title: Enhancement of hexokinase II inhibitor-induced apoptosis in hepatocellular carcinoma cells via augmenting ER stress and anti-angiogenesis by protein disulfide isomerase inhibition.
abstract: 3-bromopyruvate (3-BP), a hexokinase (HK) II inhibitor, promotes tumor cell death by inducing endoplasmic reticulum (ER) stress in human hepatocellular carcinoma (HCC) cell lines. Protein disulfide isomerase (PDI) is an essential folding catalyst and attenuates ER stress by folding the misfolded proteins. We examined if PDI is expressed in hypoxic HCC cells, and evaluated its inhibition potentiated HK II inhibitor-induced ER stress in hypoxic HCC cells. HCC apoptotic cell death was assessed by DAPI staining and apoptotic signaling pathways were explored by immunoblot analysis. An in vivo model of HCC was established in C3H mice intradermally with implanted MH134 cells. 3-BP with/without a PDI inhibitor (bacitracin) was subsequently administered. The anti-tumor efficacies were evaluated by measuring tumor volumes and quantifying apoptotic cells and microvessel densities (MVDs). HCC cells were found to express PDI in a hypoxia-inducible manner. The simultaneous treatment of bacitracin and 3-BP enhanced 3-BP-induced apoptosis. This enhancement was attributed to increased ER stress and JNK activation compared to the cells treated with just 3-BP. In an in vivo model of HCC, tumor growth was significantly suppressed in mice co-treated with bacitracin and 3-BP, and the percentages of apoptotic cells significantly increased and MVDs significantly decreased. These results demonstrated that PDI was induced in hypoxic HCC tissue and that PDI inhibition enhanced HK II inhibitor-induced anti-tumor efficacy synergistically via augmenting ER stress and anti-angiogenesis in vivo. Thus, blockage of PDI activity in combination with HK II inhibitor may be therapeutically useful in HCCs.
authors.affiliation: Department of Internal Medicine and Liver Research Institute, Seoul National University College of Medicine, 101 Daehak-ro, Jongno-gu, Seoul 110-744, Republic of Korea.
authors.forename: Su Jong
authors.initials: SJ
authors.lastname: Yu
authors.forename: Jung-Hwan
authors.initials: JH
authors.lastname: Yoon
authors.forename: Jong-In
authors.initials: JI
authors.lastname: Yang
authors.forename: Eun Ju
authors.initials: EJ
authors.lastname: Cho
authors.forename: Min Sun
authors.initials: MS
authors.lastname: Kwak
authors.forename: Eun Sun
authors.initials: ES
authors.lastname: Jang
authors.forename: Jeong-Hoon
authors.initials: JH
authors.lastname: Lee
authors.forename: Yoon Jun
authors.initials: YJ
authors.lastname: Kim
authors.forename: Hyo-Suk
authors.initials: HS
authors.lastname: Lee
authors.forename: Chung Yong
authors.initials: CY
authors.lastname: Kim
mesh_terms: D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001414:Bacitracin; D006528:Carcinoma, Hepatocellular / Q000378:metabolism*; D045744:Cell Line, Tumor; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D006593:Hexokinase / Q000037:antagonists & inhibitors*; D006801:Humans; D015151:Immunoblotting; D007211:Indoles; D008297:Male; D051379:Mice; D055806:Microvessels / Q000473:pathology; D019704:Protein Disulfide-Isomerases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011773:Pyruvates / Q000494:pharmacology*; D018709:Statistics, Nonparametric
chemical_list: D018906:Antineoplastic Agents, Alkylating; D007211:Indoles; D011773:Pyruvates; D001414:Bacitracin; C007293:DAPI; C017092:bromopyruvate; D006593:Hexokinase; D019704:Protein Disulfide-Isomerases