Anticancer activity of Tephrosia purpurea and Ficus religiosa using MCF 7 cell lines

Objective:To investigate anticancer activity of different fractions of Tephrosia purpurea[TP] （Sharapunkha,Fabaceae） and Ficus religiosa[FR]（Peepal,Moraceae）.Methods:The fractions of TP and FR were prepared and tested for in vitro anticancer activity using human MCF 7 cell line by trypan blue exclusion method.Results:The result showed that among all these fractions of TPI.TPIII.FRI and FRIII showed better anticancer activity compared to other fractions.The IC50 value for TPI（152.4μM）,TPIII（158.71μM）.FRI（160.3μM） and for FRIII（222.7μM） was observed.Conclusions:The present study shows anticancer potential of TP and FR fractions in MCF 7 cell line.

Hesperidin as a preventive resistance agent in MCF-7 breast cancer cells line resistance to doxorubicin

Objective:To evaluate of hesperidin to overcome resistance of doxorubicin in MCF-7 resistant doxorubicin cells(MCF-7/Dox)in cytotoxicity apoptosis and P-glycoprotein(Pgp)expression in combination with doxorubicin.Methods:The cytotoxic properties.50%inhibition concentration(IC_(50))and its combination with doxorubicin in MCF-7 cell lines resistant to doxorubicin(MCF-7/Dox)cells were determined using MTT assay.Apoptosis induction was examined by double staining assay using ethidium bromide-acridine orange.Immunocytochemistry assay was performed to determine the level and localization of Pgp.Results:Single treatment of hesperidin showed cytotoxic activity on MCF-7/Dox cells with IC_(50)value of 11μmol/L.Thus,combination treatment from hesperidin and doxorubicin showed addictive and antagonist effect(CI>1.0).Hesperidin did not increase the apoptotic induction,but decreased the Pgp expressions level when combined with doxorubicin in low concentration.Conclusions:Hesperidin has cytotoxic effect on MCF-7/Dox cells with IC_(50)of 11μmol/L.Hesperidin did not increased the apoptotic induction combined with doxorubicin.Cochemotherapy application of doxorubicin and hesperidin on MCF-7/Dox cells showed synergism effect through inhibition of Pgp expression.

Anticancer property of sediment actinomycetes against MCF-7 and MDA-MB-231 cell lines

ObjectiveTo investigate the anticancer property of marine sediment actinomycetes against two different breast cancer cell lines.MethodsIn vitro anticancer activity was carried out against breast (MCF-7 and MDA-MB-231) cancer cell lines. Partial sequences of the 16s rRNA gene, phylogenetic tree construction, multiple sequence analysis and secondary structure analysis were also carried out with the actinomycetes isolates.ResultsOf the selected five actinomycete isolates, ACT01 and ACT02 showed the IC50 value with (10.13±0.92) and (22.34±5.82) μg/mL concentrations, respectively for MCF-7 cell line at 48 h, but ACT01 showed the minimum (18.54±2.49 μg/mL) level of IC50 value with MDA-MB-231 cell line. Further, the 16s rRNA partial sequences of ACT01, ACT02, ACT03, ACT04 and ACT05 isolates were also deposited in NCBI data bank with the accession numbers of GQ478246, GQ478247, GQ478248, GQ478249 and GQ478250, respectively. The phylogenetic tree analysis showed that, the isolates of ACT02 and ACT03 were represented in group I and III, respectively, but ACT01 and ACT02 were represented in group II. The multiple sequence alignment of the actinomycete isolates showed that, the maximum identical conserved regions were identified with the nucleotide regions of 125 to 221st base pairs, 65 to 119th base pairs and 55, 48 and 31st base pairs. Secondary structure prediction of the 16s rRNA showed that, the maximum free energy was consumed with ACT03 isolate (-45.4 kkal/mol) and the minimum free energy was consumed with ACT04 isolate (?7.6 kkal/mol).ConclusionsThe actinomycete isolates of ACT01 and ACT02 (GQ478246 and GQ478247) which are isolated from sediment sample can be further used as anticancer agents against breast cancer cell lines.

