Flavonoid baicalein suppresses adhesion,migration and invasion of MDA-MB-231 human breast cancer cells

Baicalein is a widely used Chinese herbal medicine that has been used historically in anti-inflammatory and anti-cancer therapy. However, the molecular mechanism of its anti-cancer activity remains poorly understood and warrants further investigations. The purpose of this study is to verify the activity of baicalein to inhibit the invasion of MDA-MB-231 human breast cancer cells. The results indicated that baicalein suppressed MDA-MB-231 cell adhesion to fibronectin-coated substrate, wound healing migration and invasion through the Matrigel in a concentration-dependent manner. Western blot and gelatin zymography analysis showed that baicalein significantly inhibited the expression and secretion of matrix metalloproteinases 2/9 (MMP-2/9) in MDA-MB-231 cells. Additionally, treatment of MDA-MB-231 cells with baicalein down-regulated the expression of MMP-2/9 involved mitogen-activated protein kinases (MAPK) signaling pathway. Taken together, baicalein had potential to suppress the adhesion, migration and invasion of MDA-MB-231 cancer cells in vitro and it could serve as a promising drug for the treatment of cancer metastasis.     

Anti-Axl monoclonal antibodies attenuate the migration of MDA-MB-231 breast cancer cells

The receptor tyrosine kinase, anexelekto (Axl) is involved in tumor cell growth, migration and invasion, and has been associated with chemotherapy resistance, which makes it an attractive target for cancer therapy. In total, six Axl-targeted monoclonal antibodies (mAbs) and two antibody-drug conjugates have been reported in the last 10 years, which have been shown to have bioactivity in inhibiting tumor cell proliferation and migration. The Axl external cell domain (Axl^−ECD), consisting of 426 amino acids, has always been used as an antigen in the screening process for all six of these Axl-targeted mAbs. However, the Axl functional domain, which interacts with its natural ligand, growth arrest-specific protein 6 (Gas6), is only a small part of the Axl^−ECD. Antibodies targeting the Axl functional domain may efficiently block Gas6-Axl binding and attenuate its downstream signals and activities. To the best of our knowledge, no mAbs targeting the Axl functional domain have been reported. In the present study, a major Axl functional domain interacting with Gas6 was determined using bioinformatics and structural biology methods. In MDA-MB-231 breast cancer cell assays, anti-Axl mAbs targeting this relatively specific Axl functional domain almost completely neutralized the stimulation of Gas6 in both Axl phosphorylation and cell migration assays, and showed similar activity to the positive control drug R428 (a small molecular tyrosine kinase inhibitor of Axl currently in phase II clinical trials) in the cell migration assay. Given the important role of Axl in tumor development and chemotherapy resistance, Axl-targeted mAbs could be used to inhibit tumor cells directly, as well as reduce the development of chemotherapy resistance by blocking Axl activity. The application of Axl-targeted mAbs combined with chemotherapy provides a promising treatment strategy for patients with tumors, particularly those with triple-negative breast cancer, for whom no targeted therapy is currently available.     

siRNA 沉默Sema 4D对乳腺癌MDA-MB-231细胞增殖及迁移的影响

目的： 观察siRNA沉默信号素 4D(semaphorin 4D, Sema 4D）对乳腺癌MDA-MB-231细胞增殖、迁移的影响。方法： 构建靶向Sema 4D基因的siRNA,脂质体法转染MDA-MB-231细胞系,通过实时荧光定量-PCR、Western blotting检测干扰效率,筛选有效序列。siRNA有效干扰MDA-MB-231细胞Sema 4D表达后,CCK-8法及Transwell迁移实验检测细胞增殖及迁移能力的变化。结果：Sema 4D siRNA转染MDA-MB-231细胞后Sema 4D的（mRNA及蛋白）表达水平明显下降（P<0.05）,其中以siRNA-C最明显（P<0.05）;与空白、阴性对照组相比,siRNA-C沉默MDA-MB-231细胞Sema 4D表达可明显抑制MDA-MB-231细胞增殖（均P<0.05）,同时明显减弱细胞的迁移能力\[穿膜细胞数：（105.60±12.07） vs（196.20±9.04）、（186.40±6.69）个,均P<0.05\]。结论： siRNA沉默Sema 4D可抑制MDA-MB-231细胞增殖,并抑制细胞迁移,可作为乳腺癌基因治疗的潜在位点。     

