Overcoming Multidrug Resistance by Codelivery of MDR1-Targeting siRNA and Doxorubicin Using EphA10-Mediated pH-Sensitive Lipoplexes: In Vitro and In Vivo Evaluation

mRNA-responsive two-in-one nanodrug for enhanced anti-tumor chemo-gene therapy

The combination of chemotherapy and gene therapy holds great promise for the treatment and eradication of tumors. However, due to significant differences in physicochemical properties between chemotherapeutic agents and functional nucleic acid drugs, direct integration into a single nano-agent is hindered, impeding the design and construction of an effective co-delivery nano-platform for synergistic anti-tumor treatments. In this study, we have developed an mRNA-responsive two-in-one nano-drug for effective anti-tumor therapy by the direct self-assembly of 2'-fluoro-substituted antisense DNA against P-glycoprotein (2'F-DNA) and chemo drug paclitaxel (PTX). The 2'-fluoro modification of DNA could significantly increase the interaction between the therapeutic nucleic acid and the chemotherapeutic drug, promoting the successful formation of 2'F-DNA/PTX nanospheres (2'F-DNA/PTX NSs). Due to the one-step self-assembly process without additional carrier materials, the prepared 2'F-DNA/PTX NSs exhibited considerable loading efficiency and bioavailability of PTX. In the presence of endogenous P-glycoprotein mRNA, the 2'F-DNA/PTX NSs were disassembled. The released 2'F-DNA could down-regulate the expression of P-glycoprotein, which decreased the multidrug resistance of tumor cells and enhanced the chemotherapy effect caused by PTX. In this way, the 2'F-DNA/PTX NSs could synergistically induce the apoptosis of tumor cells and realize the combined anti-tumor therapy. This strategy might provide a new tool to explore functional intracellular co-delivery nano-systems with high bioavailability and exhibit potential promising in the applications of accurate diagnosis and treatment of tumors.

Current Principles, Challenges, and New Metrics in pH-Responsive Drug Delivery Systems for Systemic Cancer Therapy

The paradigm of drug delivery via particulate formulations is one of the leading ideas that enable overcoming limitations of traditional chemotherapeutic agents. The trend toward more complex multifunctional drug carriers is well-traced in the literature. Nowadays, the prospectiveness of stimuli-responsive systems capable of controlled cargo release in the lesion nidus is widely accepted. Both endogenous and exogenous stimuli are employed for this purpose; however, endogenous pH is the most common trigger. Unfortunately, scientists encounter multiple challenges on the way to the implementation of this idea related to the vehicles' accumulation in off-target tissues, their immunogenicity, the complexity of drug delivery to intracellular targets, and finally, the difficulties in the fabrication of carriers matching all imposed requirements. Here, we discuss fundamental strategies for pH-responsive drug delivery, as well as limitations related to such carriers' application, and reveal the main problems, weaknesses, and reasons for poor clinical results. Moreover, we attempted to formulate the profiles of an "ideal" drug carrier in the frame of different strategies drawing on the example of metal-comprising materials and considered recently published studies through the lens of these profiles. We believe that this approach will facilitate the formulation of the main challenges facing researchers and the identification of the most promising trends in technology development.

Overcoming Multidrug Resistance by Base-Editing-Induced Codon Mutation

Multidrug resistance (MDR) is the main obstacle in cancer chemotherapy. ATP binding cassette (ABC) transporters on the MDR cell membrane can transport a wide range of antitumor drugs out of cells, which is one of the main causes of MDR. Therefore, disturbing ABC transporters becomes the key to reversing MDR. In this study, we implement a cytosine base editor (CBE) system to knock out the gene encoding ABC transporters by base editing. When the CBE system works in MDR cells, the MDR cells are manipulated, and the genes encoding ABC transporters can be inactivated by precisely changing single in-frame nucleotides to induce stop (iSTOP) codons. In this way, the expression of ABC efflux transporters is reduced and intracellular drug retention is significantly increased in MDR cells. Ultimately, the drug shows considerable cytotoxicity to the MDR cancer cells. Moreover, the substantial downregulation of P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) implies the successful application of the CBE system in the knockout of different ABC efflux transporters. The recovery of chemosensitivity of MDR cancer cells to the chemotherapeutic drugs revealed that the system has a satisfactory universality and applicability. We believe that the CBE system will provide valuable clues for the use of CRISPR technology to defeat the MDR of cancer cells.

Emergence of Nanoscale Drug Carriers through Supramolecular Self-Assembly of RNA with Calixarene

Supramolecular self-assembly is a powerful tool for the development of polymolecular assemblies that can form the basis of useful nanomaterials. Given the increasing popularity of RNA therapy, the extension of this concept of self-assembly to RNA is limited. Herein, a simple method for the creation of nanosized particles through the supramolecular self-assembly of RNA with a three-dimensional macrocycle from the calixarene family was reported for the first time. This self-assembly into nanoparticles was realized using cooperative supramolecular interactions under mild conditions. The obtained nanoparticles are able to bind various hydrophobic (quercetin, oleic acid) and hydrophilic (doxorubicin) drugs, as a result of which their cytotoxic properties are enhanced. This work demonstrates that intermolecular interactions between flexible RNA and rigid calixarene is a promising route to bottom-up assembly of novel supramolecular soft matter, expanding the design possibilities of nanoscale drug carriers.

Nanoparticles-Based Strategies to Improve the Delivery of Therapeutic Small Interfering RNA in Precision Oncology

Small interfering RNA (siRNA) can selectively suppress the expression of disease-causing genes, holding great promise in the treatment of human diseases, including malignant cancers. In recent years, with the development of chemical modification and delivery technology, several siRNA-based therapeutic drugs have been approved for the treatment of non-cancerous liver diseases. Nevertheless, the clinical development of siRNA-based cancer therapeutics remains a major translational challenge. The main obstacles of siRNA therapeutics in oncology include both extracellular and intracellular barriers, such as instability under physiological conditions, insufficient tumor targeting and permeability (particularly for extrahepatic tumors), off-target effects, poor cellular uptake, and inefficient endosomal escape. The development of clinically suitable and effective siRNA delivery systems is expected to overcome these challenges. Herein, we mainly discuss recent strategies to improve the delivery and efficacy of therapeutic siRNA in cancer, including the application of non-viral nanoparticle-based carriers, the selection of target genes for therapeutic silencing, and the combination with other therapeutic modalities. In addition, we also provide an outlook on the ongoing challenges and possible future developments of siRNA-based cancer therapeutics during clinical translation.

