Treatment Of Multidrug-resistant Cancer Research Articles

PH-sensitive micelles self-assembled from star-shaped TPGS copolymers with ortho ester linkages for enhanced MDR reversal and chemotherapy

TPGS approved by FDA can be used as a P-gp inhibitor to effectively reverse multi-drug resistance (MDR) and as an anticancer agent for synergistic antitumor effects. However, the comparatively high critical micelle concentration (CMC), low drug loading (DL) and poor tumor target limit its further clinical application. To overcome these drawbacks, the pH-sensitive star-shaped TPGS copolymers were successfully constructed via using pentaerythritol as the initial materials, ortho esters as the pH-triggered linkages and TPGS active-ester as the terminated MDR material. The amphiphilic star-shaped TPGS copolymers could self-assemble into free and doxorubicin (DOX)-loaded micelles at neutral aqueous solutions. The micelles exhibited the lower CMC (8.2 × 10−5 mg/ml), higher DL (10.8%) and long-term storage and circulation stability, and showed enhanced cellular uptake, apoptosis, cytotoxicity, and growth inhibition for in vitro MCF-7/ADR and/or MCF-7/ADR multicellular spheroids and in vivo MCF-7/ADR tumors via efficiently targeted drug release at tumoral intracellular pH (5.0), MDR reversal of TPGS, and synergistic effect of DOX and TPGS. Therefore, the pH-sensitive micelles self-assembled from star-shaped TPGS copolymers with ortho ester linkages are potentially useful to clinically transform for enhanced MDR cancer treatment.

PH and ROS sequentially responsive podophyllotoxin prodrug micelles with surface charge-switchable and self-amplification drug release for combating multidrug resistance cancer

Multidrug resistance (MDR) is one of the main reasons for tumor chemotherapy failure. Podophyllotoxin (PPT) has been reported that can suppress MDR cancer cell growth; however, effective delivery of PPT to MDR cancer cells is challenged by cascaded bio-barriers. To effectively deliver PPT to MDR cancer cells, a PPT polymeric prodrug micelle (PCDMA) with the charge-conversion capability and self-acceleration drug release function are fabricated, which is composed of a pH and reactive oxygen species (ROS) sequentially responsive PPT-polymeric prodrug and an ROS generation agent, cucurbitacin B (CuB). After reach to tumor tissue, the surface charge of PCDMA could rapidly reverse to positive in the tumor extracellular environment to promote cellular uptake. Subsequently, the PCDMA could be degraded to release PPT and CuB in response to an intracellular high ROS condition. The released CuB is competent for generating ROS, which in turn accelerates the release of PPT and CuB. Eventually, the released PPT could kill MDR cancer cells. The in vitro and in vivo studies demonstrated that PCDMA was effectively internalized by cancer cells and produces massive ROS intracellular, rapid release drug, and effectively overcame MDR compared with the control cells, due to the tumor-specific weakly acidic and ROS-rich environment. Our results suggest that the pH/ROS dual-responsive PCDMA micelles with surface charge-reversal and self-amplifying ROS-response drug release provide an excellent platform for potential MDR cancer treatment.

The Role of NIR Fluorescence in MDR Cancer Treatment: From Targeted Imaging to Phototherapy.

Multidrug Resistance (MDR) is defined as a cross-resistance of cancer cells to various chemotherapeutics and has been demonstrated to correlate with drug efflux pumps. Visualization of drug efflux pumps is useful to pre-select patients who may be insensitive to chemotherapy, thus preventing patients from unnecessary treatment. Near-Infrared (NIR) imaging is an attractive approach to monitoring MDR due to its low tissue autofluorescence and deep tissue penetration. Molecular NIR imaging of MDR cancers requires stable probes targeting biomarkers with high specificity and affinity. This article aims to provide a concise review of novel NIR probes and their applications in MDR cancer treatment. Recently, extensive research has been performed to develop novel NIR probes and several strategies display great promise. These strategies include chemical conjugation between NIR dyes and ligands targeting MDR-associated biomarkers, native NIR dyes with inherent targeting ability, activatable NIR probes as well as NIR dyes loaded nanoparticles. Moreover, NIR probes have been widely employed for photothermal and photodynamic therapy in cancer treatment, which combine with other modalities to overcome MDR. With the rapid advancing of nanotechnology, various nanoparticles are incorporated with NIR dyes to provide multifunctional platforms for controlled drug delivery and combined therapy to combat MDR. The construction of these probes for MDR cancers targeted NIR imaging and phototherapy will be discussed. Multimodal nanoscale platform which integrates MDR monitoring and combined therapy will also be encompassed. We believe these NIR probes project a promising approach for diagnosis and therapy of MDR cancers, thus holding great potential to reach clinical settings in cancer treatment.

