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Clinical Cancer Research : An Official... Feb 2011P-glycoprotein (Pgp) antagonists have been difficult to develop because of complex pharmacokinetic interactions and a failure to show meaningful results. Here we report... (Clinical Trial)
Clinical Trial
PURPOSE
P-glycoprotein (Pgp) antagonists have been difficult to develop because of complex pharmacokinetic interactions and a failure to show meaningful results. Here we report the results of a pharmacokinetic and pharmacodynamic trial using a third-generation, potent, noncompetitive inhibitor of Pgp, tariquidar (XR9576), in combination with docetaxel.
EXPERIMENTAL DESIGN
In the first treatment cycle, the pharmacokinetics of docetaxel (40 mg/m(2)) were evaluated after day 1 and day 8 doses, which were administered with or without tariquidar (150 mg). (99m)Tc-sestamibi scanning and CD56(+) mononuclear cell rhodamine efflux assays were conducted to assess Pgp inhibition. In subsequent cycles, 75 mg/m(2) docetaxel was administered with 150 mg tariquidar every 3 weeks.
RESULTS
Forty-eight patients were enrolled onto the trial. Nonhematologic grade 3/4 toxicities in 235 cycles were minimal. Tariquidar inhibited Pgp-mediated rhodamine efflux from CD56(+) cells and reduced (99m)Tc-sestamibi clearance from the liver. There was striking variability in basal sestamibi uptake; a 12% to 24% increase in visible lesions was noted in 8 of 10 patients with lung cancer. No significant difference in docetaxel disposition was observed in pairwise comparison with and without tariquidar. Four partial responses (PR) were seen (4/48); 3 in the non-small cell lung cancer (NSCLC) cohort, measuring 40%, 57%, and 67% by RECIST, and 1 PR in a patient with ovarian cancer.
CONCLUSIONS
Tariquidar is well tolerated, with less observed systemic pharmacokinetic interaction than previous Pgp antagonists. Variable effects of tariquidar on retention of sestamibi in imageable lung cancers suggest that follow-up studies assessing tumor drug uptake in this patient population would be worthwhile.
Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Adolescent; Adult; Aged; Aged, 80 and over; Antineoplastic Combined Chemotherapy Protocols; Docetaxel; Female; Humans; Lung Neoplasms; Middle Aged; Ovarian Neoplasms; Quinolines; Taxoids; Uterine Cervical Neoplasms
PubMed: 21081657
DOI: 10.1158/1078-0432.CCR-10-1725 -
Journal of Cancer Research and Clinical... Apr 2020Increased ATP-binding-cassette (ABC) transporter activity is a major cause of chemotherapy resistance in cancer. The ABC transporter family member ABCB1 is often...
PURPOSE
Increased ATP-binding-cassette (ABC) transporter activity is a major cause of chemotherapy resistance in cancer. The ABC transporter family member ABCB1 is often overexpressed in colorectal cancer (CRC). Phosphatidylinositol-4,5-bisphosphat (PI(4,5)P)-dependent pathways are involved in the regulation of ABCB1 function. The protein Myristoylated Alanine-Rich C-Kinase Substrate (MARCKS) is a pivotal regulator of PI(4,5)P and inactivated in many CRC cancers via genetic deletion or hyperphosphorylation. Therefore, MARCKS may critically impact ABCB1.
METHODS
CRC samples as well as CRC cell lines were tested for a connection between MARCKS and ABCB1 via immunofluorescence and Western-blot analysis. ABCB1 function was studied via calcein influx assay under treatment with known ABCB1 inhibitors (verapamil, tariquidar) as well as the kinase inhibitor bosutinib. ABCB1 internalization and MARCKS translocation was analyzed via confocal microscopy exploiting the endocytosis inhibitors chlorpromazine and dynasore. Abundance of PI(4,5)P was monitored by intramolecular fluorescence resonance energy transfer (FRET). Reproductive cell survival was studied via colorimetric WST-1 and clonogenic assays in combination with exposure to the chemotherapeutics doxorubicin and 5-fuorouracil (5-FU).
