The FLT3 and PDGFR inhibitor crenolanib is a substrate of the multidrug resistance protein ABCB1 but does not inhibit transport function at pharmacologically relevant concentrations

Overexpression of ABCB1 confers resistance to FLT3 inhibitor FN-1501 in cancer cells: in vitro and in vivo characterization

FN-1501 is a potent FLT3 inhibitor with antitumor activity. A phase 1 trial of FN-1501 monotherapy in patients with advanced solid tumors and R/R AML is in progress. Since one of the primary causes of multidrug resistance (MDR) is the overexpression of ATP-binding cassette superfamily B member 1 (ABCB1), the objective of this study was to investigate the potential relationship between FN-1501 and the ABCB1 transporter. We found ABCB1 overexpressing-cancer cells conferred FN-1501 resistance, which could be reversed by an ABCB1 inhibitor. Molecular docking study revealed that FN-1501 docked the ligand binding site with an affinity score of -9.77 kcal/mol, denoting a strong interaction between FN-1501 and ABCB1. Additionally, the ABCB1 ATPase assay indicated that FN-1501 could significantly stimulate ABCB1 ATPase activity. Furthermore, we observed a similar trend of ABCB1-facilated FN-1501 resistance in tumor-bearing mice model. In sum, we demonstrate that FN-1501 is a substrate of ABCB1 transporter from both in vivo and in vitro studies. Therefore, our findings provide new insight on the mechanism of chemoresistance due to ABCB1 overexpression.

Comprehensive Analysis of Universal Stress Protein Family Genes and Their Expression in Fusarium oxysporum Response of Populus davidiana × P. alba var. pyramidalis Louche Based on the Transcriptome

Universal stress proteins (USPs) are typical stress-inducible proteins that function directly in a variety of biotic or abiotic stresses and effectively protect plants from complex, adverse environments. However, the expression patterns of USP genes under pathogen stress and their molecular mechanisms in stress resistance have not been reported in detail. In this study, 46 USP genes were identified from Populus trichocarpa (PtrUSPs), and their biological characteristics were comprehensively analyzed based on phylogeny, physicochemical properties of proteins, and gene structures. The promoter regions of PtrUSPs contain a variety of cis-acting elements related to hormone and stress response. The results of a collinearity analysis showed that PtsrUSPs were highly conserved with homologous genes from four other representative species (Arabidopsis thaliana, Eucalyptus grandis, Glycine max, and Solanum lycopersicum). Furthermore, RNA-Seq analysis showed that the expression of 46 USPs from P. davidiana × P. alba var. pyramidalis Louche (PdpapUSPs) was significantly induced by Fusarium oxysporum. The co-expression network and gene ontology analysis of PtrUSPs showed that they participated in the response to stress and response to stimulus through precise coordination. The results of this paper systematically revealed the biological characteristics of PtrUSPs and the characteristics of their response to F. oxysporum stress, which will lay a theoretical foundation for improving genetic traits and the breeding of poplar disease-resistant varieties in subsequent studies.

Drug-drug interactions associated with FLT3 inhibitors for acute myeloblastic leukemia: current landscape

INTRODUCTION

FLT3 inhibitors (FLT3i) are drugs in which there is limited experience and not yet enough information on the mechanisms of absorption, transport, and elimination; but especially on the potential drug-drug interactions (DDIs). There are therefore risks in the management of FLT3i DDIs (i.e. sorafenib, ponatinib, crenolanib, midostaurin, quizartinib, and gilteritinib) and ignoring them can compromise therapeutic success in acute myeloid leukemia (AML) treatment, in complex patients and secondary pathologies.

AREAS COVERED

This review summarizes the DDIs of FLT3i with P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), organic anion transporting (OAT), organic cationic transporting (OCT), cytochrome P450 (CYP) subunits, and other minor metabolic/transport pathways. EMBASE, PubMed, the Cochrane Central Register and the Web of Science were searched. The last literature search was performed on the 14 February 2022.

EXPERT OPINION

FLT3i will be combined with other therapeutic agents (supportive care, doublet, or triplet therapy) and in different clinical settings, which means a greater chance of controlling and even eradicating the disease effectively, but also an increased risk to patients due to potential DDIs. Healthcare professionals should be aware of the potential interactions that may occur and be vigilant in monitoring those patients who are receiving any potentially interacting drug.