金雀异黄素诱导乳腺癌MDA-MB-231细胞凋亡的研究

目的 探讨金雀异黄素（genistein,GEN）诱导乳腺癌MDA-MB-231细胞凋亡的分子机制.方法 用0、5、10、20 μmol/L GEN处理MDA-MB-231 细胞24 h.采用CCK-8、Hoechst 33342染色和流式细胞仪测定不同浓度GEN对 MDA-MB-231细胞增殖和凋亡的影响.采用Western blotting检测不同浓度GEN处理前后MDA-MB-231细胞中Fas相关死亡域蛋白（FADD）、活性半胱天冬酶8（cleaved caspase-8）、Fas、FasL蛋白表达水平.采用实时RT-PCR分析不同浓度GEN处理前后MDA-MB-231细胞中Fas、FasL基因表达水平.多组均数比较采用方差齐性检验后进行单因素方差分析.结果 在GEN作用24 h后,0、5、10和20 μmol/L组对MDA-MB-231细胞增殖的抑制率分别为（3.00±1.41）%、（14.02±1.57）%、（27.5±1.52）%、（48.90±1.44）%.与0 μmol/L组相比,5、10和20 μmol/L组呈浓度依赖性增加（F=528.119,P=0.000）.两两比较显示：各浓度组之间差异均有统计学意义（P〈0.05）.0、5、10和20 μmol/L组诱导MDA-MB-231细胞的早期凋亡率分别为（3.40±0.40）%、（9.34±1.34）%、（19.26±0.93）%、（27.41±1.12）%.与0 μmol/L组相比,5、10和20 μmol/L组呈浓度依赖性增加（F=379.573,P=0.000）.两两比较显示：各浓度组之间差异均有统计学意义（P〈0.05）.Western blotting结果显示,与0 μmol/L组相比,其他浓度组经GEN处理的MDA-MB-231细胞FADD、cleaved caspase-8、FasL蛋白表达升高（F=368.621、456.744、419.129,P均=0.000）,Fas蛋白表达差异无统计学意义（F=0.800,P=0.528）;与10（μmol/L组相比,20 μmol/L组FasL蛋白表达降低有统计学意义（F=92.235,P=0.001）.实时RT-PCR结果显示,与0 μmol/L组相比,其他浓度组经GEN处理的MDA-MB-231细胞FasL mRNA表达升高（F=646.983,P=0.000）,Fas mRNA表达差异无统计学意义（F=1.556,P=0.274）;与10 μmol/L组相比,20 μmol/L组FasL mRNA表达降低有统计学意义（F=52.562,P=0.020）.结论 GEN通过上调Fas/FasL途径中FasL基因表达诱导乳腺癌MDA-MB-231细胞凋亡.     

Autocrine TGFbeta supports growth and survival of human breast cancer MDA-MB-231 cells

Using a cell model system established by ectopic expression of a soluble TGFbeta type III receptor (sRIII) containing the whole extracellular domain of the type III receptor in human breast cancer MDA-MB-231 cells, we observed that the expression of sRIII antagonized TGFbeta activity and inhibited both anchorage-dependent and anchorage-independent cell growth. Further studies revealed that sRIII expression induced apoptosis both in vitro and in vivo. Treatment with TGFbeta neutralizing antibodies or a recombinant human sRIII also induced apoptosis in the MDA-MB-231 parental cells, suggesting that the increased apoptosis after sRIII expression was specifically due to antagonization of autocrine TGFbeta signaling. Western blotting showed that sRIII clones had a higher PTEN expression level than the control cells did. Treatment with TGFbeta(1) decreased PTEN and inhibited apoptosis in sRIII cells to a level similar to that in the control cells. sRIII clones also showed a lower level of phosphorylated-Akt than the control cells, consistent with the inhibitory activity of PTEN on Akt activation. Treatment with LY294002, a specific inhibitor of Akt activator, phosphatidylinositol 3-kinase, also induced apoptosis in a dose dependent manner in the control cells. Our results suggest that autocrine TGFbeta signaling is necessary for the growth and survival of MDA-MB-231 cells.     

