Therefore, to identify novel HIF-regulated target genes we developed an inducible expression system to selectively express either HIF-1α or HIF-2α in PC-12 rat pheochromocytoma cells, and performed siRNA-targeted knockdown of endogenous HIF-1α or HIF-2α in neuroblastoma cells. The gene discussed is HIF1A; the disease is hereditary pheochromocytoma-paraganglioma.