热休克蛋白90抑制剂诱导Kasumi-1细胞凋亡和分化的机制探讨

目的探讨热休克蛋白90（HSP 90）抑制剂17-丙烯胺-17-去甲氧格尔德霉素（17AAG）诱导白血病细胞生长抑制、分化和凋亡作用.方法应用MTT比色法观察17AAG对白血病细胞系Kasumi-1细胞的生长抑制作用,用流式细胞术分析细胞周期和分化抗原的表达,用Annexin V标记、DNA凝胶电泳和流式细胞术分析细胞凋亡,Western blot检测干细胞因子受体（KIT）蛋白水平,RT-PCR测定c-kit mRNA水平.结果17AAG明显抑制Kasumi-l细胞的生长,半数抑制浓度（IC50）为0.62 μmol/L;17AAG诱导Kasumi-1细胞凋亡呈时间、剂量依赖性,17AAG处理24 h早期凋亡细胞增加,48 h晚期凋亡细胞增加,早期凋亡细胞减少.17AAG可诱导Kasumi-1细胞髓系分化抗原CD11b及CD15表达增加,并呈剂量和时间依赖性.经17AAG作用后细胞阻滞于G0/G1期,伴有S期细胞减少.Western blot检测发现17AAG可降低KIT水平,处理2 h开始减少,处理20 h后KIT基本消失,但c-kit mRNA水平并未受影响.结论HSP 90抑制剂17AAG通过降解KIT蛋白抑制Kasumi-1细胞生长,使细胞阻滞于G0/G1期,诱导其发生凋亡及部分分化.     

ASP2215联合SAHA对FLT3-ITD突变细胞株体外协同机制研究

目的：探究FLT3急性髓细胞性白血病（acute myeloid leukemia, AML）抑制剂ASP2215联合组蛋白去乙酰化酶（histone deacetylase inhibitor,HDAC）抑制剂SAHA,对伴FLT3-ITD突变的细胞株MV4-11的协同作用及其作用机制。方法：用不同浓度的ASP2215、SAHA单药或两药联合处理白血病细胞株MV4-11,观察细胞形态变化,采用CCK-8试剂盒检测其细胞活力,用流式细胞仪检测细胞凋亡率,蛋白免疫印迹检测FLT3及下游信号分子STAT5的磷酸化,分析凋亡调控蛋白Mcl-1、Bcl-xL、Bcl-2、Bax和caspase-9、caspase-3的蛋白含量。结果：①相较于FLT3野生型细胞株THP-1,ASP2215能够特异性地抑制FLT3-ITD突变AML细胞株MV4-11细胞的增殖。②ASP2215和SAHA单药处理均能抑制MV4-11细胞的活性,这种抑制作用呈浓度和时间依赖性,且两药联合使用时能够协同抑制MV4-11细胞株的活性,不同药物浓度联合的联合指数（combination index,CI）值皆小于1。③ASP2215和SAHA呈浓度和时间依赖性诱导MV4-11细胞凋亡,两者联合能够进一步增加MV4-11细胞凋亡。MV4-11细胞凋亡的过程中,伴caspase-3和caspase-9蛋白剪切活化,且活化程度随细胞凋亡增加而上升。相较于单药作用,两药联合能够引起更多的caspase-3和caspase-9剪切活化。形态学上,细胞凋亡和坏死改变随着药物浓度增加依次增多,且两药物联合能够引起细胞更明显的凋亡和坏死改变。④FLT3抑制剂ASP2215能够降低FLT3受体及下游分子STAT5的磷酸化水平,SAHA对FLT3及下游STAT5分子磷酸化也有轻度抑制作用。ASP2215和SAHA都能引起Mcl-1和Bcl-xL抗凋亡蛋白水平的降低,轻度下调Bcl-2蛋白和轻度上调Bax蛋白表达水平。两药联合相较于单药能够进一步下调Mcl-1、Bcl-xL的蛋白表达水平和Bcl-2/Bax蛋白比例。结论：ASP2215联合SAHA能够协同抑制伴FLT3-ITD突变MV4-11细胞株增殖,促进细胞凋亡,其机制涉及两药对FLT3-STAT5通路不同程度抑制作用,以及对凋亡相关蛋白Mcl-1、Bcl-xL及Bcl-2/Bax蛋白比例的调控。     

