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Research Articles: Therapeutics, Targets, and Development

Apoptosis-inducing antitumor efficacy of hexokinase II inhibitor in hepatocellular carcinoma

¹ Department of Internal Medicine and Liver Research Institute and ² Department of Nuclear Medicine, Seoul National University College of Medicine; ³ Department of Nuclear Medicine, Korea Institute of Radiological and Medical Sciences, Seoul, Korea

Requests for reprints: Jung-Hwan Yoon, Seoul National University Hospital, 28 Yungun-dong, Chongno-gu, Seoul 110-744, South Korea. Phone: 82-2-2072-2228; Fax: 82-2-743-6701. E-mail: yoonjh{at}snu.ac.kr

Abstract

Hypoxia stimulates hepatocellular carcinoma (HCC) cell growth via hexokinase (HK) II induction, and alternatively, HK II inhibition induces apoptosis by activating mitochondrial signaling. This study was to investigate whether the induction of HK II by hypoxia is associated with enhanced mitochondrial stability and to confirm the apoptosis-inducing efficacy of HK II inhibitor in an in vivo model of HCC. Mitochondrial stability was examined by treating isolated mitochondria with deoxycholate, a permeability-enhancing agent. Alteration of permeability transition pore complex composition was analyzed by immunoprecipitation and immunoblotting. An in vivo model of HCC was established in C3H mice i.d. implanted with MH134 cells. The antitumor efficacy of i.p. given 3-bromopyruvate (3-BrPA), a HK II inhibitor, was evaluated by measuring tumor volumes and quantifying apoptosis using terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling staining and ^99mTc-hydrazinonicotinamide-Annexin V scans. Hypoxia enhanced mitochondrial stability, and this was inhibited by 3-BrPA treatment. In particular, HK II levels in permeability transition pore complex immunoprecipitates were reduced after 3-BrPA treatment. In mice treated with 3-BrPA, mean tumor volumes and tumor volume growth were found to be significantly reduced. Moreover, percentages of terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling–positive cells were significantly increased in 3-BrPA–treated mice, and this apoptosis-inducing efficacy was reflected in vivo by ^99mTc-hydrazinonicotinamide-Annexin V imaging. Our results show that hypoxia enhances mitochondrial stability via HK II induction and that HK II inhibitor treatment exhibits an in vivo antitumor effect by inducing apoptosis. Therefore, HK II inhibitors may be therapeutically useful for the treatment of advanced infiltrative hypovascular HCCs, which are growing in a hypoxic environment. [Mol Cancer Ther 2007;6(9):2554–62]

Grant support: Korean Foundation of Liver Research, Korea Health 21 R&D Project (0412-CR01-0704-0001), and National Cancer Control R&D Program 2003, Ministry of Health and Welfare, Republic of Korea.

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

Received 2/20/07; revised 6/21/07; accepted 8/ 2/07.