Stereochemistry of intercalation: interaction of daunomycin with DNA

Doxorubicin-loaded polymeric nanoparticles containing ketoester-based block and cholesterol moiety as specific vehicles to fight estrogen-dependent breast cancer

The presented research concerns the preparation of polymer nanoparticles (PNPs) for the delivery of doxorubicin. Several block and statistical copolymers, composed of ketoester derivative, N-isopropylacrylamide, and cholesterol, were synthesized. In the nanoprecipitation process, doxorubicin (DOX) molecules were kept in spatial polymeric systems. DOX-loaded PNPs show high efficacy against estrogen-dependent MCF-7 breast cancer cell lines despite low doses of DOX applied and good compatibility with normal cells. Research confirms the effect of PNPs on the degradation of the biological membrane, and the accumulation of reactive oxygen species (ROS), and the ability to cell cycle arrest are strictly linked to cell death.

Graphical Abstract

Interaction of an anticancer benzopyrane derivative with DNA: Biophysical, biochemical, and molecular modeling studies

BACKGROUND

SIMR1281 is a potent anticancer lead candidate with multi- target activity against several proteins; however, its mechanism of action at the molecular level is not fully understood. Revealing the mechanism and the origin of multitarget activity is important for the rational identification and optimization of multitarget drugs.

METHODS

We have used a variety of biophysical (circular dichroism, isothermal titration calorimetry, viscosity, and UV DNA melting), biochemical (topoisomerase I & II assays) and computational (molecular docking and MD simulations) methods to study the interaction of SIMR1281 with duplex DNA structures.

RESULTS

The biophysical results revealed that SIMR1281 binds to dsDNA via an intercalation-binding mode with an average binding constant of 3.1 × 10⁶ M^-1. This binding mode was confirmed by the topoisomerases' inhibition assays and molecular modeling simulations, which showed the intercalation of the benzopyrane moiety between DNA base pairs, while the remaining moieties (thiazole and phenyl rings) sit in the minor groove and interact with the flanking base pairs adjacent to the intercalation site.

CONCLUSIONS

The DNA binding characteristics of SIMR1281, which can disrupt/inhibit DNA function as confirmed by the topoisomerases' inhibition assays, indicate that the observed multi-target activity might originate from ligand intervention at nucleic acids level rather than due to direct interactions with multiple biological targets at the protein level.

GENERAL SIGNIFICANCE

The findings of this study could be helpful to guide future optimization of benzopyrane-based ligands for therapeutic purposes.

Synergistic Effect Evaluation of Magnetotherapy and a Cationic-Magnetic Nanocomposite Loaded with Doxorubicin for Targeted Drug Delivery to Breast Adenocarcinoma

This work investigates the synergistic effect of magnetotherapy and a novel cationic-magnetic drug delivery system on inhibiting breast cancer cell growth and other tissues. First, super-paramagnetic magnetite (Fe₃O₄) nanoparticles were coated with doxorubicin-imprinted poly(methacrylic acid-co-diallyl dimethylammonium chloride) [Fe₃O₄/poly(MAA-DDA)]. The cationic-magnetic nanocomposite (CMC) was characterized using XRD, FT-IR, VSM, TGA, TEM, FESEM, EDS, DLS, and BET. In vitro analyses, including drug release kinetics, cytotoxicity, and hemolytic assays, confirmed this novel CMC's good drug release profile and biocompatibility. Finally, in vivo experiments on BALB/c mice were designed to evaluate the synergistic effect of magnetotherapy on targeted drug delivery using the CMC. In vivo fluorescence imaging evaluated the drug distribution in different tissues of mice. Tumor volume evaluation demonstrated the efficiency of the CMC and magnetotherapy in preventing tumor growth; the two techniques significantly reduced tumor volume. Histopathological analysis proved that applying magnetotherapy in conjunction with the cationic-magnetic drug delivery system significantly prevented tumor cell proliferation and increased apoptosis with limited impact on other tissues. Also, Dox and Fe concentrations in different tissues confirmed the efficient drug delivery to tumor cells.

The Achilles' heel of cancer: targeting tumors via lysosome-induced immunogenic cell death

Interest in the lysosome's potential role in anticancer therapies has recently been appreciated in the field of immuno-oncology. Targeting lysosomes triggers apoptotic pathways, inhibits cytoprotective autophagy, and activates a unique form of apoptosis known as immunogenic cell death (ICD). This mechanism stimulates a local and systemic immune response against dead-cell antigens. Stressors that can lead to ICD include an abundance of ROS which induce lysosome membrane permeability (LMP). Dying cells express markers that activate immune cells. Dendritic cells engulf the dying cell and then present the cell's neoantigens to T cells. The discovery of ICD-inducing agents is important due to their potential to trigger autoimmunity. In this review, we discuss the various mechanisms of activating lysosome-induced cell death in cancer cells specifically and the strategies that current laboratories are using to selectively promote LMP in tumors.

