosterol glucoside revealed no activity against the nematode.

Multifunctional nanoemulsions for intraductal delivery as a new platform for local treatment of breast cancer

Considering that breast cancer usually begins in the lining of the ducts, local drug administration into the ducts could target cancers and pre-tumor lesions locally while reducing systemic adverse effects. In this study, a cationic bioadhesive nanoemulsion was developed for intraductal administration of C6 ceramide, a sphingolipid that mediates apoptotic and non-apoptotic cell death. Bioadhesive properties were obtained by surface modification with chitosan. The optimized nanoemulsion displayed size of 46.3 nm and positive charge, properties that were not affected by ceramide encapsulation (0.4%, w/w). C6 ceramide concentration necessary to reduce MCF-7 cells viability to 50% (EC₅₀) decreased by 4.5-fold with its nanoencapsulation compared to its solution; a further decrease (2.6-fold) was observed when tributyrin (a pro-drug of butyric acid) was part of the oil phase of the nanocarrier, a phenomenon attributed to synergism. The unloaded nanocarrier was considered safe, as indicated by a score <0.1 in HET-CAM models, by the high survival rates of Galleria mellonella larvae exposed to concentrations ≤500 mg/mL, and absence of histological changes when intraductally administered in rats. Intraductal administration of the nanoemulsion prolonged drug localization for more than 120 h in the mammary tissue compared to its solution. These results support the advantage of the optimized nanoemulsion to enable mammary tissue localization of C6 ceramide.

Cytotoxic, antioxidative, genotoxic and antigenotoxic effects of Horchata, beverage of South Ecuador

BACKGROUND

"Horchata" is an herbal mixture infusion consumed in Southern Ecuador; 66% of its plants are anti-inflammatory medicinal plant, and 51% are analgesics. Anti-inflammatory substances can prevent carcinogenesis mediated by cytotoxic effects and can prevent DNA damage. The aim of this study was to evaluate the cytotoxicity and apoptotic/antigenotoxic effects of horchata as well as its mechanism.

METHODS

Nine different varieties of horchata were prepared in the traditional way and then freeze-dried. Phytochemical screening tested for the presence of secondary metabolites using standard procedures and antioxidant activities. The cytotoxic activity was evaluated on cerebral astrocytoma (D-384), prostate cancer (PC-3), breast cancer (MCF-7), colon cancer (RKO), lung cancer (A-549), immortalized Chinese hamster ovary cells (CHO-K1), and human peripheral blood lymphocytes via a MTS assay. The pro-apoptotic effects were evaluated with Anexin V/Propidium Iodide and western blot of Bax, Bcl-2, TP53, and TP73. Induction and reduction of ROS were assessed by fluorimetry. Genotoxic and antigenotoxic effects were evaluated with a comet assay and micronuclei on binucleated cells.

RESULTS

Five of nine horchatas had cytotoxic effects against D-384 while not affecting normal cells. These horchatas induce cell death by apoptosis modulated by p53/p73. In CHO-K1 cells, the horchatas decrease the damage induced by hydrogen peroxide and Mitomycin C measured in the comet and micronucleus assay respectively.

CONCLUSIONS

The IC50 range of effective horchatas in D-384 was 41 to 122 μg·mL-1. This effect may be related to its use in traditional medicine (brain tonic). On the other hand, immortalized Chinese hamster ovary cells (CHO-K1) and lymphocytes did not show a cytotoxic effect. The most potent horchata induced apoptosis via a p53/p73-mediated mechanism. The horchatas present antigenotoxic properties, which may be related to the antioxidant capacity. Future studies on horchata components are necessary to understand the interactions and beneficial properties.

