FoxM1 promotes development of AML by regulating Bcl-2 expression

AIM: To investigate the role of Forkhead box M1 (FoxM1) and B-cell leukemia/lymphoma-2 (Bcl-2) in the pathogenesis of acute myeloid leukemia (AML). METHODS: RT-qPCR and immunofluorescence analysis were used to determine the expression of FoxM1 at mRNA and protein levels in AML-de novo patients, AML-complete remission (CR) patients, AML-refractoriness and relapse (RR) patients and healthy controls. HL60 cells and K562 cells were transfected with FoxM1 siRNA. The cell proliferation was detected by cell proliferation assay and colony formation assay on soft agar, and the cell apoptosis was determined by flow cytometry. The expression of FoxM1 and Bcl-2 at mRNA and protein levels was detected by RT-qPCR and Western blotting. The activity of bcl-2 promoter was examined by luciferase reporter assay with FoxM1 targetting. RESULTS: FoxM1 expression level in the AML-de novo patients was significantly higher than that in the healthy controls. As compared with the AML-de novo patients, FoxM1 expression in the AML-CR patients was reduced, and the FoxM1 expression level was the highest in the AML-RR patients. FoxM1 expression was inhibited in the HL60 cells and K562 cells transfected with FoxM1 siRNA. Transfection with FoxM1 siRNA in the HL60 cells and K562 cells inhibited the proliferation as compared with NC siRNA transfection, and impaired the colony formation ability. On the contrary, transfection with FoxM1 siRNA promoted the cell apoptosis. FoxM1 regulated bcl-2 expression positively. CONCLUSION: FoxM1 promotes the development of AML by regulating bcl-2 expression. Silencing of FoxM1 expression suppresses cell proliferation and promotes cell apoptosis. FoxM1 is a potential target for AML treatment.     

Three kinds of antisense oligodeoxynucleotide enhance the sensitivity of leukemia cell K562 to cisplatin

AIM: To investigate whether antisense oligodeoxynucleotides of hTERT、bcl-2 and c-myc could enhance the sensitivity of leukemia cell K562 to cisplatin. METHODS: The inhibiting effects of cisplatin and cisplatin plus antisense oligodeoxynucleotide on K562 cells were determined by MTT. RESULTS: The inhibiting rate of 20 μmol/L cisplatin to K562 cell is 17.17%±1.36% and it becomes 25.41%±1.77%, 26.18%±1.43% and 28.29%±1.05%, respectively, as combinated with antisense oligodeoxynucleotide of hTERT, bcl-2 or c-myc. CONCLUSION: These results indicated that antisense oligodeoxynucleotides of hTERT, bcl-2 and c-myc enhanced efficacy of cisplatin in K562 leukemic cells.     

Inhibition of K562 cell growth by antisense drug targeting with VEGF mRNA in vitro

AIM: To investigate inhibition of K562 cell growth by antisense drug targeted VEGF mRNA. METHODS: X7, 20-mer antisense sequences were selected, synthesized and modified with phosphorothioate. The drug was transfected into K562 cells in the present of lipofection. Cell growth was assayed by trypan blue dye exclusion assay and MTT. The level of VEGF protein in the media was determined by ELISA. The morphology of apoptotic cells were observed by Giemsa staining, and the propotion of apoptotic cells was detected by flow cytometry. RESULTS: The antisense drug inhibited growth of K562 and downregulated expression of VEGF protein significantly, compared with Scrambed control group and showed dose-dependent relation. Signs of apoptosis of K562 cells were not observed. CONCLUSION: Inhibition of K562 cell proliferation, but not cells apoptosis induction is the mechanism of inhibing growth of K562 cells by antisense drug targeted VEGF mRNA. At same time, VEGF has function of promoting K562 cell proliferation, and VEGF mRNA may be a new target attached by drugs.     

