Breast Cancer Resistance Protein Protein Research Articles

Hypoxia modulates P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) drug transporters in brain endothelial cells of the developing human blood-brain barrier

P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP) multidrug resistance (MDR) transporters are localized at the luminal surface of the blood-brain barrier (BBB). They confer fetal brain protection against harmful compounds that may be circulating in the peripheral blood. The fetus develops in low oxygen levels; however, some obstetric pathologies such as pre-eclampsia, placenta accreta/previa may result in even greater fetal hypoxic states. We investigated how hypoxia impacts MDR transporters in human fetal brain endothelial cells (hfBECs) derived from early and mid-stages of pregnancy. Hypoxia decreased BCRP protein and activity in hfBECs derived in early pregnancy. In contrast, in hfBECs derived in mid-pregnancy there was an increase in P-gp and BCRP activity following hypoxia. Results suggest a hypoxia-induced reduction in fetal brain protection in early pregnancy, but a potential increase in transporter-mediated protection at the BBB during mid-gestation. This would modify accumulation of various key physiological and pharmacological substrates of P-gp and BCRP in the developing fetal brain and potentially contribute to the pathogenesis of neurodevelopmental disorders commonly associated with in utero hypoxia.

Method for Testing of Drugs Belonging to Substrates and Inhibitors of the Transporter Protein BCRP on Caco-2 Cells

Introduction. Breast cancer resistance protein (BCRP) is an efflux membrane transporter that controls the pharmacokinetics of a large number of drugs. Its activity may change when taking some endo- and exogenous substances, thus making it a link in drug interactions.Aim. The aim of the study was to develop a method for testing of drugs for belonging to BCRP substrates and inhibitors in vitro.Materials and methods. The work was performed on Caco-2 cells overexpressing BCRP, the cultivation was performed in a transwell-system consisting of the apical and basolateral chambers. Cells were seeded at the bottom of the apical chamber, which is a semipermeable membrane. Primarily, the transport of BCRP substrates: methotrexate, mitoxantrone and quercetin was evaluated in the concentration range of 1, 5, 10, and 50 μM in the direction from the basal chamber to the apical one (Papp b-a) and in the opposite direction (Papp a-b). The ratio Papp b-a / Papp a-b more than «2» characterizes the participation of transporter proteins in the transcellular transport of substances. To confirm the participation of BCRP in their transport the experiment was carried out with the addition of a transporter inhibitor, reserpine, to the transport medium at a concentration of 50 μM. The concentration of substrates in the chambers was analyzed by HPLC-MS/MS.Results and their discussion. The addition of methotrexate (1 μM), mitoxantrone (1 μM), and quercetin (1–10 μM) to both the apical or basolateral chambers of the transwell-system, their content in the recipient chamber was not detected. When methotrexate concentration became 5 μM the Papp b-a / Papp a-b ratio was 3.38 ± 0.08, which indicates the involvement of transporters in its transfer. The addition of methotrexate to the donor chamber at concentrations of 10 and 50 μM, Papp b-a / Papp a-b decreased to values below «2». At mitoxantrone concentration of 5 μM Papp b-a / Papp a-b was 2.72 ± 0.16. An increase in the concentration to 10 μM led to an increase in Papp b-a / Papp a-b to 6.18 ± 0.08. With a substance content of 50 μM the indicator decreased but remained above the value «2». In the quercetin concentration of 50 microns, Papp b-a / Papp was below "2". Reserpine reduced Papp b-a / Papp a-b of methotrexate by 3.31 times (p = 0.0002), which indicates the elimination of asymmetry in the transport of the substance. At a mitoxantrone concentration of 10 microns, reserpine reduced its Papp b-a / Papp a-b by 3.36 times (p < 0.0001). The results indicate the participation of BCRP in the control of the transfer of both substances through the cellular monolayer.Conclusion. A method of testing drugs belonging to BCRP substrates and inhibitors using methotrexate (5 μM) and mitoxantrone (10 μM) as marker substrates and reserpine (50 μM) as inhibitor was developed and tested on Caco-2 cells.

