Dietary antioxidant curcumin inhibits microtubule assembly through tubulin binding

Curcumin, a component of turmeric, has potent antitumor activity against several tumor types. However, its molecular target and mechanism of antiproliferative activity are not clear. Here, we identified curcumin as a novel antimicrotubule agent. We have examined the effects of curcumin on cellular microtubules and on reconstituted microtubules in vitro. Curcumin inhibited HeLa and MCF-7 cell proliferation in a concentration-dependent manner with IC(50) of 13.8 +/- 0.7 microm and 12 +/- 0.6 microm, respectively. At higher inhibitory concentrations (> 10 microm), curcumin induced significant depolymerization of interphase microtubules and mitotic spindle microtubules of HeLa and MCF-7 cells. However, at low inhibitory concentrations there were minimal effects on cellular microtubules. It disrupted microtubule assembly in vitro, reduced GTPase activity, and induced tubulin aggregation. Curcumin bound to tubulin at a single site with a dissociation constant of 2.4 +/- 0.4 microm and the binding of curcumin to tubulin induced conformational changes in tubulin. Colchicine and podophyllotoxin partly inhibited the binding of curcumin to tubulin, while vinblastine had no effect on the curcumin-tubulin interactions. The data together suggested that curcumin may inhibit cancer cells proliferation by perturbing microtubule assembly dynamics and may be used to develop efficacious curcumin analogues for cancer chemotherapy.     

Synthesis, biological evaluation, and molecular docking studies of 2,6-dinitro-4-(trifluoromethyl)phenoxysalicylaldoxime derivatives as novel antitubulin agents

A series of 2,6-dinitro-4-(trifluoromethyl)phenoxysalicylaldoxime derivatives (1h-20h) have been designed and synthesized, and their biological activities were also evaluated as potential antiproliferation and tubulin polymerization inhibitors. Among all the compounds, 2h showed the most potent activity in vitro, which inhibited the growth of MCF-7, Hep-G2 and A549 cell lines with IC(50) values of 0.70 ± 0.05, 0.68 ± 0.02 and 0.86 ± 0.05 μM, respectively. Compound 2h also exhibited significant tubulin polymerization inhibitory activity (IC(50)=3.06 ± 0.05 μM). The result of flow cytometry (FCM) demonstrated that compound 2h induced cell apoptosis. Docking simulation was performed to insert compound 2h into the crystal structure of tubulin at colchicine binding site to determine the probable binding model. Based on the preliminary results, compound 2h with potent inhibitory activity in tumor growth may be a potential anticancer agent.     

A Rhodanine Derivative CCR-11 Inhibits Bacterial Proliferation by Inhibiting the Assembly and GTPase Activity of FtsZ

A perturbation of FtsZ assembly dynamics has been shown to inhibit bacterial cytokinesis. In this study, the antibacterial activity of 151 rhodanine compounds was assayed using Bacillus subtilis cells. Of 151 compounds, eight strongly inhibited bacterial proliferation at 2 μM. Subsequently, we used the elongation of B. subtilis cells as a secondary screen to identify potential FtsZ-targeted antibacterial agents. We found that three compounds significantly increased bacterial cell length. One of the three compounds, namely, CCR-11 [(E)-2-thioxo-5-({[3-(trifluoromethyl)phenyl]furan-2-yl}methylene)thiazolidin-4-one], inhibited the assembly and GTPase activity of FtsZ in vitro. CCR-11 bound to FtsZ with a dissociation constant of 1.5 ± 0.3 μM. A docking analysis indicated that CCR-11 may bind to FtsZ in a cavity adjacent to the T7 loop and that short halogen-oxygen, H-bonding, and hydrophobic interactions might be important for the binding of CCR-11 with FtsZ. CCR-11 inhibited the proliferation of B. subtilis cells with a half-maximal inhibitory concentration (IC(50)) of 1.2 ± 0.2 μM and a minimal inhibitory concentration of 3 μM. It also potently inhibited proliferation of Mycobacterium smegmatis cells. Further, CCR-11 perturbed Z-ring formation in B. subtilis cells; however, it neither visibly affected nucleoid segregation nor altered the membrane integrity of the cells. CCR-11 inhibited HeLa cell proliferation with an IC(50) value of 18.1 ± 0.2 μM (～15 × IC(50) of B. subtilis cell proliferation). The results suggested that CCR-11 inhibits bacterial cytokinesis by inhibiting FtsZ assembly, and it can be used as a lead molecule to develop FtsZ-targeted antibacterial agents.     

