Benzoyl indoles with metabolic stability as reversal agents for ABCG2-mediated multidrug resistance

Epertinib counteracts multidrug resistance in cancer cells by antagonizing the drug efflux function of ABCB1 and ABCG2

A significant hurdle in cancer treatment arises from multidrug resistance (MDR), often due to overexpression of ATP-binding cassette (ABC) transporters like ABCB1 and/or ABCG2 in cancer cells. These transporters actively diminish the efficacy of cytotoxic drugs by facilitating ATP hydrolysis-dependent drug efflux and reducing intracellular drug accumulation in cancer cells. Addressing multidrug-resistant cancers poses a significant challenge due to the lack of approved treatments, prompting the exploration of alternative avenues like drug repurposing (also referred to as drug repositioning) of molecularly targeted agents to reverse MDR-mediated by ABCB1 and/or ABCG2 in multidrug-resistant cancer cells. Epertinib, a potent inhibitor of EGFR and HER2 currently in clinical trials for solid tumors, was investigated for its potential to resensitize ABCB1- and ABCG2-overexpressing multidrug-resistant cancer cells to chemotherapeutic agents. Our findings reveal that at sub-toxic, submicromolar concentrations, epertinib restores the sensitivity of multidrug-resistant cancer cells to cytotoxic drugs in a concentration-dependent manner. The results demonstrate that epertinib enhances drug-induced apoptosis in these cancer cells by impeding the drug-efflux function of ABCB1 and ABCG2 without altering their expression. ATPase activity and molecular docking were employed to reveal potential interaction sites between epertinib and the drug-binding pockets of ABCB1 and ABCG2. In summary, our study demonstrates an additional pharmacological capability of epertinib against the activity of ABCB1 and ABCG2. These findings suggest that incorporating epertinib into combination therapy could be advantageous for a specific patient subset with tumors exhibiting high levels of ABCB1 or ABCG2, warranting further exploration.

MS-BACL: enhancing metabolic stability prediction through bond graph augmentation and contrastive learning

MOTIVATION

Accurately predicting molecular metabolic stability is of great significance to drug research and development, ensuring drug safety and effectiveness. Existing deep learning methods, especially graph neural networks, can reveal the molecular structure of drugs and thus efficiently predict the metabolic stability of molecules. However, most of these methods focus on the message passing between adjacent atoms in the molecular graph, ignoring the relationship between bonds. This makes it difficult for these methods to estimate accurate molecular representations, thereby being limited in molecular metabolic stability prediction tasks.

RESULTS

We propose the MS-BACL model based on bond graph augmentation technology and contrastive learning strategy, which can efficiently and reliably predict the metabolic stability of molecules. To our knowledge, this is the first time that bond-to-bond relationships in molecular graph structures have been considered in the task of metabolic stability prediction. We build a bond graph based on 'atom-bond-atom', and the model can simultaneously capture the information of atoms and bonds during the message propagation process. This enhances the model's ability to reveal the internal structure of the molecule, thereby improving the structural representation of the molecule. Furthermore, we perform contrastive learning training based on the molecular graph and its bond graph to learn the final molecular representation. Multiple sets of experimental results on public datasets show that the proposed MS-BACL model outperforms the state-of-the-art model.

AVAILABILITY AND IMPLEMENTATION

The code and data are publicly available at https://github.com/taowang11/MS.

Epidermal Growth Factor Receptor Inhibitor Mobocertinib Resensitizes Multidrug-Resistant Cancer Cells by Attenuating the Human ATP-Binding Cassette Subfamily B Member 1 and Subfamily G Member 2

ATP-binding cassette (ABC) transporters, notably ABCB1 (P-glycoprotein) and ABCG2, play a crucial role in the development of multidrug resistance (MDR) during the administration of chemotherapy for cancer patients. With a lack of approved treatments for addressing multidrug-resistant cancers, MDR remains a substantial challenge to the effective management of cancer. Rather than focusing on developing novel synthetic inhibitors, a promising approach to combat MDR involves repurposing approved therapeutic agents to enhance the sensitivity to cytotoxic antiproliferative drugs of multidrug-resistant cancer cells with high expression of ABCB1 or ABCG2. In this investigation, we observed a substantial reversal of MDR conferred by ABCB1 and ABCG2 in multidrug-resistant cancer cells through the use of mobocertinib, an approved third-generation inhibitor of the epidermal growth factor receptor (EGFR) tyrosine kinase. Mobocertinib demonstrated the ability to hinder drug transport function without causing changes in protein expression. The interactions between mobocertinib and ABCB1, as well as ABCG2, were validated through ATPase assays. Furthermore, in silico docking simulations were utilized to substantiate the binding of mobocertinib within the drug-binding pockets of both ABCB1 and ABCG2. We conclude that further testing of mobocertinib in combination therapy is warranted for patients with tumors expressing elevated levels of the ABC drug transporters ABCB1 and ABCG2.