The Critical Role of 12-Methyl Group of Anthracycline Dutomycin to Its Antiproliferative Activity

Anthracycline dutomycin is a tetracyclic quinone glycoside produced by Streptomyces minoensis NRRL B-5482. SW91 is a C-12 demethylated dutomycin derivative, which was identified in our previous research. In vitro cytotoxicity and apoptosis assays of these two compounds were conducted to demonstrate their antiproliferation activities. The results showed that both dutomycin and SW91 block cells at the S phase, whereas dutomycin shows more significant inhibition of cell growth. Their interactions with calf thymus DNA (CT-DNA) were investigated, with dutomycin exhibiting higher binding affinity. The molecular docking demonstrated that the 12-methyl group makes dutomycin attach to the groove of DNA. These findings suggest that dutomycin has binding higher affinity to DNA and impairs DNA replication resulting in more significant antitumor activity.

Applications of Mesoporous Silica-Encapsulated Gold Nanorods Loaded Doxorubicin in Chemo-photothermal Therapy

We investigate the chemo-photothermal effects of gold nanorods (GNRs) coated using mesoporous silica (mSiO₂) loading doxorubicin (DOX). When the mesoporous silica layer is embedded by doxorubicin drugs, a significant change in absorption spectra enables to quantify the drug loading. We carried out photothermal experiments on saline and livers of mice having GNRs@mSiO₂ and GNRs@mSiO₂-DOX. We also injected the gold nanostructures into many tumor-implanted mice and used laser illumination on some of them. By measuring the weight and size of tumors, the distinct efficiency of photothermal therapy and chemotherapy on treatment is determined. We experimentally confirm the accumulation of gold nanostructures in the liver.

Phenanthridine derivatives as promising new anticancer agents: synthesis, biological evaluation and binding studies

Aim: Phenanthridines are an essential class of nitrogenous heterocycles with extensive applications in medicinal chemistry. The development of efficient and eco-friendly methods for the preparation of chirally pure dihydropyrrolo[1,2-f]phenanthridines (5a-h), and their in vitro evaluation and modeling studies as potential anticancer, antioxidant and DNA cleavage agents is reported. Methodology & results: Compounds 5a-h were prepared through a facile one-pot synthesis and characterized by infrared, high resolution mass spectrometry, ¹H and ¹³C nuclear magnetic resonance. The molecules were subjected to virtual screening and docking analysis against selected human molecular targets. Compound 5g displayed good binding properties as well as significant anticancer and DNA cleavage activity. Conclusion: Compound 5g has been identified as a potential lead candidate for further testing against additional cancer cell lines and animal models in future.

Encapsulation of anticancer drug doxorubicin inside dendritic macromolecular cavities: First-principles benchmarks

By using first-principles approaches based on Density Functional Theory, we explore the possibility of using dendritic macromolecular structures as carriers of the doxorubicin anticancer drug. In particular, we consider macromolecular cavities of different sizes composed of phenylene-, thiophene-, phenyl-cored thiophen- and thioazole-based dendrimers. The comparison between the optimized molecular geometries of the monomers and of the host-guest complexes reveals that only slight structural changes are observed in doxorubicin upon complexation. Also, the encapsulation energies for the host-guest complexes suggest that these systems are of potential use for pharmacology applications in vivo. The interaction of the guest doxorubicin with the macromolecular cavities exploits different types of weak intermolecular forces including σ, π and hydrogen bond interactions. The electronic structure of these complexes is discussed, with particular emphasis placed on the role of the charge distribution and the nature of the frontier molecular orbitals in the encapsulation process. Spectroscopic properties of these complexes are derived to facilitate their detection in laboratory and in vivo. These include IR vibrational frequencies, absorption wavelengths and relative oscillator strengths for the main transitions in the UV-Vis spectrum.

Interaction of anthraquinones of Cassia occidentalis seeds with DNA and Glutathione

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Emodin has the maximum binding affinity to calf thymus DNA.

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Anthraquinones form GSH conjugates.

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Anthraquinones oxidizes GSH to GSSG.

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Cytotoxicity of anthraquinones are linked to their DNA binding affinity.

