BMC Research Notes

BMC Res Notes. 7(1): 710

Association between acquired resistance to PLX4032 (vemurafenib) and ATP-binding cassette transporter expression

Martin Michaelis

M.Michaelis@kent.ac.uk

, Florian Rothweiler

f.rothweiler@kinderkrebsstiftung-frankfurt.de

, Thomas Nerreter

nerrie2001@yahoo.de

, Marijke van Rikxoort

MvanRikxoort@uni-bonn.de

, Richard Zehner

zehner@em.uni-frankfurt.de

, Wilhelm G Dirks

wdi@dsmz.de

, Michael Wiese

mwiese@uni-bonn.de

, Jindrich Cinatl Jr

Cinatl@em.uni-frankfurt.de

Institut für Medizinische Virologie, Klinikum der Goethe-Universität, Paul Ehrlich-Str. 40, Frankfurt am Main, 60596 Germany

Centre for Molecular Processing and School of Biosciences, University of Kent, Canterbury Kent, CT2 7NJ UK

Institut für Rechtsmedizin, Klinikum der Goethe-Universität, Kennedyallee 104, Frankfurt am Main, 60596 Germany

Leibniz-Institute Deutsche Sammlung für Mikroorganismen und Zellkulturen GmbH, Inhoffenstraße 7B, Braunschweig, 38124 Germany

Pharmaceutical Institute, University of Bonn, An der Immenburg 4, Bonn, 53121 Germany

Centre for Molecular Processing and School of Biosciences, University of Kent, Canterbury Kent, CT2 7NJ UK

Institute of Pharmacology and Toxicology, Biomedical Center (BMZ), University of Bonn, Bonn, 53127 Germany

© Michaelis et al.; licensee BioMed Central Ltd. 2014

DOI: 10.1186/1756-0500-7-710

Published online: 10 October 2014

Abstract

Background

Various kinase inhibitors are known to be ATP-binding cassette (ABC) transporter substrates and resistance acquisition to kinase inhibitors has been associated to increased ABC transporter expression. Here, we investigated the role of the ABC transporters ABCB1, ABCC1, and ABCG2 during melanoma cell resistance acquisition to the V600-mutant BRAF inhibitors PLX4032 (vemurafenib) and PLX4720. PLX4032 had previously been shown to interfere with ABCB1 and ABCG2. PLX4720 had been demonstrated to interact with ABCB1 but to a lower extent than PLX4032.

Findings

PLX4032 and PLX4720 affected ABCC1- and ABCG2-mediated drug transport in a similar fashion. In a panel of 16 V600E BRAF-mutated melanoma cell lines consisting of four parental cell lines and their sub-lines with acquired resistance to PLX4032, PLX4720, vincristine (cytotoxic ABCB1 and ABCC1 substrate), or mitoxantrone (cytotoxic ABCG2 substrate), we detected enhanced ABC transporter expression in 4/4 cytotoxic ABC transporter substrate-resistant, 3/4 PLX4720-resistant, and 1/4 PLX4032-resistant melanoma cell lines.

Conclusion

PLX4032 has the potential to induce ABC transporter expression but this potential is lower than that of PLX4720 or cytotoxic ABC transporter substrates. Since ABC transporters confer multi-drug resistance, this is of relevance for the design of next-line therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/1756-0500-7-710) contains supplementary material, which is available to authorized users.

Findings

The oncogenic V600-mutant BRAF inhibitor PLX4032 (vemurafenib) caused improved response and survival rates in V600-mutant BRAF melanoma patients but PLX4032 resistance formation remains inevitable. Resistance mechanisms involve activation of alternative kinases and non-related compensatory pathways [1, 2]. Although protein kinase inhibitors are rather specific drugs (particularly in comparison to the cytotoxic anti-cancer chemotherapeutics) they are also known to exert off-target effects [3–5]. For example, different protein kinase inhibitors interfere with drug transport mediated by various ATP binding cassette (ABC) transporters including ABCB1 (also known as MDR1 or P-glycoprotein), ABCC1 (also known as MRP1), and ABCG2 (also known as BCRP) [3, 4, 6–9].

