HIF-1α基因干扰对大鼠CBRH-7919肝癌细胞HIF-1α与VEGF表达影响的研究

目的:探讨沉默缺氧诱导因子-1α(HIF-1α)对肝癌细胞在缺氧状态下表达HIF-1α及血管内皮生长因子(VEGF)的影响.方法:选用大鼠CBRH-7919肝癌细胞株作为研究对象,利用氯化钴(CoCl2)模拟缺氧状态,构建3组特异性较强的HIF-1α siRNA表达载体,采用小分子RNA干扰技术沉默细胞HIF-1α的基因表达,分别利用real time RT-PCR和蛋白质印迹法检测肝癌细胞HIF-1α和VEGF在mRNA及蛋白水平的表达变化.结果:在不同浓度CoCl2模拟缺氧条件下,随着CoCl2浓度的增高及时间的推移,肝癌细胞HIF-1α和VEGF的表达(mRNA及蛋白水平)较常氧对照组(0 μmol/L CoCl2)显著增多,差异均有统计学意义,P＜0.05.应用3组不同HIF-1α和siRNA表达载体转染缺氧条件下的肝癌细胞后,细胞的HIF-1α和VEGF的基因(mRNA)表达量与未转染HIF-1α siRNA表达载体对照组相比较明显减少,同步检测两者的蛋白表达亦明显减少,与对照组差异均有统计学意义,P＜0.05.结论:缺氧可以诱导肝癌细胞HIF-1α和VEGF的表达,siRNA沉默HIF-1α能显著抑制缺氧状态下诱导的VEGF表达.     

HIF-1α对胶质瘤U251细胞增殖及侵袭的影响

目的 探讨氯化钴(CoCl2)模拟化学缺氧复氧中缺氧诱导因子-1α(HIF-1α)蛋白的表达及其对人胶质瘤U251细胞增殖及侵袭的影响.方法 在培养基中加入和去除CoCl2模拟化学缺氧和缺氧复氧,采用免疫印迹法(Western blot)检测CoCl2与HIF-1α蛋白表达关系;通过MTT、过河实验、黏附试验分别检测细胞侵袭、迁移运动能力和黏附能力.结果 人胶质瘤U251细胞中存在HIF-1α蛋白表达;在CoCl2模拟缺氧的时-效关系实验中,100μmol/L CoCl2刺激细胞6h、12h、24h时HIF- 1α蛋白呈递增(分别 为1.024±0.03、2.35±0.04、2.82±0.12)(P<0.05),24h达高峰,48h明显下降(1.82±0.05).同时,在量-效关系实验中,CoCl2 50μmol/L、100μmol/L和150μmol/L刺激细胞24h时HIF-1α蛋白呈递增(分别为1.78±0.03、1.81±0.03、2.12±0.12)(P<0.05);MTT发现CoCl2诱导的缺氧对细胞增殖起抑制作用;过河实验发现缺氧24h复氧24h后细胞的迁移运动能力增加;细胞黏附实验发现缺氧24h复氧24h后细胞的黏附力增加.结论 CoCl2能诱导人胶质瘤U251细胞HIF-1α蛋白过度表达,而且存在一定的时-效关系;经CoCl2诱导的缺氧后复氧,肿瘤细胞增殖能力下降,细胞的迁移运动能力和黏附能力增加.     