Consumption of Cassia occidentalis (CO) seeds has been associated with the hepatomyoencephalopathy (HME) in children. Recently, we have characterized the toxic anthraquinones (AQs) such as Emodin, Rhein, Aloe-emodin, Chrysophanol and Physcion in CO seeds and detected these moieties in the bio fluids of CO poisoning cases. As AQs were detected in the serum of HME patients, their interaction with key biomolecules including protein, DNA and glutathione (GSH) is imperative. In this regard, we have previously reported the interaction of these AQs with serum albumin protein and their subsequent biological effects. However, the interaction of these AQs with DNA and GSH remained unexplored. In the present work, we have studied the binding of these AQs of CO seeds with DNA and GSH by fluorescence spectroscopy, UV–vis spectral analysis, molecular docking, and biochemical studies. Results indicated a higher binding affinity for Emodin (K_a = 3.854 × 10⁴ L mol⁻¹ S⁻¹), Aloe-emodin (K_a = 0.961 × 10⁴ L mol⁻¹ S⁻¹) and Rhein (K_a = 0.034 × 10⁴ L mol⁻¹ S⁻¹) towards calf thymus DNA may be associated with their higher cytotoxicity. Alternatively, Physcion and Chrysophanol which showed less cytotoxicity in our earlier studies exhibited very low DNA binding. The binding pattern of all these AQs is consistent with the in-silico data. Absorption spectroscopy studies indicated the possible formation of GSH conjugate with Aloe-emodin and Physcion. Further biochemical measurement of GSH and GSSG (Glutathione disulfide) following incubation with AQs indicated that Aloe-emodin (28%) and Rhein (30%) oxidizes GSH to GSSG more as compared to other AQs. Taken together, these results suggest that the higher cytotoxicity of Rhein, Emodin and Aloe-emodin may be attributed to their potent DNA and GSH binding affinity.

Insight into the Mechanism of Action of Marine Cytotoxic Thiazinoquinones

The electrochemical response of four natural cytotoxic thiazinoquinones isolated from the Aplidium species was studied using conventional solution-phase and solid-state techniques, based on the voltammetry of immobilized particles methodology. The interaction with O₂ and electrochemically generated reactive oxygen species (ROS) was electrochemically monitored. At the same time, a molecular modeling study including density functional theory (DFT) calculations was performed in order to analyze the conformational and electronic properties of the natural thiazinoquinones, as well as those of their reduced intermediates. The obtained electrochemical and computational results were analyzed and correlated to cytotoxic activity of these compounds, highlighting some features possibly related to their mechanism of action.

Doxorubicin: Comparison between 3-h continuous and bolus intravenous administration paradigms on cardio-renal axis, mitochondrial sphingolipids and pathology

Doxorubicin (DOX) is a potent and effective broad-spectrum anthracycline antitumor agent, but its clinical usefulness is restricted by cardiotoxicity. This study compared pharmacokinetic, functional, structural and biochemical effects of single dose DOX bolus or 3-h continuous iv infusion (3-h iv) in the Han–Wistar rat to characterize possible treatment-related differences in drug safety over a 72 h observation period. Both DOX dosing paradigms significantly altered blood pressure, core body temperature and QA interval (indirect measure of cardiac contractility); however, there was no recovery observed in the bolus iv treatment group. Following the 3-h iv treatment, blood pressures and QA interval normalized by 36 h then rose above baseline levels over 72 h. Both treatments induced biphasic changes in heart rate with initial increases followed by sustained decreases. Cardiac injury biomarkers in plasma were elevated only in the bolus iv treatment group. Tissue cardiac injury biomarkers, cardiac mitochondrial complexes I, III and V and cardiac mitochondrial sphingolipids were decreased only in the bolus iv treatment group. Results indicate that each DOX dosing paradigm deregulates sinus rhythm.However, slowing the rate of infusion allows for functional compensation of blood pressure and may decrease the likelihood of cardiac myocyte necrosis via a mechanism associated with reduced mitochondrial damage.

Synthesis of marmycin A and investigation into its cellular activity

Anthracyclines such as doxorubicin are used extensively in the treatment of cancers. Anthraquinone-related angucyclines also exhibit antiproliferative properties and have been proposed to operate via similar mechanisms, including direct genome targeting. Here, we report the chemical synthesis of marmycin A and the study of its cellular activity. The aromatic core was constructed by means of a one-pot multistep reaction comprising a regioselective Diels-Alder cycloaddition, and the complex sugar backbone was introduced through a copper-catalysed Ullmann cross-coupling, followed by a challenging Friedel-Crafts cyclization. Remarkably, fluorescence microscopy revealed that marmycin A does not target the nucleus but instead accumulates in lysosomes, thereby promoting cell death independently of genome targeting. Furthermore, a synthetic dimer of marmycin A and the lysosome-targeting agent artesunate exhibited a synergistic activity against the invasive MDA-MB-231 cancer cell line. These findings shed light on the elusive pathways through which anthraquinone derivatives act in cells, pointing towards unanticipated biological and therapeutic applications.

Design and synthesis of novel isoxazole tethered quinone-amino Acid hybrids

A new series of isoxazole tethered quinone-amino acid hybrids has been designed and synthesized involving 1,3-dipolar cycloaddition reaction followed by an oxidation reaction using cerium ammonium nitrate (CAN). Using this method, for the first time various isoxazole tethered quinone-phenyl alanine and quinone-alanine hybrids were synthesized from simple commercially available 4-bromobenzyl bromide, propargyl bromide, and 2,5-dimethoxybenzaldehyde in good yield.