ABC transporters play important roles in the passage of drugs, xenobiotics, and food constituents through cellular and tissue barriers and consequently in their absorption, distribution, and excretion. Moreover, different ABC transporters are frequently found highly expressed on cancer cells playing an important role in cancer cell chemoresistance [10–12]. Resistance acquisition to kinase inhibitors may be associated with enhanced ABC transporter expression on cancer cells [13–15].

Some information is already available on the effects of PLX4032 and the closely related V600-mutant BRAF inhibitor PLX4720 [16] on ABC transporter function. PLX4032 and PLX4720 both interfere with ABCB1-mediated drug transport [17–19]. PLX4032 was also shown to interact with ABCG2 (also known as BCRP) [17, 18]. ABCG2 expression was suggested to be an acquired resistance mechanism to PLX4032 [20] although data on ABCG2 expression in cells with acquired PLX4032 resistance are missing.

Recently, we had shown that PLX4032 and PLX4720 differed in their effects on ABCB1-mediated drug transport. Despite the structural similarity of these compounds PLX4032 interfered stronger with ABCB1 function than PLX4720 [19]. Here, we 1) compared the effects of PLX4032 and PLX4720 on ABCG2 and ABCC1 and 2) investigated whether resistance acquisition to these compounds may be associated with enhanced ABC transporter expression.

Effects of PLX4032 and PLX4720 on ABCG2 and ABCC1 function

To study the effects of PLX4032 and PLX4720 on ABCG2, an ABCG2-expressing sub-line of the BRAF wild-type neuroblastoma cell line UKF-NB-3 (UKF-NB-3ABCG2) was used that had been established by lentiviral transduction with LeGO vectors (http://www.lentigo-vectors.de) as described previously [21, 22]. All experimental procedures were performed as described previously [22]. PLX4032 and PLX4720 treatment of UKF-NB-3ABCG2 cells (but not of UKF-NB-3 cells or UKF-NB-3 cells transduced with a control vector) resulted in a similar dose-dependent increase in the cellular accumulation of the fluorescent ABCG2 substrate BODIPY-prazosine (Figure 1A) without affecting ABCG2 expression (Additional file 1: Figure S1).

Figure 1View larger versionFigure 1. Effect of PLX4032 and PLX4720 on ABCG2 activity. A) Influence of PLX4032 or PLX4720 on BODIPY-prazosine (1 μM) fluorescence in UKF-NB-3ABCG2 cells, B) time kinetics of BODIPY-prazosine (1 μM) fluorescence in UKF-NB-3ABCG2 cells in the presence of PLX4032 or PLX4720 after a 60 min pre-incubation period with subsequent wash-out of extracellular BODIPY-prazosine and PLX4032 or PLX4720 (control = BODIPY-prazosine incubation in the absence of drugs). C) ABCG2 ATPase activity in isolated membranes in the presence of PLX4032 or PLX4720 (control = activity in the absence of drugs). Sulfasalazine, a known ABCG2 substrate, was used for comparison. *P < 0.05 relative to non-treated controls.

In wash-out experiments, cellular BODIPY-prazosine fluorescence levels declined rapidly in UKF-NB-3ABCG2 cells (Figure 1B), likely because the removal of extracellular PLX4032 and PLX4720 resulted in the rapid ABCG2-mediated efflux of PLX4032/PLX4720 and BODIPY-prazosine. PLX4032 and PLX4720 increased ABCG2 ATPase activity in an isolated membrane assay (Figure 1C) indicating binding and activation of ABCG2 by these compounds. Further, PLX4032 and PLX4720 concentration-dependently enhanced the toxicity of the ABCG2 substrate mitoxantrone in UKF-NB-3ABCG2 cells but not of non-transduced UKF-NB-3 cells or UKF-NB-3 cells transduced with a control vector (Additional file 2: Table S1) as indicated by MTT assay after five day incubation. These findings are in accordance with previous studies demonstrating PLX4032 to be an ABCG2 substrate [17, 18, 20].