Cytotoxic activity and quantitative structure activity relationships of arylpropyl sulfonamides

B13 is a ceramide analogue and apoptosis inducer with potent cytotoxic activity. A series of arylpropyl sulfonamide analogues of B13 were evaluated for their cytotoxicity using MTT assays in prostate cancer PC-3 and leukemia HL-60 cell lines. Some compounds (4, 9, 13, 14, 15, and 20) showed stronger activities than B13 in both tumor cell lines, and compound (15) gave the most potent activity with IC₅₀ values of 29.2 and 20.7 µM, for PC-3and HL-60 cells, respectively. Three-dimensional quantitative structure-activity relationship (3D-QSAR) analysis was performed to build highly reliable and predictive CoMSIA models with cross-validated q² values of 0.816 and 0.702, respectively. Our results suggest that long alkyl chains and a 1R, 2R configuration of the propyl group are important for the cytotoxic activities of arylpropyl sulfonamides. Moreover, the introduction of small hydrophobic groups in the phenyl ring and sulfonamide group could increase biological activity.

Dehydroepiandrosterone inhibits the proliferation and induces the death of HPV-positive and HPV-negative cervical cancer cells through an androgen- and estrogen-receptor independent mechanism

Dehydroepiandrosterone (DHEA) has a protective role against epithelial-derived carcinomas; however, the mechanisms remain unknown. We determined the effect of DHEA on cell proliferation, the cell cycle and cell death in three cell lines derived from human uterine cervical cancers infected or not with human papilloma virus (HPV). We also determined whether DHEA effects are mediated by estrogen and androgen receptors. Proliferation of C33A (HPV-negative), CASKI (HPV16-positive) and HeLa (HPV18-positive) cells was evaluated by violet crystal staining and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) reduction. Flow cytometry was used to evaluate the phases of the cell cycle, and cell death was detected using a commercially available carboxyfluorescein apoptosis detection kit that determines caspase activation. DNA fragmentation was determined using the terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay. Flutamide and ICI 182,780 were used to inhibit androgen and estrogen receptors, respectively, and letrozol was used to inhibit the conversion of DHEA to estradiol. Our results show that DHEA inhibited cell proliferation in a dose-dependent manner in the three cell lines; the DHEA IC(50) doses were 50, 60 and 70 mum for C33A, CASKI and HeLa cells, respectively. The antiproliferative effect was not abrogated by inhibitors of androgen and estrogen receptors or by an inhibitor of the conversion of testosterone to estradiol, and this effect was associated with an increase in necrotic cell death in HPV-negative cells and apoptosis in HPV-positive cells. These results suggest that DHEA strongly inhibits the proliferation of cervical cancer cells, but its effect is not mediated by androgen or estrogen receptor pathways. DHEA could therefore be used as an alternative in the treatment of cervical cancer.

N-(4-Hydroxyphenyl)retinamide increases dihydroceramide and synergizes with dimethylsphingosine to enhance cancer cell killing

Fenretinide [N-(4-hydroxyphenyl)retinamide (4-HPR)] is cytotoxic in many cancer cell types. Studies have shown that elevation of ceramide species plays a role in 4-HPR cytotoxicity. To determine 4-HPR activity in a multidrug-resistant cancer cell line as well as to study ceramide metabolism, MCF-7/AdrR cells (redesignated NCI/ADR-RES) were treated with 4-HPR and sphingolipids were analyzed. TLC analysis of cells radiolabeled with [3H]palmitic acid showed that 4-HPR elicited a dose-responsive increase in radioactivity migrating in the ceramide region of the chromatogram and a decrease in cell viability. Results from liquid chromatography/electrospray tandem mass spectrometry revealed large elevations in dihydroceramides (N-acylsphinganines), but not desaturated ceramides, and large increases in complex dihydrosphingolipids (dihydrosphingomyelins, monohexosyldihydroceramides), sphinganine, and sphinganine 1-phosphate. To test the hypothesis that elevation of sphinganine participates in the cytotoxicity of 4-HPR, cells were treated with the sphingosine kinase inhibitor d-erythro-N,N-dimethylsphingosine (DMS), with and without 4-HPR. After 24 h, the 4-HPR/DMS combination caused a 9-fold increase in sphinganine that was sustained through +48 hours, decreased sphinganine 1-phosphate, and increased cytotoxicity. Increased dihydrosphingolipids and sphinganine were also found in HL-60 leukemia cells and HT-29 colon cancer cells treated with 4-HPR. The 4-HPR/DMS combination elicited increased apoptosis in all three cell lines. We propose that a mechanism of 4-HPR-induced cytotoxicity involves increases in dihydrosphingolipids, and that the synergy between 4-HPR and DMS is associated with large increases in cellular sphinganine. These studies suggest that enhanced clinical efficacy of 4-HPR may be realized through regimens containing agents that modulate sphingoid base metabolism.