Tumor-associated macrophage membrane-camouflaged pH-responsive polymeric micelles for combined cancer chemotherapy-sensitized immunotherapy

The low immunogenicity and tumor immunosuppressive microenvironment (TIM) are two major obstacles for cancer immunotherapy. Synergistically immunogenic cell death induction and tumor-associated macrophages depletion could perfectly overcome this limitation. Herein, a tumor-associated macrophage (TAMs) membrane-camouflaged pH-responsive doxorubicin (DOX) loaded hyaluronic acid (HA)-g-poly (histidine) polymeric micelles (DHP@M2) was fabricated for the first time. DHP@M2 could effectively accumulated into tumor regions via TAMs membrane mediated immune camouflage. In acidic tumor microenvironment, particle size of DHP was enlarged due to decrease hydrophobic interaction of inner core, which caused a "membrane escape effect" to expose inner HA residue. Together high expression of α4β1 integrin, DHP@M2 could reach CD44/VCAM-1 dual-targetability to facilitate intracellular DOX accumulation for efficient ICD induction. Meanwhile, TAMs membrane could absorb colony stimulating factor 1(CSF1) through high expression of its receptor (CSF1R) on TAMs membrane to deplete TAMs in tumor tissues and relieved TIM. This strategy could efficiently induce cytotoxic T lymphocyte (CTLs) infiltration for antitumor immune response and inhibit tumor progression in 4T1 tumor bearing Balb/c mice. Therefore, DHP@M2 is suitable for cancer chemotherapy-sensitized immunotherapy.

Preparation and application of pH-responsive drug delivery systems

Microenvironment-responsive drug delivery systems (DDSs) can achieve targeted drug delivery, reduce drug side effects and improve drug efficacies. Among them, pH-responsive DDSs have gained popularity since the pH in the diseased tissues such as cancer, bacterial infection and inflammation differs from a physiological pH of 7.4 and this difference could be harnessed for DDSs to release encapsulated drugs specifically to these diseased tissues. A variety of synthetic approaches have been developed to prepare pH-sensitive DDSs, including introduction of a variety of pH-sensitive chemical bonds or protonated/deprotonated chemical groups. A myriad of nano DDSs have been explored to be pH-responsive, including liposomes, micelles, hydrogels, dendritic macromolecules and organic-inorganic hybrid nanoparticles, and micron level microspheres. The prodrugs from drug-loaded pH-sensitive nano DDSs have been applied in research on anticancer therapy and diagnosis of cancer, inflammation, antibacterial infection, and neurological diseases. We have systematically summarized synthesis strategies of pH-stimulating DDSs, illustrated commonly used and recently developed nanocarriers for these DDSs and covered their potential in different biomedical applications, which may spark new ideas for the development and application of pH-sensitive nano DDSs.

Multifunctional Lipid Bilayer Nanocarriers for Cancer Immunotherapy in Heterogeneous Tumor Microenvironments, Combining Immunogenic Cell Death Stimuli with Immune Modulatory Drugs

In addition to the contribution of cancer cells, the solid tumor microenvironment (TME) has a critical role in determining tumor expansion, antitumor immunity, and the response to immunotherapy. Understanding the details of the complex interplay between cancer cells and components of the TME provides an unprecedented opportunity to explore combination therapy for intervening in the immune landscape to improve immunotherapy outcome. One approach is the introduction of multifunctional nanocarriers, capable of delivering drug combinations that provide immunogenic stimuli for improvement of tumor antigen presentation, contemporaneous with the delivery of coformulated drug or synthetic molecules that provide immune danger signals or interfere in immune-escape, immune-suppressive, and T-cell exclusion pathways. This forward-looking review will discuss the use of lipid-bilayer-encapsulated liposomes and mesoporous silica nanoparticles for combination immunotherapy of the heterogeneous immune landscapes in pancreatic ductal adenocarcinoma and triple-negative breast cancer. We describe how the combination of remote drug loading and lipid bilayer encapsulation is used for the synthesis of synergistic drug combinations that induce immunogenic cell death, interfere in the PD-1/PD-L1 axis, inhibit the indoleamine-pyrrole 2,3-dioxygenase (IDO-1) immune metabolic pathway, restore spatial access to activated T-cells to the cancer site, or reduce the impact of immunosuppressive stromal components. We show how an integration of current knowledge and future discovery can be used for a rational approach to nanoenabled cancer immunotherapy.

The expression, function, and utilization of Protamine1: a literature review

Objective

Protamine 1 (PRM1) is specific in sperm and plays essential roles in fertilization, also a member of cancer testis antigen (CTA) family. This study aims to summarize the expression and function of PRM1 in spermatogenesis, and to broaden the current knowledge and inspire future development of PRM1-based therapeutic strategies in cancer treatment and nanomedicine.

Background

The protamine proteins, are characterized by an arginine-rich core and cysteine residues. Humans express two types of protamine: PRM1 and PRM2. The abnormal expression or proportion of PRM1 and PRM2 is known to be associated with subfertility and infertility, especially for PRM1 which is highly evolutionary conserved in mammalians and expressed in all vertebrates. Biological functions of PRM1 have been unveiled in diverse cellular processes, such as tumorigenesis, somatic cell nucleus transfer, and drug delivery systems. Moreover, PRM1 is identified as a CTA in chronic leukemia (CLL) and colorectal cancer (CRC).

Methods

Literature was obtained using PubMed and the keywords protamine 1, PRM1, or P1, from January 1, 1980, through July 20, 2021. We also collect the additional evidence through screening references of articles identified through the PubMed searches.

Conclusions

PRM1 is well-studied in male infertility, and further researches and attempts to develop PRM1 as novel tumor marker, as well as drug delivery vector, will be of important clinical significance.

Gene therapy: A promising approach for breast cancer treatment

Breast cancer (BC) is the most prevalent malignancy and the second leading cause of death among women worldwide that is caused by numerous genetic and environmental factors. Hence, effective treatment for this type of cancer requires new therapeutic approaches. The traditional methods for treating this cancer have side effects, therefore so much research have been performed in last decade to find new methods to alleviate these problems. The study of the molecular basis of breast cancer has led to the introduction of gene therapy as an effective therapeutic approach for this cancer. Gene therapy involves sending genetic material through a vector into target cells, which is followed by a correction, addition, or suppression of the gene. In this technique, it is necessary to target tumour cells without affecting normal cells. In addition, clinical trial studies have shown that this approach is less toxic than traditional therapies. This study will review various aspects of breast cancer, gene therapy strategies, limitations, challenges and recent studies in this area.