The effects of PLX4032 and PLX4720 on ABCC1 were investigated in the ABCC1-expressing cell lines G62 (glioblastoma) and PC3rVCR²⁰ (prostate cancer) [22]. PLX4032 and PLX4720 similarly increased the accumulation of the fluorescent ABCC1 substrate 5-CFDA in G62 cells in a concentration-dependent manner (Figure 2A) without affecting ABCC1 expression (Additional file 1: Figure S1). 5-CFDA fluorescence declined rapidly after wash-out of PLX4032 or PLX4720 (Figure 2B). Both substances increased ABCC1 ATPase activity in an isolated membrane assay (Figure 2C) and the toxicity of the ABCC1 substrate vincristine in G62 and PC3rVCR²⁰ cells (Additional file 3: Table S2) in a concentration-dependent manner. These findings appear to contrast other findings that suggested PLX4032 not to be an ABCC1 substrate [20]. The differences may be explained by the use of different ABCC1 substrates and different cellular models. Depending on the exact mode or strength of interaction of ABC transporter modulators with an ABC transporter, different substrates may not always compete for the same binding site. For example, activators of ABCB1 activity that enhance the efflux of certain ABCB1 substrates were described [23]. Moreover, certain ABCB1 modulators were shown to exert differing effects on the cellular accumulation of distinct ABCB1 substrates [24].

Figure 2View larger versionFigure 2. Effect of PLX4032 and PLX4720 on ABCC1 activity. A) Influence of PLX4032 or PLX4720 on 5-CFDA (1 μM) fluorescence in G62 cells, B) time kinetics of 5-CFDA (1 μM) fluorescence in G62 cells in the presence of PLX4032 or PLX4720 after a 60 min pre-incubation period with subsequent wash-out of extracellular 5-CFDA and PLX4032 or PLX4720 (control = 5-CFDA incubation in the absence of drugs). C) ABCC1 ATPase activity in isolated membranes in the presence of PLX4032 or PLX4720 (control = activity in the absence of drugs). NEM-GS, a known ABCC1 substrate, was used for comparison. *P < 0.05 relative to non-treated controls.

PLX4032 and PLX4720 also sensitised two wild-type BRAF melanoma cell lines, IPC-298 and SK-Mel-30 (DSMZ, Braunschweig, Germany), that express ABCB1, ABCC1, and ABCG2 (Additional file 4: Table S3) to vincristine and mitoxantrone (Additional file 5: Table S4). Taken together, these results show that PLX4032 and PLX4720 interfere with ABCC1 and ABCG2 in a similar fashion.

ABC transporter expression in V600E BRAF-mutated melanoma cell lines with acquired resistance to PLX4032 and PLX4720

Next, we investigated the expression of ABCB1, ABCC1, and ABCG2 in the V600E BRAF-mutated melanoma cell lines Colo-679, IGR-39, MelHO, and RVH-421 (DSMZ, Braunschweig, Germany) and their sub-lines with acquired resistance to PLX4032 (Colo-679rPLX403210 μM, MelHOrPLX403210 μM, IGR-39rPLX403220 μM, RVH-421rPLX403210 μM), PLX4720 (Colo-679rPLX472010 μM, MelHOrPLX472010 μM, IGR-39rPLX472020 μM, RVH-421rPLX472010 μM), vincristine (Colo-679rVCR²⁰, IGR-39rVCR¹⁰, MelHOrVCR²⁰), or mitoxantrone (RVH-421rMitox¹⁰) (Figure 3; Additional file 6: Table S5) that were derived from the Resistant Cancer Cell Line (RCCL) collection (http://www.kent.ac.uk/stms/cmp/RCCL/RCCLabout.html). Treatment of melanoma cells with PLX4032 or cytotoxic anti-cancer drugs had been shown to result in the selection of ABCB5-expressing cells [25]. However, we did not detect enhanced ABCB5 expression in our resistance models relative to the parental sensitive cells.

