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The breast cancer resistance protein (BCRP/ABCG2) transporter mediates the efflux of numerous antineoplastic drugs, playing a central role in multidrug resistance related to cancer. The absence of successful clinical trials using specific ABCG2 inhibitors reveals the urge to identify new compounds to attend this critical demand. In this work, a series of 13 magnolol derivatives was tested as ABCG2 inhibitors. Only two compounds, derivatives 10 and 11, showed partial and complete ABCG2 inhibitory effect, respectively. This inhibition was selective toward ABCG2, since none of the 13 compounds inhibited neither P-glycoprotein nor MRP1. Both inhibitors (10 and 11) were not transported by ABCG2 and demonstrated a low cytotoxic profile even at high concentrations (up to 100 µM). 11 emerged as the most promising compound of the series, considering the ratio between cytotoxicity (IG 50 ) and ABCG2 inhibition potency (IC 50 ), showing a therapeutic ratio (TR) higher than observed for 10 (10.5 versus 1.6, respectively). This derivative showed a substrate-independent and a mixed type of inhibition. The effect of compound 11 on the ABCG2 ATPase activity and thermostability revealed allosteric protein changes. This compound did not affect the expression levels of ABCG2 and increased the binding of the conformational-sensitive antibody 5D3. A docking study showed that 11 did not share the same binding site with ABCG2 substrate mitoxantrone. Finally, 11 could revert the chemoresistance to SN-38 mediated by ABCG2., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

This paper describes a novel, simple, and low-cost device to perform in vitro photodynamic therapy (PDT) assays, named the PhotoACT. The device was built using a set of conventional programmable light-emitting diodes (LEDs), a liquid crystal display (LCD) module, and a light sensor connected to a commercial microcontroller board. The box-based structure of the prototype was made with medium-density fiberboards (MDFs). The internal compartment can simultaneously allocate four cell culture multiwell microplates. As a proof of concept, we studied the cytotoxic effect of the photosensitizer (PS) verteporfin against the HeLa cell line in two-dimensional (2D) culture. HeLa cells were treated with increasing concentrations of verteporfin for 24 h. The drug-containing supernatant medium was discarded, the adherent cells were washed with phosphate-buffered saline (PBS), and drug-free medium was added. In this study, the effect of verteporfin on cells was examined either without light exposure or after exposure for 1 h to light using red-green-blue (RGB) values of 255, 255, and 255 (average fluence of 49.1 ± 0.6 J/cm 2 ). After 24 h, the cell viability was assessed by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide (MTT) assay. Experimental results showed that exposure of cells treated with verteporfin to the light from the device enhances the drug's cytotoxic effect via a mechanism mediated by reactive oxygen species (ROS). In addition, the use of the prototype described in this work was validated by comparing the results with a commercial PDT device. Thus, this LED-based photodynamic therapy prototype represents a good alternative for in vitro studies of PDT.

The primary source of failure of cancer therapies is multidrug resistance (MDR), which can be caused by different mechanisms, including the overexpression of ABC transporters in cancer cells. Among the 48 human ABC proteins, the breast cancer resistance protein (BCRP/ABCG2) has been described as a pivotal player in cancer resistance. The use of functional inhibitors and expression modulators is a promising strategy to overcome the MDR caused by ABCG2. Despite the lack of clinical trials using ABCG2 inhibitors, many compounds have already been discovered. This review presents an overview about various ABCG2 inhibitors that have been identified, discussing some chemical aspects and the main experimental methods used to identify and characterize the mechanisms of new inhibitors. In addition, some biological requirements to pursue preclinical tests are described. Finally, we discuss the potential use of ABCG2 inhibitors in cancer stem cells (CSC) for improving the objective response rate and the mechanism of ABCG2 modulators at transcriptional and protein expression levels., (Copyright © 2022 Elsevier Masson SAS. All rights reserved.)