A curated binary pattern multitarget dataset of focused ATP-binding cassette transporter inhibitors

Multitarget datasets that correlate bioactivity landscapes of small-molecules toward different related or unrelated pharmacological targets are crucial for novel drug design and discovery. ATP-binding cassette (ABC) transporters are critical membrane-bound transport proteins that impact drug and metabolite distribution in human disease as well as disease diagnosis and therapy. Molecular-structural patterns are of the highest importance for the drug discovery process as demonstrated by the novel drug discovery tool ‘computer-aided pattern analysis’ (‘C@PA’). Here, we report a multitarget dataset of 1,167 ABC transporter inhibitors analyzed for 604 molecular substructures in a statistical binary pattern distribution scheme. This binary pattern multitarget dataset (ABC_BPMDS) can be utilized for various areas. These areas include the intended design of (i) polypharmacological agents, (ii) highly potent and selective ABC transporter-targeting agents, but also (iii) agents that avoid clearance by the focused ABC transporters [e.g., at the blood-brain barrier (BBB)]. The information provided will not only facilitate novel drug prediction and discovery of ABC transporter-targeting agents, but also drug design in general in terms of pharmacokinetics and pharmacodynamics.

Measurement(s)	Influx • Efflux • Tracer • Transport velocity
Technology Type(s)	Fluorometry • Radioactivity • Plate reader • Flow cytometer • Tracer distribution
Factor Type(s)	half-maximal inhibition concentration
Sample Characteristic - Organism	Homo sapiens
Sample Characteristic - Environment	cell culture
Sample Characteristic - Location	Kingdom of Norway • Germany • Australia • Latvia

Genome-Wide Analysis of Major Facilitator Superfamily and Its Expression in Response of Poplar to Fusarium oxysporum

The major facilitator superfamily (MFS) is one of the largest known membrane transporter families. MFSs are involved in many essential functions, but studies on the MFS family in poplar have not yet been reported. Here, we identified 41 MFS genes from Populus trichocarpa (PtrMFSs). We built a phylogenetic tree, which clearly divided members of PtrMFS into six groups with specific gene structures and protein motifs/domains. The promoter regions contain various cis-acting elements involved in stress and hormone responsiveness. Genes derived from segmental duplication events are unevenly distributed in 17 poplar chromosomes. Collinearity analysis showed that PtrMFS genes are conserved and homologous to corresponding genes from four other species. Transcriptome data indicated that 40 poplar MFS genes were differentially expressed when treated with Fusarium oxysporum. Co-expression networks and gene function annotations of MFS genes showed that MFS genes tightly co-regulated and closely related in function of transmembrane transport. Taken together, we systematically analyzed structure and function of genes and proteins in the PtrMFS family. Evidence indicated that poplar MFS genes play key roles in plant development and response to a biological stressor.

Scaffold fragmentation and substructure hopping reveal potential, robustness, and limits of computer-aided pattern analysis (C@PA)

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Exploratory changes in substructure patterns are well tolerated by C@PA.

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Extended positive substructures support prediction capability.

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Increased biological hit rate of 40% for multitarget pan-ABC transporter inhibition.

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Contribution to major understanding of pattern analysis and multitarget activity.

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Pan-ABC transporter inhibitors as tool for elucidation of multitarget binding site.

Computer-aided pattern analysis (C@PA) was recently presented as a powerful tool to predict multitarget ABC transporter inhibitors. The backbone of this computational methodology was the statistical analysis of frequently occurring molecular features amongst a fixed set of reported small-molecules that had been evaluated toward ABCB1, ABCC1, and ABCG2. As a result, negative and positive patterns were elucidated, and secondary positive substructures could be suggested that complemented the multitarget fingerprints. Elevating C@PA to a non-statistical and exploratory level, the concluded secondary positive patterns were extended with potential positive substructures to improve C@PA’s prediction capabilities and to explore its robustness. A small-set compound library of known ABCC1 inhibitors with a known hit rate for triple ABCB1, ABCC1, and ABCG2 inhibition was taken to virtually screen for the extended positive patterns. In total, 846 potential broad-spectrum ABCB1, ABCC1, and ABCG2 inhibitors resulted, from which 10 have been purchased and biologically evaluated. Our approach revealed 4 novel multitarget ABCB1, ABCC1, and ABCG2 inhibitors with a biological hit rate of 40%, but with a slightly lower inhibitory power than derived from the original C@PA. This is the very first report about discovering novel broad-spectrum inhibitors against the most prominent ABC transporters by improving C@PA.

