Green tea extract and (-)-epigallocatechin-3-gallate inhibit hypoxia- and serum-induced HIF-1alpha protein accumulation and VEGF expression in human cervical carcinoma and hepatoma cells

Green tea extract and its major component (-)-epigallocatechin-3-gallate (EGCG) exhibit antiangiogenic activities in various experimental tumor models. A growing body of evidence has established that hypoxia-inducible factor-1alpha (HIF-1alpha) and its downstream target, vascular endothelial growth factor (VEGF), play a critical role in tumor angiogenesis. In this study, we investigated the effect of green tea extract and EGCG on HIF-1alpha and VEGF expression in human cervical carcinoma (HeLa) and hepatoma (HepG2) cells. Our results showed that green tea extract and EGCG significantly inhibited hypoxia- and serum-induced HIF-1alpha protein accumulation in these cancer cells but had no effects on HIF-1alpha mRNA expression. Suppression of HIF-1alpha protein by green tea extract and EGCG also resulted in a drastic decrease in VEGF expression at both mRNA and protein levels. The mechanisms of green tea extract and EGCG inhibition of hypoxia-induced HIF-1alpha protein accumulation seem to involve the blocking of both phosphatidylinositol 3-kinase/Akt and extracellular signal-regulated kinase 1/2 signaling pathways and the enhancing of HIF-1alpha protein degradation through the proteasome system. In addition, green tea extract and EGCG inhibited serum-induced HIF-1alpha protein and VEGF expression by interfering with the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin signaling pathways, which play a crucial role in the protein translational machinery cascade. Functionally, green tea extract and EGCG abolished both chemoattractant- and hypoxia-stimulated HeLa cell migration. Our data suggested that HIF-1alpha/VEGF function as therapeutic target for green tea extract and EGCG in the context of cancer chemoprevention and anticancer therapy.     

Targeting HIF-1α abrogates PD-L1–mediated immune evasion in tumor microenvironment but promotes tolerance in normal tissues

A combination of anti–CTLA-4 plus anti–PD-1/PD-L1 is the most effective cancer immunotherapy but causes high incidence of immune-related adverse events (irAEs). Here we report that targeting of HIF-1α suppressed PD-L1 expression on tumor cells and tumor-infiltrating myeloid cells, but unexpectedly induced PD-L1 in normal tissues by an IFN-γ–dependent mechanism. Targeting the HIF-1α/PD-L1 axis in tumor cells reactivated tumor-infiltrating lymphocytes and caused tumor rejection. The HIF-1α inhibitor echinomycin potentiated the cancer immunotherapeutic effects of anti–CTLA-4 therapy, with efficacy comparable to that of anti–CTLA-4 plus anti–PD-1 antibodies. However, while anti–PD-1 exacerbated irAEs triggered by ipilimumab, echinomycin protected mice against irAEs by increasing PD-L1 levels in normal tissues. Our data suggest that targeting HIF-1α fortifies the immune tolerance function of the PD-1/PD-L1 checkpoint in normal tissues but abrogates its immune evasion function in the tumor microenvironment to achieve safer and more effective immunotherapy.     

Hypoxia-inducible factors and hypoxic cell death in tumour physiology

Hypoxic up-regulation of hypoxia-inducible factors (HIFs) during tumourigenesis presents an interesting paradox with respect to their role in tumour growth. Hypoxia-inducible factor 1 (HIF-1) plays a key role in the adaptive response to hypoxia, trans-activating many genes whose protein products are involved in pathways of angiogenesis, glucose metabolism and cell proliferation, thus facilitating tumour progression. However, it is also emerging that up-regulation of HIF-1 trans-activates anti-proliferative and pro-apoptotic genes (such as BNIP3, NIX and IGFBP3). This makes it unclear as to whether HIF-1 up-regulation provides a selective advantage or disadvantage to neoplastic progression under hypoxia. In addition, vagaries in the hypoxic microenvironment of the tumour such as pH changes, presence of reactive oxygen species and energy availability in the form of adenosine triphosphate (ATP), appear to influence the function of HIF-1 and up-regulated pathways and affect susceptibility to undergo hypoxic cell death. It is apparent that hypoxic cancer cells must be able to select against HIF-1 mediated cell death signals in order to survive and progress towards malignancy. Hypoxia-induced HIF-1 may in itself serve to select for increased malignancy by exerting pressure in the form of anti-proliferative signals that must be escaped. Understanding the mechanisms by which HIF-1 induces cell death and the manner in which the tumour cell can overcome such signals, is critical for our understanding of cancer progression and the development of effective therapeutics.     