Regulation of BCRP expression and sulfasalazine pharmacokinetics by the nuclear receptor REV-ERBα

BCRP (breast cancer resistance protein) is a crucial efflux transporter involved in the regulation of the pharmacokinetics and pharmacodynamics of a wide range of drugs. Herein, we aimed to investigate a potential role for the nuclear receptor REV-ERBα in the regulation of BCRP expression and sulfasalazine (a BCRP probe substrate) pharmacokinetics. Regulation of BCRP expression by REV-ERBα was assessed using Rev-erbα -/- mice and AML12 and CT26 cells. Pharmacokinetic analysis was performed with Rev-erbα -/- and wild-type mice after sulfasalazine administration. We found that the expression levels of BCRP mRNA and protein were downregulated in the liver and small intestine of Rev-erbα-dificient mice. In line with this, Rev-erbα ablation increased the systemic exposures of oral sulfasalazine. Positive regulation of BCRP expression and function by REV-ERBα was furtherly confirmed in AML12 and CT26 cells. Moreover, indirect regulation of Bcrp expression by REV-ERBα was potentially mediated by a negative transcription factor DEC2, which is a downstream target of REV-ERBα. In conclusion, REV-ERBα positively regulates BCRP expression in mice, thereby affecting sulfasalazine pharmacokinetics.

Reduction in ABCG2 mRNA Expression in Human Immortalised Brain Microvascular Endothelial Cells by Ferric Ammonium Citrate is Mediated by Reactive Oxygen Species and Activation of ERK1/2 Signalling.

The ATP-binding cassette (ABC) transport protein ABCG2 (also known as breast cancer resistance protein (BCRP)) is expressed at the luminal face of the blood-brain barrier (BBB), where it limits the brain uptake of a number of therapeutic drugs. We recently reported that the ABC efflux transporter P-glycoprotein (P-gp) was downregulated in human immortalised brain endothelial (hCMEC/D3) cells treated with ferric ammonium citrate (FAC). The aim of the present study, therefore, was to assess whether BCRP expression is also affected by FAC and identify any signalling mechanisms involved. ABCG2 mRNA was assessed by RT-qPCR. Protein levels of BCRP, phosphorylated extracellular-regulated kinases 1 and 2 (p-ERK1/2) and total ERK 1/2 were assessed by Western blot. Reactive oxygen species (ROS) levels were determined using 2',7'-dichlorofluorescin diacetate. Treatment of hCMEC/D3 cells with FAC (250 µM, 72 h) significantly reduced ABCG2 mRNA levels (32.2 ± 3.7%) without a concomitant reduction in BCRP protein expression. ABCG2 mRNA levels were restored to control levels when co-treated with the antioxidant N-acetylcysteine (NAC), suggesting the effect of FAC was mediated by a ROS-sensitive pathway. We also found that FAC-treatment was associated with increased levels of p-ERK1/2, suggesting involvement of the ERK1/2 signalling pathway in the observed ABCG2 mRNA downregulation. The ERK1/2 signalling pathway inhibitor U0126 restored p-ERK1/2 levels and partially attenuated the FAC-induced reduction in ABCG2 mRNA. This study suggests that FAC-induced downregulation of ABCG2 mRNA isdriven byROS and ERK1/2 signalling, mechanisms which may be exploited to modulate BCRP expression at the BBB.

Quantitative Comparison of Breast Cancer Resistance Protein (BCRP/ABCG2) Expression and Function Between Maternal Blood-Brain Barrier and Placental Barrier in Mice at Different Gestational Ages

Breast cancer resistance protein (BCRP) is expressed by brain capillary endothelial cells and at the interface between two placental syncytiotrophoblast layers in rodents and serves to suppress drug distribution to the brain and the fetus. The purpose of the present study is to determine and compare the apparent impact of a single BCRP molecule on drug transfer between the maternal blood-brain barrier and placental barrier in pregnant mice at different gestation ages. BCRP protein was quantified by liquid chromatography-tandem mass spectrometry. Genistein or dantrolene was continuously administered to pregnant Bcrp−/− or wild-type (WT) mice, and the brain-to-plasma concentration ratio in the mother (Kp,brain) and the fetal-to-maternal ratio of plasma concentrations (Kp,fp) were determined. At gestational day 15.5 (GD15.5), the protein amount of BCRP at the murine placental barrier was estimated to be approximately three times higher than at the maternal blood-brain barrier, but the levels were approximately the same at GD17.5 due to the decline of placental BCRP expression during gestation. On the other hand, the values of Bcrp−/−/WT ratio of Kp,brain for genistein and dantrolene were 6.1 and 3.8, respectively, while the Kp,fp ratios were all less than 2.0. These results indicate that the apparent impact of a single placental BCRP molecule on the restriction of drug distribution is much less than that of a single brain BCRP molecule, probably because the function of placental BCRP is attenuated by bypass transfer through the connexin26 gap junctions between adjacent syncytiotrophoblast layers. The present study also found that the expression amount of BCRP protein at the human placental barrier formed by the monolayer of syncytiotrophoblasts was lower than that in mice, but this species difference appears to be functionally compensated by the murine-specific bypass route through gap junctions, at least in part.

