Rapid non-genomic signalling by 17β-oestradiol through c-Src involves mTOR-dependent expression of HIF-1α in breast cancer cells

Abstract

Background:Hypoxia-inducible factor 1 (HIF1) has been implicated in regulating many of the genes responsible for angiogenesis, erythropoiesis, glucose metabolism and cancer pathogenesis. In this study, we demonstrate that exposure of human breast cancer lines to 17β-oestradiol (E2) rapidly induced the expression of HIF-1α, the regulated subunit of HIF1, in normoxic condition. Hypoxia-inducible factor-1α is normally degraded in normoxia through ubiquitination-mediated proteolysis, whereas hypoxia modulates HIF-1α level by inhibiting ubiquitination-mediated degradation.Methods:Oestradiol-induced accumulation of HIF-1α in breast cancer lines was detected by western blot analysis and its promoter activity was measured by HIF1 reporter assay. Molecular signalling of oestradiol-mediated HIF-1α expression was studied using specific pharmacological inhibitors and small interference RNA by co-immunoprecipitation and western blotting analysis.Results:Oestradiol has been observed to rapidly activate the nongenomic signalling cascade leading to HIF-1α protein synthesis. The results define a signalling pathway in breast cancer cells whereby oestradiol induces a rapid protein–protein interaction of ERα-c-Src-PI3K, resulting in the activation of PI3K/AKT pathway leading to mammalian target of rapamycin (mTOR) phosphorylation. The mTOR then stimulates translation by phosphorylating p70 S6 kinase and 4EB-P1, modulating HIF-1α protein synthesis. Oestradiol-stimulated HIF-1α activity was inhibited by either siRNA or pharmacological inhibitors to ERα, c-Src, PI3K and mTOR, providing a mechanism for the modulation of HIF-1α protein synthesis.Conclusion:These results show oestradiol-induced expression of HIF-1α, downstream of the ERα/c-Src/PI3K/AKT/mTOR pathway in human breast cancer cells.

Resveratrol Suppresses Cancer Cell Glucose Uptake by Targeting Reactive Oxygen Species–Mediated Hypoxia-Inducible Factor-1α Activation

“…HIF-1a induction in malignant cells is closely linked to PI3K/Akt and mTOR signaling (27)(28)(29), which are frequently involved in cancer cell proliferation, metabolism, and survival (30). In breast cancer cells, estrogen-induced HIF-1a accumulation was shown to occur through the PI3K/Akt pathway leading to mTOR phosphorylation (31). In our results, resveratrol reduced activated Akt levels in LLC cells in a manner that preceded suppression of HIF-1a accumulation.…”

Membrane-Initiated Estradiol Signaling of Epithelial-Mesenchymal Transition-Associated Mechanisms Through Regulation of Tight Junctions in Human Breast Cancer Cells

“…Despite the classical mode of action of estradiol, it has been implicated in a rapid non-genomic signaling cascade involving ER interaction with the non-receptor tyrosine kinase c-Src, which activates the phosphatidylinositol-3 kinase/Akt pathway [9]. It has also been reported that c-Src is an important adapter protein between extranuclear ERs and HER2, allowing for cross talk pathways in cancer cell lines [10].…”

Reprogramming of non-genomic estrogen signaling by the stemness factor SOX2 enhances the tumor-initiating capacity of breast cancer cells

“…Indeed, E 2 and growth factors/growth factor receptors can result in phosphorylation of ERα at Ser118 by MAPK, thus linking rapid, membrane-initiated, non-genomic ERα responses with later bona fide ERα genomic actions. [14][15][16][17][18][19] Because the genomic and non-genomic actions of ERα are complementary and even synergistic via crossregulatory interactions that are mediated through cross-talk with other growth factor and cellular signal transduction pathways, the fact that the SOX2-driven reprogramming of breast CSC-like states was involved in the derepression of the phospho-Ser118-ERα-activating insulin receptor/mTOR pathway 4 strongly suggested that the E 2 -hypersensitive phenotype of the SOX2-overexpressing MCF-7/ Rep xenotumors might be explained in terms of increased phospho-Ser118-ERα. When testing the hypothesis that phosphoSer118-ERα levels might correspond to enhanced estrogenic responses and tumorinitiating ability in SOX2-overexpressing MCF-7/Rep cells, we first observed that the basal protein expression of ERα, which was diffusely distributed throughout the cytoplasm and nucleus, was increased in SOX2-overexpressing CSC-like MCF-7/ Rep cells compared with MCF-7 parental cells (Fig.…”