Multidrug resistance (MDR) is one of the major factors in the failure of many chemotherapy approaches. In cancer cells, MDR is mainly associated with the expression of ABC transporters such as P-glycoprotein, MRP1 and ABCG2. Despite major efforts to develop new selective and potent inhibitors of ABC drug transporters, no ABCG2-specific inhibitors for clinical use are yet available. Here, we report the evaluation of sixteen tetrahydroquinoline/4,5-dihydroisoxazole derivatives as a new class of ABCG2 inhibitors. The affinity of the five best inhibitors was further investigated by the vanadate-sensitive ATPase assay. Molecular modelling data, proposing a potential binding mode, suggest that they can inhibit the ABCG2 activity by binding on site S1, previously reported as inhibitors binding region, as well targeting site S2, a selective region for substrates, and by specifically interacting with residues Asn436, Gln398, and Leu555. Altogether, this study provided new insights into THQ/4,5-dihydroisoxazole molecular hybrids, generating great potential for the development of novel most potent ABCG2 inhibitors., (© 2021 The Authors. ChemMedChem published by Wiley-VCH GmbH.)

Perillyl alcohol is a natural compound that has attracted a significant interest due to its potent antitumor activity. However, clinical trials have exhibited poor tolerance by oral administration, mainly due to gastrointestinal side effects. We propose the entrapment of perillyl alcohol into poly(D,L-lactic acid)-block-poly(ethylene glycol) (PLA-b-PEG) as delivery platform (entrapment efficiency of 63%-68%). The influence of different concentrations of the tensoactives poly(vinyl alcohol) and sodium cholate (SC) on shear strength and morphology was evaluated by confocal laser scanning microscopy and interfacial tension studies. Only the microcapsules formulated with SC maintained their sphericity when submitted to shear stress. These results indicate that the interface is better organized with SC, conferring mutual stacked packing that is able to better stabilize the organic drop. The in vitro release profile of the drug from the microcapsules was correlated with pore formation and polymer degradation, best fitted to the Baker-Lonsdale model. The loaded microcapsules showed an IC 50 equivalent to that of the free drug (80 μg/mL) after 72 h of exposure. However, after 24 h of exposure, loaded microcapsules showed an IC 50 almost two-fold higher (220 μg/mL) suggesting gradual release., (Copyright © 2019 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.)

Ketonic indeno[1,2-b]indole-9,10-dione derivatives, initially designed as human casein kinase II (CK2) inhibitors, were recently shown to be converted into efficient inhibitors of drug efflux by the breast cancer resistance protein ABCG2 upon suited substitutions including a N (5)-phenethyl on C-ring and hydrophobic groups on D-ring. A series of ten phenolic and seven p-quinonic derivatives were synthesized and screened for inhibition of both CK2 and ABCG2 activities. The best phenolic inhibitors were about threefold more potent against ABCG2 than the corresponding ketonic derivatives, and showed low cytotoxicity. They were selective for ABCG2 over both P-glycoprotein and MRP1 (multidrug resistance protein 1), whereas the ketonic derivatives also interacted with MRP1, and they additionally displayed a lower interaction with CK2. Quite interestingly, they strongly stimulated ABCG2 ATPase activity, in contrast to ketonic derivatives, suggesting distinct binding sites. In contrast, the p-quinonic indenoindoles were cytotoxic and poor ABCG2 inhibitors, whereas a partial inhibition recovery could be reached upon hydrophobic substitutions on D-ring, similarly to the ketonic derivatives.

