In vitro cytotoxic study of immunoliposomal doxorubicin targeted to human CD34+ leukemic cells

Electrochemical Sensor Based on Poly(Azure B)-DNA Composite for Doxorubicin Determination

A new voltammetric DNA sensor has been developed for doxorubicin determination on the platform of a glassy carbon electrode (GCE) covered with electropolymerized Azure B film and physically adsorbed native DNA. The redox properties of polymeric Azure B were monitored at various pH and scan rates. DNA application decreased the peak currents related to polymeric and monomeric forms of the dye, whereas incubation in doxorubicin solution partially restored the peaks in accordance with the drug and DNA concentration. The relative shift of the cathodic peak current caused by doxorubicin depended on the nominal DNA concentration and its application mode. In optimal conditions, the DNA sensor makes it possible to determine between 0.1 μM to 0.1 nM doxorubicin (limit of detection 7×10-11 M). The DNA sensor was tested on commercial doxorubicin formulations and on artificial samples the mimicked electrolyte content of human serum.

Surface-Modified Liposomal Formulation of Amphotericin B: In vitro Evaluation of Potential Against Visceral Leishmaniasis

Surface modification of liposomes with targeting ligands is known to improve the efficacy with reduced untoward effects in treating infective diseases like visceral leishmaniasis (VL). In the present study, modified ligand (ML), designed by modifying polysaccharide with a long chain lipid was incorporated in liposomes with the objective to target amphotericin B (Amp B) to reticuloendothelial system and macrophages. Conventional liposomes (CL) and surface modified liposomes (SML) were characterized for size, shape, and entrapment efficiency (E.E.). Amp B SML with 3% w/w of ML retained the vesicular nature with particle size of ∼205 nm, E.E. of ∼95% and good stability. SML showed increased cellular uptake in RAW 264.7 cells which could be attributed to receptor-mediated endocytosis. Compared to Amp B solution, Amp B liposomes exhibited tenfold increased safety in vitro in RAW 264.7 and J774A.1 cell lines. Pharmacokinetics and biodistribution studies revealed high t _1/2, area under the curve (AUC)_0-24, reduced clearance and prolonged retention in liver and spleen with Amp B SML compared to other formulations. In promastigote and amastigote models, Amp B SML showed enhanced performance with low 50% inhibitory concentration (IC₅₀) compared to Amp B solution and Amp B CL. Thus, due to the targeting ability of ML, SML has the potential to achieve enhanced efficacy in treating VL.

Efficient delivery of docetaxel for the treatment of brain tumors by cyclic RGD-tagged polymeric micelles

The treatment of glioblastoma, and other types of brain cancer, is limited due to the poor transport of drugs across the blood brain barrier and poor penetration of the blood‑brain‑tumor barrier. In the present study, cyclic Arginine‑Glycine‑Aspartic acid‑D‑Tyrosine‑Lysine [c(RGDyK)], that has a high binding affinity to integrin αvβ3 receptors, that are overexpressed in glioblastoma cancers, was employed as a novel approach to target cancer by delivering therapeutic molecules intracellularly. The c(RGDyK)/docetaxel polylactic acid‑polyethylene glycol (DTX‑PLA‑PEG) micelle was prepared and characterized for various in vitro and in vivo parameters. The specific binding affinity of the Arginine‑Glycine‑Aspartic acid (RGD) micelles, to the integrin receptor, enhanced the intracellular accumulation of DTX, and markedly increased its cytotoxic efficacy. The effect of microtubule stabilization was evident in the inhibition of glioma spheroid volume. Upon intravenous administration, c(RGDyK)/DTX‑PLA‑PEG showed enhanced accumulation in brain tumor tissues through active internalization, whereas non‑targeted micelles showed limited transport ability. Furthermore, RGD‑linked micelles showed marked anti‑glioma activity in U87MG malignant glioma tumor xenografts, and significantly suppressed the growth of tumors without signs of systemic toxicity. In conclusion, the results of the present study suggest that ligand‑mediated drug delivery may improve the efficacy of brain cancer chemotherapy.

Anti-CD30 antibody conjugated liposomal doxorubicin with significantly improved therapeutic efficacy against anaplastic large cell lymphoma