Requirement of p38 MAPK for a cell-death pathway triggered by vorinostat in MDA-MB-231 human breast cancer cells

Vorinostat is a histone deacetylase inhibitor that effectively suppresses cancer-cell proliferation by inducing cell-cycle arrest and/or apoptosis. We now show the involvement of p38 mitogen-activated protein kinase (MAPK) in the regulation of vorinostat-induced apoptosis in MDA-MB-231 human breast cancer cells. Vorinostat induced the hyperacetylation of histone H3, which correlated to apoptosis induction. Vorinostat-induced apoptosis occurred in parallel with the phosphorylation of p38 MAPK and the dephosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2). Knockdown of p38 MAPK prominently abrogated apoptosis induction and was accompanied by decreased caspase-3 cleavage. These findings support the notion that the activation of the p38 MAPK pathway followed by caspase-3 cleavage is responsible for vorinostat-induced apoptosis in MDA-MB-231 cells.     

环加氧酶-2 通过调控EMT促进乳腺癌MDA-MB-231 细胞的迁移和侵袭

[摘要] 目的：探讨环加氧酶-2（COX-2）在乳腺癌转移中的作用及其可能的机制。方法：收集从2015 年10 月至2018 年4 月在云南省肿瘤医院接受乳腺切除术的患者中获得的原发乳腺癌组织和脑转移乳腺癌组织临床病理样本共45 例,其中原发30 例、脑转移15 例。采用qPCR检测COX-2 在原位乳腺癌和脑转移乳腺癌组织中的表达。将COX-2 过表达重组病毒（LV6-COX2）或敲减COX-2 重组病毒（LV3-COX2 shRNA1、LV3-COX2 shRNA2）感染人乳腺癌MDA-MB-231 细胞并获得稳转细胞株后,CCK-8法检测COX-2 表达对MDA-MB-231 细胞增殖的影响,划痕实验和Transwell 法检测对MDA-MB-231 细胞迁移和侵袭的影响。qPCR和WB实验分析各组细胞中COX-2 mRNA和蛋白的表达水平,qPCR检测COX-2 表达对MDA-MB-231 细胞内EMT相关基因表达的影响。结果：COX-2 表达水平在脑转移乳腺癌患者组织中显著高于原位乳腺癌组织（P<0.01）;并且与乳腺癌患者肿瘤TMN分期有关。成功构建稳定过表达/敲减COX-2 的MDA-MB-231 细胞株。过表达COX-2 促进MDA-MB-231 细胞的迁移和侵袭（均P<0.01）,同时显著提高MMP2、MMP1、N-cadherin 和vimentin 的表达（均P<0.01）,但对细胞增殖无明显影响;而沉默COX-2 则有相反的作用,且可促进细胞增殖（P<0.05）。结论：COX-2 在脑转移乳腺癌组织中高表达,其可能通过调控EMT过程促进乳腺癌MDA-MB-231 细胞的迁移和侵袭。     

Hypoxia regulates stemness of breast cancer MDA-MB-231 cells

Human breast cancers include cancer stem cell populations as well as non-tumorigenic cancer cells. Breast cancer stem cells possess self-renewal capability and thus are the root cause of recurrence and metastasis of malignant tumors. Hypoxia is a fundamental pathological feature of solid tumor tissues and exerts a wide range of effects on the biological behavior of cancer cells. However, there is little information on the role of hypoxia in modulating the stemness of breast cancer cells. In the present study, we cultured MDA-MB-231 cells in a hypoxic gas mixture to simulate the hypoxic environment in tissues and to determine how hypoxia conditions could affect the cell proliferation, apoptosis, cytotoxicity, and colony-forming ability. Expression of the stem cell phenotype CD24^?CD44⁺ESA⁺ was analyzed to assess the effects of hypoxia on stemness transformation in MDA-MB-231 cells. Our results found that the cell toxicity of MDA-MB-231 cells was not affected by hypoxia. Hypoxia could slightly inhibit the growth of MDA-MB-231 cells, but the inhibitory effect is not significant when compared with normoxic control. Moreover, hypoxia significantly blocked the apoptosis in MDA-MB-231 cells (P < 0.05). The proportion of CD24^?CD44⁺ESA⁺ cells in MDA-MB-231 cells was increased greatly after they were treated with hypoxia, and cell colony-formation rate of MDA-MB-231 cells also increased significantly in hypoxia-treated cells. These results encourage the exploration of hypoxia as a mechanism which might not be underestimated in chemo-resistant breast cancer treatment.     

