Surfactant-polymer nanoparticles overcome P-glycoprotein-mediated drug efflux

Nanoparticles enhance the therapeutic efficacy of an encapsulated drug by increasing and sustaining the delivery of the drug inside the cell. We have previously demonstrated that Aerosol OT (AOT)-alginate nanoparticles, a novel formulation developed recently in our laboratory, significantly enhance the therapeutic efficacy of encapsulated drugs like doxorubicin in drug-sensitive tumor cells. The purpose of this study is to evaluate the drug delivery potential of AOT-alginate nanoparticles in drug-resistant cells overexpressing the drug efflux transporter, P-glycoprotein (P-gp). AOT-alginate nanoparticles were formulated using an emulsion-cross-linking process. Rhodamine 123 and doxorubicin were used as model P-gp substrates. Cytotoxicity of nanoparticle-encapsulated doxorubicin and kinetics of nanoparticle-mediated cellular drug delivery were evaluated in both drug-sensitive and -resistant cell lines. AOT-alginate nanoparticles enhanced the cytotoxicity of doxorubicin significantly in drug-resistant cells. The enhancement in cytotoxicity with nanoparticles was sustained over a period of 10 days. Uptake studies with rhodamine-loaded nanoparticles indicated that nanoparticles significantly increased the level of drug accumulation in resistant cells at nanoparticle doses higher than 200 microg/mL. Blank nanoparticles also improved rhodamine accumulation in drug-resistant cells in a dose-dependent manner. Nanoparticle-mediated enhancement in rhodamine accumulation was not because of membrane permeabilization. Fluorescence microscopy studies demonstrated that nanoparticle-encapsulated doxorubicin was predominantly localized in the perinuclear vesicles and to a lesser extent in the nucleus, whereas free doxorubicin accumulated mainly in peripheral endocytic vesicles. Inhibition of P-gp-mediated rhodamine efflux with AOT-alginate nanoparticles was confirmed in primary brain microvessel endothelial cells. In conclusion, an AOT-alginate nanoparticle system enhanced the cellular delivery and therapeutic efficacy of P-gp substrates in P-gp-overexpressing cells.     

Long-circulating PEG-PE micelles co-loaded with paclitaxel and elacridar (GG918) overcome multidrug resistance

Overexpression of drug efflux pump P-gp is one of the major reasons to cause multidrug resistance (MDR). To overcome P-gp mediated MDR, modulators, so called P-gp inhibitors, can be used to block efflux pump activity. Elacridar is one of the most potent P-gp inhibitors, which can cause irreversible and total P-gp blockage. Elacridar, among with other P-gp inhibitors, can be used in combination with anticancer drugs to enhance the effectiveness of chemotherapy against resistant tumor cells. On the other hand, P-gp is presented in normal tissues, thus non-selective blockage of P-gp can cause undesired side effects. Therefore, it is important to deliver P-gp inhibitor only to the tumor cells (along with anticancer drug) and limit its distribution in the body. In this study, we have developed PEG-PE-based long-circulating ca. 15?nm micelles co-loaded with elacridar and paclitaxel, and investigated their ability to overcome paclitaxel resistance in two cancer cell lines. Vitamin E, a common solubility enhancer for PEG-PE micelles, was found to have a negative effect on both particle size and encapsulation efficiencies. The human MDR1 gene-transfected and thus paclitaxel-resistant MDCKII-MDR1 P-gp overexpressing cells were used for cytotoxicity evaluation. Even though PEG-PE based micelles itself have a potential to enhance the cytotoxicity of paclitaxel, elacridar/paclitaxel-co-loaded micelles demonstrated the highest cytotoxicity compared to both free and micellar paclitaxel. The obtained results suggest that co-loading of paclitaxel and elacridar into micellar drug carriers results in promising preparations capable of overcoming paclitaxel resistance.     