Metabolism-guided development of Ko143 analogs as ABCG2 inhibitors

ATP-binding cassette subfamily G member 2 (ABCG2), an efflux transporter, is involved in multiple pathological processes. Ko143 is a potent ABCG2 inhibitor; however, it is quickly metabolized through carboxylesterase 1-mediated hydrolysis of its t-butyl ester moiety. The current work aimed to develop more metabolically stable ABCG2 inhibitors. Novel Ko143 analogs were designed and synthesized by replacing the unstable t-butyl ester moiety in Ko143 with an amide group. The synthesized Ko143 analogs were evaluated for their ABCG2 inhibitory activity, binding mode with ABCG2, cytotoxicity, and metabolic stability. We found that the amide modification of Ko143 led to metabolically stable ABCG2 inhibitors. Among these Ko143 analogs, K2 and K34 are promising candidates with favorable oral pharmacokinetic profiles in mice. In summary, we synthesized novel Ko143 analogs with improved metabolic stability, which can potentially be used as lead compounds for the future development of ABCG2 inhibitors.

Furmonertinib, a Third-Generation EGFR Tyrosine Kinase Inhibitor, Overcomes Multidrug Resistance through Inhibiting ABCB1 and ABCG2 in Cancer Cells

ATP-binding cassette transporters, including ABCB1 (P-glycoprotein) and ABCG2 (BCRP/MXR/ABCP), are pivotal in multidrug resistance (MDR) development in cancer patients undergoing conventional chemotherapy. The absence of approved therapeutic agents for multidrug-resistant cancers presents a significant challenge in effectively treating cancer. Researchers propose repurposing existing drugs to sensitize multidrug-resistant cancer cells, which overexpress ABCB1 or ABCG2, to conventional anticancer drugs. The goal of this study is to assess whether furmonertinib, a third-generation epidermal growth factor receptor tyrosine kinase inhibitor overcomes drug resistance mediated by ABCB1 and ABCG2 transporters. Furmonertinib stands out due to its ability to inhibit drug transport without affecting protein expression. The discovery of this characteristic was validated through ATPase assays, which revealed interactions between furmonertinib and ABCB1/ABCG2. Additionally, in silico docking of furmonertinib offered insights into potential interaction sites within the drug-binding pockets of ABCB1 and ABCG2, providing a better understanding of the underlying mechanisms responsible for the reversal of MDR by this repurposed drug. Given the encouraging results, we propose that furmonertinib should be explored as a potential candidate for combination therapy in patients with tumors that have high levels of ABCB1 and/or ABCG2. This combination therapy holds the potential to enhance the effectiveness of conventional anticancer drugs and presents a promising strategy for overcoming MDR in cancer treatment.

Design, synthesis, and biological evaluation of phenylurea indole derivatives as ABCG2 inhibitors

Three series of phenylurea indole derivatives were synthesized with potent inhibitory activities on ABCG2 with simple and efficient synthetic routes. Among these compounds, four phenylurea indole derivatives 3c-3f with extended π system were discovered as the most potent ABCG2 inhibitors, while these compounds showed no inhibition on ABCB1. Compounds 3c and 3f were selected for further investigation to explore the mechanisms of action on reversing ABCG2-mediated multidrug resistance (MDR). The results revealed that compounds 3c and 3f increased the accumulation of mitoxantrone (MX) in ABCG2-overexpressing cells, but they did not alter the expression level or localization of ABCG2 in cells. In addition, both 3c and 3f significantly stimulated the ATP hydrolysis of ABCG2 transporter indicating that they can be competitive substrates of ABCG2 transporter, and thereby increase the accumulation of mitoxantrone in ABCG2-overexpressing H460/MX20 cells. Both 3c and 3f was docked into the drug-binding site of the human ABCG2 transporter protein (PDB 6FFC) with high affinities. This study showed that extending the π system of phenylurea indole derivatives enhanced their inhibitory activities on ABCG2, which may provide a clue for the further research to discover more potent ABCG2 inhibitors.

Design, Synthesis and Biological Evaluation of Quinazolinamine Derivatives as Breast Cancer Resistance Protein and P-Glycoprotein Inhibitors with Improved Metabolic Stability

A series of twenty-two quinazolinamine derivatives showing potent inhibitory activities on breast cancer resistance protein (BCRP) and p-glycoprotein (P-gp) were synthesized. A cyclopropyl-containing quinazolinamine 22 was identified as a dual BCRP and P-gp inhibitor, while azide-containing quinazolinamine 33 showed BCRP inhibitory activity. These lead compounds were further investigated in a battery of mechanistic experiments. Compound 22 changed the localization of BCRP and P-gp in cells, thus inhibiting the efflux of anticancer drugs by the two ATP-binding cassette (ABC) transporters. In addition, both 22 and 33 significantly stimulated the ATP hydrolysis of the BCRP transporter, indicating that they can be competitive substrates of the BCRP transporter, and thereby increase the accumulation of mitoxantrone in BCRP-overexpressing H460/MX20 cells. Azide derivative 33, exhibited a greater inhibitory effect on BCRP after UV activation and can serve as a valuable probe for investigating the interactions of quinazolinamine derivatives with BCRP. Notably, the dual BCRP and P-gp inhibitors 4-5, 22-24, 27, and BCRP inhibitor 33 showed improved metabolic stability compared to Ko143.