Fetal Membranes Contribute to Drug Transport across the Feto-Maternal Interface Utilizing the Breast Cancer Resistance Protein (BCRP).

During pregnancy, the placenta is established as a primary organ for drug transport at the maternal-fetal interface. The fetal membranes (FM) also form an interface with maternal tissues; however, their role in drug transport has not been previously investigated. Knowledge of drug transport across this feto-maternal interface along with the placenta can improve new drug development and testing for use during pregnancy. We also hypothesize that extracellular vesicles (exosomes 30–160 nm) released from the FM and placental cells may also contain drug transport proteins and might impact drug trafficking across the feto-maternal interfaces. The objectives were to (1) localize the breast cancer resistance protein (BCRP) in human FM; (2) determine the drug transport function of BCRP in chorion trophoblast cells (CTCs) of the FM; and (3) investigate the presence of BCRP in FM cell-derived exosomes, as a paracrine modifier of the tissue environment for transport functions. The gene and protein expressions of ABCG2/BCRP in FMs were determined by quantitative real-time PCR (qRT-PCR) and western blotting (WB) and were localized by immunohistochemistry (IHC). The surface expression of BCRP in FM cells was determined by flow cytometry. The functional role of BCRP was assessed by an EFFLUX dye multidrug resistance assay. The presence of BCRP in exosomes derived from CTCs and BeWo cells was examined using ExoView®. Data derived from CTCs are compared with placental trophoblast cells (BeWo). BCRP is expressed and localized in the fetal membrane, primarily in the chorion trophoblast cell layer and scarcely in the amnion epithelial layer (AEC), and primarily localized on both AEC and CTC cell surfaces. Efflux assay data showed that FM cells have similar drug resistance activity as BeWo cells, suggesting that FM also have drug transportation capabilities. BeWo- and CTC-derived exosomes expressed limited BCRP protein on the surface, so it was predominantly contained in the exosomal lumen. As far as we are aware, this is the first study to report BCRP expression in fetal membrane cells and as cargo in fetal membrane-derived exosomes. We report that fetal membrane cells are capable of drug transportation. Based on these results, investigational drug trials should include the FM and its exosomes as possible drug transportation routes in pregnancy.

Bile duct ligation causes opposite impacts on the expression and function of BCRP and P-gp in rat brain partly via affecting membrane expression of ezrin/radixin/moesin proteins.

Breast cancer resistance protein (BCRP) and P-glycoprotein (P-gp) are co-located at blood-brain barrier (BBB) cells, preventing their substrates from entering brain. Accumulating evidence demonstrates that liver failure impairs P-gp and BCRP expression and function in the brain. In the current study, we investigated how liver failure influenced the expression and function of brain BCRP and P-gp in rats subjected to bile duct ligation (BDL). The function of BCRP, P-gp and BBB integrity was assessed using distribution of prazosin, rhodamine 123 and fluorescein, respectively. We showed that BDL significantly decreased BCRP function, but increased P-gp function without affecting BBB integrity. Furthermore, we found that BDL significantly downregulated the expression of membrane BCRP and upregulated the expression of membrane P-gp protein in the cortex and hippocampus. In human cerebral microvascular endothelial cells, NH4Cl plus unconjugated bilirubin significantly decreased BCRP function and expression of membrane BCRP protein, but upregulated P-gp function and expression of membrane P-gp protein. The decreased expression of membrane BCRP protein was linked to the decreased expression of membrane radixin protein, while the increased expression of membrane P-gp protein was related to the increased location of membrane ezrin protein. Silencing ezrin impaired membrane location of P-gp, whereas silencing radixin impaired membrane location of BCRP protein. BDL rats showed the increased expression of membrane ezrin protein and decreased expression of membrane radixin protein in the brain. We conclude that BDL causes opposite effects on the expression and function of brain BCRP and P-gp, attributing to the altered expression of membrane radixin and ezrin protein, respectively, due to hyperbilirubinemia and hyperammonemia.