Dodecylamine Derivative of Hydroxocobalamin Acts as a Potent Inhibitor of Cobalamin-Dependent Methionine Synthase in Mammalian Cultured COS-7 Cells

We evaluated whether the dodecylamine derivative of hydroxocobalamin acts as a potent inhibitor of cobalamin-dependent enzymes in an African green monkey kidney cell, COS-7. When the dodecylamine derivative (1.0 μmol/L) did not show any cytotoxicity in the cultured cells, the derivative could not affect methylmalonyl-CoA mutase (holo-enzyme) activity, but significantly inhibit methionine synthase (holo-enzyme) activity in the cell homogenates of COS-7 grown in 1.0 μmol/L hydroxocobalamin-supplemented medium. An immunoblot analysis indicated that the dodecylamine derivative could not decrease the protein level of methionine synthase, but significantly inhibit the enzyme activity.

Construction of Porcine CCK pDNA and Its Expression in COS-7 Cells

CCK correlates with the generation and progression of pancreatic cancer. The research aims to construct eukaryotic expression plasmid pIRES2-EGFP/CCK (CCK pDNA) and transiently express it in COS-7 cells. Total RNA was extracted from porcine intestinal mucosa. RT-PCR was used to amplify the aimed segments CCKcDNA which was then digested with EcoR1 and BamH1 and inserted into a eukaryotic expression plasmid pIRES2-EGFP to construct CCK pDNA. The con- structed plasmid was transfected into COS-7 cells by lepofectamineTM2000-mediated transfer method. The expression of CCK in transfected COS-7 cells was detected 24, 48 and 72 h post-transfection with fluorescence microscopy and the expression level of CCK mRNA in transfected COS-7 cells was assayed by using RT-PCR. The results showed CCK pDNA was successfully constructed and expressed transiently in COS-7 cells. Green fluorescent protein could be detected in the COS-7 cells transfected with porcine CCK pDNA 24 h post-transfection. At 48th h post-transfection, the number of positive cells was increased significantly and much brighter green fluorescence could be detected. And 72 h post-transfection, the green fluorescence of positive cells became even stronger, while no green fluorescence was detected in the control group. The expression of CCK mRNA in the cells was detectable by using RT-PCR. In COS-7 cells transfected with CCK pDNA a high level of porcine CCK mRNA was detected while no expression of porcine CCKmRNA was found in the cells trans- fected with null plasmid. It was concluded CCK pDNA was expressed successfully in COS-7 cells, which lays a foundation for further research on the relationship between CCK and tumor.

STUDY OF ENHANCED IMMUNOGENECITY OF B7-1 GENE TRANSFECTED HUMAN HELA CELL LINE

This work was supposed by CMB (No. 96—635) This is one of papers of the special issue on gene therapy research (Chin J Cancer Res Vol. 9 No. 4 December, 1997). Although cervical carcinoma cells may express the human papillomavirus protein E6 and E7, they fail to induce an effective specific cytotoxic T lymphocyte response. Recent studies suggest that expression of CD 80 (B7 1) on tumor cells is effective to induce antitumor immune responses. 1,2 In our study, CD 80 gene was transfected into human Hela cell line with a CD 80 expression plasmid (B7 1 +pcDNA 3) by electroporation, then the immunogenecity of the modified Hela cell was tested in TLMC (tumor lymphocyte mixed culture) system. Thymidine lymphocyte proliferation assays showed that the response of human peripheral blood lymphocytes (PBLS) to CD 80 positive Hela cells demonstrated a substantial increase in cell proliferation compared to the response to control cells. Cocultivation of allogeneic PBLs with CD 80 positive tumor cells for three days can induce an increased secretion of IL 2. Our results demonstrate an immunostimulatory effect of CD 80 expression on cervical cancer cells, which provides a basis for the development of a therapeutic tumor vaccine.

REVERSION OF MULTIDRUG RESISTANCE IN THE P-GLYCOPROTEIN POSITIVE BREAST CANCER CELL LINE(MCF-7/ADR) BY INTRODUCTION OF HAMMERHEAD RIBOZYME

A hammerhead ribozyme which site-specifically cleaved the GUC position in canon 880 of the mdr1 mRNA was designed. The target site was chosen between the two ATP binding sites, which may be important for the function of the P-Gp as an ATP-dependent pump. A DNA sequence encoding the ribozyme gene was then incorporated into a eukaryotic expression vector (pH Apr-1 neo) and transfected into the breast cancer cell line MCF-7/Adr, which is resistant to adriamycin and expresses the MDR phenotype. The ribozyme was stably expressed in the cell line by the RNA dot blotting assay. The result of Northern blot assay showed that the expressed ribozyme could decrease the level of mdrl mRNA expression by 83. 5 %; and the expressed ribozyme could inhibite the formation of p-glycoprotein detected by immuno- cy-tochemistry assay and could reduce the cell’s resistance to adrimycin; this means that the resistant cells were 1 000-fold more resistant than the parental cell line(MCF-7), whereas those cell clones that showed ribozyme expression were only 6-fold more resistant than the parental cell line. These results show that a potentially useful tool is at hand which may inactivate MDR1 mRNA and revert the multidrug resistance phenotype.

