Autophagic cell death, polyploidy and senescence induced in breast tumor cells by the substituted pyrrole JG-03-14, a novel microtubule poison

JG-03-14, a substituted pyrrole that inhibits microtubule polymerization, was screened against MCF-7 (p53 wild type), MDA-MB231 (p53 mutant), MCF-7/caspase 3 and MCF-7/ADR (multidrug resistant) breast tumor cell lines. Cell viability and growth inhibition were assessed by the crystal violet dye assay. Apoptosis was evaluated by the TUNEL assay, cell cycle distribution by flow cytometry, autophagy by acridine orange staining of vesicle formation, and senescence based on beta-galactosidase staining and cell morphology. Our studies indicate that exposure to JG-03-14, at a concentration of 500 nM, induces time-dependent cell death in the MCF-7 and MDA-MB231 cell lines. In MCF-7 cells, a residual surviving cell population was found to be senescent; in contrast, there was no surviving senescent population in treated MDA-MB231 cells. No proliferative recovery was detected over a period of 15 days post-treatment in either cell line. Both the TUNEL assay and FLOW cytometry indicated a relatively limited degree of apoptosis (<10%) in response to drug treatment in MCF-7 cells with more extensive apoptosis (but <20%) in MDA-MB231 cells; acidic vacuole formation indicative of autophagic cell death was relatively extensive in both MCF-7 and MDA-MB231 cells. In addition, JG-03-14 induced the formation of a large hyperdiploid cell population in MDA-MB231 cells. JG-03-14 also demonstrated pronounced anti-proliferative activity in MCF-7/caspase 3 cells and in the MCF-7/ADR cell line. The observation that JG-03-14 promotes autophagic cell death and also retains activity in tumor cells expressing the multidrug resistance pump indicates that novel microtubule poisons of the substituted pyrroles class may hold promise in the treatment of breast cancer.     

三阴性乳腺癌新型靶向治疗药物研究进展

三阴性乳腺癌（TNBC）即雌激素受体（ER）、孕激素受体（PR）和人表皮生长因子受体-2（HER-2）表达均为阴性的乳腺癌,是一种异质性疾病,通常具有较高的组织学级别,较激素受体阳性乳腺癌更具侵袭性,且易发生内脏转移。目前,临床对TNBC多采用细胞毒性药物进行常规化疗,但极易产生骨髓抑制、神经毒性等不良反应,导致患者不耐受。使用铂类药物治疗转移性TNBC,药效持续时间短、毒性大,中位总生存期仅9～12个月。鉴于TNBC的化疗效果欠佳,临床迫切需要寻找新的靶向治疗药物,从而根据患者的肿瘤分子亚型制定有效的治疗方案。本文主要就TNBC新型靶向治疗药物的研究进展作一综述。     

Triple negative breast cancer: a brief review of its characteristics and treatment options

Triple negative breast cancer (TNBC), an aggressive variant of breast cancer, is characterized by lack of expression of the estrogen (ER) and progesterone receptors (PRs) and the human epidermal growth factor receptor (HER-2) that are commonly observed in other breast cancer subtypes. The TNBC subtype primarily occurs in younger women of African American or Hispanic descent and tumors tend to be high grade and initially responsive to chemotherapy. However, TNBC is characteristically aggressive with high recurrence, metastatic, and mortality rates. Treatment options are limited since the hormonal receptor and HER-2 antagonists typically used for other breast cancers are ineffective. As such, the mainstay of treatment of TNBC is traditional systemic cytotoxic chemotherapy. Potential future therapies for TNBC include targeted molecular strategies including poly (adenosine diphosphate ribose) polymerase (PARP) and epidermal growth factor receptor (EGFR) inhibitors and antiangiogenic agents. Further research aimed at identifying unique genetic characteristics of TNBC may allow development of other targeted molecular chemotherapy treatment options.     