Functional Alterations of Multidrug Resistance-Associated Proteins 2 and 5, and Breast Cancer Resistance Protein upon Snail-Induced Epithelial-Mesenchymal Transition in HCC827 Cells.

Our previous report indicated that Snail-induced epithelial-mesenchymal transition (EMT) enhanced P-glycoprotein (P-gp) function and drug resistance to P-gp substrate anticancer drug in a human non-small cell lung cancer (NSCLC) cell line, HCC827. Our objective is to evaluate the changes in the mRNA and protein expression levels and the functions of multidrug resistance-associated protein (MRP) 2, MRP5 and breast cancer resistance protein (BCRP). Snail-expressing HCC827 cells showed increased mRNA levels of Snail and a mesenchymal marker vimentin, and decreased mRNA levels of an epithelial marker E-cadherin after transduction, indicating that Snail had induced EMT consistent with our previous reports. The mRNA level of MRP2 was significantly decreased, while that of MRP5 remained unchanged, in Snail-expressing cells. The expression levels of MRP2 and MRP5 proteins in whole-cell homogenate were unchanged in Snail-expressing cells, but MRP5 protein showed significantly increased membrane localization. Snail-transduction increased the efflux transport of 5-(and-6)-carboxy-2',7'-dichlorofluorescein (CDCF), a substrate of MRP2, 3 and 5. This increase was blocked by MK571, which inhibits MRP1, 2, and 5. Toxicity of cisplatin, a substrate of MRP2 and 5, was significantly decreased in Snail-expressing cells. BCRP mRNA and protein levels were both decreased in Snail-expressing cells, which showed an increase in the intracellular accumulation of 7-ethyl-10-hydroxycamptothecin (SN-38), a BCRP substrate, resulting in reduced viability. These results suggested that MRP5 function appears to be increased via an increase in membrane localization, whereas the BCRP function is decreased via a decrease in the expression level in HCC827 cells with Snail-induced EMT.

Studies on pharmacokinetic properties and absorption mechanism of phloretin: In vivo and in vitro

Phloretin is a natural dihydrochalcone flavonoid that is mainly distributed in apple, pear and other juicy fruit peels or root peels. Phloretin exhibits several pharmacological properties, such as antidiabetic, antioxidant, anti-inflammatory, and antitumor activities. However, the poor water solubility of phloretin limits its application in the treatment of numerous diseases. To date, the underlying mechanisms of phloretin absorption have not been investigated. In this study, the pharmacokinetics of phloretin orally administered to Sprague-Dawley (SD) rats were examined, and the absorption mechanisms of phloretin were investigated in a Caco-2 cell monolayer and single-pass intestinal perfusion in SD rat. The effects measured by basic parameters, such as compound concentration, time, temperature, paracellular pathway, in different intestinal segments were analyzed, and various inhibitors, such as the P-glycoprotein (P-gp) inhibitor verapamil, the multidrug resistance protein 2 (MRP2) inhibitor indomethacin, the breast cancer resistance protein (BCRP) inhibitor reserpine, and the closely related regulator EDTA, were evaluated to determine their effects on the absorption of phloretin. The pharmacokinetics of phloretin was studied by oral and intravenous injection in rats. The bioavailability was 8.676 %.The SPIP experiments showed that P-gp, MRP2, BCRP protein inhibitor and closely related regulator, could significantly increase the apparent permeability coefficient (Papp) of phloretin. Monolayer transport experiments in Caco-2 cells showed that P-gp, MRP2 protein inhibitor and closely related regulator EDTA, significantly increased the Papp value of phloretin. In conclusion, phloretin is a substrate of P-gp and MRP2, and its modes of transport include active transport, efflux protein transport and cell bypass.

Short-chain fatty acids exert opposite effects on the expression and function of p-glycoprotein and breast cancer resistance protein in rat intestine.

