HDAC4 Protein Regulates HIF1α Protein Lysine Acetylation and Cancer Cell Response to Hypoxia

Hypoxia-inducible factor 1 alpha (HIF1 alpha) is an essential part of the HIF-1 transcriptional complex that regulates angiogenesis, cellular metabolism, and cancer development. In von Hippel-Lindau (VHL)-null kidney cancer cell lines, we reported previously that HIF1 alpha proteins can be acetylated and inhibited by histone deacetylase (HDAC) inhibitors or specific siRNA against HDAC4. To investigate the mechanism and biological consequence of the inhibition, we have generated stableHDAC4 knockdown via shRNA in VHL-positive normal and cancer cell lines. We report that HDAC4 regulates HIF1 alpha protein acetylation and stability. Specifically, the HIF1 alpha protein acetylation can be increased by HDAC4 shRNA and decreased by HDAC4 overexpression. HDAC4 shRNA inhibits HIF1 alpha protein stability. In contrast, HDAC1 or HDAC3 shRNA has no such inhibitory effect. Mutations of the first five lysine residues (lysine 10, 11, 12, 19, and 21) to arginine within the HIF1 alpha N terminus reduce protein acetylation but render the mutant HIF1 alpha protein resistant to HDAC4 and HDACi-mediated inhibition. Functionally, in VHL-positive cancer cell lines, stable inhibition of HDAC4 decreases both the HIF-1 transcriptional activity and a subset of HIF-1 hypoxia target gene expression. On the cellular level, HDAC4 inhibition reduces the hypoxia-related increase of glycolysis and resistance to docetaxel chemotherapy. Taken together, the novel biological relationship between HDAC4 and HIF1 alpha presented here suggests a potential role for the deacetylase enzyme in regulating HIF-1 cancer cell response to hypoxia and presents a more specific molecular target of inhibition.