DNA origami as an in vivo drug delivery vehicle for cancer therapy

Many chemotherapeutics used for cancer treatments encounter issues during delivery to tumors in vivo and may have high levels of systemic toxicity due to their nonspecific distribution. Various materials have been explored to fabricate nanoparticles as drug carriers to improve delivery efficiency. However, most of these materials suffer from multiple drawbacks, such as limited biocompatibility and inability to engineer spatially addressable surfaces that can be utilized for multifunctional activity. Here, we demonstrate that DNA origami possessed enhanced tumor passive targeting and long-lasting properties at the tumor region. Particularly, the triangle-shaped DNA origami exhibits optimal tumor passive targeting accumulation. The delivery of the known anticancer drug doxorubicin into tumors by self-assembled DNA origami nanostructures was performed, and this approach showed prominent therapeutic efficacy in vivo. The DNA origami carriers were prepared through the self-assembly of M13mp18 phage DNA and hundreds of complementary DNA helper strands; the doxorubicin was subsequently noncovalently intercalated into these nanostructures. After conducting fluorescence imaging and safety evaluation, the doxorubicin-containing DNA origami exhibited remarkable antitumor efficacy without observable systemic toxicity in nude mice bearing orthotopic breast tumors labeled with green fluorescent protein. Our results demonstrated the potential of DNA origami nanostructures as innovative platforms for the efficient and safe drug delivery of cancer therapeutics in vivo.

Synthesis and evaluation as antitumor agents of 1,4-naphthohydroquinone derivatives conjugated with amino acids and purines

We report on the synthesis of two series of 1,4-naphthohydroquinone derivatives conjugated with amino acids (Gly, Ala, Phe, and Glu) and with substituted purines linked by an aliphatic chain. The compounds were obtained through Diels-Alder cycloaddition between myrcene and 1,4-benzoquinone and evaluated in vitro for their cytotoxicity (GI50 ) against cultured human cancer cells of A-549 lung carcinoma, HT-29 colon adenocarcinoma, and MCF-7 breast carcinoma. The GI50 values found for some hydroquinone-amino acid and hydroquinone-purine hybrids against MCF-7 are in an activity range comparable to that of the reference drug doxorubicin.

Amrubicin: potential in combination with cisplatin or carboplatin to treat small-cell lung cancer

Small-cell lung cancer (SCLC) is the most aggressive form of lung cancer characterized by early metastasis and high mortality. In recent years, monotherapy and combination therapy of amrubicin with cisplatin or carboplatin has been actively studied and shown promise for the treatment of extensive disease SCLC (ED-SCLC). In this article, we summarize clinical trials of both monotherapy and combination therapy with amrubicin conducted in Japan, the USA, and the European Union. The results suggest that the clinical outcome of amrubicin therapy may be associated with genetic variations in patients. Further study of combination regimens in patients of different ethnicities is warranted.

pH-responsive delivery of doxorubicin from citrate-apatite nanocrystals with tailored carbonate content

In this work, the efficiency of bioinspired citrate-functionalized nanocrystalline apatites as nanocarriers for delivery of doxorubicin (DOXO) has been assessed. The nanoparticles were synthesized by thermal decomplexing of metastable calcium/citrate/phosphate solutions both in the absence (Ap) and in the presence (cAp) of carbonate ions. The presence of citrate and carbonate ions in the solution allowed us to tailor the size, shape, carbonate content, and surface chemistry of the nanoparticles. The drug-loading efficiency of the two types of apatite was evaluated by means of the adsorption isotherms, which were found to fit a Langmuir-Freundlich behavior. A model describing the interaction between apatite surface and DOXO is proposed from adsorption isotherms and ζ-potential measurements. DOXO is adsorbed as a dimer by means of a positively charged amino group that electrostatically interacts with negatively charged surface groups of nanoparticles. The drug-release profiles were explored at pHs 7.4 and 5.0, mimicking the physiological pH in the blood circulation and the more acidic pH in the endosome-lysosome intracellular compartment, respectively. After 7 days at pH 7.4, cAp-DOXO released around 42% less drug than Ap-DOXO. However, at acidic pH, both nanoassemblies released similar amounts of DOXO. In vitro assays analyzed by confocal microscopy showed that both drug-loaded apatites were internalized within GTL-16 human carcinoma cells and could release DOXO, which accumulated in the nucleus in short times and exerted cytotoxic activity with the same efficiency. cAp are thus expected to be a more promising nanocarrier for experiments in vivo, in situations where intravenous injection of nanoparticles are required to reach the targeted tumor, after circulating in the bloodstream.