Figure 3View larger versionFigure 3. Expression of ABCB1, ABCC1, and ABCG2 in V600 BRAF-mutated melanoma cells adapted to PLX4032, PLX4720, or the cytotoxic ABC transporter substrates vincristine (VCR) or mitoxantrone (MITOX) relative to the respective parental cell lines. White and black bars are used to facilitate the identification of resistant sub-lines that are derived from the same parental cell line. *P < 0.05 relative to parental cells.

Colo-679rVCR¹⁰, MelHOrVCR²⁰, IGR-39rPLX472020 μM, and RVH-421rPLX472010 μM expressed increased ABCB1 levels, IGR-39rVCR¹⁰, IGR-39rPLX403220 μM, and IGR-39rPLX472020 μM high ABCC1 levels, IGR-39rVCR¹⁰, MelHOrPLX472010 μM, RVH-421rMITOX¹⁰, and RVH-421rPLX472010 μM high ABCG2 levels (Figure 3). The ABC transporters conferred resistance to the cytotoxic ABC transporter substrates vincristine (ABCB1, ABCC1) and mitoxantrone (ABCG2) but not to PLX4032 or PLX4720 (Additional file 7: Table S6). These data show that V600-mutant melanoma cells with acquired resistance to PLX4032 may express enhanced ABC transporter levels. However, the potential of PLX4032 to induce ABC transporter expression appears to be lower compared to PLX4720, although both molecules differ in just one phenyl group (Additional file 8: Figure S2), and cytotoxic ABC transporter substrates.

Discussion

The finding that resistance acquisition to PLX4032 and PLX4720 may be associated with enhanced ABCB1 expression is in line with data showing resistance acquisition to other kinase inhibitors to be associated with ABCB1, ABCC1, and ABCG2 expression [13–15, 26].

PLX4032 had previously been shown to interfere substantially stronger with ABCB1 than PLX4720 [19] while we show here that both compounds display similar effects on ABCG2 and ABCC1. Therefore, differing levels of interaction with the investigated ABC transporters do not explain the enhanced ABC transporter expression in PLX4720-resistant relative to PLX4032-resistant cells. ABC transporter up-regulation may be part of the cellular stress response, and anti-cancer drug-induced stress may induce ABC transporter expression regardless of whether the drugs are ABC transporter substrates [27–29]. PLX4720 induced more pronounced toxic off-target effects (IC₅₀ 15.04 ± 0.60 μM in BRAF wild-type UKF-NB-3 cells) than PLX4032 (IC₅₀ 30.61 ± 1.37 μM in UKF-NB-3). Also, we detected enhanced ABCG2 expression in IGR-39rVCR¹⁰ cells although vincristine is not regarded to be an ABCG2 substrate.

In conclusion, we show that PLX4032 and PLX4720 interfere with ABCC1- and ABCG2-mediated drug transport. Since ABC transporters play important roles in the absorption, distribution, and excretion of drugs these findings are of potential clinical relevance when PLX4032 is co-administered with anti-cancer drugs or non-cancer-related drugs that are ABC transporter substrates [10–12]. The investigation of a panel of 16 BRAF V600-mutant melanoma cell lines suggested that resistance acquisition to PLX4032 may be associated with enhanced ABC transporter expression although PLX4720 and cytotoxic ABC transporter substrates are stronger inducers of ABC transporter expression than PLX4032. This is of relevance for the design of next-line therapies for melanomas with acquired PLX4032 resistance since ABC transporters including ABCB1, ABCC1, and ABCG2 confer multi-drug resistance [10–12]. The potential clinical implications of our findings are outlined in Additional file 9: Figure S3.

Availability of supporting data

The data sets supporting the results of this article are included within the article and its additional files.

Supplementary Material

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Footnotes

Competing interests

The authors declare that they have no competing interest.

Authors’ contributions

MM and JCjr designed the study, performed experiments, analysed data, and drafted the manuscript. FR and TN determined effects of PLX4032 and PLX4720 on ABC transporter function. MvR established and characterised drug-resistant melanoma cells. RZ and WGD authenticated and characterised the investigated cell lines. MW analysed ABC transporter data and provided WK-X-34. All authors read and approved the final manuscript.

