Sphingomyelin nanosystems loaded with uroguanylin and etoposide for treating metastatic colorectal cancer

Colorectal cancer is the third most frequently diagnosed cancer malignancy and the second leading cause of cancer-related deaths worldwide. Therefore, it is of utmost importance to provide new therapeutic options that can improve survival. Sphingomyelin nanosystems (SNs) are a promising type of nanocarriers with potential for association of different types of drugs and, thus, for the development of combination treatments. In this work we propose the chemical modification of uroguanylin, a natural ligand for the Guanylyl Cyclase (GCC) receptor, expressed in metastatic colorectal cancer tumors, to favour its anchoring to SNs (UroGm-SNs). The anti-cancer drug etoposide (Etp) was additionally encapsulated for the development of a combination strategy (UroGm-Etp-SNs). Results from in vitro studies showed that UroGm-Etp-SNs can interact with colorectal cancer cells that express the GCC receptor and mediate an antiproliferative response, which is more remarkable for the drugs in combination. The potential of UroGm-Etp-SNs to treat metastatic colorectal cancer cells was complemented with an in vivo experiment in a xenograft mice model.

Physicochemical stability of etoposide diluted at range concentrations between 0.38 and 1.75 mg/mL in polyolefin bags

Introduction

According to the manufacturers, the diluted solution of etoposide should not exceed 0.4 mg/mL because precipitation may occur. For high doses or for patients requiring fluid restrictions, etoposide phosphate may be an option but shortages occurs frequently. The objective of this work was to study the stability of etoposide solutions between 0.38 and 1.75 mg/mL, diluted in 0.9% sodium chloride (0.9% NaCl) or 5% glucose (G5%) in polyolefin bags, stored at 25°C and between 2°C to 8°C, in a 61-day period. This study also observed the impact of an infusion pump on the physical and chemical stability of etoposide solutions.

Materials and method

Chemical stability was analysed at days 0, 9, 16, 21, 28 and 61 by high-performance liquid chromatography. Physical stability was evaluated by visual and subvisual inspection. The action of an infusion pump on solutions was evaluated to verify the impact of the mechanical pumping action on the etoposide solutions. This investigation was performed at day 61, at the end of the study.

Results

Etoposide solutions diluted at 0.38, 0.74 and 1.26 mg/mL in G5% and stored at 25°C were stable for 61 days and at 1.75 mg/mL for 28 days. In 0.9% NaCl, etoposide was less stable, with more precipitations observed. The action of an infusion pump has not caused any physical modifications.

Conclusion

Storage at 25°C and G5% as diluent are recommended for etoposide high concentration with 61-day stability up to a concentration of 1.26 mg/mL and 28-day stability up to a concentration of 1.75 mg/mL. As a precaution, the use of an administration set with an in-line micro-filter is nevertheless recommended. Storage at 2°C to 8°C and the use of 0.9% NaCl increase the risk of precipitation.

Topoisomerase II-Induced Chromosome Breakage and Translocation Is Determined by Chromosome Architecture and Transcriptional Activity

Topoisomerase II (TOP2) relieves torsional stress by forming transient cleavage complex intermediates (TOP2ccs) that contain TOP2-linked DNA breaks (DSBs). While TOP2ccs are normally reversible, they can be "trapped" by chemotherapeutic drugs such as etoposide and subsequently converted into irreversible TOP2-linked DSBs. Here, we have quantified etoposide-induced trapping of TOP2ccs, their conversion into irreversible TOP2-linked DSBs, and their processing during DNA repair genome-wide, as a function of time. We find that while TOP2 chromatin localization and trapping is independent of transcription, it requires pre-existing binding of cohesin to DNA. In contrast, the conversion of trapped TOP2ccs to irreversible DSBs during DNA repair is accelerated 2-fold at transcribed loci relative to non-transcribed loci. This conversion is dependent on proteasomal degradation and TDP2 phosphodiesterase activity. Quantitative modeling shows that only two features of pre-existing chromatin structure-namely, cohesin binding and transcriptional activity-can be used to predict the kinetics of TOP2-induced DSBs.

Octreotide-Conjugated Core-Cross-Linked Micelles with pH/Redox Responsivity Loaded with Etoposide for Neuroendocrine Neoplasms Therapy and Bioimaging with Photoquenching Resistance

The study of multifunctional polymer micelles combined with chemotherapy due to reduced systemic toxicity and enhanced efficacy has attracted intensive attention. Herein, a multifunctional core-cross-linked hybrid micelle system based on mPEG- b-PGu(BA-TPE) and OCT-PEG- b-PGu(DA-TPE) with pH- and redox-triggered drug release and aggregation-induced emission (AIE) active imaging has been developed for active targeting of neuroendocrine neoplasms (NENs), especially neuroendocrine carcinomas (NECs) with poor prognosis. These micelles showed excellent biocompatibility and stability. After the formation of borate ester bonds, core-cross-linked micelles (CCLMs) showed enhanced emission properties. In addition, etoposide (ETO), one of the most important anticancer drugs of NECs, was loaded into the hydrophobic core of micelles by self-assembly with an average diameter of 274.6 nm and spherical morphology. Octreotide (OCT) conjugated onto the micelles enhanced cellular uptake by receptor-mediated endocytosis. ETO-loaded micelles demonstrated the dual-responsive triggered intracellular drug release and great tumor suppression ability in vitro. Compared with free ETO, ETO-loaded CCLMs exhibited a considerable antitumor effect and significantly reduced side effects. Considering the active tumor targeting, dual-responsive drug release and the AIE effect, the polymer micelle system will be a potential candidate for diagnosis and oncotherapy of NENs.

Generating digital drug cocktails via optical manipulation of drug-containing particles and photo-patterning of hydrogels

An integrated microfluidic system combining 1) an optically-induced-dielectrophoresis (ODEP) module for manipulation of drug-containing particles and 2) an ultraviolet (UV) "direct writing" module capable of patterning hydrogels was established herein for automatic formulation of customized digital drug cocktails. Using the ODEP module, the drug-containing particles were assembled by using moving light patterns generated from a digital projector. The hydrogel, poly(ethylene glycol) diacrylate (PEGDA), was used as the medium in the ODEP module such that the assembled drug-containing particles could be UV-cured and consequently encapsulated in "pills" of specific sizes and shapes by using the UV direct writing module. At an optimal ODEP force of 335 pN, which was achieved in a solution of 15% PEGDA in 0.2 M sucrose, it was possible to manipulate and UV-cure the drug-containing particles. Furthermore, with a digital micromirror device inside the UV direct writing module, different UV patterns could be designed and projected, allowing for the digital drug cocktails to be packaged into different shapes in <60 s. As a demonstration, emulsion droplets containing two different anti-cancer drugs were further tested to show the capability of the developed device. This represents an automatic digital drug cocktail formulating device which stands to revolutionize personalized medicine.

Targeted delivery of etoposide, carmustine and doxorubicin to human glioblastoma cells using methoxy poly(ethylene glycol)‑poly(ε‑caprolactone) nanoparticles conjugated with wheat germ agglutinin and folic acid

Wheat germ agglutinin (WGA) and folic acid (FA)-grafted methoxy poly(ethylene glycol) (MPEG)‑poly(ε‑caprolactone) (PCL) nanoparticles (WFNPs) were applied to transport anticancer drugs across the blood-brain barrier and treat glioblastoma multiforme (GBM). PCL was copolymerized with MPEG, and MPEG-PCL NPs were stabilized with pluronic F127 using a microemulsion-solvent evaporation technique and crosslinked with WGA and FA. The targeting ability of WFNPs loaded with etoposide (ETO), carmustine (BCNU) and doxorubicin (DOX) was investigated via the binding affinity of drug-loaded NP formulations to N‑acetylglucosamine expressed in human brain microvascular endothelial cells and to folate receptor in malignant U87MG cells. We found that a shorter PCL chain in drug-loaded MPEG-PCL NPs yielded a smaller average size of the particles. An increase in PCL chain length (stronger hydrophobicity) enhanced drug entrapment efficiencies in MPEG-PCL NPs, and reduced drug-releasing rates from NP formulations. In addition, anti-proliferative activity against U87MG cells for the 3 drugs followed the order of WFNPs > FA-grafted NPs > WGA-grafted NPs > MPEG-PCL NPs. Immunofluorescence staining revealed that the ligands of drug-loaded WFNPs connected to N‑acetylglucosamine and folate receptor with the help of surface WGA and FA. WFNPs carrying ETO, BCNU and DOX acted as dual-targeting nanocarriers, and their use can be a promising approach to inhibiting GBM growth in the brain.