Small-Molecule Gankyrin Inhibition as a Therapeutic Strategy for Breast and Lung Cancer

Gankyrin is an oncoprotein responsible for the development of numerous cancer types. It regulates the expression levels of multiple tumor suppressor proteins (TSPs) in liver cancer; however, gankyrin's regulation of these TSPs in breast and lung cancers has not been thoroughly investigated. Additionally, no small-molecule gankyrin inhibitor has been developed which demonstrates potent anti-proliferative activity against gankyrin overexpressing breast and lung cancers. Herein, we are reporting the structure-based design of gankyrin-binding small molecules which potently inhibited the proliferation of gankyrin overexpressing A549 and MDA-MB-231 cancer cells, reduced colony formation, and inhibited the growth of 3D spheroids in an in vitro tumor simulation model. Investigations demonstrated that gankyrin inhibition occurs through either stabilization or destabilization of its 3D structure. These studies shed light on the mechanism of small-molecule inhibition of gankyrin and demonstrate that gankyrin is a viable therapeutic target for the treatment of breast and lung cancer.

Molecular Modeling Strategies of Cancer Multidrug Resistance

Cancer remains a leading cause of morbidity and mortality worldwide. Hence, the increase in cancer cases observed in the elderly population, as well as in children and adolescents, makes human malignancies a prime target for anticancer drug development. Although highly effective chemotherapeutic agents are continuously developed and approved for clinical treatment, the major impediment towards curative cancer therapy remains multidrug resistance (MDR). In recent years, intensive studies have been carried out on the identification of new therapeutic molecules to reverse MDR efflux transporters of the ATP-binding cassette (ABC) superfamily. Although a great deal of progress has been made in the development of specific inhibitors for certain MDR efflux pumps in experimental studies, advanced computational studies can accelerate this drug development process. In the literature, there are many experimental studies on the impact of natural products and synthetic small molecules on the reversal of cancer MDR. Molecular modeling methods provide an opportunity to explain the activity of these molecules on the ABC-transporter family with non-covalent interactions as well as it is possible to carry out studies for the discovery of new anticancer drugs specific to MDR with these methods. The coordinate file of the 3-dimensional (3D) structure of the target protein is indispensable for molecular modeling studies. In some cases where a 3D structure cannot be obtained by experimental methods, the homology modeling method can be applied to obtain the file containing the target protein's information including atomic coordinates, secondary structure assignments, and atomic connectivity. Homology modeling studies are of great importance for efflux transporter proteins that still lack 3D structures due to crystallization problems with multiple hydrophobic transmembrane domains. Quantum mechanics, molecular docking and molecular dynamics simulation applications are the most frequently used molecular modeling methods in the literature to investigate non-covalent interactions between the drug-ABC transporter superfamily. The quantitative structure-activity relationship (QSAR) model provides a relationship between the chemical properties of a compound and its biological activity. Determining the pharmacophore region for a new drug molecule by superpositioning a series of molecules according to their physicochemical properties using QSAR models is another method in which molecular modeling is used in computational drug development studies with ABC transporter proteins. There are also in silico absorption, distribution, metabolism, excretion, and toxicity (ADME/Tox) studies conducted to make a prediction about the pharmacokinetic properties, and drug-likeness of new molecules. Drug repurposing studies, which have become a trending topic in recent years, involve identifying possible new targets for an already approved drug molecule. There are few studies in the literature in which drug repurposing performed by molecular modelling methods has been applied on ABC transporter proteins. The aim of the current paper is to create a complete review of drug development studies including aforementioned molecular modeling methods carried out between the years 2019-2021. Furthermore, an intensive investigation is also conducted on licensed applications and free web servers used in in silico studies. The current review is an up-to-date guide for researchers who plan to conduct computational studies with MDR transporter proteins.