Reversal of multidrug resistance by co-delivery of tariquidar (XR9576) and paclitaxel using long-circulating liposomes

One of the major obstacles to the success of cancer chemotherapy is the multidrug resistance (MDR) often resulting due to the overexpression of drug efflux transporter pumps such as P-glycoprotein (P-gp). Highly efficacious third generation P-gp inhibitors, like tariquidar, have shown promising results in overcoming the MDR. However, P-gp is also expressed in normal tissues like blood brain barrier, gastrointestinal track, liver, spleen and kidney. To maximize the efficacy of P-gp inhibitor and reduce the systemic toxicity, it is important to limit the exposure of P-gp inhibitors and the anticancer drugs to normal tissues and increase their co-localization with tumor cells. In this study, we have investigated the co-delivery of the P-gp inhibitor, tariquidar, and cytotoxic drug, paclitaxel, into tumor cells to reverse the MDR using long-circulating liposomes. Tariquidar- and paclitaxel-loaded long-circulating liposomes showed significant resensitization of the resistant variant for paclitaxel, which could be correlated with an increased accumulation of paclitaxel in tumor cells. These results suggest that the co-delivery of the P-gp inhibitor, tariquidar, and the cytotoxicity inducer, paclitaxel, looks like a promising approach to overcome the MDR.     

BioPerine Encapsulated Nanoformulation for Overcoming Drug-Resistant Breast Cancers

The evolving dynamics of drug resistance due to tumor heterogeneity often creates impediments to traditional therapies making it a challenging issue for cancer cure. Breast cancer often faces challenges of current therapeutic interventions owing to its multiple complexities and high drug resistivity， for example against drugs like trastuzumab and tamoxifen. Drug resistance in the majority of breast cancer is often aided by the overtly expressed P-glycoprotein (P-gp) that guides in the rapid drug efflux of chemotherapy drugs. Despite continuous endeavors and ground-breaking achievements in the pursuit of finding better cancer therapeutic avenues, drug resistance is still a menace to hold back. Among newer therapeutic approaches, the application of phytonutrients such as alkaloids to suppress P-gp activity in drug-resistant cancers has found an exciting niche in the arena of alternative cancer therapies. In this work, we would like to present a black pepper alkaloid derivative known as BioPerine-loaded chitosan (CS)-polyethylene glycol (PEG) coated polylactic acid (PLA) hybrid polymeric nanoparticle to improve the bioavailability of BioPerine and its therapeutic efficacy in suppressing P-gp expression in MDA-MB 453 breast cancer cell line. Our findings revealed that the CS-PEG-BioPerine-PLA nanoparticles demonstrated a smooth spherical morphology with an average size of 316 nm, with improved aqueous solubility, and provided sustained BioPerine release. The nanoparticles also enhanced in vitro cytotoxicity and downregulation of P-gp expression in MDA-MB 453 cells compared to the commercial inhibitor verapamil hydrochloride, thus promising a piece of exciting evidence for the development of BioPerine based nano-drug delivery system in combination with traditional therapies as a crucial approach to tackling multi-drug resistance in cancers.     

Flavonoid dimers as bivalent modulators for P-glycoprotein-based multidrug resistance: synthetic apigenin homodimers linked with defined-length poly(ethylene glycol) spacers increase drug retention and enhance chemosensitivity in resistant cancer cells

Much effort has been spent on searching for better P-glycoprotein- (P-gp-) based multidrug resistance (MDR) modulators. Our approach was to target the binding sites of P-gp using dimers of dietary flavonoids. A series of apigenin-based flavonoid dimers, linked by poly(ethylene glycol) chains of various lengths, have been synthesized. These flavonoid dimers modulate drug chemosensitivity and retention in breast and leukemic MDR cells with the optimal number of ethylene glycol units equal to 2-4. Compound 9d bearing four ethylene glycol units increased drug accumulation in drug-resistant cells and enhanced cytotoxicity of paclitaxel, doxorubicin, daunomycin, vincristine, and vinblastine in drug-resistant breast cancer and leukemia cells in vitro, resulting in reduction of IC50 by 5-50 times. This compound also stimulated P-gp's ATPase activity by 3.3-fold. Its modulating activity was presumably by binding to the substrate binding sites of P-gp and disrupting drug efflux.     