JAK2/STAT3信号通路对A549细胞株中HIF-1α、VEGF蛋白表达的影响

目的:研究人肺腺癌细胞A549细胞中JAK2/STAT3信号通路对HIF-1α、VEGF蛋白表达的影响.方法:AG490处理在氧含量正常及缺氧条件下(CoCl2 200μmol/L)48h后Western blot法测定A549细胞中HIF-1α、VEGF蛋白表达变化(分组为对照组、AG490 50μmol/L、AG490 100μmol/L、CoCl2、CoCl2+AG49050μmol/L和CoCl2+AG490 100μmol/L组).IL-6 (3.85nmol/L)处理A549细胞24h后,检测细胞中STAT3、p-STAT3、HIF-1α、VEGF蛋白表达变化(分组为对照组,IL-6组).结果:JAK2特异性抑制剂AG490作用48h后,相对于对照组AG490能够下调HIF-1α、VEGF的蛋白表达,且呈浓度依赖性;随浓度的升高,抑制作用更明显.缺氧条件下(CoCl2200μmol/L)能够上调HIF-1α、VEGF的蛋白表达.AG490也能够下调CoCl2诱导的HIF-1α、VEGF的蛋白表达,且呈浓度依赖性,随浓度的升高,抑制作用更显著.IL-6能够上调HIF-1α、VEGF的蛋白表达.结论:在人肺腺癌细胞A549细胞中,缺氧可上调HIF-1α和VEGF蛋白表达.JAK2/STAT3信号通路对HIF-1α和VEGF蛋白的表达具有调节作用.     

HIF-1α对胶质瘤U251细胞增殖及侵袭的影响

目的：探讨氯化钴（CoCl2）模拟化学缺氧复氧中缺氧诱导因子-1α（HIF-1α）蛋白的表达及其对人胶质瘤U251细胞增殖及侵袭的影响。方法：在培养基中加入和去除CoCl2模拟化学缺氧和缺氧复氧,采用免疫印迹法（Western blot）检测CoCl2与HIF-1α蛋白表达关系;通过MTT、过河实验、黏附试验分别检测细胞侵袭、迁移运动能力和黏附能力。结果：人胶质瘤U251细胞中存在HIF-1α蛋白表达;在CoCl2模拟缺氧的时-效关系实验中,100μmol/L CoCl2刺激细胞6h、12h、24h时HIF-1α蛋白呈递增（分别为1.024±0.03、2.35±0.04、2.82±0.12）（P〈0.05）,24h达高峰,48h明显下降（1.82±0.05）。同时,在量-效关系实验中,CoCl250μmol/L、100μmol/L和150μmol/L刺激细胞24h时HIF-1α蛋白呈递增（分别为1.78±0.03、1.81±0.03、2.12±0.12）（P〈0.05）;MTT发现CoCl2诱导的缺氧对细胞增殖起抑制作用;过河实验发现缺氧24h复氧24h后细胞的迁移运动能力增加;细胞黏附实验发现缺氧24h复氧24h后细胞的黏附力增加。结论：CoCl2能诱导人胶质瘤U251细胞HIF-1α蛋白过度表达,而且存在一定的时-效关系;经CoCl2诱导的缺氧后复氧,肿瘤细胞增殖能力下降,细胞的迁移运动能力和黏附能力增加。     

HIF-1的功能结构及其基因调控

HIF-1是氧平衡调控的转录因子，在肿瘤细胞缺氧适应过程中起着中枢调节作用，其对下游基因的表达调控广泛影响着肿瘤细胞的糖代谢、增殖、凋亡和肿瘤的血管形成．使缺氧的组织细胞能保持氧稳态以耐受缺氧状态。因此，探讨HIF-1的功能结构和活性表达及其对下游基因的表达调控，将HIF-1及其下游基因为靶点，有望成为抗肿瘤治疗的有效手段。     

siRNA 沉默HIF-1α在缺氧状态下对食管鳞癌细胞VEGF表达的影响

 目的 观察体外乏氧培养条件下食管鳞癌细胞系EC9706中HIF-1α和VEGF的表达，探讨HIF-1α在低氧条件下对食管鳞癌血管生成的调控作用。方法 CoCl2化学缺氧法模拟肿瘤缺氧环境，RT-PCR、免疫组化法和免疫印迹法分别检测缺氧状态下HIF-1α和VEGF在mRNA和蛋白水平的表达。采用化学合成小干扰RNA（siRNA）介导的RNA干扰技术（RNAi）用siRNA转染EC9706细胞。观察转染后HIF-1α沉默效果。结果 低氧条件下，EC9706细胞HIF-1amRNA水平稳定，蛋白表达显著升高，而VEGFmRNA和蛋白的表达均显著升高。SiRNA转染EC9706后能够显著下调HIF-1α的基因表达，同时VEGF基因的表达也受到明显抑制。结论 缺氧促使EC9706细胞HIF-1α在蛋白水平表达升高，并通过转录激活VEGF的机制调控食管鳞癌血管生成。     