Up-regulation of mRNA expressions of fas,bcl-2, bim,bax, caspase-3, caspase-9, and bcl2l12 in K562 treated with bortezomib

AIM: To detect the treatment of K562 leukemia cells with bortezomib altering the expression of genes fas, bcl-2, bcl2l12, bim, bax, caspase-9 and caspase-3.METHODS: MTT assay was used to detect the inhibition of proliferation. Apoptosis was detected by Annexin-V staining and mitochondrial transmembrane potential (Δψm). RT-PCR was used to analyze the mRNA expressions of fas, bcl-2, bcl2l12, bim, bax, caspase-3 and caspase-9.RESULTS: Bortezomib caused a time- and dose-dependent inhibition of cell proliferation and IC50 of 24 h and 48 h were 161.41 nmol/L and 96.33 nmol/L, respectively. At the concentration of 104 nmol/L, bortezomib induced apoptosis in a time-dependent manner, including increasing annexin-V positivity and decreasing the Δψm. RT-PCR showed that bortezomib up-regulated the mRNA expression of fas, bcl2l12, caspase-9 and caspase-3, but mRNA expressions of bcl-2, bim and bax did not changed obviously.CONCLUSION: Bortezomib inhibits the proliferation of K562 and induces apoptosis, in which fas, bcl2l12, caspase-9 or caspase-3 gene is one of the main genes taking part in.     

Combination of sorafenib and daunorubicin has antileukemic activity on K562 cells

AIM: To investigate the synergetic inhibitory effect of sorafenib and daunorubicin (DNR) on K562 and U937 cells. METHODS: The inhibitory rate of sorafenib or daunorubicin alone, and the combined inhibitory rate of sorafenib and IC10 daunorubicin were measured by MTT assay. Apoptotic rate of single drug or combination was assessed by flow cytometry (Annexin Ⅴ/PI staining) and Hoechst 33258 staining assay. p-ERK1/2 level was detected by Western blotting after the cells were treated with sorafenib, daunorubicin and U0126 or combinations. Synergistic or antagonistic effect of proliferation and apoptosis on K562 and U937 was estimated according to the Jins Method. RESULTS: Combination of sorafenib and DNR showed synergistic growth inhibition (q>1.15, P<0.01) and synergistic promotion of apoptosis (q>1.15, P<0.05) in K562 and U937 cells. The level of p-ERK1/2 in K562 cells was obviously higher than that in U937 cells (P<0.01). p-ERK1/2 expression was completely inhibited in sorafenib or U0126 treated K562 cells for 24 h. Combination of U0126 with DNR inhibited the proliferation of K562 cells synergistically. CONCLUSION: Combination of sorafenib with DNR showed synergistic cell growth inhibition and promotion of apoptosis in K562 and U937 cells. U937 cells were more sensitive to DNR than K562 cells while K562 cells were more sensitive to sorafenib. Sorafenib enhances the anti-leukemic activity of DNR in K562 and U937 cells via down-regulation of p-ERK1/2 expression.     

Effect of CLCN2 antisense oligonucleotide on U251 cells injury by cisplatin

AIM: To investigate the effect of chloride channel CLCN2 antisense oligonucleotide on the cell injury of malignant U251 glioma cells induced by cisplatin (DDP). METHODS: The experiment was divided into 4 groups: control group (nonsense oligonucleotide), CLCN2 antisense oligonucleotide group, DDP group (DDP＋nonsense oligonucleotide), DDP＋CLCN2 antisense oligonucleotide group. The viability of U251 cells was measured by MTT assay, CLCN2 mRNA level was determined by RT-PCR, cell apoptosis was measured by TUNEL assay. RESULTS: Compared to the control group, the cell viability, CLCN2 and cyclinD1 mRNA decreased in CLCN2 antisense oligonucleotide group, DDP treated group and CLCN2 antisense oligonucleotide with DDP treated group, cells apoptosis increased. Compared to DDP group, the cell viability (P<0.05) and CLCN2 mRNA decreased in CLCN2 antisense oligonucleotide with DDP treated group, and cells apoptosis increased (P<0.01). Compared to CLCN2 antisense oligonucleotide group, CLCN2 mRNA significantly decreased (P<0.01) in CLCN2 antisense oligonucleotide with DDP treated group. CONCLUSION: CLCN2 antisense oligonucleotide inhibits the expression of CLCN2 mRNA in U251 cells. Inhibition of CLCN2 mRNA facilitates the cell injury of U251 cells induced by DDP. The decrease in CLCN2 mRNA is involved in the mechanism of cell injury by DDP.     