Mouse mammary tumors display Stat3 activation dependent on leukemia inhibitory factor signaling

Introduction

It has been demonstrated that leukemia inhibitory factor (LIF) induces epithelium apoptosis through Stat3 activation during mouse mammary gland involution. In contrast, it has been shown that this transcription factor is commonly activated in breast cancer cells, although what causes this effect remains unknown. Here we have tested the hypothesis that locally produced LIF can be responsible for Stat3 activation in mouse mammary tumors.

Methods

The studies were performed in different tumorigenic and non-tumorigenic mammary cells. The expression of LIF and LIF receptor was tested by RT-PCR analysis. In tumors, LIF and Stat3 proteins were analyzed by immunohistochemistry, whereas Stat3 and extracellular signal-regulated kinase (ERK)1/2 expression and phosphorylation were studied by Western blot analysis. A LIF-specific blocking antibody was used to determine whether this cytokine was responsible for Stat3 phosphorylation induced by conditioned medium. Specific pharmacological inhibitors (PD98059 and Stat3ip) that affect ERK1/2 and Stat3 activation were used to study their involvement in LIF-induced effects. To analyze cell survival, assays with crystal violet were performed.

Results

High levels of LIF expression and activated Stat3 were found in mammary tumors growing in vivo and in their primary cultures. We found a single mouse mammary tumor cell line, LM3, that showed low levels of activated Stat3. Incidentally, these cells also showed very little expression of LIF receptor. This suggested that autocrine/paracrine LIF would be responsible for Stat3 activation in mouse mammary tumors. This hypothesis was confirmed by the ability of conditioned medium of mammary tumor primary cultures to induce Stat3 phosphorylation, activity that was prevented by pretreatment with LIF-blocking antibody. Besides, we found that LIF increased tumor cell viability. Interestingly, blocking Stat3 activation enhanced this effect in mammary tumor cells.

Conclusion

LIF is overexpressed in mouse mammary tumors, where it acts as the main Stat3 activator. Interestingly, the positive LIF effect on tumor cell viability is not dependent on Stat3 activation, which inhibits tumor cell survival as it does in normal mammary epithelium.

Novel analogs of D-e-MAPP and B13. Part 1: synthesis and evaluation as potential anticancer agents

A series of novel isosteric analogs of the ceramidase inhibitors, (1S,2R)-N-myristoylamino-phenylpropanol-1 (d-e-MAPP) and (1R,2R)-N-myristoylamino-4'-nitro-phenylpropandiol-1,3 (B13), with modified targeting and physicochemical properties were designed, synthesized, and evaluated as potential anticancer agents. When MCF7 cells were treated with the analogs, results indicated that the new analogs were of equal or greater potency compared to the parent compounds. Their activity was predominantly defined by the nature of the modification of the N-acyl hydrophobic interfaces: N-acyl analogs (class A), urea analogs (class B), N-alkyl analogs (class C, lysosomotropic agents), and omega-cationic-N-acyl analogs (class D, mitochondriotropic agents). The most potent compounds belonged to either class D, the aromatic ceramidoids, or to class C, the aromatic N-alkylaminoalcohols. Representative analogs selected from this study were also evaluated by the National Cancer Institute In Vitro Anticancer Drug Discovery Screen. Again, results showed a similar class-dependent activity. In general, the active analogs were non-selectively broad spectrum and had promising activity against all cancer cell lines. However, some active analogs of the d-e-MAPP family were selective against different types of cancer. Compounds LCL85, LCL120, LCL385, LCL284, and LCL204 were identified to be promising lead compounds for therapeutic development.

