EGCG通过下调Bcl-2、NF-κB(p65)表达,活化Caspase-3诱导人胃癌细胞凋亡的实验研究

目的:观察表没食子儿茶素没食子酸酯(Epigallocatechin-3-gallate, EGCG)对人胃癌SGC7901细胞裸鼠移植瘤生长的抑制作用,探讨EGCG诱导移植瘤细胞凋亡作用的分子机制. 方法:建立人胃腺癌(SGC7901)细胞裸鼠异种移植瘤模型,用不同剂量的EGCG进行治疗,并设对照;采用TUNEL法检测肿瘤组织中细胞凋亡情况,Western blot法检测肿瘤组织凋亡相关基因NF-κB(p65)、Bcl-2、Bax、Caspase-3蛋白表达情况. 结果:EGCG对移植瘤生长有明显抑制作用;TUNEL法发现EGCG导致移植瘤内细胞发生凋亡;Western blot分析表明EGCG能下调NF-κB(p65)蛋白的表达,促使Bax/Bcl-2蛋白表达的比值增高,并且可以促进Caspase-3的活化. 结论:EGCG对人胃癌细胞裸鼠移植瘤有明显的抑制作用,并能诱导移植瘤细胞凋亡.其机制可能与通过NF-κB(p65)的下调,促使Bax/Bcl-2比值增高,进而导致Caspase-3的活化而诱导细胞发生凋亡相关.     

核因子-κB/p65表达下调对舌鳞状细胞癌裸鼠移植瘤中bcl-2和bax表达的影响

目的:本实验旨在探讨下调核因子-κB(nuclear factor-kappa B,NF-κB)/p65亚单位的表达对舌鳞状细胞癌裸鼠移植瘤生长及细胞凋亡相关基因bcl-2和bax表达的影响。方法:应用舌鳞状细胞癌Tca8113细胞建立舌鳞状细胞癌裸鼠移植瘤模型。将针对p65的小干扰RNA(small interfering RNA,siRNA)接种荷瘤裸鼠,观察下调NF-κB/p65表达后荷瘤裸鼠的生长情况;采用TUNEL法检测肿瘤组织中的细胞凋亡情况;进一步应用RT-PCR和Western印迹法检测肿瘤组织中p65、bcl-2和bax的mRNA及蛋白表达变化。结果:经p65siRNA治疗后,肿瘤的生长明显受到抑制(P<0.05);TUNEL结果表明,p65siRNA组肿瘤细胞明显发生凋亡;此外,p65siRNA组裸鼠肿瘤组织p65和bcl-2的mRNA及蛋白表达明显下调,而bax的mRNA及蛋白表达显著上调,差异均有统计学意义(均P<0.05)。结论:NF-κB/p65亚基可能在舌鳞状细胞癌的细胞凋亡中发挥重要作用。     

NF-κB p65对人非霍奇金淋巴瘤细胞凋亡调控的研究

目的:研究NF-κB p65对人非霍奇金淋巴瘤(NHL)细胞凋亡的作用及其调控机制。方法:以NF-κB p65抑制剂quinazoline(QNZ)处理人NHL细胞,采用Annexin-Ⅴ染色方法检测肿瘤凋亡水平的变化,蛋白质印迹法检测各细胞系中Survivin蛋白及凋亡相关蛋白Bax、Bcl-2和Cleaved Caspase-3的表达水平;进一步应用实时定量PCR方法检测Survivin mRNA水平。结果:NF-κB p65抑制剂QNZ能够诱导NHL细胞的凋亡(P<0.05),具有时间-剂量依赖性。10nmol/L QNZ作用72h后Namalwa、Ramos和Raji细胞凋亡率分别为(13.5±2.7)%、(16.4±2.8)%和(15.8±2.5)%。抑制NF-κB p65的表达能够显著下调淋巴瘤细胞中Survivin蛋白的表达水平,10nmol/L QNZ作用72h后Namalwa、Ramos和Raji细胞中Survivin蛋白表达为0.58±0.06、0.54±0.03和0.51±0.09。同时,凋亡相关蛋白Bcl-2表达减低而Bax和Cleaved Caspase-3蛋白表达增加,Bcl-2与Bax蛋白比值明显降低,与对照组相比差异均有统计学意义,P<0.05。预处理QNZ后3种NHL细胞Survivin mRNA均不同程度下降,随浓度增加其作用更为明显,P<0.05。结论:抑制NF-κB p65能够诱导NHL细胞凋亡,其机制可能与下调Survivin蛋白表达水平及对凋亡相关蛋白Bcl-2家族的调节有关。     