The use of nano-carriers has been shown to improve the delivery and efficacy of chemotherapeutic agents in cancer patients. Recent studies suggest that decoration of the surface of nano-carriers with various targeting moieties may further improve the overall therapeutic efficacy. In this study, we compared the therapeutic efficacy of Doxil(®) (commercial doxorubicin-loaded liposomes) and that of Doxil(®) conjugated with anti-CD30 antibodies (CD30-targeted Doxil(®)) in treating anaplastic large cell lymphoma (ALCL), a type of T-cell lymphoma characterized by a high CD30 expression. Compared to Doxil(®), the CD30-targeted Doxil(®) showed a significantly higher binding affinity to ALCL cells (5.3% versus 27%, p = 0.005) and a lower inhibitory concentration at 50% (IC50) in-vitro (32.6 μg/mL versus 12.6 μg/mL, p = 0.006). In a SCID mouse xenograft model, CD30-targeted Doxil(®) inhibited tumor growth more significantly than the unconjugated formulation; specifically, tumors in mice treated with CD30-targeted Doxil(®) were significantly smaller than those in mice treated with Doxil(®) (average, 117 mm(3) versus 270 mm(3), p = 0.001) at 18 days after the tumors were inoculated. Our findings have provided the proof-of-principle of using CD30-targeted nano-carriers to treat cancers that are characterized by a high level of CD30 expression, such as ALCL.

E-selectin liposomal and nanotube-targeted delivery of doxorubicin to circulating tumor cells

The presence of circulating tumor cells (CTCs) is believed to lead to the formation of secondary tumors via an adhesion cascade involving interaction between adhesion receptors of endothelial cells and ligands on CTCs. Many CTCs express sialylated carbohydrate ligands on their surfaces that adhere to selectin protein found on inflamed endothelial cells. We have investigated the feasibility of using immobilized selectin proteins as a targeting mechanism for CTCs under flow. Herein, targeted liposomal doxorubicin (L-DXR) was functionalized with recombinant human E-selectin (ES) and polyethylene glycol (PEG) to target and kill cancer cells under shear flow, both when immobilized along a microtube device or sheared in a cone-and-plate viscometer in a dilute suspension. Healthy circulating cells such as red blood cells were not targeted by this mechanism and were left to freely circulate, and minimal leukocyte death was observed. Halloysite nanotube (HNT)-coated microtube devices immobilized with nanoscale liposomes significantly enhanced the targeting, capture, and killing of cancer cells. This work demonstrates that E-selectin functionalized L-DXR, sheared in suspension or immobilized onto microtube devices, provides a novel approach to selectively target and deliver chemotherapeutics to CTCs in the bloodstream.

The effect of glucosylceramide synthase on P-glycoprotein function in K562/AO2 leukemia drug-resistance cell line

Previous work from our laboratory demonstrated that glucosylceramide synthase (GCS) and multidrug resistance 1 gene (MDR1) are co-overexpressed in drug-resistant leukemia cells. We hypothesized that GCS and MDR1 may interact. In this study, we used RNA interference (RNAi) to silence the GCS or MDR1 gene in K562/AO2 drug-resistant cells. The sensitivity of cells to different treatments with doxorubicin was evaluated. We used Taqman probe fluorescence real-time quantitative PCR, and detected expression of GCS and MDR1 mRNAs in different interfering groups. Intracellular mean fluorescence intensity (MFI), which represents rhodamine123 (rh123) retention, was determined by flow cytometry (FCM). An MTT cytotoxicity assay showed that the 50% inhibition concentration (IC50) of doxorubicin of K562/AO2 cells (138.25 ± 3.75 µg/ml) was significantly higher than that of K562 drug-sensitive cells (2.125 ± 0.125 µg/ml), and that IC50 was evidently lower in K562/AO2 cells, whether it was transfected with a small interfering RNA (siRNA) targeting GCS (GCSsiRNA) or one targeting MDR1 (MDR1siRNA). Compared with untreated K562/AO2 cells, the inhibition rates of GCS mRNA in the cells transfected with GCSsiRNA for 9 and 36 h were 56.67 ± 9.29% (p < 0.05) and 74 ± 6.38% (p < 0.05), respectively. Interestingly, the expression of MDR1 mRNA was also inhibited to 51.7 ± 4.5% (p < 0.05) 36 h after transfection with GCSsiRNA, but there was no significant difference in MDR1 expression at 9 h post-transfection in cells treated with GCSsiRNA and a negative control. It is well known that rh123 retention in cells results from an efflux function of P-glycoprotein (P-gp). In K562 cells, rh123 retention was much higher than in K562/AO2 cells (p < 0.01). We also noted that rh123 retention in the K562/AO2 cells transfected with GCSsiRNA for 48 h was significantly higher than in the negative control group. In conclusion, we show in the present study that inhibition of the GCS gene affects the expression of MDR1 mRNA and P-gp function.