Insights on the structure-function relationship of human multidrug resistance protein 7 (MRP7/ABCC10) from molecular dynamics simulations and docking studies

ATP-binding cassette (ABC) transporters superfamily mediates multidrug resistance in cancer by extruding structurally distinct chemotherapeutic agents, causing failure in chemotherapy. Among the 49 ABC transporters, multidrug resistance protein 7 (MRP7 or ABCC10) is relatively new and has been identified as the efflux pump of multiple anticancer agents including Vinca alkaloids and taxanes. Herein, we construct and validate a homology model for human MRP7 based on the cryo-EM structures of MRP1. Structure-function relationship of MRP7 was obtained from molecular dynamics simulations and docking studies and was in accordance with previous studies of ABC transporters. The motion patterns correlated with efflux mechanism were discussed. Additionally, predicted substrate- and modulator-binding sites of MRP7 were described for the first time, which provided rational insights in understanding the drug binding and functional regulation in MRP7. Our findings will benefit the high-throughput virtual screening and development of MRP7 modulators in the future.

Establishment and Characterization of a Novel Multidrug Resistant Human Ovarian Cancer Cell Line With Heterogenous MRP7 Overexpression

Ovarian cancer is one of the leading female malignancies which accounts for the highest mortality rate among gynecologic cancers. Surgical cytoreduction followed by chemotherapy is the mainstay of treatment. However, patients with recurrent ovarian cancer are likely to exhibit resistance to chemotherapy due to reduced sensitivity to chemotherapeutic drugs. Adenosine triphosphate (ATP)-binding cassette (ABC) transporters have been extensively studied as multidrug resistance (MDR) mediators since they are responsible for the efflux of various anticancer drugs. Multidrug resistance protein 7 (MRP7, or ABCC10) was discovered in 2001 and revealed to transport chemotherapeutic drugs. Till now, only limited knowledge was obtained regarding its roles in ovarian cancer. In this study, we established an MRP7-overexpressing ovarian cancer cell line SKOV3/MRP7 via transfecting recombinant MRP7 plasmids. The SKOV3/MRP7 cell line was resistant to multiple anticancer drugs including paclitaxel, docetaxel, vincristine and vinorelbine with a maximum of 8-fold resistance. Biological function of MRP7 protein was further determined by efflux-accumulation assays. Additionally, MTT results showed that the drug resistance of the SKOV3/MRP7 cells was reversed by cepharanthine, a known inhibitor of MRP7. Moreover, we also found that the overexpression of MRP7 enhanced the migration and epithelial-mesenchymal transition (EMT) induction. In conclusion, we established an in vitro model of MDR in ovarian cancer and suggested MRP7 overexpression as the leading mechanism of chemoresistance in this cell line. Our results demonstrated the potential relationship between MRP7 and ovarian cancer MDR.

VKNG-1 Antagonizes ABCG2-Mediated Multidrug Resistance via p-AKT and Bcl-2 Pathway in Colon Cancer: In Vitro and In Vivo Study

The emergence of multidrug resistance (MDR) to chemotherapeutic drugs is a major problem in the therapy of cancer. Knowledge of the mechanisms of drug resistance in cancer is necessary for developing efficacious therapies. ATP-binding cassette (ABC) transporters are transmembrane proteins that efflux chemotherapeutic drugs from cancer cells, thereby producing MDR. Our research efforts have led to the discovery of VKNG-1, a compound that selectively inhibits the ABCG2 transporter and reverses resistanctabe to standard anticancer drugs both in vitro and in vivo. VKNG-1, at 6 µM, selectively inhibited ABCG2 transporter and sensitized ABCG2-overexpressing drug-resistant cancer cells to the ABCG2 substrate anticancer drugs mitoxantrone, SN-38, and doxorubicin in ABCG2-overexpressing colon cancers. VKNG- 1 reverses ABCG2-mediated MDR by blocking ABCG2 efflux activity and downregulating ABCG2 expression at the mRNA and protein levels. Moreover, VKNG-1 inhibits the level of phosphorylated protein kinase B (PKB/p-AKT), and B-cell lymphoma-2 (Bcl-2) protein which may overcome resistance to anticancer drugs. However, the in vitro translocation of ABCG2 protein did not occur in the presence of 6 µM of VKNG-1. In addition, VKNG-1 enhanced the anticancer efficacy of irinotecan in ABCG2- overexpressing mouse tumor xenografts. Overall, our results suggest that VKNG-1 may, in combination with certain anticancer drugs, represent a treatment to overcome ABCG2-mediated MDR colon cancers.

CMP25, a synthetic new agent, targets multidrug resistance-associated protein 7 (MRP7/ABCC10)

Multidrug resistance-associated protein 7 (MRP7) is an important member of ABC transporter superfamily and has been revealed to mediate the cross-membrane translocation of a wide range of chemotherapeutic agents including taxanes, epothilones, Vinca alkaloids, Anthracyclines and Epipodophyllotoxins.In our previous study, a 1,2,3-triazole-pyrimidine hybridCMP25was synthesized and found able to efficiently reverse multidrug resistance (MDR) mediated by P-glycoprotein. In this study, we evaluated the efficacy of compound CMP25in reversing MDR mediated by MRP7in vitro. The results showed that CMP25significantly sensitized MRP7-overexpressing cells to anticancer drugs that are MRP7 substrates. Mechanistic study showed that CMP25reversed MRP7-mediated MDR by increasing the intracellular accumulation of anticancer drugs and decreasing drug efflux, without altering protein expression level or subcellular localization. Currently, very few studies on synthetic MRP7 modulators have been published. Our findings provide a valuable prototype for designing drugs to combine with conventional anticancer drugs to overcome MDR-mediated by MRP7.

