Hedgehog信号通路与LKB1基因在乳腺癌中的达及其相关性研究

Hedgehog信号通路在乳腺癌中过度激活,LKB1是抑癌基因,有抑制乳腺癌增殖的功能.LKB1过表达可调控Hedgehog信号通路的靶基因CyclinD1系列基因的表达,同时研究发现Hedgehog信号通路中PKA基因起重要作用,其激活与cAMP状态有关,而LKB1基因能影响cAMP的状态.因此,LKB1基因与Hed...     

乳腺癌中Hedgehog信号通路的表达及其与LKB1基因相关性的研究

目的：探讨Hedgehog（Hh）信号通路主要蛋白在乳腺癌中的表达及其与LKB1基因的相关性,以及与临床病理特征、预后的关系。方法：采用免疫组化方法检测75例人乳腺癌标本中Hh信号通路主要蛋白（Shh、Smo、Sufu、Gli1、Ptch）及LKB1基因的表达,分析二者相关性,并分析Hh信号通路的表达与临床病理特征及预后的关系。结果：在75例乳腺癌样本中,阳性表达Shh、Gli1、Smo、Ptch、Sufu、LKB1分别为69（92.0%）、58（77.3%）、65（86.7%）、50（66.7%）、34（45.3%）、33（44.0%）,而在其相邻的正常乳腺上皮不表达或低表达。Hh信号通路与LKB1的表达呈负相关;Hh信号通路的表达情况与患者年龄、淋巴结转移情况、分子分型具有一定的相关性,且高表达的患者预后较差。结论：Hh信号通路在乳腺癌中过度激活,与临床病理特征及预后相关,并与LKB1基因的表达呈负相关,两者之间的相互作用对乳腺癌的诊治及预后可能有重要影响。     

乳腺癌中CXCR4的表达及其与Hedgehog信号通路的相关性

目的 检测乳腺癌组织中CXCR4及Smoothened (Smo)、Patched (Ptch)的表达,对CXCR4表达的临床意义进行分析,并评价CXCR4与Smo、Ptch之间的相关性.方法 以免疫组织化学染色法检测124例乳腺癌组织中CXCR4、Smo、Ptch的表达情况,并对其结果进行分析.结果 乳腺癌组织中CXCR4阳性表达率为66.9％,CXCR4与乳腺癌淋巴结转移呈正相关(r=0.181,P=0.044);Smo、Ptch阳性表达率分别为58.9％和64.5％,与CXCR4表达呈正相关(r=0.189,P=0.036;r=0.230,P=0.0l0).结论 CXCR4的表达与乳腺癌淋巴结转移有关,与Smo、Ptch表达呈正相关,当其与Hedgehog信号通路同时表达时或许与乳腺癌的复发风险增高相关.     

RNA干扰抑制MTA 1的表达对乳腺癌细胞MDA-MB-231增殖的影响

目的:探讨通过RNA干扰技术抑制MTA1的表达及对乳腺癌细胞MDA-MB-231增殖和细胞周期的影响。方法:建立3种稳定表达靶向MTA1的shRNA的MDA-MB-231细胞系。通过反转录-聚合酶链反应(reverse transeription-polymerase chain reaction,RT-PCR)和免疫组化法验证基因表达的抑制效果;采用细胞计数法及噻唑蓝(thiazolylblue,MTT)法检测细胞的增殖能力;流式细胞仪分析细胞周期。结果:MTA1基因被抑制后,其mRNA表达明显下降,RT-PCR结果显示,稳定转染3种重组质粒后,MTA1mRNA水平较对照组分别下调了70.07%、82.40%和63.44%;同时,MDA-MB-231细胞的生长明显受抑制,与对照组细胞相比,细胞计数示细胞数目明显减低;MTT分析示细胞增殖下降,流式细胞分析示细胞周期阻滞在G0/G1期。结论:在MDA-MB-231细胞中,抑制MTA1的表达可有效抑制细胞生长并导致细胞周期的阻滞;利用RNA干扰技术抑制MTA1的表达可能会成为一种有效的乳腺癌基因治疗手段。     

