Multidrug resistance (MDR) in cancer. Mechanisms, reversal using modulators of MDR and the role of MDR modulators in influencing the pharmacokinetics of anticancer drugs

Stress Introduction Rate Alters the Benefit of AcrAB-TolC Efflux Pumps

Stress tolerance studies are typically conducted in an all-or-none fashion. However, in realistic settings-such as in clinical or metabolic engineering applications-cells may encounter stresses at different rates. Therefore, how cells tolerate stress may depend on its rate of appearance. To address this, we studied how the rate of stress introduction affects bacterial stress tolerance by focusing on a key stress response mechanism. Efflux pumps, such as AcrAB-TolC of Escherichia coli, are membrane transporters well known for the ability to export a wide variety of substrates, including antibiotics, signaling molecules, and biofuels. Although efflux pumps improve stress tolerance, pump overexpression can result in a substantial fitness cost to the cells. We hypothesized that the ideal pump expression level would involve a rate-dependent trade-off between the benefit of pumps and the cost of their expression. To test this, we evaluated the benefit of the AcrAB-TolC pump under different rates of stress introduction, including a step, a fast ramp, and a gradual ramp. Using two chemically diverse stresses, the antibiotic chloramphenicol and the jet biofuel precursor pinene, we assessed the benefit provided by the pumps. A mathematical model describing these effects predicted the benefit as a function of the rate of stress introduction. Our findings demonstrate that as the rate of introduction is lowered, stress response mechanisms provide a disproportionate benefit to pump-containing strains, allowing cells to survive beyond the original inhibitory concentrations.IMPORTANCE Efflux pumps are ubiquitous in nature and provide stress tolerance in the cells of species ranging from bacteria to mammals. Understanding how pumps provide tolerance has far-reaching implications for diverse fields, from medicine to biotechnology. Here, we investigated how the rate of stressor appearance impacts tolerance. We focused on two distinct substrates of AcrAB-TolC efflux pumps, the antibiotic chloramphenicol and the biofuel precursor pinene. Interestingly, tolerance is highly dependent on the rate of stress introduction. Therefore, it is important to consider not only the total quantity of a stressor but also the rate at which it is applied. The implications of this work are significant because environments are rarely static; antibiotic concentrations change during dosing, and metabolic engineering processes change with time.

pH-triggered surface charge-switchable polymer micelles for the co-delivery of paclitaxel/disulfiram and overcoming multidrug resistance in cancer

Multidrug resistance (MDR) remains a major challenge for providing effective chemotherapy for many cancer patients. To address this issue, we report an intelligent polymer-based drug co-delivery system which could enhance and accelerate cellular uptake and reverse MDR. The nanodrug delivery systems were constructed by encapsulating disulfiram (DSF), a P-glyco-protein (P-gp) inhibitor, into the hydrophobic core of poly(ethylene glycol)-block-poly(l-lysine) (PEG-b-PLL) block copolymer micelles, as well as 2,3-dimethylmaleic anhydride (DMA) and paclitaxel (PTX) were grafted on the side chain of l-lysine simultaneously. The surface charge of the drug-loaded micelles represents as negative in plasma (pH 7.4), which is helpful to prolong the circulation time, and in a weak acid environment of tumor tissue (pH 6.5-6.8) it can be reversed to positive, which is in favor of their entering into the cancer cells. In addition, the carrier could release DSF and PTX successively inside cells. The results of in vitro studies show that, compared to the control group, the DSF and PTX co-loaded micelles with charge reversal exhibits more effective cellular uptake and significantly increased cytotoxicity of PTX to MCF-7/ADR cells which may be due to the inhibitory effect of DSF on the efflux function of P-gp. Accordingly, such a smart pH-sensitive nanosystem, in our opinion, possesses significant potential to achieve combinational drug delivery and overcome drug resistance in cancer therapy.

Schisandrin A reverses doxorubicin-resistant human breast cancer cell line by the inhibition of P65 and Stat3 phosphorylation

BACKGROUND

Multidrug resistance (MDR) in breast cancer therapy occurs frequently. Thus, anti-MDR agents from natural products or synthetic compounds were tested extensively. We have also explored the reverse effect and mechanism of Schisandrin A (Sch A), a natural product, on MCF-7 breast cancer doxorubicin (DOX)-resistant subline MCF-7/DOX.

METHODS

MTT assay was performed to measure the viability of MCF-7 cells to assess the reverse effect of Sch A. Western blot analysis was used to study the protein levels. Laser scanning confocal microscopy was performed to detect the intercellular DOX and Rhodamine 123 accumulation. The qRT-PCR was used to analysis the target gene expression. Dual-luciferase reporter assay was performed to test the transcriptional activity of P-glycoprotein (P-gp).

RESULTS

Sch A, at the concentration of 20 µM, showed selective reverse effect (better than the positive control, verapamil at 5 µM) on MCF-7/DOX cell line but not on BEL-7402/DOX, Hep G2/DOX, and K-562/DOX cells. In addition, Sch A enhanced DOX-induced cleavage of Caspase-9 and PARP levels by increasing intracellular DOX accumulation and inhibiting P-gp function. Furthermore, Sch A selectively suppressed P-gp at gene and protein levels in MCF-7/DOX cells which express high level of MDR1 but not MRP1, MRP3, or BCRP. Besides, Sch A showed inhibitory effect on P-gp transcriptional activity. Sch A significantly reduced p-IκB-α (Ser32) and p-Stat3 (Tyr705) levels which mediate P-gp expression. In addition, Stat3 knockdown enhanced the reverse effect of siP65. The combined effect of siStat3 and siP65 was better than Sch A single treatment in MCF-7/DOX cells.

CONCLUSION

Sch A specifically reverses P-gp-mediated DOX resistance in MCF-7/DOX cells by blocking P-gp, NF-κB, and Stat3 signaling. Inhibition of P65 and Stat3 shows potent anti-MDR effect on MCF-7/DOX cells.

Expression of multidrug resistance proteins in retinoblastoma

AIM

To elucidate the mechanism of multidrug resistance in retinoblastoma, and to acquire more insights into in vivo drug resistance.

METHODS

Three anticancer drug resistant Y79 human RB cells were generated against vincristine, etoposide or carboplatin, which are used for conventional chemotherapy in RB. Primary cultures from enucleated eyes after chemotherapy (PCNC) were also prepared. Their chemosensitivity to chemotherapeutic agents (vincristine, etoposide and carboplatin) were measured using MTT assay. Western blot analysis was performed to evaluate the expression of p53, Bcl-2 and various multidrug resistant proteins in retinoblastoma cells.

RESULTS

Following exposure to chemotherapeutic drugs, PCNC showed less sensitivity to drugs. No significant changes observed in the p53 expression, whereas Bcl-2 expression was found to be increased in the drug resistant cells as well as in PCNC. Increased expression of P-glycoprotein (P-gp) was observed in drug resistant Y79 cells; however there was no significant change in the expression of P-gp found between primary cultures of primarily enucleated eyes and PCNC. Multidrug resistance protein 1 (Mrp-1) expression was found to be elevated in the drug resistant Y79 cells as well as in PCNC. No significant change in the expression of lung resistance associated protein (Lrp) was observed in the drug resistant Y79 cells as well as in PCNC.