Nanoparticle-mediated combination chemotherapy and photodynamic therapy overcomes tumor drug resistance in vitro

Drug resistance limits the success of many anticancer drugs. Reduced accumulation of the drug at its intracellular site of action because of overexpression of efflux transporters such as P-glycoprotein (P-gp) is a major mechanism of drug resistance. In this study, we investigated whether photodynamic therapy (PDT) using methylene blue, also a P-gp inhibitor, can be used to enhance doxorubicin-induced cytotoxicity in drug-resistant tumor cells. Aerosol OT (AOT)-alginate nanoparticles were used as a carrier for the simultaneous cellular delivery of doxorubicin and methylene blue. Methylene blue was photoactivated using light of 665 nm wavelength. Induction of apoptosis and necrosis following treatment with combination chemotherapy and PDT was investigated in drug-resistant NCI/ADR-RES cells using flow cytometry and fluorescence microscopy. Effect of encapsulation in nanoparticles on the intracellular accumulation of doxorubicin and methylene blue was investigated qualitatively using fluorescence microscopy and was quantitated using HPLC. Encapsulation in AOT-alginate nanoparticles significantly enhanced the cytotoxicity of combination therapy in resistant tumor cells. Nanoparticle-mediated combination therapy resulted in a significant induction of both apoptosis and necrosis. Improvement in cytotoxicity could be correlated with enhanced intracellular and nuclear delivery of the two drugs. Further, nanoparticle-mediated combination therapy resulted in significantly elevated reactive oxygen species (ROS) production compared to single drug treatment. In conclusion, nanoparticle-mediated combination chemotherapy and PDT using doxorubicin and methylene blue was able to overcome resistance mechanisms and resulted in improved cytotoxicity in drug-resistant tumor cells.     

Increase in doxorubicin cytotoxicity by inhibition of P-glycoprotein activity with lomerizine

Acquired resistance to chemotherapy is a major problem during cancer treatment. One mechanism for drug resistance is overexpression of the MDR (multidrug resistance)1 gene encoding the transmembrane efflux pump, P-glycoprotein (P-gp). Calcium channel blockers such as verapamil, nifedipine and nicardipine have been shown to reverse cellular drug resistance by inhibiting P-gp drug efflux. This study evaluated whether a new calcium channel blocker, lomerizine, influenced doxorubicin (Dox) cytotoxicity and P-gp activity in a P-gp-expressing cell line compared to a non-expressing subline. Verapamil, and even more markedly, lomerizine, increased cellular uptake of calcein transported by P-gp in a P-gp-expressing erythroleukemia cell line, K562-Dox. Ten microM of lomerizine reduced the IC50 of doxorubicin in the K562-Dox from 60000 ng/ml to 800 ng/ml, whereas the IC50 of doxorubicin in the K562 subline was only marginally affected by these drugs. Lomerizine showed greater reduction in P-gp efflux than verapamil at an equimolar concentration. These results suggest that lomerizine has the clinical potential to reverse tumor MDR involving the efflux protein P-gp.     

Reversal of multidrug resistance by methoxypolyethylene glycol-block-polycaprolactone diblock copolymers through the inhibition of P-glycoprotein function