Novel analogs of D-e-MAPP and B13. Part 2: signature effects on bioactive sphingolipids

Novel isosteric analogs of the ceramidase inhibitors (1S,2R)-N-myristoylamino-phenylpropanol-1 (d-e-MAPP) and (1R,2R)-N-myristoylamino-4'-nitro-phenylpropandiol-1,3 (B13) with modified targeting and physicochemical properties were developed and evaluated for their effects on endogenous bioactive sphingolipids: ceramide, sphingosine, and sphingosine 1-phosphate (Cer, Sph, and S1P) in MCF7 cells as determined by high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS). Time- and dose-response studies on the effects of these compounds on Cer species and Sph levels, combined with structure-activity relationship (SAR) data, revealed 4 distinct classes of analogs which were predominantly defined by modifications of the N-acyl-hydrophobic interfaces: N-acyl-analogs (class A), urea-analogs (class B), N-alkyl-analogs (class C), and omega-cationic-N-acyl analogs (class D). Signature patterns recognized for two of the classes correspond to the cellular compartment of action of the new analogs, with class D acting as mitochondriotropic agents and class C compounds acting as lysosomotropic agents. The neutral agents, classes A and B, do not have this compartmental preference. Moreover, we observed a close correlation between the selective increase of C(16)-, C(14)-, and C(18)-Cers and inhibitory effects on MCF7 cell growth. The results are discussed in the context of compartmentally targeted regulators of Sph, Cer species, and S1P in cancer cell death, emphasizing the role of C(16)-Cer. These novel analogs should be useful in cell-based studies as specific regulators of Cer-Sph-S1P inter-metabolism, in vitro enzymatic studies, and for therapeutic development.

Ceramide induces early and late apoptosis in human papilloma virus+ cervical cancer cells by inhibiting reactive oxygen species decay, diminishing the intracellular concentration of glutathione and increasing nuclear factor-kappaB translocation

Ceramide is regarded as an important cellular signal for the induction of cell death. We have previously shown that ceramide induces the death of cervical tumor cells without biochemical and morphological markers of apoptosis. The mechanisms by which ceramide induces cell death are not understood, therefore we evaluated the effect of C6-ceramide, a synthetic cell-permeable analog of endogenous ceramides, in signaling pathways involved in the oxidative stress of three cervical human papilloma virus cancer cell lines. Reactive oxygen species production was determined by fluorescent 2,7-dichlorofluorescein, nitrite concentration by the Griess reaction (as an indirect measure of nitric oxide production), mitochondrial membrane potential by staining with Rh123, reduced-glutathione concentration by high-pressure liquid chromatography, nuclear factor-kappaB translocation by electrophoretic mobility shift assay, inhibitory protein of nuclear factor-kappaB expression by Western blot and cell death by a poly-caspases fluorochrome-labeled inhibitors of caspases apoptosis assay. C6-ceramide induced early and late apoptosis, which was associated with an increase in reactive oxygen species and nitric oxide production, a loss in mitochondrial membrane potential, an increase in nuclear factor-kappaB translocation, and a decrease in reduced glutathione concentration. C6-ceramide did not modify the expression of inhibitory protein of nuclear factor-kappaB and its antiproliferative effect was not abrogated by Bay 11-7082, an inhibitory protein of nuclear factor-kappaB kinase inhibitor. Our results suggest that oxidative stress might participate in the ceramide-induced damage to human papilloma virus cervical cancer cells.

Tailoring structure-function and targeting properties of ceramides by site-specific cationization

In the course of our studies on compartment-specific lipid-mediated cell regulation, we identified an intimate connection between ceramides (Cers) and the mitochondria-dependent death-signaling pathways. Here, we report on a new class of cationic Cer mimics, dubbed ceramidoids, designed to act as organelle-targeted sphingolipids (SPLs), based on conjugates of Cer and dihydroceramide (dhCer) with pyridinium salts (CCPS and dhCCPS, respectively). Ceramidoids having the pyridinium salt unit (PSU) placed internally (alpha and gamma- CCPS) or as a tether (omega-CCPS) in the N-acyl moiety were prepared by N-acylation of sphingoid bases with different omega-bromo acids or pyridine carboxylic acid chlorides following capping with respective pyridines or alkyl bromides. Consistent with their design, these analogs, showed a significantly improved solubility in water, well-resolved NMR spectra in D(2)O, broadly modified hydrophobicity, fast cellular uptake, and higher anticancer activities in cells in comparison to uncharged counterparts. Structure-activity relationship (SAR) studies in MCF-7 breast carcinoma cells revealed that the location of the PSU and its overall chain length affected markedly the cytotoxic effects of these ceramidoids. All omega-CCPSs were more potent (IC(50/48 h): 0.6-8.0 microM) than their alpha/gamma-CCPS (IC(50/48 h): 8-20 microM) or D-erythro-C6-Cer (IC(50/48 h): 15 microM) analogs. omega-DhCCPSs were also moderately potent (IC(50/48 h): 2.5-12.5 microM). Long-chain omega-dhCCPSs were rapidly and efficiently oxidized in cells to the corresponding omega-CCPSs, as established by LC-MS analysis. CCPS analogs also induced acute changes in the levels and composition of endogenous Cers (upregulation of C16-, C14-, and C18-Cers, and downregulation of C24:0- and C24:1-Cers). These novel ceramidoids illustrate the feasibility of compartment-targeted lipids, and they should be useful in cell-based studies as well as potential novel therapeutics.

Sphingolipids as modulators of cancer cell death: potential therapeutic targets

Through modifications in the fine membrane structure, cell-cell or cell-matrix interactions, and/or modulation of intracellular signaling pathways, sphingolipids can affect the tumorigenic potential of numerous cell types. Whereas ceramide and its metabolites have been described as regulators of cell growth and apoptosis, these lipids as well as other sphingolipid molecules can modulate the ability of malignant cells to grow and resist anticancer treatments, and their susceptibility to non-apoptotic cell deaths. This review summarizes our current knowledge on the properties of sphingolipids in the regulation of cancer cell death and tumor development. It also provides an update on the potential perspectives of manipulating sphingolipid metabolism and using sphingolipid analogues in anticancer therapy.

Caspase-dependent and -independent cell death of Jurkat human leukemia cells induced by novel synthetic ceramide analogs

Ceramide metabolism has emerged as a potential target for anticancer therapy. Here, the potential usefulness of two novel synthetic ceramide analogs as anti-leukemic drugs was investigated. Compounds AD2646 and AD2687 were able to dose-and time-dependently decrease the viability of Jurkat leukemic cells. This was accompanied by an accumulation of endogenous ceramide owing to perturbed ceramide metabolism. Cytotoxicity involved caspase activation but also necrotic-like features, as evidenced by phosphatidylserine externalization, membrane permeability, hypodiploidy, caspase processing and only partial protection from cell death by a pan-caspase inhibitor. Ceramide analogs also induced cell death in Jurkat mutants that are deficient in cell death signaling proteins, including FADD, caspase-8 and 10, and RIP. While overexpression of Bcl-xL did not suppress ceramide accumulation, it conferred robust protection from caspase activation and cell death. Altogether, these novel ceramide analogs are able to kill leukemic cells through distinct pathways implicating caspase activation and mitochondrial events, and represent a new group of bioactive molecules with potential applications in anticancer therapy.

Role of biologically active sphingolipids in tumor growth

This review highlights the literature on the effects of biologically active sphingolipids (sphingosine, ceramide, sphingomyelin, glucosylceramide, gangliosides GM1, GM2, GM3, GD3, etc.) on proliferation, apoptosis, metastases, and invasiveness of tumor cells and the putative role of sphingolipids in chemotherapy of malignant tumors.

Gene Identification by cDNA Arrays in HPV-Positive Cervical Cancer

BACKGROUND

One of the most frequent malignancies in women worldwide is carcinoma of the uterine cervix. High-risk human papillomavirus (HPV) infection is considered the most important etiological factor of uterine cervical cancer. Our aim was to identify novel cellular genes that could potentially act as predictive molecular markers for human cervical cancer by means of cDNA arrays.

