Effect of Bmi-1 Expression on Chemotherapy Sensitivity in THP-1 Cells / 中国实验血液学杂志

OBJECTIVE@#To investigate the effect of Bmi-1 expression on the chemosensitivity of THP-1 cells and its relative mechanism.@*METHODS@#The pGenesil-2-Bmi-1 1 siRNA, p-MSCV-Bmi-1 plasmid was transfected into THP-1 cells to reduce or increase the expression of Bmi-1. The expression of Bmi-1 mRNA and protein was verified by PCR and Western blot. The effect of camptothecin (CPT) on the proliferation and chemosensitivity of THP-1 cells affected by Bmi-1 gene were detected by MTT assay. The expression of DNA double-strand breaks marker-γ-H2AX was detected by immunofluorescence assay. Mitochondrial membrane potential and apoptosis were observed by flow cytometry. The expression of Cytochrome C, Caspase 3, Bax and BCL-2 was detected by Western blot.@*RESULTS@#Silencing Bmi-1 could inhibit proliferation and enhance the sensitivity of THP-1 cells to CPT, while overexpressed Bmi-1 could promote the cell proliferation and attenucate sensitivity of THP-1 cells to CPT. Silencing Bmi-1 could enhance CPT-induced DNA double-strand breaks, decrease mitochondrial membrane potential and promote CPT-induced apoptosis. While increasing Bmi-1 gene expression could attenuate CPT-induced DNA double-strand breaks, enhamce mitochondrial membrane potential and significantly reduce CPT-induced apoptosis of cells.@*CONCLUSION@#Bmi-1 expression could influence the sensitivity of THP-1 cells to CPT, and its relative mechanism may relate to DNA double-strand breaks and endogenous apoptotic pathways.

Effect of Bmi-1 on Multidrug Resistance in K562/ADR Cells and Its Mechanisms / 中国实验血液学杂志

OBJECTIVE@#To investigate the effect of Bmi-1 gene silencing on drug resistance of leukemia cell K562/ADR and to explore its possible mechanism.@*METHODS@#After two sequences of Bmi-1-siRNA were transfected into drug-resistant K562/ADR cells, the mRNA and protein expressions of Bmi-1 gene were detected. After Bmi-1 gene silencing the expression of P-gp and MDR1 were detected and the accumulation of doxorubicin in K562/ADR cells were detected by flow cytometry to determine the effect of Bmi-1 gene silencing on drug resistance of K562/ADR cells. The protein expression of NF-κB was analyzed after Bmi-1 gene silencing. Then after K562/ADR cells were treated with NF-κB inhibitor PDTC, the protein expression of P-gp and its functional changes were analyzed to determine the effect of NF-κB on drug resistance of leukemia cells. The protein expressions of PTEN, AKT and p-AKT after Bmi-1 gene silencing were detected and the effect of Bmi-1 gene silencing on PTEN/PI3K/AKT signaling pathway in drug-resistant cells was determined. After K562/ADR cells were treated with PI3K/AKT pathway inhibitor LY294002, the protein expressions of NF-κB and P-gp were analyzed to determine the regulation of AKT on the expression of NF-κB and P-gp. The protein expressions of AKT, p-AKT, NF-κB and P-gp were detected after the Bmi-1-siRNA transfected cells were treated by PTEN inhibitor BPV. Above-mentioned expression of mRNA was detected by RT-PCR, and the protein expression was detected by Western blot.@*RESULTS@#The expression of Bmi-1 gene in K562/ADR cells decreased at both mRNA and protein levels and the doxorubicin accumulation increased after Bmi-1 gene silencing. The expression of MDR1/P-gp in Bmi-1-siRNA transfected cells was lower than that in K562/ADR cells (P＜0.05). After Bmi-1 gene silencing, the activity of NF-κB decreased. The activity of NF-κB and P-gp expression was inhibited and the function of P-gp in K562/ADR cells was reduced by using NF-κB inhibitor (PDTC). The protein expression of PTEN increased while the protein expression of p-AKT decreased after Bmi-1 gene silencing (P＜0.05). The protein expressions of p-AKT, P-gp and the activity of NF-κB were inhibited significantly by using PI3K/AKT inhibitor LY294002 (P＜0.05). After the Bmi-1-siRNA transfected cells were treated by PTEN inhibitor BPV, the activity of NF-κB and the protein expressions of P-gp were restored.@*CONCLUSION@#Bmi-1 plays a key role in MDR-mediated multidrug resistance in K562/ADR cells, which may be mediated by activating PTEN/AKT pathway to regulate NF-κB.