Overexpression of P-glycoprotein (Pgp) is one of the major limitations in cancer chemotherapy. Previous work has shown that amphiphilic diblock copolymers composed of methoxypolyethylene glycol-block-polycaprolactone (MePEG-b-PCL) diblock copolymers enhanced the cellular accumulation of Pgp substrates by modulating the function of this drug efflux transporter. The objective of this work was to determine whether MePEG-b-PCL diblock copolymers modulated Pgp function in multidrug resistant (MDR) cancer cells. The diblock copolymer enhanced the accumulation of various Pgp substrates in Pgp overexpressing MDR cells but did not influence substrate accumulation in non-Pgp expressing cells. Treatment of MDR cells with the diblock copolymer enhanced paclitaxel (ptx) and doxorubicin (dox) accumulation. Following uptake, ptx was rapidly effluxed from MDR cells whereas diblock copolymer treatment retained dox inside MDR cells. Treatment of MDR cells with the diblock copolymer reversed drug resistance to dox but not ptx. However, resistance to ptx was reversed by verapamil, which indicated that a sustained inhibition of Pgp was required for ptx to induce cytotoxicity in MDR cells. Taken together, these results highlight the potential of MePEG-b-PCL diblock copolymer to reverse drug resistance in MDR cancer cells through inhibition of Pgp function, making it a promising candidate for overcoming MDR.     

Increase in doxorubicin cytotoxicity by carvedilol inhibition of P-glycoprotein activity

Acquired resistance to chemotherapy is a major problem during cancer treatment. One mechanism for drug resistance is overexpression of the MDR1 (multidrug resistance) gene encoding for the transmembrane efflux pump, P-glycoprotein (P-gp). The calcium channel blocker verapamil has been shown to reverse cellular drug resistance by inhibiting P-gp drug efflux. This study evaluated whether the new antihypertensive drug carvedilol influenced doxorubicin (Dox) cytotoxicity and P-gp activity in a P-gp-expressing cell line compared to a non-expressing subline. Verapamil (10 micromol/L), and even more markedly, carvedilol (10 micromol/L) increased cellular uptake of P-gp-transported calcein of a P-gp-expressing breast cancer cell line (Hs578T-Dox). In the subline (Hs578T) not expressing P-gp, no effects of carvedilol or verapamil on calcein uptake were seen. Carvedilol and verapamil (10 micromol/L) reduced the LD50 (dose which results in the death of half the number of cells) of the Hs578T-Dox subline from 200 mg/L to approx. 10 mg/L Dox, whereas the LD50 of the Hs578T subline was only marginally affected. Carvedilol (10 micromol/L) reduced P-gp activity approximately twice as effectively as verapamil at an equimolar concentration. Carvedilol did not affect pyrogallol cytotoxicity and pyrogallol was without effect on calcein accumulation of the Hs578T-Dox cell line, indicating the lack of antioxidative properties affecting P-gp activity and associated toxicity of the drug. The results suggest that carvedilol has the clinical potential to reverse tumour MDR involving the efflux protein P-gp.     

Brain-targeted delivery of paclitaxel using glutathione-coated nanoparticles for brain cancers

Paclitaxel is not effective for treatment of brain cancers because it cannot cross the blood–brain barrier (BBB) due to efflux by P-glycoprotein (P-gp). In this work, glutathione-coated poly-(lactide-co-glycolide) (PLGA) nanoparticles (NPs) of paclitaxel were developed for brain targeting for treatment of brain cancers. P-gp ATPase assay was used to evaluate the NP as potential substrates. The NP showed a particle size suitable for BBB permeation (particle size around 200?nm) and higher cellular uptake of the NP was demonstrated in RG2 cells. The P-gp ATPase assay suggested that the NP were not substrate for P-gp and would not be effluxed by P-gp present in the BBB. The in vitro release profile of the NP exhibited no initial burst release and showed sustained drug release. The proposed coated NP showed significantly higher cytotoxicity in RG2 cells compared with uncoated NP (p?≤?0.05). Tubulin immunofluorescent study showed higher cell death by the NP due to increased microtubule stabilization. In vivo brain uptake study in mice showed higher brain uptake of the NP containing coumarin-6 compared with solution. The proposed brain-targeted NP delivery of paclitaxel could be an effective treatment for the brain cancers.     