RESULTS
We found increased ABCB1 expression in MARCKS negative CRC patient tumor samples and established CRC cell lines. Mechanistically, the reconstitution of MARCKS function via recombinant expression or the pharmacological inhibition of MARCKS phosphorylation led to a substantial decrease in ABCB1 activity. In CRC cells, bosutinib treatment resulted in a MARCKS translocation from the cytosol to the plasma membrane, while simultaneously, ABCB1 was relocated to intracellular compartments. Inhibition of MARCKS phosphorylation via bosutinib rendered cells more sensitive to the chemotherapeutics doxorubicin and 5-FU.
CONCLUSIONS
Cells devoid of MARCKS function showed incomplete ABCB1 internalization, leading to higher ABCB1 activity enhancing chemoresistance. Vice versa our data suggest the prevention of MARCKS inhibition by reversing hyperphosphorylation or genomic restoration after deletion as two promising approaches to overcome tumor cell resistance towards chemotherapeutic ABCB1 substrates.
Topics: ATP Binding Cassette Transporter, Subfamily B; Aniline Compounds; Cell Line, Tumor; Colorectal Neoplasms; Drug Resistance, Neoplasm; Fluoresceins; Fluorescence Resonance Energy Transfer; HT29 Cells; Humans; Microscopy, Confocal; Myristoylated Alanine-Rich C Kinase Substrate; Nitriles; Phosphorylation; Quinolines
PubMed: 32056006
DOI: 10.1007/s00432-020-03149-2 -
Thoracic Cancer Aug 2022Small cell lung cancer (SCLC) is a highly aggressive disease with a poor prognosis. Although most patients initially respond to topoisomerase inhibitors, resistance...
BACKGROUND
Small cell lung cancer (SCLC) is a highly aggressive disease with a poor prognosis. Although most patients initially respond to topoisomerase inhibitors, resistance rapidly emerges. The aim, therefore, is to overcome resistance to topoisomerase I (irinotecan) or II (etoposide) inhibitors in SCLCs.
METHODS
To identify key factors in the chemoresistance of SCLCs, we established four cell lines resistant to etoposide or an active metabolite of irinotecan, SN-38, from SCLC cell lines and evaluated RNA profiles using parental and newly established cell lines.
RESULTS
We found that the drug efflux protein, ATP-binding cassette sub-family B member 1 (ABCB1), was associated with resistance to etoposide, and ATP-binding cassette sub-family G member 2 (ABCG2) was associated with resistance to SN-38 by RNA sequencing. The inhibition of ABCB1 or ABCG2 in each resistant cell line induced synergistic apoptotic activity and promoted drug sensitivity in resistant SCLC cells. The ABC transporter inhibitors, elacridar and tariquidar, restored sensitivity to etoposide or SN-38 in in vitro and in vivo studies, and promoted apoptotic activity and G2-M arrest in resistant SCLC cells.
CONCLUSIONS
ABC transporter inhibitors may be a promising therapeutic strategy for the purpose of overcoming resistance to topoisomerase inhibitors in patients with SCLC.
Topics: ATP Binding Cassette Transporter, Subfamily B; ATP Binding Cassette Transporter, Subfamily G, Member 2; Antineoplastic Agents; Apoptosis; Cell Line, Tumor; Drug Resistance, Neoplasm; Etoposide; G2 Phase Cell Cycle Checkpoints; Humans; Irinotecan; Lung Neoplasms; Neoplasm Proteins; Small Cell Lung Carcinoma; Topoisomerase Inhibitors
PubMed: 35719112
DOI: 10.1111/1759-7714.14527 -
Molecular Imaging and Biology Apr 2019The melanin-concentrating hormone receptor 1 (MCHR1) has become an important pharmacological target, since it may be involved in various diseases, such as diabetes,... (Comparative Study)
Comparative Study
PURPOSE
The melanin-concentrating hormone receptor 1 (MCHR1) has become an important pharmacological target, since it may be involved in various diseases, such as diabetes, insulin resistance, and obesity. Hence, a suitable positron emission tomography radiotracer for the in vivo assessment of the MCHR1 pharmacology is imperative. The current paper contrasts the extensive in vitro, in vivo, and ex vivo assessments of the radiotracers [F]FE@SNAP and [C]SNAP-7941 and provides comprehensive information about their biological and physicochemical properties. Furthermore, it examines their suitability for first-in-man imaging studies.