In this work, we evaluated the cytotoxicity of mesoionic 4-phenyl-5-(2-Y, 4-X or 4-X-cinnamoyl)-1,3,4-thiadiazolium-2-phenylamine chloride derivatives (MI-J: X=OH, Y=H; MI-D: X=NO2, Y=H; MI-4F: X=F, Y=H; MI-2,4diF: X=Y=F) on human hepatocellular carcinoma (HepG2), and non-tumor cells (rat hepatocytes) for comparison. MI-J, M-4F and MI-2,4diF reduced HepG2 viability by ~ 50% at 25 μM after 24-h treatment, whereas MI-D required a 50 μM concentration, as shown by 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyltetrazolium bromide assays. The cytotoxicity was confirmed with lactate dehydrogenase assay, of which activity was increased by 55, 24 and 16% for MI-J, MI-4F and MI-2,4diF respectively (at 25 μM after 24 h). To identify the death pathway related to cytotoxicity, the HepG2 cells treated by mesoionic compounds were labeled with both annexin V and PI, and analyzed by flow cytometry. All compounds increased the number of doubly-stained cells at 25 μM after 24 h: by 76% for MI-J, 25% for MI-4F and MI-2,4diF, and 11% for MI-D. It was also verified that increased DNA fragmentation occurred upon MI-J, MI-4F and MI-2,4diF treatments (by 12%, 9% and 8%, respectively, at 25 μM after 24 h). These compounds were only weakly, or not at all, transported by the main multidrug transporters, P-glycoprotein, ABCG2 and MRP1, and were able to slightly inhibit their drug-transport activity. It may be concluded that 1,3,4-thiadiazolium compounds, especially the hydroxy derivative MI-J, constitute promising candidates for future investigations on in-vivo treatment of hepatocellular carcinoma.

Four series of carbazole derivatives, including N-substituted-hydroxycarbazoles, oxazinocarbazoles, isoxazolocarbazolequinones, and pyridocarbazolequinones, were studied using diverse biological test methods such as a CE-based assay for CK2 activity measurement, a cytotoxicity assay with IPC-81 cell line, determination of MIC of carbazole derivatives as antibacterial agents, a Plasmodium falciparum susceptibility assay, and an ABCG2-mediated mitoxantrone assay. Two oxazinocarbazoles Ib and Ig showed CK2 inhibition with IC50 = 8.7 and 14.0 µM, respectively. Further chemical syntheses were realized and the 7-isopropyl oxazinocarbazole derivative 2 displayed a stronger activity against CK2 (IC50 = 1.40 µM). Oxazinocarbazoles Ib, Ig, and 2 were then tested against IPC-81 leukemia cells and showed the ability to induce leukemia cell death with IC50 values between 57 and 62 μM. Further investigations were also reported on antibacterial and antiplasmodial activities. No significant inhibitory activity on ABCG2 efflux pump was detected.

Efflux transporters play an important role in drug absorption and also in multidrug resistance. ABCG2 (BCRP) is an efflux transporter conferring cross-resistance to mitoxantrone (Mit), irinotecan (CPT11), and its active metabolite SN38. MBLI87, a new ABCG2 inhibitor has proven its efficacy against ABCG2-mediated efflux in vitro and in vivo. This work aimed at modeling and quantifying the cellular interaction between MBLI87 and different substrates using a mechanistic template model. An in vitro competition experiment study was carried out with HEK293 cells overexpressing ABCG2 exposed to fixed concentrations of substrates (Mit, CPT11, SN38) and to MBLI87 at several concentration levels. A nonlinear mixed-effects transport inhibition model was developed to fit intracellular drug concentrations. In this model, drugs cross the cell membrane through passive diffusion, active drug efflux is ABCG2 mediated, interaction between substrates and inhibitor occurs within the transporter. The interaction was found to be noncompetitive. The MBLI87 Ki was estimated to 141 nm for Mit, 289 nm for CPT11, and 1160 nm for SN38. The ratio of intrinsic transport clearance divided by diffusion clearance was estimated to 2.5 for Mit, 1.01 for CPT11, and 5.4 for SN38. The maximal increase in the intracellular substrate concentration that is possible to achieve by inhibition of the transporter was estimated to 1.5 for Mit, 0.1 for CPT11, and 4.4 for SN38. This mechanistic template model describes both drug accumulation and cellular transport, and the mixed-effects approach allows an estimation of intra- and interassay variability. This model is of great interest to study cytotoxic cellular pharmacokinetics., (© 2012 The Authors Fundamental and Clinical Pharmacology © 2012 Société Française de Pharmacologie et de Thérapeutique.)