缺氧条件下YC-1对人胰腺癌细胞VEGF和GPI基因的抑制效应

目的探讨缺氧条件下3-(5’-hydroxymethyl-2’-furyl)-1-benzylindazole(YC-1)对人胰腺癌细胞血管内皮生长因子(VEGF)和磷酸葡萄糖异构酶(GPI)基因的调控作用及其机制。方法缺氧条件下体外培养胰腺癌PC-3细胞株,免疫细胞化学染色法检测常氧和缺氧条件下缺氧诱导因子- 1α(HIF-1α)的表达。半定量RT-PCR检测YC-1对PC-3细胞VEGF、GPI、HIF-1αmRNA表达的调节作用。Western blot检测YC-1对PC-3细胞HIF-1α蛋白表达的调节作用。MTT法检测YC-1对缺氧PC-3细胞恶性增殖的影响。结果缺氧条件下,HIF-1α主要表达于PC-3细胞胞核内。随着YC-1浓度升高,VEGF和GPI mRNA表达、HIF-1α蛋白表达逐渐受抑,并呈明显的剂量依赖性;实验组HIF- 1αmRNA均呈强表达,其表达水平不随YC-1作用浓度的升高而降低。缺氧条件下,实验组细胞增殖抑制率均增高,100μmol／L YC-1组细胞增殖抑制率达73．28%±2．01％。结论缺氧状态下,YC-1抑制人胰腺癌PC-3细胞VEGF和GPI基因转录与其抑制HIF-1α蛋白的表达有关,YC-1能够抑制PC-3细胞生长和增殖。     

缺氧调控端粒酶活性及抑制鼻咽癌细胞增殖实验研究

目的探讨缺氧及siRNA沉默缺氧诱导因子-1α(hypoxia inducible factor-1α,HIF-1α)后对鼻咽癌细胞中端粒酶催化亚单位(telomerase catalytic subunit,hTERT)、细胞周期和化疗耐药的影响。方法采用三气培养箱对鼻咽癌细胞5-8F和CNE2进行缺氧处理(1%O2),蛋白质印迹法检测不同乏氧时相(0~72h)HIF-1α和hTERT蛋白的表达。将HIF-1α基因特异性siRNA分别转染鼻咽癌细胞株5-8F和CNE2,筛选出沉默效率最高的siRNA,实验分为未处理组(常氧)、未处理组(缺氧)、Negative-siRNA(缺氧)和HIF-1α-siRNA(缺氧),荧光定量PCR及蛋白质印迹检测瞬时转染后hTERT及HIF-1α的表达。流式细胞术(flow cytometry,FCM)分析缺氧或沉默HIF-1α后对细胞周期的影响。MTT法检测缺氧或沉默HIF-1α后,鼻咽癌细胞对顺铂(DDP)和5-氟尿嘧啶(5-FU)的化疗敏感性。结果缺氧处理0~72h后鼻咽癌5-8F细胞HIF-1α(F=37.147,P<0.001)和hTERT(F=70.069,P<0.001)蛋白的表达上调,差异有统计学意义。HIF-1α-siRNA对5-8F细胞瞬时转染率>98%。HIF-1α-siRNA组hTERT mRNA表达量为0.37±0.05,显著低于未处理组(缺氧)的1.00±0.00和Negative-siRNA(缺氧)的0.95±0.01,F=360.339,P<0.001;hTERT蛋白表达量为(0.27±0.05),显著低于未处理组(缺氧)0.54±0.00和Negative-siRNA组(缺氧)0.53±0.01,F=24.010,P<0.001。未处理组(缺氧)G0/G1期细胞比例明显增加(45.63±2.01)%,显著高于未处理组(常氧)的(26.75±1.28)%,P<0.001。5-8F细胞未处理组(常氧)对5-FU的IC50分别为(17.30±3.31)μg/mL,未处理组(缺氧)为(32.04±12.75)μg/mL,Negative-siRNA组为(33.90±0.87)μg/mL,HIF-1α-siRNA组为(13.72±2.36)μg/mL,F=3.704,P<0.001。5-8F细胞缺氧组对DDP的化疗敏感性也降低,沉默HIF-1α后,5-8F细胞对DDP的化疗敏感性明显提高。除细胞周期外,CNE2与5-8F的结果均一致。结论缺氧促使鼻咽癌细胞发生G1/S阻滞及化疗耐药,可能与上调hTERT表达,进而上调端粒酶活性有关;沉默HIF-1α显著逆转缺氧诱导的肿瘤耐药并下调端粒酶活性。     