The Effects of Traditional Chinese Medicine on P-Glycoprotein-Mediated Multidrug Resistance and Approaches for Studying the Herb-P-Glycoprotein Interactions.

As a member of the ATP-dependent membrane transport proteins, P-Glycoprotein (P-gp) is known to pump substrates out of cells using an ATP-dependent mechanism. The overexpression of P-gp in tumor cells reduces the intracellular drug concentrations, which decreases the efficacy of extensive antitumor drugs and leads to multidrug resistance (MDR) clinically. The combination of anticancer drugs with P-gp inhibitor has been an attractive and promising strategy to reverse MDR in cancer treatment. However, nonspecific or nonselective distribution of P-gp inhibitors to nontarget organs is one of the most fatal shortcomings in clinical application. Thus, there is an urgent need for effective and nontoxic MDR reversal agents, particularly in P-gp-mediated MDR. Traditional Chinese medicine (TCM) natural products may prove less toxic for use in P-gp inhibition to promote MDR reversal. P-gp modulatory effects have been previously demonstrated using selected TCM, including the flavonoid, alkaloid, terpenoid, coumarin, and quinonoid compounds, and some Chinese medicine extracts. Moreover, the approaches for screening active components from TCM are necessary, and these approaches face challenges. At present, the approaches to study the interaction between TCM and P-gp are divided into in vitro, in vivo, and in silico methods. This review will provide an overview and update on the role of TCM in overcoming P-gp-mediated MDR and the approaches to study the interaction between TCM and P-gp. SIGNIFICANCE STATEMENT: This review summarized some traditional Chinese medicines identified to have a modulatory effect on P-gp, including flavonoids, alkaloids, terpenoids, coumarins, quinonoid compounds, and some Chinese medicine extracts, and it introduced possible mechanisms. The approaches to study the interaction between TCM and P-gp are divided into in vitro, in vivo, and in silico methods.

CXL146, a Novel 4H-Chromene Derivative, Targets GRP78 to Selectively Eliminate Multidrug-Resistant Cancer Cells

The 78-kDa glucose-regulated protein (GRP78), an endoplasmic reticulum (ER) chaperone, is a master regulator of the ER stress. A number of studies revealed that high levels of GRP78 protein in cancer cells confer multidrug resistance (MDR) to therapeutic treatment. Therefore, drug candidate that reduces GRP78 may represent a novel approach to eliminate MDR cancer cells. Our earlier studies showed that a set of 4H-chromene derivatives induced selective cytotoxicity in MDR cancer cells. In the present study, we elucidated its selective mechanism in four MDR cancer cell lines with one lead candidate (CXL146). Cytotoxicity results confirmed the selective cytotoxicity of CXL146 toward the MDR cancer cell lines. We noted significant overexpression of GRP78 in all four MDR cell lines compared with the parental cell lines. Unexpectedly, CXL146 treatment rapidly and dose-dependently reduced GRP78 protein in MDR cancer cell lines. Using human leukemia (HL) 60/mitoxantrone (MX) 2 cell line as the model, we demonstrated that CXL146 treatment activated the unfolded protein response (UPR); as evidenced by the activation of inositol-requiring enzyme 1α, protein kinase R-like ER kinase, and activating transcription factor 6. CXL146-induced UPR activation led to a series of downstream events, including extracellular signal-regulated kinase 1/2 and c-Jun N-terminal kinase activation, which contributed to CXL146-induced apoptosis. Targeted reduction in GRP78 resulted in reduced sensitivity of HL60/MX2 toward CXL146. Long-term sublethal CXL146 exposure also led to reduction in GRP78 in HL60/MX2. These data collectively support GRP78 as the target of CXL146 in MDR treatment. Interestingly, HL60/MX2 upon long-term sublethal CXL146 exposure regained sensitivity to mitoxantrone treatment. Therefore, further exploration of CXL146 as a novel therapy in treating MDR cancer cells is warranted. SIGNIFICANCE STATEMENT: Multidrug resistance is one major challenge to cancer treatment. This study provides evidence that cancer cells overexpress 78-kDa glucose-regulated protein (GRP78) as a mechanism to acquire resistance to standard cancer therapies. A chromene-based small molecule, CXL146, selectively eliminates cancer cells with GRP78 overexpression via activating unfolded protein response-mediated apoptosis. Further characterization indicates that CXL146 and standard therapies complementarily target different populations of cancer cells, supporting the potential of CXL146 to overcome multidrug resistance in cancer treatment.