The clinically relevant pharmacogenomic changes in acute myelogenous leukemia

Acute myelogenous leukemia (AML) is an extremely heterogeneous neoplasm with several clinical, pathological, genetic and molecular subtypes. Combinations of various doses and schedules of cytarabine and different anthracyclines have been the mainstay of treatment for all forms of AMLs in adult patients. Although this combination, with the addition of an occasional third agent, remains effective for treatment of some young-adult patients with de novo AML, the prognosis of AML secondary to myelodysplastic syndromes or myeloproliferative neoplasms, treatment-related AML, relapsed or refractory AML, and AML that occurs in older populations remains grim. Taken into account the heterogeneity of AML, one size does not and should not be tried to fit all. In this article, the authors review currently understood, applicable and relevant findings related to cytarabine and anthracycline drug-metabolizing enzymes and drug transporters in adult patients with AML. To provide a prime-time example of clinical applicability of pharmacogenomics in distinguishing a subset of patients with AML who might be better responders to farnesyltransferase inhibitors, the authors also reviewed findings related to a two-gene transcript signature consisting of high RASGRP1 and low APTX, the ratio of which appears to positively predict clinical response in AML patients treated with farnesyltransferase inhibitors.

Oxidative stress, redox signaling, and metal chelation in anthracycline cardiotoxicity and pharmacological cardioprotection

SIGNIFICANCE

Anthracyclines (doxorubicin, daunorubicin, or epirubicin) rank among the most effective anticancer drugs, but their clinical usefulness is hampered by the risk of cardiotoxicity. The most feared are the chronic forms of cardiotoxicity, characterized by irreversible cardiac damage and congestive heart failure. Although the pathogenesis of anthracycline cardiotoxicity seems to be complex, the pivotal role has been traditionally attributed to the iron-mediated formation of reactive oxygen species (ROS). In clinics, the bisdioxopiperazine agent dexrazoxane (ICRF-187) reduces the risk of anthracycline cardiotoxicity without a significant effect on response to chemotherapy. The prevailing concept describes dexrazoxane as a prodrug undergoing bioactivation to an iron-chelating agent ADR-925, which may inhibit anthracycline-induced ROS formation and oxidative damage to cardiomyocytes.

RECENT ADVANCES

A considerable body of evidence points to mitochondria as the key targets for anthracycline cardiotoxicity, and therefore it could be also crucial for effective cardioprotection. Numerous antioxidants and several iron chelators have been tested in vitro and in vivo with variable outcomes. None of these compounds have matched or even surpassed the effectiveness of dexrazoxane in chronic anthracycline cardiotoxicity settings, despite being stronger chelators and/or antioxidants.

CRITICAL ISSUES

The interpretation of many findings is complicated by the heterogeneity of experimental models and frequent employment of acute high-dose treatments with limited translatability to clinical practice.

FUTURE DIRECTIONS

Dexrazoxane may be the key to the enigma of anthracycline cardiotoxicity, and therefore it warrants further investigation, including the search for alternative/complementary modes of cardioprotective action beyond simple iron chelation.

Novel Cholesteric Phase in Dispersions of Nucleic Acids due to Polymeric Chelate Bridges

Physics, Moscow, RussiaWe consider cholesteric liquid-crystalline DNA dispersions, and show thatpolymeric (Dau-Cu) complexes, the so-called bridges, between pairs of DNA molecules may generate a super liquid-crystalline structure (BR-phase), charachterized by a soliton lattice of the spatial distribution of theorder parameter. The BR-phase could have a layered spatial structure andan abnormal optical activity that could have a bearing upon the intenseCD-band observed in DNA-dispersions.

Mutant p53 exhibits trivial effects on mitochondrial functions which can be reactivated by ellipticine in lymphoma cells

Increasing evidence has shown that a fraction of the wild-type (wt) form of the tumor suppressor p53, can translocate to mitochondria due to genotoxic stress. The mitochondrial targets of wt p53 have also been studied. However, whether mutant p53, which exists in 50% of human cancers, translocates to mitochondria and affects mitochondrial functions is unclear. In this study, we used doxorubicin, a chemotherapeutic drug, to treat five human lymphoma cell lines with wt, mutant or deficient in p53, to induce p53 activation and mitochondrial translocation. Our results demonstrated that mutant p53, like wt p53, was induced upon doxorubicin treatment. Similarly, a fraction of mutant p53 also translocated to mitochondria. However, Complex I and II activities in the mitochondria were compromised only in wt p53-bearing cells after doxorubicin treatment, but not in mutant p53-bearing cells. Similarly, doxorubicin treatment caused greater cell death only in wt p53-bearing cells, but not in mutant p53-bearing cells. When p53 deficient Ramos cells were transfected with mutant p53 (249S), the cells showed resistance to doxorubicin-induced cell death and decreases in complex activities. To reactivate mutant p53 and reverse chemoresistance, ellipticine (5,11-dimethyl-6H-pyrido[4,3-b]carbazole) was used to treat mutant p53 cells. Ellipticine enhanced p53 mitochondrial translocation, decreased Complex I activity, and sensitized p53 mutant cells to doxorubicin-induced apoptosis. In summary, our studies suggest that mutations in p53 may not hinder p53's mitochondrial translocation, but impair its effects on mitochondrial functions. Therefore, restoring mutant p53 by ellipticine may sensitize these cells to chemotherapy.