RNA干扰CXCR4表达抑制乳腺癌MDA-MB-231细胞的增殖、黏附和迁移

目的：构建CXC趋化因子受体4（CXC chemokine receptor 4, CXCR4）RNA干扰真核表达载体,研究其对人乳腺癌细胞MDA-MB-231增殖、黏附及迁移能力的抑制作用。方法：构建针对CXCR4的带发夹结构的小RNA干扰序列,并连接到pGCsi-U6-Neo-GFP载体中,转染293T细胞,筛选出干扰效率最高的表达载体。脂质体法转染MDA-MB-231细胞。利用CCK8法、细胞-基质黏附实验和划痕修复实验检测shRNA干扰CXCR4表达对MDA-MB-231细胞增殖、黏附和迁移能力的影响。结果：成功构建CXCR4-shRNA重组质粒,并转染293T细胞,利用RT-PCR及Western blotting检测发现CXCR4沉默效率最高可达81.3%。CXCR4-shRNA转染能显著抑制MDA-MB-231细胞的增殖(P<0.05)以及细胞与细胞外基质的黏附(P<005)。CXCR4-shRNA转染组MDA-MB-231细胞的迁移距离明显低于对照质粒组和空白对照组(P<0.01)。结论：CXCR4-shRNA干扰载体能特异性抑制CXCR4的表达,从而抑制乳腺癌MDA-MB-231细胞的增殖、黏附及迁移。     

Up-regulation of LOX-1 expression by TNF-alpha promotes trans-endothelial migration of MDA-MB-231 breast cancer cells

Adhesion of cancer cell to endothelial cells and the subsequent trans-endothelial migration are key steps in metastasis. However, the identities of the molecules mediating cancer cell/endothelial cell interaction are still not fully understood. In this study, we tested the hypothesis that lectin-like oxidized-low-density lipoprotein (oxLDL) receptor-1 (LOX-1), a key mediator of vascular inflammation and atherosclerosis expressed on endothelial cell surface, mediates breast cancer cell/endothelial cell interactions. We showed that up-regulation of endothelial LOX-1 by TNF-alpha promoted the adhesion and trans-endothelial migration of MDA-MB-231 breast cancer cells. Thus, endothelial LOX-1 could present a novel pathway in breast cancer metastasis.     

Role of LOXs and COX-2 on FAK activation and cell migration induced by linoleic acid in MDA-MB-231 breast cancer cells

Background

Epidemiological studies and animal models suggest a link between high levels of dietary fat intake and an increased risk of developing breast cancer. Particularly, free fatty acids (FFAs) are involved in several processes, including proliferation, migration and invasion, in breast cancer cells. Linoleic acid (LA) is a dietary n-6 polyunsaturated fatty acid that is known to induce proliferation and invasion in breast cancer cells. So far, however, the contribution of LA to focal adhesion kinase (FAK) activation and cell migration in breast cancer cells has not been studied.

Results

Here, we show that LA promotes FAK and Src activation, as well as cell migration, in MDA-MB-231 breast cancer cells. FAK activation and cell migration require Src, Gi/Go, COX-2 and LOXs activities, whereas both are independent of Δ6 desaturase activity. In addition, we show that cell migration requires FAK activity, whereas FAK activation requires Src activity, thus suggesting a reciprocal catalytic activation mechanism of FAK and Src.

Conclusions

In summary, our findings show that LA induces FAK activation and cell migration in MDA-MB-231 breast cancer cells.     

MDA-MB-231乳腺癌细胞特异性多肽的初步筛选

目的 利用噬菌体展示技术,从噬菌体随机十二肽库中筛选出能够特异性结合MDA-MB-231乳腺癌细胞的噬菌体克隆.方法 以人正常乳腺细胞为减性筛选细胞、MDA-MB-231乳腺癌细胞为靶细胞,对噬菌体随机十二肽库进行筛选,挑取富集后的阳性单克隆噬菌体,酶联免疫吸附试验（ELISA）及DAB染色鉴定阳性噬菌体的特异性及亲和力.结果 经过3轮筛选,噬菌体得到约113倍的富集,随机挑选11株单克隆噬菌体,ELISA显示8号噬菌体单克隆对乳腺癌细胞的亲和力是对照的6.5倍,DAB鉴定亦显示其对乳腺癌细胞的特异性及亲和力最高,命名为LK-8.结论 利用噬菌体筛选技术成功筛选出能够特异性结合MDA-MB-231乳腺癌细胞的特异性噬菌体单克隆LK-8,可为进一步合成特异性多肽用于早期诊断和靶向治疗乳腺癌奠定基础.     