CONCLUSION

Our results suggest that multidrug resistant proteins are intrinsically present in retinoblastoma which causes treatment failure in managing retinoblastoma with chemotherapy.

"Bottom-Up" Construction of Hyperbranched Poly(prodrug-co-photosensitizer) Amphiphiles Unimolecular Micelles for Chemo-Photodynamic Dual Therapy

Despite the great advantages of chemo-photodynamic combination therapy, tedious synthesis steps and laborious purification procedures make the fabrication of chemo-photodynamic combined therapeutic platforms rather difficult. In this study, we develop a facile "bottom-up" strategy to fabricate hyperbranched poly(prodrug-co-photosensitizer) amphiphiles, h-P(CPTMA-co-BYMAI)-b-POEGMA (hPCBE), for chemo-photodynamic dual therapy. The easily prepared hPCBE possess a bottom-up-constructed hydrophobic core h-P(CPTMA-co-BYMAI) (hPCB) direct copolymerized from reduction-responsive CPT prodrug monomer (CPTMA) and boron dipyrromethene-based photosensitizer monomer (BYMAI), as well as a biocompatible shell polymerized from hydrophilic monomers. Because of the covalently interconnected core-shell structure, hPCBE exists as unimolecular micelles in aqueous solution and exhibits excellent structural stability under dilution condition. The hPCBE micelles can be effectively internalized by MCF-7 cells and release CPT triggered by the reductive milieu. In addition, photosensitizer moieties embedded in the hPCB core could generate singlet oxygen (¹O₂) effectively under irradiation, endowing hPCBE with the boosting of chemotherapeutic efficacy. As compared to the single chemotherapy of hyperbranched polyprodrug amphiphiles h-PCPTMA-b-POEGMA (hPCE) and photodynamic therapy of hyperbranched polyphotosensitizer amphiphiles h-PBYMAI-b-POEGMA (hPBE), hPCBE shows higher in vitro cytotoxicity. We expect that our approach will further boost research on the design of multifunctional drug delivery systems via the facile "bottom-up" strategy.

Tomentodione M sensitizes multidrug resistant cancer cells by decreasing P-glycoprotein via inhibition of p38 MAPK signaling

In this study, we investigated the mechanism by which tomentodione M (TTM), a novel natural syncarpic acid-conjugated monoterpene, reversed multi-drug resistance (MDR) in cancer cells. TTM increased the cytotoxicity of chemotherapeutic drugs such as docetaxel and doxorubicin in MCF-7/MDR and K562/MDR cells in a dose- and time-dependent manner. TTM reduced colony formation and enhanced apoptosis in docetaxel-treated MCF-7/MDR and K562/MDR cells, and it enhanced intracellular accumulation of doxorubicin and rhodamine 123 in MDR cancer cells by reducing drug efflux mediated by P-gp. TTM decreased expression of both P-gp mRNA and protein by inhibiting p38 MAPK signaling. Similarly, the p38 MAPK inhibitor SB203580 reversed MDR in cancer cells by decreasing P-gp expression. Conversely, p38 MAPK-overexpressing MCF-7 and K562 cells showed higher P-gp expression than controls. These observations indicate that TTM reverses MDR in cancer cells by decreasing P-gp expression via p38 MAPK inhibition.

Modulation of P-glycoprotein by Stemona alkaloids in human multidrug resistance leukemic cells and structural relationships

BACKGROUND

Multidrug resistance (MDR) is a major reason for the failure of chemotherapy in the treatment of cancer patients. P-gp over-expression in MDR cancer cells is a multifactorial phenomenon with biochemical resistance mechanisms. Stemofoline (STF), isolated from Stemona bukillii, has been reported to be an MDR reversing compound.

PURPOSE

This study investigated whether other Stemona alkaloids that had been purified from Stemonaceae plants exerted MDR modulation activity.

METHODS

MTT assay was performed to determine the MDR reversing property of the alkaloids. Modulation of P-gp function by these compounds was investigated using cell cycle analysis and P-gp fluorescent substrate accumulation assays. P-gp expression was determined by Western blot analysis. We preliminarily examined the safety of these compounds in normal human fibroblasts and human peripheral blood mononuclear cells (PBMCs) using the MTT assay, and in red blood cells (human and rat) through in vitro hemolysis assays.

RESULTS

Three of the eight alkaloids tested, isostemofoline (ISTF), 11Z -didehydrostemofoline (11Z-DSTF) and 11E-didehydrostemofoline (11E-DSTF), enhanced the chemotherapeutic sensitivity of MDR leukemic K562/Adr cells, which overexpressed P-gp. The P-gp functional studies showed that these three alkaloids increased the accumulation of P-gp substrates, calcein-AM (C-AM) and rhodamine123 (Rho 123) in K562/Adr cells, while this effect was not seen in drug sensitive parental K562 cells. Whereas, the alkaloids did not alter P-gp expression as was determined by Western blotting analysis.

CONCLUSION

The alkaloids reversed MDR via the inhibition of P-gp function. For pharmaceutical safety testing, the alkaloids were found to be not toxic to normal human fibroblasts and PBMCs. Moreover, the effective compounds did not induce hemolysis in either human or rat erythrocytes. These compounds may be introduced as potential candidate molecules for treating cancers exhibiting P-gp-mediated MDR.

Polysaccharide-based nanoparticles for co-loading mitoxantrone and verapamil to overcome multidrug resistance in breast tumor

The aim of this study was to evaluate the potential of polyelectrolyte complex nanoparticles (PENPs) based on hyaluronic acid/chitosan hydrochloride (HA/HCS) for co-loading mitoxantrone (MTO) and verapamil (VRP) to overcome multidrug resistance in breast tumors. PENPs co-loaded with MTO and VRP (MTO-VRP-PENPs) were affected by the method of preparation, molecular weight of HA, mass ratios and initial concentrations of HA/HCS, pH, and drug quantities. Optimized MTO-VRP-PENPs were ~209 nm in size with a zeta potential of approximately -24 mV. Encapsulation efficiencies (%) of MTO and VRP were 98.33%±0.27% and 44.21%±8.62%, respectively. MTO and VRP were successfully encapsulated in PENPs in a molecular or amorphous state. MTO-VRP-PENPs showed significant cytotoxicity in MCF-7/ADR cells in contrast to MTO-loaded PENPs (MTO-PENPs). The reversal index of MTO-VRP-PENPs was 13.25 and 10.33 times greater than that of the free MTO and MTO-PENPs, respectively. In conclusion, MTO-VRP-PENPs may serve as a promising carrier to overcome tumor drug resistance.

