Effects of 5-bromotetrandrine and daunorubicin on apoptosis and expression of survivin in K562/A02 cells / 中国实验血液学杂志

The aim of this study was to investigate the potential benefit of combination therapy with 5-bromotetrandrine (5-BrTet) and daunorubicin (DNR) on chronic leukemia. The apoptosis of K562/A02 cells treated by DNA, BrTet and BrTet combined with DNR for 48 hours was detected by flow cytometry; the expressions levels of survivin mRNA and protein K562/A02 cells treated by DNR, BrTet and BrTet combined with DNR and in untreated K562 cells for 48 hours were measured by RT-PCR and Western blot respectively. The results showed that the combination of BrTet with DNR increased apoptotic rate of K562/A02, down-regulated the expression levels of survivin mRNA and protein in K562/A02 cells as compared with blank control and cells treated by BrTet or DNR alone, the survivin expression in K562/A02 cells was higher than that in K562 cells. It is concluded that the combination of BrTet with DNR can effectively reverse the multidrug resistance of K562/A02 cells, promote the apoptosis of K562/A02 cells, the mechanism of which may be related with down-regulation of survivin expression. Survivin may be a target for the treatment of MDR in hematopoietic malignancies.

VEGF shRNA enhances the sensitivity of multidrug-resistant leukemia cells to anticancer agent / 中国实验血液学杂志

This study was aimed to explore the effect of vascular endothelial growth factor (VEGF) on sensitivity of leukemia cell line K562/A02 to doxorubicin by using RNA interference, and to investigate its mechanism. The 3 shRNA targeting human vegf gene were synthesized, then transfected into K562/A02 cells by lipofectamine 2000 reagent. RT-PCR was used to detect the expression of vegf and mrp1 at the mRNA level;Western blot was used to analyze the expression of VEGF, MRP1, AKT, P-AKT at the protein level; MTT was used to determine the IC(50) value of transfected cells to doxorubicin (DOX); flow cytometry was used to detect cell apoptosis and intracellular Rho123 retention. The results showed that after vegf shRNA were transfected into K562/A02 cells, the expression of vegf at the mRNA level decreased, and the difference between vegf shRNA2 group or vegf shRNA3 group and HK group was statistically significant (p < 0.05), the greatest decrease was observed in the cells transfected with vegf shRNA3; and the protein level of VEGF was also down-regulated. The IC(50) value of positively transfected group was lower than that of control groups, and the difference between vegf shRNA2 group or vegf shRNA3 group and HK group was significant (p < 0.05). The retention of intracellular Rho123 was enhanced in three positively transfected groups (p < 0.05). Cell apoptosis increased in positively transfected groups, and there was statistically difference between vegf shRNA2 group or vegf shRNA3 group and HK group (p < 0.05). The expression of mrp1 at the mRNA level were decreased, and there were statistical difference between vegf shRNA3 group and HK group (p < 0.05), and the protein level of mrp1 was also down-regulated; the expression of P-AKT at protein level decreased in positively transfected groups, and the greatest decrease was seen in vegf shRNA3 group. It is concluded that the transfection with exogenous vegf shRNA can inhibit the expression of vegf at both mRNA and protein levels, and enhance the sensitivity of K562/A02 cell to doxorubicin, the mechanism of which may be the inhibition of apoptosis and down-regulation of MRP1 by inactivating PI3K/AKT signaling pathway.