Sonic Hedgehog信号通路与乳腺癌抑癌基因LKB1的相互影响

目的：研究环靶明（cyclopamine）抑制Sonic Hedgehog（SHH）信号通路后,转染LKB1基因的乳癌细胞的凋亡、周期及信号通路相关基因表达的改变。方法：抑癌基因LKB1转染人乳腺癌细胞MDA-MB-231,分MDA-MB-231组（231组）和转染LKB1基因的MDA-MB-231（LKB1组）两组,每组分别采用0,5×10-6mol/L,10×10-6mol/L,20×10-6mol/L 4种浓度的环靶明处理细胞,各小组细胞分别采用流式细胞仪检测细胞凋亡和周期,用RT-PCR法和Western blot法检测Sonic Hedgehog信号通路相关基因Shh、Smo、Ptch、Sufu、Hip及LKB1的mRNA和蛋白表达水平。结果 ：在LKB1组和231组中,各小组细胞的凋亡率变化与Sonic Hedgehog相关基因Shh、Smo表达变化一致,随环靶明浓度增大凋亡率增加、基因表达受抑制,在环靶明浓度达10×10-6mol/L时变化最明显,且LKB1组较231组的变化更为明显。在231组中,各小组细胞周期变化与Sonic Hedgehog相关抑制基因Sufu、Hip表达变化一致。而在LKB1组中,各小组细胞周期与抑制基因Sufu、Hip表达变化均无明显差异。在231组中,各小组抑癌基因LKB1的表达随药物浓度增加渐增强。Ptch表达在两组均无明显变化。结论 ：抑癌基因LKB1可协同Sonic Hedgehog信号通路抑制剂环靶明促进乳腺癌细胞凋亡,调控细胞周期,推测其机制可能是通过如上信号通路相关基因表达变化而实现。信号通路抑制剂环靶明可提高乳腺癌细胞抑癌基因LKB1的表达,推测此也是信号通路抑制剂降低癌细胞活性机制之一。     

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。     

JNK信号通路介导ghrelin对乳腺癌MDA-MB-231细胞耐药蛋白表达的影响

目的探讨ghrelin调控c-Jun氨基末端激酶(c-Jun N-terminal kinase,JNK)信号转导通路对乳腺癌细胞P-糖蛋白表达的影响。方法培养人乳腺癌MDA-MB-231细胞,分别加入生长激素释放肽(ghrelin,100 nmol/L,干预72小时)、多柔比星(0.8 mg/L,干预72小时)、ghrelin联合多柔比星(ghrelin 100 nmol/L,多柔比星0.8 mg/L,干预72小时)。采用MTT方法检测细胞增殖,Western blot法检测细胞JNK、P-糖蛋白(P-glycoprotein,P-gp)的表达及p-JNK水平。结果 MTT检测显示,人乳腺癌MDA-MB-231细胞在ghrelin的干预下增殖(P<0.01),存活率在多柔比星的干预下降低(P<0.01),ghrelin联合多柔比星能够抑制多柔比星对MDA-MB-231细胞的杀伤作用(P<0.01)。ghrelin组JNK表达及p-JNK水平上升(均P<0.01),且P-gp蛋白表达上升(P<0.05);多柔比星组JNK表达及p-JNK水平下降(均P<0.01);ghrelin联合多柔比星较多柔比星组JNK表达及p-JNK水平增加,且P-gp表达明显上升(均P<0.05)。结论 ghrelin激活JNK信号通路干预乳腺癌细胞P-gp表达增加从而抑制多柔比星诱导乳腺癌细胞凋亡。     

三阴性乳腺癌发生机制的信号传导通路

三阴性乳腺癌(TNBC)具有易转移与侵袭等特点，预后差，目前以化疗为主。TNBC的发生与多种信号通路有关，信号通路的激活参与了肿瘤发生、发展、侵袭和转移等多个环节。准确识别TNBC靶向治疗的有效靶点是临床科研中亟待解决的问题。因此，研究TNBC相关的信号通路对提高患者生存率具有重要意义。笔者着重介绍几种与TNBC发生机制相关的主要信号传导通路。     