Combinatorial therapeutic approaches with RNAi and anticancer drugs using nanodrug delivery systems

RNA interference (RNAi) is emerging as a powerful approach in cancer treatment. siRNA is an important RNAi tool that can be designed to specifically silence the expression of genes involved in drug resistance and chemotherapeutic inactivity. Combining siRNA and other therapeutic agents can overcome the multidrug resistance (MDR) phenomenon by simultaneously silencing genes and enhancing chemotherapeutic activity. Moreover, the therapeutic efficiency of anticancer drugs can be significantly improved by additive or synergistic effects induced by siRNA and combined therapies. Co-delivery of these diverse anticancer agents, however, requires specially designed nanocarriers. This review highlights the recent trends in siRNA/anticancer drug co-delivery systems under the major categories of liposomes/lipid, polymeric and inorganic nanoplatforms. The objective is to discuss the strategies for nanocarrier-based co-delivery systems using siRNA/anticancer drug combinations, emphasizing various siRNA targets that help overcome MDR and enhance therapeutic efficiency.

Tumor-targeting templated silica nanoparticles as a dual-drug delivery system for anti-angiogenic ovarian cancer therapy

The present study indicated the successful construction of a silica nanoparticle (SLN)-based drug delivery system (DDS) for the tumor-targeted co-delivery of two anti-angiogenic drugs, candesartan (CD) and trastuzumab (Tra), for ovarian cancer therapy via different anti-angiogenic mechanisms using hyaluronic acid (HA)/Tra/CD/SLNs. In vitro and in vivo anti-angiogenic assays indicated that CD and Tra exert beneficial functions on suppressing cancer angiogenesis, and exhibited significantly enhanced effects compared with the angiotensin stimulated group (P<0.01). CD and Tra co-delivery also significantly increased the anti-angiogenic effect compared with applying either drug alone (P<0.01). Furthermore, HA on the surface of the DDS was demonstrated to reduce the cytotoxicity of the DDS and also endowed the particles with an advanced tumor-homing property in vitro and in vivo. The present results revealed that HA/Tra/CD/SLNs may be a preferable formulation for anti-angiogenic ovarian cancer therapy.

Targeting P-glycoprotein: Investigation of piperine analogs for overcoming drug resistance in cancer

P-glycoprotein (P-gp) is a drug transporter that effluxes chemotherapeutic drugs and is implicated in the development of resistance of cancer cells to chemotherapeutic drugs. To date, no drug has been approved to inhibit P-gp and restore chemotherapy efficacy. Moreover, majority of the reported inhibitors have high molecular weight and complex structures, making it difficult to understand the basic structural requirement for P-gp inhibition. In this study, two structurally simple, low molecular weight piperine analogs Pip1 and Pip2 were designed and found to better interact with P-gp than piperine in silico. A one step, acid-amine coupling reaction between piperic acid and 6,7-dimethoxytetrahydroisoquinoline or 2-(3,4-dimethoxyphenyl)ethylamine afforded Pip1 and Pip2, respectively. In vitro testing in drug resistant P-gp overexpressing KB (cervical) and SW480 (colon) cancer cells showed that both analogs, when co-administered with vincristine, colchicine or paclitaxel were able to reverse the resistance. Moreover, accumulation of P-gp substrate (rhodamine 123) in the resistant cells, a result of alteration of the P-gp efflux, was also observed. These investigations suggest that the natural product analog - Pip1 ((2E,4E)-5-(benzo[d][1,3]dioxol-5-yl)-1-(6,7-dimethoxy-3,4-dihydroisoquinolin-2(1 H)-yl)penta-2,4-dien-1-one) - is superior to piperine and could inhibit P-gp function. Further studies are required to explore the full potential of Pip1 in treating drug resistant cancer.

Targeting of CCN2 suppresses tumor progression and improves chemo-sensitivity in urothelial bladder cancer

Urothelial bladder cancer (UBC) is the most common urinary neoplasm in China. CCN family protein 2 (CCN2), a cysteine-rich matricellular protein, is abnormally expressed in several cancer types and involved in tumor progression or chemo-resistance. However, detailed expression patterns and effects of CCN2 in UBC still remain unknown. We found that down-regulation of CCN2 suppressed proliferation, migration and invasion of UBC cells in vitro and targeting of CCN2 decelerated xenograft growth in vivo. When treated with mitomycin C (MMC), CCN2-scilencing UBC cells showed lower survival and higher apoptotic rates and these effects were probably mediated via inactivation of Akt and Erk pathways. We also demonstrated the clinical significance of CCN2 expression, which was higher in UBC tissues and associated with advanced tumor stage and high pathologic grade. Taken together, our data suggest that CCN2 is an oncogene in UBC and might serve as a matricellular target for improving chemotherapeutic efficacy.

Cepharanthine hydrochloride reverses P‑glycoprotein-mediated multidrug resistance in human ovarian carcinoma A2780/Taxol cells by inhibiting the PI3K/Akt signaling pathway

Ovarian cancer has the highest mortality rate among gynecologic malignant tumors. The major obstacle to treatment success is multidrug resistance (MDR) to chemotherapy drugs. Cepharanthine hydrochloride (CH), a natural alkaloid-derived compound, has shown MDR reversal potency in several tumor cell lines; however, the molecular mechanism is not entirely known. In the present study, we assessed whether CH sensitized malignant cells to chemotherapy drugs in ovarian cancer and explored the relevant mechanism. We found that CH reduced the IC50 value of paclitaxel and increased intracellular rhodamine-123 accumulation in human ovarian cancer A2780/Taxol cells in a concentration-dependent manner. Reverse transcription polymerase chain reaction and western blot assay demonstrated that CH inhibited MDR1 expression as indicated by reduced mRNA and protein levels in A2780/Taxol cells. In addition, the inhibitory effect was strengthened after CH was combined with the specific PI3K/Akt signaling pathway inhibitor LY294002. Furthermore, p‑Akt expression decreased gradually with the concentration of CH (2, 4 and 8 µM). Taken together, these findings indicated that CH reversed P‑glycoprotein-mediated MDR in A2780/Taxol cells by inhibiting the PI3K/Akt signaling pathway.