SARI过表达对CBFL细胞凋亡的影响及其机制

目的:探讨SARI基因过表达对核结合因子白血病(CBFL)细胞增殖、凋亡的影响及其机制。方法:通过17号外显子测序验证CBFL细胞模型Kasumi-1细胞负载c-KIT N822K突变。构建SARI基因过表达慢病毒载体,并转染Kasuimi-1细胞。采用荧光定量PCR和Western blot鉴定细胞转染后SARI基因过表达效果。设置空白对照(CON)、空载体对照(NC)和SARI过表达(OE) 3组。MTT法检测各组细胞增殖能力,流式细胞术检测细胞凋亡率,Western blot检测凋亡相关蛋白BCL-2、BAX、Cyto C、Caspase 9、Caspase 3、cleaved-Caspase 3、PARP、cleavedPARP,以及PI3K/Akt通路蛋白PI3K(p85)、p-PI3K(p85)、Akt、p-Akt的表达变化。结果:Kasumi-1细胞具有c-KIT N822K突变。成功构建稳定过表达SARI基因的Kasumi-1细胞。与NC组细胞相比,OE组细胞增殖减缓,凋亡增加;抗凋亡蛋白BCL-2表达降低,促凋亡蛋白BAX表达增高;出现Cyto C蛋白的表达; Caspase 9、Caspase 3表达降低,cleaved-Caspase3表达增高; PARP表达降低,活性剪切体cleaved-PARP表达增高,PI3K/Akt通路蛋白p-PI3K/PI3K、p-Akt/Akt磷酸化水平下调(P 0. 05)。结论:SARI基因过表达可通过线粒体途径诱导CBFL细胞凋亡,机制可能与PI3K/Akt信号通路失活有关。     

凋亡抑制蛋白c-FLIP高表达与白血病细胞耐药的关系

目的:探讨抗凋亡蛋白c-FLIP的表达对于白血病细胞系Kasumi-1细胞耐药的作用及其机制。方法:应用Tet-on系统,通过强力霉素(doxycycline,Dox)调控c-FLIP的条件性表达;将c-FLIP基因与慢病毒目的载体p LVX-Tight-puro连接,感染Kasumi-1细胞并获得稳定表达c-FLIP蛋白的稳定克隆;应用实时荧光定量PCR和Western blot方法证实c-FLIP在mRNA和蛋白水平的过表达情况;通过流式细胞术分析Fas激动剂CH11和HDAC抑制剂苯丁酸钠处理的Kasumi-1细胞的凋亡变化,以及过表达c-FLIP蛋白后对凋亡发生的影响;应用吉姆萨染色观察细胞凋亡形态变化,Western blot检测caspase-8凋亡信号通路的激活情况。结果:CH11和苯丁酸钠能够诱导Kasumi-1细胞凋亡,在Kasumi-1细胞过表达c-FLIP蛋白后,细胞能够抵抗CH11和苯丁酸钠诱导的凋亡;Western blot显示c-FLIP过表达阻滞了caspase-8凋亡信号通路的激活。结论:c-FLIP基因高表达使白血病细胞系Kasumi-1细胞对CH11和苯丁酸钠产生耐药作用。     