新城疫病毒7793株抑制人结肠癌LoVo细胞裸鼠移植瘤的生长及其机制

目的:观察新城疫病毒7793株(Newcastle disease virus 7793 strain,NDV 7793)对人结肠癌LoVo细胞裸鼠移植瘤生长的作用,并探讨其可能机制。方法:建立LoVo细胞裸鼠移植瘤模型,随机分成3组,分别静脉注射PBS、5-FU以及NDV 7793,观察各组裸鼠肿瘤的生长情况,流式细胞术检测移植瘤细胞的坏死率和凋亡率,免疫组织化学法检测移植瘤组织中Bax、Bcl-2蛋白的表达,细胞色素C试剂盒检测移植瘤组织中细胞色素C的含量,ELISA法检测移植瘤组织中TNF-α含量。结果:NDV 7793较5-FU更明显抑制LoVo细胞移植瘤的生长(抑制率50.14%vs 37.14%,P<0.05)。NDV 7793组移植瘤LoVo细胞凋亡率显著高于5-FU对照组[(28.7±1.5)%vs(1.46±0.3)%,P<0.01],且NDV 7793组诱导LoVo细胞的凋亡率和坏死率[(28.7±1.5)%vs(27.80±3.32)%]相当。NDV 7793能促进移植瘤组织中Bax蛋白的表达,对Bcl-2蛋白的表达无影响。NDV 7793可提高移植瘤组织中的细胞色素C含量[(2.28±0.68)vs(0.68±0.13)μg/μl]和TNF-α的水平[(489.6±5.2)vs(167.9±3.9)pg/ml]。结论:NDV 7793可抑制人结肠癌LoVo细胞移植瘤的生长,其机制可能与其上调Bax蛋白、细胞色素C和TNF-α的表达,以及促进肿瘤细胞凋亡有关。     

IP6对结肠癌裸鼠皮下移植瘤细胞生长抑制及其机制的探讨

目的:研究肌醇六磷酸(IP6)对HT-29细胞裸鼠皮下移植瘤生长的抑制作用.方法:建立HT-29细胞裸鼠移植瘤模型,随机分为对照组(生理盐水组)、低剂量IP6组和高剂量IP6组,用药20 d后处死小鼠.比较各组抑瘤作用和裸鼠一般状态的变化,透射电镜观察移植瘤细胞形体变化,TUNEL法检测移植瘤细胞凋亡情况,并运用RT-PCR、蛋白质印迹法检测移植瘤Bcl-2及Bax基因和蛋白的表达.结果:IP6组出现典型凋亡现象,PCR及蛋白检测也显示IP6可显著上调Bax蛋白的表达,下调Bcl-2蛋白的表达(P＜0.05);在移植瘤质量和体积方面,用药组与对照组差异无统计意义,P＞0.05,但用药组移植瘤呈现下降趋势.结论:IP6可能通过促进细胞凋亡而起到抑制和延缓肿瘤生长的作用,其机制可能与上调Bax蛋白表达和下调Bcl-2蛋白表达有关.     