C@PA: Computer-Aided Pattern Analysis to Predict Multitarget ABC Transporter Inhibitors

Based on literature reports of the last two decades, a computer-aided pattern analysis (C@PA) was implemented for the discovery of novel multitarget ABCB1 (P-gp), ABCC1 (MRP1), and ABCG2 (BCRP) inhibitors. C@PA included basic scaffold identification, substructure search and statistical distribution, as well as novel scaffold extraction to screen a large virtual compound library. Over 45,000 putative and novel broad-spectrum ABC transporter inhibitors were identified, from which 23 were purchased for biological evaluation. Our investigations revealed five novel lead molecules as triple ABCB1, ABCC1, and ABCG2 inhibitors. C@PA is the very first successful computational approach for the discovery of promiscuous ABC transporter inhibitors.

Rational drug design of 6-substituted 4-anilino-2-phenylpyrimidines for exploration of novel ABCG2 binding site

In the search for novel, highly potent, and nontoxic adjuvant chemotherapeutics to resolve the major issue of ABC transporter-mediated multidrug resistance (MDR), pyrimidines were discovered as a promising compound class of modern ABCG2 inhibitors. As ABCG2-mediated MDR is a major obstacle in leukemia, pancreatic carcinoma, and breast cancer chemotherapy, adjuvant chemotherapeutics are highly desired for future clinical oncology. Very recently, docking studies of one of the most potent reversers of ABCG2-mediated MDR were reported and revealed a putative second binding pocket of ABCG2. Based on this (sub)pocket, a series of 16 differently 6-substituted 4-anilino-2-phenylpyrimidines was designed and synthesized to explore the potential increase in inhibitory activity of these ABCG2 inhibitors. The compounds were assessed for their influence on the ABCG2-mediated pheophorbide A transport, as well as the ABCB1- and ABCC1-mediated transport of calcein AM. They were additionally evaluated in MDR reversal assays to determine their half-maximal reversal concentration (EC₅₀). The 6-substitution did not only show increased toxicity against ABCG2-overexpressing cells in combination with SN-38 but also a negative influence on cell viability in general. Nevertheless, several candidates had EC₅₀ values in the low double-digit nanomolar concentration range, qualifying them as some of the most potent reversers of ABCG2-mediated MDR. In addition, five novel multitarget ABCB1, ABCC1, and ABCG2 inhibitors were discovered, four of them exerting their inhibitory power against the three stated transporters at least in the single-digit micromolar concentration range.

Superior Pyrimidine Derivatives as Selective ABCG2 Inhibitors and Broad-Spectrum ABCB1, ABCC1, and ABCG2 Antagonists

In the search for highly effective modulators addressing ABCG2-mediated MDR, 23 pyrimidines were synthesized and biologically assessed. Seven derivatives with (a) nitrogen- and/or halogen-containing residue(s) had extraordinary potencies against ABCG2 (IC₅₀ < 150 nM). The compounds competitively inhibited ABCG2-mediated Hoechst 33342 transport but were not substrates of ABCG2. The most potent MDR reverser, compound 19, concentration-dependently increased SN-38-mediated cancer cell death at 11 nM (EC₅₀), time-dependently doubled SN-38 toxicity in a period of 7 days at 10 nM, and half-maximally accelerated cell death combined with SN-38 at 17 nM. No induction of ABCG2 was observed. Furthermore, 11 pyrimidines were revealed as triple ABCB1/ABCC1/ABCG2 inhibitors. Five possessed IC₅₀ values below 10 μM against each transporter, classifying them as some of the 50 most potent multitarget ABC transporter inhibitors. The most promising representative, compound 37, reversed ABCB1-, ABCC1-, and ABCG2-mediated MDR, making it one of the three most potent ABC transporter inhibitors and reversers of ABC transporters-mediated MDR.

The potent roles of salt-inducible kinases (SIKs) in metabolic homeostasis and tumorigenesis

Salt-inducible kinases (SIKs) belong to AMP-activated protein kinase (AMPK) family, and functions mainly involve in regulating energy response-related physiological processes, such as gluconeogenesis and lipid metabolism. However, compared with another well-established energy-response kinase AMPK, SIK roles in human diseases, especially in diabetes and tumorigenesis, are rarely investigated. Recently, the pilot roles of SIKs in tumorigenesis have begun to attract more attention due to the finding that the tumor suppressor role of LKB1 in non-small-cell lung cancers (NSCLCs) is unexpectedly mediated by the SIK but not AMPK kinases. Thus, here we tend to comprehensively summarize the emerging upstream regulators, downstream substrates, mouse models, clinical relevance, and candidate inhibitors for SIKs, and shed light on SIKs as the potential therapeutic targets for cancer therapies.