Augmented anticancer efficacy of doxorubicin-loaded polymeric nanoparticles after oral administration in a breast cancer induced animal model

The present investigation reports an extensive evaluation of in vitro and in vivo anticancer efficacy of orally administered doxorubicin-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles (Dox-NPs) in a breast cancer induced animal model. Spherically shaped Dox-NPs were prepared with an entrapment efficiency and particle size of 55.40 ± 2.30% and 160.20 ± 0.99 nm, respectively, and freeze-dried with 5% trehalose using stepwise freeze-drying. Cytotoxicity, as investigated on C127I cell line, revealed insignificant differences between the IC(50) of free Dox and Dox-NPs treated cells in the first 24 h, while higher cytotoxicity was demonstrated by Dox-NPs, following 72 h of incubation. Confocal laser scanning microscopy (CLSM) imaging corroborated that nanoparticles were efficiently localized into the nuclear region of C127I cells. The cellular uptake profile of Dox-NPs revealed both time and concentration dependent increases in the Caco-2 cell uptake as compared to the free Dox solution. Further, Dox-NPs significantly suppressed the growth of breast tumor in female Sprague-Dawley (SD) rats upon oral administration. Finally, orally administered Dox-NPs showed a marked reduction in cardiotoxicity when compared with intravenously injected free Dox as also evident by the increased level of malondialdehyde (MDA), lactate dehydrogenase (LDH), and creatine phosphokinase (CK-MB) and reduced levels of glutathione (GSH) and superoxide dismutase (SOD). The reduced cardiotoxicity of orally administered Dox-NPs was also confirmed by the major histopathological changes in the heart tissue after the treatments of intravenously injected free Dox and orally delivered Dox-NPs.

Retinoblastoma tumor suppressor gene expression determines the response to sequential flavopiridol and doxorubicin treatment in small-cell lung carcinoma

PURPOSE

Small-cell lung cancers (SCLC) are defective in many regulatory mechanisms that control cell cycle progression, i.e., functional retinoblastoma protein (pRb). Flavopiridol inhibits proliferation and induces apoptosis in SCLC cell lines. We hypothesized that the sequence flavopiridol followed by doxorubicin would be synergistic in pRb-deficient SCLC cells.

EXPERIMENTAL DESIGN

A H69 pRb-deficient SCLC cell line, H865, with functional pRb and H865 pRb small interfering RNA (siRNA) knockdown cells were used for in vitro and in vivo experiments. The in vivo efficiencies of various sequential combinations were tested using nude/nude athymic mice and human SCLC xenograft models.

RESULTS

Flavopiridol then doxorubicin sequential treatment was synergistic in the pRB-negative H69 cell line. By knocking down pRb with specific siRNA, H865 clones with complete pRb knockdown became sensitive to flavopiridol and doxorubicin combinations. pRb-deficient SCLC cell lines were highly sensitive to flavopiridol-induced apoptosis. pRb-positive H865 cells arrested in G0-G1 with flavopiridol exposure, whereas doxorubicin and all flavopiridol/doxorubicin combinations caused a G2-M block. In contrast, pRb-negative SCLC cells did not arrest in G0-G1 with flavopiridol exposure. Flavopiridol treatment alone did not have an in vivo antitumor effect, but sequential flavopiridol followed by doxorubicin treatment provided tumor growth control and a survival advantage in Rb-negative xenograft models, compared with the other sequential treatments.

CONCLUSIONS

Flavopiridol and doxorubicin sequential treatment induces potent in vitro and in vivo synergism in pRb-negative SCLC cells and should be clinically tested in tumors lacking functional pRB.

Protection of multiple antioxidants Chinese herbal medicine on the oxidative stress induced by adriamycin chemotherapy

Adriamycin is an effective anthracycline anti-tumor antibiotic. However, the clinical use of adriamycin has been restricted by its serious side effects. Some reports indicated that the side effects of adriamycin could cause systemic injury, in which reactive oxygen species (ROS) play an important role. ROS are a large family of oxygen free radical and non-free radical active oxygen-containing molecules, including superoxide radical, hydrogen peroxide and hydroxyl radical, which contribute to oxidative stress. Although antioxidant treatment is a promising method to prevent the side effects, protection by a single antioxidant is limited. The Chinese herbal medicine ANTIOXIN is a multiple antioxidant that can effectively block oxidative stress. It was hypothesized that ANTIOXIN could effectively reduce the side effects of adriamycin. A rat tumor model with a transplanted tumor in the liver was treated with adriamycin and ANTIOXIN was used as a protection. Oxidative stress and antioxidant enzymes were evaluated. The results showed that adriamycin chemotherapy increased the level of malondialdehyde (MDA), nitrogen oxide (NO) and decreased the activities of total superoxide dismutase (T-SOD), manganese superoxide dismutase (MnSOD), catalase (CAT), glutathione (GSH) and total antioxidant capacity (TAC). Adriamycin chemotherapy also decreased the expression of Bcl-2, increased the expression of iNOS and cell apoptosis in the liver and kidney. Multiple antioxidants ANTIOXIN had an antagonistic effect on these changes and significantly decreased the mortality of the experimental rats. These data demonstrated that adriamycin chemotherapy could cause oxidative stress to the whole body, on which multiple antioxidants based on the theory of 'multiple antioxidant chain' had effective protection.