汉黄芩苷通过调控AKT信号通路促进肝癌细胞HepG2凋亡的研究

目的 探究汉黄芩苷(Wogonoside)对抑制肝癌细胞HepG2增殖及凋亡的影响及其机制。方法 体外培养肝癌细胞HepG2,随机分为对照组、汉黄芩苷治疗组、AKT激动剂处理组。通过CCK-8实验检测不同浓度汉黄芩苷对细胞活力的影响,运用Western blot实验检测肝癌细胞内Caspase-3、Bax和Bcl-2蛋白表达水平及AKT蛋白磷酸化水平,通过流式细胞技术检测肝癌细胞凋亡程度。结果 与对照组比较,汉黄芩苷治疗组细胞增殖能力显著降低(P<0.05),且存在量效关系,凋亡相关蛋白Caspase-3、Bax表达水平显著增加(P<0.05),而抗凋亡相关蛋白Bcl-2蛋白表达水平以及AKT蛋白磷酸化水平显著降低(P<0.05),凋亡程度显著增加(P<0.05)。与汉黄芩苷治疗组相比,AKT激动剂处理组凋亡相关蛋白Caspase-3、Bax表达水平显著降低(P<0.05),Bcl-2蛋白表达水平显著增加(P<0.05),凋亡程度显著降低(P<0.05)。结论 汉黄芩苷具有抑制肝癌HepG2细胞增殖并促进其凋亡的作用,其机制与调节AKT信号通路...     

c-Met抑制剂对人鼻咽癌细胞株CNE-1的生长抑制作用

目的:探讨c-Met抑制剂PHA-665752对人鼻咽癌细胞的生长抑制作用,为c-Met抑制剂在鼻咽癌中的应用提供实验依据。方法:Western blot法检测鼻咽癌细胞经HGF和(或)PHA-665752处理前后CNE-1细胞中相关信号分子的磷酸化状态变化。MTT法检测肝细胞生长因子(HGF)的促鼻咽癌细胞CNE-1的增殖作用。同时检测PHA-665752对CNE-1细胞的生长抑制作用。流式分析PHA-665752对鼻咽癌细胞CNE-1凋亡的影响。结果 :HGF可促进CNE-1细胞的增殖。而PHA-665752抑制了CNE-1细胞的增殖,并增强细胞凋亡。PHA-665752抑制c-Met磷酸化,同时降低下游信号分子Akt、Erk1/2和STAT3的磷酸化。结论:PHA-665752显著抑制鼻咽癌细胞CNE-1增殖,诱导细胞凋亡,其机制与调节下游MAPK、PI3K和STAT通路有关。     

癌蛋白NPM-ALK关键磷酸化位点对细胞周期的影响及其机制研究

目的:探讨NPM-ALK蛋白关键磷酸化位点Tyr644和Tyr664对细胞周期的影响及相关的分子机制。方法:建立NPM-ALK和NPM-ALK~(644,664)稳定表达的Jurkat细胞以及瞬时转染的293T细胞,检测各个细胞系的周期分布;应用软琼脂集落形成实验检验野生型NPM-ALK与双点突变型NPM-ALK致瘤能力的差异;利用蛋白质印迹法检测NPM-ALK关键磷酸化位点对下游相关蛋白表达、修饰的调控作用。结果:野生和突变NPM-ALK在瞬时转染的293T细胞和稳定转染的Jurkat细胞中成功表达,转入双点突变型NPM-ALK的Jurkat细胞与转入野生型NPM-ALK的细胞相比呈现出明显的细胞S期阻滞;酪氨酸激酶抑制剂PPP对野生型NPM-ALK转染的Jurkat细胞杀伤效果最强,对双点突变型NPM-ALK转染的细胞的杀伤作用与阴性对照无明显差异;随着NPM-ALK的转入,下游与细胞生长相关分子STAT3、AKT和ERK的磷酸化水平有所升高(P0.05),双点突变型NPM-ALK转入后,相关蛋白的磷酸化水平与野生型相比显著降低(P0.05)。结论:癌蛋白NPM-ALK的Tyr644和Tyr664两个关键磷酸化位点的突变会引起细胞S期阻滞和对药物PPP敏感性的降低,其机制可能与NPM-ALK下游的细胞生长相关分子的磷酸化表达变化相关。     