鞣花酸对乳腺癌细胞MDA-MB-231增殖及SDF1α/CXCR4信号通路的影响

目的 探讨鞣花酸对乳腺癌细胞MDA-MB-231的增殖侵袭转移的作用.方法 采用0（对照）、6、12 μg/ml鞣花酸培养液分别处理乳腺癌细胞MDA-MB-231,分别于培养后24、48、72 h计数MDA-MB-231细胞数.细胞趋化实验观察鞣花酸对MDA-MB-231细胞趋化运动的影响,Western Blot 观察鞣花酸对乳腺癌细胞MDA-MB-231中SDF-1α信号通路激活的抑制作用.数据分析采用重复测量的方差分析,两两比较采用SNK-q分析方法.结果 与对照组比较,6、12 μg/ml鞣花酸处理组在24、48、72 h的细胞计数显著降低.重复测量的方差分析结果提示分组比较（F=4875.56,P=0.00）及三个时间点间比较（F=670.73,P=0.00）差异有统计学意义,而分组与时间有交互作用（F=122.92,P=0.00）,表明鞣花酸对乳腺癌MDA-MB-231细胞增殖有显著抑制作用.乳腺癌细胞趋化运动实验提示各组乳腺癌细胞的趋化数分别为（14.00±1.00）＆#215;105/ml、（7.70±0.58）＆#215;105/ml、（3.00±1.00）＆#215;105/ml,差异有统计学意义（F=117.57,P=0.00）.Western Blot结果显示鞣花酸明显抑制CXCR4表达及SDF1α/CXCR4对乳腺癌细胞AKT信号通路的激活.结论 鞣花酸可抑制乳腺癌MDA-MB-231细胞增殖,SDF1α/CXCR4介导的细胞趋化运动及其SDF1α/CXCR4信号通路激活,在预防乳腺癌复发及转移中可能有潜在价值.     

Celecoxib下调NF-kB信号通路促进人乳腺癌MDA-MB-231细胞凋亡的体外研究

背景与目的:Celecoxib可以抑制多种肿瘤细胞增殖、诱导其凋亡,但具体的作用机制尚不明确.本研究探讨Celecoxib是否通过阻断NF-kB信号途径诱导人乳腺癌MDA-MB-231细胞的凋亡.方法:RT-PCR法检测MDA-MB-231细胞中COX-2 mRNA的表达.MTT法检测Celecoxib、PGE2与Celecoxib联合应用对MDA-MB-231细胞增殖的影响.流式细胞术检测细胞周期、凋亡的变化.Westernblot法检测0、40、80、120 μmol/L Celecoxib作用MDA-MB-231细胞24 h后细胞中Caspase-3、p65蛋白的表达变化.结果:RT-PCR检测显示MDA-MB-231细胞中COX-2 mRNA的表达随着Celecoxib浓度的增加而逐渐降低.Celecoxib能够显著地抑制MDA-MB-231细胞增殖(P<0.05),但Celecoxib联合PGE2与单独应用Celecoxib对细胞增殖的影响差异无统计学意义(P>0.05).流式细胞术结果显示Celecoxib可使MDA-MB-231细胞阻滞在G0/G1期,并可诱发细胞凋亡.Western blot检测发现Celecoxib作用MDA-MB-231细胞24 h,随着Celecoxib浓度的增加,Caspase-3蛋白表达增加,P65蛋白表达下调.结论:Celecoxib可以通过下调P65蛋白的表达从而阻断NF-kB信号途径,抑制人乳腺癌MDA-MB-231细胞增殖,促进其凋亡.     

伊班膦酸钠对人乳腺癌细胞系MDA-MB-231、MDA-MB-453的体外生长抑制作用

目的：研究伊班膦酸钠（IBN）对体外培养的人乳腺癌细胞MDA—MB-231、MDA—MB-453细胞生长增殖的影响及其潜在的作用机制。方法：采用MTT法检测不同浓度的IBN、及相同浓度不同作用时间的IBN对MDA—MB-231、MDA—MB-453两类不同的人乳腺癌细胞系生长增殖的影响；应用流式细胞仪检测不同浓度IBN作用下，MDA—MB-231、MDA—MB-453细胞细胞周期的变化。结果：在（10～100）μg／ml的浓度范围内，IBN对MDA—MB-231、MDA—MB-453细胞生长增殖均有抑制作用（P〈0．01），抑制效果与IBN浓度呈剂量依赖性，与其作用时间呈时间依赖性；IBN可使细胞明显阻滞于S期，G2／M期细胞比例则明显减少，且呈剂量依赖趋势。结论：在（10～100）μg／ml的浓度范围内，IBN对体外生长的人乳腺癌细胞MDA—MB-231、MDA—MB-453产生剂量、时间依赖性的抑制作用，其机制可能与其将细胞阻滞在DNA合成的S期，阻碍肿瘤细胞分裂增殖有关。     

