Modulation of hypoxia-inducible factor-1α expression by mitochondrial NADP+-dependent isocitrate dehydrogenase.
The transcription factor hypoxia-inducible factor-1 (HIF-1) is an important regulator of the tumor response to hypoxia, including increased angiogenesis, glycolytic metabolism, and resistance to apoptosis. In the current study, small interfering RNA (siRNA)-mediated knockdown of mitochondrial NADP(+)-dependent isocitrate dehydrogenase (IDPm) suppressed hypoxia-induced stimulation of HIF-1α protein expression in PC3 human prostate cancer cells. Treatment with the 26S proteasome inhibitor MG132 failed to abrogate the suppression of HIF-1α accumulation induced by IDPm knockdown, whereas HIF-1α levels were reduced by cycloheximide treatment in both control and IDPm siRNA-transfected cells. These results suggested that the suppression of HIF-1α accumulation by IDPm knockdown in PC3 cells was due to an inhibition of HIF-1α transcription. Inactivation of the phosphoinsotide-3 kinase (PI3K)/Akt pathway decreased HIF-1α expression through inactivation of Sp1. Thus, IDPm siRNA functioned as a potentially useful agent for targeting chemo- and radio-resistant hypoxic cells within solid tumors through inhibition of HIF-1α expression.
Kim
Sung Youl
SY
School of Life Sciences and Biotechnology, College of Natural Sciences, Kyungpook National University, Taegu 702-701, Republic of Korea.
Park
Jeen-Woo
JW
D000111:Acetylcysteine / Q000494:pharmacology; D045744:Cell Line, Tumor; D003513:Cycloheximide / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D007521:Isocitrate Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D007976:Leupeptins / Q000494:pharmacology; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D016329:Sp1 Transcription Factor / Q000378:metabolism
D000111:Acetylcysteine; D003513:Cycloheximide; D015853:Cysteine Proteinase Inhibitors; D016166:Free Radical Scavengers; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007521:Isocitrate Dehydrogenase; D007976:Leupeptins; D024101:Mitochondrial Proteins; D019869:Phosphatidylinositol 3-Kinases; D011500:Protein Synthesis Inhibitors; D051057:Proto-Oncogene Proteins c-akt; D016329:Sp1 Transcription Factor; C538784:IDH2 protein, human; C039355:isocitrate dehydrogenase (NADP+); C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde