Thymoquinone affects hypoxia-inducible factor-1α expression in pancreatic cancer cells via HSP90 and PI3K/AKT/mTOR pathways.

Pancreatic cancer (PC) is associated with some of the worst prognoses of all major cancers. Thymoquinone (TQ) has a long history in traditional medical practice and is known for its anti-cancer, anti-inflammatory, anti-fibrosis and antioxidant pharmacological activities. Recent studies on hypoxia-inducible factor-1α (HIF-1α) and PC have shown that HIF-1α affects the occurrence and development of PC in many aspects. In addition, TQ could inhibit the development of renal cancer by decreasing the expression of HIF-1α. Therefore, we speculate whether TQ affects HIF-1α expression in PC cells and explore the mechanism. To elucidate the effect of TQ in PC cells and the regulatory mechanism of HIF-1α expression. Cell counting kit-8 assay, Transwell assay and flow cytometry were performed to detect the effects of TQ on the proliferative activity, migration and invasion ability and apoptosis of PANC-1 cells and normal pancreatic duct epithelial (hTERT-HPNE) cells. Quantitative real-time polymerase chain reaction and western blot assay were performed to detect the expression of HIF-1α mRNA and protein in PC cells. The effects of TQ on the HIF-1α protein initial expression pathway and ubiquitination degradation in PANC-1 cells were examined by western blot assay and co-immunoprecipitation. TQ significantly inhibited proliferative activity, migration, and invasion ability and promoted apoptosis of PANC-1 cells; however, no significant effects on hTERT-HPNE cells were observed. TQ significantly reduced the mRNA and protein expression levels of HIF-1α in PANC-1, AsPC-1, and BxPC-3 cells. TQ significantly inhibited the expression of the HIF-1α initial expression pathway (PI3K/AKT/mTOR) related proteins, and promoted the ubiquitination degradation of the HIF-1α protein in PANC-1 cells. TQ had no effect on the hydroxylation and von Hippel Lindau protein mediated ubiquitination degradation of the HIF-1α protein but affected the stability of the HIF-1α protein by inhibiting the interaction between HIF-1α and HSP90, thus promoting its ubiquitination degradation. The regulatory mechanism of TQ on HIF-1α protein expression in PC cells was mainly to promote the ubiquitination degradation of the HIF-1α protein by inhibiting the interaction between HIF-1α and HSP90; Secondly, TQ reduced the initial expression of HIF-1α protein by inhibiting the PI3K/AKT/mTOR pathway.

Zhao ZX ，Li S ，Liu LX 《-》

A group of novel HIF-1α inhibitors, glyceollins, blocks HIF-1α synthesis and decreases its stability via inhibition of the PI3K/AKT/mTOR pathway and Hsp90 binding.

Glyceollins, a group of phytoalexins isolated from soybean, are known to exhibit anticancer, antiestrogenic, and antiangiogenic activities. However, whether glyceollins regulate tumor growth through regulation of hypoxia-inducible factor (HIF)-1α has not been investigated. We determined whether and how glyceollins regulate the synthesis and stability of HIF-1α. Quantitative real-time PCR revealed that glyceollins inhibited the expression of HIF-1-induced genes such as vascular endothelial growth factor (VEGF) in cancer cells. Enzyme-linked immunosorbent assay and reporter luciferase assay showed that glyceollins decreased VEGF secretion and its promoter activity, respectively. Treatment of various cancer cells with 0.5-100 µM glyceollins under hypoxic conditions reduced the expression of HIF-1α. Glyceollins blocked translation of HIF-1α by inhibiting the PI3K/AKT/mTOR pathway under hypoxic conditions. Glyceollins decreased the stability of HIF-1α after treatment with cycloheximide, a protein synthesis inhibitor, and increased the ubiquitination of HIF-1α after treatment with MG132, a proteasome inhibitor. Glyceollins blocked the interaction of Hsp90 with HIF-1α, as shown by immunoprecipitation assay. Chemical binding of Hsp90 with glyceollins, as confirmed by computational docking analysis, was stronger than that with geldanamycin at the HSP90 ATP-binding pocket. We found that glyceollins decreased microvessel density, as well as expression of phosphorylated AKT/mTOR and the Hsp90 client protein CDK4, in solid tumor tissues. Glyceollins potently inhibited HIF-1α synthesis and decreased its stability by blocking the PI3K/AKT/mTOR pathway and HSP90 binding activity, respectively. These results may provide new perspectives into potential therapeutic application of glyceollins for the prevention and treatment of hypervascularized diseases and into the mechanism of their anticancer activity.

Lee SH ，Jee JG ，Bae JS ，Liu KH ，Lee YM ... -  《-》

PI3K/Akt is required for heat shock proteins to protect hypoxia-inducible factor 1alpha from pVHL-independent degradation.

Zhou J ，Schmid T ，Frank R ，Brüne B ... -  《JOURNAL OF BIOLOGICAL CHEMISTRY》

Inflammatory interferon activates HIF-1α-mediated epithelial-to-mesenchymal transition via PI3K/AKT/mTOR pathway.

Yeh YH ，Hsiao HF ，Yeh YC ，Chen TW ，Li TK ... -  《JOURNAL OF EXPERIMENTAL & CLINICAL CANCER RESEARCH》

Knockdown of KLF5 suppresses hypoxia-induced resistance to cisplatin in NSCLC cells by regulating HIF-1α-dependent glycolysis through inactivation of the PI3K/Akt/mTOR pathway.

Gong T ，Cui L ，Wang H ，Wang H ，Han N ... -  《Journal of Translational Medicine》