信号通路抑制剂XL765对人白血病KG-1细胞株的抑制效应研究

目的:探讨PI3K/mTOR信号通路抑制剂XL765(SAR245409, Voxtalisib)对人急性髓系白血病细胞株KG-1细胞的抑制效应及可能的作用机制。方法:应用CCK-8法检测XL765对KG-1细胞增殖的影响;平板集落形成实验检测XL765对KG-1细胞集落形成的抑制情况;Annexin V/PI双染色流式细胞术检测XL765对细胞凋亡的影响;实时荧光定量PCR检测细胞凋亡相关基因的表达;Western blot法检测凋亡相关蛋白的表达水平及信号通路分子磷酸化水平的变化。结果:XL765能有效抑制KG-1细胞的增殖,抑制率呈剂量依赖性增加;与DMSO处理组相比,加入XL765后,KG-1细胞的集落形成能力显著下降(P=0.0002);XL765能有效诱导细胞凋亡(P0.001);XL765作用KG-1细胞48 h后,细胞的凋亡相关基因BCL-2表达下调,BAX及Caspase3表达上调,其差异均有统计学意义(P0.05);与DMSO组对比,实验组BAX及Caspase3活化蛋白表达上调,同时BCL-2蛋白表达下调,信号蛋白PI3K、AKT及S6K磷酸化表达下调,其差异均有统计学意义(P值均0.005)。结论:XL765能有效抑制KG-1细胞增殖及集落形成,并诱导细胞凋亡,其机制可能与调节凋亡蛋白BCL2、BAX及Caspase3水平及抑制PI3K、AKT及S6K磷酸化水平相关。     

Hsp90选择性抑制剂17-AAG诱导白血病细胞株凋亡的基因谱研究

目的:探讨热休克蛋白90(Hsp90)抑制剂17-AAG对急性白血病细胞株HL-60和NB4细胞的凋亡诱导作用及其可能机制。方法:应用CCK-8比色法观察17-AAG对HL-60和NB4细胞的生长抑制作用;用Annexin V/PI标记流式细胞术分析细胞凋亡;Western blot检测凋亡相关蛋白Caspase-3和PARP的表达水平及其活化状态,采用实时定量PCR法检测17-AAG处理后NB4细胞的凋亡相关基因的mRNA变化。结果:17-AAG呈剂量依赖性抑制白血病细胞的生长。Annexin V测定、细胞周期分析和Caspase-3、PARP1的活化均表明17-AAG诱导白血病细胞的凋亡。实时荧光定量PCR分析发现,17-AAG处理后实验组和对照组相比有56个基因显著上调,23个基因显著下调。结论:17-AAG可诱导白血病细胞的凋亡,抑制细胞增殖。17-AAG处理白血病细胞后凋亡相关基因发生明显变化,激活凋亡信号通路可诱导细胞发生凋亡。     

HSP90抑制剂17-DMAG对急性淋巴细胞白血病Jurkat细胞株增殖和凋亡的影响

目的:探讨热休克蛋白90(HSP90)抑制剂17-二甲胺乙胺基-17去甲氧基格尔德霉素(17-DMAG)对急性淋巴细胞白血病Jurkat细胞的增殖及凋亡的影响。方法:收集Jurkat细胞,应用HSP90抑制剂17-DMAG作用于细胞株,通过半定量PCR检测HSP90的基因表达,WST技术检测17-DMAG对细胞增殖的影响,Annexin V/PI双染流式细胞术检测细胞凋亡。结果:不同浓度17-DMAG作用于Jurkat细胞48 h后,HSP90 mRNA表达明显减少,且呈剂量依赖性(r=0.9530,P0.01);17-DMAG处理Jurkat细胞48 h的IC50为3.17μmol/L,作用于Jurkat细胞后抑制Jurkat细胞增殖(r=0.9903,P0.01),促进Jurkat细胞凋亡,且呈剂量依赖性(r=0.9876,P0.01)。结论:HSP90抑制剂17-DMAG能够抑制急性淋巴细胞白血病Jurkat细胞株的增殖并诱导其凋亡。     