3-Aryl/Heteroaryl-5-amino-1-(3′,4′,5′-trimethoxybenzoyl)-1,2,4-triazoles as antimicrotubule agents. Design,synthesis, antiproliferative activity and inhibition of tubulin polymerization

Many natural and synthetic substances are known to interfere with the dynamic assembly of tubulin, preventing the formation of microtubules. In our search for potent and selective antitumor agents, a novel series of 1-(3′,4′,5′-trimethoxybenzoyl)-5-amino-1,2,4-triazoles were synthesized. The compounds had different heterocycles, including thiophene, furan or the three isomeric pyridines, and they possessed a phenyl ring bearing electron-releasing or electron-withdrawing substituents at the 3-position of the 5-amino-1,2,4-triazole system. Most of the twenty-two tested compounds showed moderate to potent antiproliferative activities against a panel of solid tumor and leukemic cell lines, with four (5j, 5k, 5o and 5p) showing strong antiproliferative activity (IC₅₀ < 1 μM) against selected cancer cells. Among them, several molecules preferentially inhibited the proliferation of leukemic cell lines, showing IC₅₀ values 2-100-fold lower for Jurkat and RS4;11 cells than those for the three lines derived from solid tumors (HeLa, HT-29 and MCF-7 cells). Compound 5k strongly inhibited tubulin assembly, with an IC₅₀ value of 0.66 μM, half that obtained in simultaneous experiments with CA-4 (IC₅₀ = 1.3 μM).     

Rotenone inhibits mammalian cell proliferation by inhibiting microtubule assembly through tubulin binding

Rotenone, a widely used insecticide, has been shown to inhibit mammalian cell proliferation and to depolymerize cellular microtubules. In the present study, the effects of rotenone on the assembly of microtubules in relation to its ability to inhibit cell proliferation and mitosis were analyzed. We found that rotenone inhibited the proliferation of HeLa and MCF-7 cells with half maximal inhibitory concentrations of 0.2 +/- 0.1 microm and 0.4 +/- 0.1 microm, respectively. At its effective inhibitory concentration range, rotenone depolymerized spindle microtubules of both cell types. However, it had a much stronger effect on the interphase microtubules of MCF-7 cells compared to that of the HeLa cells. Rotenone suppressed the reassembly of microtubules in living HeLa cells, suggesting that it can suppress microtubule growth rates. Furthermore, it reduced the intercentrosomal distance in HeLa cells at its lower effective concentration range and induced multipolar-spindle formation at a relatively higher concentration range. It also increased the level of checkpoint protein BubR1 at the kinetochore region. Rotenone inhibited both the assembly and the GTP hydrolysis rate of microtubules in vitro. It also inhibited the binding of colchicine to tubulin, perturbed the secondary structure of tubulin, and reduced the intrinsic tryptophan fluorescence of tubulin and the extrinsic fluorescence of tubulin-1-anilinonaphthalene-8-sulfonic acid complex, suggesting that it binds to tubulin. A dissociation constant of 3 +/- 0.6 microm was estimated for tubulin-rotenone complex. The data presented suggest that rotenone blocks mitosis and inhibits cell proliferation by perturbing microtubule assembly dynamics.     