Evaluation of the effect of paclitaxel, epirubicin and tamoxifen by cell kinetics parameters in estrogen-receptor-positive ehrlich ascites tumor (eat) cells growing in vitro

In this study the antiproliferative effects of Paclitaxel (PAC), Epirubicin (EPI) and Tamoxifen (TAM) on growth kinetics of Ehrlich Ascites Tumor (EAT) cells were examined in culture. An estrogen-receptor-positive ER (+) hyperdiploid EAT cell line growing in vitro was also analysed in the present study. IC50 doses of PAC, EPI and TAM (12 microg/ml, 12 microg/ml and 2 microg/ml, respectively) were used. Cells were treated with the above doses for 0, 4, 8, 16, 24 and 32 hrs. At the end of these periods, living cell numbers were determined by collecting EAT cells in every group for growth study rate and for MTT assay. Therefore, the mitotic index was determined in the same experimental groups. The proliferation of EAT cells, inhibited by PAC, EPI and TAM concentrations was compared to control with increasing treatment time (4-32 hrs). Treatment of PAC, EPI and TAM alone for 24 hrs decreased the proliferation rate of EAT cells by 50% with respect to control. The inhibition of proliferation rate was higher in double drug treatment than that in single drug treatment with increased treatment time. In the treatment of three drugs applied for 32 hrs, this effect reached a maximum and proliferation rate decreased by 12% as compared to the (100%) control. In our studies, when the mitotic index parameter data were evaluated to determine which phase of the cell cycle was affected by PAC to cause the repression of cell reproduction, it was found that PAC exerted of its cytotoxic effect by causing cell accumulation at mitosis. The accumulation of the cells resulted in an increase in mitotic index values, which was an expected consequence of PAC treatment. It was observed that depending on the drug treatments, inhibition of proliferation rate and mitotic index in EAT cells were increased with respect to control, being with statistically significant occurrence (p < 0.01 - p < 0.001). As a result, concomitant treatment combined with hormonal therapy has given improved results compared with single treatment and PAC + EPI + TAM treatments had a maximum synergistic effect for 32 hrs (p < 0.001).

Biotin deficiency stimulates survival pathways in human lymphoma cells exposed to antineoplastic drugs

Cells may respond to nutrient deficiency or death signals with nuclear translocation of the transcription factor nuclear factor kappaB (NF-kappaB), which activates transcription of anti-apoptotic genes. Here we tested the hypothesis that biotin deficiency stimulates NF-kappaB-dependent survival pathways in human lymphoma cells, enhancing resistance to antineoplastic agents. Lymphoma (Jurkat) cells were cultured in biotin-deficient (0.025 nmol/L) and biotin-supplemented (10 nmol/L) media. If cells were treated with antineoplastic agents (taxol, doxorubicin or vinblastine), nuclear translocation of two NF-kappaB proteins (p50 and p65) was >25% greater in biotin-deficient compared with biotin-supplemented cells. The transcriptional activities of the following NF-kappaB-dependent reporter genes were 16-59% greater in biotin-deficient compared with biotin-supplemented cells treated with various antineoplastic agents: (1) reporter expression driven by a TATA box and five NF-kappaB repeats and (2) reporter expression driven by the regulatory region of the anti-apoptotic Bfl-1 gene. Collectively, these findings are consistent with activation of survival pathways in biotin-deficient lymphoma cells. Finally, cells were treated with antineoplastic agents for 48 h and cell survival was monitored at timed intervals. Biotin deficiency was associated with enhanced survival of cells treated with doxorubicin and vinblastine, but did not affect survival of cells treated with taxol. Collectively, these observations suggest that biotin deficiency may enhance resistance of cancer cells to antineoplastic agents.