Emerging Nano-Based Strategies Against Drug Resistance in Tumor Chemotherapy

Drug resistance is the most significant causes of cancer chemotherapy failure. Various mechanisms of drug resistance include tumor heterogeneity, tumor microenvironment, changes at cellular levels, genetic factors, and other mechanisms. In recent years, more attention has been paid to tumor resistance mechanisms and countermeasures. Nanomedicine is an emerging treatment platform, focusing on alternative drug delivery and improved therapeutic effectiveness while reducing side effects on normal tissues. Here, we reviewed the principal forms of drug resistance and the new possibilities that nanomaterials offer for overcoming these therapeutic barriers. Novel nanomaterials based on tumor types are an excellent modality to equalize drug resistance that enables gain more rational and flexible drug selectivity for individual patient treatment. With the emergence of advanced designs and alternative drug delivery strategies with different nanomaterials, overcome of multidrug resistance shows promising and opens new horizons for cancer therapy. This review discussed different mechanisms of drug resistance and recent advances in nanotechnology-based therapeutic strategies to improve the sensitivity and effectiveness of chemotherapeutic drugs, aiming to show the advantages of nanomaterials in overcoming of drug resistance for tumor chemotherapy, which could accelerate the development of personalized medicine.

Delivery of small interfering RNAs by nanovesicles for cancer therapy

Small interfering ribonucleic acids (siRNAs) are originally recognized as an intermediate of the RNA interference (RNAi) pathway. They can inhibit or silence various cellular pathways by knocking down specific messenger RNA molecules. In cancer cells, siRNAs can suppress the expression of several multidrug-resistant genes, leading to the increased deposition of chemotherapeutic drugs at the tumor site. siRNA therapy can be used to selectively increase apoptosis of cancer cells or activate an immune response to the cancer. However, delivering siRNAs to the targeted location is the main limitation in achieving safe and effective delivery of siRNAs. This review highlights some representative examples of nonviral delivery systems, especially nanovesicles such as exosomes, liposomes, and niosomes. Nanovesicles can improve the delivery of siRNAs by increasing their intracellular delivery, and they have demonstrated excellent potential for cancer therapy. This review focuses on recent discoveries of siRNA targets for cancer therapy and the use of siRNAs to successfully silence these targets. In addition, this review summarizes the recent progress in designing nanovesicles (liposomes or niosomes) for siRNA delivery to cancer cells and the effects of a combination of anticancer drugs and siRNA therapy in cancer therapy.

Folate targeted hybrid lipo-polymeric nanoplexes containing docetaxel and miRNA-34a for breast cancer treatment

In spite of established evidence of the synergistic combination of hydrophobic anticancer molecule and microRNA for breast cancer treatment, their in vivo delivery has not been realized owing to their instability in the biological milieu and varied physicochemical properties. The present work reports folate targeted hybrid lipo-polymeric nanoplexes for co-delivering DTX and miR-34a. These nanoplexes exhibited a mean size of 129.3 nm with complexation efficiency at an 8:1 N/P ratio. The obtained nanoplexes demonstrated higher entrapment efficiency of DTX (94.8%) with a sustained release profile up to 85% till 48 h. Further, an improved transfection efficiency in MDA-MB-231 and 4T1 breast cancer cells was observed with uptake primarily through lipid-raft and clathrin-mediated endocytosis. Further, nanoplexes showed improved cytotoxicity (~3.5-5 folds), apoptosis (~1.6-2.0 folds), and change in expression of apoptotic genes (~4-7 folds) compared to the free treatment group in breast cancer cells. In vivo systemic administration of FA-functionalized DTX and FAM-siRNA-loaded nanoplexes showed an improved area under the curve (AUC) as well as circulation half-life compared to free DTX and naked FAM-labelled siRNA. Acute toxicity studies of the cationic polymer showed no toxicity at a dose equivalent to 10 mg/kg based on the hematological, biochemical, and histopathological examination.

T cell membrane cloaking tumor microenvironment-responsive nanoparticles with a smart "membrane escape mechanism" for enhanced immune-chemotherapy of melanoma

The application of combination immune-chemotherapy makes up for the limitation of monotherapy and achieves superior antitumor activity against cancer. However, combinational therapy is always restricted by poor tumor targeted drug delivery efficacy. Herein, novel T cell membrane cloaking tumor microenvironment-responsive nanoparticles (PBA modified T cell membrane cloaking hyaluronic acid (HA)-disulfide bond-vitamin E succinate/curcumin, shortened as RCM@T) were developed. T cell membrane cloaking not only serves as a protection shell for sufficient drug delivery but also acts as a programmed cell death-1(PD-1) "antibody" to selectively bind the PD-L1 of tumor cells. When RCM@T is intravenously administrated into the blood stream, it accumulates at tumor sites and responds to an acidic pH to achieve a "membrane escape effect" and expose the HA residues of RCM for tumor targeted drug delivery. RCM accumulates in the cytoplasm via CD44 receptor mediated endocytosis and intracellularly releases antitumor drug in the intracellular redox microenvironment for tumor chemotherapy. T cell membrane debris targets the PD-L1of tumor cells for tumor immunotherapy, which not only directly kills tumor cells, but also improves the CD8+ T cell level and facilitates effector cytokine release. Taken together, the as-constructed RCM@T creates a new way for the rational design of a drug delivery system via the combination of stimuli-responsive drug release, chemotherapeutical agent delivery and cell membrane based immune checkpoint blockade immunotherapy.

The reversal of chemotherapy-induced multidrug resistance by nanomedicine for cancer therapy

Multidrug resistance (MDR) of cancer is a persistent problem in chemotherapy. Scientists have considered the overexpressed efflux transporters responsible for MDR and chemotherapy failure. MDR extremely limits the therapeutic effect of chemotherapy in cancer treatment. Many strategies have been applied to solve this problem. Multifunctional nanoparticles may be one of the most promising approaches to reverse MDR of tumor. These nanoparticles can keep stability in the blood circulation and selectively accumulated in the tumor microenvironment (TME) either by passive or active targeting. The stimuli-sensitive or organelle-targeting nanoparticles can release the drug at the targeted-site without exposure to normal tissues. In order to better understand reversal of MDR, three main strategies are concluded in this review. First strategy is the synergistic effect of chemotherapeutic drugs and ABC transporter inhibitors. Through directly inhibiting overexpressed ABC transporters, chemotherapeutic drugs can enter into resistant cells without being efflux. Second strategy is based on nanoparticles circumventing over-expressed efflux transporters and directly targeting resistance-related organelles. Third approach is the combination of multiple therapy modes overcoming cancer resistance. At last, numerous researches demonstrated cancer stem-like cells (CSCs) had a deep relation with drug resistance. Here, we discuss two different drug delivery approaches of nanomedicine based on CSC therapy.