PROCEDURES
Kinetic real-time cell-binding studies with [F]FE@SNAP and [C]SNAP-7941 were conducted on adherent Chines hamster ovary (CHO-K1) cells stably expressing the human MCHR1 and MCHR2. Small animal imaging studies on mice and rats were performed under displacement and baseline conditions, as well as after pretreatment with the P-glycoprotein/breast cancer resistant protein inhibitor tariquidar. After the imaging studies, detailed analyses of the ex vivo biodistribution were performed. Ex vivo metabolism was determined in rat blood and brain and analyzed at various time points using a quantitative radio-HPLC assay.
RESULTS
[C]SNAP-7941 demonstrates high uptake on CHO-K1-hMCHR1 cells, whereas no uptake was detected for the CHO-K1-hMCHR2 cells. In contrast, [F]FE@SNAP evinced binding to CHO-K1-hMCHR1 and CHO-K1-hMCHR2 cells. Imaging studies with [F]FE@SNAP and [C]SNAP-7941 showed an increased brain uptake after tariquidar pretreatment in mice, as well as in rats, and exhibited a significant difference between the time-activity curves of the baseline and blocking groups. Biodistribution of both tracers demonstrated a decreased uptake after displacement. [C]SNAP-7941 revealed a high metabolic stability in rats, whereas [F]FE@SNAP was rapidly metabolized.
CONCLUSIONS
Both radiotracers demonstrate appropriate imaging properties for the MCHR1. However, the pronounced metabolic stability as well as superior selectivity and affinity of [C]SNAP-7941 underlines the decisive superiority over [F]FE@SNAP.
Topics: Animals; Blood Proteins; CHO Cells; Carbon Radioisotopes; Chromatography, Affinity; Cricetinae; Cricetulus; Fluorine Radioisotopes; Humans; Kinetics; Metabolome; Mice; Piperidines; Positron-Emission Tomography; Protein Binding; Pyrimidines; Rats; Receptors, Somatostatin; Tissue Distribution
PubMed: 29948643
DOI: 10.1007/s11307-018-1212-0 -
International Journal of Molecular... Nov 2020ABCB1 (P-glycoprotein) and ABCG2 (breast cancer resistance protein) are co-localized at the blood-brain barrier (BBB), where they restrict the brain distribution of many...
BACKGROUND
ABCB1 (P-glycoprotein) and ABCG2 (breast cancer resistance protein) are co-localized at the blood-brain barrier (BBB), where they restrict the brain distribution of many different drugs. Moreover, ABCB1 and possibly ABCG2 play a role in Alzheimer's disease (AD) by mediating the brain clearance of beta-amyloid (Aβ) across the BBB. This study aimed to compare the abundance and activity of ABCG2 in a commonly used β-amyloidosis mouse model (APP/PS1-21) with age-matched wild-type mice.
METHODS
The abundance of ABCG2 was assessed by semi-quantitative immunohistochemical analysis of brain slices of APP/PS1-21 and wild-type mice aged 6 months. Moreover, the brain distribution of two dual ABCB1/ABCG2 substrate radiotracers ([C]tariquidar and [C]erlotinib) was assessed in APP/PS1-21 and wild-type mice with positron emission tomography (PET). [C]Tariquidar PET scans were performed without and with partial inhibition of ABCG2 with Ko143, while [C]erlotinib PET scans were only performed under baseline conditions.
RESULTS
Immunohistochemical analysis revealed a significant reduction (by 29-37%) in the number of ABCG2-stained microvessels in the brains of APP/PS1-21 mice. Partial ABCG2 inhibition significantly increased the brain distribution of [C]tariquidar in APP/PS1-21 and wild-type mice, but the brain distribution of [C]tariquidar did not differ under both conditions between the two mouse strains. Similar results were obtained with [C]erlotinib.
CONCLUSIONS
Despite a reduction in the abundance of cerebral ABCG2 and ABCB1 in APP/PS1-21 mice, the brain distribution of two dual ABCB1/ABCG2 substrates was unaltered. Our results suggest that the brain distribution of clinically used ABCB1/ABCG2 substrate drugs may not differ between AD patients and healthy people.
Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; ATP Binding Cassette Transporter, Subfamily G, Member 2; Amyloid beta-Peptides; Amyloidosis; Animals; Blood-Brain Barrier; Brain; Disease Models, Animal; Female; Mice; Mice, Inbred C57BL; Mice, Transgenic; Positron-Emission Tomography; Quinolines; Tissue Distribution
PubMed: 33153231
DOI: 10.3390/ijms21218245 -
Clinical Cancer Research : An Official... May 2009P-glycoprotein (Pgp) antagonists have had unpredictable pharmacokinetic interactions requiring reductions of chemotherapy. We report a phase I study using tariquidar...
PURPOSE
P-glycoprotein (Pgp) antagonists have had unpredictable pharmacokinetic interactions requiring reductions of chemotherapy. We report a phase I study using tariquidar (XR9576), a potent Pgp antagonist, in combination with vinorelbine.
EXPERIMENTAL DESIGN
Patients first received tariquidar alone to assess effects on the accumulation of (99m)Tc-sestamibi in tumor and normal organs and rhodamine efflux from CD56+ mononuclear cells. In the first cycle, vinorelbine pharmacokinetics was monitored after the day 1 and 8 doses without or with tariquidar. In subsequent cycles, vinorelbine was administered with tariquidar. Tariquidar pharmacokinetics was studied alone and with vinorelbine.
RESULTS
Twenty-six patients were enrolled. Vinorelbine 20 mg/m(2) on day 1 and 8 was identified as the maximum tolerated dose (neutropenia). Nonhematologic grade 3/4 toxicities in 77 cycles included the following: abdominal pain (4 cycles), anorexia (2), constipation (2), fatigue (3), myalgia (2), pain (4) and dehydration, depression, diarrhea, ileus, nausea, and vomiting, (all once). A 150-mg dose of tariquidar: (1) reduced liver (99m)Tc-sestamibi clearance consistent with inhibition of liver Pgp; (2) increased (99m)Tc-sestamibi retention in a majority of tumor masses visible by (99m)Tc-sestamibi; and (3) blocked Pgp-mediated rhodamine efflux from CD56+ cells over the 48 hours examined. Tariquidar had no effects on vinorelbine pharmacokinetics. Vinorelbine had no effect on tariquidar pharmacokinetics. One patient with breast cancer had a minor response, and one with renal carcinoma had a partial remission.
CONCLUSIONS
Tariquidar is a potent Pgp antagonist, without significant side effects and much less pharmacokinetic interaction than previous Pgp antagonists. Tariquidar offers the potential to increase drug exposure in drug-resistant cancers.
Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Adolescent; Adult; Aged; Aged, 80 and over; Antineoplastic Agents, Phytogenic; Area Under Curve; Dose-Response Relationship, Drug; Drug Interactions; Humans; Metabolic Clearance Rate; Middle Aged; Neoplasms; Neutropenia; Quinolines; Vinblastine; Vinorelbine; Young Adult
PubMed: 19417029
DOI: 10.1158/1078-0432.CCR-08-0938 -
PloS One 2013Multidrug resistance protein 7 (MRP7, ABCC10) is a recently discovered member of the ATP-binding cassette (ABC) family which are capable of conferring resistance to a...
Multidrug resistance protein 7 (MRP7, ABCC10) is a recently discovered member of the ATP-binding cassette (ABC) family which are capable of conferring resistance to a variety of anticancer drugs, including taxanes and nucleoside analogs, in vivo. MRP7 is highly expressed in non-small cell lung cancer cells, and Mrp7-KO mice are highly sensitive to paclitaxel, making MRP7 an attractive chemotherapeutic target of non-small cell lung cancer. However, only a few inhibitors of MRP7 are currently identified, with none of them having progressed to clinical trials. We used MRP7-expressing cells to investigate whether tariquidar, a third generation inhibitor of P-glycoprotein, could inhibit MRP7-mediated multidrug resistance (MDR). We found that tariquidar, at 0.1 and 0.3 µM, significantly potentiated the sensitivity of MRP7-transfected HEK293 cells to MRP7 substrates and increased the intracellular accumulation of paclitaxel. We further demonstrated that tariquidar directly impaired paclitaxel efflux and could downregulate MRP7 protein expression in a concentration- and time-dependent manner after prolonged treatment. Our findings suggest that tariquidar, at pharmacologically achievable concentrations, reverses MRP7-mediated MDR through inhibition of MRP7 protein expression and function, and thus represents a promising therapeutic agent in the clinical treatment of chemoresistant cancer patients.