Effect of desferrioxamine on K562/A02 cell line and its mechanism / 中国实验血液学杂志

Iron is an essential element for cell growing including tumor cells. This study was purposed to explore the effect of desferrioxamine (DFO) on cell line K562/A02 and its mechanism. K562/A02 cells were cultured with different concentrations of DFO. The inhibitory effects of adriamycin (ADM) used alone or combined with DFO on the proliferation of K562/A02 was evaluated by MTT assay. The apoptosis rate of K562/A02 cells after treatment with 0, 12.5, 25 and 50 µmol/L DFO alone or in combination with 1 mg/L ADM were analyzed by flow cytometry. ADM accumulation in K562/A02 cells after treatment with different concentrations of 0, 12.5, 25 and 50 µmol/L DFO were also analyzed by flow cytometry. The levels of BAX/BCL-2 and MDR1 mRNA were determined by RT-PCR, and then the protein level of P-glycoprotein (P-gp) was detected by Western blot. The results showed that the IC(50) of ADM for K562 and K562/A02 cells were (1.46 ± 0.07) mg/L and (40.98 ± 3.05) mg/L respectively. The resistance of K562/A02 cells to ADM was 28.06 times as that of K562 cells. After treatment of K562/A02 cell with DFO of 12.5, 25 and 50 µmol/L for 48 hours, the resistance of K562/A02 cells to ADM were increased by 24.95, 16.11 and 9.99 times respectively. When K562/A02 cells were incubated with different concentrations of DFO of 12.5, 25, 50 µmol/L for 48 hours, the apoptosis rat were (3.50 ± 0.30)%, (7.27 ± 0.32)% and (12.53 ± 1.21)% respectively. After co-culture with DFO and ADM for 48 hours, apoptosis rate were (6.13 ± 0.29)%, (9.57 ± 0.40)% and (18.97 ± 1.10)% respectively. The above apoptosis rates was much higher than that of control group (p < 0.05) and they were dose-dependent. In comparison between DFO + ADM group and DFO group, there was no significant difference (p > 0.05). Expression rate of BAX/BCL-2 increased. The levels of MDR1 mRNA reduced. Furthermore, expression of P-gp also decreased in K562/A02 cells. It is concluded that iron increase can promote K562/A02 cells growth and inhibit their apoptosis. Otherwise, iron-deprivation can induce K562/A02 cells apoptosis. DFO disturbs the iron metabolism and inhibits DNA synthesis of K562/A02 cells. This action of DFO may enhance the susceptibility of K562/A02 cells to apoptosis induced by chemotherapeutic drugs. The iron-deprivation may play a role in the treatment of leukemia with combination of DFO with other anticancer agents.

Influence of YB-1 protein on the biological behaviour in K562/A02 cells / 中国实验血液学杂志

The aim of this study was to investigate whether the growth, apoptosis and sensitivity to anticancer agent could be altered after introduction of YB-1 shRNA eukaryotic expression vector into the K562/A02 cells, and its possible molecular mechanisms. The recombinant eukaryotic expression plasmids including YB-1 shRNA and the vector-random-sequence were introduced into K562/A02 cells by lipofectamine mediation, and the positive clones were screened by G418. RT-PCR and Western blot were employed to detect the expression of mRNA and protein of YB-1 in leukemia cells, respectively. The proliferative ability of the cells was determined by MTT assay and cell cycle analysis. Apoptosis of K562/A02 cells was assayed by AnnexinV-FITC/PI double labeled flow cytometry. The drug sensitivity to anticancer agent was determined by MTT assay. The expressions of MDR1 gene and P-gp were detected by RT-PCR and flow cytometry respectively. The results indicated that the levels of mRNA and protein of YB-1 decreased dramatically in three groups of positively transfected cells when compared with control cells. The inhibitory rates of 3 different shRNA sequences targeting YB-1 gene were (65.1 ± 2.1)%, (27.4 ± 1.3)% and (67.4 ± 1.6)% respectively. The introduction of exogenous YB-1 shRNA gene into K562/A02 cells resulted in decreased levels of the proliferative ability in K562/A02 cells, and displayed higher at G(1), lower at G(2) and S phase in cell cycle distribution in comparison with the control groups. AnnexinV/PI detection indicated higher AnnexinV(+) ratio in 3 groups of positively transfected cells after being treated with As(2)O(3) of 0.5 µmol/L for 24 hours. The IC(50) values of doxorubicin in 3 groups of positively transfected cells were significantly lower than that in control group. The level of MDR1 gene and P-gp decreased significantly in 3 groups of positively transfected cells. It is concluded that the transfection with YB-1 shRNA gene can inhibit the proliferation of leukemia cells and induce cell apoptosis. The expression of MDR1 mRNA and P-gp decrease after transfection of YB-1 shRNA into K562/A02 cells.