塞来昔布抑制人类三阴性乳腺癌裸鼠移植瘤生长的实验研究

 【摘要】　目的　探讨塞来昔布（celecoxib）对人类三阴性乳腺癌（TNBC）肿瘤生长及细胞凋亡的影响。方法　32只裸鼠于背部皮下接种人类TNBC细胞株MDA-MB-231,随机分为空白对照组及低、中、高剂量塞来昔布组（25、50、100 mg?kg-1?d-1）。实验结束后,留取移植瘤标本,观察用药前后裸鼠肿瘤体积的变化;流式细胞术（FCM）检测肿瘤细胞凋亡率;免疫组织化学法检测NF-κB p65和p50分子的表达;Western blot法检测凋亡相关分子Caspase-3、Survivin蛋白的表达。结果　塞来昔布治疗组肿瘤体积较对照组均明显减小。中、高剂量塞来昔布治疗组凋亡率分别为（13.58±3.16）％、（21.91±4.75）％,与对照组的（3.15±1.73）％相比差异有统计学意义（t＝6.736,12.151,均P＜0.05）,塞来昔布低、中、高剂量组p65表达阳性率分别为79.3 %、46.7 %、23.9 %,与对照组（89.7 %）相比差异有统计学意义（χ2＝3.312,10.785,15.900,均P＜0.05）。Western blot结果显示,塞来昔布治疗后肿瘤组织中Caspase-3蛋白出现了裂解片段,并且随药物浓度增加,裂解片段表达量逐渐增加。Survivin蛋白随药物浓度增加表达逐渐下调。结论　塞来昔布可以诱导TNBC裸鼠移植瘤细胞凋亡,抑制肿瘤生长,其抗肿瘤作用机制可能部分与抑制p65分子以及下调Survivin蛋白表达有关。     

TNF-α联合多西紫杉醇治疗肾癌的实验研究

目的:探讨TNF-α联合多西紫杉醇治疗肾癌的作用,并进一步了解其作用机理.方法:建立人肾癌细胞的裸鼠皮下移植瘤模型,在TNF-α和多西紫杉醇的联合作用下观察其对皮下移植瘤生长的抑制作用,并通过RT-PCR、免疫组化方法检测Bax、Bcl-2基因mRNA表达及p53蛋白表达的影响.结果:与TNF-α组、多西紫杉醇组及对照组相比,TNF-α和多西紫杉醇联合治疗组可抑制肾癌皮下移植瘤生长速度,且肿瘤体积明显减少(P<0.01).Bax mRNA表达上调,而Bcl-2表达水平下降, 免疫组化结果表明p53蛋白的表达水平下降.结论:TNF-α和多西紫杉醇对肾癌有一定的治疗作用,作用机理可能是通过引起促凋亡基因Bax表达增高,从而导致肿瘤细胞加速凋亡而实现的.     

腺病毒介导PTEN过表达抑制人脑胶质瘤U251细胞裸鼠移植瘤的生长

目的:研究含第10号染色体同源丢失性磷酸酶-张力蛋白(phosphatase and tensin homologue deleted on chromo-some 10,PTEN)基因的重组腺病毒(Ad-PTEN-GFP)对人胶质瘤U251细胞裸鼠移植瘤生长的抑制作用。方法:于裸鼠背部注射人脑胶质瘤U251细胞,建立胶质瘤裸鼠移植瘤模型。荷瘤裸鼠随机分为3组进行治疗:Ad-PTEN-GFP组,Ad-GFP组(空载体组)及PBS组(空白组),观察3组裸鼠移植瘤的生长,测量肿瘤体积,绘制肿瘤生长曲线,并观察荷瘤裸鼠的生存时间。采用TUNEL法检测移植瘤组织中细胞凋亡的情况,采用免疫组化法检测移植瘤组织中PTEN及P65蛋白的表达。结果:与Ad-GFP组相比,Ad-PTEN-GFP组移植瘤的生长受到抑制,肿瘤体积抑制率显著升高[(82.5±12.7)%vs(7.2±1.3)%,P<0.05],荷瘤裸鼠生存时间延长[(103±10)vs(58±8)d,P<0.01];TUNEL结果表明,Ad-PTEN-GFP组与Ad-GFP组相比,移植瘤细胞凋亡率明显增加[(46.4±8.3)%vs(4.6±1.0)%,P<0.01];免疫组化结果显示,Ad-PTEN-GFP组与Ad-GFP组相比,移植瘤组织中PTEN蛋白的阳性表达率增高(83.3%vs 0,P<0.01),P65蛋白阳性表达率下降(16.7%vs 66.7%,P<0.01)。结论:感染Ad-PTEN-GFP后人脑胶质瘤U251细胞裸鼠移植瘤的生长受到抑制,其机制可能与P65蛋白表达的下调有关。     