WNT signaling enhances breast cancer cell motility and blockade of the WNT pathway by sFRP1 suppresses MDA-MB-231 xenograft growth

Introduction  

In breast cancer, deregulation of the WNT signaling pathway occurs by autocrine mechanisms. WNT ligands and Frizzled receptors are coexpressed in primary breast tumors and cancer cell lines. Moreover, many breast tumors show hypermethylation of the secreted Frizzled-related protein 1 (sFRP1) promoter region, causing low expression of this WNT antagonist. We have previously shown that the WNT pathway influences proliferation of breast cancer cell lines via activation of canonical signaling and epidermal growth factor receptor transactivation, and that interference with WNT signaling reduces proliferation. Here we examine the role of WNT signaling in breast tumor cell migration and on xenograft outgrowth.     

RNA干扰对MDA-MB-231乳腺癌细胞株骨保护素基因表达的抑制作用

目的 构建针对骨保护素（OPG）基因的一个载体编码三条短发夹RNA（shRNA）的真核表达质粒,观察其对MDA—MB-231乳腺癌细胞株OPG表达的抑制作用。方法选择3个针对OPG基因的RNA干扰（RNAi）位点,分别设计合成3对编码相应shRNA的DNA单链,每对单链连接形成双链后分别与线性化载体pGenesil-1．1、pGenesil-1．2、pGenesil-1．3连接形成pGenesil-1．1-shRNAl、pGenesil-1．2-shRNA2、pGenesil-1．3-shRNA3,对以上重组载体反复酶切连接,构建成重组质pGenesil—1．1—1．2-1．3-shRNA1-shRNA2-shRNA3,酶切鉴定和测序无误后,将该质粒转染MDA—MB一231细胞,以G418加压筛选,对转染细胞行单克隆化,稳定转染细胞行RT—PCR和Westernblot检测,确定其对OPG基因表达抑制作用。统计分析采用单因素方差分析和SLD分析法。结果成功构建了pGenesil-1．1—1．2-1．3-shRNA1-shRNA2-shRNA3重组质粒;以该质粒稳定转染MDA—MB-231细胞后其OPGmRNA和蛋白表达均较对照差异有统计学意义（P〈0．05）,RNAi对OPGmRNA和蛋白的表达抑制率分别为91％和73％。结论本研究构建了针对OPG的一个载体编码3条shRNA的真核表达质粒,通过RNAi抑制了MDA—MB-231细胞OPG基因表达,为进一步深入探讨肿瘤细胞自身OPG表达在乳腺癌骨转移发生发展中的作用提供了相关实验基础。     

LKB1 signaling in advancing cell differentiation

The Peutz-Jeghers syndrome (PJS) culprit kinase LKB1 phosphorylates and activates multiple intracellular kinases regulating cell metabolism and polarity. The relevance of each of these pathways is highly variable depending on the tissue type, but typically represents functions of differentiated cells. These include formation and maintenance of specialized cell compartments in nerve axons, swift refunneling of metabolites and restructuring of cell architecture in response to environmental cues in committed lymphocytes, and ensuring energy-efficient oxygen-based energy expenditure. Such features are often lost or reduced in cancer cells, and indeed LKB1 defects in PJS-associated and sporadic cancers and even the benign PJS polyps lead to differentiation defects, including expansion of partially differentiated epithelial cells in PJS polyps and epithelial-to-mesenchymal transition in carcinomas. This review focuses on the involvement of LKB1 in the differentiation of epithelial, mesenchymal, hematopoietic and germinal lineages.     