Topics: Cell Line; Drug Resistance, Multiple; Humans; Multidrug Resistance-Associated Proteins; Quinolines
PubMed: 23393594
DOI: 10.1371/journal.pone.0055576 -
Biological & Pharmaceutical Bulletin 2022Microfluidic devices are attracting attention for their ability to provide a biomimetic microenvironment wherein cells are arranged in a particular pattern and provided...
Microfluidic devices are attracting attention for their ability to provide a biomimetic microenvironment wherein cells are arranged in a particular pattern and provided fluidic and mechanical forces. In this study, we evaluated drug transport across Caco-2 cell layers in microfluidic devices and investigated the effects of fluid flow on drug transport and metabolism. We designed a microfluidic device that comprises two blocks of polydimethylsiloxane and a sandwiched polyethylene terephthalate membrane with pores 3.0 µm in diameter. When cultured in a dynamic fluid environment, Caco-2 cells were multilayered and developed microvilli on the surface as compared with a static environment. Drugs with higher lipophilicity exhibited higher permeability across the Caco-2 layers, as well as in the conventional method using Transwells, and the fluidic conditions had little effect on permeability. In the Caco-2 cell layers cultured in Transwells and microfluidic devices, the basal-to-apical transport of rhodamine 123, a substrate of P-glycoprotein, was greater than the apical-to-basal transport, and the presence of tariquidar, an inhibitor of P-glycoprotein, completely diminished asymmetric transport. Furthermore, fluidic conditions promoted the metabolism of temocapril by carboxylesterases. On the other hand, we showed that fluidic conditions have little effect on gene expression of several transporters and metabolic enzymes. These results provide useful information regarding the application of microfluidic devices in drug transport and metabolism studies.
Topics: ATP Binding Cassette Transporter, Subfamily B; Caco-2 Cells; Humans; Intestinal Absorption; Intestines; Lab-On-A-Chip Devices; Permeability
PubMed: 36047192
DOI: 10.1248/bpb.b22-00092 -
Proceedings of the National Academy of... Jan 2023ABCG2 is an ATP-binding cassette (ABC) transporter that extrudes a wide range of xenobiotics and drugs from the cell and contributes to multidrug resistance in cancer...
ABCG2 is an ATP-binding cassette (ABC) transporter that extrudes a wide range of xenobiotics and drugs from the cell and contributes to multidrug resistance in cancer cells. Following our recent structural characterization of topotecan-bound ABCG2, here, we present cryo-EM structures of ABCG2 under turnover conditions in complex with a special modulator and slow substrate, tariquidar, in nanodiscs. The structures reveal that similar to topotecan, tariquidar induces two distinct ABCG2 conformations under turnover conditions (turnover-1 and turnover-2). μs-scale molecular dynamics simulations of drug-bound and apo ABCG2 in native-like lipid bilayers, in both topotecan- and tariquidar-bound states, characterize the ligand size as a major determinant of its binding stability. The simulations highlight direct lipid-drug interactions for the smaller topotecan, which exhibits a highly dynamic binding mode. In contrast, the larger tariquidar occupies most of the available volume in the binding pocket, thus leaving little space for lipids to enter the cavity and interact with it. Similarly, when simulating ABCG2 in the apo inward-open state, we also observe spontaneous penetration of phospholipids into the binding cavity. The captured phospholipid diffusion pathway into ABCG2 offers a putative general path to recruit any hydrophobic/amphiphilic substrates directly from the membrane. Our simulations also reveal that ABCG2 rejects cholesterol as a substrate, which is omnipresent in plasma membranes that contain ABCG2. At the same time, cholesterol is found to prohibit the penetration of phospholipids into ABCG2. These molecular findings have direct functional ramifications on ABCG2's function as a transporter.
Topics: Ligands; Topotecan; Drug Resistance, Multiple; ATP-Binding Cassette Transporters; Phospholipids; Cholesterol; Drug Resistance, Neoplasm
PubMed: 36580587
DOI: 10.1073/pnas.2213437120 -
Molecular Pharmaceutics Sep 2015The adenosine triphosphate-binding cassette transporter P-glycoprotein (ABCB1/Abcb1a) restricts at the blood-brain barrier (BBB) brain distribution of many drugs. ABCB1...
