Regulation of the HIF-1α protein under hypoxic and normoxic conditions, the effect of PHD inhibitors on HIF-1α stabilization, and possible effects on HSC quiescence/proliferation via the ATM kinase and mTORC pathways. S6R kinase indicates S6 ribosomal protein kinase; EIF4e, eukaryotic initiation factor 4E; HRE, hypoxia-responsive element; REDD1, regulated in development and DNA response 1.