Reversal Effect of ALK Inhibitor NVP-TAE684 on ABCG2-Overexpressing Cancer Cells.

Failure of cancer chemotherapy is mostly due to multidrug resistance (MDR). Overcoming MDR mediated by overexpression of ATP binding cassette (ABC) transporters in cancer cells remains a big challenge. In this study, we explore whether NVP-TAE684, a novel ALK inhibitor which has the potential to inhibit the function of ABC transport, could reverse ABC transporter-mediated MDR. MTT assay was carried out to determine cell viability and reversal effect of NVP-TAE684 in parental and drug resistant cells. Drug accumulation and efflux assay was performed to examine the effect of NVP-TAE684 on the cellular accumulation and efflux of chemotherapeutic drugs. The ATPase activity of ABCG2 transporter in the presence or absence of NVP-TAE684 was conducted to determine the impact of NVP-TAE684 on ATP hydrolysis. Western blot analysis and immunofluorescence assay were used to investigate protein molecules related to MDR. In addition, the interaction between NVP-TAE684 and ABCG2 transporter was investigated via in silico analysis. MTT assay showed that NVP-TAE684 significantly decreased MDR caused byABCG2-, but not ABCC1-transporter. Drug accumulation and efflux tests indicated that the effect of NVP-TAE684 in decreasing MDR was due to the inhibition of efflux function of ABCG2 transporter. However, NVP-TAE684 did not alter the expression or change the subcellular localization of ABCG2 protein. Furthermore, ATPase activity analysis indicated that NVP-TAE684 could stimulate ABCG2 ATPase activity. Molecular in silico analysis showed that NVP-TAE684 interacts with the substrate binding sites of the ABCG2 transporter. Taken together, our study indicates that NVP-TAE684 could reduce the resistance of MDR cells to chemotherapeutic agents, which provides a promising strategy to overcome MDR.

Wnt3a Stimulation Promotes Primary Ciliogenesis through β-Catenin Phosphorylation-Induced Reorganization of Centriolar Satellites

Primary cilium is an antenna-like microtubule-based cellular sensing structure. Abnormal regulation of the dynamic assembly and disassembly cycle of primary cilia is closely related to ciliopathy and cancer. The Wnt signaling pathway plays a major role in embryonic development and tissue homeostasis, and defects in Wnt signaling are associated with a variety of human diseases, including cancer. In this study, we provide direct evidence of Wnt3a-induced primary ciliogenesis, which includes a continuous pathway showing that the stimulation of Wnt3a, a canonical Wnt ligand, promotes the generation of β-catenin p-S47 epitope by CK1δ, and these events lead to the reorganization of centriolar satellites resulting in primary ciliogenesis. We have also confirmed the application of our findings in MCF-7/ADR cells, a multidrug-resistant tumor cell model. Thus, our dataprovide a Wnt3a-induced primary ciliogenesis pathway and may provide a clue on how to overcome multidrug resistance in cancer treatment.