Trackable Mitochondria-Targeting Nanomicellar Loaded with Doxorubicin for Overcoming Drug Resistance

Multidrug resistance (MDR) has been recognized as a major obstacle to successful chemotherapy for cancer in the clinic. In recent years, more and more nanoscaled drug delivery systems (DDS) are constructed to modulate drug efflux protein (P-gp) and deliver chemotherapeutic drugs for overcoming MDR. Among them, d-α-tocopheryl polyethylene glycol succinate (TPGS) has been widely used as a drug carrier due to its capability of inhibiting overexpression of P-gp and good amphiphilicity favorable for improving permeation and long-circulation property of DDS. In the present work, a novel kind of mitochondria-targeting nanomicelles-based DDS is developed to integrate chemotherapeutics delivery with fluorescence imaging functionalities on a comprehensive nanoplatform. The mitochondria-targeting nanomicelles are prepared by self-assembly of triphenylphosphine (TPP)-modified TPGS and fluorescent carbon quantum dots (CQDs) in an n-hexane/H₂O mixed solution, named CQDs-TPGS-TPP. Notably, although the drug loading content of doxorubicin (DOX) in the as-prepared nanomicelles is as low as 3.4%, the calculated resistant index (RI) is greatly decreased from 66.23 of free DOX to 7.16 of DOX-loaded nanomicelles while treating both parental MCF-7 cells and drug-resistant MCF-7/ADR cells. Compared with free DOX, the penetration efficiency of DOX-loaded nanomicelles in three-dimensional multicellular spheroids (MCs) of MCF-7/ADR is obviously increased. Moreover, the released DOX from the nanomicelles can cause much more damage to cells of drug-resistant MCs. These results demonstrate that our constructed mitochondria-targeting nanomicelles-based DDS have potential application in overcoming MDR of cancer cells as well as their MCs that mimic in vivo tumor tissues. The MDR-reversal mechanism of the DOX-loaded CQDs-TPGS-TPP nanomicelles is also discussed.

Elacridar, a third-generation ABCB1 inhibitor, overcomes resistance to docetaxel in non-small cell lung cancer

Docetaxel is a third-generation chemotherapeutic drug that is widely used in the treatment of patients with non-small cell lung cancer (NSCLC). However, the majority of patients with NSCLC eventually acquire resistance to the treatment. In the present study, the mechanism of acquired resistance to docetaxel treatment in lung cancer cells was investigated. The three NSCLC cell lines, H1299 with wild-type epidermal growth factor receptor (EGFR), EGFR-mutant HCC4006 and HCC827, and experimentally established docetaxel-resistant (DR) cells, H1299-DR, HCC827-DR, and HCC4006-DR were used with stepwise increases in concentrations of docetaxel. It was demonstrated that the established cell lines showed resistance to docetaxel and EGFR-tyrosine kinase inhibitors (TKIs). Molecular analysis revealed that all of the resistant cell lines highly expressed ATP binding cassette subfamily B member 1 (ABCB1), which is also known as P-glycoprotein or MDR1. Furthermore, HCC827-DR and HCC4006-DR cells exhibited a cancer stem cell-like marker and epithelial-to-mesenchymal transition features, respectively. Elacridar (GF120918), a third-generation inhibitor of ABCB1, was able to overcome resistance to docetaxel. Additionally, knockdown of ABCB1 using small interfering RNA (si)-ABCB1 recovered sensitivity to docetaxel. However, elacridar and si-ABCB1 could not recover sensitivity to EGFR-TKIs in established resistant cells. The results of the present study revealed that docetaxel-resistant NSCLC cells also acquired cross-resistance to EGFR-TKI therapy through mechanisms other than ABCB1, that ABCB1 serves an important role in acquired resistance to docetaxel in lung cancer, and that combination therapy with elacridar can overcome ABCB1-mediated docetaxel resistance.

Design, synthesis and antiproliferative activity of decarbonyl luotonin analogues

A small library of benzimidazole-fused pyrrolo[3,4-b]quinoline has been synthesized from readily available benzimidazole 2-carbaldehyde and various substituted arylamines in good to excellent yields utilizing an intramolecular Povarov reaction catalyzed by boron trifluoride diethyl etharate as the key final step. The compounds thus synthesized can be considered as decarbonyl analogues of the anticancer alkaloid luotonin A and were evaluated in a DNA relaxation assay for their ability to inhibit human topoisomerase I. Interestingly, two of the compounds showed a remarkable activity that is comparable to that of the standard drug camptothecin. The compounds were also evaluated for their cytotoxic effect in four highly aggressive human cancer cell lines, namely KB, MDA-MB231 (breast), LNCap (prostate), and HT1080 (fibrosarcoma). Some of the compounds obtained showed promising cytotoxicities for these four cell lines.

Natural Products as Alternative Choices for P-Glycoprotein (P-gp) Inhibition

Multidrug resistance (MDR) is regarded as one of the bottlenecks of successful clinical treatment for numerous chemotherapeutic agents. Multiple key regulators are alleged to be responsible for MDR and making the treatment regimens ineffective. In this review, we discuss MDR in relation to P-glycoprotein (P-gp) and its down-regulation by natural bioactive molecules. P-gp, a unique ATP-dependent membrane transport protein, is one of those key regulators which are present in the lining of the colon, endothelial cells of the blood brain barrier (BBB), bile duct, adrenal gland, kidney tubules, small intestine, pancreatic ducts and in many other tissues like heart, lungs, spleen, skeletal muscles, etc. Due to its diverse tissue distribution, P-gp is a novel protective barrier to stop the intake of xenobiotics into the human body. Over-expression of P-gp leads to decreased intracellular accretion of many chemotherapeutic agents thus assisting in the development of MDR. Eventually, the effectiveness of these drugs is decreased. P-gp inhibitors act by altering intracellular ATP levels which are the source of energy and/or by affecting membrane contours to increase permeability. However, the use of synthetic inhibitors is known to cause serious toxicities. For this reason, the search for more potent and less toxic P-gp inhibitors of natural origin is underway. The present review aims to recapitulate the research findings on bioactive constituents of natural origin with P-gp inhibition characteristics. Natural bioactive constituents with P-gp modulating effects offer great potential for semi-synthetic modification to produce new scaffolds which could serve as valuable investigative tools to recognize the function of complex ABC transporters apart from evading the systemic toxicities shown by synthetic counterparts. Despite the many published scientific findings encompassing P-gp inhibitors, however, this article stand alones because it provides a vivid picture to the readers pertaining to Pgp inhibitors obtained from natural sources coupled with their mode of action and structures. It provides first-hand information to the scientists working in the field of drug discovery to further synthesise and discover new P-gp inhibitors with less toxicity and more efficacies.

Enhancing Tumor Cell Response to Multidrug Resistance with pH-Sensitive Quercetin and Doxorubicin Conjugated Multifunctional Nanoparticles

Classical chemotherapy uses chemotherapeutic agents as a mainstay of anticancer treatment. However, the development of multidrug resistance to chemotherapy limits the effectiveness of current cancer treatment. Nanosized bioconjugates combining a chemotherapeutic agent with a pharmacological approach may improve the curative effect of chemotherapeutic agents. Herein I addressed this issue by describing the synthesis, and testing of, pH-responsive Fe3O4@SiO2(FITC)-BTN/QUR/DOX multifunctional nanoparticles. The particles were designed to modulate resistance-mediating factors and to potentiate the efficacy of DOX against chemoresistance. The physicochemical properties of the nanoparticles were characterized based on the combination of several techniques: dynamic light scattering (DLS), zeta-potential measurement, Fourier transform infrared spectroscopy (FTIR), electron microscopy techniques (SEM and STEM with EDX) and an in vitro pH-dependent release study. Cellular uptake and cytotoxicity experiments demonstrated enhanced intracellular delivery and retention of nanoparticles in the cytoplasm and efficient reduction of cancer cell viability in drug-resistant lung carcinoma A549/DOX cell lines. This did not affect internalization and viability of an immortalized human lung epithelial cell line BEAS-2B. Moreover, proapoptotic and antiproliferative studies showed that Fe3O4@SiO2(FITC)-BTN/QUR/DOX nanoparticles can promote apoptosis, inhibit tumor cell proliferation, and enhance the chemotherapeutic effects of DOX against multidrug resistance. These results confirm that this multifunctional platform possesses significant synergy between QUR and DOX and is promising for development as an antitumor treatment in cancer therapy.