Potentiation of paclitaxel activity by the HSP90 inhibitor 17-allylamino-17-demethoxygeldanamycin in human ovarian carcinoma cell lines with high levels of activated AKT

Activation of the phosphatidylinositol-3-kinase (PI3K)/AKT survival pathway is a mechanism of cytotoxic drug resistance in ovarian cancer, and inhibitors of this pathway can sensitize to cytotoxic drugs. The HSP90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) depletes some proteins involved in PI3K/AKT signaling, e.g., ERBB2, epidermal growth factor receptor (EGFR), and phosphorylated AKT (p-AKT). 17-AAG and paclitaxel were combined (at a fixed 1:1 ratio of their IC(50)) in four ovarian cancer cell lines that differ in expression of p-AKT, EGFR, and ERBB2. The EGFR-overexpressing A431 and KB epidermoid cell lines were also included. Combination indices (CI) were calculated using the median-effect equation and interpreted in the context of 17-AAG-mediated inhibition of PI3K signaling. Synergy was observed in IGROV-1- and ERBB2-overexpressing SKOV-3 ovarian cancer cells that express a high level of constitutively activated p-AKT [CI at fraction unaffected (fu)(0.5) = 0.50 and 0.53, respectively]. Slight synergy was observed in A431 cells (moderate p-AKT/overexpressed EGFR; CI at fu(0.5) = 0.76) and antagonism in CH1 (moderate p-AKT), HX62 cells (low p-AKT), and KB cells (low p-AKT/overexpressed EGFR; CI at fu(50) = 3.0, 3.5, and 2.0, respectively). The observed effects correlated with changes in the rate of apoptosis induction. 17-AAG induced a decrease in HSP90 client proteins (e.g., C-RAF, ERBB2, and p-AKT) or in downstream markers of their activity (e.g., phosphorylated extracellular signal-regulated kinase or p-AKT) in SKOV-3, IGROV-1, and CH1 cells at IC(50) concentrations. A non-growth-inhibitory concentration (6 nmol/L) reduced the phosphorylation of AKT (but not extracellular signal-regulated kinase) and sensitized SKOV-3 cells to paclitaxel. In conclusion, 17-AAG may sensitize a subset of ovarian cancer to paclitaxel, particularly those tumors in which resistance is driven by ERBB2 and/or p-AKT.     

17-Allylamino-17-demethoxygeldanamycin enhances the lethality of deoxycholic acid in primary rodent hepatocytes and established cell lines

Ansamycin antibiotics that target heat shock protein 90 function are being developed as anticancer agents but are also known to be dose limiting in patients due to hepatotoxicity. Herein, to better understand how the normal tissue toxicity of geldanamycins could be ameliorated to improve the therapeutic index of these agents, we examined the interactions of 17-allylamino-17-demethoxygeldanamycin (17AAG) and the secondary bile acid deoxycholic acid (DCA) in hepatocytes and fibroblasts. DCA and 17AAG interacted in a greater than additive fashion to cause hepatocyte cell death within 2 to 6 h of coadministration. As single agents DCA, but not 17AAG, enhanced the activity of extracellular signal-regulated kinase 1/2, AKT, c-Jun NH(2)-terminal kinase 1/2 (JNK1/2), and p38 mitogen-activated protein kinase (MAPK). Combined exposure of cells to DCA and 17AAG further enhanced JNK1/2 and p38 MAPK activity. Inhibition of JNK1/2 or p38 MAPK, but not activator protein-1, suppressed the lethality of 17AAG and of 17AAG and DCA. Constitutive activation of AKT, but not MAPK/extracellular signal-regulated kinase kinase 1/2, suppressed 17AAG- and DCA-induced cell killing and reduced activation of JNK1/2. DCA and 17AAG exposure promoted association of BAX with mitochondria, and functional inhibition of BAX or caspase-9, but not of BID and caspase-8, suppressed 17AAG and DCA lethality. DCA and 17AAG interacted in a greater than additive fashion to promote and prolong the generation of reactive oxygen species (ROS). ROS-quenching agents, inhibition of mitochondrial function, expression of dominant-negative thioredoxin reductase, or expression of dominant-negative apoptosis signaling kinase 1 suppressed JNK1/2 and p38 MAPK activation and reduced cell killing after 17AAG and DCA exposure. The potentiation of DCA-induced ROS production by 17AAG was abolished by Ca(2+) chelation and ROS generation, and cell killing following 17AAG and DCA treatment was abolished in cells lacking expression of PKR-like endoplasmic reticulum kinase. Thus, DCA and 17AAG interact to stimulate Ca(2+)-dependent and PKR-like endoplasmic reticulum kinase-dependent ROS production; high levels of ROS promote intense activation of the p38 MAPK and JNK1/2 pathways that signal to activate the intrinsic apoptosis pathway.     