Apigenin inhibits HGF-promoted invasive growth and metastasis involving blocking PI3K/Akt pathway and beta 4 integrin function in MDA-MB-231 breast cancer cells

Hepatocyte growth factor (HGF) and its receptor, Met, known to control invasive growth program have recently been shown to play crucial roles in the survival of breast cancer patients. The diet-derived flavonoids have been reported to possess anti-invasion properties; however, knowledge on the pharmacological and molecular mechanisms in suppressing HGF/Met-mediated tumor invasion and metastasis is poorly understood. In our preliminary study, we use HGF as an invasive inducer to investigate the effect of flavonoids including apigenin, naringenin, genistein and kaempferol on HGF-dependent invasive growth of MDA-MB-231 human breast cancer cells. Results show that apigenin presents the most potent anti-migration and anti-invasion properties by Boyden chamber assay. Furthermore, apigenin represses the HGF-induced cell motility and scattering and inhibits the HGF-promoted cell migration and invasion in a dose-dependent manner. The effect of apigenin on HGF-induced signaling activation involving invasive growth was evaluated by immunoblotting analysis, it shows that apigenin blocks the HGF-induced Akt phosphorylation but not Met, ERK, and JNK phosphorylation. In addition to MDA-MB-231 cells, apigenin exhibits inhibitory effect on HGF-induced Akt phosphorylation in hepatoma SK-Hep1 cells and lung carcinoma A549 cells. By indirect immunofluorescence microscopy assay, apigenin inhibits the HGF-induced clustering of beta 4 integrin at actin-rich adhesive site and lamellipodia through PI3K-dependent manner. Treatment of apigenin inhibited HGF-stimulated integrin beta 4 function including cell-matrix adhesion and cell-endothelial cells adhesion in MDA-MB-231 cells. By Akt-siRNA transfection analysis, it confirmed that apigenin inhibited HGF-promoted invasive growth involving blocking PI3K/Akt pathway. Finally, we evaluated the effect of apigenin on HGF-promoted metastasis by lung colonization of tumor cells in nude mice and organ metastasis of tumor cells in chick embryo. By histological and gross examination of mouse lung and real-time PCR analysis of human alu in host tissues, it showed that apigenin, wortmannin, as well as anti-beta 4 antibody all inhibit HGF-promoted metastasis. These data support the inhibitory effect of apigenin on HGF-promoted invasive growth and metastasis involving blocking PI3K/Akt pathway and integrin beta 4 function.     

The apple polyphenol phloretin inhibits breast cancer cell migration and proliferation via inhibition of signals by type 2 glucose transporter

Human triple-negative breast cancer (TNBC) is the most aggressive and poorly understood subclass of breast cancer. Glucose transporters (GLUTs) are required for glucose uptake in malignant cancer cells and are ideal targets for cancer therapy. To determine whether the inhibition of GLUTs could be used in TNBC cell therapy, the apple polyphenol phloretin (Ph) was used as a specific antagonist of GLUT2 protein function in human TNBC cells. Interestingly, we found that Ph (10–150 μM, for 24 h) inhibited cell growth and arrested the cell cycle in MDA-MB-231 cells in a p53 mutant-dependent manner, which was confirmed by pre-treatment of the cells with a p53-specific dominant-negative expression vector. We also found that Ph treatment (10–150 μM, for 24 h) significantly decreased the migratory activity of the MDA-MB-231 cells through the inhibition of paxillin/FAK, Src, and alpha smooth muscle actin (α-sMA) and through the activation of E-cadherin. Furthermore, the anti-tumorigenic effect of Ph (10, 50 mg/kg or DMSO twice a week for six weeks) was demonstrated in vivo using BALB/c nude mice bearing MDA-MB-231 tumor xenografts. A decrease in N-cadherin, vimentin and an increase in p53, p21 and E-cadherin were detected in the tumor tissues. In conclusion, inhibition of GLUT2 by the apple polyphenol Ph could potentially suppress TNBC tumor cell growth and metastasis.     

Curcumin-induced antitumor effects on triple-negative breast cancer patient-derived xenograft tumor mice through inhibiting salt-induced kinase-3 protein

This study demonstrated for the first time that curcumin effectively inhibits the growth of triple-negative breast cancer (TNBC) tumors by inhibiting the expression of salt-induced kinase-3 (SIK3) protein in patient-derived xenografted tumor mice (TNBC-PDX). For TNBC patients, chemotherapy is the only option for postoperative adjuvant treatment. In this study, we detected the SIK3 mRNA expression in paired-breast cancer tissues by qPCR analysis. The results revealed that SIK3 mRNA expression was significantly higher in tumor tissues when compared to the normal adjacent tissues (73.25 times, n = 183). Thus, it is proposed for the first time that the antitumor effect induced by curcumin by targeting SIK3 can be used as a novel strategy for the therapy of TNBC tumors. In vitro mechanism studies have shown that curcumin (>25 μM) inhibits the SIK3-mediated cyclin D upregulation, thereby inhibiting the G1/S cell cycle and arresting TNBC (MDA-MB-231) cancer cell growth. The SIK3 overexpression was associated with increased mesenchymal markers (i.e., Vimentin, α-SMA, MMP3, and Twist) during epithelial–mesenchymal transition (EMT). Our results demonstrated that curcumin inhibits the SIK3-mediated EMT, effectively attenuating the tumor migration. For clinical indications, dietary nutrients (such as curcumin) as an adjuvant to chemotherapy should be helpful to TNBC patients because the current trend is to shrink the tumor with preoperative chemotherapy and then perform surgery. In addition, from the perspective of chemoprevention, curcumin has excellent clinical application value.     

