Journal Article

MMPSense, IVIS, Animals; Cell Hypoxia; Cell Line, Tumor; Cell Movement; Enzyme Activation; Extracellular Signal-Regulated MAP Kinases/metabolism; Gene Knockdown Techniques; Glioblastoma/*enzymology/*pathology; Humans; JNK Mitogen-Activated Protein Kinases/metabolism; Matrix Metalloproteinase 9/metabolism; Mice; Mice, SCID; Molecular Imaging/*methods; NADPH Oxidase/*metabolism; NF-kappa B/metabolism; Neoplasm Invasiveness; Reactive Oxygen Species/metabolism; Tumor Microenvironment; Xenograft Model Antitumor Assays

PURPOSE: We determined the impact of the cycling hypoxia tumor microenvironment on tumor cell invasion and infiltration in U87 human glioblastoma cells and investigated the underlying mechanisms using molecular bio-techniques and imaging. PROCEDURES: The invasive phenotype of U87 cells and xenografts exposed to experimentally imposed cycling hypoxic stress in vitro and in vivo was determined by the matrigel invasion assay in vitro and dual optical reporter gene imaging in vivo. RNAi-knockdown technology was utilized to study the role of the NADPH oxidase subunit 4 (Nox4) on cycling hypoxia-mediated tumor invasion. RESULTS: Cycling hypoxic stress significantly promoted tumor invasion in vitro and in vivo. However, Nox4 knockdown inhibited this effect. Nox4-generated reactive oxygen species (ROS) are required for cycling hypoxia-induced invasive potential in U87 cells through the activation of NF-kappaB- and ERK-mediated stimulation of MMP-9. CONCLUSIONS: Cycling hypoxia-induced ROS via Nox4 should be considered for therapeutic targeting of tumor cell invasion and infiltration in glioblastoma.