Bioengineering the spider silk sequence to modify its affinity for drugs

BACKGROUND

Silk is a biocompatible and biodegradable material, able to self-assemble into different morphological structures. Silk structures may be used for many biomedical applications, including carriers for drug delivery. The authors designed a new bioengineered spider silk protein, EMS2, and examined its property as a carrier of chemotherapeutics.

MATERIALS AND METHODS

To obtain EMS protein, the MS2 silk monomer (that was based on the MaSp2 spidroin of Nephila clavipes) was modified by the addition of a glutamic acid residue. Both bioengineered silks were produced in an Escherichia coli expression system and purified by thermal method. The silk spheres were produced by mixing with potassium phosphate buffer. The physical properties of the particles were characterized using scanning electron microscopy, atomic force microscopy, Fourier-transform infrared spectroscopy, and zeta potential measurements. The MTT assay was used to examine the cytotoxicity of spheres. The loading and release profiles of drugs were studied spectrophotometrically.

RESULTS

The bioengineered silk variant, EMS2, was constructed, produced, and purified. The EMS2 silk retained the self-assembly property and formed spheres. The spheres made of EMS2 and MS2 silks were not cytotoxic and had a similar secondary structure content but differed in morphology and zeta potential values; EMS2 particles were more negatively charged than MS2 particles. Independently of the loading method (pre- or post-loading), the loading of drugs into EMS2 spheres was more efficient than the loading into MS2 spheres. The advantageous loading efficiency and release rate made EMS2 spheres a good choice to deliver neutral etoposide (ETP). Despite the high loading efficiency of positively charged mitoxantrone (MTX) into EMS2 particles, the fast release rate made EMS2 unsuitable for the delivery of this drug. A faster release rate from EMS2 particles compared to MS2 particles was observed for positively charged doxorubicin (DOX).

CONCLUSION

By modifying its sequence, silk affinity for drugs can be controlled.

Polymer-lipid hybrid nanoparticles-based paclitaxel and etoposide combinations for the synergistic anticancer efficacy in osteosarcoma

In this study, paclitaxel and etoposide-loaded lipid-polymer hybrid nanoparticles (PE-LPN) was successful prepared and evaluated for physicochemical and anticancer effect. Nanosized PE-LPN was obtained with a perfect spherical morphology. PE-LPN exhibited a controlled release of two drugs in a sequential manner. The nanoparticles exhibited a typical endocytosis-mediated cellular uptake in cancer cells. The ratiometric combination of paclitaxel (PTX) and etoposide (ETP) were significantly more cytotoxic than individual drugs. Importantly, superior cytotoxic effect was observed for dual-drug-loaded PE-LPN than cocktail combination at a much lower dose. Similarly, PE-LPN exhibited a significantly higher apoptosis of cancer cells (∼45%) compared to that of any other groups with higher caspase-3 and -8 activity. Importantly, PE-LPN showed a remarkable tumor regression effect and exhibited a 2-fold superior efficacy than free drugs. PE-LPN treated group showed significantly less Ki-67 positive cells (less than 25%) than PTX/ETP and single drug treated groups, suggesting less active cell proliferation and a considerably higher tumor growth inhibition effect. The results collectively showed that combination of drugs could greatly improve the therapeutic property of chemotherapeutic drugs. By combining ETP with PTX (a powerful anticancer drug) in a polymer-lipid hybrid nanoparticle system, therapeutic efficacy could be improved in osteosarcoma treatments.

DNA breaks and chromatin structural changes enhance the transcription of autoimmune regulator target genes

The autoimmune regulator (AIRE) protein is the key factor in thymic negative selection of autoreactive T cells by promoting the ectopic expression of tissue-specific genes in the thymic medullary epithelium. Mutations in AIRE cause a monogenic autoimmune disease called autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy. AIRE has been shown to promote DNA breaks via its interaction with topoisomerase 2 (TOP2). In this study, we investigated topoisomerase-induced DNA breaks and chromatin structural alterations in conjunction with AIRE-dependent gene expression. Using RNA sequencing, we found that inhibition of TOP2 religation activity by etoposide in AIRE-expressing cells had a synergistic effect on genes with low expression levels. AIRE-mediated transcription was not only enhanced by TOP2 inhibition but also by the TOP1 inhibitor camptothecin. The transcriptional activation was associated with structural rearrangements in chromatin, notably the accumulation of γH2AX and the exchange of histone H1 with HMGB1 at AIRE target gene promoters. In addition, we found the transcriptional up-regulation to co-occur with the chromatin structural changes within the genomic cluster of carcinoembryonic antigen-like cellular adhesion molecule genes. Overall, our results suggest that the presence of AIRE can trigger molecular events leading to an altered chromatin landscape and the enhanced transcription of low-expressed genes.

Microbial growth tests in anti-neoplastic injectable solutions

The Institut Gustave-Roussy (IGR) Department of Clinical Pharmacy (DCP) ensures the annual preparation of about 30 000 therapeutic batches of anti-neoplastic agents.High performance thin-layer chromatography (HPTLC) allows postproduction quality control of these batches.Although the centralized chemotherapy manufacturing unit has been recently ISO 9001:2000 certified, it was considered to improve the quality level of manufactured batches even further.The viability of micro-organisms (bacteria and fungi) in appropriate sterile media containing various anti-neoplastic agents at therapeutic concentration was assessed to demonstrate the lack of contamination during our manufacturing process in the isolator.After 14 days of incubation in these media, the results show the absence of contamination of the manufactured batches.This leads us to conclude that using sterile drugs and sterile medical devices in a sterile isolator allows the manufacture of sterile therapeutic batches with excellent confidence.

Preparation and Evaluation of a Novel Class of Amphiphilic Amines as Antitumor Agents and Nanocarriers for Bioactive Molecules

Purpose

We describe a novel class of antitumor amphiphilic amines (RCn) based on a tricyclic amine hydrophilic head and a hydrophobic linear alkyl tail of variable length.

Methods

We tested the lead compound, RC16, for cytotoxicity and mechanism of cell death in several cancer cell lines, anti tumor efficacy in mouse tumor models, and ability to encapsulate chemotherapy drugs.

Results

These compounds displayed strong cytotoxic activity against cell lines derived from both pediatric and adult cancers. The IC50 of the lead compound, RC16, for normal cells including human keratinocytes, human fibroblasts and human umbilical vein endothelial cells was tenfold higher than for tumor cells. RC16 exhibited significant antitumor effects in vivo using several human xenografts and a metastatic model of murine neuroblastoma by both intravenous and oral administration routes. The amphiphilic character of RC16 triggered a spontaneous molecular self-assembling in water with formation of micelles allowing complexation of Doxorubicin, Etoposide and Paclitaxel. These micelles significantly improved the in vitro antitumor activity of these drugs as the enhancement of their aqueous solubility also improved their biologic availability.

Conclusions

RC16 and related amphiphilic amines may be useful as a novel cancer treatment.

Electronic supplementary material

The online version of this article (doi:10.1007/s11095-016-1999-9) contains supplementary material, which is available to authorized users.