HIF-1α对人卵巢癌细胞生物学行为的影响

背景与目的:HIF-1α是一个在缺氧状态下重要的转录调节因子,控制调节各种由缺氧引起的相关基因表达,参与肿瘤的恶化、浸润和转移,在肿瘤领域已成为研究热点。本文主要研究CoCl2模拟化学缺氧复氧中HIF-1α的表达,及其对人卵巢癌HO-8910PM细胞株生物学行为的影响。方法:在培养基中加入和去除CoCl2模拟化学缺氧和缺氧复氧,采用逆转录-聚合酶链反应(RT-PCR)检测CoCl2与HIF-1α的mRNA转录的量-效和时-效关系;通过MTT、Boyden小室、细胞黏附试验分别检测细胞生长、侵袭力和黏附力。结果:人卵巢癌HO-8910PM细胞株中存在HIF-1α的mRNA转录;在CoCl2模拟缺氧的时-效关系实验中,150μmol/LCoCl2刺激细胞8h、16h、24h时HIF-1αmRNA转录呈递增(分别为2.11±0.03、2.52±0.05、2.78±0.11)(P<0.05),24h达高峰,48h明显下降。同时,在量-效关系实验中,100μmol/L、150μmol/L刺激细胞16h时HIF-1αmRNA转录呈递增(分别为1.54±0.03、2.07±0.13)(P<0.05);MTT发现CoCl2诱导的缺氧对细胞生长起抑制作用;Boyden小室检测细胞侵袭力实验发现缺氧16h复氧24h后细胞的侵袭力增加(穿越细胞膜的细胞数86±9,较对照组53±10增加)(P<0.05);细胞黏附实验发现缺氧16h复氧24h后细胞的黏附力增加(P>0.05)。结论:CoCl2能诱导HO8910-PM细胞HIF-1α的过度转录,而且存在一定的时-效关系;经缺氧后复氧,肿瘤细胞的侵袭力和黏附力增加,且肿瘤细胞的侵袭力增加统计学差异显著。     

缺氧时肝癌HepG2细胞HIF-1α对GLUT-1表达的影响及机制探讨

目的探讨缺氧状态下肝癌HepG2细胞中HIF-1α表达对GLUT-1的影响。方法 HepG2人肝癌细胞株,以DMEM培养基加胎牛血清培养,分为常氧对照组(21%O2),缺氧组(1%O2),常氧加吲哚美辛组,缺氧加吲哚美辛组。收获细胞后,分别行免疫荧光法检测细胞内HIF-1α的表达和核转位;Western blot检测各组的HIF-1α、GLUT-1蛋白表达;RT-PCR检测各组的GLUT-1mRNA含量。结果缺氧时HIF-1α(蛋白:68.25±11.72)和GLUT-1(mRNA:0.7424±0.1127;蛋白:70.33±12.83)在肝癌HepG2细胞中的表达增高(P<0.05);缺氧时以吲哚美辛抑制HIF-1α蛋白(36.34±9.50)稳定和积聚后,GLUT-1 mRNA(0.3710±0.1016)及蛋白(38.46±12.20)表达受到抑制(P<0.05)。结论缺氧可以上调HIF-1α和GLUT-1在肝癌HepG2细胞中的表达;HIF-1α可以调控其下游靶基因GLUT-1的转录和表达,影响糖酵解和细胞能量的产生。     