Effectiveness of imatinib mesylate over etoposide in the treatment of sensitive and resistant chronic myeloid leukaemia cells in vitro

Chronic myeloid leukaemia (CML) is a form of leukaemia derived from the myeloid cell lineage. Imatinib mesylate, the breakpoint cluster region-abelson murine leukeamia kinase inhibitor, is a specific reagent used in the clinical treatment of CML. The DNA topoisomerase II inhibitor, etoposide, is also employed as a therapeutic, though it is used to a lesser extent. The present study aims to evaluate the effects of CML-targeted therapy, utilising imatinib mesylate and etoposide in the in vitro treatment of parental sensitive and adriamycin-resistant CML in the K562 and K562/ADM cell lines, respectively. Preliminary work involved the screening of multidrug resistant (MDR) gene expression, including MDR1, MRP1 and B-cell lymphoma 2 (BCL-2) at the mRNA levels. The sensitive and resistant CML cell lines expressed the MRP1 gene, though the sensitive K562 cells expressed low, almost undetectable levels of MDR1 and BCL-2 genes relative to the K562/ADM cells. Following treatment with imatinib mesylate or etoposide, the IC50 for imatinib mesylate did not differ between the sensitive and resistant cell lines (0.492±0.024 and 0.378±0.029, respectively), indicating that imatinib mesylate is effective in the treatment of CML regardless of cell chemosensitivity. However, the IC50 for etoposide in sensitive K562 cells was markedly lower than that of K562/ADM cells (50.6±16.5 and 194±8.46 µM, respectively), suggesting that the higher expression levels of MDR1 and/or BCL-2 mRNA in resistant cells may be partially responsible for this effect. This is supported by terminal deoxynucleotidyl transferase dUTP nick-end labeling data, whereby a higher percentage of apoptotic cells were found in the sensitive and resistant K562 cells treated with imatinib mesylate (29.3±0.2 and 31.9±16.7%, respectively), whereas etoposide caused significant apoptosis of sensitive K562 cells (18.3±8.35%) relative to K562/ADM cells (5.17±3.3%). In addition, the MDR genes in K562/ADM cells were knocked down by short interfering RNAs. The percentage knockdowns were 15.4% for MRP1, 17.8% for MDR and 30.7% for BCL-2, which resulted in a non-significant difference in the half maximal inhibitory concentration value of K562/ADM cells relative to K562 cells upon treatment with etoposide.

Twist1 confers multidrug resistance in colon cancer through upregulation of ATP-binding cassette transporters

Multidrug resistance is a major problem in colon cancer treatment. However, its molecular mechanisms remain unclear. Recently, the epithelial-mesenchymal transition (EMT) in anticancer drug resistance has attracted increasing attention. This study investigated whether vincristine treatment induces EMT and promotes multidrug resistance in colon cancer. The result showed that vincristine treatment increases the expression of several ATP-binding cassette transporters in invasive human colon adenocarcinoma cell line (HCT-8). Vincristine-resistant HCT-8 cells (HCT-8/V) acquire a mesenchymal phenotype, and thus its migratory and invasive ability are increased both in vitro and in vivo. The master transcriptional factors of EMT, especially Twist1, were significantly increased in the HCT-8/V cell line. Moreover, the ectopic expression of Twist1 increased the chemoresistance of HCT-8 cells to vincristine and increased the expression levels and promoter activities of ABCB1 and ABCC1. Furthermore, Twist1 silencing reverses the EMT phenotype, enhances the chemosensitivity of HCT-8/ V cells to anticancer agents in vitro and in vivo, and downregulates the expression of ABCB1 and ABCC1. Twist1-mediated promotion of ABCB1 and ABCC1 expression levels plays an important role in the drug resistance of colon cancer cells.

Mechanism Underlying the Reversal of Drug Resistance in P-Glycoprotein-Expressing Leukemia Cells by Pinoresinol and the Study of a Derivative

P-glycoprotein (P-gp) is a membrane protein associated with multidrug resistance (MDR) due to its key role in mediating the traffic of chemotherapeutic drugs outside cancer cells, leading to a cellular response that hinders efforts toward successful therapy. With the aim of finding agents that circumvent the MDR phenotype mediated by P-gp, 15 compounds isolated from native and naturalized plants of Argentina were screened. Among these, the non-cytotoxic lignan (±) pinoresinol successfully restored sensitivity to doxorubicin from 7 μM in the P-gp overexpressed human myelogenous leukemia cells, Lucena 1. This resistance-reversing effect was confirmed by competitively increasing the intracellular doxorubicin accumulation and by significantly inhibiting the efflux of doxorubicin and, to a lesser extent, that of rhodamine 123. The activity obtained was similar to that observed with verapamil. No such results were observed in the sensitive parental K562 cell line. To gain deeper insight into the mode of action of pinoresinol, its effect on P-gp function and expression was examined. The docking simulations indicated that the lignan bound to P-gp at the apex of the V-shaped transmembrane cavity, involving transmembrane helices 4, 5, and 6, and partially overlapped the binding region of tariquidar, which was used as a positive control. These results would shed some light on the nature of its interaction with P-gp at molecular level and merit further mechanistic and kinetic studies. In addition, it showed a maximum 29% activation of ATP hydrolysis and antagonized verapamil-stimulated ATPase activity with an IC₅₀ of 20.9 μM. On the other hand, pinoresinol decreased the presence of P-gp in the cell surface. Derivatives of pinoresinol with improved activity were identified by docking studies. The most promising one, the non-cytotoxic 1-acetoxypinoresinol, caused a reversion of doxorubicin resistance from 0.11 μM and thus higher activity than the lead compound. It also caused a significant increase in doxorubicin accumulation. Results were similar to those observed with verapamil. The results obtained positioned these compounds as potential candidates for effective agents to overcome P-gp-mediated MDR, leading to better outcomes for leukemia chemotherapy.