Effect of regulation of Y-box protein 1 by RNA interference on the doxorubicin induced mdr1 gene expression in K562 cells / 中华血液学杂志

<p><b>OBJECTIVE</b>To investigate the effect of YB-1 on the transcription of induced mdr1 gene expression in K562 cells.</p><p><b>METHODS</b>K562 cells were treated with doxorubicin (DOX) at different concentrations and times. Expression of mdr1 and YB-1 genes was examined by RT-PCR and P-glycoprotein (P-gp) by flow cytometry. Cyto/nuclear protein was extracted for YB-1 detection by Western blotting. The expression of YB-1 gene in K562 cells was inhibited by YB-1 gene specific RNA interference (RNAi), then the expression of mdr1 and P-gp in YB-1 gene silenced cells treated with DOX was detected.</p><p><b>RESULTS</b>The mdr1 gene as well as its corresponding protein P-gp was highly expressed in DOX exposed K562 cells. DOX up-regulated the expression of YB-1 gene, and promoted YB-1 protein nuclear translocation. On YB-1 gene silenced, the expressions of mdr1 gene and P-gp were obviously down-regulated in DOX treated K562 cells.</p><p><b>CONCLUSION</b>Doxorubicin can induce the expression of mdr1 gene in K562 cells, which may result from the transcription of mdr1 gene by activated YB-1.</p>

Effect of YB-1 gene knockdown on human leukemia cell line K562/A02 / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To investigate the potential effects of YB-1 gene knockdown on gene expression profile, cell growth and apoptosis in leukemia cell line K562/A02.</p><p><b>METHODS</b>The recombinant eukaryotic expression plasmid containing YB-1 short hairpin RNA (shRNA) or random-sequence (HK) were transfected into K562/A02 cells by lipofectamine mediation. cDNA microarray was performed to explore the alteration of gene expression profile when YB-1 gene expression was decreased. Expression of CARD8 and RHOC genes were verified by semi-quantitative reverse transcription-PCR (RT-PCR). The proliferative ability of the cells was determined by methyl thiazolyltetrazolium (MTT) assay and cell cycle analysis. Cell apoptosis was assayed by Annexin V-FITC/PI double labeled flow cytometry.</p><p><b>RESULTS</b>The levels of YB-1 mRNA and protein decreased dramatically in three positively transfected cells when compared with untransfected K562/A02 cells or K562/A02-HK thansfected cells. Gene expression profile was altered by transfection of YB-1 shRNA into K562/A02 cells. Among 47,000 genes on the microarray, 252 genes were detected to have changes, with 143 down-regulated and 109 up-regulated. They were functionally related to cell cycle progression, gene replication, metabolism, cell apoptosis, cell signal transduction, etc. An increase in CARD8 gene expression and a decrease in RHOC gene expression have been confirmed by RT-PCR in K562/A02-YBX13 cells. The introduction of exogenous YB-1 shRNA gene into K562/A02 cells resulted in decreased proliferation, higher G1, lower G2 and S ratio in cell cycle distribution in comparison with the control groups. Annexin V/PI detection indicated higher Annexin V+ ratio in the three positively transfected cells 24 hours after cells were treated with 0.5 micromol/L of As2O3.</p><p><b>CONCLUSION</b>Down-regulation of YB-1 gene by shRNA-YB-1 can alter the gene expression profile in K562/A02 cells, leading to change of cell proliferation and apoptosis.</p>

Inhibition effect of short hairpin RNA on VEGF receptor flt-1 gene expression in leukemia cell line K562 / 中国实验血液学杂志