Background and Purpose: Drugs targeting microtubules are commonly used for cancer treatment. However, the potency of microtubule inhibitors used clinically is limited by the emergence of resistance. We thus designed a strategy to find new cell-permeable microtubule-targeting agents., Experimental Approach: Using a cell-based assay designed to probe for microtubule polymerization status, we screened a chemical library and identified two azaindole derivatives, CM01 and CM02, as cell-permeable microtubule-depolymerizing agents. The mechanism of the anti-tumour effects of these two compounds was further investigated both in vivo and in vitro., Key Results: CM01 and CM02 induced G2/M cell cycle arrest and exerted potent cytostatic effects on several cancer cell lines including multidrug-resistant (MDR) cell lines. In vitro experiments revealed that the azaindole derivatives inhibited tubulin polymerization and competed with colchicines for this effect, strongly indicating that tubulin is the cellular target of these azaindole derivatives. In vivo experiments, using a chicken chorioallantoic xenograft tumour assay, established that these compounds exert a potent anti-tumour effect. Furthermore, an assay probing the growth of vessels out of endothelial cell spheroids showed that CM01 and CM02 exert anti-angiogenic activities., Conclusions and Implications: CM01 and CM02 are reversible microtubule-depolymerizing agents that exert potent cytostatic effects on human cancer cells of diverse origins, including MDR cells. They were also shown to inhibit angiogenesis and tumour growth in chorioallantoic breast cancer xenografts. Hence, these azaindole derivatives are attractive candidates for further preclinical investigations., (© 2012 The Authors. British Journal of Pharmacology © 2012 The British Pharmacological Society.)

The emergence of tumor resistance to conventional microtubule-targeting drugs restricts their clinical use. Using a cell-based assay that recognizes microtubule polymerization status to screen for chemicals that interact with regulators of microtubule dynamics, we identified Pyr1, a cell permeable inhibitor of LIM kinase, which is the enzyme that phosphorylates and inactivates the actin-depolymerizing factor cofilin. Pyr1 reversibly stabilized microtubules, blocked actin microfilament dynamics, inhibited cell motility in vitro and showed anticancer properties in vivo, in the absence of major side effects. Pyr1 inhibition of LIM kinase caused a microtubule-stabilizing effect, which was independent of any direct effects on the actin cytoskeleton. In addition, Pyr1 retained its activity in multidrug-resistant cancer cells that were resistant to conventional microtubule-targeting agents. Our findings suggest that LIM kinase functions as a signaling node that controls both actin and microtubule dynamics. LIM kinase may therefore represent a targetable enzyme for cancer treatment., (©2012 AACR.)

ABCG2 plays a major role in anticancer-drug efflux and related tumor multidrug resistance. Potent and selective ABCG2 inhibitors with low cytotoxicity were investigated among a series of 44 chalcones and analogues (1,3-diarylpropenones), by evaluating their inhibitory effect on the transport of mitoxantrone, a known ABCG2 substrate. Six compounds producing complete inhibition with IC(50) values below 0.5 μM and high selectivity for ABCG2 were identified. The number and position of methoxy substituents appeared to be critical for both inhibition and cytotoxicity. The best compounds, with potent inhibition and low toxicity, contained an N-methyl-1-indolyl (compound 38) or a 6'-hydroxyl-2',4'-dimethoxy-1-phenyl (compound 27) moiety (A-ring) and two methoxy groups at positions 2 and 6 of the 3-phenyl moiety (B-ring). Methoxy substitution contributed to inhibition at positions 3 and 5, but had a negative effect at position 4. Finally, methoxy groups at positions 3, 4, and 5 of the B-ring markedly increased cytotoxicity and, therefore, should be avoided., (© 2012 American Chemical Society)