SERCA and P-glycoprotein inhibition and ATP depletion are necessary for celastrol-induced autophagic cell death and collateral sensitivity in multidrug-resistant tumor cells

Multidrug resistance (MDR) represents an obstacle in anti-cancer therapy. MDR is caused by multiple mechanisms, involving ATP-binding cassette (ABC) transporters such as P-glycoprotein (P-gp), which reduces intracellular drug levels to sub-therapeutic concentrations. Therefore, sensitizing agents retaining effectiveness against apoptosis- or drug-resistant cancers are desired for the treatment of MDR cancers. The sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA) pump is an emerging target to overcome MDR, because of its continuous expression and because the calcium transport function is crucial to the survival of tumor cells. Previous studies showed that SERCA inhibitors exhibit anti-cancer effects in Bax-Bak-deficient, apoptosis-resistant and MDR cancers, whereas specific P-gp inhibitors reverse the MDR phenotype of cancer cells by blocking efflux of chemotherapeutic agents. Here, we unraveled SERCA and P-gp as double targets of the triterpenoid, celastrol to reverse MDR. Celastrol inhibited both SERCA and P-gp to stimulate calcium-mediated autophagy and ATP depletion, thereby induced collateral sensitivity in MDR cancer cells. In vivo studies further confirmed that celastrol suppressed tumor growth and metastasis by SERCA-mediated calcium mobilization. To the best of our knowledge, our findings demonstrate collateral sensitivity in MDR cancer cells by simultaneous inhibition of SERCA and P-gp for the first time.

Models used to screen for the treatment of multidrug resistant cancer facilitated by transporter-based efflux

Efflux transporters of the adenosine triphosphate-binding cassette (ABC)-superfamily play an important role in the development of multidrug resistance (multidrug resistant; MDR) in cancer. The overexpression of these transporters can directly contribute to the failure of chemotherapeutic drugs. Several in vitro and in vivo models exist to screen for the efficacy of chemotherapeutic drugs against MDR cancer, specifically facilitated by efflux transporters. This article reviews a range of efflux transporter-based MDR models used to test the efficacy of compounds to overcome MDR in cancer. These models are classified as either in vitro or in vivo and are further categorised as the most basic, conventional models or more complex and advanced systems. Each model's origin, advantages and limitations, as well as specific efflux transporter-based MDR applications are discussed. Accordingly, future modifications to existing models or new research approaches are suggested to develop prototypes that closely resemble the true nature of multidrug resistant cancer in the human body. It is evident from this review that a combination of both in vitro and in vivo preclinical models can provide a better understanding of cancer itself, than using a single model only. However, there is still a clear lack of progression of these models from basic research to high-throughput clinical practice.

A New Strategy for Glioblastoma Treatment: In Vitro and In Vivo Preclinical Characterization of Si306, a Pyrazolo[3,4-d]Pyrimidine Dual Src/P-Glycoprotein Inhibitor.

Overexpression of P-glycoprotein (P-gp) and other ATP-binding cassette (ABC) transporters in multidrug resistant (MDR) cancer cells is responsible for the reduction of intracellular drug accumulation, thus decreasing the efficacy of chemotherapeutics. P-gp is also found at endothelial cells’ membrane of the blood-brain barrier, where it limits drug delivery to central nervous system (CNS) tumors. We have previously developed a set of pyrazolo[3,4-d]pyrimidines and their prodrugs as novel Src tyrosine kinase inhibitors (TKIs), showing a significant activity against CNS tumors in in vivo. Here we investigated the interaction of the most promising pair of drug/prodrug with P-gp at the cellular level. The tested compounds were found to increase the intracellular accumulation of Rho 123, and to enhance the efficacy of paclitaxel in P-gp overexpressing cells. Encouraging pharmacokinetics properties and tolerability in vivo were also observed. Our findings revealed a novel role of pyrazolo[3,4-d]pyrimidines which may be useful for developing a new effective therapy in MDR cancer treatment, particularly against glioblastoma.