Enhanced retinoid-induced apoptosis of MDA-MB-231 breast cancer cells by PKC inhibitors involves activation of ERK

Retinoids are vitamin A derivatives, which cause growth inhibition, differentiation and/or apoptosis in various cell types, including some breast cancer cells. In general, estrogen receptor (ER)-positive cells are retinoic acid (RA) sensitive, whereas ER-negative cells are resistant. In this report, we show that ER-negative MDA-MB-231 cells are strongly growth inhibited by retinoids in combination with a PKC inhibitor. While neither RA nor GF109203X (GF) has a significant growth inhibitory effect in these cells, RA+GF potently suppress proliferation. We found that RA+GF induce apoptosis, as shown by an increase in fragmented DNA, Annexin-V-positive cells and caspase-3 activation. Apoptosis was also induced by GF in combination with two synthetic retinoids. Expression of phosphorylated as well as total PKC was decreased by GF and this was potentiated by RA. In addition, treatment with GF caused a strong and sustained activation of ERK1/2 and p38-MAPK, as well as a weaker activation of JNK. Importantly, inhibition of ERK but not p38 or JNK suppressed apoptosis induced by RA+GF, indicating that activation of ERK is specifically required. In support of this novel finding, the ability of other PKC inhibitors to cause apoptosis in combination with RA correlates with ability to cause sustained activation of ERK.     

曲格列酮对人乳腺癌MDA-MB-231和MCF-7细胞株增殖影响的研究

目的:探讨过氧化物酶体增殖物激活受体γ(PPARγ)激动剂曲格列酮(TRG)对体外培养雌激素受体(ER)阴性乳腺癌MDA-MB-231细胞及ER+乳腺癌MCF-7细胞增殖的影响。方法:以不同浓度的TRG(0～50μmol/mL)分别处理体外培养的MDA-MB-231细胞和MCF-7细胞48h,MTT法检测细胞存活率;流式细胞术(FCM)检测细胞周期分布;蛋白质印迹法检测PPARγ和ER-α的表达。结果:MTT结果示TRG浓度≥5μmol/mL时MDA-MB-231细胞(P值分别为0.006、0.006、0.000和0.000)和MCF-7细胞(P值分别为0.007、0.006、0.004和0.001)的存活率降低。FCM检测结果表明,经TRG作用后肿瘤细胞主要集中在G1期。以上2种检测结果显示,MDA-MB-231细胞对TRG的敏感程度较MCF-7细胞高;蛋白质印迹法检测结果表明,TRG处理后的MDA-MB-231细胞中PPARγ蛋白的表达水平随药物浓度增加逐渐升高(相对强度分别为2.045、2.600和3.038),MCF-7细胞的ER-α表达水平则随药物浓度增加逐渐降低(相对强度分别为1.164、1.130和0.680)。结论:TRG对ER+和ER-乳腺癌细胞均有抑制作用,且ER-乳腺癌细胞对TRG更敏感。     

miR-21通过靶向PDCD4调控三阴性乳腺癌细胞的迁移和侵袭

目的： 研究miR-21在三阴性乳腺癌细胞MDA-MB-231中的表达，以及其是否通过调控PDCD4影响MDA-MB-231细胞的迁移和侵袭。方法： 采用实时定量PCR（qPCR）法检测MDA-MB-231细胞和正常乳腺细胞MCF-10A中miR-21和PDCD4 mRNA的表达。将MDA-MB-231细胞随机分为5组：空白对照组，转染miR-21模拟物组，模拟物对照组，转染miR-21抑制物组和抑制物对照组。采用Western blot法检测MDA-MB-231细胞PDCD4蛋白的表达；采用荧光素酶报告基因试剂盒检测转染不同载体后荧光强度的变化来判断miR-21的靶标；采用Transwell实验检测各组细胞的迁移和侵袭数目。结果： miR-21和PDCD4 mRNA在MDAMB-231细胞中的表达水平分别明显高于和低于MCF-10A细胞（P均 < 0.01）。过表达或抑制miR-21可调节PDCD4的表达水平。荧光素酶报告基因试剂盒检测结果显示miR-21可直接靶向调控PDCD4的表达。Transwell实验结果表明过表达miR-21表达能增强MDA-MB-231细胞的迁移和侵袭能力。结论： 在MDA-MB-231细胞中，miR-21通过靶向调控PDCD4表达影响细胞的迁移和侵袭。miR-21可能成为抑制三阴性乳腺癌迁移和侵袭的靶点。     