The ABCG2 multidrug transporter is known to confer cancer cell multidrug resistance by causing the efflux of anticancer drugs; therefore, selective inhibitors have the potential to improve chemotherapeutic treatments. Here, various methoxy derivatives of resveratrol are shown to be potent inhibitors of mitoxantrone efflux by ABCG2: among a series of 11 derivatives, compound 9 (3,5,3',4'-tetramethoxy trans-stilbene) had an IC(50) of 0.16 μM and showed a maximal inhibition of 75%, as measured by flow cytometry. It was not transported, as shown by HPLC fractionation and mass spectrometry titration and the lack of any cross-resistance in cell survival experiments. Compound 9 had a very low intrinsic cytotoxicity and was able to chemosensitize the growth of resistant ABCG2-transfected HEK293 cells at submicromolar concentrations. Drug-efflux inhibition was specific for ABCG2 since very low effects were observed with ABCB1 and ABCC1. The action mechanism of compound 9 was different from that of GF120918, which produced a complete and partly competitive but not ABCG2-specific inhibition, since ABCB1 was even more strongly inhibited. The two inhibitors also displayed different effects on the ABCG2 vanadate-sensitive ATPase activity, suggesting that they either bound to distinct sites or induced different conformational changes. Mitoxantrone efflux was fully inhibited by combining low concentrations of compound 9 with either GF120918 or a transport substrate such as prazosin or nilotinib. We conclude that methoxy derivatives of stilbene are good candidates for investigating future in vivo modulation of ABCG2 drug-efflux activity.

A series of 13 disubstituted chromones was synthesized. Two types of substituents, on each side of the scaffold, contributed to both the potency of ABCG2 inhibition and the cytotoxicity. The best compound, 5-(4-bromobenzyloxy)-2-(2-(5-methoxyindolyl)ethyl-1-carbonyl)-4H-chromen-4-one (6g), displayed high-affinity inhibition and low cytotoxicity, giving a markedly high therapeutic index. The chromone derivative specifically inhibited ABCG2 versus other multidrug ABC transporters and was not transported. It constitutes a highly promising candidate for in vivo chemosensitization of ABCG2-expressing tumors.

The commercialization of medicinal plants, as recognized in their uses by the nutraceutical, cosmeceutical, and pharmaceutical industries, is gaining more popularity and interest around the globe. The plant family Amaryllidaceae has a long history in the traditional medicinal system and is used to treat diverse diseases. In Brazil, the Crinum americanum L. has been applied by riverside communities for cancer treatment. In this study, the lipid fractions (LF) of leaves of C. americanum L., obtained by Soxhlet (SX) and ultrasonic bath (UAE), were characterized by gas chromatography–mass spectrometry (GC-MS) and evaluated for their anti-diabetic properties, antiglycante, antioxidant, and cytotoxic potential. The extraction yield was higher for UAE (9.45%) than SX (5.99%). Furthermore, the LF obtained by UEA had a higher content of unsaturated fatty acids (73.34%) when compared to the SX (48.94%). However, compounds extracted by both methods showed in vitro anti-diabetic, antioxidant, and anticancer activity against a lung cancer cell line. These results demonstrate that UAE can be used as an efficient and important method in relation to the SX, due to the preservation of the functional properties, reduction of time, and amount of solvent used to extract fatty acids. [Display omitted] • The extractions performed by UAE showed a higher content of unsaturated fatty acids. • The LF obtained by UAE comprises 42.13% omega-6% and 31.21% omega-3. • The LF obtained by UAE and SX is a promoting anti-diabetic and antiglycant agent. • LF obtained by UAE and SX showed a cytotoxic effect on the H460 cell line. [ABSTRACT FROM AUTHOR]

Breast cancer resistance protein (BCRP/ABCG2) is one of the major transporters involved in the efflux of anticancer compounds, contributing to multidrug resistance (MDR). Inhibition of ABCG2-mediated transport is then considered a promising strategy for overcoming MDR in tumors. We recently identified a chromone derivative, namely MBL-II-141 as a selective ABCG2 inhibitor, with relevant in vivo activity. Here, we report the pharmacomodulation of MBL-II-141, with the aim of identifying key pharmacophoric elements to design more potent selective and non-toxic inhibitors. Through rational structural modifications of MBL-II-141, using simple and affordable chemistry, we obtained highly active and easily-made inhibitors of ABCG2. Among the investigated compounds, derivative 4a , was found to be 3-fold more potent than MBL-II-141. It was similarly efficient as the reference inhibitor Ko143 but with the advantage of a lower intrinsic cytotoxicity, and therefore constitutes the best ABCG2 inhibitor ever reported displaying a very high therapeutic ratio. [ABSTRACT FROM AUTHOR]