A-803467, a tetrodotoxin-resistant sodium channel blocker, modulates ABCG2-mediated MDR in vitro and in vivo
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Nagaraju Anreddy1,*, Atish Patel1, Yun-Kai Zhang1, Yi-Jun Wang1, Suneet Shukla2, Rishil J. Kathawala1, Priyank Kumar1, Pranav Gupta1, Suresh V. Ambudkar2, John N. D. Wurpel1, Zhe-Sheng Chen1, Huiqin Guo3,*
1Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, St. John’s University, Queens, NY 11439, USA
2Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
3Department of Thoracic Surgery, Peking Union Medical College Hospital, Beijing 100730, P.R. China
*These authors have contributed equally to this work
Huiqin Guo, e-mail: email@example.com
Zhe-Sheng Chen, e-mail: firstname.lastname@example.org
Keywords: multidrug resistance, ABCG2, ABC transporters, non-small cell lung cancer
Received: July 22, 2015 Accepted: October 09, 2015 Published: October 22, 2015
ATP-binding cassette subfamily G member 2 (ABCG2) is a member of the ABC transporter superfamily proteins, which has been implicated in the development of multidrug resistance (MDR) in cancer, apart from its physiological role to remove toxic substances out of the cells. The diverse range of substrates of ABCG2 includes many antineoplastic agents such as topotecan, doxorubicin and mitoxantrone. ABCG2 expression has been reported to be significantly increased in some solid tumors and hematologic malignancies, correlated to poor clinical outcomes. In addition, ABCG2 expression is a distinguishing feature of cancer stem cells, whereby this membrane transporter facilitates resistance to the chemotherapeutic drugs. To enhance the chemosensitivity of cancer cells, attention has been focused on MDR modulators. In this study, we investigated the effect of a tetrodotoxin-resistant sodium channel blocker, A-803467 on ABCG2-overexpressing drug selected and transfected cell lines. We found that at non-toxic concentrations, A-803467 could significantly increase the cellular sensitivity to ABCG2 substrates in drug-resistant cells overexpressing either wild-type or mutant ABCG2. Mechanistic studies demonstrated that A-803467 (7.5 μM) significantly increased the intracellular accumulation of [3H]-mitoxantrone by inhibiting the transport activity of ABCG2, without altering its expression levels. In addition, A-803467 stimulated the ATPase activity in membranes overexpressed with ABCG2. In a murine model system, combination treatment of A-803467 (35 mg/kg) and topotecan (3 mg/kg) significantly inhibited the tumor growth in mice xenografted with ABCG2-overexpressing cancer cells. Our findings indicate that a combination of A-803467 and ABCG2 substrates may potentially be a novel therapeutic treatment in ABCG2-positive drug resistant cancers.
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