Synthesis of (aryloxyacetylamino)-isonicotinic/nicotinic acid analogues as potent hypoxia-inducible factor (HIF)-1alpha inhibitors

We report a new series of HIF-1alpha inhibitors which were obtained through structural modifications of previously reported lead 1. The in vitro inhibitory potencies of newly synthesized compounds were evaluated against hypoxia-induced HIF-1 activation using cell-based reporter assay in three human cancer cell lines including SK-Hep-1, Hep3B, and AGS cells. Several compounds displayed significant inhibitory activity in all the three tested cell lines. In particular, analogue 17 displayed potent inhibition of hypoxia-induced accumulation of HIF-1alpha protein in Hep3B cell line, in addition to the dose-dependent inhibition of HIF-1 target genes VEGF and EPO.     

Structure-activity relationships study of neolamellarin A and its analogues as hypoxia inducible factor-1 (HIF-1) inhibitors

The novel marine pyrrole alkaloid neolamellarin A derived from sponge has been shown to inhibit hypoxia-induced HIF-1 activity. In this work, we designed and synthesized neolamellarin A and its series of derivatives by a convergent synthetic strategy. The HIF-1 inhibitory activity and cytotoxicity of these compounds were evaluated in Hela cells by dual-luciferase reporter gene assay and MTT assay, respectively. The results showed that neolamellarin A 1 (IC₅₀ = 10.8 ± 1.0 μM) and derivative 2b (IC₅₀ = 11.9 ± 3.6 μM) had the best HIF-1 inhibitory activity and low cytotoxicity. Our SAR research focused on the effects of key regions aliphatic carbon chain length, aromatic ring substituents and C-7 substituent on biological activity, providing a basis for the subsequent research on the development of novel pyrrole alkaloids as HIF-1 inhibitors and design of small molecule probes for target protein identification.     

Phosphatidylinositol 3-kinase signaling controls levels of hypoxia-inducible factor 1.

The phosphatidylinositol 3-kinase (PI3K) signaling pathway has inherent oncogenic potential. It is up-regulated in diverse human cancers by either a gain of function in PI3K itself or in its downstream target Akt or by a loss of function in the negative regulator PTEN. However, the complete consequences of this up-regulation are not known. Here we show that insulin and epidermal growth factor or an inactivating mutation in the tumor suppressor PTEN specifically increase the protein levels of hypoxia-inducible factor (HIF) 1alpha but not of HIF-1beta in human cancer cell lines. This specific elevation of HIF-1alpha protein expression requires PI3K signaling. In the prostate carcinoma-derived cell lines PC-3 and DU145, insulin- and epidermal growth factor-induced expression of HIF-1alpha was inhibited by the PI3K-specific inhibitors LY294002 and wortmannin in a dose-dependent manner. HIF-1beta expression was not affected by these inhibitors. Introduction of wild-type PTEN into the PTEN-negative PC-3 cell line specifically inhibited the expression of HIF-1alpha but not that of HIF-1beta. In contrast to the HIF-1alpha protein, the level of HIF-1alpha mRNA was not significantly affected by PI3K signaling. Vascular endothelial growth factor reporter gene activity was induced by insulin in PC-3 cells and was inhibited by the PI3K inhibitor LY294002 and by the coexpression of a HIF-1 dominant negative construct. Vascular endothelial growth factor reporter gene activity was also inhibited by expression of a dominant negative PI3K construct and by the tumor suppressor PTEN.     

Design and synthesis of a series of novel pyrazolopyridines as HIF-1alpha prolyl hydroxylase inhibitors

Recently resolved X-ray crystal structure of HIF-1alpha prolyl hydroxylase was used to design and develop a novel series of pyrazolopyridines as potent HIF-1alpha prolyl hydroxylase inhibitors. The activity of these compounds was determined in a human EGLN-1 assay. Structure-based design aided in optimizing the potency of the initial lead (2, IC(50) of 11 microM) to a potent (11l, 190 nM) EGLN-1 inhibitor. Several of these analogs were potent VEGF inducers in a cell-based assay. These pyrazolopyridines were also effective in stabilizing HIF-1alpha.     

Lignans from Saururus chinensis inhibiting the transcription factor NF-kappaB

The sesquineolignans, saucerneol D and saucerneol E were isolated from the roots of Saururus chinensis together with four known lignans, manassantin A, manassantin B, (-)-saucerneol methyl ether, and (+)-saucernetin. Structure elucidation was based on the analysis of spectroscopic data and anti-inflammatory activity was studied using HeLa cells transfected with NF-kappaB reporter construct. All compounds except for (+)-saucernetin inhibited NF-kappaB dependent reporter gene expression with IC50 values of 2.5-16.9 microM.     

Insulin and hypoxia share common target genes but not the hypoxia-inducible factor-1alpha

Both hypoxia and insulin induce common target genes, including vascular endothelial growth factors and several glycolytic enzymes. However, these two signals eventually trigger quite different metabolic pathways. Hypoxia induces glycolysis, resulting in anaerobic ATP production, while insulin increases glycolysis for energy storage. Hypoxia-induced gene expression is mediated by the hypoxia-inducible factor-1 (HIF-1) that consists of HIF-1alpha and the aromatic hydrocarbon nuclear translocator (Arnt). Hypoxia-induced gene expression is initiated by the stabilization of the HIF-1alpha subunit. Here we investigated whether insulin-induced gene expression also requires stabilization of HIF-1alpha. Our results indicate that hypoxia but not insulin stabilizes HIF-1alpha protein levels, whereas both insulin- and hypoxia-induced gene expression require the presence of the Arnt protein. Insulin treatment fails to inactivate proline hydroxylation of HIF-1alpha, which triggers recruitment of the von Hippel-Lindau protein and oxygen-dependent degradation of HIF-1alpha. Insulin-induced gene expression is inhibited by the presence of the phosphoinositide (PI) 3-kinase inhibitor LY294002 and the dominant negative mutant of the p85 subunit of PI 3-kinase, whereas hypoxia-induced gene expression is not. Pyrrolidine dithiocarbamate, a scavenger of H2O2, reduces insulin-induced gene expression but not hypoxia-induced gene expression. Although both hypoxia and insulin induce the expression of common target genes through a hypoxia-responsive element- and Arnt-dependent mechanism, insulin cannot stabilize the HIF-1alpha protein. We believe that insulin activates other putative partner proteins for Arnt in PI 3-kinase- and H2O2-dependent pathways.