METHODS

We used cDNA arrays to examine the expression profiles of six cell lines derived from human cervical cancer, three HPV+ tumor samples and three normal (HPV-) epithelium tissues. Data normalization was performed and the top overexpressed genes were obtained. Hierarchical cluster was performed and, to validate some of the differentially expressed genes between normal and carcinogenic samples, semi-quantitative RT-PCR, in situ hybridization and immunohistochemistry were performed in tissue samples.

RESULTS

Four genes were demonstrated to be consistently overexpressed in invasive cervical cancer biopsies; three novel genes not previously related to cervical cancer: MMP10, Lamc2 and Claudin 1. Moreover, overexpression of IL6 and VEGF was corroborated.

CONCLUSIONS

The identification of characteristic molecular changes in cervical cells by carcinogenesis and HPV infection can lead to a better understanding of cervical cancer. cDNA arrays are beginning to provide new possible molecular markers for prognosis and diagnosis. This technology could eventually help to elucidate the biological differences of the particular mechanisms associated with each different HPV-type infection and those with a poor prognosis.

NF-κB activation but not PI3K/Akt is required for dexamethasone dependent protection against TNF-α cytotoxicity in L929 cells

Tumor necrosis factor alpha (TNF-alpha) is one of the best-described cell death promoters. In murine L929 fibroblasts, dexamethasone inhibits TNF-alpha-induced cytotoxicity. Since phosphatidyl inositol 3 kinase (PI3K) and nuclear factor kappa B (NF-kappaB) proteins regulate several survival pathways, we evaluated their participation in dexamethasone protection against TNF-alpha cell death. We interfered with these pathways by overexpressing a negative dominant mutant of PI3K or a non-degradable mutant of inhibitor of NF-kappaB alpha (IkappaBalpha) (the cytoplasmic inhibitor of NF-kappaB) in L929 cells. The mutant IkappaB, but not the mutant PI3K, abrogated dexamethasone-mediated protection. The loss of dexamethasone protection was associated with a diminished accumulation in XIAP and c-IAP proteins.

A fungal tRNA of Aspergillus niger induces IFN-beta synthesis in HEp-2 cells

In this work, we evaluated the capacity of a fungal transfer RNA (F-tRNA) from Aspergillus niger to protect HEp-2 cells against a viral infection, and as an inducer of IFN-beta synthesis. HEp-2 cells previously incubated with F-tRNA, polyI:polyC, or IFN-alpha, at different concentrations for 24 h were infected with 200 pfu of adenovirus type 6 (AdV-6); after 5 days, we determined cellular viability, cytopathic effect of the virus, optimal concentration necessary to inhibit the cytopathic effect, and IFN-beta expression by RT-PCR. Results showed that HEp-2 cells treated with F-tRNA were less susceptible to the cytopathic effect of AdV-6 infection than those incubated with polyI:polyC (p < 0.05). On the other hand, F-tRNA- treated HEp-2 cells expressed IFN-beta mRNA, whereas monolayers incubated with polyI:polyC or IFN-alpha did not. Our results suggest that F-tRNA protected HEp-2 cells against AdV-6 infection, due to its capacity to induce IFN-beta synthesis.

Synergistic antiproliferative and apoptotic effects induced by mixed epidermal growth factor receptor inhibitor ZD1839 and nitric oxide donor in human prostatic cancer cell lines

BACKGROUND

The specific inhibitor of epidermal growth factor receptor (EGFR) tyrosine kinase, ZD1839 induces potent antitumoral effects on several advanced cancer types. The present study was undertaken to determine whether the combination of ZD1839 with an agent donating nitric oxide (NO(*)), sodium nitroprusside (SNP) results in a synergy of anticarcinogenic responses on metastatic prostate cancer (PC) cells.