Co-delivery of rapamycin- and piperine-loaded polymeric nanoparticles for breast cancer treatment

P-glycoprotein (P-gp) efflux is the major cause of multidrug resistance (MDR) in tumors when using anticancer drugs, moreover, poor bioavailability of few drugs is also due to P-gp efflux in the gut. Rapamycin (RPM) is in the clinical trials for breast cancer treatment, but its P-gp substrate property leads to poor oral bioavailability and efficacy. The objective of this study is to formulate and evaluate nanoparticles of RPM, along with a chemosensitizer (piperine, PIP) for improved oral bioavailability and efficacy. Poly(d,l-lactide-co-glycolide) (PLGA) was selected as polymer as it has moderate MDR reversal activity, which may provide additional benefits. The nanoprecipitation method was used to prepare PLGA nanoparticles with particle size below 150?nm, loaded with both drugs (RPM and PIP). Prepared nanoparticles showed sustained in vitro drug release for weeks, with initial release kinetics of zero order with non-Fickian transport, subsequently followed by Higuchi kinetics with Fickian diffusion. An everted gut sac method was used to study the effect of P-gp efflux on drug transport. This reveals that the uptake of the RPM (P-gp substrate) has been increased in the presence of chemosensitizer. Pharmacokinetic studies showed better absorption profile of RPM from polymeric nanoparticles compared to its suspension counterpart and improved bioavailability of 4.8-folds in combination with a chemosensitizer. An in vitro cell line study indicates higher efficacy of nanoparticles compared to free drug solution. Results suggest that the use of a combination of PIP with RPM nanoparticles would be a promising approach in the treatment of breast cancer.     

Enhanced cellular association of paclitaxel delivered in chitosan-PLGA particles

We have previously demonstrated that the cellular association, cytotoxicity, and in vivo anti-tumor efficacy of paclitaxel are significantly greater when delivered in PLGA microparticles compared to nanoparticles. The purpose of this research is to test the hypothesis that mucoadhesive chitosan promotes adhesion of PLGA particles to mucus on the tumor epithelium, resulting in enhanced cellular association and cytotoxicity of paclitaxel. PLGA particles containing paclitaxel or Bodipy(?) were prepared and chitosan was either adsorbed or chemically conjugated to the particle surface. The cellular association and cytotoxicity of paclitaxel in 4T1 cells was determined. A 4-10 fold increase in cellular association of paclitaxel was observed when chitosan was adsorbed or conjugated to the PLGA particles. Chitosan-conjugated PLGA microparticles were most cytotoxic with an IC(50) value of 0.77 μM. Confocal microscopy demonstrated that chitosan-PLGA microparticles adhered to the surface of 4T1 cells. Pretreatment of either 4T1 cells or chitosan-PLGA particles with mucin resulted in significant increase in cellular association of paclitaxel. A linear correlation was established between theoretical amount of chitosan used and experimentally determined amount of chitosan adsorbed or conjugated to PLGA nanoparticles. In conclusion, cellular association and cytotoxicity of paclitaxel was significantly enhanced when delivered in chitosan-PLGA particles.     

Interactions of Human P-glycoprotein with Simvastatin, Simvastatin Acid, and Atorvastatin

PURPOSE: In this study, P-glycoprotein (P-gp) mediated efflux of simvastatin (SV), simvastatin acid (SVA), and atorvastatin (AVA) and inhibition of P-gp by SV, SVA, and AVA were evaluated to assess the role of P-gp in drug interactions. METHODS: P-gp mediated efflux of SV, SVA, and AVA was determined by directional transport across monolayers of LLC-PK1 cells and LLC-PK1 cells transfected with human MDR1. Inhibition of P-gp was evaluated by studying the vinblastine efflux in Caco-2 cells and in P-gp overexpressing KBV1 cells at concentrations of SV, SVA, and AVA up to 50 microM. RESULTS: Directional transport studies showed insignificant P-gp mediated efflux of SV, and moderate P-gp transport [2.4-3.8 and 3.0-6.4 higher Basolateral (B) to Apical (A) than A to B transport] for SVA and AVA, respectively. Inhibition studies did not show the same trend as the transport studies with SV and AVA inhibiting P-gp (IC50 -25-50 microM) but SVA not showing any inhibition of P-gp. CONCLUSIONS: The moderate level of P-gp mediated transport and low affinity of SV, SVA, and AVA for P-gp inhibition compared to systemic drug levels suggest that drug interactions due to competition for P-gp transport is unlikely to be a significant factor in adverse drug interactions. Moreover, the inconsistencies between P-gp inhibition studies and P-gp transport of SV, SVA, and AVA indicate that the inhibition studies are not a valid means to identify statins as Pgp substrates.     

