Hypoxia inducible factor-1 mediates effects of insulin on pancreatic cancer cells and disturbs host energy homeostasis

Intratumoral hypoxia and paracrine insulin stimulate the expression of hypoxia inducible factor-1alpha (HIF-1alpha) in pancreatic cancer cells. In the present studies, we investigated whether insulin-induced HIF-1alpha expression is a prerequisite for insulin to induce other trophic effects in MiaPaCa2 human pancreatic cancer cells and whether inhibition of HIF-1alpha expression would decrease tumor glycolysis and improve host energy homeostasis. We found that hypoxia was a prerequisite for induction of HIF-1alpha mRNA expression by insulin in MiaPaCa2 cells. Under hypoxic conditions, insulin stimulated glycolysis, cell proliferation, and the secretion of vascular endothelial growth factor in regular MiaPaCa2 cells but not in a MiaPaCa2 variant (si-MiaPaCa2) that expressed specific short interfering RNA for HIF-1alpha and therefore lacked HIF-1alpha protein. This suggests that HIF-1alpha expression is required for insulin to induce other trophic effects. When si-MiaPaCa2 cells were transplanted into the pancreas of athymic mice, they were less tumorigenic and expressed less hexokinase than regular MiaPaCa2 cells. Body weight gain was attenuated in mice hosting tumors composed of regular MiaPaCa2 but not si-MiaPaCa2 cells. These results suggest that an interaction between insulin and HIF-1alpha helps sustain pancreatic cancer cells and disturbs host energy homeostasis.     

晚期缺血预适应促进低氧诱导因子的表达减轻肾脏缺血再灌注损伤

目的: 探讨晚期缺血预适应对肾脏缺血再灌注损伤的作用,以及低氧诱导因子1α(HIF-1α)在其中的作用。方法: 将雄性C57/BL6N小鼠随机分为3组:假手术组(sham)、缺血再灌注组(IR)和缺血预适应组(IPC)。采用夹闭双侧肾蒂30 min后恢复灌注的方法建立肾缺血再灌注小鼠模型;缺血预适应组4 d前给予肾脏15 min预缺血。观察缺血预处理对再灌注后不同时点血肌酐(Scr)、尿素氮(BUN)、肾组织形态学和细胞凋亡的影响。采用免疫组化及Western印迹法,分析HIF-1α在肾组织的表达;采用实时定量RT-PCR法,检测血管内皮生长因子(VEGF)和葡萄糖转运子-1(Glut-1)的mRNA表达。结果: 再灌注24 h后,IPC组小管间质损伤程度较IR组显著减轻,Scr、BUN水平以及小管上皮细胞凋亡明显下降。IPC组的HIF-1α核内表达显著高于IR组,且HIF-1下游靶基因VEGF和Glut-1的mRNA表达亦显著增加。结论: 晚期缺血预适应能够显著改善缺血再灌注后肾脏的形态和功能,这种保护作用可能与促进低氧诱导因子高表达有关。     

缺氧诱导因子-1α在结直肠腺癌中的表达及意义

目的　观察低氧培养条件下人结肠腺癌SW4 80细胞及人结直肠腺癌组织中缺氧诱导因子 1α(HIF 1α)mRNA、蛋白表达 ,探讨HIF 1α在结直肠腺癌中的表达及在肿瘤血管形成中的作用。方法　免疫组织化学链霉素抗生物素蛋白 过氧化物酶法 (SP法 )检测SW4 80细胞及结直肠腺瘤、腺癌组织中HIF 1α、血管内皮生长因子 (VEGF)蛋白表达 ;采用CD34标记血管内皮细胞计数微血管密度 (MVD)。用蛋白印迹法检测SW4 80细胞HIF 1α蛋白表达 ;原位杂交检测HIF 1αmRNA。结果　RT PCR结果显示 :低氧组SW4 80细胞HIF 1αmRNA表达显著升高 ,为常氧组的 2 33倍。低氧 genistein组HIF 1αmRNA表达为常氧组的 5 0 7%。原位杂交结果表明 :HIF 1αmRNA表达低氧组 (0 16 2 8± 0 0 0 85 )显著高于常氧组 (0 12 0 1± 0 0 0 38)和低氧 genistein组 (0 115 4± 0 0 0 5 6 ,P <0 0 5 )。免疫细胞化学染色显示 ,低氧组细胞HIF 1α、VEGF蛋白表达水平显著高于常氧组 (P <0 0 1,P <0 0 5 )和低氧 genistein组 (P <0 0 1,P <0 0 5 )。蛋白印迹结果显示 :低氧组HIF 1α蛋白表达显著高于常氧组 ,为常氧组 3 5 4倍。低氧 genistein组HIF 1α蛋白约为常氧组的 5 8 9%。结直肠腺瘤和腺癌HIF 1αmRNA阳性表达率分别为 38 9% (7/     