Synthesis of 7-amino-6-halogeno-3-phenylquinoxaline-2-carbonitrile 1,4-dioxides: a way forward for targeting hypoxia and drug resistance of cancer cells

To establish a new approach for the synthesis of quinoxaline 1,4-dioxides as hypoxia-selective cytotoxic agents, an original multi-step preparation of derivatives possessing the diamine moiety at position 7 was evaluated. Herein, we present the synthesis of a series of novel 7-amino-6-halogeno-3-phenylquinoxaline-2-carbonitrile 1,4-dioxides 13a–h, 14a,b,g based on the regioselective Beirut reaction. Comparison of antitumor properties of derivatives possessing the diamine moiety at position 7 with structurally close congeners possessing the corresponding amino groups at position 6 revealed key differences in the cytotoxicity profiles and HIF-1α inhibition. All the synthesized 7-amino-6-halogeno derivatives 13a–h, 14a,b,g demonstrated significant cytotoxic activities against breast cancer cell lines (MCF7, MDA-MB-231) in normoxia and hypoxia with IC50 values ranging from 0.1 to 7.6 μM. Most of these novel derivatives can circumvent the multidrug resistance of tumor cells caused by P-glycoprotein over expression. The lead compounds 13a, 14a and 14b can suppress the expression of HIF-1α at low micromolar concentrations and induce apoptosis in breast cancer MCF7 cells. In addition, compound 14b effectively inhibits BCL2 and ERα expression in MCF7 cells. The current research opens a new direction for targeting hypoxia and drug resistance of cancer cells.

New water-soluble hypoxia activated 7-aminoquinoxaline 1,4-dioxides, prepared by the regioselective Beirut reaction, acted as HIF-1α suppressors and induced apoptosis in hypoxic and MDR cancer cells.     

Hypoxia enhances the expression of plasminogen activator inhibitor-1 in human lung cancer cells,EBC-1

Plasminogen activator inhibitor-1 (PAI-1) is one of the target genes of hypoxia inducible factor-1alpha (HIF-1alpha). Besides being an important physiological regulator of the fibrinolytic system PAI-1 is also involved in cancer invasiveness. HIF-1alpha is expressed in various types of pulmonary cells, but the relation of PAI-1 to HIF-1alpha under hypoxic condition in these cells are not fully elucidated. We, therefore, studied the effect of hypoxia on the expression of PAI-1 in a lung cancer cell line EBC-1. The expression of HIF-1alpha protein in EBC-1 cells was enhanced by hypoxia, and this was associated with increased secretion of PAI-1. Hypoxia did not affect the levels of HIF-1alpha mRNA but enhanced the PAI-1 mRNA. Pretreatment of the cells with MG132, which inhibits the proteasomal degradation of HIF-1alpha, increased the production of PAI-1 under both normoxia and hypoxia. We conclude that hypoxia induces PAI-1 expression, in EBC-1 cells, through the stabilization of HIF-1 complex and this may be related to cancer metastasis.     

Distinct subpopulations of FOXD1 stroma-derived cells regulate renal erythropoietin

Renal peritubular interstitial fibroblast-like cells are critical for adult erythropoiesis, as they are the main source of erythropoietin (EPO). Hypoxia-inducible factor 2 (HIF-2) controls EPO synthesis in the kidney and liver and is regulated by prolyl-4-hydroxylase domain (PHD) dioxygenases PHD1, PHD2, and PHD3, which function as cellular oxygen sensors. Renal interstitial cells with EPO-producing capacity are poorly characterized, and the role of the PHD/HIF-2 axis in renal EPO-producing cell (REPC) plasticity is unclear. Here we targeted the PHD/HIF-2/EPO axis in FOXD1 stroma-derived renal interstitial cells and examined the role of individual PHDs in REPC pool size regulation and renal EPO output. Renal interstitial cells with EPO-producing capacity were entirely derived from FOXD1-expressing stroma, and Phd2 inactivation alone induced renal Epo in a limited number of renal interstitial cells. EPO induction was submaximal, as hypoxia or pharmacologic PHD inhibition further increased the REPC fraction among Phd2^–/– renal interstitial cells. Moreover, Phd1 and Phd3 were differentially expressed in renal interstitium, and heterozygous deficiency for Phd1 and Phd3 increased REPC numbers in Phd2^–/– mice. We propose that FOXD1 lineage renal interstitial cells consist of distinct subpopulations that differ in their responsiveness to Phd2 inactivation and thus regulation of HIF-2 activity and EPO production under hypoxia or conditions of pharmacologic or genetic PHD inactivation.     

Apolipoprotein A-I mimetic peptides inhibit expression and activity of hypoxia-inducible factor-1α in human ovarian cancer cell lines and a mouse ovarian cancer model

