Hypoxia stimulates proliferation of human hepatoma cells through the induction of hexokinase II expression.
OBJECTIVE
In a hypoxic state, a glycolytic system is operating as a salvage pathway of generating ATP, and hexokinase II, the first enzyme in this system, might be over-expressed in hepatocellular carcinomas (HCCs). This study was to evaluate if hexokinase II is participating in HCC cell survival in a hypoxic state, and to analyze the mechanism of cell death caused by hexokinase II-specific inhibition.


METHODS
Human hepatoma cell lines were grown either in a normoxic or hypoxic condition. Hexokinase II and hypoxia-inducible factor-1alpha (HIF-1alpha) expression were evaluated using immunoblot techniques. Cell growth was assessed using the MTS assay. Apoptotic signaling cascades were explored by immunoblot analysis.


RESULTS
Hypoxia stimulated HCC cellular growth through HIF-1alpha-dependent induction of hexokinase II expression. The hexokinase II-specific inhibitor, 3-bromopyruvate, significantly suppressed cellular growth in a hypoxic state compared to cells in a normoxic condition. This suppression was due to the induction of apoptosis through activating mitochondrial apoptotic signaling cascades.


CONCLUSIONS
This study demonstrates that hypoxia stimulates HCC cellular growth through hexokinase II induction, and its inhibition induces apoptotic cell death. Therefore, hexokinase II induction may participate in HCC progression and the blockage of this enzyme may therapeutically be efficacious in human HCCs.
Gwak
Geum-Youn
GY
Department of Internal Medicine and Liver Research Institute, Seoul National University College of Medicine, 28 Yungun-dong, Chongno-gu, Seoul 110-744, South Korea.
Yoon
Jung-Hwan
JH
Kim
Kang Mo
KM
Lee
Hyo-Suk
HS
Chung
Jin Wook
JW
Gores
Gregory J
GJ
D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000473:pathology*; D002455:Cell Division; D015687:Cell Hypoxia / Q000502:physiology*; D045744:Cell Line, Tumor; D002470:Cell Survival; D003600:Cytosol / Q000201:enzymology; D004790:Enzyme Induction; D006593:Hexokinase / Q000096:biosynthesis*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D008113:Liver Neoplasms / Q000201:enzymology / Q000473:pathology*; D008856:Microscopy, Fluorescence; D008930:Mitochondria, Liver / Q000201:enzymology; D014157:Transcription Factors / Q000502:physiology
C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D014157:Transcription Factors; D007770:L-Lactate Dehydrogenase; D006593:Hexokinase