Doxorubicin and adjudin co-loaded pH-sensitive nanoparticles for the treatment of drug-resistant cancer

Multi-drug resistance (MDR) of tumor is a major cause of chemotherapy failure. In this study, a pH-sensitive graft copolymer, poly(β-amino ester)-g-β-cyclodextrin (PBAE-g-β-CD), was synthesized via Michael addition polymerization and was employed to co-deliver doxorubicin (DOX), a chemotherapy agent, and adjudin (ADD), a mitochondrial inhibitor, in the form of dual-drug co-loaded nanoparticles (NPs). Specifically, DOX was conjugated to 1-adamantaneacetic acid (Aa) to generate a prodrug that was subsequently encapsulated in the cavity of cyclodextrin via host-guest interactions. In addition, ADD was encapsulated by poly(β-aminoester) (PBAE). The introduction of the Aa-d-α-tocopheryl polyethylene glycolsuccinate (TPGS) conjugate enhanced the biocompatibility and serum stability of the resulting NPs. The NPs can realize precise ratiometric control of drugs being loaded, increase cellular uptake of the drugs, induce mitochondrial dysfunction and augment tumor treatment efficiency by inducing apoptosis. Western blot and polymerase chain reaction analyses showed that inhibition of P-glycoprotein and X-linked inhibitor of apoptosis protein expression may underlie inhibition of tumor resistance mediated by NPs. The MCF-7/ADR xenograft tumor model also revealed that in comparison with DOX, the NPs exhibited satisfactory performance in promoting apoptosis of tumor cells and achieved high therapeutic outcomes for MDR tumors. Statement of SignificanceCombination chemotherapy is an effective way to overcome MDR of tumor. However, one of the major obstacles for successful combination chemotherapy is the co-loading, co-delivery and controlled release of two different drugs, whose chemo-physical properties may be totally different. In this study, a pH-sensitive NP system was designed to realize the co-loading and precise ratiometric control of DOX and ADD, as well as the programmed drug release. That is, ADD release was triggered by low pH in endo/lysosome after endocytosis and then DOX was hydrolyzed to achieve a sustained release in tumor cells. Therefore, the NPs exhibited an effectively growth inhibition against MDR cells both in vitro and in vivo via the synergistic effect of ADD and DOX, which provided a promising strategy for treatment of MDR cancer.

O2-evolving and ROS-activable nanoparticles for treatment of multi-drug resistant Cancer by combination of photodynamic therapy and chemotherapy

Herein, a novel nano-system IF7-ROSPCNP, which is O2-evolving and reactive oxygen species (ROS)-activable, was developed for enhancing the combination chemotherapy and photodynamic therapy (PDT). The nanoparticles composed of photosensitizers (disulfonated meso-tetraphenylporphine, TPPS2a) and catalase in the inner core, doxorubicin (DOX) in the polymeric shell and functionalized on its surface with IF7 peptide, which specially bind to annexin 1. As confirmed that the structure of IF7-ROSPCNP was able to remain intact under normal physiological conditions. After IF7-ROSPCNP was selectively entrapped by the annexin 1-positive and ROS-abundant MCF-7/ADR cells, the shell of nanoparticles was ruptured and the entrapped photosensitizers were completely released out. Under irradiation, ROS was continuously produced and the DOX, which was conjugated to the terminal of polylactic copolymer (mPEG-PLA) by a ROS-cleavable linkage, was subsequently released. With such strategy, cellular uptake of drugs was dramatically improved resulted in an enhanced cytotoxicity and anti-tumor effect on drug resistant cancer.

Current Understanding of Interactions between Nanoparticles and ABC Transporters in Cancer Cells.