The Novel Benzamide Derivative, VKNG-2, Restores the Efficacy of Chemotherapeutic Drugs in Colon Cancer Cell Lines by Inhibiting the ABCG2 Transporter

The overexpression of ATP-binding cassette transporter, ABCG2, plays an important role in mediating multidrug resistance (MDR) in certain types of cancer cells. ABCG2-mediated MDR can significantly attenuate or abrogate the efficacy of anticancer drugs by increasing their efflux from cancer cells. In this study, we determined the efficacy of the novel benzamide derivative, VKNG-2, to overcome MDR due to the overexpression of the ABCG2 transporter in the colon cancer cell line, S1-M1-80. In vitro, 5 μM of VKNG-2 reversed the resistance of S1-M1-80 cell line to mitoxantrone (70-fold increase in efficacy) or SN-38 (112-fold increase in efficacy). In contrast, in vitro, 5 μM of VKNG-2 did not significantly alter either the expression of ABCG2, AKT, and PI3K p110β protein or the subcellular localization of the ABCG2 protein compared to colon cancer cells incubated with the vehicle. Molecular docking data indicated that VKNG-2 had a high docking score (-10.2 kcal/mol) for the ABCG2 transporter substrate-drug binding site whereas it had a low affinity on ABCB1 and ABCC1 transporters. Finally, VKNG-2 produced a significant concentration-dependent increase in ATPase activity (EC50 = 2.3 µM). In conclusion, our study suggests that in vitro, VKNG-2 reverses the resistance of S1-M1-80, a cancer cell line resistant to mitoxantrone and SN-38, by inhibiting the efflux function of the ABCG2 transporter.

Multidrug resistance proteins (MRPs): Structure, function and the overcoming of cancer multidrug resistance

ATP-binding cassette (ABC) transporters mediate the ATP-driven translocation of structurally and mechanistically distinct substrates against steep concentration gradients. Among the seven human ABC subfamilies namely ABCA-ABCG, ABCC is the largest subfamily with 13 members. In this respect, 9 of the ABCC members are termed "multidrug resistance proteins" (MRPs1-9) due to their ability to mediate cancer multidrug resistance (MDR) by extruding various chemotherapeutic agents or their metabolites from tumor cells. Furthermore, MRPs are also responsible for the ATP-driven efflux of physiologically important organic anions such as leukotriene C₄, folic acid, bile acids and cAMP. Thus, MRPs are involved in important regulatory pathways. Blocking the anticancer drug efflux function of MRPs has shown promising results in overcoming cancer MDR. As a result, many novel MRP modulators have been developed in the past decade. In the current review, we summarize the structure, tissue distribution, biological and pharmacological functions as well as clinical insights of MRPs. Furthermore, recent updates in MRP modulators and their therapeutic applications in clinical trials are also discussed.

In vitro and ex vivo anti‑tumor effect and mechanism of Tucatinib in leukemia stem cells and ABCG2‑overexpressing leukemia cells

Leukemia stem cells (LSCs), which evade standard chemotherapy, may lead to chemoresistance and disease relapse. The overexpression of ATP-binding cassette subfamily G member 2 (ABCG2) is an important determinant of drug resistance in LSCs and it can serve as a marker for LSCs. Targeting ABCG2 is a potential strategy to selectively treat and eradicate LSCs, and, hence, improve leukemia therapy. Tucatinib (Irbinitinib) is a novel tyrosine kinase inhibitor, targeting ErbB family member HER2, and was approved by the Food and Drug Administration in April 2020, and in Switzerland in May 2020 for the treatment of HER2-positive breast cancer. In the present study, the results demonstrated that tucatinib significantly improved the efficacy of conventional chemotherapeutic agents in ABCG2-overexpressing leukemia cells and primary leukemia blast cells, derived from patients with leukemia. In addition, tucatinib markedly decreased the proportion of leukemia stem cell-like side population (SP) cells. In SP cells, isolated from leukemia cells, the intracellular accumulation of Hoechst 33342, which is an ABCG2 substrate, was significantly elevated by tucatinib. Furthermore, tucatinib notably inhibited the efflux of [³H]-mitoxantrone and, hence, there was a higher level of [³H]-mitoxantrone in the HL60/ABCG2 cell line. The result from the ATPase assay revealed that tucatinib may interact with the drug substrate-binding site and stimulated ATPase activity of ABCG2. However, the protein expression level and cellular location of ABCG2 were not affected by tucatinib treatment. Taken together, these data suggested that tucatinib could sensitize conventional chemotherapeutic agents, in ABCG2-overexpressing leukemia cells and LSCs, by blocking the pump function of the ABCG2 protein. The present study revealed that combined treatment with tucatinib and conventional cytotoxic agents could be a potential therapeutic strategy in ABCG2-positive leukemia.