Improved delivery of miR-1296 loaded cationic nanoliposomes for effective suppression of triple negative breast cancer

Nowadays, microRNA is considered an attractive strategy for the effective treatment of cancer. A significant delivery of microRNA for cancer therapy remains a significant obstacle to target cancer cells. The restoring microRNA-1296 (miR-1296) has immense therapeutic efficacy in triple-negative breast cancer (TNBC). TNBC is an aggressive subtype of breast tumors with the progression of malignant transformation. This study aimed to develop a cationic nanoliposome that can serve as a miR-1296 carrier and studied its efficiency in TNBC. The efficacy of miR-1296 liposomes was evaluated on its apoptotic effect, cellular uptake, and potential chemotherapy sensitization in the TNBC cell line (MDA-MB-231). For in vitro viability study, the apoptotic effect was performed to validate protein expression using Alamar blue kit and western blot. The transfection of miR-1296 into TNBC cells was also investigated using cisplatin as a TNBC resistance drug. The fluorescent miR-1296-cy3 liposome was used for cellular uptake study. The miR-liposome was successfully prepared with a particle size of 123.6 ± 1.3 nm and encapsulation efficiency of 94.33%. A dose of 0.5 uM has significantly reduced the viability of MDA-MB-231 to be 33.45%±5.29 (P < 0.001). This result was validated by down-expression of CCND1, and PARP1, the miR-1296 receptor, and apoptosis marker. The image of the miR-1296-cy3 liposome showed cytoplasmic intracellular localization. It was found high sensitization of TNBC cell line for miR-1296 liposome compared to cisplatin (P < 0.001). Future in vivo research may answer questions concerning safety and stability. This study demonstrates that miR-191 liposomes may have promising clinical applications for TNBC therapy.     

Bisphenol A induces focal adhesions assembly and activation of FAK,Src and ERK2 via GPER in MDA-MB-231 breast cancer cells

Bisphenol A (BPA) is an industrial synthetic chemical used in the production of polycarbonate plastics and epoxy resins. Human exposition to BPA is primarily through eating food, and drinking liquids, because BPA can leach from polycarbonate plastic containers, beverage cans and epoxy resins. BPA induces proliferation and migration in human breast cancer cells. The G protein-coupled estrogen receptor (GPER) is a G protein-coupled receptor coupled with Gs proteins that is activated by estrogen and estrogenic compounds and it is the receptor for BPA. However, the signal transduction pathways that mediate migration via BPA/GPER in triple negative breast cancer (TNBC) cells has not been studied in detail. Here, we demonstrate that BPA induces an increase of GPER expression and activation of FAK, Src and ERK2, and an increase of focal adhesion assembly via GPER in TNBC MDA-MB-231 cells. Moreover, BPA induces FAK and ERK2 activation, focal adhesion assembly and migration via epidermal growth factor receptor (EGFR) transactivation. Collectively our data showed that BPA via GPER and/or EGFR transactivation induces activation of signal transduction pathways that mediate migration in TNBC MDA-MB-231 cells.     

三阴性乳腺癌靶向治疗研究进展

三阴性乳腺癌（TNBC）作为乳腺癌一种预后较差的亚型,在出现化疗药物抵抗的情况下,由于缺少其他有效治疗方法,疾病往往易快速复发转移。因此针对TNBC新治疗靶点及靶向药物的研究已成为目前国内外研究热点。本文主要针对目前TNBC靶向治疗研究进展进行总结分析,主要包括ADP合同聚合酶抑制剂、抗血管生成靶向药物、抗表皮生长因子受体信号通路靶向药物、雄激素受体拮抗剂、免疫检查点抑制剂、PI3K-AKT-mTOR通路抑制剂等,以期从中找出最有可能成为未来发展方向的靶向治疗方法。     

Acetaminophen-induced differentiation of human breast cancer stem cells and inhibition of tumor xenograft growth in mice