Effect of antisense locked nucleic acid blocking translation initiation region of c-myc exon 2 on apoptosis of hepatocellular carcinoma cells

AIM: To observe the effect of antisense locked nucleic acid (anti-LNA) blocking the translation initiation region of c-myc exon 2 on the viability and apoptosis of hepatocellular carcinoma cells.METHODS: The anti-LNA that was complementary to the translation initiation region of c-myc exon 2 was designed, synthesized, and introduced into the HepG2 cells by cationic liposome-mediated transfection. The mRNA and protein levels of c-Myc in the cells were determined by RT-PCR and Western blot. The change of cell apoptosis was analyzed by flow cytometry, and the toxicity of anti-LNA to the cells was detected by MTT assay.RESULTS: Five days after transfection, the mRNA level of c-Myc in anti-LNA group was 0.335±0.016, and the protein level was 0.448±0.037, significantly lower than those in control group (both P<0.05). The ratio of apoptotic cells in anti-LNA group was 32%±6%, which was higher than that in control group (P<0.05).CONCLUSION: Antisense locked nucleic acid targeting at the translation initiation region of c-myc exon 2 shows strong inhibitory effects on the apoptosis of hepatocellular carcinoma cells.     

Apoptosis induced by berbamine in K562 cells correlates with the expression levels of bcr/abl gene and P210

AIM: To explore the effect of berbamine(BER) on apoptosis in K562 cells and its possible molecular mechanisms. METHODS: The apoptosis rate was measured by flow cytometry while electron microscopy and DNA electrophoresis were used to evaluate the characteristic changes of apoptosis, RT-PCR and Western blot were used to examine the expression levels of apoptosis related gene bcr/abl and BCR/ABL protein. RESULTS: By FCM, the apoptosis rate of K562 cells treated with 8.0 mg/L BER for 24 h and 72 h increased from (29.20±3.82)% to (61.77±4.35)% (P＜0.01); The typical apoptosis morphologic changes and the DNA ladder were more clearly observed. After treated with BER 0 to 16.0 mg/L for 24 h, the expression levels of bcr/abl mRNA and P210 (semiquantity value) decreased quickly from 1.19±0.02 to 0.73±0.02 (P＜0.01) and from 1.04±0.02 to 0.63±0.01 (P＜0.01), respectively. CONCLUSION: BER induces apoptosis of K562 cells in a time-and-concentration-dependent manner, the decline of bcr/abl mRNA and P210 may play an important role in the apoptotic effect of BER in K562 cells. BER could be used as a new clinical trials for bcr-abl⁺ diseases such as CML.     

Antisense drug targeting with VEGF mRNA designed by computer aid and inhibitory effects on K562 cell line in vitro

AIM:The effective antisense sequences targeted VEGF mRNA with computer software would be screened and designed, and effect of them on growth K562 cells and protein expression of VEGF were studied with experiments.METHODS:Seven antisense sequences were selected and synthesized, which consisted of 18-20 deoxynucleotide acid and were modified with phosphorothioate, according to principle of low free energy of overall △G₃₇ Overall. Cell growth was assayed by trypan blue dye exclusion assay and level of VEGF protien in the media was determined by ELISA.RESULTS:Six of seven sequences were capable of inhibing growth of K562 cells and downregulating the VEGF protein expression significantly, compared with Scrambed control group. It was found that there was a close correlation between low level of overall △G₃₇ and antisense effectiveness (r=0.887,P<0.01).CONCLUSION:VEGF mRNA antisense oliogdeoxynucleotides, which were designed by computer software of RNAstructure, were able to inhibit growth of K562 and its protein expression. The VEGF mRNA may be new target attached by drugs. At same time, the computer aided design is useful methods to obtain the effective antisense.     

