Epithelial cell adhesion molecule promotes breast cancer resistance protein-mediated multidrug resistance in breast cancer by inducing partial epithelial-mesenchymal transition.

Overexpression of breast cancer resistance protein (BCRP) plays a crucial role in the acquired multidrug resistance (MDR) in breast cancer. The elucidation of molecular events that confer BCRP-mediated MDR is of major therapeutic importance in breast cancer. Epithelial cell adhesion molecule (EpCAM) has been implicated in tumor progression and drug resistance in various types of cancers, including breast cancer. However, the role of EpCAM in BCRP-mediated MDR in breast cancer remains unknown. In the present study, we revealed that EpCAM expression was upregulated in BCRP-overexpressing breast cancer MCF-7/MX cells, and EpCAM knockdown using siRNA reduced BCRP expression and increased the sensitivity of MCF-7/MX cells to mitoxantrone (MX). The epithelial-mesenchymal transition (EMT) promoted BCRP-mediated MDR in breast cancer cells, and EpCAM knockdown partially suppressed EMT progression in MCF-7/MX cells. In addition, Wnt/ß-catenin signaling was activated in MCF-7/MX cells, and the inhibition of this signaling attenuated EpCAM and BCRP expression and partially reversed EMT. Together, this study illustrates that EpCAM upregulation by Wnt/ß-catenin signaling induces partial EMT to promote BCRP-mediated MDR resistance in breast cancer cells. EpCAM may be a potential therapeutic target for overcoming BCRP-mediated resistance in human breast cancer.

[The cytotoxicity of indirubin derivative PHII-7 against human breast cancer MCF-7 cells and its mechanisms].

OBJECTIVE: To observe the cytotoxicity of indirubin derivative PHII-7 against human breast cancer MCF-7 cells and to study its primary mechanisms. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

[Effects of PKCα/c-fos, Bax/Bcl-2 expression on the proliferation and apoptosis of rat pulmonary arterial smooth muscle cells in hypoxia].

OBJECTIVE: To explore the effects of PKCα/c-fos, Bax/Bcl-2 on the proliferation and apoptosis of rat pulmonary arterial smooth musclecells(PASMCs) in hypoxia. METHODS: The PASMCs of rats had been isolated and cultured, and then were cultured under normoxia (5%CO2、21%O2、74%N2)and hypoxia(5%CO2,2% O2,93%N2)condition for 24 h and 48 h, respectively. The proliferation of PASMCs was tested by methylthiazolyltetrazolium (MTT). The changes of PASMCs apoptosis were detected by Annexin V-FITC/PI staining combined flow cytometry. RT-PCR and Western blot analysis were performed to detect the gene and protein levels of PKCα/c-fos, Bax/Bcl-2, respectively. All experiments were repeated three times with at least triplicate samples. RESULTS: The proliferation of PASMCs in hypoxia group were stronger than that of normoxia group after 24 h and 48 h (P < 0.01), while the apoptosis rate did not change significantly. Meanwhile, the higher levels of PKCα, c-fos, Bcl-2 mRNA and proteins after hypoxia for 24 h and 48 h were detected by RT-PCR and Western blot analysis, while the ex-pression levels of Bax had no significant difference under normoxic and hypoxic conditions. CONCLUSIONS: Elevated proliferation and expression of PKCα, c-fos, Bcl-2 was observed in rat PASMCs in hypoxia, and while the apoptosis rate had no significant change.

Ginsenoside Rg1 reduces toxicity of PM(2.5) on human umbilical vein endothelial cells by upregulating intracellular antioxidative state.

Ambient airborne particulate matter (PM) is an important environmental pollutant responsible for many human diseases. Oxidative stress is suggested to be involved in PM-induced cell injury. The present study is designed to study unsalutary effects of the organic extracts of PM with an aerodynamic diameter of less than 2.5µm (PM(2.5)) and protective effect of Ginsenoside Rg1 (Rg1) against PM(2.5) on human umbilical vein endothelial cells (HUVECs) in vitro. Cytotoxic effects of the organic extract PM(2.5) on HUVECs were measured by means of HUVEC cell viability and the generation of intracellular reactive oxygen species (ROS). Expression of heme oxygenase-1(HO-1) and Nuclear factor-erythroid 2-related factor 2 (Nrf2) and Nrf2 cytoplasm-nucleus location were assayed. The present results showed that PM(2.5) (50-800µg/ml) decreased HUVEC viability and increased intracellular generation of ROS and malondialdehyde (MDA) in a concentration dependent manner, but increased HO-1 expression without concentration dependence. Rg1 (10 and 40µg/ml) diminished PM(2.5)-induced HUVEC viability, decrease ROS and MDA generation, increased HO-1 and Nrf2 expression and promoted Nrf2 translocation to nucleus in a concentration dependent manner. These results suggested that organic extracts of PM(2.5) increase oxidative stress and decrease cell viability; Rg1 antagonize PM(2.5)-induced excess oxidative stress; HO-1 expression increase and Nrf2 translocation to nucleus may be involved in the effects of both PM(2.5) and Rg1 on HUVECs.