Mechanistic & functional genomic studies identify marine sesquterpene quinones that activate HIF-1 and induce VEGF expression

The transcription factor hypoxia-inducible factor-1 (HIF-1) promotes cellular survival and adaptation under hypoxic conditions. Activators of HIF-1 show promise in the prevention and/or treatment of cardiovascular and ischemic disorders. Marine invertebrate extracts from the NCI's Open Repository were evaluated for their ability to activate HIF-1. The sponge Dactylospongia elegans Thiele (Thorectidae) afforded 4 new sesquiterpene quinones, a sesquiterpene phenol, ilimaquinone, and 3 previously reported analogues. The quinones that possess a 2-hydroxy-5-methoxy-1,4-benzoquinone moiety activated HIF-1 and increased vascular endothelial growth factor (VEGF) protein levels in normoxic T47D cells. A functional genomic approach was used to examine a yeast genome-wide deletion mutant library and identify mutants that exhibit either ilimaquinone hypersensitivity or resistance. Of the 31 hypersensitive mutants identified, 28 exhibited a synthetic fitness defect and 3 possessed a synthetic defect lethal to yeast cells. Golgi-related mutations and mutants that affected mitochondrial function, ubiquitin-specific proteases, and cellular iron homeostasis were identified. Mechanistic studies suggest that these quinones activate HIF-1 and induce HIF-1 target gene expression by inhibiting Fe⁺⁺-dependent dioxygenases known as HIF prolyl hydroxylases (HPHs). Cellular HPHs are required for the proteasome-mediated HIF-1α degradation under normoxic conditions.