Synthesis, biological evaluation, and molecular docking studies of benzyl, alkyl and glycosyl [2-(arylamino)-4,4-dimethyl-6-oxo-cyclohex-1-ene]carbodithioates, as potential immunomodulatory and immunosuppressive agents

The immunomodulating properties of functionalized [2-(arylamino)-4,4-dimethyl-6-oxo-cyclohex-1-ene] carbodithioates and 6,6-dimethyl-4-(2-(propan-2-ylidene)hydrazinyl)-6,7-dihydro-2H-indazole-3(5H)-thione compounds have been investigated. Four of them, 13, 18, 19 and 20 inhibited PBMC proliferation induced by phytohemagglutinin (PHA) in a dose dependent manner with an IC(50) of ≤ 20 μM. The Th-1 cytokine, interleukin-2 (IL-2) in PHA/PMA-stimulated peripheral blood mononuclear cells (PBMCs) is significantly inhibited by 13, 19 and 20 with an IC(50) of 8.4 ± 0.4, 5.34 ± 0.15 and 4.9 ± 0.7 μM, respectively. They also inhibited the PMA/lipopolysaccharide-induced proinflammatory cytokines, IL-1β and TNF-α production in human monocytic leukemia cells (THP-1), by 86%, 46% and 59.2% for IL-1β and by 83.8%, 48.2% and 58.7% for TNF-α, respectively. Only 20 showed significant suppressive activity against the phagocyte oxidative burst in a dose dependent manner, with an IC(50) of 23.8 μM. LPS-induced nitrites in mouse macrophages were found to be inhibited by compounds 6, 8, 13-15 and 19 with an IC(50), which range between 7.7 and 63 μM. The cytotoxicity for the active compounds was also studied on Rat Wistar Hepatocyte cell line, CC1 and the Mouse Fibroblast cell line 3T3 NIH in the presence of compounds using a standard MTT assay. Furthermore, structural-activity relationship using automated docking software revealed that active compounds 7, 13 and 19, adapted the same binding mode, however the most active compound 20 is found deeply inserted within the ligand binding site of IL-2, as multiple hydrophobic and hydrophilic key interactions stabilize the compound inside the binding site, thus contributing higher activity.     

Design, synthesis and anticancer activity of novel dihydrobenzofuro[4,5-b][1,8]naphthyridin-6-one derivatives

On the basis of the chemical structures of psorospermin with a xanthone template and acronycine derivatives with an acridone template, rac-1 and rac-2 constructed on an 1,2-dihydrobenzofuro[4,5-b][1,8]naphthyridin-6(11H)-one scaffold were designed and synthesized as potential anticancer agents. Their anticancer activities were evaluated against five human cancer cell lines. Rac-2 showed similar anticancer activity to doxorubicin and rac-1 exhibited even higher anticancer activity against LNCaP (IC(50)=0.14 μM), DU145 (IC(50)=0.15 μM), PC3 (IC(50)=0.30 μM) and MCF-7 (IC(50)=0.26 μM) cancer lines than doxorubicin and rac-2. Also, rac-1 revealed very potent anticancer activity (IC(50)=0.15 μM) against MCF-7/ADR cell (doxorubicin-resistant breast cancer cell) lines and induced G2/M phase arrest of the cell cycle in MCF-7/ADR cells.     

Antimitotic antifungal compound benomyl inhibits brain microtubule polymerization and dynamics and cancer cell proliferation at mitosis, by binding to a novel site in tubulin

The antifungal agent benomyl [methyl-1-(butylcarbamoyl)-2-benzimidazolecarbamate] is used throughout the world against a wide range of agricultural fungal diseases. In this paper, we investigated the interaction of benomyl with mammalian brain tubulin and microtubules. Using the hydrophobic fluorescent probe 1-anilinonaphthalene-8-sulfonic acid, benomyl was found to bind to brain tubulin with a dissociation constant of 11.9 +/- 1.2 microM. Further, benomyl bound to at a novel site, distinct from the well-characterized colchicine and vinblastine binding sites. Benomyl altered the far-UV circular dichroism spectrum of tubulin and reduced the accessibility of its cysteine residues to modification by 5,5'-dithiobis-2-nitrobenzoic acid, indicating that benomyl binding to tubulin induces a conformational change in the tubulin. Benomyl inhibited the polymerization of brain tubulin into microtubules, with 50% inhibition occurring at a concentration of 70-75 microM. Furthermore, it strongly suppressed the dynamic instability behavior of individual brain microtubules in vitro as determined by video microscopy. It reduced the growing and shortening rates of the microtubules but did not alter the catastrophe or rescue frequencies. The unexpected potency of benomyl against mammalian microtubule polymerization and dynamics prompted us to investigate the effects of benomyl on HeLa cell proliferation and mitosis. Benomyl inhibited proliferation of the cells with an IC(50) of 5 microM, and it blocked mitotic spindle function by perturbing microtubule and chromosome organization. The greater than expected actions of benomyl on mammalian microtubules and mitosis together with its relatively low toxicity suggest that it might be useful as an adjuvant in cancer chemotherapy.     