HIF依赖性表达的自杀基因抑制肾细胞癌生长的实验研究

目的探讨依赖乏氧诱导因子(hypoxiainduciblefactor.HIF)依赖性表达的自杀基因治疗系统对肾细胞癌的治疗效果。方法借助DNA重组技术构建HIF依赖性表达的重组腺病毒载体Ad-5HRE/hCMVmp-BCD。用Westernblot检测细菌胞苷脱氨酶(bacterialcytosinedeaminase,BCD)的表达,细胞生长抑制试验检测人肾细胞癌786-0细胞对5-氟胞嘧啶(5-fluorocytosine,5-FC)的敏感性,裸鼠移植瘤试验观察Ad-5HRE/hCMVmp-BCD/5-FC对786-0细胞移植瘤的抑制效应。结果786-0细胞感染Ad-5HRE/hCM-Vmp-BCD后,可诱导BCD蛋白的表达,并显著提高细胞对5-FC的敏感性。裸鼠移植瘤试验结果显示,Ad-5HRE/hCMVmp-BCD/5-FC可抑制肾细胞癌移植瘤的生长。结论HIF依赖性表达的Ad-5HRE/hCM-Vmp-BCD/5-FC自杀基因系统可显著抑制肾细胞癌生长,具有良好的临床应用前景。     

Dual responsive promoters to target therapeutic gene expression to radiation-resistant hypoxic tumor cells

PURPOSE: Tumor hypoxia is unequivocally linked to poor radiotherapy outcome. This study aimed to identify enhancer sequences that respond maximally to a combination of radiation and hypoxia for use in genetic radiotherapy approaches. METHODS AND MATERIALS: The influence of radiation (5 Gy) and hypoxia (1% O2) on reporter-gene expression driven by hypoxia (HRE) and radiation (Egr-1) responsive elements was evaluated in tumor cells grown as monolayers or multicellular spheroids. Hypoxia-inducible factor-1alpha (HIF-1alpha) and HIF-2alpha protein expression was monitored in parallel. RESULTS: Of the sequences tested, an HRE from the phosphoglycerate kinase-1 gene (PGK-18[5+]) was maximally induced in response to hypoxia plus radiation in all 5 cell lines tested. The additional radiation treatment afforded a significant increase in the induction of PGK-18[5+] compared with hypoxia alone in 3 cell lines. HIF-1alpha/2alpha were induced by radiation but combined hypoxia/radiation treatment did not yield a further increase. The dual responsive nature of HREs was maintained when spheroids were irradiated after delivery of HRE constructs in a replication-deficient adenovirus. CONCLUSIONS: Hypoxia-responsive enhancer element sequences are dually responsive to combined radiation and hypoxic treatment. Their use in genetic radiotherapy in vivo could maximize expression in the most radio-resistant population at the time of radiation and also exploit microenvironmental changes after radiotherapy to yield additional switch-on.     

A noninvasive approach for assessing tumor hypoxia in xenografts: developing a urinary marker for hypoxia