Preparation and characterization of zedoary turmeric oil-loaded insulin-modified sterically stabilized liposomes

The poor selectivity of anticancer drugs often leads to their multiplicate dose-limiting toxicities in humans, which severely restricts their clinical application. In this study, a novel liposomal formulation of zedoary turmeric oil (ZTO) targeting the insulin receptor (IR) was prepared by covalently conjugating insulin to the terminal of the polyethylene glycol (PEG) chain of sterically stabilized liposomes. In vitro assays indicated that a higher uptake of insulin-modified sterically stabilized liposomes (ISSLs) was observed in SMMC-7721 hepatocarcinoma cells overexpressing insulin receptors. IC(50) values of ISSLs, NTLs (nontargeted liposomes), and ZTO injection (free ZTO) against SMMC-7721, determined by MTT assays, were 157.2, 256.7, and 43.3 microg x ml(-1), respectively. Plasma-clearance profiles of ZTO in the liposomal formulations were then compared with that of ZTO injection. The liposomal formulations showed much longer terminal half-lives (11.24 and 14.73 hours for ISSLs and NTLs, respectively) than that of ZTO injection (1.45 hours). All results above indicated the ISSLs were potentially useful for the treatment of IR (+) tumors and are worthy of further investigation.

GCS induces multidrug resistance by regulating apoptosis-related genes in K562/AO2 cell line

We have previously shown that the expression of glucosylceramide synthase (GCS) gene in drug-resistant K562/AO2 human leukemia cell was higher than that in drug-sensitive K562 cell, and the sensitivity to adriamycin of K562/AO2 cell was enhanced by inhibiting GCS. It is concluded that the overexpression of GCS gene is one of the reasons which lead to multidrug resistance (MDR) of leukemia cell. Meanwhile, we also found that higher expression of Bcl-2 gene and protein were exhibited in K562/AO2 cell compared with K562 cell. Basing on this, we hypothesized that the high expression of GCS gene which results in MDR of leukemia cell is correlated with Bcl-2 signal transduction. In order to validate the hypothesis, the inhibition of GCS gene in K562/AO2 cell was observed by using chemical suppressor PPMP and siRNA targeted at GCS, and applying RT-PCR and flow cytometry, the expression levels of apoptosis-related gene Bcl-2 and Bax were analyzed before and after inhibiting GCS gene in K562/AO2 cell. The results demonstrated that the gene and protein of Bcl-2 in K562/AO2 cell were both down-regulated significantly after GCS gene being inhibited; however, the Bax mRNA expression had no apparent change in different groups. This suggested that GCS gene may contributed to MDR of human leukemia cell K562/AO2 by Bcl-2 signal transduction.

Nanomicellar paclitaxel increases cytotoxicity of multidrug resistant breast cancer cells

Multidrug resistance (MDR) of breast cancer cells still represents an unmet medical need in chemotherapy. To this end, the purpose of this study was to determine efficacy of paclitaxel loaded in sterically stabilized, biocompatible and biodegradable sterically stabilized mixed phospholipid nanomicelles (SSMM; size, approximately 15 nm) and actively targeted vasoactive intestinal peptide-grafted SSMM (SSMM-VIP) in circumventing P-gp-mediated paclitaxel resistance in BC19/3 cells, a human breast cancer cell line that expresses >10-fold higher P-gp than its parental sensitive cell line, MCF-7. We found that in drug sensitive MCF-7 cells, paclitaxel loaded in SSMM (P-SSMM) and SSMM-VIP (P-SSMM-VIP) significantly inhibited cell growth in dose-dependent fashion (p<0.05). Both formulations were approximately 7-fold more potent than paclitaxel dissolved in DMSO (P-DMSO). Efficacy of P-SSMM and P-SSMM-VIP was similar (p>0.5). By contrast, in drug resistant BC19/3 cells, P-SSMM-VIP was significantly more effective than either P-SSMM or P-DMSO ( approximately 2- and 5-fold, respectively; p<0.05). Collectively, these data indicate that actively targeted paclitaxel-loaded SSMM-VIP overcomes multiple drug resistance of BC19/3 cells. We suggest this formulation should be further developed to treat MDR breast cancer.

Monoclonal antibody 2C5-modified doxorubicin-loaded liposomes with significantly enhanced therapeutic activity against intracranial human brain U-87 MG tumor xenografts in nude mice

Liposomes, modified with monoclonal antibodies, are suitable carriers for targeted delivery of chemotherapeutic drugs into brain tumors. Here, we investigate the therapeutic efficacy of monoclonal anticancer antibody 2C5-modified long-circulating liposomes (LCL) loaded with doxorubicin (2C5-DoxLCL) for the treatment of U-87 MG human brain tumors in an intracranial model in nude mice. In vitro, 2C5-DoxLCL is significantly more effective in killing the U-87 MG tumor cells than Doxil (commercial doxorubicin-loaded PEGylated LCL) or DoxLCL modified with a non-specific IgG. 2C5-immunoliposomes also demonstrate a significantly higher accumulation in U-87 MG tumors compared to all controls in a subcutaneous model. The treatment of intracranial U-87 MG brain tumors in nude mice with 2C5-DoxLCL provides a significant therapeutic benefit over control formulations, substantially reducing the tumor size and almost doubling the survival time. Thus, monoclonal antibody 2C5-modified LCL can specifically target the anticancer drugs to brain tumors, leading to improved therapeutic treatment of brain tumor in an intracranial model, in vivo.