Antiproliferative activity of novel derivative of thiopyran on breast and colon cancer lines and DNA binding

Dimethyl-5-acetyl-4-methyl-6-(4-methylphenylimino)-6H-thiopyran-2,3-dicarboxylate (4) has been synthesized and its antiproliferative activity is reported here. Compound 4 inhibited the growth of human colon cancer cell line HCT-15 with an IC(50) value of 3.5 μM and of breast cancer cell line MCF-7 with an IC(50) value of 1.5 μM in a dose/time-dependent manner using a sulforhodamine B assay. Moreover, suppression of clonogenic activity occurred after exposure to 4 at a concentration of 4 μM for HCT-15 and 1.7 μM for MCF-7. The results also showed tumor cell invasion through matrigel and cell adhesion. The effect of ligand complexation on DNA structure led to overall affinity constant of K(4-DNA)=9.8×10(4) M(-1).     

Somatostatin subtype-2 receptor-targeted metal-based anticancer complexes

Conjugates of a dicarba analogue of octreotide, a potent somatostatin agonist whose receptors are overexpressed on tumor cells, with [PtCl(2)(dap)] (dap = 1-(carboxylic acid)-1,2-diaminoethane) (3), [(η(6)-bip)Os(4-CO(2)-pico)Cl] (bip = biphenyl, pico = picolinate) (4), [(η(6)-p-cym)RuCl(dap)](+) (p-cym = p-cymene) (5), and [(η(6)-p-cym)RuCl(imidazole-CO(2)H)(PPh(3))](+) (6), were synthesized by using a solid-phase approach. Conjugates 3-5 readily underwent hydrolysis and DNA binding, whereas conjugate 6 was inert to ligand substitution. NMR spectroscopy and molecular dynamics calculations showed that conjugate formation does not perturb the overall peptide structure. Only 6 exhibited antiproliferative activity in human tumor cells (IC(50) = 63 ± 2 μM in MCF-7 cells and IC(50) = 26 ± 3 μM in DU-145 cells) with active participation of somatostatin receptors in cellular uptake. Similar cytotoxic activity was found in a normal cell line (IC(50) = 45 ± 2.6 μM in CHO cells), which can be attributed to a similar level of expression of somatostatin subtype-2 receptor. These studies provide new insights into the effect of receptor-binding peptide conjugation on the activity of metal-based anticancer drugs, and demonstrate the potential of such hybrid compounds to target tumor cells specifically.     

Thiosemicarbazone fragment embedded within 1,2,4-triazole ring as inhibitors of Entamoeba histolytica

A series of 1,2,4-triazole derivatives containing thiosemicarbazone linkage was synthesized and evaluated for their in vitro antiamoebic activity against HM1:IMSS strain of Entamoeba histolytica. All the compounds were capable of inhibiting the growth of E. histolytica out of which four compounds (IC(50)=0.28-1.38 μM) were found to have better efficacy than the standard drug Metronidazole (IC(50)=1.8 μM). Cytotoxicity of the active compounds was assessed by MTT assay using human breast cancer MCF-7 cell line, which revealed that all the compounds were low cytotoxic in the concentration range of 2.5-250 μM.     

