GPER-mediated stabilization of HIF-1α contributes to upregulated aerobic glycolysis in tamoxifen-resistant cells.

Tamoxifen is a first-line therapeutic drug for oestrogen-receptor positive breast cancer; however, like other therapeutics, its clinical use is limited by acquired resistance. Tamoxifen-resistant cells have demonstrated enhanced aerobic glycolysis; however, the mechanisms underlying this upregulation remain unclear. Here, we demonstrated that G-protein coupled oestrogen receptor (GPER) was involved in the upregulation of aerobic glycolysis via induction of hypoxia-inducible factor-1α (HIF-1α) expression and transcriptional activity in tamoxifen-resistant cells. Additionally, GPER stabilized HIF-1α through inhibiting its hydroxylation and ubiquitin-mediated degradation, which were associated with upregulation of C-terminal hydrolase-L1 (UCH-L1), downregulation of prolyl hydroxylase 2 (PHD2) and von Hippel-Lindau tumour suppressor protein (pVHL), induction of HIF-1α/UCH-L1 interaction, and suppression of HIF-1α/PHD2-pVHL association. The GPER/HIF-1α axis was functionally responsible for regulating tamoxifen sensitivity both in vitro and in vivo. Moreover, there was a positive correlation between GPER and HIF-1α expression in clinical breast cancer tissues, and high levels of GPER combined with nuclear HIF-1α indicated poor overall survival. High levels of the GPER/HIF-1α axis were also correlated with shorter relapse-free survival in patients receiving tamoxifen. Hence, our findings support a critical role of GPER/HIF-1α axis in the regulation of aerobic glycolysis in tamoxifen-resistant cells, offering a potential therapeutic target for tamoxifen-resistant breast cancer.

Baicalein resensitizes tamoxifen-resistant breast cancer cells by reducing aerobic glycolysis and reversing mitochondrial dysfunction via inhibition of hypoxia-inducible factor-1α.

Drug resistance is a major hurdle for the effectiveness of tamoxifen (TAM) to provide clinical benefit. Therefore, it is essential to identify a sensitizer that could be used to improve TAM efficacy in treating TAM-resistant breast cancer. Here, we investigated the ability of baicalein to reverse TAM resistance. We found that baicalein increased the efficacy of TAM in inhibiting proliferation and inducing apoptosis of TAM-resistant cells. It also enhanced the TAM-induced growth reduction of resistant cells from NOD/SCID mouse mammary fat pads, without causing obvious systemic toxicity. Analyses using the CellMiner tool and the Kaplan-Meier plotter database showed that HIF-1α expression was inversely correlated with TAM therapeutic response in NCI-60 cancer cells and breast cancer patients. HIF-1α expression was increased in TAM-resistant cells due to an increase in mRNA levels and reduced ubiquitin-mediated degradation. Baicalein reduced HIF-1α expression by promoting its interaction with PHD2 and pVHL, thus facilitating ubiquitin ligase-mediated proteasomal degradation and thereby suppressing the nuclear translocation, binding to the hypoxia-response element, and transcriptional activity of HIF-1α. As a result, baicalein downregulated aerobic glycolysis by restricting glucose uptake, lactate production, ATP generation, lactate/pyruvate ratio and expression of HIF-1α-targeted glycolytic genes, thereby enhancing the antiproliferative efficacy of TAM. Furthermore, baicalein interfered with HIF-1α inhibition of mitochondrial biosynthesis, which increased mitochondrial DNA content and mitochondrial numbers, restored the generation of reactive oxygen species in mitochondria, and thus enhanced the TAM-induced mitochondrial apoptotic pathway. The HIF-1α stabilizer dimethyloxallyl glycine prevented the baicalein-induced downregulation of glycolysis and mitochondrial biosynthesis and reduced the effects of baicalein on reversing TAM resistance. Our results indicate that baicalein is a promising candidate to help overcome TAM resistance by sensitizing resistant cells to TAM-induced growth inhibition and apoptosis. The mechanism underlying the effects of baicalein consists of inhibition of HIF-1α-mediated aerobic glycolysis and mitochondrial dysfunction.

Plasma interleukin-21 levels and genetic variants are associated with susceptibility to rheumatoid arthritis.