HSP抑制剂对食管鳞癌细胞株 TE-凋亡的影响及作用机制研究

目的探讨抑制热休克蛋白90（Hsp90）对食管鳞癌细胞株TE-1凋亡的影响。方法采用不同浓度（0.25、0.5、1.0、2.0 μmol/L）、不同时间（24、48、72 h）HSP90抑制剂17-烯丙胺-17-脱甲氧格尔德霉素(17-AAG)处理食管鳞癌细胞株TE-1,分别采用MTT法、流式细胞仪及western blot检测细胞增殖、细胞凋亡及Hsp90、Hsp70、Akt、Fas蛋白表达。 结果17-AAG对TE-1细胞体外增殖抑制率和细胞凋亡率有明显促进作用,并呈现时间-剂量依赖性。17-AAG 处理后TE-1 细胞Hsp90、Akt 蛋白表达明显降低,Hsp70、Fas蛋白表达明显上调。 结论17-AAG可显著抑制TE-1增殖,促进凋亡,其机制可能是通过抑制Hsp90活性、影响其相关信号通路所致。       

Inhibiting the HSP90 chaperone destabilizes macrophage migration inhibitory factor and thereby inhibits breast tumor progression

Intracellular macrophage migration inhibitory factor (MIF) often becomes stabilized in human cancer cells. MIF can promote tumor cell survival, and elevated MIF protein correlates with tumor aggressiveness and poor prognosis. However, the molecular mechanism facilitating MIF stabilization in tumors is not understood. We show that the tumor-activated HSP90 chaperone complex protects MIF from degradation. Pharmacological inhibition of HSP90 activity, or siRNA-mediated knockdown of HSP90 or HDAC6, destabilizes MIF in a variety of human cancer cells. The HSP90-associated E3 ubiquitin ligase CHIP mediates the ensuing proteasome-dependent MIF degradation. Cancer cells contain constitutive endogenous MIF-HSP90 complexes. siRNA-mediated MIF knockdown inhibits proliferation and triggers apoptosis of cultured human cancer cells, whereas HSP90 inhibitor-induced apoptosis is overridden by ectopic MIF expression. In the ErbB2 transgenic model of human HER2-positive breast cancer, genetic ablation of MIF delays tumor progression and prolongs overall survival of mice. Systemic treatment with the HSP90 inhibitor 17AAG reduces MIF expression and blocks growth of MIF-expressing, but not MIF-deficient, tumors. Together, these findings identify MIF as a novel HSP90 client and suggest that HSP90 inhibitors inhibit ErbB2-driven breast tumor growth at least in part by destabilizing MIF.     