P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) are involved in intestinal barrier. Short-chain fatty acids (SCFAs) play important roles in maintaining intestinal barrier. In this study we explored how SCFAs affected the expression and function of intestinal P-gp and BCRP in rats. Rats received 150 mM acetate, propionate or butyrate in drinking water for 4 weeks. In SCFA-treated rats, the expression and function of intestinal P-gp were decreased, but those of intestinal BCRP were increased; intestinal p-p65 was also decreased, which was positively related to P-gp protein expression. Among the three SCFAs tested, butyrate exhibited the strongest induction or inhibitory effect, followed by propionate and acetate. Similar results were observed in mouse primary enterocytes and Caco-2 cells treated with acetate (5 mM), propionate (2 mM), or butyrate (1 mM). In Caco-2 cells, addition of butyrate, vorinostat, and valproate (two classic HDAC inhibitors), Bay117082 (selective inhibitor of NF-κB activation) or NF-κB p65 silencing significantly decreased the expression of P-gp and the level of phosphorylated p65 (p-p65). Furthermore, butyrate attenuated the expression of P-gp and p-p65 induced by TNF-α (NF-κB activator) and theophylline (HDAC activator). However, vorinostat, valproate, Bay117082, TNF-α or p65 silencing hardly affected BCRP protein expression. But GW9662 (selective PPARγ antagonist) or PPARγ silencing abolished BCRP induction by butyrate and troglitazone (PPARγ agonist). SCFAs-treated rats showed higher intestinal protein expression of PPARγ, which was positively related to BCRP protein expression. Butyrate increased plasma exposure of fexofenadine but decreased that of rosuvastatin following oral dose to rats. In conclusion, SCFAs exert opposite effects on the expression and function of intestinal P-gp and BCRP; butyrate downregulated P-gp expression and function possibly via inhibiting HDAC/NF-κB pathways; butyrateinduced BCRP expression and function partly via PPARγ activation.

A Combination of Clioquinol, Zinc and Copper Increases the Abundance and Function of Breast Cancer Resistance Protein in Human Brain Microvascular Endothelial Cells

Modulating the abundance of the blood-brain barrier (BBB) efflux transporter breast cancer resistance protein (BCRP) has the potential to impact brain levels of drugs and endogenous substrates. Studies have demonstrated that the metal ionophore clioquinol (CQ) increases BBB abundance of P-glycoprotein (P-gp), an effect associated with increased endothelial cell levels of Cu2+. This study therefore assessed whether human brain endothelial (hCMEC/D3) cell abundance and function of BCRP is modulated by CQ. hCMEC/D3 cells were treated with CQ, Zn2+ and Cu2+ (CZC) (0.5 μM, 0.5 μM, 0.1 μM, respectively) for 24 h and BCRP mRNA and protein abundance was determined by Western blot and qPCR, respectively. After a series of optimisation studies assessing specificity of bodipy prazosin (BP) and Ko143 as a substrate and inhibitor of BCRP, respectively, the impact of CZC on BP uptake was assessed. While CZC did not increase mRNA expression of BCRP, BCRP abundance was increased 1.8 ± 0.1-fold; this was associated with a 68.1 ± 3.3% reduction in accumulation of BP in hCMEC/D3 cells. This is the first study to demonstrate that augmenting metal ion availability enhances protein abundance and function of BCRP at the BBB, which may be exploited to modulate CNS access of therapeutics and endogenous substrates.

Effect of GenX on P-Glycoprotein, Breast Cancer Resistance Protein, and Multidrug Resistance-Associated Protein 2 at the Blood-Brain Barrier.

Background:Ammonium 2,3,3,3-tetrafluoro-2-(heptafluoropropoxy)propanoic acid (GenX) is a replacement for perfluorooctanoic acid in the production of fluoropolymers used in a variety of consumer products. GenX alters fetal development and antibody production and elicits toxic responses in the livers and kidneys of rodents. The GenX effect on the blood–brain barrier (BBB) is unknown. The BBB protects the brain from xenobiotic neurotoxicants and harmful endogenous metabolites.Objectives:We aimed to investigate the effects of GenX on the transport activity and expression of P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), and multidrug resistance–associated protein 2 (MRP2) at the BBB.Methods:Transporter activities were measured in isolated rat brain capillaries by a confocal microscopy–based method. ATPase (enzymatic hydrolysis of adenosine triphosphate to inorganic phosphate) levels were measured in vitro. Western blotting determined P-gp and BCRP protein levels. Cell survival after GenX exposure was determined for two human cell lines.Results:Nanomolar levels of GenX inhibited P-gp and BCRP but not MRP2 transport activities in male and female rat brain capillaries. P-gp transport activity returned to control levels after GenX removal. GenX did not reduce P-gp- or BCRP-associated ATPase activity in an in vitro transport assay system. Reductions of P-gp but not BCRP transport activity were blocked by a peroxisome proliferator–activated receptor () antagonist. GenX reduced P-gp and BCRP transport activity in human cells.Conclusion:In rats, GenX at rapidly (in 1–2 h) inhibited P-gp and BCRP transport activities at the BBB through different mechanisms. was required for the GenX effects on P-gp but not BCRP transport activity. https://doi.org/10.1289/EHP5884

Talazoparib nanoparticles for overcoming multidrug resistance in triple-negative breast cancer.