Fluorescence Characterization of Gold Modified Liposomes with Antisense N-myc DNA Bound to the Magnetisable Particles with Encapsulated Anticancer Drugs (Doxorubicin, Ellipticine and Etoposide)

Liposome-based drug delivery systems hold great potential for cancer therapy. The aim of this study was to design a nanodevice for targeted anchoring of liposomes (with and without cholesterol) with encapsulated anticancer drugs and antisense N-myc gene oligonucleotide attached to its surface. To meet this main aim, liposomes with encapsulated doxorubicin, ellipticine and etoposide were prepared. They were further characterized by measuring their fluorescence intensity, whereas the encapsulation efficiency was estimated to be 16%. The hybridization process of individual oligonucleotides forming the nanoconstruct was investigated spectrophotometrically and electrochemically. The concentrations of ellipticine, doxorubicin and etoposide attached to the nanoconstruct in gold nanoparticle-modified liposomes were found to be 14, 5 and 2 µg·mL⁻¹, respectively. The study succeeded in demonstrating that liposomes are suitable for the transport of anticancer drugs and the antisense oligonucleotide, which can block the expression of the N-myc gene.

pH sensitive nano layered double hydroxides reduce the hematotoxicity and enhance the anticancer efficacy of etoposide on non-small cell lung cancer

Etoposide (VP16), used for the treatment of many carcinomas, can cause leukopenia, thrombocytopenia and hair loss. To overcome the side effects and achieve target therapy, layered double hydroxides (LDHs), a pH sensitive layered double hydroxide nanohybrid, was used here as a nano-carrier. The functions of LDHs-VP16 on non-small cell lung cancer (NSCLC) were firstly explored both in vitro and in vivo. In A549 cell line, LDH-VP16 induced apoptosis 2.3-fold as that of plain VP16 by targeting to mitochondrial, stocking cells in G1 phase. The cellular uptake demonstrated the delivery of LDH for VP16 to pass through the membrane and accumulate in mitochondria. As a carrier, LDH greatly decreased the liver toxicity and hematotoxicity of VP16. The detected liver parameters, including glutamic-oxaloacetic transaminase (AST), alkaline phosphatase (ALP), alanine aminotransferase (ALT), were all turn back to normal range after the delivery of LDH, except ALP. In vivo, LDH-VP16 reduced A549 tumor growth significantly by 60.5%, whereas native VP16 exerted no significant anticancer activity. In LDH-VP16 treated mice, the AUC was increased by 6.26 folds as the native drug, and t1/2 of LDH-VP16 was prolonged from 6.68 to 98.78h. LDH-VP16 showed a targeting effect, which largely increase the concentration in tumor and lung. The phosphorylation antibody array and Western Blot of proteins from xenografts revealed that PI3K-AKT signaling was suppressed in the LDH-VP16 treated tumor, while in VP16 treated mice, ERBB signaling pathway was involved. These results suggested that LDH-VP16 diminishes hematotoxicity, targets NSCLC tumor, performs more effectively than VP16, and different signaling pathway is involved compared to VP16.

STATEMENT OF SIGNIFICANCE

This paper explored that nano-sized layered double hydroxide (LDH) could be used as a pH sensitive delivery system to overcome hematotoxicity and enhance the bioavailability and anticancer efficacy of etoposide (VP16) against non small cell lung cancer, which was not reported before, as the best of our knowledge. We found that the liver and hematotoxicity is nearly recovered after the loading of VP16 in pH sensitive LDH, which prongs the half time from 6.68h to 98h, helps target VP16 to tumor and lung, and protects white blood cells by its pH sensitive and nano-size property. LDH-VP16 achieve markedly performance on non-small cell lung cancer by targeting to mitochondria of A549 cells in vitro and effectively inhibiting the PI3K-AKT signaling pathway in vivo. The inhibition ratio of VP16 on A549 tumor growth is increased from less than 20% (no significance compared to control) to 60.5% after the delivery of LDH. This work provides a novel system for the safe and efficient use of etoposide on non-small cell lung cancer and explores the mechanism of the function of nano carrier in cancer therapy both in vitro and in vivo.

[Stability of high-dose etoposide dilutions for use in hematopoietic stem cell transplantation conditioning regimens]

High-dose etoposide is used in conditioning regimens for allogeneic stem cell transplantation. The limited stability of the drug induces barriers for its use for pharmacists, nurses and patients. When using a concentration of 10 mg/mL etoposide in physiologic saline, limitations can be overcome. This study provides stability data for etoposide in a high concentration that can be used in conditioning regimens. The solution was stable for 48h at 5°C, for 48h at 5°C followed by 8h at 25°C and for 24 h at 25°C.

Enhanced Anti-Metastatic Activity of Etoposide Using Layered Double Hydroxide Nano Particles

Cell migration and invasion are integral to lung cancer metastasis. In this study, we investigated the combination of traditional chemotherapy and a layered double hydroxide (LDH) carrier as a new strategy for the inhibition of migration and invasion. To investigate the characteristics and possible mechanisms of VP16-LDH [the Mg-Al/LDH containing etoposide (VP16)], we used several experimental techniques, such as transmission electron microscopy (TEM) and fluorescent microscopy. The TEM, X-ray diffraction (XRD) and zeta potential results indicated that VP16 binds well with LDH, with an average size of 70 nm, and the drug delivery system was confirmed to have the desired quality of slow release by the in vitro release test results. Fluorescent images showed that the cellular uptake of VP16-LDH was a caveolae-mediated and energy-dependent process. Moreover, A549 cells treated with VP16-LDH (5 μg/ml, 10 μg/ml) demonstrated significant inhibition of cell migration and invasion compared with the cells treated with free VP16 at the same concentration. The inhibition of AKT, mTOR and STAT3 phosphorylation and p-β-catenin up-regulation in VP16-LDH-treated cells revealed a possible molecular mechanism via the mTOR/AKT and STAT pathways, through which VP16-LDH had a stronger inhibitory effect on migration than the drug alone.

Theranostic etoposide phosphate/indium nanoparticles for cancer therapy and imaging

Etoposide phosphate (EP), a water-soluble anticancer prodrug, is widely used for treatment of many cancers. After administration it is rapidly converted to etoposide, its parent compound, which exhibits anticancer activity. Difficulty in parenteral administration necessitates the development of a suitable nanoparticle delivery system for EP. Here we have used indium both as a carrier to deliver etoposide phosphate to tumor cells and as a SPECT imaging agent through incorporation of (111)In. Etoposide phosphate was successfully encapsulated together with indium in nanoparticles, and exhibited dose dependent cytotoxicity and induction of apoptosis in cultured H460 cancer cells via G2/M cell cycle arrest. In a mouse xenograft lung cancer model, etoposide phosphate/indium nanoparticles induce tumor cell apoptosis, leading to significant enhancement of tumor growth inhibition compared to the free drug.

Head-To-Head Comparison of Different Solubility-Enabling Formulations of Etoposide and Their Consequent Solubility-Permeability Interplay

The purpose of this study was to conduct a head-to-head comparison of different solubility-enabling formulations, and their consequent solubility-permeability interplay. The low-solubility anticancer drug etoposide was formulated in several strengths of four solubility-enabling formulations: hydroxypropyl-β-cyclodextrin, the cosolvent polyethylene glycol 400 (PEG-400), the surfactant sodium lauryl sulfate, and an amorphous solid dispersion formulation. The ability of these formulations to increase the solubility of etoposide was investigated, followed by permeability studies using the parallel artificial membrane permeability assay (PAMPA) and examination of the consequent solubility-permeability interplay. All formulations significantly increased etoposide's apparent solubility. The cyclodextrin-, surfactant-, and cosolvent-based formulations resulted in a concomitant decreased permeability that could be modeled directly from the proportional increase in the apparent solubility. On the contrary, etoposide permeability remained constant when using the ASD formulation, irrespective of the increased apparent solubility provided by the formulation. In conclusion, supersaturation resulting from the amorphous form overcomes the solubility-permeability tradeoff associated with other formulation techniques. Accounting for the solubility-permeability interplay may allow to develop better solubility-enabling formulations, thereby maximizing the overall absorption of lipophilic orally administered drugs.

Paclitaxel and etoposide co-loaded polymeric nanoparticles for the effective combination therapy against human osteosarcoma

BACKGROUND

The combination of chemotherapeutic drugs with different pharmacological action has emerged as a promising therapeutic strategy in the treatment of cancers. Present study examines the antitumor potential of paclitaxel (PTX) and etoposide (ETP)-loaded PLGA nanoparticles for the treatment of osteosarcoma.

RESULTS

The resulting drug-loaded PLGA NP exhibited a nanosize dimension with uniform spherical morphology. The NP exhibited a sustained release profile for both PTX and ETP throughout the study period without any sign of initial burst release. The combinational drug-loaded PLGA NP enhanced the cytotoxic effect in MG63 and Saos-2 osteosarcoma cell lines, in comparison to either native drug alone or in cocktail combinations. Additionally, NPs showed an appreciable uptake in MG63 cells in a time-based manner. Co-delivery of anticancer drugs resulted in enhanced cell cycle arrest and cell apoptosis. The results clearly showed that combinational drugs remarkably improved the therapeutic index of chemotherapeutic drugs. The greater inhibitory effect of nanoparticle combination would be of great advantage during systemic cancer therapy.