Nanohybrid systems of non-ionic surfactant inserting liposomes loading paclitaxel for reversal of multidrug resistance

Three new nanohybrid systems of non-ionic surfactant inserting liposomes loading paclitaxel (PTX) (NLPs) were prepared to overcome multidrug resistance (MDR) in PTX-resistance human lung cancer cell line. Three non-ionic surfactants, Solutol HS 15 (HS-15), pluronic F68 (PF-68) and cremophor EL (CrEL) were inserted into liposomes by film hydration method to form NLPs with an average size of around 110, 180 and 110 nm, respectively. There was an obvious increase of rhodamin 123 (Rh123) accumulation in A549/T cells after treated with nanohybrid systems loading Rh123 (NLRs) when compared with free Rh123 or liposomes loading Rh123 without surfactants (LRs), which indicated the significant inhibition effects of NLRs on drug efflux. The P-gp detection and ATP determination demonstrated that BNLs could not only interfere P-gp expression on the membrane of drug resistant cells, but also decrease ATP level in the cells. The cytotoxicity of NLPs against A549/T cells was higher than PTX loaded liposomes without surfactants (LPs), and the best result was achieved after treated with NLPs2. The apoptotic assay and the cell cycle analysis showed that NLPs could induce more apoptotic cells in drug resistant cells when compared with LPs. These results suggested that NLPs could overcome MDR by combination of drug delivery, P-gp inhibition and ATP depletion, and showed potential for treatment of MDR.     

Folate and CD44 Receptors Dual-Targeting Hydrophobized Hyaluronic Acid Paclitaxel-Loaded Polymeric Micelles for Overcoming Multidrug Resistance and Improving Tumor Distribution

The drug efflux mediated by P-glycoprotein (P-gp) transporter is one of the important factors responsible for multidrug resistance (MDR), and then the efficient intracellular drug delivery is an important strategy to overcome MDR of tumor cells. We describe and compare CD44 receptor single-targeting and folate (FA), CD44 receptors dual-targeting hyaluronic acid-octadecyl (HA-C₁₈) micellar formulations to overcome MDR of tumor cells and to improve tumor distribution. In comparison with Taxol solution, the cytotoxicity of paclitaxel (PTX) loaded in HA-C₁₈ and FA-HA-C₁₈ micelles against drug-resistant tumor cells was improved significantly because of the increased intracellular delivery by active receptor-mediated endocytosis. Compared with the single-targeting micelles, dual-targeting micelles possessed better MDR-overcoming performance. Pharmacokinetic study demonstrated HA-C₁₈ and FA-HA-C₁₈ PTX-loaded micelles possessed much longer circulation and moderately larger AUC than Taxol solution. Above all, the tumor distribution in MCF-7 tumor-bearing mice of PTX encapsulated in HA-C₁₈ and FA-HA-C₁₈ micelles were 2.8 and 4.0 times higher than that of Taxol solution. It was concluded that dual-targeting FA–HA-C₁₈ micelles demonstrate excellent MDR-overcoming ability and improved tumor distribution, and provide a novel effective nanoplatform for anticancer drug delivery in cancer chemotherapy. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.     