Nanoparticles as Drug Delivery Systems of RNAi in Cancer Therapy

RNA interference (RNAi) can mediate gene-silencing by knocking down the expression of a target gene via cellular machinery with much higher efficiency in contrast to other antisense-based approaches which represents an emerging therapeutic strategy for combating cancer. Distinct characters of nanoparticles, such as distinctive size, are fundamental for the efficient delivery of RNAi therapeutics, allowing for higher targeting and safety. In this review, we present the mechanism of RNAi and briefly describe the hurdles and concerns of RNAi as a cancer treatment approach in systemic delivery. Furthermore, the current nanovectors for effective tumor delivery of RNAi therapeutics are classified, and the characteristics of different nanocarriers are summarized.

Multifunctional nanoplatforms co-delivering combinatorial dual-drug for eliminating cancer multidrug resistance

Clinically, the primary cause of chemotherapy failure belongs to the occurrence of cancer multidrug resistance (MDR), which directly leads to the recurrence and metastasis of cancer along with high mortality. More and more attention has been paid to multifunctional nanoplatform-based dual-therapeutic combination to eliminate resistant cancers. In addition to helping both cargoes improve hydrophobicity and pharmacokinetic properties, increase bioavailability, release on demand and enhance therapeutic efficacy with low toxic effects, these smart co-delivery nanocarriers can even overcome drug resistance. Here, this review will not only present different types of co-delivery nanocarriers, but also summarize targeted and stimuli-responsive combination nanomedicines. Furthermore, we will focus on the recent progress in the co-delivery of dual-drug using such intelligent nanocarriers for surmounting cancer MDR. Whereas it remains to be seriously considered that there are some knotty issues in the fight against MDR of cancers via using co-delivery nanoplatforms, including limited intratumoral retention, the possible changes of combinatorial ratio under complex biological environments, drug release sequence from the nanocarriers, and subsequent free-drug resistance after detachment from the nanocarriers. It is hoped that, with the advantage of continuously developing nanomaterials, two personalized therapeutic agents in combination can be better exploited to achieve the goal of cooperatively combating cancer MDR, thus advancing the time to clinical transformation.

Nanomedicines for combating multidrug resistance of cancer

Chemotherapy typically involves the use of specific chemodrugs to inhibit the proliferation of cancer cells, but the frequent emergence of a variety of multidrug-resistant cancer cells poses a tremendous threat to our combat against cancer. The fundamental causes of multidrug resistance (MDR) have been studied for decades, and can be generally classified into two types: one is associated with the activation of diverse drug efflux pumps, which are responsible for translocating intracellular drug molecules out of the cells; the other is linked with some non-efflux pump-related mechanisms, such as antiapoptotic defense, enhanced DNA repair ability, and powerful antioxidant systems. To overcome MDR, intense efforts have been made to develop synergistic therapeutic strategies by introducing MDR inhibitors or combining chemotherapy with other therapeutic modalities, such as phototherapy, gene therapy, and gas therapy, in the hope that the drug-resistant cells can be sensitized toward chemotherapeutics. In particular, nanotechnology-based drug delivery platforms have shown the potential to integrate multiple therapeutic agents into one system. In this review, the focus was on the recent development of nanostrategies aiming to enhance the efficiency of chemotherapy and overcome the MDR of cancer in a synergistic manner. Different combinatorial strategies are introduced in detail and the advantages as well as underlying mechanisms of why these strategies can counteract MDR are discussed. This review is expected to shed new light on the design of advanced nanomedicines from the angle of materials and to deepen our understanding of MDR for the development of more effective anticancer strategies. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Rational Design of Hyaluronic Acid-Based Copolymer-Mixed Micelle in Combination PD-L1 Immune Checkpoint Blockade for Enhanced Chemo-Immunotherapy of Melanoma

The application of combinational therapy breaks the limitation of monotherapy and achieves better clinical benefit for tumor therapy. Herein, a hyaluronic acid/Pluronic F68-based copolymer-mixed micelle was constructed for targeted delivery of chemotherapeutical agent docetaxel (PHDM) in combination with programmed cell death ligand-1(PD-L1) antibody. When PHDM+anti-PDL1 was injected into the blood system, PHDM could accumulate into tumor sites and target tumor cells via CD44-mediated endocytosis and possess tumor chemotherapy. While anti-PDL1 could target PD-L1 protein expressed on surface of tumor cells to the immune checkpoint blockade characteristic for tumor immunotherapy. This strategy could not only directly kill tumor cells but also improve CD8+ T cell level and facilitate effector cytokines release. In conclusion, the rational-designed PHDM+anti-PDL1 therapy strategy creates a new way for tumor immune-chemotherapy.

Surmounting tumor resistance to metallodrugs by co-loading a metal complex and siRNA in nanoparticles

Copper complexes are promising anticancer agents widely studied to overcome tumor resistance to metal-based anticancer drugs. Nevertheless, copper complexes per se encounter drug resistance from time to time. Adenosine-5'-triphosphate (ATP)-responsive nanoparticles containing a copper complex CTND and B-cell lymphoma 2 (Bcl-2) small interfering RNA (siRNA) were constructed to cope with the resistance of cancer cells to the complex. CTND and siRNA can be released from the nanoparticles in cancer cells upon reacting with intracellular ATP. The resistance of B16F10 melanoma cells to CTND was terminated by silencing the cellular Bcl-2 gene via RNA interference, and the therapeutic efficacy was significantly enhanced. The nanoparticles triggered a cellular autophagy that amplified the apoptotic signals, thus revealing a novel mechanism for antagonizing the resistance of copper complexes. In view of the extensive association of Bcl-2 protein with cancer resistance to chemotherapeutics, this strategy may be universally applicable for overcoming the ubiquitous drug resistance to metallodrugs.

Progress in Natural Compounds/siRNA Co-delivery Employing Nanovehicles for Cancer Therapy

Chemotherapy using natural compounds, such as resveratrol, curcumin, paclitaxel, docetaxel, etoposide, doxorubicin, and camptothecin, is of importance in cancer therapy because of the outstanding therapeutic activity and multitargeting capability of these compounds. However, poor solubility and bioavailability of natural compounds have limited their efficacy in cancer therapy. To circumvent this hurdle, nanocarriers have been designed to improve the antitumor activity of the aforementioned compounds. Nevertheless, cancer treatment is still a challenge, demanding novel strategies. It is well-known that a combination of natural products and gene therapy is advantageous over monotherapy. Delivery of multiple therapeutic agents/small interfering RNA (siRNA) as a potent gene-editing tool in cancer therapy can maximize the synergistic effects against tumor cells. In the present review, co-delivery of natural compounds/siRNA using nanovehicles are highlighted to provide a backdrop for future research.