Acknowledgements

The authors thank Kristoffer Riecken and Boris Fehse (Universitätsklinikum Hamburg-Eppendorf) for provision of and support with the LeGO vectors.

The work was supported by the Hilfe für krebskranke Kinder Frankfurt e.V. (JCjr, MM), the Frankfurter Stiftung für krebskranke Kinder (JCjr, MM), the Royal Society (MM), and the Kent Cancer trust (MM).

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References

Bollag G, Tsai J, Zhang J, Zhang C, Ibrahim P, Nolop K, Hirth P, authors. Vemurafenib: the first drug approved for BRAF-mutant cancer. Nat Rev Drug Discov. 2012;11:873–886. [Cross Ref] [PubMed]

Bucheit AD, Davies MA, authors. Emerging insights into resistance to BRAF inhibitors in melanoma. Biochem Pharmacol. 2014;87:381–389. [Cross Ref] [PubMed]

Hegedus C, Ozvegy-Laczka C, Szakács G, Sarkadi B, authors. Interaction of ABC multidrug transporters with anticancer protein kinase inhibitors: substrates and/or inhibitors? Curr Cancer Drug Targets. 2009;9:252–262. [Cross Ref] [PubMed]

Van Erp NP, Gelderblom H, Guchelaar HJ, authors. Clinical pharmacokinetics of tyrosine kinase inhibitors. Cancer Treat Rev. 2009;35:692–706. [Cross Ref] [PubMed]

Force T, Kolaja KL, authors. Cardiotoxicity of kinase inhibitors: the prediction and translation of preclinical models to clinical outcomes. Nat Rev Drug Discov. 2011;10:111–126. [Cross Ref] [PubMed]

Hegedus T, Orfi L, Seprodi A, Váradi A, Sarkadi B, Kéri G, authors. Interaction of tyrosine kinase inhibitors with the human multidrug transporter proteins, MDR1 and MRP1. Biochim Biophys Acta. 2002;1587:318–325. [Cross Ref] [PubMed]

Shi Z, Peng XX, Kim IW, Shukla S, Si QS, Robey RW, Bates SE, Shen T, Ashby CR Jr, Fu LW, Ambudkar SV, Chen ZS, authors. Erlotinib (Tarceva, OSI-774) antagonizes ATP-binding cassette subfamily B member 1 and ATP-binding cassette subfamily G member 2-mediated drug resistance. Cancer Res. 2007;67:11012–11020. [Cross Ref] [PubMed]

Hegedüs C, Ozvegy-Laczka C, Apáti A, Magócsi M, Német K, Orfi L, Kéri G, Katona M, Takáts Z, Váradi A, Szakács G, Sarkadi B, authors. Interaction of nilotinib, dasatinib and bosutinib with ABCB1 and ABCG2: implications for altered anti-cancer effects and pharmacological properties. Br J Pharmacol. 2009;158:1153–1164. [Cross Ref] [PubMed]

Hegedüs C, Truta-Feles K, Antalffy G, Várady G, Német K, Ozvegy-Laczka C, Kéri G, Orfi L, Szakács G, Settleman J, Váradi A, Sarkadi B, authors. Interaction of the EGFR inhibitors gefitinib, vandetanib, pelitinib and neratinib with the ABCG2 multidrug transporter: Implications for the emergence and reversal of cancer drug resistance. Biochem Pharmacol. 2012;84:260–267. [Cross Ref] [PubMed]

Silverton L, Dean M, Moitra K, authors. Variation and evolution of the ABC transporter genes ABCB1, ABCC1, ABCG2, ABCG5 and ABCG8: implication for pharmacogenetics and disease. Drug Metabol Drug Interact. 2011;26:169–179. [Cross Ref] [PubMed]

Tamaki A, Ierano C, Szakacs G, Robey RW, Bates SE, authors. The controversial role of ABC transporters in clinical oncology. Essays Biochem. 2011;50:209–232. [Cross Ref] [PubMed]

Ieiri I, author. Functional significance of genetic polymorphisms in P-glycoprotein (MDR1, ABCB1) and breast cancer resistance protein (BCRP, ABCG2). Drug Metab Pharmacokinet. 2012;27:85–105. [Cross Ref] [PubMed]