Studies on mechanism of cis9,trans11-CLA and trans10,cis12-CLA inducing apoptosis of human breast cancer cell line MCF-7

Objective： The aim of the study was to explore the activities of cis9, trans11-CLA （C9, t11-CLA） and transl0, cis12-CLA （t10, c12-CLA） inhibiting tumor, and investigate their relationships with PPARy and apoptotic proteins, and mechanism of anti-cancer. Methods： The inhibitory rate, cell growth curve and apoptotic morphological observation of MCF-7 cells were obtained by MTT assay, trypan blue staining and Hoechst33342 fluorescence staining. The apoptotic rate and cell cycle were detected with flow cytometry. Transcriptional level of genes was detected with RT-PCR semi-quantitative method, and Western blot was performed to detect proteins levels. Results： The two CLA isomers could reduce cell proliferation （P 〈 0.05）, increase apoptotic rate （P 〈 0.05）, and increase obviously the transcriptional and protein levels of PPARy （P 〈 0.01）. The synchronism and correlation between the effects of CLA to PPARy and apoptotic proteins Bax, Bcl-2, Caspase 3 changes were found with the dose- and time-dependent manners. There was cooperative relation between the levels of PPARy and the rates of Bax/Bcl-2, Caspase 3 （small fragment） by experiments of PPARy inhibitor GW9662 and ligand Rosiglitazone. Conclusion： The apoptotic pathway of PPARy-Bcl-2-Caspase 3 signaling was found. The C9, t11-CLA and tl0, c12-CLA could inhibit MCF-7 cell proliferation and promote apoptosis via activating PPARy-Bcl-2-Caspase 3 pathway. CLA may be a kind of activator of PPARv.

Expression of Recombinant Protein Bovine Prion pCIp264 in COS-7 Cells and Its Detection

Bovine spongiform encephalopathy （BSE） is thought to be caused by prions initially derived from sheep scrapie, and epidemiological studies suggest that new viriant form of CJD manifest in Great Britain may be caused by BSE prions. PrP^Sc is thought to pathogenic factor of transmissible spongiform encephalopathy （TSE）, which invariably involve a post-translational modification process of PrPc encoded by the host euchromosome PrP gene during the period it converted into the pathogenic form （PrP^Sc）, PrP is nomal cellular protein which has been found in both neuronal and nonneuronal tissues. Since the crucial infectious event in protein-transmitted diseases is an induced misfolding of prion proteins （PrP^c） catalyzed by already misfolded PrP^Sc, it is of high importance that such collisions are enhanced by two-dimensional diffusion in cell membranes is of high importance compared to three-dimensional diffusion in solution. The level of PrP mRNA in brain is higher than other tissue, but purification of PrPc from rodent has been difficult. To understand the formation of PrP^Sc, it seemed useful to develop a system for produced a large quantities of PrPc since there is no nature source of PrP^c. The pCI-neo mammalian expression vector contains the neomycin phosphtransferase gene which serves as a marker for the selection of stable transfected cells with G418. COS-7 cells constitutively express simian viruse 40 （SV40） T-antigen and support replication of expression plasmids containing the SV40 origin of replication, amplifying the introduced expression cassettes, now become important routine of expression a large number of heterologous gene products. In this paper, the authors used pCI-neo vector to construct a recombnant pCIp264 （cotains mPrP, N-signalpeptide and C-GPI anchor） plasmid to express it in the COS-7 cells and meanwhile detect the expression fusion using IN-ELISA, IN-IFA and western blot, and obtain some approximative nature PrPc.