表没食子儿茶素没食子酸酯诱导人胃癌细胞裸鼠移植瘤凋亡的研究

背景与目的探讨绿茶提取物表没食子儿茶素没食子酸酯(epigallocatechin-3-gallate,EGCG)诱导人胃癌细胞裸鼠移植瘤凋亡及分子机制。方法建立人胃腺癌(SGC7901)细胞裸鼠异种移植瘤模型,用不同剂量的EGCG进行治疗,并设对照,用流式细胞分析术检测肿瘤组织中细胞凋亡情况,免疫组织化学方法检测肿瘤组织的凋亡相关基因Bcl-2、Bax、Caspase-3的表达情况。结果裸鼠异种移植瘤治疗实验结果显示,EGCG对移植瘤生长有明显抑制作用(其中20mg/kg、EGCG抑制率54.64%与对照组比较P<0.05);PI染色FCM分析发现,EGCG20mg/kg能诱导移植瘤细胞凋亡率17.2%与对照组比P<0.05;SP免疫组织化学结果表明EGCG可上调移植瘤细胞中Bax、Caspase-3蛋白的表达,下调Bcl-2蛋白的表达。结论表没食子儿茶素没食子酸酯(EGCG)具有体内诱导人胃腺癌细胞凋亡的作用,其机制可能与Bcl-2/Bax比值降低导致Caspase-3的活化从而启动细胞凋亡有关。     

吴茱萸碱联合放射治疗对舌鳞癌细胞Tca-8113裸鼠移植瘤生长的抑制作用

目的:研究吴茱萸碱(evodiamine,EVO)联合射线对舌鳞癌细胞Tca-8113裸鼠移植瘤生长的抑制作用。方法:建立舌鳞癌Tca-8113细胞裸鼠皮下移植瘤模型16只,随机分为空白对照组、EVO组、放射组及联合组,观察并绘制肿瘤生长曲线图,计算肿瘤抑制率;肿瘤组织通过常规苏木精-伊红染色行病理学检查;免疫组织化学法检测移植瘤组织中Ki67、Bax和Bcl-2表达情况;透射电子显微镜观察细胞凋亡形态。结果:治疗第12天起,联合组肿瘤体积与其余各组相比,明显减小(P<0.05);治疗结束时,EVO组、放射组和联合组的抑瘤率分别为15.15%、43.29%和63.20%。联合组Ki67和Bcl-2表达水平较EVO组和放射组下降,Bax表达水平增高(P<0.05)。联合组坏死细胞数增多,且细胞呈典型凋亡特征。结论:放疗联合EVO能抑制舌鳞癌Tca-8113细胞裸鼠移植瘤的生长,可能与Ki67和Bcl-2表达下调以及Bax表达上调有关。     