Burger H, Van Tol H, Brok M, Wiemer EA, De Bruijn EA, Guetens G, De Boeck G, Sparreboom A, Verweij J, Nooter K, authors. Chronic imatinib mesylate exposure leads to reduced intracellular drug accumulation by induction of the ABCG2 (BCRP) and ABCB1 (MDR1) drug transport pumps. Cancer Biol Ther. 2005;4:747–752. [Cross Ref] [PubMed]

Balabanov S, Gontarewicz A, Keller G, Raddrizzani L, Braig M, Bosotti R, Moll J, Jost E, Barett C, Rohe I, Bokemeyer C, Holyoake TL, Brümmendorf TH, authors. Abcg2 overexpression represents a novel mechanism for acquired resistance to the multi-kinase inhibitor Danusertib in BCR-ABL-positive cells in vitro. PLoS One. 2011;6:e19164 [Cross Ref] [PubMed]

Tang C, Schafranek L, Watkins DB, Parker WT, Moore S, Prime JA, White DL, Hughes TP, authors. Tyrosine kinase inhibitor resistance in chronic myeloid leukemia cell lines: investigating resistance pathways. Leuk Lymphoma. 2011;52:2139–2147. [Cross Ref] [PubMed]

Tsai J, Lee JT, Wang W, Zhang J, Cho H, Mamo S, Bremer R, Gillette S, Kong J, Haass NK, Sproesser K, Li L, Smalley KS, Fong D, Zhu YL, Marimuthu A, Nguyen H, Lam B, Liu J, Cheung I, Rice J, Suzuki Y, Luu C, Settachatgul C, Shellooe R, Cantwell J, Kim SH, Schlessinger J, Zhang KY, West BL, et al., authors. Discovery of a selective inhibitor of oncogenic B-Raf kinase with potent antimelanoma activity. Proc Natl Acad Sci U S A. 2008;105:3041–3046. [Cross Ref] [PubMed]

Durmus S, Sparidans RW, Wagenaar E, Beijnen JH, Schinkel AH, authors. Oral availability and brain penetration of the B-RAFV600E inhibitor vemurafenib can be enhanced by the P-GLYCOprotein (ABCB1) and breast cancer resistance protein (ABCG2) inhibitor elacridar. Mol Pharm. 2012;9:3236–3245. [Cross Ref] [PubMed]

Mittapalli RK, Vaidhyanathan S, Sane R, Elmquist WF, authors. Impact of P-glycoprotein (ABCB1) and Breast Cancer Resistance Protein (ABCG2) on the brain distribution of a novel B-RAF Inhibitor: Vemurafenib (PLX4032). J Pharmacol Exp Ther. 2012;342:33–40. [Cross Ref] [PubMed]

Michaelis M, Rothweiler F, Nerreter T, Van Rikxoort M, Sharifi M, Wiese M, Ghafourian T, Cinatl J Jr, authors. Differential effects of the oncogenic BRAF Inhibitor PLX4032 (vemurafenib) and its progenitor PLX4720 on ABCB1 function. J Pharm Pharm Sci. 2014;17:154–168. [PubMed]

Wu CP, Sim HM, Huang YH, Liu YC, Hsiao SH, Cheng HW, Li YQ, Ambudkar SV, Hsu SC, authors. Overexpression of ATP-binding cassette transporter ABCG2 as a potential mechanism of acquired resistance to vemurafenib in BRAF(V600E) mutant cancer cells. Biochem Pharmacol. 2013;85:325–334. [Cross Ref] [PubMed]

Weber K, Bartsch U, Stocking C, Fehse B, authors. A multicolor panel of novel lentiviral "gene ontology" (LeGO) vectors for functional gene analysis. Mol Ther. 2008;16:698–706. [Cross Ref] [PubMed]

Michaelis M, Rothweiler F, Nerreter T, Sharifi M, Ghafourian T, Cinatl J Jr, authors. Karanjin interferes with ABCB1, ABCC1, and ABCG2. J Pharm Pharm Sci. 2014;17:92–105. [PubMed]