Mechanisms of drug resistance in colon cancer and its therapeutic strategies

Drug resistance develops in nearly all patients with colon cancer, leading to a decrease in the therapeutic efficacies of anticancer agents. This review provides an up-to-date summary on over-expression of ATP-binding cassette (ABC) transporters and evasion of apoptosis, two representatives of transport-based and non-transport-based mechanisms of drug resistance, as well as their therapeutic strategies. Different ABC transporters were found to be up-regulated in colon cancer, which can facilitate the efflux of anticancer drugs out of cancer cells and decrease their therapeutic effects. Inhibition of ABC transporters by suppressing their protein expressions or co-administration of modulators has been proven as an effective approach to sensitize drug-resistant cancer cells to anticancer drugs in vitro. On the other hand, evasion of apoptosis observed in drug-resistant cancers also results in drug resistance to anticancer agents, especially to apoptosis inducers. Restoration of apoptotic signals by BH3 mimetics or epidermal growth factor receptor inhibitors and inhibition of cancer cell growth by alternative cell death pathways, such as autophagy, are effective means to treat such resistant cancer types. Given that the drug resistance mechanisms are different among colon cancer patients and may change even in a single patient at different stages, personalized and specific combination therapy is proposed to be more effective and safer for the reversal of drug resistance in clinics.

Nanotechnology for the treatment of melanoma skin cancer

Melanoma is the most aggressive type of skin cancer and has very high rates of mortality. An early stage melanoma can be surgically removed, with a survival rate of 99%. This literature review intends to elucidate the possibilities to treat melanoma skin cancer using hybrid nanofibers developed by advanced electrospinning process. In this review we have shown that the enhanced permeability and retention is the basis for using nanotechnology, aiming topical drug delivery. The importance of the detection of skin cancer in the early stages is directly related to non-metastatic effects and survival rates of melanoma cells. Inhibitors of protein kinase are already available in the market for melanoma treatment and are approved by the FDA; these agents are cobimetinib, dabrafenib, ipilimumab, nivolumab, trametinib, and vemurafenib. We also report a case study involving two different approaches for targeting melanoma skin cancer therapy, namely, magnetic-based core–shell particles and electrospun mats.

The efficacy of WGA modified daunorubicin anti-resistant liposomes in treatment of drug-resistant MCF-7 breast cancer

BACKGROUND

Breast cancer is the most common malignancy and remains a leading cause of cancer-related deaths in female. Chemotherapy failure of breast cancer is mainly associated with multidrug resistance of cancer cells.

PURPOSE

The WGA modified daunorubicin anti-resistant liposomes were developed for circumventing the multidrug resistance and eliminating cancer cells.

METHODS

WGA was modified on liposomal surface for increasing the intracellular uptake. Tetrandrine was inserted into the phospholipid bilayer for reversing cancer drug-resistance, and daunorubicin was encapsulated in liposomal aqueous core as an anticancer agent. Evaluations were performed on MCF-7 cells, MCF-7/ADR cells and xenografts of MCF-7/ADR cells.

RESULTS

In vitro results showed that WGA modified daunorubicin anti-resistant liposomes exhibited suitable physicochemical properties, significantly increased intracellular uptake in both MCF-7 cells and MCF-7/ADR cells, and circumvented the multidrug resistance via inhibiting P-gp. In vivo results demonstrated that the targeting liposomes showed a long-circulatory effect in blood system, and could remarkably accumulate at the tumor location. The involved action mechanisms for the enhanced anticancer efficacy were activation of pro-apoptotic proteins (Bax and Bok), apoptotic enzymes (caspase 8, caspase 9 and caspase 3).

CONCLUSION

The established WGA modified daunorubicin anti-resistant liposomes could provide a potential strategy for treating resistant MCF-7 breast cancer.

Influence of microRNAs and Long Non-Coding RNAs in Cancer Chemoresistance

Innate and acquired chemoresistance exhibited by most tumours exposed to conventional chemotherapeutic agents account for the majority of relapse cases in cancer patients. Such chemoresistance phenotypes are of a multi-factorial nature from multiple key molecular players. The discovery of the RNA interference pathway in 1998 and the widespread gene regulatory influences exerted by microRNAs (miRNAs) and other non-coding RNAs have certainly expanded the level of intricacy present for the development of any single physiological phenotype, including cancer chemoresistance. This review article focuses on the latest research efforts in identifying and validating specific key molecular players from the two main families of non-coding RNAs, namely miRNAs and long non-coding RNAs (lncRNAs), having direct or indirect influences in the development of cancer drug resistance properties and how such knowledge can be utilised for novel theranostics in oncology.

miR-506 enhances the sensitivity of human colorectal cancer cells to oxaliplatin by suppressing MDR1/P-gp expression

OBJECTIVES

Chemoresistance development represents a major obstacle to the successful treatment of colorectal cancer (CRC). The aim of this study was to elucidate the mechanism by which miR-506 reverses oxaliplatin chemoresistance in CRC.

METHODS

In this study, miR-506 levels were measured in 74 patients with colon cancer via quantitative real-time polymerase chain reaction (qRT-PCR) and in situ hybridization (ISH). We subsequently analysed the relationship between miR-506 expression and CRC patient survival via the Kaplan-Meier method. MTT assay demonstrated the fractional survival rates and cell viability of HCT116-OxR, HCT116-OxR-miR-Ctrl and HCT116-OxR-miR-506 cells treated with oxaliplatin at different concentrations. Cell proliferation and apoptosis were assessed via flow cytometry (FCM) analysis and apoptosis assay. MDR1 mRNA expression and P-gp protein expression were assessed via qRT-PCR and Western blotting (WB) respectively. Immunofluorescence (IF) staining demonstrated P-gp expression in HCT116-OxR and HCT116-OxR-miR-506 cells. qRT-PCR and WB were used to detect Wnt/β-catenin pathway activity after miR-506 overexpression.

RESULTS

In the present study, in ISH and qRT-PCR results demonstrated that miR-506 is weakly expressed in chemoresistant CRC tissues. The low miR-506 expression group exhibited lower 5-year OS and lower 5-year RFS than the high miR-506 expression group. miR-506 overexpression inhibited cell growth and increased oxaliplatin-induced cell apoptosis in HCT116-OxR cells, as shown via FCM and apoptosis assay. We subsequently noted low MDR1/P-gp expression in HCT116-OxR-miR-506 cells via qRT-PCR, WB and IF. Lastly, we demonstrated low MDR1/P-gp expression in HCT116-OxR-miR-506 cells via inhibition of the Wnt/β-catenin by WB, MTT and FCM analysis.

CONCLUSION

Taken together, the findings of our study demonstrate that miR-506 overexpression in HCT116-OxR cells enhances oxaliplatin sensitivity by inhibiting MDR1/P-gp expression via down-regulation of the Wnt/β-catenin pathway and thus provide a rationale for the development of miRNA-based strategies to reverse oxaliplatin resistance in CRC cells.