Mitogen-activated protein kinase kinase 1/2 inhibitors and 17-allylamino-17-demethoxygeldanamycin synergize to kill human gastrointestinal tumor cells in vitro via suppression of c-FLIP-s levels and activation of CD95

Prior studies have noted that inhibitors of mitogen-activated protein kinase (MAPK) kinase 1/2 (MEK1/2) enhanced geldanamycin lethality in malignant hematopoietic cells by promoting mitochondrial dysfunction. The present studies focused on defining the mechanism(s) by which these agents altered survival in carcinoma cells. MEK1/2 inhibitors [PD184352; AZD6244 (ARRY-142886)] interacted in a synergistic manner with geldanamycins [17-allylamino-17-demethoxygeldanamycin (17AAG) and 17-dimethylaminoethylamino-17-demethoxy-geldanamycin] to kill hepatoma and pancreatic carcinoma cells that correlated with inactivation of extracellular signal-regulated kinase 1/2 and AKT and with activation of p38 MAPK; p38 MAPK activation was reactive oxygen species dependent. Treatment of cells with MEK1/2 inhibitors and 17AAG reduced expression of c-FLIP-s that was mechanistically connected to loss of MEK1/2 and AKT function; inhibition of caspase-8 or overexpression of c-FLIP-s abolished cell killing by MEK1/2 inhibitors and 17AAG. Treatment of cells with MEK1/2 inhibitors and 17AAG caused a p38 MAPK-dependent plasma membrane clustering of CD95 without altering the levels or cleavage of FAS ligand. In parallel, treatment of cells with MEK1/2 inhibitors and 17AAG caused a p38 MAPK-dependent association of caspase-8 with CD95. Inhibition of p38 MAPK or knockdown of BID, FAS-associated death domain, or CD95 expression suppressed MEK1/2 inhibitor and 17AAG lethality. Similar correlative data were obtained using a xenograft flank tumor model system. Our data show that treatment of tumor cells with MEK1/2 inhibitors and 17AAG induces activation of the extrinsic pathway and that suppression of c-FLIP-s expression is crucial in transduction of the apoptotic signal from CD95 to promote cell death. [Mol Cancer Ther 2008;7(9):2633-48].     

Role for NAD(P)H:quinone oxidoreductase 1 and manganese-dependent superoxide dismutase in 17-(allylamino)-17-demethoxygeldanamycin-induced heat shock protein 90 inhibition in pancreatic cancer cells

Previous work demonstrated that NAD(P)H:quinone oxidoreductase 1 (NQO1) metabolized the heat shock protein 90 (Hsp90) inhibitor 17-(allylamino)-17-demethoxygeldanamycin (17AAG) to the corresponding hydroquinone (17AAGH?). The formation of 17AAGH? by NQO1 results in a molecule that binds with greater affinity to Hsp90 compared with the parent quinone. 17AAG induced substantial growth inhibition in human pancreatic cancer cell lines expressing NQO1. Growth inhibition induced by 17AAG could be reduced by pretreatment with 5-methoxy-1,2-dimethyl-3-[(4-nitrophenoxy)methyl]-indole-4,7-dione (ES936), a mechanism-based inhibitor of NQO1. After treatment with 17AAG, biomarkers of Hsp90 inhibition, including markers of cell-cycle arrest, were more pronounced in NQO1-expressing cells compared with NQO1-null cells. The intracellular concentrations of 17AAG and 17AAGH? were measured in human pancreatic cancer cells, and it was observed that larger amounts of 17AAG and 17AAGH? could be detected in cells with catalytically active NQO1 compared with cells lacking NQO1 activity or cells pretreated with ES936. These data demonstrate that, in addition to generating an inhibitor with greater affinity for Hsp90 (17AAGH?), reduction of 17AAG to 17AAGH? by NQO1 leads to substantially greater intracellular concentrations of 17AAG and 17AAGH?. In addition, oxidation of 17AAGH? could be prevented by superoxide dismutase (SOD), demonstrating that 17AAGH? was sensitive to oxidation by superoxide. Stable transfection of manganese-dependent SOD into MiaPaCa-2 cells resulted in a significantly greater intracellular concentration of 17AAGH? with a corresponding increase in growth inhibitory activity. These data confirm the role of NQO1 in sensitivity to 17AAG and demonstrate that SOD functions in conjunction with NQO1 to maintain intracellular levels of 17AAGH?, the active Hsp90 inhibitor derived from 17AAG.     