Targeted inhibition of microRNA-21 with antisense oligonucleotide and their effects on human leukemic K562 cells

AIM: To explore the inhibitory effect of anti-miRNA-21 oligonucleotide (AMO-miRNA-21) on human leukemic K562 cells. METHODS: K562 cells were transfected with AMO-miRNA-21, which was complementary to the miRNA-21 in a sequence-specific manner. Viability of K562 cells was measured by MTT assay and the optimal concentration for transfection was determined. The inhibitory effect of AMO on the K562 cell growth was examined by trypan blue dye exclusion assay at 24 h, 48 h and 72 h after transfection. Giemsas staining was used to detect morphologic changes of the transfected cells. The cell apoptosis and cell cycle progression were assayed by flow cytometry. Expression of microRNA-21 in the cells was measured by real-time PCR. RESULTS: The growth of cells treated with AMO-miRNA-21 was obviously inhibited compared with that in control groups (P<0.05). Very low cytotoxic and high inhibitory effects of AMO-miRNA-21 were found at concentration of 0.6 μmol/L. The inhibitory effect lasted for 72 h. Apoptotic cells were increased in AMO group and typical morphologic changes were conformed by Giemsas staining. One visible hypodiploid peak was detected in the histogram. However, the cell cycle progression was not inhibited evidently. The expression of microRNA-21 in the transfected cells was down-regulated significantly. CONCLUSION: Targeted inhibition of microRNA-21 with antisense oligonucleotide effectively suppresses leukemic K562 cells growth by inducing apoptosis. miRNA-21 might be a potential target for leukemia therapy.     

Role of plk1 in the anti-cancer effect of colcemid and vincristine against K562 cells

AIM: To study the role of plk1 in the anti-cancer effect of colcemid and vincristine against K562 cells. METHODS: K562 cells were treated with colcemid and vincristine and antisense oligonucleotide of plk1, then expression of plk1 and γ-tubulin were investigated by Western blotting and confocal microscopy. RESULTS: Treatment of K562 cells with colcemid and vincristine influenced the condensation of plk1 and assembly of γ-tubulin, though without change of protein quantity. Treatment with antisense oligonucleotide of plk1 not only reduced the expression of plk1 without influence on protein quantity of γ-tubulin detected by Western blotting, but also disturbed the formation of centrosome observed by confocal microscopy. CONCLUSION: The function of colcemid and vincristine destructing the spindle might be realized through the mechanism of restraining condensation of plk1 and assembly of γ-tubulin, which might be dependent on plk1. plk1 may be a potential target in anti-cancer therapy.     

Effect of hTERT antisense oligodeoxynucleotide on Cis-diamminedichicloroplatinum-induced apoptosis in Jurkat cells