Effects of 4-(3-Chloro-Benzyl)-6,7-Dimethoxy-Quinazoline on Kinetics of P120-Catenin and Periplakin in Human Buccal Mucosa Squamous Carcinoma Cell Line

In order to detect molecular markers for the epidermal growth factor inhibitor 4-(3-chloro-benzyl)- 6,7-dimethoxy-quinazoline (tyrphostin), we investigated the kinetics of p120-catenin and periplakin in the human buccal mucosa squamous cancer cell line BICR 10 treated with 3 nM tyrphostin. Growth of BICR 10 cells was inhibited by treatment with tyrphostin. Although changes were not observed in the expression of EGFR and p120-catenin, expression of Akt, Src and periplakin in BICR 10 treated with 3 nM tyrphostin tended to decrease. In addition, phosphorylation of EGFR, Akt and Src was inhibited by treatment with tyrphostin. On immunocytochemical staining, immunoreactions with phosphorylated EGFR, phosphorylated Akt and phosphorylated p120-catenin were weak in BICR 10 treated with tyrphostin. There was a slight immunocy to chemical reaction to periplakin in BICR 10 cells induced by tyrphostin. In conclusion, the decrease in phosphorylation in EGFR and p120-catenin by tyrphostin, following the decrease in Src or Akt phosphorylation, may inhibit expression of several growth factors associated with the proliferation and migration of cancer cells.

Construction of Cox7a2 fluorescent vector and its effect on cytochrome C oxidase activity in mouse Sertoli cell line TM4

Objective To construct Cox7a2 fluorescent vector and study its effect on cytochrome C oxidase ( COX) activity in mouse Sertoli cell line TM4. Methods The coding region of CoxTa2 was amplified from mouse Sertoli cell line TM4 by RT-PCR. PCR product was

弓形虫和乙型肝炎病毒混合核酸疫苗的研究Ⅱ.pcDNA3-HBsAg-GRA1在COS-7细胞中的表达及鉴定

目的 鉴定pcDNA3 HBsAg GRA1在哺乳动物细胞内是否表达目的蛋白。 方法 提取pcDNA3 HBsAg GRA1质粒 ;体外培养COS 7细胞 ;pcDNA3 HBsAg GRA1经脂质体转染体外培养的COS 7细胞 ;取转染后的细胞培养上清进行SDS PAGE ,Western blot鉴定。结果 成功将pcDNA3 HBsAg GRA1转染入COS 7细胞。转染的细胞能高效表达分子为 4 7kD分泌性融合蛋白 (HBsAg GRA1)。HBsAg GRA1能同时被HBsAb阳性人血清及弓形虫免疫兔血清所识别。 结论 pcDNA3 HB sAg GRA1在体外培养的COS 7细胞中高效表达与预期分子量大小相同 ,且具有免疫学活性的融合蛋白。

硅壳纳米颗粒对COS-7细胞的生物效应

从硅壳纳米颗粒对细胞存活率、细胞周期及细胞生长曲线的影响等方面系统地考察了包裹RuBpy染料的硅壳荧光纳米颗粒(FSiNPs)对美洲绿猴肾细胞(COS-7)的生物效应.结果表明,FSiNPs对COS-7细胞的影响是浓度依赖性的,低浓度(<0.2μg/μL)的FSiNPs对细胞的存活率、细胞周期及整个生长过程均无负面影响,但随着与COS-7细胞作用的FSiNPs浓度的增大,FSiNPs对COS-7细胞的毒性也逐渐增大,尤其是对细胞周期及细胞生长曲线的影响更为敏感.同时,利用FSiNPs的荧光信号同步指示作用,考察了COS-7细胞对FSiNPs的吞噬作用,发现FSiNPs通过细胞膜的吞噬作用随机地进入到细胞内,一部分FSiNPs被细胞当成异物外排到细胞培养基中,另一部分则进入到下一代细胞中.随着细胞传代次数的增多和新生胞质的产生,FSiNPs在细胞内的含量逐渐减少,最后消失.在这一过程中,细胞的形态和生长状况依然良好.上述研究结果有望为FSiNPs在细胞生物学的研究和应用提供一定的安全标准,并为开展基于新型纳米颗粒的纳米颗粒器件的研究与应用打下了基础.

野生型抑癌基因PTEN真核表达载体的鉴定及其在COS-7细胞株表达产物的鉴定

目的:电泳并真核细胞鉴定pcDNA3.0-PTEN真核表达质粒。方法:将含有pcDNA3.0-PTEN真核表达质粒的EcoliJM109细胞挑少许于LB液体培养基上,振荡过夜,离心,碱裂解法裂解细菌,参照UNIQ-10柱式质粒抽提试剂盒操作步骤抽提质粒,电泳鉴定,将获得的pcDNA3.0-PTEN真核表达质粒采用脂质体转染法转入COS-7细胞株,传代培养细胞株,West-Blot鉴定PTEN蛋白质的表达。结果:实验得到的pcDNA3.0-PTEN真核表达质粒大小约为6.0kb,质粒浓度为0.080μg/μl。该质粒目的基因在COS-7细胞株表达产物经West-Blot鉴定证实为目的基因表达产物。结论:pcDNA3.0-PTEN真核表达质粒内含有所需目的基因,该真核表达系统能在真核细胞株COS-7表达所需目的基因产物,可以应用该质粒对PTEN基因缺失或杂合性缺失的肿瘤细胞进行试验性治疗。

