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.

Bmi-1-siRNA Regulates the Proliferation of K562 Leukemia Cells in vitro and in vivo by PTEN/pAKT Pathway / 中国实验血液学杂志

OBJECTIVE@#To investigate the effect of Bmi-1 gene silence on the proliferation ability of K562 cells in vitro and in vivo, and to explore the relation of molecular mechanism between proliferation ability of K562 cells in vitro and in vivo with PTEN/pAKT signaling pathway.@*METHODS@#The Bmi-1 small interference RNA (siRNA) sequences were transfected into K562 cells for decreasing Bmi-1 expression. The effect of Bmi-1 siRNA on the proliferation of K562 cells in vitro and in vivo was detected by MTT method and colony-forming test, the effect of Bmi-1 siRNA on the tumorogenicity of K562 cells was observed by subcutaneous inoculation of K562 cells, LY294002 and Bpv treated K562 cells in nude mice, the expression of Bmi-1, PTEN and pAKT proteins were detected by Western blot.@*RESULTS@#The Bmi-1 siRNA could inhibit the proliferation activity, colony-forming and tumor-forming abilities of K562 cells. After the silence of Bmi-1 gene, the PTEN expression in Bmi-1 gene-silenced group was significantly enhanced. While the pAKT expression in Bmi-1 gene-silenced group was significantly reduced; after the K562 cells were treated with LY294002 (an inhibitor of pAKT), the pAKT expression colony-forming and tumor forming abilities were reduced in comparison with untreated K562 cells; after the K562-S1 cells were treated with Bpv (an inhibitor of PTEN), the PTEN expression decreased, while the pAKT expression, colony forming and tumor-forming abilities were restored.@*CONCLUSION@#The Bmi-1 gene possibly involves in regulation of K562 proliferation in vivo and in vitro, the effect of PTEN/pAKT signaling pathway maybe one of molecular mechanisms mediating this regulation.

Effects of antisense Bmi-1 RNA on the proliferation of lung cancer cell line A549 / 中华病理学杂志

<p><b>OBJECTIVE</b>To study the effects of antisense Bmi-1 (B cell-specific moloney murine leukemia virus insertion site 1) RNA on the growth, cell cycle and apoptosis of lung cancer cell line A549.</p><p><b>METHODS</b>Recombinant plasmids carrying antisense Bmi-1 RNA were transfected into A549 cells, which expressed a high level of endogenous Bmi-1. The mRNA level of A549 cell was analyzed by real time quantitative RT-PCR and the protein level was determined using Western blot. MTT growth curve and plate colony forming assay were used to measure the effect of antisense Bmi-1 RNA expression on the growth of A549. Flow cytometry was used to analyze cell cycle and apoptosis.</p><p><b>RESULTS</b>Antisense Bmi-1 RNA reduced the Bmi-1 expression at the protein level, but did not alter the mRNA level in A549 cells. Compared with the control cells, A549 cells transfected with antisense Bmi-1 RNA showed a strong inhibition of the cell growth. The number of plate colony formation of the antisense Bmi-1 transfected cells (0.67 +/- 0.50) was less than those of the control (73.0 +/- 4.1) and cells transfected with empty vector (67.0 +/- 4.0, P < 0.01). Transfection of antisense Bmi-1 RNA arrested the A549 cells at G₀/G₁ phase of the cell cycle and did not increase the apoptosis.</p><p><b>CONCLUSION</b>Antisense Bmi-1 RNA expression inhibits A549 cells proliferation, likely through the interference of Bmi-1 leading to an arrest of the proliferating cells at the G₀/G₁ phase.</p>