AIM:To explore the effect of hTERT antisense phosphorothioate oligodeoxynucleotide (ASODN) on apoptosis induced by chemotherapeutic drugs in Jurkat cell lines. METHODS:Cell viability was determined using the trypan blue dye exclusion assay. Apoptosis was detected by morphological observation, DNA gel electrophoresis and flow cytometry analysis. RESULTS:The survival rates of Jurkat cells cultured with daunorubicin, vincristin, and etoposide, respectively were similar with that cultured with those chemotherapic drugs plus hTERT ASODN. The survival rates of Jurkat cells cultured with cis-diamminedichicloroplatinum(DDP) added 24 hours later were higher than that cultured with hTERT ASODN and DDP added 24 hours later. The survival rates of Jurkat cells cultured with DDP were similar with that cultured with hTERT SODN and DDP. In morphological observation of apoptotic cells using Giemsa staining, cells displayed classic apoptotic changes treated with DDP or DDP combined with hTERT ASODN or SODN at 48 hours. Agarose gel electrophoresis of genomic DNA from Jurkat cells treated with ASODN and DDP combination for 48 hours showed typical DNA "ladder". Neither the DNA from Jurkat cells treated with SODN plus DDP nor the DNA from the cells treated with DDP alone showed ladder pattern. Apoptosis rates of Jurkat cells treated with DDP for 48 hours after 24 hours of exposure to ASODN significantly increased. There was significant difference in the percentage of apoptotic Jurkat cells between hTERT ASODN plus DDP and SODN plus DDP or DDP alone, respectively. CONCLUSION:The hTERT ASODN complementary to the translation initiation region of hTERT mRNA enhanced DDP-induced apoptosis in Jurkat cells.     

Glucosylceramide synthase upregulates apoptosis-related gene bcl-2 expression via MEK/ERK signaling pathway in leukemia multidrug-resis-tant cell line

AIM: To investigate whether glucosylceramide synthase (GCS) regulates apoptosis-related gene bcl-2 expression via MEK/ERK signaling pathway, thus enhancing drug resistance of K562/A02 human leukemia multidrug resistant cell line. METHODS: siRNA targeting GCS was transfected into K562/A02 cells. Bcl-2, p-ERK and total ERK expression at mRNA and protein levels after GCS knockdown were detected by real-time PCR and Western blotting. After exposed to MEK-ERK pathway inhibitor U0126, the expression of Bcl-2 at mRNA and protein levels also was analyzed by real-time PCR and Western blotting, respectively. The viability of the cells was evaluated by CCK-8 assay. RESULTS: The expression of GCS and Bcl-2, as well as MEK/ERK signaling were significantly inhibited in K562/A02 cells by GCS siRNA transfection compared with negative control group. Inactivation of MEK/ERK signaling due to U0126 treatment decreased Bcl-2 mRNA and protein levels in a concentration-dependent manner, and sensitized K562/A02 cells to adriamycin. CONCLUSION: GCS may affect the expression of apoptosis-related gene bcl-2 by MEK/ERK signaling pathway, thus regulating multidrug resistance of human leukemia K562/A02 cells.     

Cytochrome C induces apoptosis in HL-60 cells through inhibiting bcl-2,bcl-xl mRNA expression

AIM:To study the effect of cytochrome C on HL-60 cells in vitro and the expression of relevant apoptotic genes.METHODS:HL-60 cells were treated with different concentrations of cytochrome C for 24 h.The suppressing rate was assayed by MTT.The morphology of cell was observed by microscope and fluorescence microscope.The apoptosis was assayed by flow cytometry (FCM) and DNA electrophoresis.The expression changes of bcl-2 and bcl-xl mRNA was examined by RT-PCR.RESULTS:The suppressing rate increased with the increase in the cytochrome C concentrations.When treated with 0-37.5 mg/L cytochrome C for 24 h,the percentage of apoptotic HL-60 cells increased in a dose-dependent manner,and the typical cells and the appearance of apoptotic DNA ladder were observed.At the same time,within this range of concentration,the expression of bcl-2 and bcl-xl mRNA decreased gradually.When treated with cytochrome C at concentration higher than 37.5 mg/L,the percentage of apoptotic HL-60 cells did not increase,but decreased,while the cell necrosis was observed.CONCLUSIONS:It suggested from the results that at certain range of concentration,cytochrome C induces apoptosis or necrosis in HL-60 cells.The percentage of apoptosis,the changes of expression of bcl-2 and bcl-xl depend on the dose of cytochrome C.The mechanism that cytochrome C induces apoptosis in HL-60 cells may be related to suppressing the expression of bcl-2 and bcl-xl.     