Engineering of a Core-Shell Nanoplatform to Overcome Multidrug Resistance via ATP Deprivation

Inhibiting the function of P-glycoprotein (P-gp) transporter, which causes drug efflux through adenosine triphosphate (ATP)-dependent manner, has become an effective strategy to conquer multidrug resistance (MDR) of cancer cells. However, there remains challenges for effective co-delivery, sequential release of P-gp modulator and chemotherapeutic agent. In this work, a novel type of core-shell nanoparticle is reported. It can independently encapsulate a high amount (about 683 µg mg^-1 ) of chemotherapeutic agent doxorubicin (DOX) in the mesoporous polydopamine (MPDA) core and glucose oxidase (GOx) in the zeolite imidazolate frameworks-8 (ZIF-8) shell, namely MPDA@ZIF-8/DOX+GOx. The fast release of GOx triggered by acid-sensitive degradation of the ZIF-8 shell consumes glucose to starve cancer cells for ATP deprivation and effective suppress ATP-dependent drug efflux in advance, and then effectively facilitates the accumulation of DOX in MCF-7/ADR cancer cells. Experiments in vitro and in vivo demonstrate that the fabricated nanosystem can dramatically improve anticancer effects for MDR through sequential release property and exhibit excellent biocompatibility. Overall, this work reveals new insights in the use of GOx for MDR treatment.

Transport Oligonucleotides-A Novel System for Intracellular Delivery of Antisense Therapeutics

Biological activity of antisense oligonucleotides (asON), especially those with a neutral backbone, is often attenuated by poor cellular accumulation. In the present proof-of-concept study, we propose a novel delivery system for asONs which implies the delivery of modified antisense oligonucleotides by so-called transport oligonucleotides (tON), which are oligodeoxyribonucleotides complementary to asON conjugated with hydrophobic dodecyl moieties. Two types of tONs, bearing at the 5′-end up to three dodecyl residues attached through non-nucleotide inserts (TD series) or anchored directly to internucleotidic phosphate (TP series), were synthesized. tONs with three dodecyl residues efficiently delivered asON to cells without any signs of cytotoxicity and provided a transfection efficacy comparable to that achieved using Lipofectamine 2000. We found that, in the case of tON with three dodecyl residues, some tON/asON duplexes were excreted from the cells within extracellular vesicles at late stages of transfection. We confirmed the high efficacy of the novel and demonstrated that MDR1 mRNA targeted asON delivered by tON with three dodecyl residues significantly reduced the level of P-glycoprotein and increased the sensitivity of KB-8-5 human carcinoma cells to vinblastine. The obtained results demonstrate the efficacy of lipophilic oligonucleotide carriers and shows they are potentially capable of intracellular delivery of any kind of antisense oligonucleotides.

Harnessing the Power of Eph/ephrin Biosemiotics for Theranostic Applications

Comprehensive basic biological knowledge of the Eph/ephrin system in the physiologic setting is needed to facilitate an understanding of its role and the effects of pathological processes on its activity, thereby paving the way for development of prospective therapeutic targets. To this end, this review briefly addresses what is currently known and being investigated in order to highlight the gaps and possible avenues for further investigation to capitalize on their diverse potential.

Application of the Tumor Site Recognizable and Dual-Responsive Nanoparticles for Combinational Treatment of the Drug-Resistant Colorectal Cancer

PURPOSE

Combination of PCI and chemotherapy represents a promising strategy for combating drug resistance of cancer. However, poor solubility of photosensitizers and unselectively released drugs at unwanted sites significantly impaired the treatment efficacy. Therefore, in the present study, we aimed to develop a nano-platform which could efficiently co-entrapping photosensitizers and chemotherapeutics for active targeting therapy of drug resistant cancers.

METHODS

Two pro-drugs were respectively developed by covalently linking the Ce6 with each other via the GSH-sensitive linkage and the PTX with mPEG-PLA-COOH through the ROS sensitive-linker. The dual-responsive nanoparticles (PNP-Ce6) was developed by emulsion/solvent evaporation method and further modified with tLyp-1 peptides. Physicochemical properties of nanoparticles were determined by the TEM and DLC. Cellular uptake assay was investigated with the Ce6 acting as the fluorescent probe and cell growth was studied by the MTT experiment. In vivo tumor targeting and anti-tumor assay was investigated on the colorectal cancer-bearing mice.

RESULTS

The developed tPNP-Ce6 were stable enough under the normal physiological conditions. However, free Ce6 and PTX were completely released when exposed the tPNP-Ce6 to the redox environment. Excellent tumor-targeting drug delivery was achieved by the tPNP-Ce6, which in turn resulted in satisfactory anit-tumor effect. Of great importance, super inhibition effect on tumor progress was achieved by the combination therapy when compared with the group only received with chemotherapy..

CONCLUSION

The results obtained in the present study indicated that the developed tPNP-Ce6 may have great potential in enhancing the therapeutic efficacy of drug-resistant colorectal cancer. Graphical Abstract Left: Targeting delivery of drug to tumor site by the tumor recognizable and dual-responsive nanoparticles and penetrating into tumor inner via the mediation of irradiation. Right: Nanoparticle distribution within tumor tissues with green represents the blood vessels stained with CD31, blue signal represents the cell nuclei stained with DAPI and red shows fluorescence of Ce6 as the indicator of the nanoparticles.

Research and development of drug delivery systems based on drug transporter and nano-formulation

In recent years, the continuous occurrence of multi-drug resistance in the clinic has made people pay more attention to the transporter. Changes in the expression and activity of transporters can cause corresponding changes in drug pharmacokinetics and pharmacodynamics. The drug-drug interactions (DDI) caused by transporters can seriously affect drug effectiveness and toxicity. In the development of pharmaceutical preparations, people have increasingly concerned about the effects and regulation of transporters in drug effects. To improve the targeting and physicochemical properties of drugs, the development of targeted agents is very rapid. Among them, novel nano-formulations are the best. With the continuous innovation and development of nano-formulation, its application has become more and more extensive. Nano-formulation has exerted certain advantages in the drug development based on transporters, and is also involved in the combination of targeted transporters. This review focuses on the application of novel nano-agents targeting transporters and the introduction of drug-transporter-based nano-formulations.