A Prodrug of Two Approved Drugs, Cisplatin and Chlorambucil, for Chemo War Against Cancer

Cancer cells maintain normal mitochondrial glutathione as one of the defense mechanisms to inhibit mitochondrial membrane polarization and hence apoptosis. A combinational therapeutic modality Platin-Cbl, a prodrug of FDA-approved chemotherapeutic agents, cisplatin and chlorambucil (Cbl), was synthesized and characterized to explore the potential of this compound to initiate chemo war on cancer cells using the active drugs, cisplatin and Cbl, when delivered to the cellular power house mitochondrion using a targeted nanoparticle designed to get associated with this organelle. Platin-Cbl demonstrated significantly high cytotoxic activity across a number of tumor cell lines as well as in a cisplatin-resistant cancer cell line compared with cisplatin or its mixture with Cbl suggesting its unique potency in cisplatin-resistant tumors. A mitochondria-targeted nanoparticle formulation of Platin-Cbl allowed for its efficacious mitochondrial delivery. In vitro studies documented high potency of Platin-Cbl nanoparticle formulations. Cisplatin-resistant cells upon treatment with Platin-Cbl were still able to manage energy production to a certain extent via fatty acid pathway; the advantage of using T-Platin-Cbl-NP is that this nanoparticle treatment causes impairment of all metabolic pathways in cisplatin-resistant cells forcing the cells to undergo efficient apoptosis. This study highlights a combination of several beneficial effects for a cascade of events to overcome resistance associated with single drug therapy. Mol Cancer Ther; 16(4); 625-36. ©2017 AACR.

Quercetin-Based Modified Porous Silicon Nanoparticles for Enhanced Inhibition of Doxorubicin-Resistant Cancer Cells

One of the most challenging obstacles in nanoparticle's surface modification is to achieve the concept that one ligand can accomplish multiple purposes. Upon such consideration, 3-aminopropoxy-linked quercetin (AmQu), a derivative of a natural flavonoid inspired by the structure of dopamine, is designed and subsequently used to modify the surface of thermally hydrocarbonized porous silicon (PSi) nanoparticles. This nanosystem inherits several advanced properties in a single carrier, including promoted anticancer efficiency, multiple drug resistance (MDR) reversing, stimuli-responsive drug release, drug release monitoring, and enhanced particle-cell interactions. The anticancer drug doxorubicin (DOX) is efficiently loaded into this nanosystem and released in a pH-dependent manner. AmQu also effectively quenches the fluorescence of the loaded DOX, thereby allowing the use of the nanosystem for monitoring the intracellular drug release. Furthermore, a synergistic effect with the presence of AmQu is observed in both normal MCF-7 and DOX-resistant MCF-7 breast cancer cells. Due to the similar structure as dopamine, AmQu may facilitate both the interaction and internalization of PSi into the cells. Overall, this PSi-based platform exhibits remarkable superiority in both multifunctionality and anticancer efficiency, making this nanovector a promising system for anti-MDR cancer treatment.

Effect and mechanism of resveratrol on drug resistance in human bladder cancer cells

Multidrug resistance (MDR) is a significant barrier to the effective treatment of bladder cancer. In order to improve the management of bladder cancer, it is crucial to identify strategies that may reverse MDR. The effects of three herbal medicines, ginsenoside Rh2, (−)-epigallocatechin gallate (EGCG) and resveratrol (RES) on bladder cancer were determined. The effect of these three herbal medicines against the drug resistance in adriamycin (ADM)-resistant pumc-91 cells (pumc-91/ADM) was assessed using the Cell Counting Kit-8 cell proliferation assay system. Cell cycle distribution analysis was performed using flow cytometry following treatment with RES. The mRNA and protein expression levels of multidrug resistance protein 1 (MRP1), lung resistance protein (LRP), glutathione S-transferase (GST), B cell leukemia/lymphoma-2 (BCL-2) and topoisomerase-II (Topo-II) were evaluated using reverse transcription-quantitative polymerase chain reaction and immunofluorescence, respectively. RES enhanced the cytotoxicity of anticancer agents on pumc-91/ADM cells; however, Rh2 and EGCG were unable to induce a similar effect. Additionally, RES treatment led to S phase cell cycle arrest accompanied by a decrease in the number of cells in the G1 phase. A significant decrease of MRP1, LRP, GST, BCL-2 levels and an increase of Topo-II levels were observed in RES groups compared with the control group. RES effectively reversed ADM resistance in pumc-91/ADM cells and the underlying molecular mechanism may be associated with the alteration of MRP1, LRP, GST, BCL-2 and Topo-II expression levels. Therefore, RES may be a potential candidate for reversing drug resistance in bladder cancer chemotherapy.

Large-scale classification of P-glycoprotein inhibitors using SMILES-based descriptors

P-glycoprotein (Pgp) inhibition has been considered as an effective strategy towards combating multidrug-resistant cancers. Owing to the substrate promiscuity of Pgp, the classification of its interacting ligands is not an easy task and is an ongoing issue of debate. Chemical structures can be represented by the simplified molecular input line entry system (SMILES) in the form of linear string of symbols. In this study, the SMILES notations of 2254 Pgp inhibitors including 1341 active, and 913 inactive compounds were used for the construction of a SMILE-based classification model using CORrelation And Logic (CORAL) software. The model provided an acceptable predictive performance as observed from statistical parameters consisting of accuracy, sensitivity and specificity that afforded values greater than 70% and MCC value greater than 0.6 for training, calibration and validation sets. In addition, the CORAL method highlighted chemical features that may contribute to increased and decreased Pgp inhibitory activities. This study highlights the potential of CORAL software for rapid screening of prospective compounds from a large chemical space and provides information that could aid in the design and development of potential Pgp inhibitors.

Curcumin as a Modulator of P-Glycoprotein in Cancer: Challenges and Perspectives

Multidrug resistance (MDR) presents a serious challenge to the efficiency of cancer treatment, and may be associated with the overexpression of drug efflux pumps. P-glycoprotein (P-gp) is a drug efflux pump often found overexpressed in cases of acquired MDR. Nevertheless, there are no P-gp inhibitors being used in the current clinical practice, due to toxicity problems, drug interactions, or pharmacokinetic issues. Therefore, it is important to identify novel inhibitors of P-gp activity or expression. Curcumin is a secondary metabolite isolated from the turmeric of Curcuma longa L. which has been associated with several biological activities, particularly P-gp modulatory activity (by inhibiting both P-gp function and expression). However, curcumin shows extensive metabolism and instability, which has justified the recent and intensive search for analogs of curcumin that maintain the P-gp modulatory activity but have enhanced stability. This review summarizes and compares the effects of curcumin and several curcumin analogs on P-glycoprotein function and expression, emphasizing the potential of these molecules for the possible development of safe and effective inhibitors of P-gp to overcome MDR in human cancer.

Antitumor activities on HL-60 human leukemia cell line, molecular docking, and quantum-chemical calculations of some sulfonamide-benzoxazoles

We previously synthesized some novel benzoxazole derivatives-containing sulfonamide. In this study, the compounds were investigated for their antitumor activities against the HL-60 human leukemia cells, using the MTT assay. Moreover, quantum chemical calculations using the DFT methods were applied for understanding the difference in antitumor activity. Additionally, molecular docking into active site of the DNA Topo II enzyme was performed on 3QX3. PDB file in order to find out possible mechanism of antitumor effect. According to all obtained results showed that compounds 1b, 1c, and 1d could be potential drug candidates as new antitumor agents, and are promising for cancer therapy.

