3,3'-diindolylmethane reduces levels of HIF-1alpha and HIF-1 activity in hypoxic cultured human cancer cells

• Published in: Biochemical pharmacology 2008-05, Vol.75 (9), p.1858
• Main Authors: Riby, Jacques E, Firestone, Gary L, Bjeldanes, Leonard F
• Format: Article
• Language: English
• Subjects: Anticarcinogenic Agents - pharmacology; Blotting, Western; Cell Hypoxia; Cell Line, Tumor; Humans; Hypoxia-Inducible Factor 1, alpha Subunit - genetics; Hypoxia-Inducible Factor 1, alpha Subunit - metabolism; Indoles - pharmacology; Luciferases - genetics; Proton-Translocating ATPases - antagonists & inhibitors; Proton-Translocating ATPases - metabolism; Reactive Oxygen Species - metabolism; Reverse Transcriptase Polymerase Chain Reaction; Transcription, Genetic - drug effects; Transfection
• ISSN: 1873-2968
• DOI: 10.1016/j.bcp.2008.01.017

3,3'-diindolylmethane (DIM) is a chemopreventive and chemotherapeutic phytochemical derived from the metabolism of indoles found at high concentrations in cruciferous vegetables. We have previously shown that DIM exhibits anti-angiogenic properties in cultured vascular endothelial cells and in Matrigel plug assays in rodents. In the present study, we demonstrate that DIM reduces the level of hypoxia-inducible factor (HIF)-1alpha in hypoxic tumor cell lines, as well as HIF-1 transcriptional activity as measured by a reporter assay. Moreover, DIM inhibited the expression of HIF-1-responsive endogenous genes, resulting in the reduced expression of key hypoxia responsive factors, VEGF, furin, enolase-1, glucose transporter-1 and phosphofructokinase. DIM reduced the level of HIF-1alpha in hypoxic cells by increasing the rate of the prolylhydroxylase- and proteasome-mediated degradation of HIF-1alpha, and by decreasing the rate of HIF-1alpha transcription. Using enzyme kinetics studies, we established that DIM interacts with the oligomycin-binding site on the F0 transmembrane component of mitochondrial F1F0-ATPase. The contributions of the resulting increases in levels of ROS and O2 in hypoxic cells to the inhibitory effects of DIM on HIF-1alpha expression are discussed. These studies are the first to show that DIM can decrease the accumulation and activity of the key angiogenesis regulatory factor, HIF-1alpha, in hypoxic tumor cells.