Neopetrosiquinones A and B, sesquiterpene benzoquinones isolated from the deep-water sponge Neopetrosia cf. proxima

Two new marine-derived sesquiterpene benzoquinones which we designate as neopetrosiquinones A (1) and B (2), have been isolated from a deep-water sponge of the family Petrosiidae. The structures were elucidated on the basis of their spectroscopic data. Compounds 1 and 2 inhibit the in vitro proliferation of the DLD-1 human colorectal adenocarcinoma cell line with IC(50) values of 3.7 and 9.8 μM, respectively, and the PANC-1 human pancreatic carcinoma cell line with IC(50) values of 6.1 and 13.8 μM, respectively. Neopetrosiquinone A (1) also inhibited the in vitro proliferation of the AsPC-1 human pancreatic carcinoma cell line with an IC(50) value of 6.1 μM. The compounds are structurally related to alisiaquinone A, cyclozonarone, and xestoquinone.     

Microtubule depolymerization and phosphorylation of c-Jun N-terminal kinase-1 and p38 were involved in gambogic acid induced cell cycle arrest and apoptosis in human breast carcinoma MCF-7 cells

Gambogic acid (GA), an ingredient isolated from Garcinia hanburyi, has potent anticancer activity both in vitro and in vivo. In the present study, we examined the effects of GA on intracellular microtubules and reconstituted microtubules in vitro. Immunofluorescence microscopy revealed that 2.5 muM GA caused microtubule cytoskeleton disruption and microtubule depolymerization in human breast carcinoma MCF-7 cells, thereby reducing the amount of polymer form of tubulin and increasing the amount of monomer form of tubulin. We further confirmed that GA could depolymerize microtubule associated protein (MAP)-free microtubules and MAP-rich microtubules in vitro. Thus we suggested that GA-induced G2/M phase cell cycle arrest may be attributed to its depolymerization of microtubules. We also revealed that phosphorylation levels of p38 and c-Jun N-terminal kinase-1 (JNK-1) were increased markedly by GA, resulting in apoptosis of MCF-7 cells. Taken together, our results suggested that GA depolymerized microtubules and elevated the phosphorylation levels of JNK1 and p38, which caused G2/M cell cycle arrest and apoptosis in MCF-7 cells.     

The natural naphthoquinone plumbagin exhibits antiproliferative activity and disrupts the microtubule network through tubulin binding

Plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone), a naphthoquinone isolated from the roots of Plumbaginaceae plants, has potential antiproliferative activity against several tumor types. We have examined the effects of plumbagin on cellular microtubules ex vivo as well as its binding with purified tubulin and microtubules in vitro. Cell viability experiments using human non-small lung epithelium carcinoma cells (A549) indicated that the IC 50 value for plumbagin is 14.6 microM. Immunofluorescence studies using an antitubulin FITC conjugated antibody showed a significant perturbation of the interphase microtubule network in a dose dependent manner. In vitro polymerization of purified tubulin into microtubules is inhibited by plumbagin with an IC 50 value of 38 +/- 0.5 microM. Its binding to tubulin quenches protein tryptophan fluorescence in a time and concentration dependent manner. Binding of plumbagin to tubulin is slow, taking 60 min for equilibration at 25 degrees C. The association reaction kinetics is biphasic in nature, and the association rate constants for fast and slow phases are 235.12 +/- 36 M (-1) s (-1) and 11.63 +/- 11 M (-1) s (-1) at 25 degrees C respectively. The stoichiometry of plumbagin binding to tubulin is 1:1 (mole:mole) with a dissociation constant of 0.936 +/- 0.71 microM at 25 degrees C. Plumbagin competes for the colchicine binding site with a K i of 7.5 microM as determined from a modified Dixon plot. Based on these data we conclude that plumbagin recognizes the colchicine binding site to tubulin. Further study is necessary to locate the pharmacophoric point of attachment of the inhibitor to the colchicine binding site of tubulin.     