Role and mechanism of hypoxia-inducible factor-1 in cell growth and apoptosis of breast cancer cell line MDA-MB-231

The role of hypoxia-inducible factor-1 (HIF-1) in tumor development and progression is well-established but its effect on tumor growth remains controversial. The present study investigated the effect of HIF-1 on tumor growth using the estrogen receptor-negative breast cancer cell line, MDA-MB-231. Using Western blotting, we detected a higher level of HIF-1α protein in MDA-MB-231 cells than in any other breast cancer cell lines analyzed, and this was accompanied by a more rapid growth pattern. Interruption of HIF-1α expression using small interference RNA (siRNA) significantly suppressed cell growth and increased apoptosis, but the cell cycle was not affected. Activated fragments with increased caspase 3 activity and a mobility shift of B cell lymphoma (Bcl-2) were also detected in cells treated with HIF-1α siRNA. HIF-1 allows breast cancer cells to grow under long-term serum deprivation by inactivation of the caspase cascade and thus inhibition of apoptosis. Blocking HIF-1α protein resulted in loss of Bcl-2 function, which may contribute to the activation of the caspase cascade.     

Gonadotropin-releasing hormone gene expression in MDA-MB-231 and ZR-75-1 breast carcinoma cell lines

The presence of gonadotropin-releasing hormone (GnRH)-binding sites in human breast carcinomas and breast tumor cell lines as well as the demonstration of the inhibitory effects of GnRH analogues on the growth of these cells raised the possibility that GnRH is produced locally by breast tumor cells themselves. Immunoreactive GnRH was shown to be present in acetic acid extracts of cultured MDA-MB-231 and ZR-75-1 breast carcinoma cells. These extracts were separated by high-performance liquid chromatography and were analyzed by means of region-specific antisera with differing GnRH sequence specificities. A peak of GnRH which coeluted with synthetic mammalian GnRH in 2 different high-performance liquid chromatography systems was similarly detected by antisera directed at the NH2 terminus, at the middle portion and at the N and COOH termini together. The GnRH gene is expressed in these breast tumor lines, as determined by S1 nuclease protection assay, oligonucleotide primer extension studies, and polymerase chain reaction amplification of complementary DNA using oligonucleotides. The primer extension studies indicate that several forms of mRNA are present. The predominant form corresponds to the excision of intron I and the use of a start site about 60 bases upstream of intron I as in the human hypothalamus. Less usage is made of other start sites further upstream. Much larger species of mRNA were also present and correspond to the retention of intron I as in human placenta. The demonstration of GnRH gene expression and the presence of immunoreactive GnRH in mammary carcinoma cells known to have GnRH-binding sites and to be affected by GnRH analogues suggests that GnRH may serve an autocrine regulatory role.     

Inhibition of MDA-MB-231 cell cycle progression and cell proliferation by C-2-substituted oestradiol mono- and bis-3-O-sulphamates

A natural metabolite of oestradiol (E2), 2-methoxyoestradiol (2-MeOE2), exerts both antitumour and antiangiogenic effects. 2-MeOE2 is currently in clinical trials for the treatment of a variety of cancers. We have previously shown that a number of sulphamoylated analogues of 2-MeOE2 possess enhanced potency and bioavailability with respect to 2-MeOE2. In our study, the effects of C-2-substituted E2 derivatives, with sulphamoylation at the C-3 and/or C-17 position, on ERalpha -ve MDA-MB-231 breast cancer cells were evaluated. Sulphamoylated derivatives were potent inhibitors of cell proliferation, and these effects were irreversible when compared to growth inhibitory effects induced by 2-MeOE2. Cell cycle analysis suggested that these derivatives caused cells to arrest at the G2-M phase of the cell cycle. Sulphamoylated analogues suppressed the clonogenic potential of MDA-MB-231 cells and also their growth on Matrigel culture substratum. Immunofluorescence studies showed fragmented nuclear bodies and an abnormal microtubule cytoskeleton in cells exposed to one of the potent compounds, 2-MeOE2-bis-sulphamate. In addition, these analogues induced phosphorylation of BCL-2, a protein considered to be the guardian of microtubule integrity. In each of the assays, the sulphamoylated derivatives were at least 10-fold more potent than the parent compound 2-MeOE2. In view of the enhanced potencies associated with sulphamoylated E2 derivatives in ERalpha -ve cells, these analogues should hold considerable therapeutic potential for the treatment of hormone-independent breast cancers.     