Inorganic Nanocarriers Overcoming Multidrug Resistance for Cancer Theranostics

Cancer multidrug resistance (MDR) could lead to therapeutic failure of chemotherapy and radiotherapy, and has become one of the main obstacles to successful cancer treatment. Some advanced drug delivery platforms, such as inorganic nanocarriers, demonstrate a high potential for cancer theranostic to overcome the cancer-specific limitation of conventional low-molecular-weight anticancer agents and imaging probes. Specifically, it could achieve synergetic therapeutic effects, demonstrating stronger killing effects to MDR cancer cells by combining the inorganic nanocarriers with other treatment manners, such as RNA interference and thermal therapy. Moreover, the inorganic nanocarriers could provide imaging functions to help monitor treatment responses, e.g., drug resistance and therapeutic effects, as well as analyze the mechanism of MDR by molecular imaging modalities. In this review, the mechanisms involved in cancer MDR and recent advances of applying inorganic nanocarriers for MDR cancer imaging and therapy are summarized. The inorganic nanocarriers may circumvent cancer MDR for effective therapy and provide a way to track the therapeutic processes for real-time molecular imaging, demonstrating high performance in studying the interaction of nanocarriers and MDR cancer cells/tissues in laboratory study and further shedding light on elaborate design of nanocarriers that could overcome MDR for clinical translation.

Fabrication and in vitro characterization of gadolinium-based nanoclusters for simultaneous drug delivery and radiation enhancement

We report the synthesis of a gadolinium hydroxide (Gd(OH)3) nanorod based doxorubicin (Dox) delivery system that can enhance both magnetic resonance imaging contrast and radiation sensitivity. A simple and cost effective wet-chemical method was utilized in the presence of manganese (Mn) ions and Dox to produce the Gd(OH)3:Mn·Dox nanocluster structure. The Gd(OH)3:Mn·Dox nanocluster was composed of Mn-doped Gd(OH)3 nanorods arranged in parallel with Dox as a linker molecule between the adjacent nanorods. No other studies have utilized Dox as both the linker and therapeutic molecule in a nanostructure to date. The Gd(OH)3 nanorod is reported to have no significant cellular or in vivo toxicity, which makes it an ideal base material for this biomedical application. The Gd(OH)3:Mn·Dox nanocluster exhibited paramagnetic behavior and was stable in a colloidal solution. The nanocluster also enabled high Dox loading capacity and specifically released Dox in a sustained and pH-dependent manner. The positively charged Gd(OH)3:Mn·Dox nanoclusters were readily internalized into MDA-MB-231 breast cancer cells via endocytosis, which resulted in intracellular release of Dox. The released Dox in cells was effective in conferring cytotoxicity and inhibiting proliferation of cancer cells. Furthermore, a synergistic anticancer effect could be observed with radiation treatment. Overall, the Gd(OH)3:Mn·Dox nanocluster drug delivery system described herein may have potential utility in clinics as a multifunctional theranostic nanoparticle with combined benefits in both diagnosis and therapy in the management of cancer.

Cancer-Targeted Nanotheranostics: Recent Advances and Perspectives

Cancer-targeted nanotechnology is experiencing the trend of finding new materials with multiple functions for imaging and therapeutic applications. With the rapid development of the related fields, there exists a large number of reports regarding theranostic nanomedicine, decreasing the gap between cancer diagnosis and treatment with minimized separate comprehensions. In order to present an overview on the cancer-targeted nanotheranostics, we first describe their essential building blocks, including platforms, therapeutic agents and imaging agents, and then the recently rapidly developed multimodal theranostic systems. Finally we discuss the major challenges and the perspectives of future development of nanotheranostics toward clinical translations and personalized nanomedicine.

Semi-synthetic ocotillol analogues as selective ABCB1-mediated drug resistance reversal agents

Overexpression of ATP-Binding Cassette transporters leads to multidrug resistance in cancer cells and results in the failure of chemotherapy. In this in-vitro study, we investigated whether or not (20S, 24R/S)-epoxy-12β, 25-dihydroxy-dommarane-3β-amine (ORA and OSA), a pair of semi-synthetic ocotillol analogue epimers, could inhibit the ABCB1 transporter. ORA (1 μM and 3 μM) significantly reversed the resistance to paclitaxel and vincristine in ABCB1-overexpressing SW620/Ad300 and HEK/ABCB1 cells, whereas OSA had no significant effects. In addition, ORA (3 μM) significantly increased the intracellular accumulation of [3H]-paclitaxel by suppressing the efflux function of ABCB1. Meanwhile, both ORA (3 μM) and OSA (3 μM) did not significantly alter the expression level or the subcellular location of ABCB1 protein. Moreover, the ABCB1 ATPase study suggested that ORA had a stronger stimulatory effect on the ATPase activity than OSA. ORA also exhibited a higher docking score as compared with OSA inside transmembrane domain of ABCB1. Overall, we concluded that ORA reverse ABCB1-mediated MDR by competitively inhibiting the ABCB1 drug efflux function.

Design, syntheses, characterization, and cytotoxicity studies of novel heterobinuclear oxindolimine copper(II)-platinum(II) complexes

Herein, the design and syntheses of two new mononuclear oxindolimine-copper(II) (1 and 2) and corresponding heterobinuclear oxindolimine Cu(II)Pt(II) complexes (3 and 4), are described. All the isolated complexes were characterized by spectroscopic techniques (UV/Vis, IR, EPR), in addition to elemental analysis and mass spectrometry. Cyclic voltammetry (CV) measurements showed that in all cases, one-electron quasi-reversible waves were observed, and ascribed to the formation of corresponding copper(I) complexes. Additionally, waves related to oxindolimine ligand reduction was verified, and confirmed using analogous oxindolimine-Zn(II) complexes. The Pt(IV/II) reduction, and corresponding oxidation, for complexes 3 and 4 occurred at very close values to those observed for cisplatin. By complementary fluorescence studies, it was shown that glutathione (GSH) cannot reduce any of these complexes, under the experimental conditions (room temperature, phosphate buffer 50mM, pH7.4), using an excess of 20-fold [GSH]. All these complexes showed characteristic EPR spectral profile, with parameters values g_ǁ>g_⊥ suggesting an axially distorted environment around the copper(II) center. Interactions with calf thymus-DNA, monitored by circular dichroism (CD), indicated different effects modulated by the ligands. Finally, the cytotoxicity of each complex was tested toward different tumor cells, in comparison to cisplatin, and low values of IC₅₀ in the range 0.6 to 4.0μM were obtained, after 24 or 48h incubation at 37°C. The obtained results indicate that such complexes can be promising alternative antitumor agents.