It is now believed that cancer stem cells (CSCs) that are resistant to chemotherapy due to their undifferentiated nature drive tumor growth, metastasis and relapse, so development of drugs that induce differentiation of CSCs should have a profound impact on cancer eradication. In this study, we screened medicines that are already in clinical use for drugs that induce differentiation of CSCs. We used MDA-MB-231, a human breast cancer cell line that contains cancer stem cell-like cells. We found that acetaminophen, an anti-inflammatory, antipyretic and analgesic drug, induces differentiation of MDA-MB-231 cells. Differentiation was assessed by observing alterations in cell shape and expression of differentiated and undifferentiated cell markers, a decrease in cell invasion activity and an increase in susceptibility to anti-tumor drugs. This increased susceptibility seems to involve suppression of expression of multidrug efflux pumps. We also suggest that this induction of differentiation is mediated by inhibition of a Wnt/β-catenin canonical signaling pathway. Treatment of MDA-MB-231 cells with acetaminophen in vitro resulted in the loss of their tumorigenic ability in nude mice. Furthermore, administration of acetaminophen inhibited the growth of tumor xenografts of MDA-MB-231 cells in both the presence and absence of simultaneous administration of doxorubicine, a typical anti-tumor drug for breast cancer. Analysis with various acetaminophen derivatives revealed that o-acetamidophenol has a similar differentiation-inducing activity and a similar inhibitory effect on tumor xenograft growth. These results suggest that acetaminophen may be beneficial for breast cancer chemotherapy by inducing the differentiation of CSCs.     

Pifithrin-α, an inhibitor of p53 transactivation, up-regulates COX-2 expression through an MAPK-dependent pathway

Cyclooxygenase-2 (COX-2) has been reported to be elevated in many cancers, including breast and colorectal cancers, resulting in accumulation of prostaglandin E? in the cancer cell environment. In this study, we investigated the effect of pifithrin (PFT)-α, an inhibitor of p53 transactivation, on COX-2 expression in breast and fibrosarcoma cells. Our results showed that COX-2 expression was dose-dependently increased by PFT-α in MDA-MB231 breast cancer cells with mutant p53. In addition, the expression level of COX-2 was also increased by PFT-α in normal fibroblasts as well as in HT1080 fibrosarcoma cells with p53 wild-type cells. To verify the regulatory mechanism of COX-2 in response to PFT-α, we pretreated cells with a mitogen-activated protein kinase (MAPK) kinase (MEK)1/2 inhibitor (UO126) and a phosphoinositide-3 (PI-3K) inhibitor (LY294002). PFT-α-induced COX-2 expression was significantly decreased by UO126 and LY294002 in MDA-MB231 cells. However, the phosphorylation of extracellular signal-regulated kinase (ERK) was increased by PFT-α, but not Akt phosphorylation. Finally, we confirmed the correlation of the MEK and PI-3K pathway and COX-2 expression using the constitutively active (CA)-MEK and myr-Akt adenovirus systems. COX-2 expression was increased by CA-MEK transfection, but not by myr-Akt. Taken together, we have demonstrated that PFT-α-induced COX-2 expression is regulated through a MEK/ERK pathway in MDA-MB231 human breast cancer cells.     

Lenvatinib- and vadimezan-loaded synthetic high-density lipoprotein for combinational immunochemotherapy of metastatic triple-negative breast cancer

Metastatic triple-negative breast cancer (TNBC) is the most aggressive type of breast cancer. Combination of systemic chemotherapy and immune checkpoint blockade is effective but of limited benefit due to insufficient intratumoral infiltration of cytotoxic T lymphocytes (CTLs) and the accumulation of immunosuppressive cells. Herein, we designed a lenvatinib- and vadimezan-loaded synthetic high-density lipoprotein (LV-sHDL) for combinational immunochemotherapy of metastatic TNBC. The LV-sHDL targeted scavenger receptor class B type 1-overexpressing 4T1 cells in the tumor after intravenous injection. The multitargeted tyrosine kinase inhibitor (TKI) lenvatinib induced immunogenic cell death of the cancer cells, and the stimulator of interferon genes (STING) agonist vadimezan triggered local inflammation to facilitate dendritic cell maturation and antitumor macrophage differentiation, which synergistically improved the intratumoral infiltration of total and active CTLs by 33- and 13-fold, respectively. LV-sHDL inhibited the growth of orthotopic 4T1 tumors, reduced pulmonary metastasis, and prolonged the survival of animals. The efficacy could be further improved when LV-sHDL was used in combination with antibody against programmed cell death ligand 1. This study highlights the combination use of multitargeted TKI and STING agonist a promising treatment for metastatic TNBC.     