Novel Quinoline Compound Derivatives of NSC23925 as Potent Reversal Agents Against P-Glycoprotein-Mediated Multidrug Resistance

Multidrug resistance is a serious problem and a common cause of cancer treatment failure, leading to patient death. Although numerous reversal resistance inhibitors have been evaluated in preclinical or clinical trials, efficient and low-toxicity reversal agents have not been identified. In this study, a series of novel quinoline compound derivatives from NSC23925 were designed to inhibit P-glycoprotein (P-gp). Among them, YS-7a showed a stronger inhibitory effect against P-gp than verapamil, as a positive control, when co-incubated with chemotherapy drugs at minimally cytotoxic concentrations. YS-7a suppressed the P-gp transport function without affecting the expression of P-gp but stimulated the ATPase activity of P-gp in a dose-dependent manner. Next, molecular docking was used to predict the six most probable binding sites, namely, SER270, VAL273, VAL274, ILE354, VAL357, and PHE390. Moreover, YS-7a had no effect on cytochrome P450 3A4 activity and showed little toxicity to normal cells. In addition, combined treatment of YS-7a with vincristine showed a better inhibitory effect than the positive control verapamil in vivo without a negative effect on mouse weight. Overall, our results showed that YS-7a could reverse cancer multidrug resistance through the inhibition of P-gp transport function in vitro and in vivo, suggesting that YS-7a may be a novel therapeutic agent.

The FLT3 inhibitor midostaurin selectively resensitizes ABCB1-overexpressing multidrug-resistant cancer cells to conventional chemotherapeutic agents

The occurrence of multidrug resistance (MDR) associated with the overexpression of the ATP-binding cassette (ABC) protein ABCB1 in cancer cells remains a significant obstacle to successful cancer chemotherapy. Therefore, discovering modulators that are capable of inhibiting the drug efflux function or expression of ABCB1 and re-sensitizing multidrug-resistant cancer cells to anticancer agents is of great clinical importance. Regrettably, due to potential adverse events associated with drug-drug interactions and toxicity in patients, researchers have struggled to develop a synthetic inhibitor of ABCB1 that is clinically applicable to improve the effectiveness of chemotherapy. Alternatively, through drug repositioning of approved drugs, we discovered that the FMS-like tyrosine kinase-3 (FLT3) inhibitor midostaurin blocks the drug transport function of ABCB1 and re-sensitizes ABCB1-overexpressing multidrug-resistant cancer cells to conventional chemotherapeutic drugs. Our findings were further supported by results demonstrating that midostaurin potentiates drug-induced apoptosis in ABCB1-overexpressing cancer cells and inhibits the ATPase activity of ABCB1. Considering that midostaurin is a clinically approved anticancer agent, our findings revealed an additional action of midostaurin and that patients with multidrug-resistant tumors may benefit from a combination therapy of midostaurin with standard chemotherapy, which should be further investigated.

Revisiting the role of ABC transporters in multidrug-resistant cancer

Most patients who die of cancer have disseminated disease that has become resistant to multiple therapeutic modalities. Ample evidence suggests that the expression of ATP-binding cassette (ABC) transporters, especially the multidrug resistance protein 1 (MDR1, also known as P-glycoprotein or P-gp), which is encoded by ABC subfamily B member 1 (ABCB1), can confer resistance to cytotoxic and targeted chemotherapy. However, the development of MDR1 as a therapeutic target has been unsuccessful. At the time of its discovery, appropriate tools for the characterization and clinical development of MDR1 as a therapeutic target were lacking. Thirty years after the initial cloning and characterization of MDR1 and the implication of two additional ABC transporters, the multidrug resistance-associated protein 1 (MRP1; encoded by ABCC1)), and ABCG2, in multidrug resistance, interest in investigating these transporters as therapeutic targets has waned. However, with the emergence of new data and advanced techniques, we propose to re-evaluate whether these transporters play a clinical role in multidrug resistance. With this Opinion article, we present recent evidence indicating that it is time to revisit the investigation into the role of ABC transporters in efficient drug delivery in various cancer types and at the blood-brain barrier.