The adenosine triphosphate-binding cassette transporter P-glycoprotein (ABCB1/Abcb1a) restricts at the blood-brain barrier (BBB) brain distribution of many drugs. ABCB1 may be involved in drug-drug interactions (DDIs) at the BBB, which may lead to changes in brain distribution and central nervous system side effects of drugs. Positron emission tomography (PET) with the ABCB1 substrates (R)-[(11)C]verapamil and [(11)C]-N-desmethyl-loperamide and the ABCB1 inhibitor tariquidar has allowed direct comparison of ABCB1-mediated DDIs at the rodent and human BBB. In this work we evaluated different factors which could influence the magnitude of the interaction between tariquidar and (R)-[(11)C]verapamil or [(11)C]-N-desmethyl-loperamide at the BBB and thereby contribute to previously observed species differences between rodents and humans. We performed in vitro transport experiments with [(3)H]verapamil and [(3)H]-N-desmethyl-loperamide in ABCB1 and Abcb1a overexpressing cell lines. Moreover we conducted in vivo PET experiments and biodistribution studies with (R)-[(11)C]verapamil and [(11)C]-N-desmethyl-loperamide in wild-type mice without and with tariquidar pretreatment and in homozygous Abcb1a/1b((-/-)) and heterozygous Abcb1a/1b((+/-)) mice. We found no differences for in vitro transport of [(3)H]verapamil and [(3)H]-N-desmethyl-loperamide by ABCB1 and Abcb1a and its inhibition by tariquidar. [(3)H]-N-Desmethyl-loperamide was transported with a 5 to 9 times higher transport ratio than [(3)H]verapamil in ABCB1- and Abcb1a-transfected cells. In vivo, brain radioactivity concentrations were lower for [(11)C]-N-desmethyl-loperamide than for (R)-[(11)C]verapamil. Both radiotracers showed tariquidar dose dependent increases in brain distribution with tariquidar half-maximum inhibitory concentrations (IC50) of 1052 nM (95% confidence interval CI: 930-1189) for (R)-[(11)C]verapamil and 1329 nM (95% CI: 980-1801) for [(11)C]-N-desmethyl-loperamide. In homozygous Abcb1a/1b((-/-)) mice brain radioactivity distribution was increased by 3.9- and 2.8-fold and in heterozygous Abcb1a/1b((+/-)) mice by 1.5- and 1.1-fold, for (R)-[(11)C]verapamil and [(11)C]-N-desmethyl-loperamide, respectively, as compared with wild-type mice. For both radiotracers radiolabeled metabolites were detected in plasma and brain. When brain and plasma radioactivity concentrations were corrected for radiolabeled metabolites, brain distribution of (R)-[(11)C]verapamil and [(11)C]-N-desmethyl-loperamide was increased in tariquidar (15 mg/kg) treated animals by 14.1- and 18.3-fold, respectively, as compared with vehicle group. Isoflurane anesthesia altered [(11)C]-N-desmethyl-loperamide but not (R)-[(11)C]verapamil metabolism, and this had a direct effect on the magnitude of the increase in brain distribution following ABCB1 inhibition. Our data furthermore suggest that in the absence of ABCB1 function brain distribution of [(11)C]-N-desmethyl-loperamide but not (R)-[(11)C]verapamil may depend on cerebral blood flow. In conclusion, we have identified a number of important factors, i.e., substrate affinity to ABCB1, brain uptake of radiolabeled metabolites, anesthesia, and cerebral blood flow, which can directly influence the magnitude of ABCB1-mediated DDIs at the BBB and should therefore be taken into consideration when interpreting PET results.
Topics: ATP Binding Cassette Transporter, Subfamily B; ATP-Binding Cassette Transporters; Animals; Biological Transport; Blood-Brain Barrier; Brain; Calcium Channel Blockers; Carbon Radioisotopes; Drug Interactions; Female; Humans; Loperamide; Mice; Mice, Inbred C57BL; Mice, Knockout; Positron-Emission Tomography; Radiopharmaceuticals; Verapamil
PubMed: 26202880
DOI: 10.1021/acs.molpharmaceut.5b00168