环氧合酶2的DNA疫苗构建及其在COS-7细胞中表达

构建了环氧合酶-2(Cyclooxygenase-2,COX-2)的DNA疫苗载体pVAX1-COX-2,并考察在COS-7细胞中表达.用RT-PCR法从肺癌A549细胞中获得环氧合酶-2基因片段,此片段插入pVAX1载体构建pVAX1-COX-2真核重组表达质粒,脂质体介导法转染COS-7细胞,以pVAX1为对照,收集稳定转染细胞,利用RT-PCR和West-ern-blot分别在mRNA和蛋白水平上考察COX-2表达.实验结果表明:RT-PCR法从A549细胞mRNA中扩增1.8 kb的COX-2基因片段,酶切与测序结果表明所构建的真核表达载体pVAX1-COX-2与预期相符,质脂体法成功地将质粒DNA转染到COS-7细胞中.RT-PCR和Western-blot分析结果表明COX-2已表达.因此,所构建的真核表达载体pVAX1-COX-2正确,且在COS-7细胞中表达.

基因枪介导真核表达质粒转染体外培养的COS-7细胞系的实验研究

目的:建立基因枪子弹制备及转染体外培养COS-7细胞系的方法。方法:以亚精氨、氯化钙沉淀法制备子弹(DNA+金颗粒),利用原子力显微镜观察子弹制备情况;采用基因枪方法分别将真核表达质粒pVax-Dsred-IRES-EGFP转染对照组和实验组COS-7细胞,转染后24h,利用激光扫描共聚焦显微镜观察细胞中红、绿荧光蛋白的表达。结果:制备了基因枪子弹,DNA紧密包裹在金颗粒周围;基因枪介导的pVax-Dsred-IRES-EGFP被转染入体外培养的COS-7细胞,转染后24h可检测到红、绿荧光,而对照组则没有荧光蛋白的表达。结论:国产新芝SJ-500型基因枪能够有效介导外源基因转移,基因枪转染的COS-7细胞能够有效表达报告基因。

C端带Myc和多聚组氨酸双标记的重组人β-防御素-2在COS-7细胞的转染表达

本研究旨在探索建立能有效表达和分泌人类β-防御素 - 2 (h BD- 2 ) ,其表达产物又易于被检测和分离纯化的哺乳类动物细胞表达系统的可能性及技术路线。将 h BD- 2的全长 c DNA片段插入编码双重报告基因 Myc和 6个多聚组氨酸 (His)的真核表达质粒 pc DNA3.1/Myc- His(+) ,构建出 C端带 Myc和 6× His的 rpc DNA3.1/Myc-His(+) /h BD- 2。用脂质体转染法将此重组真核表达载体导入 COS- 7细胞 ,分别从 m RNA和蛋白质水平分析 h BD-2的表达情况并同步检测细胞可溶性蛋白及培养上清的抗菌活性。采用 RT- PCR法从被转染的细胞中扩增出一条约 2 4 0 bp的片段 ,其大小与预测相符。采用 Western blot法 ,用抗 His抗体检测到细胞可溶性蛋白在约 10 Kd处有强反应条带显示 ,其大小与该重组质粒结构中由 p CMV启动子驱动的基因片段有可能表达成肽链的分子量 (10 .1)相符。双层肉汤琼脂平板扩散法结果显示 :分别与正常细胞可溶性蛋白和培养上清比较 ,转染重组质粒的 COS- 7细胞的可溶性蛋白及培养上清在金黄色葡萄球菌的平板上均形成明显抑菌环。这些结果提示 :所建立的 h BD- 2哺乳类动物细胞表达系统能有效表达和分泌活性 h BD- 2。