Stat5b signaling pathway regulates the expression of Survivin and promotes apoptosis in human colon cancer cells

AIM: The purpose of the study was to examine colon cancer cell lines to determine whether Stat5b/Survivin plays an important role in the process of apoptosis in colon cancer cells. METHODS: Protein lysates were extracted from colon cancer cells. Human colon cancer cell line HT29 was transfected with Stat5b antisense oligonucleotide mediated by liposome. MTT assay was used to measure the proliferation. Flow cytometry was applied to analyze the cell cycle and apoptosis. EMSA was used to detect the activity of Stat5. Western blotting was applied to measure the expression of Stat5, p-Stat5, cyclin D1, Survivin, Bcl-2 and Bcl-x L. RESULTS: Targeting of Stat5 using antisense oligonucleotide against the translation site resulted in apoptosis and downregulaed the expressions of Stat5, p-Stat5, cyclin D1 and Survivin, but not Bcl-2 and Bcl-xL. CONCLUSION: Constitutive activation of Stat5 is associated with the carcinogenesis of colon cancer cells. Blocking of Stat5 signaling inhibits the expression of Survivin and induces apoptosis in colon cancer cells.     

Effect of decitabine on resistance of K562/A02 cells to adriamycin

AIM: To investigate the effect of decitabine (DAC) on the resistance of human chronic myeloid leukemia cell line K562/A02 to adriamycin (ADR), and to explore the possible mechanism. METHODS: The K562/A02 cell line and its parental cell line K562 were treated with different concentrations of ADR or DAC alone, or in combination. The cytotoxic effects of these 2 agents were determined by CCK-8 assay. The degree of DNA methylation was evaluated by Sequenom MassARRAY system and colorimetric method. The cell cycle distribution and the apoptotic rate were determined by flow cytometry. RESULTS: K562/A02 cells were more significantly resistant to ADR than K562 cells.The half maximal inhibitory concentration of ADR for 24 h of the K562/A02 cells was about 50 times higher than that of the K562 cells. To DAC, in the concentration range of 0.5~8 μmol/L, K562/A02 cells were more sensitive than K562 cells. As compared with the same concentrations (4.31 μmol/L and 17.24 μmol/L) of ADR alone, the combination with 1 μmol/L DAC significantly improved the sensitivity of K562/A02 cells to ADR. Both DAC and ADR affected the cell cycle progression and apoptotic rate of K562/A02 cells. DAC (1 μmol/L) treatment mainly showed S phase arrest and increased early apoptotic rate for 24 h, and G₂/M phase arrest and increased late apoptosis and necrosis for 48 h in a time-related manner. ADR treatment showed G₂/M phase arrest and increased late apoptosis and necrosis in a concentration-dependent manner. In combination with 1 μmol/L DAC, the effect of ADR on the cell cycle distribution was further enhanced, showing more obvious G₂/M phase arrest, but no significant difference of the apoptotic rate was observed. The degree of methylation in the genome had no significant difference between the 2 cells, and it before and after DAC treatment had no significant change. CONCLUSION: DAC enhances the sensitivity of K562/A02 cells to ADR, showing drug resistance-reversing potential. The mechanism may be related to regulating cell cycle progression and promoting apoptosis and necrosis of K562/A02 cells.     

Lentivirus-mediated RNA interference targeting vascular endothelial growth factor gene enhances the sensitivity of K562 cells to STI571