Growth inhibition of estrogen receptor-positive and aromatase-positive human breast cancer cells in monolayer and spheroid cultures by letrozole, anastrozole, and tamoxifen

Two third-generation aromatase inhibitors, letrozole and anastrozole, and the antiestrogen tamoxifen, were compared for growth-inhibiting activity in two estrogen receptor (ER)-positive aromatase-overexpressing human breast cancer cell lines, MCF-7aro and T-47Daro. Inhibition of hormone (1 nM testosterone)-stimulated proliferation was evaluated in both monolayer cultures and in three-dimensional spheroid cultures. Letrozole and anastrozole were also compared for effectiveness of aromatase inhibition, and relative affinity for aromatase, under both monolayer and spheroid growth conditions. Letrozole was an effective inhibitor of MCF-7aro monolayer cell proliferation, with an estimated 50% inhibitory concentration (IC50) of 50-100 nM, whereas an IC50 was not reached with anastrozole at any concentration tested (100-500 nM). An IC50 of tamoxifen was 1000 nM. Proliferation of T-47Daro monolayer cells was more sensitive to inhibition by all three agents; as with MCF-7aro cells, letrozole was the most effective inhibitor. MCF-7aro spheroids were slightly less sensitive than monolayer cells proliferation-inhibiting effects of letrozole (IC50 about 200 nM), and there was no significant inhibition with 100-200 nM anastrozole or 200-1000 nM tamoxifen. Letrozole and anastrozole significantly inhibited T-47Daro spheroid cell proliferation, at 15-25 and 50 nM, respectively, consistent with the greater sensitivity of T-47Daro monolayer cells to inhibition of proliferation by these agents. Tamoxifen failed to significantly inhibit T-47Daro spheroid cell proliferation over a 100-500 nM concentration range. Determination of aromatase inhibition in monolayers of both cell lines by a direct-access microsomal assay and an intact-cell assay revealed that letrozole was more active than anastrozole in monolayers of both cell lines and in both assays. In MCF-7aro spheroids following cell lysis, only letrozole significantly inhibited aromatase activity, supporting the conclusion that letrozole binds stronger to aromatase than anastrozole does. Our results demonstrate that MCF-7aro and T-47Daro spheroids could be a suitable model for evaluation of growth-inhibitory effects of agents used in hormonal therapy of breast cancer.     

One-pot regioselective synthesis of tetrahydroindazolones and evaluation of their antiproliferative and Src kinase inhibitory activities

A number of 2-substituted tetrahydroindazolones were synthesized by three-component condensation reaction of 1,3-diketones, substituted hydrazines, benzaldehydes, and Yb(OTf)(3) as a catalyst in [bmim][BF(4)] ionic liquid using a simple, efficient, and economical one-pot method. The synthesized tetrahydroindazolones were evaluated for inhibition of cell proliferation of human colon carcinoma (HT-29), human ovarian adenocarcinoma (SK-OV-3), and c-Src kinase activity. 3,4-Dichlorophenyl tetrahydroindazolone derivative (15) inhibited the cell proliferation of HT-29 and SK-OV-3 cells by 62% and 58%, respectively. 2,3-Diphenylsubstituted tetrahydroindazolone derivatives, inhibited the cell proliferation of HT-29 cells by 65-72% at a concentration of 50 μM. In general, the tetrahydroindazolones showed modest inhibition of c-Src kinase where 4-tertbutylphenyl- and 3,4-dichlorophenyl- derivatives showed the inhibition of c-Src kinase with IC(50) values of 35.1 and 50.7 μM, respectively.     

Surfactin对人乳腺癌MCF-7细胞增殖、凋亡及细胞骨架的影响

以体外培养的人乳腺癌细胞株MCF-7为研究对象,探讨surfactin对肿瘤细胞增殖、凋亡及细胞骨架的影响。MTT实验表明,surfactin能抑制MCF-7的增殖,并且呈现出浓度和时间的依赖关系,作用48h时的IC50是27.3μmol/L。AO/EB荧光染色法及流式细胞术检测发现,surfactin可诱导MCF-7发生典型的凋亡形态学改变和G2/M期阻滞。免疫荧光和免疫印迹结果表明,surfactin显著抑制了细胞内vimentin的表达,诱导了α-tubulin的解聚和重排,使细胞的骨架系统发生了剧烈的变化。可见,surfactin具有抑制MCF-7细胞增殖,诱导细胞凋亡的作用,其机制可能与细胞骨架蛋白的表达水平有关。     