IFN-γ对AKT基因激活的32D细胞的影响及作用机制探讨

目的 观察IFN-γ对AKT基因激活的小鼠髓系祖细胞系(32D细胞)的影响,探讨IFN-γ对造血细胞增殖和凋亡双向调节的可能机制.方法 用质粒转导技术使32D细胞高表达AKT基因,以IFN-γ作用32D细胞,用水溶性四氮唑(WST-1)细胞增殖检测法检测细胞增殖水平,流式细胞术检测细胞凋亡率,Western blot法检测磷酸化胞外信号调节激酶(p-Erk)1/2、信号转导和转录活化蛋白(Stat)3、p-Stat3的表达.结果 ①低浓度(100 U/ml)IFN-γ能促进32D细胞增殖、抑制凋亡,高浓度(1000 U/ml)IFN-γ则相反(100 U/ml处理24 h细胞密度为0.238±0.010;而1000 U/ml处理后为0.106±0.010,未处理组为0.170±0.010).②低浓度IFN-γ可使32D细胞内Stat3磷酸化水平升高(1124±13),高浓度时减低(601±13).③转染激活型AKT质粒的32D细胞(激活型细胞)较其他组细胞的增殖率显著增高、凋亡率明显降低[分别为0.287±0.010、(9.57±0.17)%](P＜0.05).④激活型32D细胞较其他组细胞p-Erk1/2蛋白表达明显减低(P＜0.05).结论 ①IFN-γ对32D细胞有双重作用,即低浓度促进细胞增殖、抑制凋亡,高浓度抑制细胞增殖、促进凋亡.②IFN-γ对32D细胞的双重效应可能是通过Stat3的磷酸化水平的增减实现的.③激活型AKT能明显促进32D细胞增殖、抑制凋亡,IFN-γ可通过调控AKT来调节细胞增殖及凋亡.④AKT激活后可以抑制Erk信号通路,可能是通过抑制Rafl的修饰实现的.     

The HSP90 Inhibitor, AT13387, Is Effective against Imatinib-Sensitive and -Resistant Gastrointestinal Stromal Tumor Models

The majority of gastrointestinal stromal tumors (GIST) are characterized by activating mutations of KIT, an HSP90 client protein. Further secondary resistance mutations within KIT limit clinical responses to tyrosine kinase inhibitors, such as imatinib. The dependence of KIT and its mutated forms on HSP90 suggests that HSP90 inhibition might be a valuable treatment option for GIST, which would be equally effective on imatinib-sensitive and -resistant clones. We investigated the activity of AT13387, a potent HSP90 inhibitor currently being evaluated in clinical trials, in both in vitro and in vivo GIST models. AT13387 inhibited the proliferation of imatinib-sensitive (GIST882, GIST-T1) and -resistant (GIST430, GIST48) cell lines, including those resistant to the geldanamycin analogue HSP90 inhibitor, 17-AAG. Treatment with AT13387 resulted in depletion of HSP90 client proteins, KIT and AKT, along with their phospho-forms in imatinib-sensitive and -resistant cell lines, irrespective of KIT mutation. KIT signaling was ablated, whereas HSP70, a marker of HSP90 inhibition, was induced. In vivo, antitumor activity of AT13387 was showed in both the imatinib-sensitive, GIST-PSW, xenograft model and a newly characterized imatinib-resistant, GIST430, xenograft model. Induction of HSP70, depletion of phospho-KIT and inhibition of KIT signaling were seen in tumors from both models after treatment with AT13387. A combination of imatinib and AT13387 treatment in the imatinib-resistant GIST430 model significantly enhanced tumor growth inhibition over either of the monotherapies. Importantly, the combination of AT13387 and imatinib was well tolerated. These results suggest AT13387 is an excellent candidate for clinical testing in GIST in combination with imatinib. Mol Cancer Ther; 11(8); 1799-808. ?2012 AACR.