Tumor hypoxia modifies the efficacy of conventional anticancer therapy and promotes malignant tumor progression. Human chorionic gonadotropin (hCG) is a glycoprotein secreted during pregnancy that has been used to monitor tumor burden in xenografts engineered to express this marker. We adapted this approach to use urinary beta-hCG as a secreted reporter protein for tumor hypoxia. We used a hypoxia-inducible promoter containing five tandem repeats of the hypoxia-response element (HRE) ligated upstream of the beta-hCG gene. This construct was stably integrated into two different cancer cell lines, FaDu, a human head and neck squamous cell carcinoma, and RKO, a human colorectal cancer cell line. In vitro studies showed that tumor cells stably transfected with this plasmid construct secrete beta-hCG in response to hypoxia or hypoxia-inducible factor 1alpha (HIF-1alpha) stabilizing agents. The hypoxia responsiveness of this construct can be blocked by treatment with agents that affect the HIF-1alpha pathways, including topotecan, 1-benzyl-3-(5'-hydroxymethyl-2'-furyl)indazole (YC-1), and flavopiridol. Immunofluorescent analysis of tumor sections and quantitative assessment with flow cytometry indicate colocalization between beta-hCG and 2-(2-nitro-1H-imidazol-1-yl)-N-(2,2,3,3,3-pentafluoropropyl)acetamide (EF5) and beta-hCG and pimonidazole, two extrinsic markers for tumor hypoxia. Secretion of beta-hCG from xenografts that contain these stable constructs is directly responsive to changes in tumor oxygenation, including exposure of the animals to 10% O2 and tumor bed irradiation. Similarly, urinary beta-hCG levels decline after treatment with flavopiridol, an inhibitor of HIF-1 transactivation. This effect was observed only in tumor cells expressing a HRE-regulated reporter gene and not in tumor cells expressing a cytomegalovirus-regulated reporter gene. The 5HRE beta-hCG reporter system described here enables serial, noninvasive monitoring of tumor hypoxia in a mouse model by measuring a urinary reporter protein.     

Noninvasive molecular imaging of hypoxia in human xenografts: comparing hypoxia-induced gene expression with endogenous and exogenous hypoxia markers

Tumor hypoxia is important in the development and treatment of human cancers. We have developed a novel xenograft model for studying and imaging of hypoxia-induced gene expression. A hypoxia-inducible dual reporter herpes simplex virus type 1 thymidine kinase and enhanced green fluorescence protein (HSV1-TKeGFP), under the control of hypoxia response element (9HRE), was stably transfected into human colorectal HT29 cancer cells. Selected clones were further enriched by repeated live cell sorting gated for hypoxia-induced eGFP expression. Fluorescent microscopy, fluorescence-activated cell sorting, and radioactive substrate trapping assays showed strong hypoxia-induced expression of eGFP and HSV1-tk enzyme in the HT29-9HRE cells in vitro. Sequential micropositron emission tomography (PET) imaging of tumor-bearing animals, using the hypoxic cell tracer (18)F-FMISO and the reporter substrate (124)I-FIAU, yielded similar tumor hypoxia images for the HT29-9HRE xenograft but not in the parental HT29 tumor. Using autoradiography and IHC, detailed spatial distributions in tumor sections were obtained and compared for the following hypoxia-associated biomarkers in the HT29-9HRE xenograft: (124)I-FIAU, (18)F-FMISO, Hoechst (perfusion), lectin-TRITC (functional blood vessels), eGFP, pimonidazole, EF5, and CA9. Intratumoral distributions of (124)I-FIAU and (18)F-FMISO were similar, and eGFP, pimonidazole, EF5, and CA9 colocalized in the same areas but not in well-perfused regions that were positive for Hoechst and lectin-TRITC. In enabling the detection of hypoxia-induced molecular events and mapping their distribution in vivo with serial noninvasive positron emission tomography imaging, and multiple variable analysis with immunohistochemistry and fluorescence microscopy, this human xenograft model provides a valuable tool for studying tumor hypoxia and in validating existing and future exogenous markers for tumor hypoxia.     