黄芩素对人乳腺癌MDA-MB-231细胞株SATB1表达的影响(英文)

Baicalein had been proved to have anti-cancer activity in vitro and in vivo, including the inhibition of malignant proliferation, migration, adhesion and invasion of many kinds of cancer cells. The special AT-rich sequence binding protein 1 （SATB1） is a tissue-specific expression of nuclear matrix-binding protein and is reported to be a breast cancer ＂gene group organizer＂. Previous studies have shown that SATB1 is involved in the growth, metastasis and prognosis of breast cancer. The present study was aimed to investigate whether baicalein inhibits the proliferation and migration of MDA-MB-231 human breast cancer cells through down-regulation of the SATB1 expression. Methods： MDA-MB-231 cells were treated for 24 h, 48 h and 72 h with various concentrations of baicalein （0, 5, 10, 20, 40 and 80 pM） respectively. Then, the proliferation and migration of MDA-MB-231 cells following treatment with baicalein were determined using colorimetric 3-（4, 5-dimethylthia- zol-2-yl） 2, 5-diphenyltetrazolium bromide （MTT） and wound healing assays. Thereafter, western blot analysis was performed to detect the changes of SATB1 protein expression in MDA-MB-231 cells. Results： Along with the prolongation of time and increase of drug concentration, inhibitory effect of baicalein on proliferation and migration of MDA-MB-231 cells gradually in- creased, in a time.- and dose- dependent manner （P 〈 0.05）. Meanwhile, after treated with baicalein in different concentrations for 48 h, the level of SATB1 protein expression of MDA-MB-231 cells decreased obviously, in a dose-dependent manner （P 〈 0.05）. Conclusion： Baicalein inhibits breast cancer cell proliferation and suppresses its invasion and metastasis by reducing cell migration possibly by down-regulation of the SATB1 protein expression, indicating that baicalein is a potential therapeutic agent for human breast cancer.     

The effect of baicalein on the expression of SATB1 in MDA-MB-231 cells

Objective:Baicalein had been proved to have anti-cancer activity in vitro and in vivo, including the inhibition of malignant proliferation, migration, adhesion and invasion of many kinds of cancer cel ...     

Defining MAP3 kinases required for MDA-MB-231 cell tumor growth and metastasis

Analysis of patient tumors suggests that multiple MAP3 kinases (MAP3Ks) are critical for growth and metastasis of cancer cells. MAP3Ks selectively control the activation of extracellular signal-regulated kinase 1/2 (ERK1/2), Jun N-terminal kinase (JNK), p38 and ERK5 in response to receptor tyrosine kinases and GTPases. We used MDA-MB-231 cells because of their ability to metastasize from the breast fat pad to distant lymph nodes for an orthotopic xenograft model to screen the function of seven MAP3Ks in controlling tumor growth and metastasis. Stable short hairpin RNA (shRNA) knockdown was used to inhibit the expression of each of the seven MAP3Ks, which were selected for their differential regulation of the MAPK network. The screen identified two MAP3Ks, MEKK2 and MLK3, whose shRNA knockdown caused significant inhibition of both tumor growth and metastasis. Neither MEKK2 nor MLK3 have been previously shown to regulate tumor growth and metastasis in vivo. These results demonstrated that MAP3Ks, which differentially activate JNK, p38 and ERK5, are necessary for xenograft tumor growth and metastasis of MDA-MB-231 tumors. The requirement for MAP3Ks signaling through multiple MAPK pathways explains why several members of the MAPK network are activated in cancer. MEKK2 was required for epidermal growth factor receptor and Her2/Neu activation of ERK5, with ERK5 being required for metastasis. Loss of MLK3 expression increased mitotic infidelity and apoptosis in vitro. Knockdown of MEKK2 and MLK3 resulted in increased apoptosis in orthotopic xenografts relative to control tumors in mice, inhibiting both tumor growth and metastasis; MEKK2 and MLK3 represent untargeted kinases in tumor biology for potential therapeutic development.