CONCLUSION

Taken together, our study demonstrated that PTX-ETP/PLGA NP based combination therapy holds significant potential towards the treatment of osteosarcoma.

Degradation of the cytostatic etoposide in chlorinated water by liquid chromatography coupled to quadrupole-Orbitrap mass spectrometry: identification and quantification of by-products in real water samples

Once discharged into the sewage system, many pharmaceuticals may undergo degradation reactions in the presence of chemical disinfectants, generating by-products that may possess enhanced toxicity relative to the parent compounds. For this reason, the stability of the widely used cytostatic etoposide in chlorinated water has been investigated for the first time in the present work. Taking advantage of the high-resolution/accurate-mass capabilities of the hybrid quadrupole-Orbitrap mass spectrometer Q Exactive, two new oxidation by-products of etoposide were reliably identified. The time course of etoposide and its by-products was followed at different pH values, free chlorine concentrations and water matrices. Finally, the occurrence of etoposide and its major identified by-product (3'-O-desmethyl etoposide) was investigated in real water samples by on-line solid-phase extraction-liquid chromatography-tandem mass spectrometry using a 4000QTRAP hybrid quadrupole-linear ion trap mass spectrometer. The etoposide by-product was found in various river and wastewater samples at levels between 14 and 33 ng L(-1), whereas etoposide was not detected in any sample.

Synthesis and cytotoxic evaluation of alkoxylated chalcones

A series of chalcones a1–20 bearing a 4-OMe groups on the A-ring were initially synthesized and their anticancer activities towards HepG2 cells evaluated. Subsequently, a series of chalcones b1–42 bearing methoxy groups at the 2' and 6'-positions of the B-ring were synthesized and their anticancer activities towards five human cancer cell lines (HepG2, HeLa, MCF-7, A549 and SW1990) and two non-tumoral human cell lines evaluated. The results showed that six compounds (b6, b8, b11, b16, b18, b22, b23 and b29) displayed promising activities, with compounds b22 and b29 in particular showing higher levels of activity than etoposide against all five cancer cell lines. Compound b29 showed a promising SI value compared with both HMLE and L02 (2.1–6.5 fold in HMLE and > 33 > 103.1 fold in L02, respectively).

Physicochemical properties of liposomes as potential anticancer drugs carriers. Interaction of etoposide and cytarabine with the membrane: spectroscopic studies

The interactions between etoposide, cytarabine and 1,2-dihexadecanoyl-sn-glycerol-3-phosphocholine bilayers were studied using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (NMR). These techniques have proven to be a very powerful tool in studying the structure and dynamics of phospholipid bilayers. In particular, DSC can provide information on the phase transition temperature and cooperativity of the lipid molecules in the absence and presence of the drug. Vibrational spectroscopy is well suited to the study of drug-lipid interactions, since it allows for an investigation of the conformation of phospholipid molecules at different levels in lipid bilayers and follows structural changes that occur during the gel to liquid-crystalline phase transition. NMR supported the determination of the main phase transition temperatures (TC) of 1,2-dihexadecanoyl-sn-glycerol-3-phosphocholine (DPPC). The main phase transition temperature (TC) determined by (1)H NMR is comparable with values obtained by DSC for all studied liposomes. The location of cytarabine and etoposide in liposomes was also determined by NMR. Atomic force microscopy (AFM) images, acquired immediately after sample deposition on a mica surface, revealed the spherical shape of lipid vesicles.

Drug-induced histone eviction from open chromatin contributes to the chemotherapeutic effects of doxorubicin

DNA topoisomerase II inhibitors are a major class of cancer chemotherapeutics, which are thought to eliminate cancer cells by inducing DNA double-strand breaks. Here we identify a novel activity for the anthracycline class of DNA topoisomerase II inhibitors: histone eviction from open chromosomal areas. We show that anthracyclines promote histone eviction irrespective of their ability to induce DNA double-strand breaks. The histone variant H2AX, which is a key component of the DNA damage response, is also evicted by anthracyclines, and H2AX eviction is associated with attenuated DNA repair. Histone eviction deregulates the transcriptome in cancer cells and organs such as the heart, and can drive apoptosis of topoisomerase-negative acute myeloid leukaemia blasts in patients. We define a novel mechanism of action of anthracycline anticancer drugs doxorubicin and daunorubicin on chromatin biology, with important consequences for DNA damage responses, epigenetics, transcription, side effects and cancer therapy.

Targeting etoposide to acute myelogenous leukaemia cells using nanostructured lipid carriers coated with transferrin

The aim of the present study was to evaluate the diverse properties of transferrin (Tf)-conjugated nanostructured lipid carriers (NLCs) prepared using three different fatty amines, including stearylamine (SA), dodecylamine (DA) and spermine (SP), and two different methods for Tf coupling. Etoposide-loaded NLCs were prepared by an emulsion-solvent evaporation method followed by probe sonication. Chemical coupling of NLCs with Tf was mediated by an amide linkage between the surface-exposed amino group of the fatty amine and the carboxyl group of the protein. The physical coating was performed in a Ringer-Hepes buffer medium. NLCs were characterized by their particle size, zeta potential, polydispersity index, drug entrapment percentage, drug release profiles and Tf-coupling efficiency. The cytotoxicity of NLCs on K562 acute myelogenous leukaemia cells was studied by MTT assay, and their cellular uptake was studied by a flow cytometry method. SA-containing NLCs showed the lowest particle size, the highest zeta potential and the largest coupling efficiency values. The drug entrapment percentage and the zeta potential decreased after Tf coupling, but the average particle size increased. SP-containing formulations released their drug contents comparatively slower than SA- or DA-containing NLCs. Unconjugated NLCs released moderately more drug than Tf-NLCs. Flow cytometry studies revealed enhanced cellular uptake of Tf-NLCs compared to unconjugated ones. Blocking Tf receptors resulted in a significantly higher cell survival rate for Tf-NLCs. The highest cytotoxic activity was observed in the chemically coupled SA-containing nanoparticles, with an IC(50) value of 15-fold lower than free etoposide.

Innovative in vitro chemo-hormonal drug therapy for refractory thyroid carcinomas

More than 95% of the thyroid carcinomas are well differentiated types showing favorable prognosis. However, only a few therapeutic options are available to treat the patients with undifferentiated thyroid carcinomas, especially with refractory thyroid carcinomas that are not amenable to surgery or radioiodine ablation. We investigated the anticancer effects of 20 chemotherapy and hormonal therapy drugs on 8 thyroid carcinoma cell lines. In vitro chemosensitivity was tested using the adenosine-triphosphate-based chemotherapy response assay (ATP-CRA). The tumor inhibition rate (TIR; or cell death rate) or half maximal inhibitory concentration (IC(50)) was analyzed to interpret the results. Of the 12 chemotherapy drugs, etoposide (178.9 index value in follicular carcinoma cell line) and vincristine (211.7 in Hürthle cell carcinoma cell line) were the most active drugs showing the highest chemosensitivity, and of the 8 additional drugs, trichostatin A (0.03 µg/mL IC(50) in follicular carcinoma cell line) showed favorable outcome having the anticancer effect. In our study, the result of etoposide and vincristine show evidence as active anticancer drugs in thyroid carcinoma cell lines and trichostatin A seems be the next promising drug. These drugs may become an innovative therapy for refractory thyroid carcinomas in near future.

Induction of cell cycle arrest by GL331 via triggering an ATM-dependent DNA damage response in HepG2 cells

GL331, a topoisomerase II inhibitor, has been found to trigger DNA damage response (DDR) to induce cell cycle arrest. However, the underlying mechanism has not yet been fully understood. This study investigated the molecular mechanism involved in the GL331-induced cell cycle arrest via DDR in human hepatocellular carcinoma HepG2 cells. As a result, GL331 could induce S arrest and up-regulate the phosphorylation of the histone H2AX variant (γ-H2AX). Ataxia telangiectasia mutated protein kinase (ATM) was activated by GL331 through its autophosphorylation at Ser1981, which led to the activation of DNA damage signaling pathways including p53/p21 and Chk2/Cdc25A cascades. The DNA damage cascades triggered by GL331 finally induced the inactivation of cyclin A/Cdk2 complexes to some extent. These phenomena could be reversed by ATM siRNA, followed by a partial disruption of S arrest. The present results suggested that the S arrest induced by GL331 via DDR was in an ATM-dependent manner to some degree.