ATP-binding cassette (ABC) transporters-mediated multidrug resistance (MDR) remains the major obstacle for effective cancer therapy. Nanoparticles (NPs)-based delivery systems are promising to overcome MDR, but only a few of them have been accepted for clinical treatment, which should be due to their insufficient transportation and potential toxicity. In this respect, more and more attentions are being attracted on the interactions between NPs and ABC transporters, which hold a key role in the treatment of MDR cancer and the toxicity of NPs. However, there are no systematic reviews about such interactions, especially about their corresponding mechanism. We undertook extensive search of PubMed databases for peer-reviewed literatures using focused review questions. The retrieved papers were mostly published within the 5 years (84 of 104) and all with an impact factor above 2. First, this review focused on the current knowledge of ABC transporters involved in MDR and their inhibitors. Then, we reviewed the most recent literature about the inhibitory effects of organic NPs' excipients on ABC transporters and the direct interactions of inorganic NPs with ABC transporters. The major elements of obtained papers were described and classified depending on the structure of NPs. Both organic and inorganic NPs can inhibit the function of ABC transporters, but based on different mechanisms. The effects of organic NPs are caused by several excipients like surfactants, polymers, lipids and cyclodextrin. Meanwhile, inorganic NPs usually act as the substrates of ABC transporters and competitively inhibit the efflux of drugs. These phenomena are interesting and worth investigating. The finding of this review confirmed the potential interactions between NPs and ABC transporters. These phenomena are interesting and worth investigating, and a knowledge of related mechanism would not only be important for the clinical therapies toward overcoming cancer MDR, but also help the treatment of other diseases like tuberculosis, AIDS, and central nervous system disorders, whose drugresistance was also related to ABC transporter-mediated efflux.

Transferrin-Conjugated Polymeric Nanoparticle for Receptor-Mediated Delivery of Doxorubicin in Doxorubicin-Resistant Breast Cancer Cells.

In this study, a transferrin (Tf)-conjugated polymeric nanoparticle was developed for the targeted delivery of the chemotherapeutic agent doxorubicin (Dox) in order to overcome multi-drug resistance in cancer treatment. Our objective was to improve Dox delivery for producing significant antitumor efficacy in Dox-resistant (R) breast cancer cell lines with minimum toxicity to healthy cells. The results of our experiments revealed that Dox was successfully loaded inside a transferrin (Tf)-conjugated polymeric nanoparticle composed of poloxamer 407 (F127) and 123 (P123) (Dox/F127&P123-Tf), which produced nanosized particles (~90 nm) with a low polydispersity index (~0.23). The accelerated and controlled release profiles of Dox from the nanoparticles were characterized in acidic and physiological pH and Dox/F127&P123-Tf enhanced Dox cytotoxicity in OVCAR-3, MDA-MB-231, and MDA-MB-231(R) cell lines through induction of cellular apoptosis. Moreover, Dox/F127&P123-Tf inhibited cell migration and altered the cell cycle patterns of different cancer cells. In vivo study in MDA-MB-231(R) tumor-bearing mice demonstrated enhanced delivery of nanoparticles to the tumor site when coated in a targeting moiety. Therefore, Dox/F127&P123-Tf has been tailored, using the principles of nanotherapeutics, to overcome drug-resistant chemotherapy.

Passive and active targeting in cancer therapy by liposomes and lipid nanoparticles.

Considerable development in the application of injectable drug delivery systems for cancer therapy has occurred in the last few decades. These improvements include liposomes, lipid nanoparticles (LNPs), and other nanoparticles with or without macromolecular conjugates. For example, liposomal doxorubicin modified by poly(ethylene glycol) (Doxil) was the first liposome with anti-cancer effects which was approved by the US Food and Drug Administration, whereas Abraxane (modified albumin nanoparticles loaded by paclitaxel) was recently confirmed for the treatment of breast cancer. Recently, drug delivery systems by LNPs are an emerging technology with numerous advantages over conventional liposomes and chemotherapy using free drug treatment of cancer. These properties are biocompatibility, controlled and sustained release of anti-tumor drugs, and lower toxicity. Valuable experiments on these drug delivery systems offer better treatment of multidrug-resistant cancers and lower cardiotoxicity. LNPs have been presented with high functionality in chemotherapeutic targeting of breast and prostate cancer. The basis for this targeting behavior has been shown to be both passive and active targeting. The main objective of this review was an overview of the current position of the liposome-based drug delivery systems in targeted anticancer chemotherapy.