METHODS

The antiproliferative and apoptotic/necrotic effects of ZD1839 and SNP alone or in combination were estimated on EGF- and serum-stimulated LNCaP, DU145, and PC3 cells by MTT growth tests, trypan blue dye exclusion method, and flow cytometric analyses. Moreover, the cellular ceramide levels were evaluated by the diacylglycerol kinase enzymatic method and the amounts of cytosolic cytochrome c by ELISA assays.

RESULTS

ZD1839 and SNP alone or in combination at lower concentrations induced an inhibition of EGF- and serum-stimulated growth of LNCaP, DU145, and PC3 concomitant with an arrest in the G1 phase of cellular cycle. Interestingly, the mixed ZD1839 and SNP also caused a more substantial apoptotic/necrotic death of these PC cells as compared to drugs alone. Moreover, we have observed that an inhibition of acidic sphingomyelinase, hydrogen peroxide (H(2)O(2)) accumulation and caspase cascades results in a significant reduction of apoptotic/necrotic death induced by mixed ZD1839 and SNP in EGF-stimulated PC3 cells. In addition, the combined ZD1839 plus SNP also induced a higher cellular ceramide and reactive oxygen species (ROS) production, mitochondrial transmembrane potential decrease, and cytochrome c amount released into cytosol as compared to drugs alone.

CONCLUSIONS

The simultaneous use of EGFR inhibitor and compound releasing NO(*) might lead to a synergy in the ceramide and ROS production which might cause cellular membrane damages resulting in a massive apoptotic/necrotic death of metastatic PC cells.

Ceramide induces caspase-dependent and -independent apoptosis in A-431 cells

We investigated the ceramide-induced apoptosis and potential mechanism in A-431 cells. Ceramide treatment causes the round up and the death of A-431 cells that is associated with p38 activation and can be observed in 10 h. Short-time ceramide treatment-induced cell death is not associated with the typical apoptotic phenotypes, such as the translocation of phosphatidylserine (PS) from inner layer to outer layer of the plasma membrane, loss of mitochondrial membrane potential, DNA fragmentation, caspase activation, and PARP or PKC-delta degradation. SB202190, a specific inhibitor of p38 mitogen-activated protein (MAP) kinase, but not caspase inhibitor, blocks the cell death induced by short-time ceramide treatment (within 12 h). Whereas neither inhibition of p38 MAP kinase nor inhibition of caspases blocks cell death induced by prolonged ceramide treatment. Moreover, incubation of cells with ceramide for a long time (over 12 h) results in the reduction of proportion of S phase accompanied with typical apoptotic cell death phenotypes that are different from the cell death induced by short-time ceramide treatment. Our data demonstrated that ceramide-induced apoptotic cell death involves both caspase-dependent and caspase-independent signaling pathways. The caspase-independent cell death that occurred in relatively early stage of ceramide treatment is mediated via p38 MAP kinase, which can progress into a stage that is associated with changes of cell cycle events and involves both caspase-dependent and -independent mechanisms.

Novel ceramide analogs as potential chemotherapeutic agents in breast cancer

Recent evidence suggests a role for aberrant ceramide levels in the pathogenesis of cancer and chemoresistance and indicates that manipulation of tumor ceramide levels may be a useful strategy in the fight against breast cancer. This study demonstrates that alterations in the degree and position of unsaturation of bonds in the sphingoid backbone of d-erythro-N-octanoyl-sphingosine (Cer) affect the antiproliferative ability of ceramide analogs in breast cancer cells. The most potent analog of Cer we tested is (2S,3R)-(4E,6E)-2-octanoylamidooctadecadiene-1,3-diol (4,6-diene-Cer), which contains an additional trans double bond at C(6)-C(7) of the sphingoid backbone. 4,6-Diene-Cer exhibited higher potency than Cer in tumor necrosis factor (TNF)-alpha-resistant (IC(50) of 11.3 versus 32.9 microM) and TNF-alpha-sensitive (IC(50) of 13.7 versus 37.7 microM) MCF-7 cells. 4,6-Diene-Cer was also more potent than Cer in inducing cell death in MDA-MB-231 and NCI/ADR-RES breast cancer cell lines (IC(50) of 3.7 versus 11.3 microM, and 24.1 versus 86.9 microM, respectively). 4,6-Diene-Cer caused a prolonged elevation of intracellular ceramide levels in MCF-7 cells, which may contribute to its enhanced cytotoxicity. Furthermore, treatment of MCF-7 cells with Cer or 4,6-diene-Cer resulted in induction of apoptosis by 8 h via the mitochondrial pathway, as demonstrated by release of cytochrome c, loss of membrane asymmetry (measured by Annexin V staining), and a decrease in the mitochondrial membrane potential. Importantly, both Cer and 4,6-diene-Cer displayed selectivity toward transformed breast cells over nontransformed breast epithelial cells. These data suggest that these and other novel ceramide analogs represent potential therapeutic agents in breast cancer treatment.