Sterz K, Möllmann L, Jacobs A, Baumert D, Wiese M, authors. Activators of P-glycoprotein: Structure-activity relationships and investigation of their mode of action. ChemMedChem. 2009;4:1897–1911. [Cross Ref] [PubMed]

Häcker HG, de la Haye A, Sterz K, Schnakenburg G, Wiese M, Gütschow M, authors. Analogs of a 4-aminothieno[2,3-d]pyrimidine lead (QB13) as modulators of P-glycoprotein substrate specificity. Bioorg Med Chem Lett. 2009;19:6102–6105. [Cross Ref] [PubMed]

Chartrain M, Riond J, Stennevin A, Vandenberghe I, Gomes B, Lamant L, Meyer N, Gairin JE, Guilbaud N, Annereau JP, authors. Melanoma chemotherapy leads to the selection of ABCB5-expressing cells. PLoS One. 2012;7:e36762 [Cross Ref] [PubMed]

Brózik A, Hegedüs C, Erdei Z, Hegedus T, Özvegy-Laczka C, Szakács G, Sarkadi B, authors. Tyrosine kinase inhibitors as modulators of ATP binding cassette multidrug transporters: substrates, chemosensitizers or inducers of acquired multidrug resistance? Expert Opin Drug Metab Toxicol. 2011;7:623–642. [Cross Ref] [PubMed]

Chaudhary PM, Roninson IB, authors. Induction of multidrug resistance in human cells by transient exposure to different chemotherapeutic drugs. J Natl Cancer Inst. 1993;85:632–639. [Cross Ref] [PubMed]

Sukhai M, Piquette-Miller M, authors. Regulation of the multidrug resistance genes by stress signals. J Pharm Pharm Sci. 2000;3:268–280. [PubMed]

Cressman AM, Petrovic V, Piquette-Miller M, authors. Inflammation-mediated changes in drug transporter expression/activity: implications for therapeutic drug response. Expert Rev Clin Pharmacol. 2012;5:69–89. [Cross Ref] [PubMed]

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Figure 1.

Effect of PLX4032 and PLX4720 on ABCG2 activity. A) Influence of PLX4032 or PLX4720 on BODIPY-prazosine (1 μM) fluorescence in UKF-NB-3ABCG2 cells, B) time kinetics of BODIPY-prazosine (1 μM) fluorescence in UKF-NB-3ABCG2 cells in the presence of PLX4032 or PLX4720 after a 60 min pre-incubation period with subsequent wash-out of extracellular BODIPY-prazosine and PLX4032 or PLX4720 (control = BODIPY-prazosine incubation in the absence of drugs). C) ABCG2 ATPase activity in isolated membranes in the presence of PLX4032 or PLX4720 (control = activity in the absence of drugs). Sulfasalazine, a known ABCG2 substrate, was used for comparison. *P < 0.05 relative to non-treated controls.

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Figure 2.

Effect of PLX4032 and PLX4720 on ABCC1 activity. A) Influence of PLX4032 or PLX4720 on 5-CFDA (1 μM) fluorescence in G62 cells, B) time kinetics of 5-CFDA (1 μM) fluorescence in G62 cells in the presence of PLX4032 or PLX4720 after a 60 min pre-incubation period with subsequent wash-out of extracellular 5-CFDA and PLX4032 or PLX4720 (control = 5-CFDA incubation in the absence of drugs). C) ABCC1 ATPase activity in isolated membranes in the presence of PLX4032 or PLX4720 (control = activity in the absence of drugs). NEM-GS, a known ABCC1 substrate, was used for comparison. *P < 0.05 relative to non-treated controls.

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Figure 3.

Expression of ABCB1, ABCC1, and ABCG2 in V600 BRAF-mutated melanoma cells adapted to PLX4032, PLX4720, or the cytotoxic ABC transporter substrates vincristine (VCR) or mitoxantrone (MITOX) relative to the respective parental cell lines. White and black bars are used to facilitate the identification of resistant sub-lines that are derived from the same parental cell line. *P < 0.05 relative to parental cells.

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