Hypoxia-inducible factor 1 and VEGF upregulate CXCR4 in glioblastoma: implications for angiogenesis and glioma cell invasion

Hypoxia and hypoxia-inducible factor-1 (HIF-1) play a critical role in glioblastoma multiforme (GBMs). CXCR4 is involved in angiogenesis and is upregulated by HIF-1alpha. CXCR4 is a chemokine receptor for stromal cell-derived factor-1 (SDF-1)alpha, also known as CXCL12. We hypothesized that CXCR4 would be upregulated by hypoxia in GBMs. First, we investigated the expression of HIF-1alpha and CXCR4 in GBMs. CXCR4 was consistently found colocalized with HIF-1alpha expression in pseudopalisading glioma cells around areas of necrosis. In addition, angiogenic tumor vessels were strongly positive for CXCR4. Next, we tested the in vitro effect of hypoxia and vascular endothelial growth factor (VEGF) on the expression of CXCR4 in glioma cell lines and in human brain microvascular endothelial cells (HBMECs). Exposure to hypoxia induced significant expression of CXCR4 and HIF-1alpha in glioma cells, whereas treatment with exogenous VEGF increased CXCR4 expression in HBMECs. We also transfected U87MG glioma cells with an HIF-1alpha construct and observed that CXCR4 was upregulated in these cells even in normoxic conditions. We then used a lentivirus-mediated shRNA expression vector directed against HIF-1alpha. When exposed to hypoxia, infected cells failed to show HIF-1alpha and CXCR4 upregulation. We performed migration assays under normoxic and hypoxic conditions in the presence or absence of AMD3100, a CXCR4 inhibitor. There was a significant increase in the migration of U87MG and LN308 glioma cells in hypoxic conditions, which was inhibited in the presence of AMD3100. These studies demonstrate the critical role played by hypoxia and CXCR4 in glioma cell migration. Based on these studies, we suggest that hypoxia regulates CXCR4 in GBMs at two levels. First, through HIF-1alpha in the pseudopalisading tumor cells themselves and, secondly, by the VEGF-stimulated angiogenic response in HBMECs. We believe this knowledge may lead to a potentially important two-pronged therapy against GBM progression using chemotherapy targeting CXCR4.     

Expression of hypoxia-related tissue factors in astrocytic gliomas. A multivariate survival study with emphasis upon carbonic anhydrase IX

Carbonic anhydrase IX (CAIX) is a transmembrane enzyme involved in the reversible metabolism of carbon dioxide to carbonic acid and, hence, in physiological pH regulation. It also participates in cellular differentiation and proliferation, its expression being absent in most normal tissues. It has been recently postulated that the hypoxia-inducible factor (HIF-1) pathway up-regulated by hypoxia accounts for CAIX overexpression in most human tumors. In the present study, we examined the expression of this enzyme in diffuse gliomas of astrocytic origin in relation to vascular endothelial growth factor (VEGF) and HIF-1alpha expression, proliferation rate (as assessed with Ki-67 antigen), microvessel morphology, and survival. Of 84 cases analyzed, 61 cases (72.6%) displayed strong membrane and/or cytoplasmic expression of CAIX and were grouped as positive. Immunoreactivity tended to have a perinecrotic distribution and increased in parallel with the extent of necrosis (P < .001) and histologic grade (P < .001). A positive correlation was also noted with HIF-1alpha and VEGF expression (P < .001), proliferation rate (P = .010), microvessel density (P = .004), and microvessel caliber parameters (P = .014-.038). In univariate survival analysis, increased CAIX expression was associated with shortened survival in the entire cohort (P < .0001), along with VEGF (P = .0205) and HIF-1alpha levels (P = .0190). Multivariate analysis selected the interaction model of CAIX, with grade and age as the only parameters independently affecting survival. CAIX expression was also the only significant parameter for the survival of patients with grades II/III. We conclude that CAIX may be used as a prognostic indicator in diffuse astrocytomas to refine the information provided by grade. Given the role of CAIX in the acidification of tumor environment and its up-regulation by hypoxia, it is thought that CAIX expression may be linked to resistance of tumor cells to radiotherapy by allowing them to acclimatize to a hypoxic and acidic microenvironment.     