A phase II study of topical ceramides for cutaneous breast cancer

PURPOSE

Short chain ceramides induce tumor cell apoptosis in preclinical models. Limited therapeutic options for patients with cutaneous breast cancer prompted the testing of these sphingolipids in patients with this disease.

PATIENTS AND METHODS

Twenty-five patients with refractory, cutaneous breast cancer were treated twice a day with a 1% mixture of topical C2 and C6 ceramides administered in a 1:1 ratio. For the first 8 weeks, patients were not allowed to receive other antineoplastic therapy. In addition to tumor status and toxicity assessment throughout the trial, skin biopsies for evidence of apoptosis and quality of life questionnaires (FACT-BR) were completed at baseline and 1 month.

RESULTS

Only one patient manifested a partial response with topical ceramides, yielding a response rate of 4% (90% confidence interval 0, 17.6%). Median cutaneous progression-free survival was 2 months. The topical ceramides were also well tolerated, with no grade 3 or 4 toxicity reported. None of the six patients who underwent serial skin biopsies showed increased tumor cell apoptosis morphologically or by the modified TUNEL assay.

CONCLUSION

To our knowledge, this trial is one of the first clinical investigations of short chain ceramides. This trial's results are not promising enough to merit further study of ceramides in the manner prescribed.

On-line solid-phase extraction of ceramides from yeast with ceramide III imprinted monolith

A molecularly imprinted polymeric monolith (MIPM) was prepared by in situ polymerization using styrene, glycidyl methacrylate and methacrylic acid as monomers, divinylbenzene and triallyl isocyanurate as cross-linking agents, and ceramide III as print molecule. The texture, pore size distribution, mobile phase flow characteristic, and chromatographic performance of the MIPM and a control monolith synthesized without the print molecule were examined, respectively. The results showed that using ceramide III as print molecule significantly affected the pore structure and pore distribution of the monolith, and greatly improved the retention of ceramide III and its analogues used in cosmetics as well. The retention of ceramide III on the MIPM could be reduced by increasing the ratio of chloroform to hexane in eluting buffer. The workability of the MIPM was firstly demonstrated through the separation of a model lipid mixture containing ceramide III and ergosterol, the main sterol impurity in yeast lipid extracts. The application of the ceramide III imprinted monolith to the isolation of ceramides from yeast lipid extracts was attempted and resulted in a considerable enrichment of ceramides, as shown by FIIR analysis. This indicates the potential of ceramide III imprinted monolith synthesized in the present study in the on-line solid-phase extraction of ceramides from yeast.

New advances on structural and biological functions of ceramide in apoptotic/necrotic cell death and cancer

Recent data on the cellular ceramide functions and its involvement in the apoptotic/necrotic cell death as well as its anticarcinogenic properties are presented. The emphasis is on the connections between the ceramide and caspase signaling pathways during the apoptotic cell death process. Notably, the experimental strategies and pharmacological tools used for establishment of the role of ceramide in triggering cell death are described. Moreover, the importance of a compartmentation of endogenous ceramide within the plasma membrane microdomains, lysosomes and mitochondria is discussed. Information on the deregulated functions of ceramide and caspase signaling pathways in several metastatic cancer types is also presented.