Herein, we investigated efflux pumps-mediated talazoparib-resistance in the treatment of triple-negative breast cancer (TNBC). Furthermore, we produced a novel talazoparib-solid lipid nanoparticles (SLNs) and then explored in vitro therapeutic efficacy of talazoparib-SLNs to overcome talazoparib-resistance in TNBC cells. Talazoparib-SLNs formulation was produced and then characterized. Calcein and Rho-123 were used to analyze the functional activity of drug efflux pumps in these cells. Additionally, RT-PCR, western blot and immunofluorescence analysis were used to detect the messenger RNA, and protein expression level, and cellular localization of the multidrug resistance (MDR1), breast cancer resistance protein (BCRP), and MRP1. We found that talazoparib efflux was mediated by BCRP and MRP1 pumps in TNBC cells. Talazoparib-SLNs could significantly enhance therapeutic efficacy of talazoparib. Furthermore, talazoparib-SLNs were more effective in the suppression of MDR1, BCRP, and MRP1 gene and protein expression levels than talazoparib. Consequently, this study suggests that talazoparib-SLNs formulation represents a promising therapeutic carrier to reverse MDR-mediated resistance in TNBC.

Cytosolic phospholipase A2 is a key regulator of blood‐brain barrier function in epilepsy

Blood-brain barrier dysfunction in epilepsy contributes to seizures and resistance to antiseizure drugs. Reports show that seizures increase brain glutamate levels, leading to barrier dysfunction. One component of barrier dysfunction is overexpression of the drug efflux transporters P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP). Based on our previous studies, we hypothesized that glutamate released during seizures activates cytosolic phospholipase A2 (cPLA2), resulting in P-gp and BCRP overexpression. We exposed isolated rat brain capillaries to glutamate ex vivo and used an in vivo-ex vivo approach of isolating brain capillaries from rats after status epilepticus (SE) and in chronic epileptic (CE) rats. Glutamate increased cPLA2, P-gp, and BCRP protein and activity levels in isolated brain capillaries. We confirmed the role of cPLA2 in the signaling pathway in brain capillaries from male and female mice lacking cPLA2. We also demonstrated, in vivo, that cPLA2 inhibition prevents overexpression of P-gp and BCRP at the blood-brain barrier in rats after status epilepticus and in CE rats. Our data support the hypothesis that glutamate signals cPLA2 activation, resulting in overexpression of blood-brain barrier P-gp and BCRP.-Hartz, A. M. S., Rempe, R. G., Soldner, E. L. B., Pekcec, A., Schlichtiger, J., Kryscio, R., Bauer, B. Cytosolic phospholipase A2 is a key regulator of blood-brain barrier function in epilepsy.

2500. Fostemsavir Drug–Drug Interaction Profile, an Attachment Inhibitor and Oral Prodrug of Temsavir, for Heavily Treatment Experienced HIV-1-Infected Patients

BackgroundFostemsavir (FTR) is a first-in-class attachment inhibitor being evaluated in heavily treatment-experienced (HTE) HIV-1-infected patients. Active temsavir (TMR) binds to viral envelope glycoprotein 120 and prevents viral attachment and entry into host CD4+ T cells. TMR is primarily metabolized by esterase-mediated hydrolysis with contributions from cytochrome P450 (CYP) 3A4. TMR does not inhibit/induce major CYP or uridine diphosphate glucuronosyltransferase (UGT) enzymes and is a P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) substrate. TMR and/or its metabolites inhibit BCRP and organic anion transporter protein 1B1/3 (OATP1B1/3). FTR DDI profile informs coadministration with antiretrovirals (ARV) and other therapeutic classes.MethodsDDI data from 13 studies were compiled to inform the impact of 17 drugs or drug combinations on TMR and the impact of TMR on 15 drugs such as ARVs, rifamycins, opioid substitutes, statins, oral contraceptives (OC), and H2-antagonsits.ResultsFTR with CYP3A4, P-gp, and/or BCRP inhibitors increase TMR concentrations; but, do not pose clinical concern at therapeutic dose. TMR may be administered with weak/moderate inducers with or without coadministration of CYP3A4, P-gp, and/or BCRP inhibitors such as RTV or COBI. Coadministration with strong inducers is contraindicated. FTR may be coadministered with RBT with or without a PK enhancer. However, co-administration of FTR with RIF is contraindicated. FTR can be given with drugs that increase gastric pH; famotidine did not impact TMR PK. TMR may increase concentrations of drugs that are substrates of OATP1B1/3 and BCRP; therefore, most statins require dose reduction (e.g., rosuvastatin dose is limited to ≤10 mg QD). TMR increased EE exposure 40% with no impact on NE; therefore, FTR may be coadministered with OCs containing ≤30 µg EE. TMR had no clinically meaningful impact on TDF, DRV/RTV, ATV/RTV, ATV, RTV, ETR, MET, or BUP/norBUP PK (Table 1).ConclusionFTR can be coadministered with ARVs and most common treatments used to manage HIV co-infections or comorbidities without dose adjustment of either drug except for select HMG-CoA reductase inhibitors and EE-containing OCs. Strong CYP3A inducers are contraindicated. Disclosures All authors: No reported disclosures.