延龄草总皂苷抑制乳腺癌细胞MDA-MB-231裸鼠移植瘤的增殖和促进凋亡作用

目的:观察延龄草总皂苷对乳腺癌细胞MDA-MB-231裸鼠皮下移植瘤的影响及相关机制。方法:培养乳腺癌细胞MDA-MB-231,接种至BALB/c裸鼠背部皮下。接种后第5天通过腹腔注射的方式给裸鼠予延龄草总皂苷治疗,每隔3天测量移植瘤的体积以及裸鼠的体重;实验结束时,采用TUNEL试剂盒检测移植瘤细胞的凋亡情况;Western blot法检测凋亡相关蛋白剪切型caspase-3,8,9表达的变化。结果:延龄草总皂苷可有效地抑制裸鼠移植瘤的增殖,实验结束时,肿瘤的体积分别为:模型组(1142.24±164.32)mm3,延龄草总皂苷(5 mg/kg)(552.90±49.71)mm3,延龄草总皂苷(10 mg/kg)(269.78±48.84)mm3。延龄草总皂苷能诱导移植瘤细胞的凋亡,可浓度依赖性地促进细胞中剪切型caspase-3,9的表达。结论:延龄草总皂苷可有效地抑制MDA-MB-231裸鼠移植瘤的增殖,其方式可能通过caspase依赖的方式促使MDA-MB-231发生凋亡。     

沉默p65基因对人乳腺癌细胞MDA-MB-231细胞周期的影响

目的研究miRNA(microRNA)沉默p65基因后对人乳腺癌细胞株MDA-MB-231细胞周期分布的影响。方法用pcDNATM6.2-GW/EmGFP-miR载体构建p65 miRNA表达质粒,转染MDA-MB-231细胞,用RT-PCR检测转染前后各组细胞中p65 mRNA表达变化;凝胶电泳迁移率改变分析(electrophoretic mobility shift assay, EMSA)实验研究转染前后细胞中NF-κB结合活性的变化;流式细胞术(Flow cytometry, FCM)观察转染前后细胞周期分布的变化;Westernblot法检测转染前后细胞周期相关因子cyclinD1、CDK4、p21蛋白表达的变化。结果p65 miRNA质粒明显下调MDA-MB-231细胞中p65 mRNA的表达水平,并显著抑制细胞中NF-κB的结合活性(P<0.05)。FCM结果显示,转染组细胞G₀/G₁期细胞比例显著增加,S、G₂/M期细胞比例明显下降(P<0.05);Western blot分析结果显示,沉默p65基因后细胞中cyclinD1蛋白表达下调,p21蛋白表达增加。结论p65 miRNA可以显著降低p65 mRNA的表达,诱导乳腺癌细胞发生G₀/G₁期阻滞,可能是通过降低cyclinD1蛋白,上调p21蛋白表达而实现的。     

siRNA沉默LKB1基因激活Hedgehog信号通路及对人乳腺癌裸鼠移植瘤模型生长的实验研究

目的探讨应用小分子干扰RNA(small interfering RNA,siRNA)沉默抑癌基因LKB1对人乳腺癌细胞MDA-MB-231中Hedgehog信号通路相关因子的表达及人乳腺癌裸鼠移植瘤模型的肿瘤生长的影响。方法构建LKB1基因siRNA质粒LKB1-siRNA;建立LKB1表达抑制的MDA-MB-435细胞模型;裸鼠乳晕皮下接种,建立人乳腺癌裸鼠移植瘤动物模型;成瘤后,观察肿瘤体积变化、裸鼠生存时间;并用Western印迹法检测瘤组织中LKB1和Hedgehog信号通路中信号肽Shh、Sufu、膜受体Ptch、Smo、转录因子Gli1、Hip蛋白表达的变化。结果 LKB1-siRNA质粒组裸鼠的肿瘤体积明显增长(P<0.05);肿瘤内LKB1基因表达水平明显下降,而Hedgehog信号通路相关因子Shh、Gli1、Ptch、Smo的表达升高,Hedgehog信号通路抑制因子Sufu、Hip表达下降。结论 LKB1基因siRNA能够明显抑制人乳腺癌裸鼠移植模型的LKB1基因的表达,上调Hedgehog信号通路相关因子的表达,促进肿瘤生长。LKB1基因和Hedgehog信号通路在乳腺癌细胞中呈现负相关表达。     