Insight into eukaryotic topoisomerase II-inhibiting fused heterocyclic compounds in human cancer cell lines by molecular docking

Etoposide is effective as an anti-tumour drug by inhibiting eukaryotic DNA topoisomerase II via establishing a covalent complex with DNA. Unfortunately, its wide therapeutic application is often hindered by multidrug resistance (MDR), low water solubility and toxicity. In our previous study, new derivatives of benzoxazoles, benzimidazoles and related fused heterocyclic compounds, which exhibited significant eukaryotic DNA topoisomerase II inhibitory activity, were synthesized and exhibited better inhibitory activity compared with the drug etoposide itself. To expose the binding interactions between the eukaryotic topoisomerase II and the active heterocyclic compounds, docking studies were performed, using the software Discovery Studio 2.1, based on the crystal structure of the Topo IIA-bound G-segment DNA (PDB ID: 2RGR). The research was conducted on a selected set of 31 fused heterocyclic compounds with variation in structure and activity. The structural analyses indicate coordinate and hydrogen bonding interactions, van der Waals interactions and hydrophobic interactions between ligands and the protein, as Topo IIA-bound G-segment DNA are responsible for the preference of inhibition and potency. Collectively, the results demonstrate that the compounds 1a, 1c, 3b, 3c, 3e and 4a are significant anti-tumour drug candidates that should be further studied.

DNA topoisomerases and their poisoning by anticancer and antibacterial drugs

DNA topoisomerases are the targets of important anticancer and antibacterial drugs. Camptothecins and novel noncamptothecins in clinical development (indenoisoquinolines and ARC-111) target eukaryotic type IB topoisomerases (Top1), whereas human type IIA topoisomerases (Top2alpha and Top2beta) are the targets of the widely used anticancer agents etoposide, anthracyclines (doxorubicin, daunorubicin), and mitoxantrone. Bacterial type II topoisomerases (gyrase and Topo IV) are the targets of quinolones and aminocoumarin antibiotics. This review focuses on the molecular and biochemical characteristics of topoisomerases and their inhibitors. We also discuss the common mechanism of action of topoisomerase poisons by interfacial inhibition and trapping of topoisomerase cleavage complexes.

Use of a cholesterol-rich microemulsion that binds to low-density lipoprotein receptors as vehicle for etoposide

A cholesterol-rich microemulsion (LDE) that binds to low-density lipoprotein (LDL) receptors is selectively taken up by malignant cells that overexpress those receptors and may be used as vehicle for antineoplastic agents. This study aimed to develop the association of etoposide with LDE. It was firstly observed that etoposide poorly associates with the microemulsion, therefore the experiments were performed with a lipophilic fatty acid derivative of the drug. The association of etoposide oleate with LDE was almost 100% and was tested for physical and chemical stability, as well as for cellular uptake, toxicity in mice and cytotoxic activity against a neoplastic cell line (NCI-H292). Uptake and cytotoxic activity of LDE-etoposide oleate by NCI-H292 cells was mediated by LDL receptors. The anti-proliferative activity of LDE-etoposide oleate against the neoplastic cells was smaller than that of etoposide oleate (IC50 (drug concentration required to inhibit 50% of the cell growth) = 0.48 and 0.19 mm, respectively). This difference, however, can be ascribed to the activity of the commercially used vehicle and not the drug itself because when this vehicle was added to the cultures with LDE-etoposide oleate, the IC50 decreased. On the other hand, the tolerability of LDE-etoposide oleate to mice was remarkable, such that its lethal dose (LD50) was about five-fold that of the commercial formulation (LD50=315 and 58 mg kg−1, respectively). In conclusion, LDE-etoposide oleate association is stable and the cytostatic activity of the drug is preserved while its toxicity to animals is small. By diminishing the side effects and directing etoposide to neoplastic tissues, LDE may be regarded as an advance in chemotherapy with this drug.

[The interaction of beta-cyclodextrin with etoposide studied by fluorescence spectroscopy]

The fluorescence spectroscopy and UV spectroscopy have been used to monitor the inclusion phenomena of VP-16 with beta-cyclodextrin (beta-CD), together with studies concerning the effects of reaction time, temperature and concentration on this behavior. The results show that the fluorescence intensity increased when VP-16 and beta-CD forming a 1 : 1 inclusion complex, which indicate that beta-CD has fluorescence sensitizing effect on the VP-16. At 22 degrees C, the inclusion constant was 2.63 x 10(5) L x mol(-1) at pH 7.0. VP-16 has maximum emission wavelength at 316 nm under the optimum conditions. According to this, the quantitative micro-detection method of VP-16 by fluorescence spectrometry was established. The linear regression equation was y = 1.107 89 x 10(70 x + 95.898 1, with a correlation coefficient of 0.999 9. The detection limit was 2.094 x 10(-7) mol x L(-1).

Comparative Study of Some Biodegradable Polymers on the Entrapment Efficiency and Release Behavior of Etoposide from Microspheres

Etoposide-loaded biodegradable microspheres of poly lactic-co-glycolide (PLGA) 50:50, PLGA 75:25, and polycaprolactone (PCL) were prepared by simple o/w emulsification solvent evaparation method and characterized by size analysis and microscopy. The influence of drug to polymer ratio on the entrapment of etoposide was studied. Of all the three types of microspheres, polycaprolactone microspheres (PCL MS) showed the highest entrapment efficiency (94.64%), followed by PLGA 75:25 microspheres (PLGA 75:25 MS) (88.64%) and PLGA 50:50 microspheres (PLGA 50:50 MS) (79.19%). The drug to polymer ratio of 1:20 gave the highest entrapment efficiency for all the three types of microspheres. The in vitro release of etoposide from the three microsphere formulations were studied in phosphate buffer pH 7.4 (pH 7.4 PB) containing 0.1% Tween 80. The microspheres showed an initial burst release, which was highest from the PLGA 50:50 MS and least from the PCL MS. PCL MS microspheres showed the lower and slow drug release than the remaining formulations. The release of etoposide from all the three microsphere formulations followed Higuchi's diffusion pattern. The microspheres in the dissolution medium for 28 days appeared irregular in shape and slightly fragmented.

Development of simulated intestinal fluids containing nutrients as transport media in the Caco-2 cell culture model: Assessment of cell viability, monolayer integrity and transport of a poorly aqueous soluble drug and a substrate of efflux mechanisms

The purpose of this study was to identify simulated intestinal fluids (SIFs) containing nutrients compatible with the Caco-2 cell culture model and to examine the impact of the identified medium on the transport of a poorly aqueous soluble model compound, estradiol, and a substrate of efflux mechanisms, etoposide. Monolayer integrity was evaluated by transepithelial electrical resistance and cellular viability by release of lactate dehydrogenase to the apical compartment and cellular protein content. It was shown that the viability of Caco-2 cells was enhanced by use of the CO(2) independent nutritional medium, Leibovitz's L-15 compared to Hanks' balanced salt solution. SIF containing 5mM sodium taurocholate and 1.25 mM phosphatidylcholine or lysophosphatidylcholine in Leibovitz's L-15 induced less release of lactate dehydrogenase than the traditional transport medium, HBSS. Addition of lipolysis products, 0.5mM oleic acid and 0.25 mM monoolein, did only cause increase in lactate dehydrogenase in 3 of 12 comparisons. The presence of SIFs in the apical compartment was shown to decrease flux of estradiol due to incorporation of estradiol in micelles and hence a decreased fraction of free estradiol. Further, a concentration dependent increase in the apparent permeability of etoposide was observed from apical to basolateral compartment, which indicated that components in the SIFs affects efflux mechanisms.