Chemo-sensitizing activity of natural cadinanes from Heterotheca inuloides in human uterine sarcoma cells and their in silico interaction with ABC transporters

Sensitizing activities exerted by 3,4-dihydro-7-hydroxycadalene (1), rac-3,7-dihydroxy-3(4H)-isocadalen-4-one (4) and (1R,4R)-4H-1,2,3,4-tetrahydro-1-hydroxycadalen-15-oic acid (9), the major cadinanes isolated from Heterotheca inuloides, towards multidrug-resistant MES-SA/MX2 and parental MES-SA epithelial human uterine sarcoma cell lines were evaluated. We also evaluated the in silico interactions (expressed as ΔGbinding in kcal/mol) of cadinanes 1, 4 and 9 in an in vitro assay, and also tested several structurally related natural compounds with the multidrug resistance protein (MDR1, P-glycoprotein), human multidrug resistance protein 1 (MRP1), and breast cancer resistance protein (BCRP) structures as pharmacological targets using AutoDock and AutoDock Vina. Compound 1 potentiated the cytotoxicity of doxorubicin and mitoxantrone drugs in resistant MES-SA/MX2 cells, compared to cells treated with each drug alone. Compound 1 could reverse the resistance to doxorubicin 12.44 fold at a concentration of 5 μM. It also re-sensitized cells to mitoxantrone 3.94 fold. Hence, compound 1 may be considered as a potential chemosensitizing agent to overcome multidrug resistance in cancer. The docking analysis suggested that there are interactions between cadinanes from H. inuloides and MDR1, MRP1, and BCRP proteins mainly through π-π interactions and hydrogen bonds.

TGF-β1 elevates P-gp and BCRP in hepatocellular carcinoma through HOTAIR/miR-145 axis.

Multidrug resistance (MDR) is common in patients and has been linked to transforming growth factor-β1 (TGF-β1) and overexpression of drug efflux transporters P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP), although the molecular mechanisms remain largely unknown. This study aimed to investigate the mechanisms underlying TGF-β1-induced MDR in hepatocellular carcinoma (HCC) cells. It was found that TGF-β1 upregulated HOX transcript antisense RNA (HOTAIR) expression in HCC cells. When drosophila mothers against decapentaplegic 4 (SMAD4) was silenced, HOTAIR expression was accordingly reduced. Meanwhile, miR-145 expression was increased in the case HOTAIR was silenced. If the enhancer of zeste homolog 2 (EZH2) was knocked down using small interfering RNA (siRNA), miR-145 expression was decreased. Then, the regulatory role of miR-145 in P-gp and BCRP expression was explored. The results showed that the expression of P-gp and BCRP protein was suppressed by miR-145 through binding to the 3'-untranslated regions (3'-UTRs) of P-gp and BCRP. In conclusion, our study revealed a novel mechanism explaining TGF-β1-induced MDR in HCC through upregulating P-gp and BCRP via the SMAD4/HOTAIR/miR-145 axis.