Our previous results demonstrated that the apolipoprotein A-I (apoA-I) mimetic peptides L-4F and L-5F inhibit vascular endothelial growth factor production and tumor angiogenesis. The present study was designed to test whether apoA-I mimetic peptides inhibit the expression and activity of hypoxia-inducible factor-1α (HIF-1α), which plays a critical role in the production of angiogenic factors and angiogenesis. Immunohistochemistry staining was used to examine the expression of HIF-1α in tumor tissues. Immunoblotting, real-time polymerase chain reaction, immunofluorescence, and luciferase activity assays were used to determine the expression and activity of HIF-1α in human ovarian cancer cell lines. Immunohistochemistry staining demonstrated that L-4F treatment dramatically decreased HIF-1α expression in mouse ovarian tumor tissues. L-4F inhibited the expression and activity of HIF-1α induced by low oxygen concentration, cobalt chloride (CoCl(2), a hypoxia-mimic compound), lysophosphatidic acid, and insulin in two human ovarian cancer cell lines, OV2008 and CAOV-3. L-4F had no effect on the insulin-induced phosphorylation of Akt, but inhibited the activation of extracellular signal-regulated kinase and p70s6 kinase, leading to the inhibition of HIF-1α synthesis. Pretreatment with L-4F dramatically accelerated the proteasome-dependent protein degradation of HIF-1α in both insulin- and CoCl(2)-treated cells. The inhibitory effect of L-4F on HIF-1α expression is in part mediated by the reactive oxygen species-scavenging effect of L-4F. ApoA-I mimetic peptides inhibit the expression and activity of HIF-1α in both in vivo and in vitro models, suggesting the inhibition of HIF-1α may be a critical mechanism responsible for the suppression of tumor progression by apoA-I mimetic peptides.     

The mechanism between epithelial mesenchymal transition in breast cancer and hypoxia microenvironment

Hypoxia microenvironment widely exists in solid tumor tissues, which is mainly due to the rapid growth of cells within the tumor more than the speed of capillary in neoplasm, resulting in tumor tissue hypoxia. In hypoxia, hypoxia inducible factor 1 (HIF-1) is activated and regulate the expression of a series of hypoxia inducible genes, resulting in a series of hypoxia adaptation reaction. Researchs proved that, HIF-1 is closely related to the invasion, metastasis, prognosis of the tumor, and the expression of HIF-1 is higher in metastatic tissues compared with primary cancer tissues. In the evolution process of breast cancer, epithelial mesenchymal transition (EMT) define the characteristics of migration and invasion of breast cancer cells, which can also allow cancer cells to acquire the ability of self-renewing and stemness, so as to promote the generation of breast cancer stem cells. The incidence of EMT cancer stem cells are higher within the resistant to conventional treatment. This review focuses on breast cancer (stem cells), targeting the mechanism between hypoxia and EMT in tumor (stem cells), with the purpose of finding the new therapy to breast cancer.     

MTA1调控HIF-1α/VEGF通路作用于胰腺癌细胞增殖和迁移能力的研究

目的研究肿瘤转移相关蛋白1(MTA1)对胰腺癌细胞增殖、迁移和缺氧诱导因子(HIF-1α)/血管内皮生长因子(VEGF)信号通路的影响。方法采用Western blot检测MTA1在人胰腺癌组织、癌旁组织组织中的表达。采用酶联免疫吸附(ELISA)检测胰腺癌肿瘤细胞系PDAC-1培养上清液中MTA1浓度。然后加入不同浓度(5.0 ng/ml、10.0 ng/ml、15.0 ng/ml、20.0 ng/ml)的外源性MTA1处理胰腺癌肿瘤细胞系PDAC-1 48 h,MTT法检测细胞增殖。采用MTA1(20.0 ng/ml)和YC-1(50μmol/L)分别单独或联合作用于胰腺癌肿瘤细胞系PDAC-1 48 h,MTT法检测细胞增殖;采用划痕法检测细胞迁移能力;24 h时Western blot检测HIF-1α/VEGF信号通路中的关键蛋白HIF-1α和VEGF蛋白的水平。结果 MTA1在胰腺癌组织中的表达显著高于癌旁组织(P <0.05)。胰腺癌肿瘤细胞系PDAC-1自然生长条件下分泌的MTA1水平随着时间的增加在不断增大,48h后浓度为(0.041±0.003) ng/ml与后续研究中加入的外源MTA1浓度相比,可忽略不计。MTA1浓度在5.0~20.0 ng/ml时,从作用第12小时开始能够显著促进胰腺癌肿瘤细胞系PDAC-1的增殖(P <0.05)具有时间和剂量依赖效应。YC-1能够抑制胰腺癌肿瘤细胞系PDAC-1的增殖和迁移能力。MTA1能够促进HIF-1α和VEGF蛋白的表达,而YC-1能够降低MTA1对HIF-1α和VEGF蛋白表达的促进作用。结论 MTA1可以促进胰腺癌肿瘤细胞系PDAC-1的增殖和迁移,且具有时间和浓度依赖效应,其作用机制可能与HIF-1α/VEGF信号通路相关。     

缺氧诱导因子-1α低表达对肺癌A549细胞增殖及侵袭能力的影响研究

目的 研究缺氧诱导因子-1α(HIF-1α)低表达对肺癌A549细胞增殖、侵袭能力的影响,并探讨相关机制.方法 取A549细胞进行缺氧培养,用于模拟肿瘤内部低氧微环境,设置为缺氧处理组,取正常培养的A549细胞设为正常组,比较两组HIF-1α表达.取对数期A549细胞,进行HIF-1α-siRNA、HIF-1α-pLe...