The activation of c-Jun NH2-terminal kinase (JNK) by DNA-damaging agents serves to promote drug resistance via activating transcription factor 2 (ATF2)-dependent enhanced DNA repair

The activating transcription factor 2 (ATF2) is a member of the ATF/cAMP-response element-binding protein family of basic-leucine zipper proteins involved in cellular stress response. The transcription potential of ATF2 is enhanced markedly by NH2-terminal phosphorylation by c-Jun NH2-terminal kinase (JNK) and mediates stress responses including DNA-damaging events. We have observed that four DNA-damaging agents (cisplatin, actinomycin D, MMS, and etoposide), but not the cisplatin isomer, transplatin, which does not readily damage DNA, strongly activate JNK, p38, and extracellular signal-regulated kinase (ERK), and strongly increase phosphorylation and ATF2-dependent transcriptional activity. Selective inhibition studies with PD98059, SB202190, SP600125, and the dominant negative JNK indicate that activation of JNK but not p38 kinase or ERK kinase is required for the phosphorylation and transcriptional activation of ATF2. Stable expression of ATF2 in human breast carcinoma BT474 cells increases transcriptional activity and confers resistance to the four DNA-damaging agents, but not to transplatin. Conversely, stable expression of a dominant negative ATF2 (dnATF2) quantitatively blocks phosphorylation of endogenous ATF2 leading to a marked decrease in transcriptional activity by endogenous ATF2 and a markedly increased sensitivity to the four agents as judged by decreased cell viability. Similarly, application of SB202190 at 50 micro m or SP600125 inhibited JNK activity, blocked transactivation, and sensitized parental cells to the four DNA-damaging drugs. Moreover, the wild type ATF2-expressing clones exhibited rapid DNA repair after treatment with the four DNA-damaging agents but not transplatin. Conversely, expression of dnATF2 quantitatively blocks DNA repair. These results indicate that JNK-dependent phosphorylation of ATF2 plays an important role in the drug resistance phenotype likely by mediating enhanced DNA repair by a p53-independent mechanism. JNK may be a rational target for sensitizing tumor cells to DNA-damaging chemotherapy agents.

Myocet (liposome-encapsulated doxorubicin citrate): a new approach in breast cancer therapy

Doxorubicin, either as a single agent or in combination regimens, is considered to be one of the most active chemotherapeutic agents in the treatment of metastatic breast cancer. However, its clinical utility is limited by a cumulative, dose-dependent cardiac myopathy that can lead to potentially fatal congestive heart failure. Considerable research has gone into improving the therapeutic index of doxorubicin-based regimens. A new liposomal formulation of doxorubicin (Myocet, Elan Pharmaceuticals) has a significantly improved therapeutic index compared with conventional doxorubicin. The development of Myocet, a less cardiotoxic, better tolerated and equally efficacious doxorubicin, extends the therapeutic options in the overall management of breast cancer.

A multivariate approach to the association pattern of reciprocal translocations induced by chemicals and ionizing radiation in mouse germ cells

The degree of similarity between chemical and physical agents in their capacity to induce reciprocal translocations was analyzed by means of multivariate analysis techniques. The effect of three different doses of gamma rays, four doses of X-rays and different doses of adriamycin, mitomycin C, thio-tepa and bleomycin was analyzed. Data were arranged in a basic matrix by two methods: cluster analysis and ordination. Two main groups were found, one including doses of 9 and 10 Gy and the other including the remaining lower doses of ionizing radiation and the other chemicals. Various subgroups were found within the second group. Accordingly, using presence/absence data there was not a specific pattern of chromosomal damage induction for physical and chemical agents. The increase in the frequencies of reciprocal translocation observed with 9 and 10 Gy was due to an increase in the kind of multivalent configurations. This variability could be dose dependent. Likewise, the similarity observed in the second group between the chemicals and the lower doses of ionizing radiation could also be dose dependent.

Release of the cyano moiety in the crystal structure of N-cyanomethyl-N-(2-methoxyethyl)-daunomycin complexed with d(CGATCG)

Doxorubicin is among the most widely used anthracycline in cancer chemotherapy. In an attempt to avoid the cardiotoxicity and drug resistance of doxorubicin therapy, several analogues were synthesized. The cyanomorpholinyl derivative is the most cytotoxic. They differ greatly from their parent compound in their biological and pharmacological properties, inducing cross-links in drug DNA complexes. The present study concerns N-cyanomethyl-N-(2-methoxyethyl)-daunomycin (CMDa), a synthetic analogue of cyanomorpholino-daunomycin. Compared to doxorubicin, CMDa displays a cytotoxic activity on L1210 leukemia cells at higher concentration but is effective on doxorubicin resistant cells. The results of fluorescence quenching experiments as well as the melting temperature (DeltaTm = 7.5 degrees C) studies are consistent with a drug molecule which intercalates between the DNA base pairs and stabilizes the DNA double helix. The crystal structure of CMDa complexed to the hexanucleotide d(CGATCG) has been determined at 1.5 A resolution. The complex crystallizes in the space group P41212 and is similar to other anthracycline-hexanucleotide complexes. In the crystal state, the observed densities indicate the formation of N-hydroxymethyl-N-(2-methoxyethyl)-daunomycin (HMDa) with the release of the cyano moiety without DNA alkylation. The formation of this degradation compound is discussed in relation with other drug modifications when binding to DNA. Comparison with two other drug-DNA crystal structures suggests a correlation between a slight change in DNA conformation and the nature of the amino sugar substituents at the N3' position located in the minor groove.