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Hypoxic conditions regulate several metabolic enzymes and transcription factors that are involved in cancer, ischemia and pulmonary diseases. The Ras homolog (Rho) family, including Rho member A (RhoA), is involved in reorganization of the actin cytoskeleton, cell migration and in the regulation of apoptosis and gene transcription. The aim of the present study was to investigate the expression of hypoxia-inducible factor (HIF)-α and the activity of RhoA in PC12 neuroblastoma cells under hypoxic conditions. The upregulation of HIF-α and RhoA by hypoxia was determined using reverse transcription-quantitative polymerase chain reaction and western blot assays, cell apoptosis was analyzed using flow cytometry, and the activity of caspase 3 was examined using a western blot assay and caspase 3 activity assay kit. The PC12 cells were induced to apoptosis following exposure to hypoxia, and exhibited increased expression of HIF-α and increased mRNA and protein expression levels of RhoA. The overexpression of HIF-α attenuated the hypoxia-induced apoptosis of the PC12 cells. In addition, RhoA knockdown using small interfering RNA abrogated the antagonism of HIF-1α towards hypoxia-induced apoptosis. The results of the present study confirmed the protective role of HIF-1α and RhoA in hypoxia-induced PC12 cell apoptosis, and that the upregulation of HIF-1α by hypoxia is RhoA-dependent. [ABSTRACT FROM AUTHOR]

Background: ECRG4 has been shown to be a candidate tumor suppressor in several tumors, but its role in glioma remains poorly understood. In this study, we examined the mRNA expression of ECRG4 and investigated its biological role in glioma cells. Methods: Real-time PCR was used to examine expression of ECRG4 in gliomas and their matched brain tissues. The effect of ECRG4 expression on cell proliferation, invasion, and migration was investigated in human U251 glioma cells. Finally, the regulation of transcription factor NF-kB by ECRG4 was evaluated by western blotting. Results: Of the 10 paired samples analyzed, 9 glioma tissues displayed the decreased expression of ECRG4 compared to matched normal brain tissues. Cells transfected with ECRG4 showed significantly decreased cell proliferation as evaluated by MTT and colony formation assays. Furthermore, overexpression inhibited cell migration and invasion in transwell and Boyden chamber experiments and retarded the cell cycle progression from G1 to S phase by FACSCaliber cytometry. Protein levels of nuclear transcription factor NF-kB, which is involved in cell proliferation, inversely correlated with ECRG4 expression. Conclusion: Our data suggest that ECRG4 serves as a tumor suppressor in glioma. [ABSTRACT FROM AUTHOR]