A comparison of the effect of anticancer drugs, idarubicin and adriamycin, on soluble chromatin

The biological activity of an anticancer agent is related to its physicochemical interaction with biological receptors. In the present study we have investigated and compared the affinity and mode of action of two potent anticancer drugs, adriamycin and idarubicin on soluble chromatin using ultraviolet/visible and fluorescence spectroscopy, hydroxyapatite (HAP) chromatography and gel electrophoresis techniques. The results show that addition of various concentrations of drugs to chromatin solution individually, reduced both absorbance and fluorescence emission intensity of chromatin and precipitated it in a dose dependent manner, however, the extent of reduction was different for two drugs used. This effect was also observed on the histone gel patterns of the drug treated samples revealing that the chromatin is less affected by idarubicin compared to adriamycin implying higher aggregation of chromatin with the former. As hydroxyapatite chromatograms show, histone H1 represented the highest drug binding activity. The results suggest that although adriamycin and idarubicin are both grouped anthracycline antibiotic anticancer drugs, they differ considerably on their binding affinity to cellular chromatin.

Affinity of anticancer drug, daunomycin, to core histones in solution: comparison of free and cross-linked proteins

AIM

The interaction of anthracycline anticancer drugs with chromatin, nucleosomes and histone H1 has been extensively studied. In the present study, for the first time, we have investigated the binding of anthracycline antibiotic, daunomycin, to free and cross-linked thymus core histones (CL-core) in solution and in the absence of DNA.

METHODS

Fluorescence, UV/Vis spectroscopy and equilibrium dialysis techniques were used.

RESULTS

The UV spectroscopy results show that daunomycin induces hypochromicity in the absorption spectra of the core histones. Fluorescence emission intensity is decreased upon daunomycin binding and the process is concentration dependent. The equilibrium dialysis shows that the binding is positive cooperative with the binding sites as Scatchard plot and Hill Coefficient confirm it.

CONCLUSION

The results suggest that daunomycin shows much higher affinity to core histones free in solution than to CL-core, implying that the binding is most likely due to the accessibility of these proteins to the environment. It is suggested that daunomycin binds strongly to open state of histones, such as in tumor cells, rather than to their compact structure seen in normal chromatin.

Chromatin as a target for the DNA-binding anticancer drugs

Chemotherapy has been a major approach to treat cancer. Both constituents of chromatin, chromosomal DNA and the associated chromosomal histone proteins are the molecular targets of the anticancer drugs. Small DNA binding ligands, which inhibit enzymatic processes with DNA substrate, are well known in cancer chemotherapy. These drugs inhibit the polymerase and topoisomerase activity. With the advent in the knowledge of chromatin chemistry and biology, attempts have shifted from studies of the structural basis of the association of these drugs or small ligands (with the potential of drugs) with DNA to their association with chromatin and nucleosome. These drugs often inhibit the expression of specific genes leading to a series of biochemical events. An overview will be given about the latest understanding of the molecular basis of their action. We shall restrict to those drugs, synthetic or natural, whose prime cellular targets are so far known to be chromosomal DNA.

Multiple drug resistance in cancer revisited: the cancer stem cell hypothesis

The failure to eradicate cancer may be as fundamental as a misidentification of the target. Current therapies succeed at eliminating bulky disease but often miss a tumor reservoir that is the source of disease recurrence and metastasis. Recent advances in the understanding of tissue development and repair cause us to revisit the process of drug resistance as it applies to oncogenesis and tumor heterogeneity. The cancer stem cell hypothesis states that the cancer-initiating cell is a transformed tissue stem cell, which retains the essential property of self-protection through the activity of multiple drug resistance (MDR) transporters. This resting constitutively drug-resistant cell remains at low frequency among a heterogeneous tumor mass. In the context of this hypothesis, the authors review the discovery of MDR transporters in cancer and normal stem cells and the failure of MDR reversal agents to increase the therapeutic index of substrate antineoplastic agents.

The anthracycline antibiotics: antitumor drugs that alter chromatin structure

Anthracycline antibiotics are an important group of antitumor drugs widely used in cancer chemotherapy. However, despite the increasing interest in these chemotherapeutic agents, their mechanism of action is not yet completely understood. Here, we review what is currently known about the molecular mechanisms involved with special emphasis on the interaction of these drugs with chromatin and its constitutive components: DNA and histones. The evidence suggests that one very important component of the activity of these drugs is the result of these manifold interactions that lead to a chromatin unfolding and aggregation. This chromatin structural disruption is likely to interfere with the metabolic processes of DNA (replication and transcription) and it may play an important role in the apoptosis undergone by the cells upon treatment with these drugs.