Sesquiterpenoids and flavonoids from the aerial parts of Tithonia diversifolia and their cytotoxic activity

Cytotoxicity-guided fractionation of the 80% EtOH extract of Tithonia diversifolia has resulted in the isolation of twelve sesquiterpenoids (1-12), including three new ones (4, 10, 12), and three known flavonoids (13-15). The structures of the new compounds were determined by analysis of their spectroscopic data. The isolated compounds showed cytotoxic activity against HL-60 leukemia cells with IC(50) values ranging from 0.13 to 13.0 microM, when etoposide used as a positive control gave an IC(50) value of 0.43 microM. The cancer growth inhibitory property of 9, the main cytotoxic compound in T. diversifolia, was examined using a disease-oriented panel composed of 39 human cancer cell lines in the Japanese Foundation for Cancer Research.

Poly(N-vinyl-pyrrolidone)-block-poly(D,L-lactide) as polymeric emulsifier for the preparation of biodegradable nanoparticles

Poly(D,L-lactide) (PDLLA) amphiphilic block copolymers were employed as emulsifiers in the preparation of PDLLA nanoparticles by an oil/water emulsion solvent evaporation technique. The surface-active properties of poly(N-vinyl-pyrrolidone)-block-poly(D,L-lactide) (PVP-b-PDLLA) toward the biphasic system were compared to those of polyethylene glycol(PEG)-b-PDLLA of similar composition. PVP-b-PDLLA was found to be a suitable emulsifier for dichloromethane/water emulsions, yielding narrowly distributed nanoparticles (<250 nm) surrounded by a hydrophilic PVP corona. PEG-b-PDLLA, however, was only effective in producing appropriately sized nanoparticles when dichloromethane was replaced with ethyl acetate. Furthermore, the lyoprotectant properties of PVP allowed the freeze-dried nanoparticles to recover their initial size following reconstitution, while PEG-coated nanoparticles could not be redispersed following lyophilization. Two poorly water-soluble drugs, that is, paclitaxel and etoposide, were efficiently loaded into PVP-decorated PDLLA nanoparticles. The entrapment efficiency of etoposide was significantly enhanced by adding MgCl2 to the aqueous phase. It was found that the nanoparticles released the drugs progressively over several days in vitro. The obtained experimental results were corroborated with the theoretical compatibility between a given drug, polymer, and solvent, predicted by total solubility parameters.

The drug loading, cytotoxicty and tumor vascular targeting characteristics of magnetite in magnetic drug targeting

Chemotherapy is a popular treatment approach against cancer but significant uptake of drugs by normal tissues is still a major limitation. Magnetic drug targeting (MDT) has been used to improve localized drug delivery to interstitial tumor targets. MDT is now being developed to improve drug delivery to tumor vessels. We thus seek to understand the role of magnetite (MAG-C) in drug loading, influence on cytotoxicity and vascular targeting characteristics. The inclusion of MAG-C at lower concentrations (0.5 mg/ml) in cationic liposomes did not alter the efficiency of loading etoposide, but at higher concentrations (2.5 mg/ml) incorporation decreased from 80+/-3.4% to 44+/-4.26%. MAG-C reduced the incorporation of dacarbazine. The incorporation was significantly lower compared to liposomal etoposide, both in the presence and absence of MAG-C. The incorporation efficiency of vinblastine sulfate in cationic liposomes was similar for low and relatively high MAG-C content; values for incorporation were 21+/-0.11 and 23+/-2, respectively. Polyethylene-glycol improved the efficiency of loading chemotherapeutic agents regardless of drug type. Additionally, cytotoxicity and tumor vascular targeting characteristics of liposome therapeutics were not influenced by MAG-C. The components used to prepare magnetic liposomes for MDT should be optimized for maximum therapeutic benefit.

Stability and degradation kinetics of etoposide‐loaded parenteral lipid emulsion

Etoposide was incorporated in lipid emulsion to develop an i.v. formulation, and improve its physical and chemical stability without addition of organic solvents, for use as a commercial formulation. High-pressure homogenization was used to prepare the lipid nanospheres and localize the drug at the surfactant layer. The particle size distribution and zeta potential were measured using photon correlation spectroscopy (PCS). Ultrafiltration was used to estimate the relative percentage of etoposide in each phase. The stability profile of etoposide in the lipid emulsion at various temperatures, pH values, and concentrations of drug was monitored by high performance liquid chromatography (HPLC). The degradation pattern of etoposide in lipid emulsion followed pseudo-first-order kinetics. The shelf life (T(90%)) of etoposide in lipid emulsion was estimated to be 47 days at 25 degrees C and it would be stable when stored for 427 days at 4 degrees C, which is a significant improvement compared with a stability of 9.5 days in aqueous solution at 25 degrees C. Etoposide in lipid emulsion and aqueous solution were both most stable at pH 5.0 with a half-life of 54.7 h and 38.6 min at 80 degrees C, respectively. The hydrolysis kinetics of etoposide in lipid emulsion was also shown to be dependent on the drug concentration.

Topoisomerase II - drug interaction domains: identification of substituents on etoposide that interact with the enzyme

Etoposide is one of the most successful chemotherapeutic agents used for the treatment of human cancers. The drug kills cells by inhibiting the ability of topoisomerase II to ligate nucleic acids that it cleaves during the double-stranded DNA passage reaction. Etoposide is composed of a polycyclic ring system (rings A-D), a glycosidic moiety at the C4 position, and a pendent ring (E-ring) at the C1 position. Although drug-enzyme contacts, as opposed to drug-DNA interactions, mediate the entry of etoposide into the topoisomerase II-drug-DNA complex, the substituents on etoposide that interact with the enzyme have not been identified. Therefore, saturation transfer difference [1H]-nuclear magnetic resonance spectroscopy and protein-drug competition binding assays were employed to define the groups on etoposide that associate with yeast topoisomerase II and human topoisomerase IIalpha. Results indicate that the geminal protons of the A-ring, the H5 and H8 protons of the B-ring, and the H2' and H6' protons and the 3'- and 5'-methoxyl protons of the pendent E-ring interact with both enzymes in the binary protein-ligand complexes. In contrast, no significant nuclear Overhauser enhancement signals arising from the C-ring, the D-ring, or the C4 glycosidic moiety were observed with either enzyme, suggesting that there is limited or no contact between these portions of etoposide and topoisomerase II in the binary complex. The functional importance of E-ring substituents was confirmed by topoisomerase II-mediated DNA cleavage assays.

Mutation of cysteine residue 455 to alanine in human topoisomerase IIalpha confers hypersensitivity to quinones: enhancing DNA scission by closing the N-terminal protein gate

Several quinone-based metabolites of industrial and environmental toxins are potent topoisomerase II poisons. These compounds act by adducting the protein, and previous studies suggest that they increase levels of enzyme-associated DNA strand breaks by at least two potential mechanisms. Quinones act directly on the DNA cleavage-ligation equilibrium of topoisomerase II by inhibiting the rate of ligation. They also block the N-terminal gate of the protein, thereby stabilizing topoisomerase II in its "closed clamp" form and trapping DNA in the central annulus of the enzyme. It has been proposed that this latter activity enhances DNA cleavage by increasing the population of enzyme molecules with DNA in their active sites, but a causal relationship has not been established. In order to more fully characterize the mechanistic basis for quinone action against topoisomerase II, the present study characterized the sensitivity of human topoisomerase IIalpha carrying a Cys455-->Ala mutation (top2alphaC455A) toward quinones. Cys455 was identified as a site of quinone adduction by mass spectrometry. The mutant enzyme was approximately 1.5-2-fold hypersensitive to 1,4-benzoquinone and the polychlorinated biphenyl quinone 4'Cl-2,5pQ, but it displayed wild-type sensitivity to traditional topoisomerase II poisons. The ability of 1,4-benzoquinone to inhibit DNA ligation mediated by top2alphaC455A was similar to that of wild-type topoisomerase IIalpha. However, the quinone induced approximately 3 times the level of clamp closure with the mutant enzyme. These findings strongly support the hypothesis that the ability of quinones to block the N-terminal gate of the type II enzyme contributes to their actions as topoisomerase II poisons.