异博定逆转肝癌细胞多药耐药的研究

肿瘤细胞对化疗药物产生多药耐药(MDR)是肿瘤化疗失败的主要原因,为了寻找克服肿瘤细胞多药耐药的方法,将异博定加入体外培养诱导的人肝癌细胞多药耐药株SMMC-7721/ADM中,MTT法检测显示异博定增加了化疗药对SMMC-7721/ADM细胞的毒性,并随异博定浓度的增加其逆转活性也增强,(VPL25μg/ml时,SMMC-7721/ADM的活细胞为65％,而VPL20μg/ml时,SMMC-7721/ADM的活细胞率为39％,两者有显著差异)。流式细胞技术显示异博定使耐药细胞表面P-糖蛋白的浓度降低和耐药细胞内柔红霉素的浓度增加(P-gp由70.13下降到22.68,DNR浓度由133上升到163),因此研究表明异博定逆转肿瘤细胞的多药耐药机理是通过使肿瘤细胞表面的P-糖蛋白表达减少,增加肿瘤细胞内的化疗药物浓度而起作用。     

Discovery of a daunorubicin analogue that exhibits potent antitumor activity and overcomes P-gp-mediated drug resistance

Anthracyclines are considered to be some of the most effective anticancer drugs for cancer therapy. However, drug resistance and cardiotoxicity of anthracyclines limit their clinical application. We hypothesize that direct modifications of the sugar moiety of anthracyclines avert P-glycoprotein (P-gp) recognition and efflux, increase drug intracellular concentration in cancer cells, and thus overcome P-gp-mediated drug resistance. Daunorubicin (DNR) analogues with sugar modifications were synthesized by directly transforming the amino group of DNR to an azido group or triazole group. Molecular docking showed that the lead compound (3'-azidodaunorubicin, ADNR) averts P-gp binding, while daunorubicin (DNR) extensively interacts with multidrug-resistance (MDR) protein through H-bonds and electrostatic interactions. FACS assay demonstrated that these new compounds abolished P-gp drug efflux and accumulated high intracellular concentration in the drug-resistant leukemia K562/Dox. P-gp inhibition by CsA confirmed that these new analogues are no longer P-gp substrates. ADNR exhibited potent anticancer activity in both drug-sensitive (K562) and drug-resistant leukemia cells (K562/Dox), with a 25-fold lower drug resistance index than DNR. An in vivo xenograft model demonstrated that ADNR showed more than 2.5-fold higher maximum growth inhibition rate against drug-resistant cancers and significant improvement for animal survival rate versus DNR. No significant body weight reduction in mice was observed for ADNR at the maximum tolerable dose, as compared to more than 70% body weight reduction for DNR. These data suggest that sugar modifications of anthracyclines avert P-gp binding, abolish P-gp-mediated drug efflux, increase intracellular drug concentration, and thus overcome P-gp-mediated drug resistance in cancer therapy.     

Korean red ginseng extract enhances paclitaxel distribution to mammary tumors and its oral bioavailability by P-glycoprotein inhibition

1.?Drug efflux by P-glycoprotein (P-gp) is a common resistance mechanism of breast cancer cells to paclitaxel, the primary chemotherapy in breast cancer. As a means of overcoming the drug resistance-mediated failure of paclitaxel chemotherapy, the potential of Korean red ginseng extract (KRG) as an adjuvant chemotherapy has been reported only in in vitro. Therefore, we assessed whether KRG alters P-gp mediated paclitaxel efflux, and therefore paclitaxel efficacy in in vitro and vivo models.

2.?KRG inhibited P-gp protein expression and transcellular efflux of paclitaxel in MDCK-mdr1 cells, but KRG was not a substrate of P-gp ATPase. In female rats with mammary tumor, the combination of paclitaxel with KRG showed the greater reduction of tumor volumes, lower P-gp protein expression and higher paclitaxel distribution in tumors, and greater oral bioavailability of paclitaxel than paclitaxel alone.

3.?From these results, KRG increased systemic circulation of oral paclitaxel and its distribution to tumors via P-gp inhibition in rats and under the current study conditions.     