This study was purposed to investigate the inhibitory effect of short hairpin RNA (shRNA) on expression of vascular endothelial growth factor (VEGF) receptor flt-1 gene in leukemia cells line K562, and to explore the influence of shRNA invasive ability on leukemia cells and its mechanism. The recombinant eukaryotic expression plasmid containing flt-1 shRNA gene was transfected into K562 cells by lipofectamine mediation and positive clones were screened by G418. shRNA gene in K562 cells was confirmed by PCR. RT-PCR and Western blot were employed to detect the expression of flt-1 mRNA and protein in leukemia cells. The invasive ability of K562 cells was studied by Boyden chamber invasion assay before and after flt-1 shRNA transfection. MMP-2 and MMP-9 mRNA expressions were detected by RT-PCR after transfection of the recombinant plasmid C1/U6/FltS2 into K562 cells through liposome. The results showed that the recombinant eukaryotic expression plasmid had been transfected into the human leukemia cell line K562 and positive clones had been screened by G418 for 2 weeks. PCR detection revealed the stable expression of the shRNA gene in K562 cells. Flt-1 gene and protein expressions were inhibited by plasmid-expressed shRNA after transfection of recombinant vetors C1/U6/FltS into K562 cells. The inhibitory efficiency of two different shRNA sequences targeting Flt-1 gene were 46.1% and 65.4% respectively. The expression of MMP-2 and MMP-9 mRNA decreased, and the mean invasion rate in C1/U6/fltS2-transfected K562 cells was lower than that in nontransfected cells. It is concluded that shRNA eukaryotic expression vector specific to VEGF receptor flt-1 gene can high efficiently be transfected into leukemia cell line K562, effectively inhibits the expression of flt-1 gene, weakens the in vitro invasive ability of leukemia cells and the expression levels of MMP-2 and MMP-9 mRNA, which suggests that the VEGF involves in the migration of leukemia cells by regulating the MMP-2 and MMP-9 through joints with the receptor.

Effect of tetrandrine in combination with droloxifen on the expression of NF-kappaB protein in K562 and K562/A02 cell lines / 中华血液学杂志

<p><b>OBJECTIVE</b>To study the effect of tetrandrine (Tet) in combination with droloxifen (DRL) on the expression of nuclear factor kappa B (NF-kappaB) in K562 and K562/A02 cell lines and its reversal mechanism.</p><p><b>METHODS</b>The activation of NF-kappaB in K562 and K562/A02 cell lines and the effect of Tet or DRL alone or in combination on NF-kappaB protein expression were determined with immunocytochemistry and Western blotting respectively.</p><p><b>RESULTS</b>(1) K562/A02 cells displayed higher level of NF-kappaB protein expression than K562 cells. (2) The application of Tet or DRL alone or in combination had no effect on NF-kappaB expression in K562 cells at 6 h and 12 h (P > 0.05). (3) Tet and DRL alone or in combination could significantly down-regulate NF-kappaB protein expression in nuclei of K562/A02 cells. The effect was more significant in combination than either alone. This effect was more significant at 12 h than at 6 h.</p><p><b>CONCLUSIONS</b>(1) Activation of NF-kappaB may be involved in the mechanism of MDR of K562/A02 cell line. (2)Inhibition of NF-kappaB activation may be involved in the reversal of multidrug resistance in K562/A02 cells by Tet and DRL.</p>

Influence of tetrandrine on SORCIN gene expression in K562/A02 cell line / 中国实验血液学杂志

This study was aimed to explore the changes of soluble resistance-related calcium binding protein (sorcin) expression in reversion of multidrug resistance of K562/A02 leukemic cell line with different concentrations of tetrandrine (Tet), so as to provide a new theoretic evidence for clinical application of Tet. The inhibition of K562/A02 cell line by daunorubicin (DNR) was assayed by MTT method. The changes of SORCIN gene expression were assayed by RT-PCR. The changes of SORCIN protein expressed were assayed by Western blot. The results showed that Tet could enhance the cytotoxicity of DNR to K562/A02 cells (the IC(50) of DNR + Tet was 11.3+/-0.17 mg/L, 5.15+/-0.10 mg/L, 3.91+/-0.06 mg/L, and 2.52+/-0.04 mg/L, when concentrations of Tet were 0 mg/L, 0.5 mg/L, 1.0 mg/L, and 2.0 mg/L respectively). The gene encoding sorcin was highly expressed in K562/A02 cells, the expression of which was firstly enhanced in Tet concentration 0.5 mg/L, then attenuated in Tet concentration of 1.0, 2.0 mg/L (p<0.05). Sorcin protein expressed lowly in K562 cells and highly in K562/A02 cells, but the expression of SORCIN protein in K562/A02 cells was enhanced in Tet concentration of 0.5 mg/L, then was attenuated in Tet concentration of 1.0, 2.0 mg/L (p<0.05). It is concluded that the effect of Tet on reversal of K562/A02 drug-resistance shows concentration dependence by MTT assay. Tet reverses multidrug-resistance of K562/A02 cells through regulation of expression of SORCIN gene and protein, but not fully correlates to the reversing effect.