Low doses of Paclitaxel repress breast cancer invasion through DJ‐1/KLF17 signalling pathway

Paclitaxel (taxol) is an important agent against many tumours, including breast cancer. Ample data documents that paclitaxel inhibits breast cancer metastasis while others prove that paclitaxel enhances breast cancer metastasis. The mechanisms by which paclitaxel exerts its action are not well established. This study focuses on the effect of paclitaxel, particularly the low doses on breast cancer metastasis and the mechanisms that regulate it. Current results show that, paclitaxel exerts significant cytotoxicity even at low doses in both MCF‐7 and MDA‐MB‐231 cells. Interestingly, paclitaxel significantly inhibits cell invasion and migration, decreases Snail and increases E‐cadherin mRNA expression levels at the indicated low doses. Furthermore, paclitaxel‐inhibiting breast cancer metastasis is associated with down‐regulation of DJ‐1 and ID‐1 mRNA expression level with a concurrent increase in KLF17 expression. Under the same experimental conditions, paclitaxel induces KLF17 and concurrently represses ID‐1 protein levels. Our results show for the first time that paclitaxel inhibits breast cancer metastasis through regulating DJ‐1/KLF17/ID‐1 signalling pathway; repressed DJ‐1 and ID‐1 and enhanced KLF17 expression.     

Preclinical Evaluation of Ixabepilone in Combination with VEGF Receptor and PARP Inhibitors in Taxane-Sensitive and Taxane-Resistant MDA-MB-231 Breast Cancer Cells

Long-term use of cytotoxic agents promotes drug-resistance in triple-negative breast cancer (TNBC). The identification of new drug combinations with efficacy against drug-resistant TNBC cells in vitro is valuable in developing new clinical strategies to produce further cancer remissions. We undertook combination analysis of the cytotoxic agent ixabepilone with small molecule inhibitors of vascular endothelial growth factor receptor (VEGFR) and poly (ADP-ribose) polymerase (PARP) in taxane-sensitive (231C) and taxane-resistant (TXT) MDA-MB-231-derived cells. As single agents, the VEGFR inhibitors cediranib and bosutinib decreased both 231C and TXT cell viability, but four other VEGFR inhibitors and two PARP inhibitors were less effective. Combinations of ixabepilone with either cediranib or bosutinib synergistically decreased 231C cell viability. However, only the ixabepilone/cediranib combination was synergistic in TXT cells, with predicted 15.3-fold and 1.65-fold clinical dose reductions for ixabepilone and cediranib, respectively. Flow cytometry and immunoblotting were used to further evaluate the loss of cell viability. Thus, TXT cell killing by ixabepilone/cediranib was enhanced over ixabepilone alone, and expression of proapoptotic cleaved caspase-3 and the Bak/Bcl-2 protein ratio were increased. These findings suggest that the synergistic activity of the ixabepilone/cediranib combination in taxane-sensitive and taxane-resistant cells may warrant clinical evaluation in TNBC patients.     

Targeting androgen receptor and trail:a novel treatment paradigm for breast cancer

OBJECTIVE TNF-related apoptosis-inducing ligand(TRAIL)is a promising cancer therapeutic agent due to its minimal toxicity to normal tissues and remarkable apoptotic activity in tumors.However,most breast cancer cells are resistant to TRAIL-induced apoptosis.Our objectives are to investigate the underlying molecular mechanisms and to develop strategies to overcome such resistance.METHODS To identify modulators of TRAIL-induced apoptosis,we carried out a genome wide si RNA screen.To validate the screening result,we either silenced or overexpressed the identified genes in various breast cancer cells and changes in growth and TRAIL-induced cell apoptosis were determined in vitro and in an orthotopic xenograft mouse model.Finally,we investigated whether small molecules targeting the identified genes improve the effectiveness of TRAIL-therapy.RESULTS We unexpectedly identified androgen receptor(AR)to be responsible for TRAIL resistance.While AR is classically viewed as the key factor in prostate cancer progression,we found that AR expression levels were markedly elevated in human invasive breast cancer specimens including triple-negative breast cancers(TNBC)that are highly aggressive with poor prognosis.Importantly,breast cancer cell lines express different levels of AR that correlated with their TRAIL resistance.AR overexpression in MDA-MB-231 and MDA-MB-436 cells suppressed the TRAIL sensitivity whereas knockdown of AR rendered MCF-7 and MDA-MB-453 cells sensitive to TRAIL-induced apoptosis.AR overexpression also induced TRAIL resistance in breast tumors in vivo.Further,we observed an upregulation of the TRAIL receptor,death receptor 5(DR5)in breast cancer cells,following the removal or inhibition of AR by its antagonists Casodex and MDV3100.Treatment with AR antagonists also enhanced TRAIL-induced breast cancer cell apoptosis.CONCLUSION AR signaling suppresses TRAIL-induced breast cancer cell apoptosis,in part,by suppressing DR5 expression,and a combination of AR antagonists together with TRAIL may be a novel and effective therapy for TNBC.     