Stimuli-responsive release and efficient siRNA delivery in non-small cell lung cancer by a poly(l-histidine)-based multifunctional nanoplatform

Small interfering RNA (siRNA) has extensive potential for the treatment of non-small cell lung cancer (NSCLC). While both cationic lipids and polymers have demonstrated promise to facilitate siRNA encapsulation, they can also hamper cytosolic siRNA release and induce severe cytotoxicity. To address these issues, a unique polymer hybrid nanoparticle (NP) nanoplatform was developed for multistage siRNA delivery based on both pH-responsive and endo/lysosomal escape characteristics, which was formed via a combination of an electrostatic interactions between the copolymer methoxy poly(ethylene glycol)-poly(l-histidine)-poly(sulfadimethoxine) (mPEG-PHis-PSD, shortened to PHD), dendritic poly-l-lysine (PLL) and PLK1 siRNA (shortened to siPLK1). The biological composition of the proton sponge effect polymer of the PHis chain, which was in position to make efficient endo/lysosomal escape, and the pH-responsive polymer of the PSD fragment, which could accelerate the release of siPLK1. In the present study, the NP illustrated excellent physiochemical properties and rapid endo/lysosomal escape in vitro. Besides this, compared with the PD/PLL/siRNA formulation, the PHD/PLL/siRNA NP indicated higher cellular uptake, and higher cell cytotoxicity in vitro. The in vivo results demonstrated that the PHD/PLL/siRNA NP exhibited the strongest tumor growth inhibition rate and ideal safety compared with the control and other siPLK1-treated formulations, which can be mainly attributed to pH-induced instantaneous dissociation and efficient endo/lysosomal escape arising from the PHD copolymer. Consequently, the above evidence indicates that the PHD/PLL/siRNA NP is a favorable gene delivery system and provides a potential strategy for siRNA delivery.

The lncRNA-GAS5/miR-221-3p/DKK2 Axis Modulates ABCB1-Mediated Adriamycin Resistance of Breast Cancer via the Wnt/β-Catenin Signaling Pathway

Drug resistance, including adriamycin (ADR)-based therapeutic resistance, is a crucial cause of chemotherapy failure in breast cancer treatment. Acquired chemoresistance has been identified to be closely associated with the overexpression of P-glycoprotein (P-gp/ABCB1). Long non-coding RNA (lncRNA) growth arrest-specific 5 (GAS5) can be involved in carcinogenesis; however, its roles in ABCB1-mediated ADR resistance are poorly understood. In this study, we identified a panel of differentially expressed lncRNAs, mRNAs, and microRNAs (miRNAs) in MCF-7 and MCF-7/ADR cell lines through RNA sequencing (RNA-seq) technologies. GAS5 level was downregulated whereas ABCB1 level was upregulated in the resistant breast cancer tissues and cells. Overexpression of GAS5 significantly enhanced the ADR sensitivity and apoptosis, and it inhibited the efflux function and expression of ABCB1 in vitro, while knockdown of GAS5 had the opposite effects. Further mechanism-related investigations indicated that GAS5 acted as an endogenous “sponge” by competing for miR-221-3p binding to regulate its target dickkopf 2 (DKK2), and then it inhibited the activation of the Wnt/β-catenin pathway. Functionally, GAS5 enhanced the anti-tumor effect of ADR in vivo. Collectively, our findings reveal that GAS5 exerted regulatory function in ADR resistance possibly through the miR-221-3p/DKK2 axis, providing a novel approach to develop promising therapeutic strategy for overcoming chemoresistance in breast cancer patients.

A smart ATP-responsive chemotherapy drug-free delivery system using a DNA nanostructure for synergistic treatment of breast cancer in vitro and in vivo

This study demonstrated a chemotherapy drug-free delivery system for breast cancer treatment based on a simple DNA nanostructure composed of sequence 1 containing ATP and AS1411 aptamers and sequence 2 containing antimiR-21. The DNA nanostructure was used for co-delivery of KLA peptide and antimiR-21 as antiapoptotic agents. These therapeutic agents could not be internalised into eukaryotic cells freely which is one of the great features of this targeting platform. The presented delivery system was ATP-responsive, leading to disassembly of the DNA nanostructure in high ATP concentration of cancer cells and restoration of the function of antimiR-21 in these cells. The DNA nanostructure was associated with high cellular uptake by MCF-7 and 4T1 cells due to expression of nucleolin as target of AS1411 on their plasma membranes, while the developed targeting platform could not be internalised into CHO cells because of lack of the active targeting moiety on their surfaces. Furthermore, the results showed that co-delivery of antimiR-21 and KLA peptide using the DNA nanostructure could efficiently prohibit tumour growth in vitro and in vivo and induce a synergistic anticancer activity. Thus, this work provides a new ATP-responsive nanotargeting delivery system and synergistic chemotherapy drug-free regimen for cancer treatment.

MUC-1 recognition-based activated drug nanoplatform improves doxorubicin chemotherapy in breast cancer

Tumor-targeted drug delivery systems with stimuli-response drug release have been increasingly used to improve the therapeutic efficacy of antitumor drugs. Here, we report a specific molecular recognition activation drug nanoplatform based on specially designed DNA sensor-capped doxorubicin (DOX)-loaded mesoporous silica nanoparticles (MSNs), designated as specific molecular recognition-activated nanoparticle (SMRAN). DNA sensors on the targeted nanoparticles can trigger DOX release through a conformational switch induced by MUC-1. This causes a significant difference in cell viability between breast cancer MCF-7 and normal breast Hs578bst cells (24.8% and 86.0%). In vivo experiments showed that the tumor volume was reduced 1.5-times in the SMRAN treatment group. Compared with that in the DOX group, due to significantly improved tumor accumulation and retention of DOX. The strategy of the MUC-1 activated drug delivery system is expected to provide a new perspective for clinical application.

Enhanced anticancer effect of doxorubicin by TPGS-coated liposomes with Bcl-2 siRNA-corona for dual suppression of drug resistance

Multiple drug resistance (MDR) is a tough problem in developing hepatocellular carcinoma (HCC) therapy. Here, we developed TPGS-coated cationic liposomes with Bcl-2 siRNA corona to load doxorubicin (Dox) i.e., Bcl-2 siRNA/Dox-TPGS-LPs, to enhance anticancer effect of Dox in HCC-MDR. TPGS i.e., d-α-tocopheryl polyethylene glycol 1000 succinate, inhibited P-glycoprotein (P-gp) efflux pump and Bcl-2 siRNA suppressed anti-apoptotic Bcl-2 protein. The Bcl-2 siRNA loaded in the liposomal corona was observed under transmission electron microscopy. The stability and hemolysis evaluation demonstrated Bcl-2 siRNA/Dox-TPGS-LPs had good biocompatibility and siRNA-corona could protect the liposomal core to avoid the attachment of fetal bovine serum. In drug-resistant cells, TPGS effectively prolonged intracellular Dox retention time and siRNA-corona did improve the internalization of Dox from liposomes. In vitro and in vivo anticancer effect of this dual-functional nanostructure was examined in HCC-MDR Bel7402/5-FU tumor model. MTT assay confirmed the IC₅₀ value of Dox was 20–50 fold higher in Bel7402/5-FU MDR cells than that in sensitive Bel7402 cells. Bcl-2 siRNA corona successfully entered the cytosol of Bel7402/5-FU MDR cells to downregulate Bcl-2 protein levels in vitro and in vivo. Bcl-2 siRNA/Dox-TPGS-LPs showed superior to TPGS- (or siRNA-) linked Dox liposomes in cell apoptosis and cytotoxicity assay in Bel7402/5-FU MDR cells, and 7-fold greater effect than free Dox in tumor growth inhibition of Bel7402/5-FU xenograft nude mice. In conclusion, TPGS-coated cationic liposomes with Bcl-2 siRNA corona had the capacity to inhibit MDR dual-pathways and subsequently improved the anti-tumor activity of the chemotherapeutic agent co-delivered to a level that cannot be achieved by inhibiting a MDR single way.

