title: β-carotene reverses multidrug resistant cancer cells by selectively modulating human P-glycoprotein function.
abstract: BACKGROUND
  The issue of multidrug resistance (MDR) cancer is one of the major barriers to successful chemotherapy treatment. The ATP-binding cassette (ABC) efflux transporters play an important role in the chemotherapeutic failure. Several generations of ABC efflux transporter inhibitors have been developed, however, none of them could provide better clinical outcome due to systemic toxicities and significant drug-drug interactions. Therefore, the present study focused on identifying the effect of the natural carotenoid on ABC transporters and may provide a safer choice to defeat MDR cancer.
  
  
  OBJECTIVE
  The aim of the present study was to evaluate the inhibitory potency of β-carotene on the ABC efflux transporters, as well as the reversal effect of β-carotene toward MDR cancers. The underlying molecular mechanisms and inhibitory kinetics of β-carotene on the major ABC efflux transporter, P-glycoprotein, were further investigated.
  
  
  METHODS
  The human P-gp (ABCB1/Flp-In(TM)-293), MRP1 (ABCC1/Flp-In(TM)-293) and BCRP (ABCG2/Flp-In(TM)-293) stable expression cells were established by using the Flp-In(TM) system. The cytotoxicity of β-carotene was evaluated by MTT assay in the established cell lines, sensitive cancer cell lines (HeLaS3 and NCI-H460) and resistant cancer cell lines (KB-vin and NCI-H460/MX20). Surface protein detection assay and eFluxx-ID Green Dye assay were applied for confirmation of surface expression and function of the transporters. The transporter inhibition potency of β-carotene was evaluated by calcein-AM uptake assay and mitoxantrone accumulation assay. Further interaction kinetics between β-carotene and P-gp were analyzed by rhodamine123 and doxorubicin efflux assay. The influence of β-carotene on ATPase activity was evaluated by Pgp-Glo(TM) Assay System.
  
  
  RESULTS
  Among the tested ABC efflux transporters, β-carotene significantly inhibited human P-gp efflux function without altering ABCB1 mRNA expression. Furthermore, β-carotene stimulated both P-gp basal ATPase activity and the verapamil-stimulated P-gp ATPase activity. In addition, β-carotene exerted partially inhibitory effect on BCRP efflux function. The combination of β-carotene and chemotherapeutic agents significantly potentiated their cytotoxicity in both cell stably expressed human P-gp (ABCB1/Flp-In(TM)-293) and MDR cancer cells (KB-vin and NCI-H460/MX20).
  
  
  CONCLUSIONS
  The present study indicated that β-carotene may be considered as a chemo-sensitizer and regarded as an adjuvant therapy in MDR cancer treatment.
authors.affiliation: Department of Pharmacy, College of Pharmacy, China Medical University, 91 Hsueh-Shih Road, Taichung, Taiwan 40402, R.O.C.
authors.forename: Yu-Ning
authors.initials: YN
authors.lastname: Teng
authors.affiliation: Department of Pharmacy, College of Pharmacy, China Medical University, 91 Hsueh-Shih Road, Taichung, Taiwan 40402, R.O.C.
authors.forename: Ming-Jyh
authors.initials: MJ
authors.lastname: Sheu
authors.affiliation: Department of Pharmacy, College of Pharmacy, China Medical University, 91 Hsueh-Shih Road, Taichung, Taiwan 40402, R.O.C.; Department of Pharmacy, China Medical University Hospital, 2 Yude Road, Taichung, 40447, Taiwan, R.O.C.
authors.forename: Yow-Wen
authors.initials: YW
authors.lastname: Hsieh
authors.affiliation: Department of Public Health, China Medical University, 91 Hsueh-Shih Road, Taichung, Taiwan 40402, R.O.C.
authors.forename: Ruey-Yun
authors.initials: RY
authors.lastname: Wang
authors.affiliation: Center for Drug Abuse and Addiction, China Medical University, 91 Hsueh-Shih Road, Taichung, Taiwan 40402, R.O.C.
authors.forename: Yao-Chang
authors.initials: YC
authors.lastname: Chiang
authors.affiliation: Department of Pharmacy, College of Pharmacy, China Medical University, 91 Hsueh-Shih Road, Taichung, Taiwan 40402, R.O.C.; Department of Pharmacy, China Medical University Hospital, 2 Yude Road, Taichung, 40447, Taiwan, R.O.C.. Electronic address: cc0206hung@gmail.com.
authors.forename: Chin-Chuan
authors.initials: CC
authors.lastname: Hung
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology; D045744:Cell Line, Tumor / Q000187:drug effects; D004317:Doxorubicin / Q000494:pharmacology; D018432:Drug Resistance, Multiple / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D006801:Humans; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D009369:Neoplasms / Q000378:metabolism*; D014700:Verapamil / Q000494:pharmacology; D019207:beta Carotene / Q000494:pharmacology*
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000251:Adenosine Triphosphatases; D000970:Antineoplastic Agents; D004317:Doxorubicin; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D014700:Verapamil; D019207:beta Carotene; C513055:ABCB1 protein, human; C116614:ABCG2 protein, human; C421109:multidrug resistance-associated protein 1
keywords: Multidrug resistant cancer; P-gp; Reversal effects; β-carotene