Reversal of Cancer Multidrug Resistance (MDR) Mediated by ATP-Binding Cassette Transporter G2 (ABCG2) by AZ-628, a RAF Kinase Inhibitor

Overexpression of ABCG2 remains a major impediment to successful cancer treatment, because ABCG2 functions as an efflux pump of chemotherapeutic agents and causes clinical multidrug resistance (MDR). Therefore, it is important to uncover effective modulators to circumvent ABCG2-mediated MDR in cancers. In this study, we reported that AZ-628, a RAF kinase inhibitor, effectively antagonizes ABCG2-mediated MDR in vitro. Our results showed that AZ-628 completely reversed ABCG2-mediated MDR at a non-toxic concentration (3 μM) without affecting ABCB1-, ABCC1-, or ABCC10 mediated MDR. Further studies revealed that the reversal mechanism was by attenuating ABCG2-mediated efflux and increasing intracellular accumulation of ABCG2 substrate drugs. Moreover, AZ-628 stimulated ABCG2-associated ATPase activity in a concentration-dependent manner. Docking and molecular dynamics simulation analysis showed that AZ-628 binds to the same site as ABCG2 substrate drugs with higher score. Taken together, our studies indicate that AZ-628 could be used in combination chemotherapy against ABCG2-mediated MDR in cancers.

Uncompetitive nanomolar dimeric indenoindole inhibitors of the human breast cancer resistance pump ABCG2

Multidrug resistance membrane pumps reduce the efficacy of chemotherapies by exporting a wide panel of structurally-divergent drugs. Here, to take advantage of the polyspecificity of the human Breast Cancer Resistance Protein (BCRP/ABCG2) and the dimeric nature of this pump, new dimeric indenoindole-based inhibitors from the monomeric α,β-unsaturated ketone 4b and phenolic derivative 5a were designed. A library of 18 homo/hetero-dimers was synthesised. Homo-dimerization shifted the inhibition efficacy from sub-micromolar to nanomolar range, correlated with the presence of 5a, linked by a 2-6 methylene-long linker. Non-toxic, the best dimers displayed a therapeutic ratio as high as 70,000. It has been found that the high potency of the best compound 7b that displays a K_I of 17 nM is due to an uncompetitive behavior toward mitoxantrone efflux and specific for that drug, compared to Hoechst 33342 efflux. Such property may be useful to target such anticancer drug efflux mediated by ABCG2. Finally, at a molecular level, an uncompetitive mechanism by which substrate promotes inhibitor binding implies that at least 2 ligands should bind simultaneously to the drug-binding pocket of ABCG2.

Understanding performance of 3D-printed sorbent in study of metabolic stability

Metabolic stability tests are one of the fundamental steps at the preclinical stages of new drug development. Microsomes, used as a typical enzymatic model of liver biotransformation, can be a challenging matrix for analytical scientists due to a high concentration of cellular proteins and membrane lipids. In the work, we propose a new procedure integrating biotransformation reaction with SPME-like protocol for sample clean-up. It is beneficial to increase the overall quality of results in contrary to the typical protein precipitation approach. A set of ten arylpiperazine analogs, six of which are considered promising drug candidates (and four are accepted drugs) were used as a probe to assess the goodness of the newly proposed approach. In order to promote an efficient extraction protocol, a new, miniaturized shape of a sorbent, suitable to perform the extraction in 100 µL of the sample has been designed. Termination of the biotransformation process by protein denaturation with hot water was additionally evaluated. A quantitative structure-property relationship (QSPR) study using Orthogonal Partial Least Squares (OPLS) technique to reveal insights to the sorption mechanism was also performed. The obtained results showed the new 3D-printed sorbent can be an attractive basis for the new sample preparation approach for metabolic stability studies and an alternative for commercially available protocols based on solid-phase microextraction (SPME) or solid-phase extraction (SPE) principles.

Modulating the function of ABCB1: in vitro and in vivo characterization of sitravatinib, a tyrosine kinase inhibitor

BACKGROUND

Overexpression of ATP-binding cassette (ABC) transporter is a major contributor to multidrug resistance (MDR), in which cancer cells acquire resistance to a wide spectrum of chemotherapeutic drugs. In this work, we evaluated the sensitizing effect of sitravatinib, a broad-spectrum tyrosine kinase inhibitor (TKI), on ATP-binding cassette subfamily B member 1 (ABCB1)- and ATP-binding cassette subfamily C member 10 (ABCC10)-mediated MDR.