Inhibition effect of antisense Bmi-1 on Jurkat cells / 中华血液学杂志

<p><b>OBJECTIVES</b>To investigate whether antisense Bmi-1 plasmid could inhibit the proliferation of Jurkat cells.</p><p><b>METHODS</b>The antisense plasmid was constructed by PCR amplification of a 171 bp segment spanning Bmi-1 start codon and zinc finger structure and the PCR product was subsequently inserted reversely to plasmid pLNCX2. The final construct was confirmed through restriction enzyme digestion. G418 was added into the medium after the plasmid was successfully introduced into Jurkat cells by using lipofectin-mediated DNA transfection. The proliferation of Jurkat cells were determined by MTT and colony formation assays. Cell cycle was determined by flow cytometry. The p16 expression of Jurkat cells was studied by immunofluorescent histochemistry.</p><p><b>RESULTS</b>The growth rate of antisense Bmi-1 transfected Jurkat cells was significantly lower than that of the controls, and the colony forming capacity of the transfected cells decreased significantly (P < 0.01), the colony numbers being (90.7 +/- 9.07)/10(3) cells, (83.3 +/- 6.11)/10(3) cells and (56.0 +/- 5.56)/10(3) cells for control cells, empty plasmid transfected Jurkat cells and antisense Bmi-1 transfected Jurkat cells, respectively. The percentage of G, phase cells was increased and the p16 expression of antisense Bmi-1 transfected cells was significantly upregulated than that of control cells.</p><p><b>CONCLUSION</b>Antisense Bmi-1 can inhibit the growth and upregulate the expression of p16 of Jurkat cells in vitro.</p>

Construction of antisense Bmi-1 expression plasmid and its inhibitory effect on K562 cells proliferation / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Bmi-1 gene determines the proliferative capacity of normal and leukemia stem cells. Expression of Bmi-1 has been found in all types of myeloid leukemia cells in both humans and mice. This study aimed at assessing the effect of antisense Bmi-1 expression on K562 cells proliferation and p16 protein (p16) expression.</p><p><b>METHODS</b>A transcriptional repressor, Bmi-1 cDNA was cloned by reverse transcriptase polymerase chain reaction (RT-PCR) of its mRNA from K562 cells. A plasmid expressing antisense Bmi-1 mRNA was then constructed by reverse design of PCR primers and cloned to the plasmid pLNCX2; G418 was added to the medium after the plasmid was successfully introduced in K562 cells by lipofectin-mediated DNA transfection. The effects of the antisense expression on the proliferation of K562 cells were analyzed by using microculture tetrazolium and colony forming. Cell cycle was analyzed by using flow cytometry. The p16 expression of K562 cells was observed by immunofluorescence histochemical stain.</p><p><b>RESULTS</b>K562 cells transfected with antisense Bmi-1 plasmid grew significantly slower than that of controls (the parental K562 and cells transfected with empty plasmid). The colony forming ability of antisense Bmi-1 plasmid transfected cells decreased significantly (P < 0.01) compared with controls. The p16 expression of cells transfected with antisense Bmi-1 was upgraded more apparently than that of controls.</p><p><b>CONCLUSION</b>The antisense Bmi-1 gene can inhibit the growth of K562 cell and upgrade expression of p16 in K562 cells.</p>

Construction of antisense telomerase hTERT and its effect on K562 cells / 中华血液学杂志

<p><b>OBJECTIVES</b>To investigate whether antisense human telomerase reverse transcriptase (hTERT) could inhibit the activity of telomerase and the proliferation of K562 cells.</p><p><b>METHODS</b>The antisense plasmid was constructed by reverse insertion of hTERT PCR product into plasmid pLNCX-neo. Then the constructed plasmid was introduced into K562 cells by liposomes-mediated DNA transfection. The inhibition effects of telomerase on the proliferation of K562 cells were analyzed by MTT and colony formation assay, the telomerase activity of K562 cells by TRAP-PCR ELISA methods.</p><p><b>RESULTS</b>The growth rate of antisense hTERT transfected K562 cells was significantly lower than those of the controls, and the colony formation capacity of the transfected cells decreased significantly (P < 0.01), the colony number is (100.33 +/- 7.57)/10(3) cells, (92.67 +/- 5.86)/10(3) cells and (50.33 +/- 6.11)/10(3) cells for control K562 cells, K562 neo cells and antisense hTERT transfected HL60 cells, respectively. The telomerase activity of antisense hTERT transfected K562 cells was significantly inhibited.</p><p><b>CONCLUSION</b>The expression of an antisense sequence to the mRNA sequence of telomerase protein subunit can inhibit the activity of telomerase, slow the cell growth and inhibit the capacity of colony formation of K562 cells.</p>