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Breast cancer is a malignant tumor with high mortality, and multidrug resistance (MDR) mediated by ABCG2 (ATP-Binding cassette G2) is an important cause of chemotherapy failure. It is an urgent problem to explore the mechanism of ABCG2-mediated drug resistance and its key molecules. Epithelial cell adhesion molecule (EpCAM) is involved in multiple tumor drug resistance and is closely related to breast cancer MDR. However, its role in ABCG2-mediated breast cancer drug resistance has not been clarified. The purpose of this study was to explore the regulation of EpCAM on ABCG2-mediated MDR in breast cancer cells and its mechanism. CCK8 cytotoxicity assays confirmed that the drug resistance of MCF-7/MX cell line to mitoxantrone (MX) was significantly increased compared with MCF-7 drug-sensitive strain of human breast cancer. Western blotting results showed that ABCG2 was highly expressed and EpCAM was up-regulated in MCF-7/MX cells compared with MCF-7. SiRNA knockdown of EpCAM in MCF-7/MX cells down-regulated ABCG2 expression and restored sensitivity to MX. Cell morphology was observed under an inverted microscope, and it was found that knocking down EpCAM reduced cell-cell connections between MCF-7/MX cells. The co-localization of EpCAM and claudin 1 in MCF-7/MX cells was observed by immunofluorescence. Furthermore, Western blotting results showed that EpCAM knockdown reduced claudin 1 expression in MCF-7/MX cells. In conclusion, EpCAM may promote ABCG2-mediated mMDR in breast cancers by enhancing intercellular tight junctions through interaction with claudin 1.
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Aim To investigate the role of aberrant cytokeratin 18(CK18) expression in breast cancer metastasis, anrl to elucidate the mechanism by identif¬ying its target.Methods The expression of CK.18 in human breast cancer tissues and cells was determined using immunohistochemical staining and Western blot, respectively.CK18 expression in human breast cancer MCF-7 cells was effectively down-regulated by shRNA, and its effect on breast cancer metastasis was further determined by scratch wound healing assay.The co-lo- cation of CK18 and non-muscle II A ( NMIIA) in MCF-7 cells was examined using double immunofluo¬rescence staining.The effect of CK18 down-regulation on the levels of NMIIA and c-Abl-ERK signaling was quantified by Western blot.Results Lower CK18 lev¬els was found in metastatic than that in primary breast cancer tissues and in highly invasive MDA-MB-231 than that in MCF-7 cells.CK.18 down-regulation pro¬moted the wound repair ability of MCF-7 cells 72h after scratch.CK18 and NMIIA were shown to co-locate in cytoplasm of MCF-7 cells.Moreover, down-regulation of CK18 increased NMIIA expression and activated the c-Abl-ERK signaling pathway in MCF-7 cells.Con¬clusions Down-regulation of CK18 could promote me¬tastasis of breast cancer, which is related to increased NMIIA expression and the activation of c-Abl-ERK sig¬naling pathway.
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Aim: To investigate the effect of epithelial cell adhesion molecule (EpCAM) on metastasis and multidrug resistance of breast cancer and its mechanism. Methods Immunohistochemical staining was employed to detect the expression of EpCAM in adjacent non-tumor tissues (ANTTs) and breast cancer tissues. siRNA was applied to knock down EpCAM expression in MDA-MB-231 cells. Transwell assay was used to detect the invasion and migration ability of breast cancer cells. Western blot analysis was performed to determine the protein expression of EpCAM, epithelial mesenchymal transition (EMT) markers E-cadherin, N-cadherin and vimentin, breast cancer resistance protein (BCRP), and β-catenin. Results EpCAM immunoreactivity was consistently stronger in primary breast cancer tissues and even higher in metastatic lesions than that in ANTTs. The expression of EpCAM was significantly upregulated in triple negative breast cancer MDA-MB-231 cells. EpCAM knockdown using siRNA decreased the invasion and migration ability and BCRP expression, and partially reversed the EMT phenotypes of MDA-MB-231 cells, β-catenin expression was upregulated in MDA-MB-231 cells. ICG-001, a specific Wnt/β-catenin pathway inhibitor, downregulated the expression levels of EpCAM, N-cadherin, and vimentin in MDA-MB-231 cells. Conclusions EpCAM could promote metastasis and drug resistance of breast cancer through the induction of EMT, which is related to the Wnt/β-catenin signaling pathway.
