Reversal of multidrug resistance by 4-chloro-N-(3-((E)-3-(4-hydroxy-3- methoxyphenyl)acryloyl)phenyl)benzamide through the reversible inhibition of P-glycoprotein Yong Kee Kim a, * , Yong Jin Song a , Dong-Wan Seo b , Dong-Won Kang a , Hoi Young Lee c , Dong-Kwon Rhee d , Jeung-Whan Han d , Chan Mug Ahn e , Seokjoon Lee a , Su-Nam Kim f, * a College of Medicine, Kwandong University, Gangneung 210-701, Republic of Korea b Department of Molecular Bioscience, Kangwon National University, Chuncheon 200-701, Republic of Korea c College of Medicine, Konyang University, Daejeon 302-718, Republic of Korea d College of Pharmacy, Sungkyunkwan University, Suwon 440-746, Republic of Korea e Wonju College of Medicine, Yonsei University, Wonju 220-701, Republic of Korea f KIST Gangneung Institute, Gangneung 210-340, Republic of Korea Received 20 January 2007 Available online 30 January 2007 Abstract Overexpression of P-glycoprotein (P-gp) is one of the major obstacles to successful cancer chemotherapy. In this study, we examined the ability of 4-chloro-N-(3-((E)-3-(4-hydroxy-3-methoxyphenyl)acryloyl)phenyl)benzamide (C-4) to reverse multidrug resistance (MDR) in P-gp expressing KBV20C cells. Treatment of KBV20C cells with C-4 led to a dramatic increase in paclitaxel- or vincristine-induced cyto- toxicity without any cytotoxicity by itself. In parallel, C-4 treatment caused an increase in apoptotic cell death by paclitaxel or vincristine. Furthermore, C-4 treatment significantly increases in intracellular accumulation of fluorescent P-gp substrate rhodamine 123, indicating that C-4 treatment leads to reversal of the MDR phenotype resulting from an increased accumulation of anticancer drugs by inhibiting drug efflux function of P-gp. This notion is further supported by the observation that C-4 treatment potentiates paclitaxel-induced G 2 /M arrest of the cell cycle. In addition, the drug efflux function of P-gp was reversibly inhibited by C-4 treatment, while the expression level of P-gp was not affected. Collectively, our results describe the potential of C-4 to reverse the P-gp-mediated MDR phenotype through reversible inhi- bition of P-gp function, which may make it an attractive new agent for the chemosensitization of cancer cells. Ó 2007 Elsevier Inc. All rights reserved. Keywords: Multidrug resistance; P-glycoprotein; Curcumin; 4-Chloro-N-(3-((E)-3-(4-hydroxy-3-methoxyphenyl)acryloyl)phenyl)benzamide Multidrug resistance (MDR) is a significant impedi- ment to providing effective cancer chemotherapy to many patients and a major mechanism for resistance of cancer cells to many structurally and functionally unrelated drugs [1]. The MDR phenotype is often associated with the overexpression of drug efflux pumps, known as ATP-binding cassette (ABC) transporters, in the plasma membrane of cancer cells. P-glycoprotein (P-gp), a 170- kDa transmembrane glycoprotein encoded by the ABCB1 (MDR1) gene, is the best characterized drug efflux pump [2–4]. A wide range of anticancer drugs including anthra- cyclines, vinca alkaloids, and taxanes have been demon- strated to be substrates for P-gp [1]. Because overexpression of P-gp has been shown to confer MDR in cultured cells and has also been implicated in clinical MDR, P-gp overexpression appears to be closely corre- lated with poor prognosis for a number of human can- cers [4,5]. Therefore, a successful inhibition of P-gp transporter function or its expression may overcome the MDR phenotype by increasing intracellular accumu- lation of anticancer drugs. 0006-291X/$ - see front matter Ó 2007 Elsevier Inc. All rights reserved. doi:10.1016/j.bbrc.2007.01.117 * Corresponding authors. Fax: +82 33 641 1074 (Y.K. Kim), +82 33 650 7199 (S.-N. Kim). E-mail addresses: yksnbk@kwandong.ac.kr (Y.K. Kim), snkim@kist. re.kr (S.-N. Kim). www.elsevier.com/locate/ybbrc Biochemical and Biophysical Research Communications 355 (2007) 136–142