Stimuli-responsive nanodrug self-assembled from amphiphilic drug-inhibitor conjugate for overcoming multidrug resistance in cancer treatment.

Severe multidrug resistance (MDR) often develops in the process of chemotherapy for most small molecule anticancer drugs, which results in clinical chemotherapy failures.Methods: Here, a nanodrug is constructed through the self-assembly of amphiphilic drug-inhibitor conjugates (ADIC) containing a redox-responsive linkage for reversing the multidrug resistance (MDR) in cancer treatment. Specifically, hydrophilic anticancer irinotecan (Ir) and hydrophobic P-gp protein inhibitor quinine (Qu) are linked by a redox responsive bridge for overcoming MDR of tumors.Results: Ir-ss-Qu is able to self-assemble into nanoparticles (NPs) in water and shows the longer blood retention half-life compared with that of free Ir or Qu, which facilitates drug accumulation in tumor site. After endocytosis of Ir-ss-Qu NPs by drug-resistant tumor cells, the disulfide bond in the linkage between Ir and Qu is cleaved rapidly induced by glutathione (GSH) to release anticancer drug Ir and inhibitor Qu synchronously. The released Qu can markedly reduce the expression of P-gp in drug-resistant tumor cells and inhibits P-gp to pump Ir out of the cells. The increased concentration of intracellular Ir can effectively improve the therapeutic efficacy.Conclusions: Such redox-responsive Ir-ss-Qu NPs, as a drug delivery system, exhibit very high cytotoxicity and the most effective inhibitory to the growth of drug-resistant breast cancer compared with that of free therapeutic agents in vitro and in vivo.

Drug-delivering-drug approach-based codelivery of paclitaxel and disulfiram for treating multidrug-resistant cancer

Multidrug resistance (MDR) is a common intractable barrier in success of clinical cancer chemotherapy. Codelivery of two drugs using nanocarriers is a commonly used approach to treat the MDR cancer. However, the drug payload in the conventional nanocarriers is low and thus compromises the treatment outcomes. Disulfiram (DSF) is promising to reverse MDR and increases the sensitivity of cancer cells to chemotherapy. While, paclitaxel (PTX) is one of the frequently used anticancer drug. Here, by using a drug-delivering-drug (DDD) strategy based on nanocrystals, hybrid PTX-DSF nanocrystals (PTX-DSF Ns) were developed for codelivery of PTX and DSF to reverse MDR in cancer. The 160-nm PTX-DSF Ns with rod-like morphology had drug-loading up to 43% at mass ratio of 5:1. Interestingly, the nanoparticles entered cells via caveolar endocytosis. By reducing intracellular ATP level and GST activity, PTX-DSF Ns killed the Taxol resistant A549 cells with higher efficiency than PTX alone, exhibiting as 6-fold increase of apoptosis in MDR tumor. The nanoparticles circulated in blood over time, accumulated in tumor efficiently and reduced the tumor volume by 12-fold in MDR tumor-bearing BALB/c nude mice and allowed 12-fold apoptosis in tumor. Additionally, the immunohistochemical examination demonstrated the safety of the nanoparticles. Overall, the DDD strategy-based PTX-DSF Ns have promising potential for the treatment of MDR cancer.

Taxifolin Resensitizes Multidrug Resistance Cancer Cells via Uncompetitive Inhibition of P-Glycoprotein Function.