6-Nitrobenzimidazole derivatives: potential phosphodiesterase inhibitors: synthesis and structure-activity relationship

6-Nitrobenzimidazole derivatives (1-30) synthesized and their phosphodiesterase inhibitory activities determined. Out of thirty tested compounds, ten showed a varying degrees of phosphodiesterase inhibition with IC(50) values between 1.5±0.043 and 294.0±16.7 μM. Compounds 30 (IC(50)=1.5±0.043 μM), 1 (IC(50)=2.4±0.049 μM), 11 (IC(50)=5.7±0.113 μM), 13 (IC(50)=6.4±0.148 μM), 14 (IC(50)=10.5±0.51 μM), 9 (IC(50)=11.49±0.08 μM), 3 (IC(50)=63.1±1.48 μM), 10 (IC(50)=120.0±4.47 μM), and 6 (IC(50)=153.2±5.6 μM) showed excellent phosphodiesterase inhibitory activity, much superior to the standard EDTA (IC(50)=274±0.007 μM), and thus are potential molecules for the development of a new class of phosphodiesterase inhibitors. A structure-activity relationship is evaluated. All compounds are characterized by spectroscopic parameters.     

沉默Bmi-1基因表达对MCF-7细胞阿霉素敏感性的影响

目的研究Bmi-1对MCF-7细胞阿霉素敏感性的影响及机制。方法阿霉素处理MCF-7／Bmilsi、MCF-7／GFPsi和MCF一7细胞株,M1Tr法检测阿霉素的IC50;DAPI检测阿霉素处理后细胞的凋亡,计算凋亡指数（apoptosisindex,AI）;Western印迹检测相关蛋白P53,phospho—Akt（Ser473）（pAkt）,totle—Akt（tAkt）,Bcl-2,Bax的表达。结果阿霉素处理72h的MCF-7／Bmi．1si组生长抑制率明显高于MCF-7和MCF-7／GFPsi组,MCF-7／Bmilsi组的IC50为（0．15±0．02）μg／ml,而MCF-7组和MCF-7／GFPsi组的IC50分别为（0．87±0．06）μg/ml和（0．81±0．02）μg/ml（P〈0．05）。阿霉素处理48h后用DAPI检测凋亡发现,MCF-7／Bmi．lsi＋doxorubiein组可见大量凋亡细胞,而MCF-7＋doxorubicin和MCF-7／GFPsi＋doxo—rubicin组出现较少的凋亡细胞,MCF-7／Bmi-1si＋doxorubicin组凋亡指数明显高于对照组（P〈0．05）。进一步研究发现：MCF-7／Bmi．1si＋doxorubicin组与MCF-7＋doxorubiein及MCF-7／GFPsi＋doxorubiein组相比,P53表达量增加,tAkt表达未发生改变,而pAkt的表达明显减少,另外,Bcl-2表达量减少而Bax表达量增加,差异具有显著性（P〈0．05）。结论沉默Bmi—l基因表达能增加MCF-7细胞对阿霉素的敏感性,增加阿霉素引起的凋亡。     

Neo-tanshinlactone inspired synthesis, in vitro evaluation of novel substituted benzocoumarin derivatives as potent anti-breast cancer agents

A small library of novel benzocoumarin derivatives based on naturally occurring neo-tanshinlactone scaffold was constructed and their antiproliferative activities against breast cancer cells MCF-7 and MDA-MB-231 were evaluated. A number of derivatives showed good anti-breast cancer activity, in some cases higher to that of the reference compound tamoxifen. In particular, benzocoumarins Bc-5, Bc-8 and Bc-9 strongly inhibited the proliferation of MCF-7 cancer cell line with the IC(50) values of 3.8, 7.9 and 6.5 μM, respectively. The compounds were capable of inducing nuclear fragmentation, cell cycle arrest and caspase dependent apoptosis in MCF-7 cell lines. In addition, these derivatives were devoid of cytotoxic effect against normal osteoblast cells. These synthetic benzocoumarins hold promises for developing safer alternative to the existing anti-breast cancer agents.