A neutrophil-biomimic platform for eradicating metastatic breast cancer stem-like cells by redox microenvironment modulation and hypoxia-triggered differentiation therapy

Metastasis accounts for 90% of breast cancer deaths, where the lethality could be attributed to the poor drug accumulation at the metastatic loci. The tolerance to chemotherapy induced by breast cancer stem cells (BCSCs) and their particular redox microenvironment further aggravate the therapeutic dilemma. To be specific, therapy-resistant BCSCs can differentiate into heterogeneous tumor cells constantly, and simultaneously dynamic maintenance of redox homeostasis promote tumor cells to retro-differentiate into stem-like state in response to cytotoxic chemotherapy. Herein, we develop a specifically-designed biomimic platform employing neutrophil membrane as shell to inherit a neutrophil-like tumor-targeting capability, and anchored chemotherapeutic and BCSCs-differentiating reagents with nitroimidazole (NI) to yield two hypoxia-responsive prodrugs, which could be encapsulated into a polymeric nitroimidazole core. The platform can actively target the lung metastasis sites of triple negative breast cancer (TNBC), and release the escorted drugs upon being triggered by the hypoxia microenvironment. During the responsiveness, the differentiating agent could promote transferring BCSCs into non-BCSCs, and simultaneously the nitroimidazole moieties conjugated on the polymer and prodrugs could modulate the tumor microenvironment by depleting nicotinamide adenine dinucleotide phosphate hydrogen (NADPH) and amplifying intracellular oxidative stress to prevent tumor cells retro-differentiation into BCSCs. In combination, the BCSCs differentiation and tumor microenvironment modulation synergistically could enhance the chemotherapeutic cytotoxicity, and remarkably suppress tumor growth and lung metastasis. Hopefully, this work can provide a new insight in to comprehensively treat TNBC and lung metastasis using a versatile platform.     

Magnolia dealbata seeds extract exert cytotoxic and chemopreventive effects on MDA-MB231 breast cancer cells

Context: Cancer prevention remains a high priority for the scientific world. Magnolia dealbata Zucc (Magnoliaceae), a Mexican endemic species, is used for the empirical treatment of cancer.

Objective: To evaluate the cytotoxic and cancer chemopreventive effects of an ethanol extract of Magnolia dealbata seeds (MDE).

Materials and methods: The cytotoxic effect of MDE, at concentrations ranging from 1 to 200?µg/ml, on human cancer cells and human nontumorigenic cells was evaluated using the MTT assay for 48?h. The apoptotic activities of MDE 25?μg/ml on MDA-MB231 breast cancer cells were evaluated using the TUNEL assay and the detection of caspase 3 using immunofluorescence analysis for 48?h, each. The chemopreventive effect was evaluated by administrating different doses of MDE, between 1 and 50?mg/kg, injected intraperitoneally daily into athymic mice which were implanted with MDA-MB231 cells during 28 days. The growth and weight of tumors were measured.

Results: MDE showed cytotoxic effects on MDA-MB231 cells (IC₅₀?=?25?µg/ml) and exerted pro-apoptotic activities as determined by DNA fragmentation in MDA-MB231 cells. MDE 25?µg/ml also induces the activation of caspase 3 in MDA-MB231 cells. These results suggest that Magnolia dealbata may be an optimal source of the bioactive compounds: honokiol (HK) and magnolol (MG). MDE 50?mg/kg i.p. exerted chemopreventive effects by inhibiting the growth of MDA-MB231 tumor by 75% in athymic mice, compared to the control group.

Conclusions: MDE exerts cytotoxic, apoptotic and chemopreventive activities on MDA-MB231 human cancer cells.