P-glycoprotein (P-gp) effluxes lots of chemotherapeutic agents and leads to multidrug resistance (MDR) in cancer treatments. The development of P-gp inhibitors from natural products provide a potential strategy for the beneficial clinical outcomes. This study aimed to evaluate the effects of the natural flavonoid taxifolin, luteolin, (−)-gallocatechin, and (−)-catechin on human P-gp activity. The kinetic interactions and underlying mechanisms of taxifolin-mediated transporter inhibition were further investigated. The transporter inhibition ability was evaluated in human P-gp stable expression cells (ABCB1/Flp-InTM-293) by calcein-AM uptake assays. The kinetics study for P-gp inhibition was evaluated by doxorubicin and rhodamine123 efflux assays. The MDR reversal ability of taxifolin were performed by SRB assays to detect the cell viability in sensitive cancer cell line (HeLaS3), and resistant cancer cell line (KB-vin). Cell cycle analysis and ABCB1 real-time RT-PCR were used for mechanical exploration. The results demonstrated that taxifolin decreased ABCB1 expression in a concentration-dependent manner. The function of P-gp was inhibited by taxifolin through uncompetitive inhibition of rhodamine 123 and doxorubicin efflux. The combination of taxifolin significantly resensitized MDR cancer cells to chemotherapeutic agents. These results suggested that taxifolin may be considered as a potential P-gp modulator for synergistic treatment of MDR cancers.

VS-4718 Antagonizes Multidrug Resistance in ABCB1- and ABCG2-Overexpressing Cancer Cells by Inhibiting the Efflux Function of ABC Transporters.

Overexpression of ATP-binding cassette (ABC) transporters is one of the most important mechanisms responsible for multi-drug resistance (MDR). VS-4718, a tyrosine kinase inhibitor targeting focal adhesion kinase (FAK) with a potential anticancer effect, is currently evaluated in clinical trials. In this study, we investigated whether VS-4718 could reverse MDR mediated by ABC transporters, including ABCB1, ABCG2, and ABCC1. The results showed that VS-4718 significantly reversed ABCB1- and ABCG2-mediated MDR, but not MDR mediated by ABCC1. Treatment of VS-4718 did not alter the protein level and subcellular localization of ABCB1 or ABCG2. Mechanism studies indicated that the reversal effects of VS-4718 were related to attenuation of the efflux activity of ABCB1 and ABCG2 transporters. ATPase analysis indicated that VS-4718 stimulated the ATPase activity of ABCB1 and ABCG2. Docking study showed that VS-4718 interacted with the substrate-binding sites of both ABCB1 and ABCG2, suggesting that VS-4718 may affect the activity of ABCB1 and ABCG2 competitively. This study provided a novel insight for MDR cancer treatment. It indicated that combination of VS-4718 with antineoplastic drugs could attenuate MDR mediated by ABCB1 or ABCG2 in ABCB1- or ABCG2-overexpressing cancer cells.

Overcoming drug-resistant lung cancer by paclitaxel-loaded hyaluronic acid-coated liposomes targeted to mitochondria

As a major cause for the inefficiency of cancer chemotherapy, multidrug resistance (MDR) has become a major barrier to cancer treatment. Mitochondrion-orientated transportation of smart liposomes has been developed as a promising strategy to deliver anticancer drugs directly to tumor sites and actively target the mitochondria, so that drugs can interfere with mitochondrial function and facilitate cell apoptosis, overcoming MDR. Herein, we report a novel dual-functional paclitaxel (PTX) liposome system possessing both CD44-targeting and mitochondrial-targeting properties to enhance drug accumulation in mitochondria and trigger apoptosis of drug-resistant cancer cells. Mitochondria-targeting PTX-loaded liposomes were prepared by thin-film hydration and then coated with hyaluronic acid (HA) by electrostatic adsorption. We evaluated the characteristics of the PTX liposomes in vitro, and found that their particle size was about 100 nm and increased to ∼140 nm after modification by HA. The entrapment efficiency was larger than 85%, and stability data indicated that the liposomes were physically and chemically stable for at least one week at 4 °C. We further evaluated the intake, mitochondrial targeting, ATP levels, caspase-3 activity measurement, and antitumor actives of the liposomes. The results indicated that HA-coated liposomes with mitochondria targeting had significant inhibitory effects against A549 and A549/Taxol cells, showing them to be a promising means of improving therapeutic efficacy and overcoming MDR in cancer treatment.