SOX7靶向ERK1/2/PD-L1通路抑制结直肠癌血管生成

目的探讨性别决定区Y框蛋白7(SOX7)对结直肠癌血管生成的影响及潜在作用机制。方法应用免疫荧光检测结直肠癌患者组织样本中SOX7表达水平,之后通过裸鼠、转染SOX7 mimic的人结直肠癌细胞系SW480细胞和人脐静脉内皮细胞(HUVEC)共培养进一步研究。用Western-blot验证SOX7与ERK1/2/PD-L1对结直肠癌细胞的相关蛋白表达的影响。用CCK8检测SOX7与ERK1/2/PD-L1对HUVEC增殖的影响。通过体外内皮细胞成管实验测定SOX7与ERK1/2/PD-L1对肿瘤血管生成的影响。结果SOX7在人结直肠癌组织中表达被抑制(P<0.01),同时SOX7的过表达抑制了小鼠体内肿瘤生长(P<0.01)。SW480细胞中SOX7的过表达抑制了ERK1/2、c-Jun的表达,并在ERK1/2的激动剂Senkyunolide I的作用下上调了SW480细胞的ERK1/2、c-Jun蛋白表达(P<0.01),逆转了SOX7对SW480细胞中ERK1/2、c-Jun蛋白表达的影响(P<0.01)。HUVEC中SOX7抑制了PD-L1、V-EGFR2、p-PI3K、HIF-1α的蛋白表达,Senkyunolide I上调了HUVEC的PD-L1、V-EGFR2、p-PI3K、HIF-1α的蛋白表达,并逆转了SOX7对HUVEC中上述相关蛋白表达的影响(P<0.01)。PD-1/PD-L1 Inhibitor 3抑制了PD-L1、V-EGFR2、p-PI3K、HIF-1α的蛋白表达,SOX7过表达在PD-1/PD-L1 Inhibitor 3的影响下并没有表现出抑制作用。CCK8实验结果显示SOX7过表达显著抑制了HUVEC的增殖能力,Senkyunolide I作用下的两组HUVEC增殖能力较SOX7 NC组与SOX7 mimic组明显上升,PD-1/PD-L1 Inhibitor 3作用下的两组HUVEC增殖能力较SOX7 NC组与SOX7 mimic组明显下降,以上均有明显统计学差异(P<0.01)。成管实验结果显示SOX7过表达抑制了HUVEC的血管生成,Senkyunolide I强烈加速了血管生成,而PD-1/PD-L1 Inhibitor 3血管生成则被显著抑制,以上均有明显统计学差异(P<0.01)。结论SOX7通过ERK1/2/PD-L1通路抑制结直肠肿瘤的增殖和血管生成,SOX7可能是晚期CRC患者临床治疗中潜在的抗血管生成靶点。

大鼠促甲状腺激素释放激素受体1基因的克隆及其在COS-7细胞系中的表达

目的:克隆大鼠促甲状腺激素释放激素受体1(TRH-R1)基因,构建其真核表达载体,并检测该基因在非洲绿猴肾细胞系COS-7中的表达。方法:应用RT-PCR方法,以大鼠脑源RNA为模板,扩增获得TRH-R1基因,定向克隆到pDsRed2-N1中,以LipofectAMINE 2000试剂转染pDsRed2-N1-TRH-R1表达载体至COS-7细胞系中进行瞬时表达。结果:测序结果表明,从大鼠脑源总RNA中克隆到正确的TRH-R1基因全长编码序列;显微照相观察到所构建的TRH-R1表达载体质粒在COS-7细胞系中获得有效表达。结论:大鼠TRH-R1基因的克隆、真核表达载体的构建及在COS-7细胞系中表达获得成功,为进一步研究其功能奠定了基础。

Sensitivity Evaluation of Two Human Breast Cancer Cell Lines to Tamoxifen through Apoptosis Induction

Tamoxifen citrate (TAM) has been used to treat breast cancer in women for many years. The com-parative effects of TAM in inducing apoptosis were evaluated in estrogen receptor-positive (ER- positive MCF-7) and estrogen receptor-negative (ER-negative MDA-MB-231) human breast cancer cell lines in vitro in order to determine if these two cell lines differ in their sensitivity to TAM. Mi-tochondrial membrane permeability potential disruption was assessed in both cell lines by a lip-ophilic cationic dye (DePsipher assay, Trevigen, Inc.) utilizing fluorescence microscopy. Using this specific fluorochrome, we were able to associate mitochondrial membrane disruption to early, mid-, and late apoptotic cells. TAM induced cell death via apoptosis in both ER-positive and ER- negative cells, however, apoptosis induction was more pronounced in ER-positive MCF-7 compared to ER-negative MDA-MB-231 breast cancer cells. These findings may have some therapeutic use in the treatment of estrogen dependent and estrogen independent breast cancer.