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Aim To investigate the effect of baicalein on the reversal of multidrug resistance ( MDR) media-ted by breast cancer resistance protein ( BCRP) in hu-man breast cancer MCF-7/MX cells, and explore the possible mechanisms. Methods MTT assay was per-formed to determine the cytotoxicity of baicalein and susceptibility of chemotherapeutic drugs. The protein expression levels of BCRP, p-p38 MAPK and NF-κB p65 were determined by Western blot. Results MCF-7/MX cells were not only resistant to MX but cross-re-sistant to 5-FU and DDP, and the resistance index was 70. 45, 6. 68 and 21. 47, respectively. 2. 5, 5μmol· L-1 of baicalein could increase the sensitivity to above chemotherapeutic agents and decrease the expression levels of BCRP, p-p38 MAPK and NF-κB p65 in MCF-7/MX cells. Conclusion Baicalein can effec-tively reverse MDR of MCF-7/MX by down-regulating BCRP expression through p38/MAPK and NF-κB path-ways.
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AIM:To investigate the effects of baicalein on pulmonary arterial hypertension(PAH)induced by monocrotaline(MCT)in rats,and its molecular mechanism was further explored.METHODS: Male SD rats(n=28) were randomly divided into 4 groups: control group, MCT group, MCT+baicalein 50 mg/kg group and MCT +baicalein 100 mg/kg group.The PAH model was established by subcutaneous injection of MCT.After 2 weeks of modeling,the rats in baicalein treatment groups were gavaged baicalein 50 and 100 mg· kg -1· d-1for 14 d,the rats in control group were administered with saline.After 4 weeks of modeling,right ventricular systolic pressure(RVSP),right ventricular hypertro-phy index(RVHI)and right ventricular mass index(RVMI)were detected.Masson staining was used to detect the degree of lung fibrosis.The pathomorphological changes of the pulmonary vessels were observed by HE staining.Western blot was used to detect the expression of α-smooth muscle actin(α-SMA)in the lung tissue and the phosphorylation p 38,ERK and JNK in the artery.RESULTS:Compared with the control group,RVSP, RVHI and RVMI increased significantly in the MCT group(P<0.01).Pulmonary fibrosis and the thickening of pulmonary artery wall were observed.α-SMA was up-regulated and p38,ERK and JNK was activated significantly(P<0.01).Compared with the MCT group,baicalein(50 and 100 mg/kg)significantly decreased the RVSP,RVHI and RVMI(P<0.01).Lung fibrosis was reduced and the vas-cular wall thickening was decreased in baicalein-treated groups.Baicalein(50 and 100 mg/kg)inhibited the phosphoryla-tion of p38,ERK and JNK compared with the MCT group(P<0.01).CONCLUSION:Baicalein ameliorates MCT-in-duced PAH by the inhibition of pulmonary artery wall thickening at least partially via MAPK signaling pathway.
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<p><b>OBJECTIVE</b>To observe the cytotoxicity of indirubin derivative PHII-7 against human breast cancer MCF-7 cells and to study its primary mechanisms.</p><p><b>METHODS</b>The proliferation of MCF-7 cells was detected using MTT colorimetry. Annexin V/PI double staining was applied to detect the apoptosis rate of MCF-7 cells. The distribution of cell cycles was detected using PI staining and flow cytometry (FCM). The levels of reactive oxygen species (ROS) in MCF-7 cells were detected by DCFH-DA staining. The mRNA and protein levels of c-fos were detected using RT-PCR and Westem blot analysis.</p><p><b>RESULTS</b>PHII-7 at different concentrations inhibited the proliferation of MCF-7 cells in a concentration-dependent manner, with the inhibitory rate ranging from 43.13% to 90.90% (P < 0.05). The inhibition was strengthened along with increased concentrations. PHII-7 at different concentrations could induce the apoptosis of MCF-7 cells. The early apoptosis rate was 1.43% +/- 0.02%, 9.14% +/- 0.36%, and 45.79% +/- 8.46%, respectively with the action of 1.25, 2.50, and 5.00 micromol/L PHII-7, respectively, showing dose-dependent manner. FCM analysis found that the proportion of MCF-7 cells in the G0/G1 phase and the S phase decreased after treatment with PHII-7, and the ratio of MCF-7 cells in the G2/M phase obviously increased (P < 0.01). The intra-cellular ROS level was significantly elevated 2 h after pretreatment with PHII-7. The levels of the protooncogene c-fos mRNA and protein were down-regulated in a dose-dependent manner after action of PHII-7.</p><p><b>CONCLUSIONS</b>PHII-7 exerted obvious in vitro cytotoxic effects on MCF-7 cells. Its mechanisms might be associated with arresting the cell cycle, regulating the redox equilibrium, and down-regulating the expression of the protooncogene.</p>