Electrochemical Study of the Antineoplastic Agent Etoposide at Carbon Paste Electrode and Its Determination in Spiked Human Serum by Differential Pulse Voltammetry

The electrochemical oxidation of the antineoplastic agent etoposide was studied at carbon paste electrode in Britton-Robinson buffer solutions over the pH range 2.0-10.0 using cyclic, linear sweep and differential pulse voltammetry. Oxidation of the drug was effected in a single reversible, diffusion-controlled step within the pH range 2.0-4.0, a second oxidation process was produced above pH 4.0. Using differential pulse voltammetry (DPV), the drug yielded a well-defined voltammetric response in Britton-Robinson buffer, pH 3.0 at 0.500 V (vs. Ag/AgCl) on carbon paste electrode. This process could be used to determine etoposide concentrations in the range 2.5 x 10(-7) to 2.5 x 10(-5) M with a detection limit of 1.0 x 10(-7) M. The method was successfully applied to the determination of the drug in spiked human serum.

Characterization of an Etoposide-Glutathione Conjugate Derived from Metabolic Activation by Human Cytochrome P450

Etoposide (VP-16), a DNA topoisomerase II poison widely used as an antineoplastic agent is also known to cause leukemia. One of its major metabolic pathways involves O-demethylation to etoposide catechol (etoposide-OH) by cytochrome P450 3A4 (CYP3A4). The catechol metabolite can undergo sequential one- and two-electron oxidations to form etoposide semi-quinone (etoposide-SQ) and etoposide quinone (etoposide-Q), respectively, which have both been implicated as cytotoxic metabolites. However, etoposide-Q is known to react with glutathione (GSH), which can protect DNA from oxidative damage by this reactive metabolite. In this study, etoposide-Q was reacted with GSH and the two etoposide-GSH conjugates were characterized. The major conjugate was etoposide-OH-6'-SG and the minor product was etoposide-OH-2'-SG. Etoposide-OH-6'-SG, which arose from Michael addition of GSH to etoposide-Q, was characterized by mass spectrometry and 2-D NMR. It was identified as the sole product from in vitro metabolism experiments using recombinant human CYP3A4 or liver microsomes incubated with etoposide in the presence of GSH. Etoposide-OH-6'-SG was also detected from incubations of etoposide-OH and GSH alone. Therefore, the presence of etoposide-OH, which can be formed from etoposide metabolism by CYP3A4, is essential for formation of the GSH conjugate. The oxidation of etoposide-OH to a quinone intermediate is likely the precursor in the formation of etoposide-OH-6'-SG.

[Studies on the electron transfer between etoposide (VP-16) and DNA]

In the present study, the electron transfer between Etoposide (VP-16) and GMP or DNA was investigated using pulse radiolysis and circular dichroism technology. The electron transfer between VP-16 and GMP was found, and the reaction rate constant was determined as 3.16 x 10(7) L x mol(-1) x s(-1) by pulse radiolysis. The authors found the interaction of VP-16 and DNA using the technology of circular dichroism. This study has provided theoretical reference for further study on the anti-tumor mechanism of VP-16.

Cdc7 is an active kinase in human cancer cells undergoing replication stress

Cdc7 kinase promotes and regulates DNA replication in eukaryotic organisms. Multiple mechanisms modulating kinase activity in response to DNA replication stress have been reported, supporting the opposing notions that Cdc7 either plays an active role under these conditions or, conversely, is a final target inactivated by a checkpoint response. We have developed new immnunological reagents to study the properties of human Cdc7 kinase in cells challenged with the ribonucleotide reductase inhibitor hydroxyurea or with the DNA topoisomerase II inhibitor etoposide. We show that Cdc7.Dbf4 and Cdc7.Drf1 complexes are stable and active in multiple cell lines upon drug treatment, with Cdc7.Dbf4 accumulating on chromatin-enriched fractions. Cdc7 depletion by small interfering RNA in hydroxyurea and etoposide impairs hyper-phosphorylation of Mcm2 at specific Cdc7-dependent phosphorylation sites and drug-induced hyper-phosphorylation of chromatin-bound Mcm4. Furthermore, sustained inhibition of Cdc7 in the presence of these drugs increases cell death supporting the notion that the Cdc7 kinase plays a role in maintaining cell viability during replication stress.

Leaching of diethylhexyl phthalate from polyvinyl chloride materials into etoposide intravenous solutions

Etoposide intravenous solution is associated with leaching of diethylhexyl phthalate (DEHP) from bags and tubings made from polyvinyl chloride (PVC). Recent evidence suggests that this may be more substantial than previously found. Since DEHP is potentially hepatotoxic and carcinogenic, it is preferable to prepare and administer etoposide bags and tubings made from non-PVC materials.

Myeloperoxidase-Catalyzed Metabolism of Etoposide to Its Quinone and Glutathione Adduct Forms in HL60 Cells

Etoposide is a widely used antineoplastic agent that has provided great success in the treatment of childhood leukemias and other malignancies. Unfortunately, its use is associated with the increased risk of development of secondary acute myelogenous leukemias involving translocations at the MLL gene in chromosome band 11q23. Previous studies showed that the phenoxyl radical of etoposide can be generated by myeloperoxidase (MPO), an enzyme prevalent in myeloid progenitor cells that can derive myelogenous leukemias. Disproportionation of this radical leads to formation of the redox active etoposide ortho-quinone metabolite. We hypothesized that etoposide ortho-quinone could therefore form in myeloid progenitor cells and might be a contributor to the development of treatment-related secondary leukemias. Etoposide ortho-quinone is an inherently unstable compound and readily reacts with glutathione in aqueous media without any requirement for catalytic assistance from glutathione S-transferase. We looked for the presence of its glutathione adduct as an indicator of etoposide ortho-quinone in cells. MPO-expressing human myeloid leukemia HL60 cells were treated with etoposide for 0.5 h in the presence and absence of the cosubstrate of MPO, hydrogen peroxide. Cell lysates and medium were analyzed by LC-ESI-ion trap-MS and MS/MS, which yielded clear evidence of the intracellular formation of the etoposide ortho-quinone-glutathione adduct. A stable isotope-labeled form of the GSH adduct was synthesized and employed as an isotope dilution internal standard in LC-ESI-quadrupole-MS analyses. The glutathione adduct level was dependent on the concentration of etoposide added to the cells. More importantly, the formation of the glutathione adduct was significantly suppressed by the pretreatment of HL60 cells with the heme synthesis inhibitor succinylacetone (p < 0.001), which resulted in a decreased level and activity of MPO. These results are consistent with the idea that MPO is responsible for the conversion of etoposide to its ortho-quinone in these cells.

Etoposide nanocarriers suppress glioma cell growth by intracellular drug delivery and simultaneous P-glycoprotein inhibition

In cancer treatment, efficient therapeutic strategies could be impeded by cellular mechanisms such as the multidrug resistance. Recently, drug-loaded nanoparticles have been reported to be useful, since they allow entering the cancer cell and act as an intracellular anti-cancer drug reservoir. A new approach is proposed here by the use of lipid nanocapsules (LNC) which were hypothesized to reverse multidrug resistance additionally by their P-glycoprotein (P-gp) inhibiting surfactant. LNC (mean diameter 25 to 100 nm) were loaded with etoposide, tested for the drug release and their efficiency to reduce cell growth in cell culture for C6, F98, and 9L glioma cell lines. Sustained etoposide release can be provided over a period of 1 week (t10%: 1.4+/-0.1h; t50%: 15.9+/-2.8h). The P-gp inhibiting activity in-vitro was found to be independent from the LNC size. In cell culture, an internalization of LNC was observed in all glioma cell types. Etoposide LNC showed a generally higher efficiency than the drug solution while blank LNC were found to be less inhibitory than the pure drug at equivalent concentrations (IC50: C6: etoposide: 25.2 microM; LNC: 2.6-8.9 microM, F98: etoposide: 46.5 microM; LNC: 1.4-14.7 microM, 9L: etoposide: 58.2 microM; LNC: 4.4-12.7 microM). This effect was found to be particle size dependent within a range of an 8- (C6) to 33-fold (F98) increased cytotoxicity for smallest particles. When cells were incubated with etoposide solution in the presence of blank LNC, a slight growth inhibition was observed, however, distinctly lower than the drug-trapping particles. Moreover, cell toxicity on astrocytes was similar for etoposide LNC and etoposide solution. The mechanism of action of etoposide LNC was proposed to be a cell uptake followed by a sustained drug release from the LNC in combination with an intracellular P-gp inhibition ensuring a higher anticancer drug concentration inside the cancer cells.