Hypoxia promotes the proliferation of cervical carcinoma cells through stimulating the secretion of IL-8

To explore whether hypoxia and interleukin 8 (IL-8) regulate the viability and apoptosis of cervical carcinomas cells and the possible mechanism. We evaluated the expression of hypoxia inducible factor-1α (HIF-1α), IL-8 and its receptors (CXCR1 and CXCR2) in cervical cancer and cervicitis tissues by immunohistochemistry. Then the effects of hypoxia and IL-8 on the viability and apoptosis of HeLa and SiHa cells were detected by the SRB and apoptosis assays. Here we observed that the expression of HIF-1α, IL-8 and CXCR1 in cervical cancer tissues was significantly higher than that in cervicitis tissues. Hypoxic condition stimulated the secretion of IL-8 and the expression of CXCR1 and CXCR2 on HeLa and SiHa cells. Recombinant human IL-8 enhanced the viability and reduced the apoptosis in HeLa and SiHa cells. HeLa and SiHa cells cultured in 1% oxygen showed the increased viability and apoptosis, and the former effect could be partly reversed by anti-human IL-8 neutralizing antibody. This data suggested that IL-8 secreted by cervical carcinomas cells induced by hypoxia can stimulate the viability of cervical carcinomas cells in an autocrine dependent manner, and contribute to the pathogenesis of cervical cancer.     

Hypoxia-inducible factor 1 alpha is essential for hypoxic p27 induction in endometrioid endometrial carcinoma

Hypoxia-inducible factor 1alpha (HIF-1alpha) plays an essential role in the adaptive response of cells to hypoxia. The cyclin-dependent kinase inhibitor p27(Kip1) is highly expressed in the normal endometrium but is lost during endometrial carcinogenesis. However, in high-grade cancers, p27 re-expression is observed. We analysed the role of HIF-1alpha in hypoxia-induced expression of p27 in vitro and in vivo in endometrial cancer. Paraffin-embedded specimens from endometrioid endometrial carcinoma (n = 39) were stained immunohistochemically for HIF-1alpha, p27, and Ki67. HEC1B, an endometrial carcinoma cell line, was cultured under normoxic or hypoxic conditions in the presence or absence of transiently expressed short hairpin RNAs targeting HIF-1alpha. Protein expression of p27 and HIF-1alpha was assessed by western blotting. Immunohistochemical staining revealed perinecrotic HIF-1alpha expression in 67% of the cases and p27 staining centrally in the tumour islands, mostly around necrosis, in 46% of the cases. In 50% of the tumours with perinecrotic HIF-1alpha expression, p27 and HIF-1alpha perinecrotic/central co-localization was observed. In these tumour sections, hypoxia-associated p27 expression showed less proliferation around necrosis. Analysis of cultured endometrial carcinoma cells demonstrated that p27 protein expression is induced by hypoxia. This induction was abrogated by transient knockdown of HIF-1alpha using RNAi. Furthermore, hypoxia induced cell cycle arrest in HEC1B cells. We conclude that, in endometrioid endometrial carcinoma, p27 re-expression by hypoxia is HIF-1alpha-dependent and leads to cell cycle arrest. This may contribute to the survival of cancer cells in hypoxic parts of the tumour.     

Up-regulation of gene expression by hypoxia is mediated predominantly by hypoxia-inducible factor 1 (HIF-1)

The hypoxia-inducible factor 1 (HIF-1) plays a critical role in cellular responses to hypoxia. The aim of the present study was to evaluate which genes are induced by hypoxia, and whether this induction is mediated by HIF-1, by expression microarray analysis of wt and HIF-1alpha null mouse fibroblasts. Forty-five genes were up-regulated by hypoxia and 40 (89%) of these were regulated by HIF-1. Of the 114 genes down-regulated by hypoxia, 19 (17%) were HIF-1-dependent. All glycolytic enzymes were strongly up-regulated by hypoxia in a HIF-1-dependent manner. Genes already known to be related to hypoxia, such as glucose transporter 1, BNIP3, and hypoxia-induced gene 1, were induced. In addition, multiple new HIF-1-regulated genes were identified, including genes involved in metabolism (adenylate kinase 4, galactokinase), apoptosis (galectin-3 and gelsolin), and invasion (RhoA). Genes down-regulated by hypoxia were involved in cytoskeleton maintenance (Rho kinase), mRNA processing (heterogeneous nuclear ribonucleoprotein H1 and splicing factor), and DNA repair (REV3). Furthermore, seven cDNAs from genes with unknown function or expressed sequence tags (ESTs) were up-regulated and 27 such cDNAs were down-regulated. In conclusion, hypoxia causes down- rather than up-regulation of gene expression and HIF-1 seems to play a major role in the regulation of hypoxia-induced genes.