BACKGROUND: Rheumatoid Arthritis (RA) is a chronic inflammatory condition characterized by autoantibodies development and an elevated spectrum of pro-inflammatory cytokines. Previous reports highlighted a relationship between IL-21and the pathogenesis of RA. Although elevated IL-21 levels have been reported in RA patients, the association of common IL-21 genetic variants with a predisposition to RA development in the Chinese population lacks. MATERIALS AND METHODS: Five hundred and fourteen Chinese subjects (healthy controls: 303 and rheumatoid arthritis patients: 211) were enrolled in the study. Clinical data of patients were collected from medical records, and patients were treated as per the guidelines. Common single nucleotide polymorphisms in the IL-21 gene (rs907715, rs2221903, rs2055979 and rs6822844) were genotyped by TaqMan SNPs genotyping method. IL-21 level in plasma of RA patients and healthy subjects was measured by ELISA. RESULTS: The plasma level of IL-21 was significantly higher in subjects with rheumatoid arthritis relative to healthy controls (p < 0.0001). A positive correlation was observed between IL-21 level and DAS28 score, indicating the association of the cytokine with the worsening of the disease (Spearman r = 0.61, p < 0.0001). The prevalence of AA genotype (rs2055979) was significantly higher in RA subjects than in the controls (p < 0.0001, χ2 = 34.73, OR = 4.34, 95% CI = 2.623 to 7.219). Furthermore, elevated plasma IL-21 was observed in the rs2055979-AA genotype compared to CC type (p < 0.0001). CONCLUSION: IL-21 plays a crucial function in rheumatoid arthritis pathogenesis. IL-21 rs2055979 polymorphism is associated with IL-21 plasma levels and is predisposed to RA development in the Chinese population.

Oxymatrine reverses epithelial-mesenchymal transition in breast cancer cells by depressing αâ ¤ß3 integrin/FAK/PI3K/Akt signaling activation.

PURPOSE: Oxymatrine, an alkaloid extracted from the Chinese herb Sophora flavescens Aiton, possesses anti-inflammatory, anti-immune, anti-hepatic fibrosis, and anti-cancer properties. However, the effects of oxymatrine on epithelial-mesenchymal transition (EMT) of breast cancer cells are still unclear. AIM: The present study was performed to investigate whether oxymatrine reverses EMT in breast cancer cells and to explore the underlying molecular mechanisms. MATERIALS AND METHODS: MTT assay was performed to evaluate cell viability. Wound-healing assay and transwell chamber assay were used to assess cell migration and invasion, respectively. Immunofluorescence and Western blot were used to study the expression of EMT-related molecules and αⅤß3 integrin/focal adhesion kinase (FAK)/phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling transduction. Fibronectin, a physiologic ligand of αⅤß3 integrin, was used to stimulate αⅤß3 integrin signaling. RESULTS: Our results demonstrated that oxymatrine effectively suppressed the viability of MDA-MB-231 and 4T1 breast cancer cells, and oxymatrine showed less cytotoxicity on normal breast mammary epithelial MCF-10A cells. In addition, oxymatrine reversed EMT in the MDA-MB-231 and 4T1 cells at nontoxic concentrations. Oxymatrine significantly inhibited cell migration and invasion, downregulated the expression of N-cadherin, vimentin, and Snail in MDA-MB-231 and 4T1 cells, but upregulated the expression of E-cadherin in 4T1 cells. The mechanism revealed that oxymatrine decreased the expression of αⅤ and ß3 integrin and their co-localization. It also inhibited αⅤß3 integrin downstream activation by suppressing the phosphorylation of FAK, PI3K, and Akt. Furthermore, oxymatrine prevented fibronectin-induced EMT and αⅤß3 integrin/FAK/PI3K/Akt signaling activation. CONCLUSION: Our results revealed that oxymatrine effectively reversed EMT in breast cancer cells by depressing αⅤß3 integrin/FAK/PI3K/Akt signaling. Thus, oxymatrine could be a potential therapeutic candidate with anti-metastatic potential for the treatment of breast cancer.

Gallic acid targets acute myeloid leukemia via Akt/mTOR-dependent mitochondrial respiration inhibition.

Gallic acid is one of the many phenolic acids that can be found in dietary substances and traditional medicine herbs. The anti-cancer activities of gallic acid have been shown in various cancers but its underlying molecular mechanisms are not well understood. In this study, we show Akt/mammalian target of rapamycin (mTOR)-dependent inhibition of mitochondrial respiration as a mechanism of gallic acid's action in acute myeloid leukemia (AML). Gallic acid significantly induces apoptosis of AML cell lines, primary mononuclear cells (MNC) and CD34 stem/progenitors isolated form AML patients via caspase-dependent pathway. It also significantly enhances two standard AML chemotherapeutic agents' efficacy in vitro cell culture system and in vivo xenograft model. Gallic acid inhibits dose- and time-dependent mitochondrial respiration, leading to decreased ATP production and oxidative stress. Overexpression of constitutively active Akt restores gallic acid-mediated inhibition of mTOR signaling, mitochondrial dysfunction, energy crisis and apoptosis. Our results demonstrate that mitochondrial respiration inhibition by gallic acid is a consequence of Akt/mTOR signaling suppression. Our findings suggest that combination therapy with gallic acid may enhance antileukemic efficacy of standard chemotherapeutic agents in AML.