Expressions of FHIT, BCRP and Bcl-2 Proteins in Breast Invasive Ductal Carcinoma

Objective: To explore the expressions of FHIT (Human fragile histidine triad), BCRP (breast cancer resistance protein) and Bcl-2 proteins in breast invasive ductal carcinoma (IDC) and its relationship with clinical pathological factors. Methods: The expressions of FHIT, BCRP and Bcl-2 proteins in 84 cases of intraoperative resection of primary breast IDC and 36 cases of normal breast tissue about 3 cm away from the neoplastci foci were detected with the method of immunohistochemical streptavidin-peroxidase (SP) to analyze the relationship between the three proteins and the pathological features of breast IDC. Results: The positive expression rates of FHIT, of BCRP and Bcl-2 were 42.86%, 72.62% and 61.90% respectively in the breast IDC group and 72.22%, 36.11% and 38.89 % respectively in the normal breast tissue control group, between which the differences were statistically significant (P <0.05). In the IDC group, the expression of the three proteins was related to the lymph nodes metastasis and tumor recurrence of breast IDC, but was not significantly correlated with the expression of estrogen receptor (ER), progesterone receptor (PR) and proto-oncogene human epidermal growth factor receptor 2 (Her-2). The expression of FHIT was negatively correlated with the expression of and Bcl-2 (r = -0.322, -0.389), but BCRP and Bcl-2 expression were positively correlated (r = 0.276). Conclusion: The abnormal expressions of FHIT, BCRP and Bcl-2 proteins in breast IDC may play an important role in its onset and development.

Placental BCRP/ABCG2 Transporter Prevents Fetal Exposure to the Estrogenic Mycotoxin Zearalenone.

In the placenta, the breast cancer resistance protein (BCRP)/ABCG2 efflux transporter limits the maternal-to-fetal transfer of drugs and chemicals. Previous research has pointed to the estrogenic mycotoxin zearalenone as a potential substrate for BCRP. Here, we sought to assess the role of the BCRP transporter in the transplacental disposition of zearalenone during pregnancy. In vitro transwell transport assays employing BCRP/Bcrp-transfected Madine-Darby canine kidney cells and BeWo trophoblasts with reduced BCRP expression were used to characterize the impact of BCRP on the bidirectional transport of zearalenone. In both models, the presence of BCRP protein increased the basolateral-to-apical transport and reduced the apical-to-basolateral transport of zearalenone over a 2-h period. In vivo pharmacokinetic analyses were then performed using pregnant wild-type and Bcrp-/- mice after a single tail vein injection of zearalenone. Zearalenone and its metabolite α-zearalenol were detectable in serum, placentas, and fetuses from all animals, and β-zearalenol was detected in serum and fetuses, but not placentas. There were no significant differences in the maternal serum concentrations of any analytes between the two genotypes. In Bcrp-/- mice, the free fetal concentrations of zearalenone, α-zearalenol, and β-zearalenol were increased by 115%, 84%, and 150%, respectively, when compared with wild-type mice. Concentrations of free zearalenone and α-zearalenol were elevated 145% and 78% in Bcrp-/- placentas, respectively, when compared with wild-type placentas. Taken together, these data indicate that the placental BCRP transporter functions to reduce the fetal accumulation of zearalenone, which may impact susceptibility to developmental toxicities associated with in utero zearalenone exposure.

Total hepatocellular disposition profiling of rosuvastatin and pitavastatin in sandwich-cultured human hepatocytes

This study describes the total disposition profiling of rosuvastatin (RSV) and pitavastatin (PTV) using a single systematic procedure called D-PREX (Disposition Profile Exploration) in sandwich-cultured human hepatocytes (SCHH). The biliary excretion fractions of both statins were clearly observed, which were significantly decreased dependent on the concentration of Ko143, an inhibitor for breast cancer resistance protein (BCRP). Ko143 also decreased the basolateral efflux fraction of RSV, whereas that of PTV was not significantly affected. To understand these phenomena, effects of Ko143 on biliary excretion (BCRP and multidrug resistance-associated protein (MRP) 2) and basolateral efflux (MRP3 and MRP4) transporters were examined using transporter-expressing membrane vesicles. BCRP, MRP3 and MRP4-mediated transport of RSV was observed, and Ko143 inhibited these transporters except MRP3. BCRP and MRP4 also mediated the transport of PTV, but the Ko143-mediated inhibition was only clear for BCRP. These results might explain the Ko143-mediated complete and partial inhibition of the biliary excretion and the basolateral efflux of RSV, respectively, in SCHH. In conclusion, D-PREX with sequential sampling of supernatants prior to cell lysis enables the evaluation of total drug disposition profiles resulting from complex interplays of intracellular pathways, which would provide high-throughput evaluation of drug disposition during drug discovery.