AIM: To investigate the effects of RNA interference (RNAi) inhibiting the expression of vascular endothelial growth factor (VEGF) gene mediated by lentiviral vector on the proliferation and apoptosis of K562 leukemic cell line. METHODS: A lentiviral vector containing short hairpin RNA (shRNA) targeting VEGF was constructed and cotransfected with the packaging plasmids mixture into 293T cells by Lipofectamine 2000. K562 cells were infected with the packaged lentivirus. The levels of VEGF mRNA and protein were detected by real-time quantitative RT- PCR, Western blotting and ELISA. Cellular proliferation was determined by trypan blue dye exclusion and MTT assay. STI571 (imatinib mesylate)-induced apoptosis was analyzed by flow cytometry. RESULTS: The lentiviral shRNA vector targeting VEGF was successfully constructed and transfected into K562 cells. The expressions of VEGF mRNA and protein in K562-shVEGF cells transfected with pRNAT-shRNA were significantly inhibited when compared with those of K562 and K562-con cells (mock transduction). The proliferation rate of K562-shVEGF cells slowed down. After STI571 treatment, the percentages of apoptotic cells in K562-shVEGF cells increased more significantly than those of K562 and K562-con cells (P<0.05). CONCLUSION: Inhibition of VEGF by lentivirus-mediated RNAi effectively inhibits proliferation and increases the sensitivity of K562 cells to STI571.     

Inhibitory effect of propolis on proliferation of K562 cells in vitro

AIM: To study the effect of propolis on the proliferation of K562 cells.METHODS: K562 cells were cultured in vitro. Cell proliferation was measured by MTT method. The apoptotic rate was determined by flow cytometry. RT-PCR was applied to detect mRNA expression of Nup98. The protein level of Nup98 was determined by Western blotting. RESULTS: The inhibitory rates of proliferation induced by propolis at the concentrations of 2 mg/L, 20 mg/L and 200 mg/L were obviously higher than that in control cells in a time-and dose-dependent manner. The apoptotic rate was increased in a dose-dependent manner. High concentration of propolis down-regulated the expression of Nup98 at mRNA and protein levels. CONCLUSION: Propolis inhibits the proliferation and induces apoptosis in K562 cells. The mechanism may be related with down-regulation of Nup98.     

Study of establishment of K562/HHT cell line and reversal of multidrug resistance by antiprogestin drug mifepristone

AIM: To study the mechanism of multidrug resistance (MDR) of leukemia cells induced by homoharringtonine (HHT) and the reversal effect of mifepristone on MDR.METHODS: Human leukemia cell line K562 was induced into MDR cell line by intermittent administration of high dose of HHT.MTT assay was used to detect the sensitivity of these MDR cells to all sorts of chemotherapeutic agents with or without mifepristone.The cytotoxicity of mifepristone was also observed.RT-PCR was used to detect the expression of MDR1 gene and glucosylceramide synthase (GCS) gene.Flow cytometry was used to detect the expression of P-glucoprotein and the accumulative value of intracellular daunorubicin (DNR) in these MDR cells with or without mifepristone.Immunohistochemistry was used to detect the expression of Bcl-2,Bax and caspase-3 in these MDR cells with or without mifepristone.RESULTS: MDR cell line K562/HHT was acquired after induced by HHT for 2 months.This MDR cell line possessed the ability of 462.6 fold resistance to HHT and cross-resistance to adriamycin,vincristine and etoposide.The expression of MDR1 gene,GCS gene,P-glucoprotein and Bcl-2/Bax ratio in K562/HHT cells were significantly higher than those in K562 cells (P<0.05).The caspase-3 expression and the accumulative value of intracellular DNR in K562/HHT cells were significantly lower than those in K562 cells (P<0.05).10 μmol/L mifepristone reversed the resistance of K562/HHT cells to HHT,adriamycin,vincristine and etoposide at different levels.The Bcl-2/Bax ratio,caspase-3 expression and accumulative value of intracellular DNR in K562/HHT cells treated with RU486 were significantly different compared with K562/HHT cells without RU486 treatment (P<0.05).CONCLUSIONS: Leukemia cell line K562 can be induced into MDR cell line K562/HHT by HHT.P-glucoprotein,GCS,Bcl-2/Bax ratio and caspase-3 may play an important role in K562/HHT cells.Mifepristone can reverse MDR in K562/HHT cells by decreasing the accumulative value of intracellular drug and regulating the expression of Bcl-2,Bax and caspase-3.