METHODS

MTT assay was conducted to examine cytotoxicity and evaluate the sensitizing effect of sitravatinib at non-toxic concentrations. Tritium-labeled paclitaxel transportation, Western blotting, immunofluorescence analysis, and ATPase assay were carried out to elucidate the mechanism of sitravatinib-induced chemosensitization. The in vitro findings were translated into preclinical evaluation with the establishment of xenograft models.

RESULTS

Sitravatinib considerably reversed MDR mediated by ABCB1 and partially antagonized ABCC10-mediated MDR. Our in silico docking simulation analysis indicated that sitravatinib strongly and stably bound to the transmembrane domain of ABCB1 human-mouse chimeric model. Furthermore, sitravatinib inhibited hydrolysis of ATP and synchronously decreased the efflux function of ABCB1. Thus, sitravatinib could considerably enhance the intracellular concentration of anticancer drugs. Interestingly, no significant alterations of both expression level and localization of ABCB1 were observed. More importantly, sitravatinib could remarkably restore the antitumor activity of vincristine in ABCB1-mediated xenograft model without observable toxic effect.

CONCLUSIONS

The findings in this study suggest that the combination of sitrvatinib and substrate antineoplastic drugs of ABCB1 could attenuate the MDR mediated by the overexpression of ABCB1.

Dual TTK/CLK2 inhibitor, CC-671, selectively antagonizes ABCG2-mediated multidrug resistance in lung cancer cells

One pivotal factor that leads to multidrug resistance (MDR) is the overexpression of ABCG2. Therefore, tremendous effort has been devoted to the search of effective reversal agents to overcome ABCG2‐mediated MDR. CC‐671 is a potent and selective inhibitor of both TTK (human protein kinase monopolar spindle 1 [hMps1]) and CDC like kinase 2 (CLK2). It represents a new class of cancer therapeutic drugs. In this study, we show that CC‐671 is an effective ABCG2 reversal agent that enhances the efficacy of chemotherapeutic drugs in ABCG2‐overexpressing lung cancer cells. Mechanistic studies show that the reversal effect of CC‐671 is primarily attributed to the inhibition of the drug efflux activity of ABCG2, which leads to an increased intracellular level of chemotherapeutic drugs. In addition, CC‐671 does not alter the protein expression or subcellular localization of ABCG2. The computational molecule docking analysis suggests CC‐671 has high binding affinity to the drug‐binding site of ABCG2. In conclusion, we reveal the interaction between CC‐671 and ABCG2, providing a rationale for the potential combined use of CC‐671 with ABCG2 substrate to overcome MDR.

Erdafitinib Resensitizes ABCB1-Overexpressing Multidrug-Resistant Cancer Cells to Cytotoxic Anticancer Drugs

The development of multidrug resistance (MDR) in cancer patients, which is often associated with the overexpression of ABCB1 (MDR1, P-glycoprotein) in cancer cells, remains a significant problem in cancer chemotherapy. ABCB1 is one of the major adenosine triphosphate (ATP)-binding cassette (ABC) transporters that can actively efflux a range of anticancer drugs out of cancer cells, causing MDR. Given the lack of Food and Drug Administration (FDA)-approved treatment for multidrug-resistant cancers, we explored the prospect of repurposing erdafitinib, the first fibroblast growth factor receptor (FGFR) kinase inhibitor approved by the FDA, to reverse MDR mediated by ABCB1. We discovered that by reducing the function of ABCB1, erdafitinib significantly resensitized ABCB1-overexpressing multidrug-resistant cancer cells to therapeutic drugs at sub-toxic concentrations. Results of erdafitinib-stimulated ABCB1 ATPase activity and in silico docking analysis of erdafitinib binding to the substrate-binding pocket of ABCB1 further support the interaction between erdafitinib and ABCB1. Moreover, our data suggest that ABCB1 is not a major mechanism of resistance to erdafitinib in cancer cells. In conclusion, we revealed an additional action of erdafitinib as a potential treatment option for multidrug-resistant cancers, which should be evaluated in future drug combination trials.

Advanced oxidation protein products upregulate efflux transporter expression and activity through activation of the Nrf-2-mediated signaling pathway in vitro and in vivo

