title: In vitro, in vivo and ex vivo characterization of ibrutinib: a potent inhibitor of the efflux function of the transporter MRP1.
abstract: OBJECTIVE
  The transporter, multidrug resistance protein 1 (MRP1, ABCC1), plays a critical role in the development of multidrug resistance (MDR). Ibrutinib is an inhibitor of Bruton's tyrosine kinase. Here we investigated the reversal effect of ibrutinib on MRP1-mediated MDR.
  
  
  METHODS
  Cytotoxicity was determined by MTT assay. The expression of protein was detected by Western blot. RT-PCR and Q-PCR were performed to detect the expression of MRP1 mRNA. The intracellular accumulation and efflux of substrates for MRP1 were measured by scintillation counter and flow cytometry. HEK293/MRP1 cell xenografts in nude mice were established to study the effects of ibrutinib in vivo.
  
  
  RESULTS
  Ibrutinib significantly enhanced the cytotoxicity of MRP1 substrates in HEK293/MRP1 and HL60/Adr cells overexpressing MRP1. Furthermore, ibrutinib increased the accumulation of substrates in these MRP1-overexpressing cells by inhibiting the drug efflux function of MRP1. However, mRNA and protein expression of MRP1 remained unaltered after treatment with ibrutinib in MRP1-overexpressing cells. In vivo, ibrutinib enhanced the efficacy of vincristine to inhibit the growth of HEK293/MRP1 tumour xenografts in nude mice. Importantly, ibrutinib also enhances the cytotoxicity of vincristine in primary cultures of leukaemia blasts, derived from patients.
  
  
  CONCLUSIONS
  Our results indicated that ibrutinib significantly increased the efficacy of the chemotherapeutic agents which were MRP1 substrates, in MRP1-overexpressing cells, in vitro, in vivo and ex vivo. These findings will lead to further studies on the effects of a combination of ibrutinib with chemotherapeutic agents in cancer patients overexpressing MRP1.
authors.affiliation: Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John's University, Queens, NY, USA; State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Sun Yat-Sen University Cancer Center, Guangzhou, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.forename: Atish
authors.initials: A
authors.lastname: Patel
authors.forename: Shao-Lin
authors.initials: SL
authors.lastname: Ma
authors.forename: Xiao Jie
authors.initials: XJ
authors.lastname: Li
authors.forename: Yun-Kai
authors.initials: YK
authors.lastname: Zhang
authors.forename: Pei-Qi
authors.initials: PQ
authors.lastname: Yang
authors.forename: Rishil J
authors.initials: RJ
authors.lastname: Kathawala
authors.forename: Yi-Jun
authors.initials: YJ
authors.lastname: Wang
authors.forename: Nagaraju
authors.initials: N
authors.lastname: Anreddy
authors.forename: Li-Wu
authors.initials: LW
authors.lastname: Fu
authors.forename: Zhe-Sheng
authors.initials: ZS
authors.lastname: Chen
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives; D000077329:Agammaglobulinaemia Tyrosine Kinase; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D057809:HEK293 Cells; D018922:HL-60 Cells; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D008819:Mice, Nude; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000037:antagonists & inhibitors*; D010880:Piperidines; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D011720:Pyrazoles / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology*; D012333:RNA, Messenger / Q000187:drug effects* / Q000378:metabolism; D014750:Vincristine / Q000494:pharmacology; D023041:Xenograft Model Antitumor Assays
chemical_list: D000225:Adenine; D000077329:Agammaglobulinaemia Tyrosine Kinase; D000970:Antineoplastic Agents; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D010880:Piperidines; D047428:Protein Kinase Inhibitors; D011505:Protein-Tyrosine Kinases; D011720:Pyrazoles; D011743:Pyrimidines; D012333:RNA, Messenger; D014750:Vincristine; C551803:ibrutinib; C000625951:Btk protein, mouse; C421109:multidrug resistance-associated protein 1