Multi-Modulation of Doxorubicin Resistance in Breast Cancer Cells by Poly(l-histidine)-Based Multifunctional Micelles

Even though the reversal of multi-drug resistance (MDR) by numerous nanoparticles has been extensively studied, limited success has been achieved. To overcome this barrier, we report a rationally-designed pH-sensitive micelle, in which doxorubicin (Dox) and resveratrol (Res) were co-loaded. The micelle was based on methoxy poly (ethylene glycol)-poly(d,l-lactide)-poly(l-histidine) (mPEG-PLA-PHis), which integrated passive targeting, endo-lysosomal escape and pH-responsive payloads release. At a physiological pH of 7.4 (slightly alkali), Dox and Res were incorporated into the micelles core using the thin-film hydration method (pH-endoSM/Dox/Res). After cellular uptake, the micelles exhibited an enhanced dissociation in response to the acidic endosomes, triggering the release of Res and Dox. Furthermore, Res was observed to synergistically improve the cytotoxicity of Dox by down-regulating the P-glycoprotein (P-gp) expression, decreasing the membrane potential of the mitochondrial and ATP level, as well as inducing cell apoptosis mediated by mitochondria. The pH-endoSM/Dox/Res showed a prominent ability to decrease the IC50 of Dox by a factor of 17.38 in cell cytotoxicity against the MCF-7/ADR cell line. In vivo distribution demonstrated the excellent tumor-targeting ability of the pH-endoSM/Dox/Res. All results indicated that pH-endoSM/Dox/Res held great potential for the treatment of Dox-resistance breast cancer cells.

Carriers Break Barriers in Drug Delivery: Endocytosis and Endosomal Escape of Gene Delivery Vectors

Over the past decades, major efforts were undertaken to develop devices on a nanoscale level for the efficient and nontoxic delivery of molecules to tissues and cells, for the purpose of either diagnosis or treatment of disease. The application of such devices in drug delivery has proven to be beneficial for matters as diverse as drug solubility, drug targeting, controlled drug release, and transport of drugs across cellular barriers. Multiple nanotherapeutics have been approved for clinical treatment, and more products are being evaluated in preclinical and clinical trials. However, many biological barriers hinder the medical application of nanocarriers. There are two main classes of barriers that need to be overcome by drug nanocarriers: extracellular and intracellular barriers, both of which may capture and/or destroy therapeutics before they reach their target site. This Account discusses major biological barriers that are confronted by nanotherapeutics, following their systemic administration, focusing on cellular entry and endosomal escape of gene delivery vectors. The use of pH-responsive materials to overcome the endosomal barrier is addressed. Historically, cell biologists have studied the interaction between cells and pathogens in order to unveil the mechanisms of endocytosis and cell signaling. Meanwhile, it is becoming clear that cells may respond in similar ways to artificial drug delivery systems and, consequently, that knowledge on the cellular response against both pathogens and nanoparticulate systems will aid in the design of improved nanomedicine. A close collaboration between bioengineers and cell biologists will promote this development. At the same time, we have come to realize that tools that we use to study fundamental cellular processes, including metabolic inhibitors of endocytosis and overexpression/downregulation of proteins, may cause changes in cellular physiology. This calls for the implementation of refined methods to study nanocarrier-cell interactions, as is discussed in this Account. Finally, recent papers on the dynamics of cargo release from endosomes by means of live cell imaging have significantly advanced our understanding of the transfection process. They have initiated discussion (among others) on the limited number of endosomal escape events in transfection, and on the endosomal stage at which genetic cargo is most efficiently released. Advancements in imaging techniques, including super-resolution microscopy, in concert with techniques to label endogenous proteins and/or label proteins with synthetic fluorophores, will contribute to a more detailed understanding of nanocarrier-cell dynamics, which is imperative for the development of safe and efficient nanomedicine.

Dual-Responsive Size-Shrinking Nanocluster with Hierarchical Disassembly Capability for Improved Tumor Penetration and Therapeutic Efficacy

It is generally known that, for nanoparticles in cancer therapy, sufficient tumor penetration needs a minor particle size, while long in vivo circulation time needs a larger particle size. It is hard to balance them because they are standing on either side of a seesaw. To address these two different requirements, a dual-responsive size-shrinking nanocluster can self-adaptively respond to a complicated tumor microenvironment and transform its particulate property to overcome sequential in vivo barriers and reach a preferable antitumor activity. The nanocluster (RPSPT@SNCs) could preferentially accumulate into tumor tissue and dissociate under extracellular matrix metalloproteinase-2 (MMP-2) to release small-sized micelle formulations (RPSPTs). RPSPT possesses favorable tumor penetration and tumor targeting capability to deliver the antitumor agent paclitaxel (PTX) into deep regions of solid tumor. The intracellular redox microenvironment can also accelerate drug accumulation. The prepared RPSPT@SNCs possesses enhanced cell cytotoxicity and tumor penetration capability on MCF-7 cells and a favorable antitumor activity on the xenograft tumor mouse model.

D-α-tocopherol polyethylene glycol 1000 succinate-modified liposomes with an siRNA corona confer enhanced cellular uptake and targeted delivery of doxorubicin via tumor priming

Background

Combination therapy employing siRNAs and antitumor drugs is a promising method for the treatment of solid tumors. However, regarding combined treatments involving siRNAs and chemotherapeutic reagents, most prior research has focused on the enhanced cytotoxicity against tumor cells conferred by downregulation of the targeted protein.

Purpose

We developed D-α-tocopherol polyethylene glycol 1000 succinate (TPGS)-modified cationic liposomes (LPs) to simultaneously deliver doxorubicin (Dox) and the Bcl-2 siRNA (siBcl-2) for synergistic chemotherapy. The co-loading of siBcl-2 onto the Dox-loaded cationic LPs (siBcl-2/Dox-TPGS-LPs) could promote cellular uptake, cytotoxicity against 3D H22 tumor spheroids, circulation in the blood, drug accumulation at tumor sites, and synergistic chemotherapy in vivo.