miR-21通过靶向PDCD4调控三阴性乳腺癌细胞的迁移和侵袭

目的： 研究miR-21在三阴性乳腺癌细胞MDA-MB-231中的表达,以及其是否通过调控PDCD4影响MDA-MB-231细胞的迁移和侵袭。方法： 采用实时定量PCR（qPCR）法检测MDA-MB-231细胞和正常乳腺细胞MCF-10A中miR-21和PDCD4 mRNA的表达。将MDA-MB-231细胞随机分为5组：空白对照组,转染miR-21模拟物组,模拟物对照组,转染miR-21抑制物组和抑制物对照组。采用Western blot法检测MDA-MB-231细胞PDCD4蛋白的表达;采用荧光素酶报告基因试剂盒检测转染不同载体后荧光强度的变化来判断miR-21的靶标;采用Transwell实验检测各组细胞的迁移和侵袭数目。结果： miR-21和PDCD4 mRNA在MDAMB-231细胞中的表达水平分别明显高于和低于MCF-10A细胞（P均 < 0.01）。过表达或抑制miR-21可调节PDCD4的表达水平。荧光素酶报告基因试剂盒检测结果显示miR-21可直接靶向调控PDCD4的表达。Transwell实验结果表明过表达miR-21表达能增强MDA-MB-231细胞的迁移和侵袭能力。结论： 在MDA-MB-231细胞中,miR-21通过靶向调控PDCD4表达影响细胞的迁移和侵袭。miR-21可能成为抑制三阴性乳腺癌迁移和侵袭的靶点。     

防己诺林碱诱导人乳腺癌细胞MDA-MB-231凋亡的作用机制

目的 探讨防己诺林碱(FAN)对三阴性乳腺癌(TNBC)的抗肿瘤机制.方法 体外细胞培养人乳腺癌细胞MDA-MB-231,Alamar-Blue法检测FAN对人乳腺癌细胞MDA-MB-231的半抑制浓度(IC50);6孔板检测细胞迁移情况;细胞流式技术检测细胞凋亡情况;Western Blot检测磷脂酰肌醇-3羟基激酶(PI3K)、蛋白激酶B(AKT)、哺乳类动物雷帕霉素靶蛋白(mTOR)及磷酸化PI3K、AKT、mTOR蛋白表达.结果 FAN可抑制人乳腺癌细胞MDA-MB-231的活力(IC50为6.25μmol/L),抑制人乳腺癌细胞MDA-MB-231的迁移能力,且随着FAN浓度升高,抑制作用明显.FAN可以诱导人乳腺癌细胞MDA-MB-231凋亡,且随着FAN浓度升高,细胞凋亡率增高,同时FAN还可以下调PI3K、AKT、mTOR及磷酸化PI3K、AKT、mTOR蛋白的表达,随药物浓度的升高,其蛋白表达降低.结论 FAN可通过下调TNBC MDA-MB-231细胞凋亡PI3K/AKT/mTOR信号通路,抑制TNBC细胞的增殖、迁移,诱导细胞凋亡,可能具有抗肿瘤作用.     

Mechanisms of omega-3 fatty acid-induced growth inhibition in MDA-MB-231 human breast cancer cells

Summary The omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), inhibit the growth of human breast cancer cells in animal models and cell lines, but the mechanism by which this occurs is not well understood. In order to explore possible mechanisms for the modulation of breast cancer cell growth by omega-3 fatty acids, we examined the effects of EPA and DHA on the human breast cancer cell line MDA-MB-231. Omega-3 fatty acids (a combination of EPA and DHA) inhibited the growth of MDA-MB-231 cells by 30–40% (p<0.05) in both the presence and absence of linoleic acid, an essential omega-6 fatty acid. When provided individually, DHA was more potent than EPA in inhibiting the growth of MDA-MB-231 cells (p<0.05). EPA and DHA treatment decreased tumor cell proliferation (p<0.05), as estimated by decreased [methyl−³H]-thymidine uptake and expression of proliferation-associated proteins (proliferating cell nuclear antigen, PCNA, and proliferation-related kinase, PRK). In addition, EPA and DHA induced apoptosis, as indicated by a loss of mitochondrial membrane potential, increased caspase activity and increased DNA fragmentation (p<0.05). Cells incubated with omega-3 fatty acids demonstrated decreased Akt phosphorylation, as well as NFκB DNA binding activity (p<0.05). The results of this study indicate that omega-3 fatty acids decrease cell proliferation and induce apoptotic cell death in human breast cancer cells, possibly by decreasing signal transduction through the Akt/NFκB cell survival pathway.