Pharmacokinetics and tissue distribution of etoposide delivered in long circulating parenteral emulsion

PURPOSE

The aim of the study is to ascertain the influence of pegylation of parenteral emulsion (PE) on their long circulating property.

METHODS

Etoposide encapsulated parenteral emulsion (EPE) was prepared using soybean oil, egg lecithin and cholesterol. Etoposide encapsulated long circulating parenteral emulsion (PEG-EPE) was prepared using PEG (2000)-DSPE as a stealth agent. The effect of monovalent and divalent electrolytes on the stability of EP was assessed by measuring the fixed aqueous layer thickness (FALT) and flocculation rate. Pharmacokinetics and tissue distribution pattern of PE following i.v. (bolus) were assessed in Wistar rats and Swiss albino mice.

RESULTS

FALT of PEG-EPE was larger than that of EPE. In case of PEG-EPE, as the concentration of pegylated lipid (PEG) increased from 0.15 to 0.45% w/v the flocculation rate decreased asymptomatically in the presence of monovalent and divalent electrolytes. The increased circulation time of PEG-EPE (0.3%) after intravenous injection to rats confirms the presence of FALT around globules. PEG-EPE showed improved pharmacokinetic parameters with 5.5 times higher AUC than etoposide commercial formulation (ETP). Tissue distribution results show that etoposide levels in all tissues except in brain and heart were lower in case of PEG-EPE than ETP. The percentage of tumor growth suppression rate (%T/C) in Lewis lung carcinoma bearing mice was 63.23, 62.83 and 33.78% in EPE, PEG-EPE and ETP treated mice, respectively. The improved activity of PEG-EPE is due to enhanced permeability and retention effect (EPR).

CONCLUSION

Encapsulation of etoposide in PEG-coated PE produced improved pharmacokinetic profile than that of EPE and ETP.

Etoposide, topoisomerase II and cancer

Etoposide is an important chemotherapeutic agent that is used to treat a wide spectrum of human cancers. It has been in clinical use for more than two decades and remains one of the most highly prescribed anticancer drugs in the world. The primary cytotoxic target for etoposide is topoisomerase II. This ubiquitous enzyme regulates DNA under- and overwinding, and removes knots and tangles from the genome by generating transient double-stranded breaks in the double helix. Etoposide kills cells by stabilizing a covalent enzyme-cleaved DNA complex (known as the cleavage complex) that is a transient intermediate in the catalytic cycle of topoisomerase II. The accumulation of cleavage complexes in treated cells leads to the generation of permanent DNA strand breaks, which trigger recombination/repair pathways, mutagenesis, and chromosomal translocations. If these breaks overwhelm the cell, they can initiate death pathways. Thus, etoposide converts topoisomerase II from an essential enzyme to a potent cellular toxin that fragments the genome. Although the topoisomerase II-DNA cleavage complex is an important target for cancer chemotherapy, there also is evidence that topoisomerase II-mediated DNA strand breaks induced by etoposide and other agents can trigger chromosomal translocations that lead to specific types of leukemia. Given the central role of topoisomerase II in both the cure and initiation of human cancers, it is imperative to further understand the mechanism by which the enzyme cleaves and rejoins the double helix and the process by which etoposide and other anticancer drugs alter topoisomerase II function.

Effect of Particle Size of Nanospheres and Microspheres on the Cellular-Association and Cytotoxicity of Paclitaxel in 4T1 Cells

PURPOSE

To compare the effect of size of delivery systems on the cell-association and in vitro cytotoxicity of paclitaxel.

METHODS

Four sizes of PLGA-paclitaxel particles were prepared to study the effect of particle size on the cell-association of paclitaxel in 4T1 monolayer in the presence, and absence, of BCRP inhibitor, endocytic inhibitor, and P-glycoprotein (P-gp) inhibitor. Paclitaxel cell-association studies were repeated in Caco-2, Cor-L23/R, and bovine brain microvessel endothelial cells (BBMECs), as well as the association of etoposide in 4T1 cells. Cytotoxicity of paclitaxel to 4T1 cells delivered in nanospheres was compared to microspheres.

RESULTS

The concentration of paclitaxel and etoposide associated with 4T1 cells was 4.8 and 29 times greater, respectively, as the size increased from 310 to 2077 nm. Paclitaxel association consistently increased in Caco-2 and Cor-L23/R as the size of the delivery system increased. The endocytic inhibitor, 2-deoxyglucose, significantly decreased the cellular paclitaxel association when delivered by nanospheres but not microspheres. Consistent with the cell-association results, paclitaxel was thrice more cytotoxic to 4T1 cells when delivered in microspheres.

CONCLUSIONS

Cell-association of paclitaxel increased in 4T1, Caco-2, and Cor-L23/R as particle size increased. Paclitaxel delivered from 1-mum microspheres was thrice more cytotoxic to 4T1 cells compared to the drug delivered from nanospheres or solution.

DNA lesion-specific co-localization of the Mre11/Rad50/Nbs1 (MRN) complex and replication protein A (RPA) to repair foci

The DNA damage response, triggered by DNA replication stress or DNA damage, involves the activation of DNA repair and cell cycle regulatory proteins including the MRN (Mre11, Rad50, and Nbs1) complex and replication protein A (RPA). The induction of replication stress by hydroxyurea (HU) or DNA damage by camptothecin (CAMPT), etoposide (ETOP), or mitomycin C (MMC) led to the formation of nuclear foci containing phosphorylated Nbs1. HU and CAMPT treatment also led to the formation of RPA foci that co-localized with phospho-Nbs1 foci. After ETOP treatment, phospho-Nbs1 and RPA foci were detected but not within the same cell. MMC treatment resulted in phospho-Nbs1 foci formation in the absence of RPA foci. Consistent with the presence or absence of RPA foci, RPA hyperphosphorylation was present following HU, CAMPT, and ETOP treatment but absent following MMC treatment. The lack of co-localization of phospho-Nbs1 and RPA foci may be due to relatively shorter stretches of single-stranded DNA generated following ETOP and MMC treatment. These data suggest that, even though the MRN complex and RPA can interact, their interaction may be limited to responses to specific types of lesions, particularly those that have longer stretches of single-stranded DNA. In addition, the consistent formation of phospho-Nbs1 foci in all of the treatment groups suggests that the MRN complex may play a more universal role in the recognition and response to DNA lesions of all types, whereas the role of RPA may be limited to certain subsets of lesions.

Etoposide: discovery and medicinal chemistry

Etoposide is an antitumor agent currently in clinical use for the treatment of small cell lung cancer, testicular cancer and lymphomas. Since the introduction of etoposide in 1971, its mechanism of action and potent antineoplastic activity has served as the impetus for intensive research activities in chemistry and biology. This drug acts by stabilizing a normally transient DNA-topoisomerase II complex, thus increasing the concentration of double-stranded DNA breaks. This phenomenon triggers mutagenic and cell death pathways. The function of topoisomerase II is understood in some detail, as is the mechanism of inhibition of etoposide at a molecular level. Etoposide has shortcomings of limited neoplastic activity against several solid tumors such as non-small cell lung cancer, cross-resistance to MDR tumor cell lines and low bioavailability. The design and synthesis of etoposide analogs is an activity of fundamental interest to the field of cancer chemotherapy. In the first part, this article is a survey of the discovery of etoposide, the DNA topoisomerase II structure and mechanism, and the models for drug-enzyme interaction. The last part is concerned with the search for new etoposide analogs based upon an empirical design.

Antitumor agents. Part 235: Novel 4'-ester etoposide analogues as potent DNA topoisomerase II inhibitors with improved therapeutic potential

Eight 4'-ester epipodophyllotoxin derivatives (9-16) were designed and synthesized with the aim to overcome drug-resistance and improve water-solubility simultaneously. These compounds were superior to etoposide (1) in causing cellular protein-linked DNA breaks and inhibiting KB and 1-resistant KB-7d cell replication. Compounds 9 and 10 showed significant inhibitory activity against DNA topoisomerase II in vitro. Compound 10 also exhibited an in vitro DNA cleavage pattern similar to that of GL-331 (5). A hypothetical model on the action mode of 1-analogues is proposed based on the results.