Sensitization of ABCB1 overexpressing cells to chemotherapeutic agents by FG020326 via binding to ABCB1 and inhibiting its function

The effectiveness of chemotherapeutic treatment is usually limited by the overexpression of adenosine triphosphate binding cassette (ABC) transporters, which mediate multidrug resistance (MDR) by acting as efflux pumps to remove chemotherapeutic agents from MDR cancer cells. Thus, the inhibition of ABC transporters may represent a promising strategy to reverse MDR. This study was to characterize the actions of FG020326, a newly synthesized triaryl-substituted imidazole derivative, to reverse MDR in vitro and in vivo. FG020326 significantly potentiated the cytotoxicity of paclitaxel, doxorubicin, and vincristine in the ABCB1 (P-glycoprotein, P-gp) overexpressing cells KBv200 and MCF-7/adr, but not in the ABCB1 negative parental cell lines KB and MCF-7. However, FG020326 did not alter the cytotoxicity of the aforementioned drugs in ABCC1 (MRP1), ABCC4 (MRP4), ABCG2 (BCRP) and LRP overexpressing cell lines, KB-CV60, NIH3T3/MRP4-2, S1-M1-80 and SW1573/2R120, respectively. FG020326, following p.o. administration, was present in concentrations sufficient for reversal of MDR in mice. The co-administration of FG020326 with paclitaxel or vincristine significantly enhanced the antitumor activity of these drugs without significantly increasing toxicity in the mice bearing the KBv200 cell xenografts. In addition, FG020326, at concentrations that reversed MDR, did not significantly affect the activity of CYP3A4 or alter the pharmacokinetic profile of paclitaxel after co-administration with paclitaxel. FG020326 produced a significant concentration-dependent displacement of [³H]azidopine and inhibition of efflux of drug from cells. Furthermore, FG020326 was co-localized with ABCB1 in cell membranes. Hence, FG020326 is characterized as a third generation MDR modulator that holds great promise for the treatment of cancer patients with ABCB1-mediated MDR.     

Development of EGFR-targeted polymer blend nanocarriers for combination paclitaxel/lonidamine delivery to treat multi-drug resistance in human breast and ovarian tumor cells

Multi-drug resistant (MDR) cancer is a significant clinical obstacle and is often implicated in cases of recurrent, nonresponsive disease. Targeted nanoparticles were made by synthesizing a poly(D,L-lactide-co-glycolide)/poly(ethylene glycol)/epidermal growth factor receptor targeting peptide (PLGA/PEG/EGFR-peptide) construct for incorporation in poly(epsilon-caprolactone) (PCL) nanoparticles. MDR was induced in a panel of nine human breast and ovarian cancer cell lines using hypoxia. EGFR-targeted polymer blend nanoparticles were shown to actively target EGFR overexpressing cell lines, especially upon induction of hypoxia. The nanoparticles were capable of sustained drug release. Combination therapy with lonidamine and paclitaxel significantly improved the therapeutic index of both drugs. Treatment with a nanoparticle dose of 1 μM paclitaxel/10 μM lonidamine resulted in less than 10% cell viability for all hypoxic/MDR cell lines and less than 5% cell viability for all normoxic cell lines. Comparatively, treatment with 1 μM paclitaxel alone was the approximate IC?? value of the MDR cells while treatment with lonidamine alone had very little effect. The PLGA/PEG/EGFR-peptide delivery system actively targets a MDR cell by exploiting the expression of EGFR. This system treats MDR by inhibiting the Warburg effect and promoting mitochondrial binding of pro-apoptotic Bcl-2 proteins (lonidamine), while hyperstabilizing microtubules (paclitaxel). This nanocarrier system actively targets a MDR associated phenotype (EGFR receptor overexpression), further enhancing the therapeutic index of both drugs and potentiating the use of lonidamine/paclitaxel combination therapy in the treatment of MDR cancer.