Ａｄ-ＩＮＧ４抑制裸鼠人肝癌移植瘤生长的体内实验研究

目的　研究携带ＩＮＧ４基因的重组腺病毒（Ａｄ-ＩＮＧ４）对人肝癌细胞株ＳＭＭＣ-７７２１移植瘤生长的抑制作用及其潜在的分子机制。方法　将扩增的Ａｄ-ＩＮＧ４感染ＳＭＭＣ-７７２１细胞,Ｗｅｓｔｅｒｎｂｌｏｔ法检测Ａｄ-ＩＮＧ４在ＳＭＭＣ-７７２１细胞中的转录。用ＳＭＭＣ-７７２１细胞建立裸鼠人肝癌移植瘤模型,予Ａｄ-ＩＮＧ４（１×１０^９ｐｆｕ／ｍｌ）５０μｌ对移植瘤瘤体注射治疗,观察肿瘤生长变化;３周后处死裸鼠,摘除瘤体,称瘤重;免疫组化法检测ｐ２１、ＣＯＸ-２、Ｆａｓ、Ｂｃｌ-２、Ｂａx、Ｃａｓｐａｓｅ-３、ＶＥＧＦ、ＣＤ３４等因子的表达。结果　Ａｄ-ＩＮＧ４在ＳＭＭＣ-７７２１细胞中成功表达;Ａｄ-ＩＮＧ４对裸鼠人肝癌移植瘤有明显的生长抑制作用,Ａｄ-ＩＮＧ４组瘤体显著减小（Ｐ＜０.０１）,抑瘤率达４１.６４％;免疫组化检测显示,Ａｄ-ＩＮＧ４抑癌的分子机制可能与上调ｐ２１、Ｆａｓ、Ｂａｘ和Ｃａｓｐａｓｅ-３的表达及下调ＣＯＸ-２、Ｂｃｌ-２、ＶＥＧＦ和ＣＤ３４的表达有关。结论　Ａｄ-ＩＮＧ４能有效抑制ＳＭＭＣ-７７２１裸鼠人肝癌移植瘤的生长,其机制可能通过抑制肿瘤细胞生长、血管形成和激活细胞凋亡等多个途径共同发挥抑癌效应。     

ICOSL expressed in triple-negative breast cancer can induce Foxp3+ Treg cell differentiation and reverse p38 pathway activation

Inducible costimulator ligand (ICOSL) expressed on cancer cells has immunoregulatory functions in various malignancies. However, the role of ICOSL in triple-negative breast cancer (TNBC) remains unclear. In this study, the role and expression of ICOSL in TNBC were analyzed using the cBioPortal and GEPIA databases. Then the role of ICOSL in Foxp3+ Treg cell differentiation, reversal of p38 pathway activation and cell proliferation, migration and apoptosis was determined in vitro. Finally, the effect of ICOSL expression on TNBC progression was verified in a nude mouse model of TNBC. We here observed that ICOSL expression in TNBC was found to be related to relapse-free survival, and Treg abundance was positively correlated with ICOSL expression, as demonstrated by database analyses. In vitro experiments showed that ICOSL overexpression (OE) in MDA-MB-231 cells induced cocultured T cells to differentiate into Foxp3+ Treg cells and promoted secretion of the tumor-promoting factors IL-10 and IL-4. Furthermore, in vitro experiments showed that ICOSL reversed p38 phosphorylation and promoted the proliferation, invasion, and metastasis of MDA-MB-231 ICOSL-OE cells. Finally, tumor progression was found to be promoted by ICOSL expression in a TNBC nude mouse model. Together, ICOSL expression can enhance tumor cell growth by inducing Foxp3+ Treg cell differentiation and reversing p38 pathway activation in TNBC.     