Methods

The siBcl-2/Dox-TPGS-LPs were constructed by co-loading siBcl-2 onto the Dox-loaded TPGS-modified cationic LPs (Dox-TPGS-LPs), and Dox entrapment into the LPs was achieved using an ammonium sulfate gradient method. The antitumor effects of siBcl-2/Dox-TPGS-LPs were studied in murine hepatic carcinoma H22 cells, 3D H22 tumor spheroids, and H22 tumor-bearing mice.

Results

Dynamic light scattering technique and transmission electron microscopy images revealed that siBcl-2 loaded onto the Dox-TPGS-LPs formed a prominent corona at an nitrogen to phosphorus (N/P) ratio of 4:1, resulting in particle size increase from 155 to 210 nm and a weak positive zeta potential (+12.5 mV). The siBcl-2/Dox-TPGS-LPs enhanced the cellular uptake of Dox, promoted toxicity against 3D H22 tumor spheroids via tumor priming, prolonged Dox circulation in the blood, and increased accumulation of Dox at tumor sites, thereby enhancing the cytotoxicity of Dox in vitro and its chemotherapeutic efficacy in vivo.

Conclusion

The siBcl-2/Dox-TPGS-LPs demonstrated a strong potential for application in synergistic chemotherapy. The co-loading of siRNAs both sensitized cells toward antitumor drugs by downregulating the expression level of a specific protein and influenced the pharmacokinetic behavior of the co-delivery system in vitro and in vivo.

pH-responsive hybrid nanoparticle with enhanced dissociation characteristic for siRNA delivery

INTRODUCTION

Specific polo-like kinase (PLK1) silencing with small interface RNA (siRNA) may be an effective approach for PLK1-overexpressed lung cancer. However, low siRNA concentration into cytoplasm of tumor tissue severely limits its application.

MATERIALS AND METHODS

In this study, a novel triblock copolymer methoxy poly(ethylene glycol)-poly(histidine)-poly(sulfadimethoxine) (mPEG-PHis-PSD, shorten as PHD) was synthesized and used to construct novel nonviral gene vector with cationic liposomes.

RESULTS

The resulting hybrid nanoparticles (PHD/LR) loaded with siPLK1 possessed excellent physiochemical properties. In vitro study indicated that PHD/LR could be efficiently internalized into human lung adenocarcinoma A549 cells and downregulated PLK1 protein expression to induce cell apoptosis, which was attributed to pH-induced instantaneous dissociation, efficient endo/lysosomal escape arose from PHD copolymer. Furthermore, in vivo antitumor activity demonstrated that PHD/LR could efficiently accumulated into tumor tissue and silenced PLK1 expression to possess antitumor activity.

CONCLUSION

Taken all these together, PHD/LR was expected to be a suitable carrier for specific delivering siRNA for lung cancer therapy.

In Situ Synthesis of Ultrathin ZIF-8 Film-Coated MSNs for Codelivering Bcl 2 siRNA and Doxorubicin to Enhance Chemotherapeutic Efficacy in Drug-Resistant Cancer Cells

Multiple drug resistance is a persistent obstacle for efficient chemotherapy of cancer. Herein, we report a novel drug delivery platform. A zeolitic imidazole framework-8 (ZIF-8) film with a few nanometer thickness was in situ synthesized on the surface of carboxylated mesoporous silica (MSN-COOH) nanoparticles (NPs) for pore blocking and efficient loading of small interfering RNAs to fabricate a pH-responsive drug delivery system. The ZIF-8 film could convert the charge of MSN-COOH from negative to positive for efficient loading of siRNA via electrostatic interactions and protect siRNA from nuclease degradation. The positively charged ZIF-8 film facilitates cellular uptake and endo-lysosome escape of the NPs. In addition, the ultrathin ZIF-8 film can decompose in the acidic endo-lysosome and trigger the intracellular release of siRNAs and chemotherapeutic drugs, leading to a significantly enhanced chemotherapeutic efficacy for multidrug-resistant cancer cells including MCF-7/ADR and SKOV-3/ADR cells as demonstrated by the confocal laser scanning microscopy image, cell viability assay, Annexin V&PI staining, and flow cytometry. This approach provides a promising strategy for pH-triggered, stimuli-responsive delivery of nucleic acid drugs and chemotherapeutic agents with remarkably enhanced chemotherapeutic efficacy.

The effects of ultrasound exposure on P-glycoprotein-mediated multidrug resistance in vitro and in vivo

Background

Multidrug resistance (MDR) is often responsible for the failure of chemotherapy treatment, and current strategies for cancer MDR are not adequately satisfying as to their efficacy and safety. In this study, we sought to determine the anti-MDR effects of ultrasound (US) irradiation and its underlying mechanisms against drug-resistance.

Methods

MDR variant MCF-7/ADR cell lines and endothelial cell lines were used to determine the appropriate ultrasound intensity for in vitro experiments. MCF-7/ADR cell and HEPG2/ADM cells were used to assess the anti-MDR effect of US irradiation. Intracellular adriamycin (ADM) accumulation, Cell viability, cell proliferation and cell apoptosis were evaluated after ADM + US treatment or ADM treatment alone. MCF-7/ADR xenograft mice were used to investigate the appropriate ultrasound intensity for in vivo experiments and its effect on the long-term prognosis. Underlining mechanisms by which ultrasound exposure reversing MDR phenotype were investigated both in vitro and in vivo.

Results

Combination of ADM and 0.74 W/cm² US irradiation enhanced ADM intracellular concentration and nuclear accumulation in MCF-7/ADR and HEPG2/ADM cells, compared to those treated with ADM alone. Enhanced cellular ADM uptake and nuclei localization was associated with increased cytotoxicity of ADM to ADM-resistant cells, lower ADM-resistant cell viability and proliferative cell ratio, and higher apoptotic cell ratio. More importantly, US exposure increased the effectiveness of ADM to inhibit tumor growth in MCF-7/ADR xenograft mice. Mechanistically, US exposure promoted ADM accumulation in MDR cells mainly through down-regulation of P-glycoprotein (P-gp), which is dependent on US-induced intracellular reactive oxygen species (ROS) production. US-induced oxidative stress promoted miR-200c-3p and miR-34a-3p expression by forming miR-200c/34a/ZEB1 double-negative feedback loop. Finally, US-induced miR-200c/34a overexpression decreased P-gp expression and reversed MDR phenotype.

Conclusion

US irradiation could reverse MDR phenotype by activating ROS-ZEB1-miR200c/34a-P-gp signal pathway. Our findings offer a new and promising strategy for sensitizing cells to combat MDR and to improve the therapeutic index of chemotherapy.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0900-6) contains supplementary material, which is available to authorized users.