慢病毒介导5HRE-CEAp调控RASSF1A表达对胃癌细胞SGC7901抑制的研究

目的:探讨5拷贝低氧反应元件（5HRE）联合癌胚抗原启动子(CEAp)调控抑癌基因RAS相关域家族1A(RASSF1A)的慢病毒载体(LV-5HRE-CEAp-RASSF1A)对胃癌细胞SGC7901的体外抑制作用。方法:采用qRT-PCR方法检测空白对照组细胞SGC7901、阴性对照组细胞SGC7901/NC及慢病毒载体感染的实验组细胞SGC7901/5HRE-CEAp-RASSF1A中RASSF1A mRNA 表达水平;通过CCK-8实验检测各组细胞的生长曲线;通过流式细胞技术检测各细胞的凋亡及细胞周期。结果:qRT-PCR结果显示,与其他组比较,实验组细胞的RASSF1A mRNA水平在低氧条件下明显升高（P<0.01）;CCK-8实验结果显示从第3天开始,低氧条件下实验组细胞的OD值开始低于其它各组细胞（P<0.05）;流式细胞检测结果显示与其它各组细胞比较,低氧条件下实验组细胞凋亡比例明显增加（P<0.01）,并且其细胞周期G1期的细胞百分比明显增加（P<0.05）。结论:慢病毒载体LV-5HRE-CEAp-RASSF1A具有在低氧诱导下显著抑制胃癌细胞株SGC7901增殖的作用。     

CoCl2-induced HIF-1alpha expression correlates with proliferation and apoptosis in MKN-1 cells: a possible role for the PI3K/Akt pathway

The exact mechanism behind the effect of hypoxia-inducible factor-1alpha (HIF-1alpha) on the proliferation and/or apoptosis of carcinoma cells is still a matter of debate. We treated a human gastric carcinoma cell line, MKN-1 (mutant P53), with 500 microM CoCl(2). A dual-phase pattern of HIF-1alpha expression with an increase until 4 h followed by a decrease until 36 h was observed. Immunocytochemistry showed that nuclear translocation was maximal at 4 h of treatment, while trypan blue staining showed a dual-phase pattern. Instead of G1/S arrest, FACS showed an increase in the pre-G1 fraction and G(2)/M arrest that correlated with Cyclin-B1, SKP-2 and P27 expression. Starting at 6 h, the apoptotic index increased in a time-dependent manner, in correlation with the expression of HIF-1alpha, Bcl-2, Bcl-xL, Bax and cleaved-Caspase-9. Phosphorylation of Akt was inhibited by CoCl(2) treatment and LY294002 treatment inhibited HIF-1alpha expression in a dose-dependent manner. These results suggested that the alteration of CoCl(2)-induced HIF-1alpha expression correlated with proliferation and apoptosis in MKN-1 cells. A possible role for the PI3K/Akt pathway was indicated in this model of hypoxia.     

Cobalt chloride and low oxygen tension trigger differentiation of acute myeloid leukemic cells: possible mediation of hypoxia-inducible factor-1alpha.

Cellular and systemic O(2) concentrations are tightly regulated to maintain delicate oxygen homeostasis. Although the roles of hypoxia in solid tumors have been widely studied, few studies were reported regarding the possible effects of hypoxia on leukemic cells. Here, we showed for the first time that low concentrations of cobalt chloride (CoCl(2)), a hypoxia-mimicking agent, and 2-3% O(2) triggered differentiation of various subtypes of human acute myeloid leukemic (AML) cell lines, including NB4, U937 and Kasumi-1 cells, respectively, from M3, M5 and M2b-type AML, but CoCl(2) did not modulate AML subtype-specific fusion proteins promyelocytic leukemia-retinoic acid receptor alpha (PML-RARalpha) and AML1-ETO. Treatment with CoCl(2) also induced primary leukemic cells from some AML patients to undergo differentiation. Similar to what occurs in solid tumor cells, CoCl(2)-mimicked hypoxia also increased the level of hypoxia-inducible factor (HIF)-1alpha protein and its DNA-binding activity in leukemic cells. The CoCl(2) induction of HIF-1alpha protein and its DNA-binding activity were inhibited by 3-morpholinosydnonimine, which also blocked CoCl(2)-induced cell differentiation in leukemic cells. These results provide an insight into a possible link of hypoxia or HIF-1alpha and leukemic cell differentiation, and are possibly of significance to explore clinical potentials of hypoxia or hypoxia-mimicking agents and novel target-based drugs for differentiation therapy of leukemia.