Adenovirus-mediated ING4/IL-24 double tumor suppressor gene co-transfer enhances antitumor activity in human breast cancer cells

Cancer gene therapy represents a new and promising therapeutic modality for various types of cancer. Two or more anti-oncogenes carried by a single vector could theoretically improve treatment efficacy, reduce side-effects from vectors, and have a satisfactory clinical application prospect; however, this has seldom been studied in breast cancer. The inhibitor of growth?4 (ING4), as a member of the inhibitor of growth tumor suppressor family has potent inhibitory effects on a variety of tumors. Interleukin?24 (IL-24) has also shown broad spectrum and tumor-specific antitumor activities. In this study, we aimed to prove the enhanced antitumor activity of adenovirus-mediated ING4/IL-24 double tumor suppressor gene co-transfer in human breast cancer cells. We assessed the combined effect of the ING4/IL-24 bicistronic adenovirus (Ad-ING4-IL-24) in?vitro and in?vivo on MDA-MB-231 human breast cancer cells by detecting and comparing the apoptotic status in the bicistronic anti-oncogene group (Ad-ING4-IL-24) and in the ING4 or IL-24 single anti-oncogene groups, and also investigated the possible underlying mechanism. Our results showed that the bicistronic adenovirus-mediated ING4 and IL-24 co-expression induced additive growth suppression and apoptosis as well as an overlapping effect on the upregulation of p21, p27 and Bax, and the downregulation of Bcl-2 and survivin in MDA-MB?231 human breast cancer cells in?vitro or in?vivo. Moreover, Ad-ING4-IL-24 treatment additively reduced CD34 expression and the microvessel density in MDA-MB-231 xenografted tumors in athymic nude mice, which correlated with the decreased expression of the vascular endothelial growth factor. The enhanced antitumor activity on breast cancer elicited by Ad-ING4-IL-24 was closely associated with the activation of the apoptotic pathways and the additive inhibition of tumor angiogenesis.     

CIP2A is a target of bortezomib in human triple negative breast cancer cells

Introduction

Triple negative breast cancer (TNBC) is very aggressive and currently has no specific therapeutic targets, such as hormone receptors or human epidermal growth factor receptor type 2 (HER2); therefore, prognosis is poor. Bortezomib, a proteasome inhibitor, may exert efficacy in TNBC through its multiple cellular effects. Here, we tested the efficacy of bortezomib and examined the drug mechanism in breast cancer cells.

Methods

Five breast cancer cell lines: TNBC HCC-1937, MDA-MB-231, and MDA-MB-468; HER2-overexpressing MDA-MB-453; and estrogen receptor positive MCF-7 were used for in vitro studies. Apoptosis was examined by both flow cytometry and Western Blot. Signal transduction pathways in cells were assessed by Western Blot. Gene silencing was done by small interfering RNA (siRNA). In vivo efficacy of bortezomib was tested in nude mice with breast cancer xenografts. Immunohistochemical study was performed on tumor tissues from patients with TNBC.

Results

Bortezomib induced significant apoptosis, which was independent of its proteasome inhibition, in the three TNBC cell lines, but not in MDA-MB-453 or MCF-7 cells. Furthermore, cancerous inhibitor of protein phosphatase 2A (CIP2A), a cellular inhibitor of protein phosphatase 2A (PP2A), mediated the apoptotic effect of bortezomib. We showed that bortezomib inhibited CIP2A in association with p-Akt downregulation in a dose- and time-dependent manner in all sensitive TNBC cells, whereas no alterations in CIP2A expression and p-Akt were noted in bortezomib-resistant cells. Overexpression of CIP2A upregulated p-Akt and protected MDA-MB-231 and MDA-MB-468 cells from bortezomib-induced apoptosis, whereas silencing CIP2A by siRNA overcame the resistance to bortezomib-induced apoptosis in MCF-7 cells. In addition, bortezomib downregulated CIP2A mRNA but did not affect the degradation of CIP2A protein. Furthermore, bortezomib exerted in vivo antitumor activity in HCC-1937 xenografted tumors, but not in MCF-7 tumors. Bortezomib downregulated CIP2A expression in the HCC-1937 tumors but not in the MCF-7 tumors. Importantly, CIP2A expression is readily detectable in tumor samples from TNBC patients.

Conclusions

CIP2A is a major determinant mediating bortezomib-induced apoptosis in TNBC cells. CIP2A may thus be a potential therapeutic target in TNBC.