Clinical and benchtop studies suggest that chronic kidney disease (CKD) alters both renal and nonrenal clearance of drugs. Although studies have documented that the accumulating uremic toxins in the body under CKD conditions are humoral factors that alter the expression and/or activity of drug transporters, the specific process is poorly understood. In this study, we found that advanced oxidation protein products (AOPPs), which are a modified protein uremic toxin, could upregulate efflux transporters, including P-glycoprotein (ABCB1), multi-drug resistance-associated protein 2 (ABCC2) and breast cancer resistance protein (ABCG2) expression in CKD rat models and in HepG2 cells. Our research shows that renal function decline was associated with the accumulation of AOPPs in serum and the upregulation of efflux transporters in the liver in two rat models of CKD. In HepG2 cells, AOPPs significantly increased the expression of efflux transporters in a dose- and time-dependent manner and upregulated the mRNA expression, protein expression and activity of efflux transporters, but bovine serum albumin (BSA), a synthetic precursor of AOPPs, had no effect. This effect correlated with AOPPs activation of the nuclear factor E2-related factor 2 (Nrf-2)-mediated signaling pathway. Further investigation of the regulation of Nrf-2 by AOPPs revealed that ML385 and siNrf-2 abolished the upregulatory effects of AOPPs. These findings suggest that AOPPs upregulate ABCB1, ABCG2 and ABCC2 through Nrf-2 signaling pathways. Protein uremic toxins, such as AOPPs, may modify the nonrenal clearance of drugs in patients with CKD through effects on drug transporters.

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.

Venetoclax, a BCL-2 Inhibitor, Enhances the Efficacy of Chemotherapeutic Agents in Wild-Type ABCG2-Overexpression-Mediated MDR Cancer Cells

Previous studies have shown that small-molecule BCL-2 inhibitors can have a synergistic interaction with ABCG2 substrates in chemotherapy. Venetoclax is a potent and selective BCL-2 inhibitor, approved by the FDA in 2016 for the treatment of patients with chronic lymphocytic leukemia (CLL). This study showed that, at a non-toxic concentration, venetoclax at 10 µM significantly reversed multidrug resistance (MDR) mediated by wild-type ABCG2, without significantly affecting MDR mediated by mutated ABCG2 (R482G and R482T) and ABCB1, while moderate or no reversal effects were observed at lower concentrations (0.5 to 1 µM). The results showed that venetoclax increased the intracellular accumulation of chemotherapeutic agents, which was the result of directly blocking the wild-type ABCG2 efflux function and inhibiting the ATPase activity of ABCG2. Our study demonstrated that venetoclax potentiates the efficacy of wild-type ABCG2 substrate drugs. These findings may provide useful guidance in combination therapy against wild-type ABCG2-mediated MDR cancer in clinical practice.

Biological evaluation of non-basic chalcone CYB-2 as a dual ABCG2/ABCB1 inhibitor

The enhancement of drug efflux caused by ATP-binding cassette (ABC) transporters (including ABCG2 and ABCB1) overexpression is an important factor for multidrug resistance (MDR) in cancers. After testing the reversal activities of 19 chalcone and bis-chalcone derivatives on MDR cancer cell lines, we found that non-basic chalcone CYB-2 exhibited the most potent reversal activities against both ABCG2- and ABCB1-mediated MDR. The mechanistic studies show that this compound can increase the accumulation of anticancer drugs in both ABCG2- and ABCB1-overexpressing cancer cell lines, resulting from the blocked efflux function of the MDR cancer cell lines. This inhibition is due to the barred ABCG2 and ABCB1 ATPase activities rather than altering the expression or localization of ABCG2 or ABCB1 transporters. The previous studies showed that non-basic chalcones were ABCG2-specific inhibitors; however, we found that non-basic chalcone CYB-2 can be developed as an ABCG2/ABCB1 dual inhibitor to overcome MDR in cancers that co-express both ABCG2 and ABCB1. Moreover, non-basic chalcone CYB-2 has synthetic tractability compared to other chalcone-based derivatives.

Sitravatinib Sensitizes ABCB1- and ABCG2-Overexpressing Multidrug-Resistant Cancer Cells to Chemotherapeutic Drugs

The development of multidrug resistance (MDR) in cancer patients driven by the overexpression of ATP-binding cassette (ABC) transporter ABCB1 or ABCG2 in cancer cells presents one of the most daunting therapeutic complications for clinical scientists to resolve. Despite many novel therapeutic strategies that have been tested over the years, there is still no approved treatment for multidrug-resistant cancers to date. We have recently adopted a drug repurposing approach to identify therapeutic agents that are clinically active and at the same time, capable of reversing multidrug resistance mediated by ABCB1 and ABCG2. In the present study, we investigated the effect of sitravatinib, a novel multitargeted receptor tyrosine kinase inhibitor, on human ABCB1 and ABCG2 in multidrug-resistant cancer cell lines. We discovered that at submicromolar concentrations, sitravatinib re-sensitizes ABCB1- and ABCG2-overexpressing multidrug-resistant cancer cells to chemotherapeutic drugs. We found that sitravatinib blocks the drug efflux function of ABCB1 and ABCG2 in a concentration-dependent manner but does not significantly alter the protein expression of ABCB1 or ABCG2 in multidrug-resistant cancer cells. In conclusion, we reveal a potential drug repositioning treatment option for multidrug-resistant cancers by targeting ABCB1 and ABCG2 with sitravatinib and should be further investigated in future clinical trials.