Experimental study on the role of VEGF autocrine loop in K562 leukemia cells / 中华血液学杂志

<p><b>OBJECTIVE</b>lo investigate the effects of anti-VEGF antibody and anti-VEGF hairpin ribozyme gene on the proliferation, apoptosis and related gene expression of the leukemia K562 cells and the possible molecular mechanisms.</p><p><b>METHODS</b>K562 cells were cultured in different concentrations of anti-VEGF antibody. The recombinant eukaryotic expression plasmid (pcDNA3-RZ) containing anti-VEGF hairpin ribozyme gene and the vector-alone were introduced into K562 cells by lipofectamine mediation. Cell proliferative capacity was determined by MTT, colony formation assay and cells cycles analysis. Cell apoptosis was assayed by DNA ladder and Annexin V -FITC/PI flow cytometry.</p><p><b>RESULTS</b>The anti-VEGF antibody was able to inhibit growth and induce apoptosis of K562 cells in a dose-dependent manner. Exposure to anti-VEGF antibody at 0. 165 microg/ml for 72 hours, the cells exhibited typical DNA ladders. The apoptosis rate peaked at antibody concentration of 0. 825 microg/ml. RT-PCR showed a decrease of MRP and TOPO II expression but a relative constant expression of GST. The introduction of exogenous anti-VEGF ribozyme gene resulted in a decrease of the proliferative capacity and colony forming efficiency from (30.5 +/- 3.3) % in control group to (16.3 +/- 2.8) % in K562/RZ group, higher G1 and lower S ratio in cell cycle distribution in comparison with the control groups. Typical DNA fragmentation and higher Annexin V + ratio occurred in K562/RZ cells after treated with 0.5 micromot/L of As2O3 for 3 days, the apoptosis rate increased from 13.4% in control group to 31. 5% in As2O3 treated group.</p><p><b>CONCLUSION</b>Anti-VEGF antibody can inhibit growth, induce apoptosis and down-regulate the expression of MRP, TOPO II genes of K562 cells in vitro. Transfection with anti-VEGF ribozyme gene can inhibit the proliferation of the cells by delaying the progression G1 into S phase in cell cycles and induce cell apoptosis by down-regulating VEGF gene expression.</p>

Preparation of Fe3O4-magnetic nanoparticles loaded with adriamycin and its reversal of multidrug resistance in vitro / 中国实验血液学杂志

To prepare Fe(3)O(4)-magnetic nanoparticles loaded with adriamycin and investigate the reversal role of drug-loaded nanoparticles in K562 and resistant cell line K562/A02, the drug-loaded nanoparticles were prepared by using mechanical absorption polymerization at different conditions of 4 degrees C or 37 degrees C for 24 or 48 hours. The survival of cells cultured with drug-loaded nanoparticles for 48 hours was detected by MTT assay, then the growth inhibition efficacy of cells was calculated. The results showed that the growth inhibition efficacy of both two cell lines was enhanced with increasing concentration of Fe(3)O(4)-magnetic nanoparticles. The inhibitory ratio of two cell lines obtained at 4 degrees C and for 48 hours was significantly better than that at 37 degrees C and 24 hours. In conclusion, Fe(3)O(4)-magnetic nanoparticles can load adriamycin by using mechanical absorption polymerization, but depended on proper temperature and time. Furthermore, drug-loaded nanoparticles showed an ability reversing multidrug resistance.

RbAp46 gene activates the expression of IGFBP-rP1 gene in K562 leukemic cells / 中华血液学杂志

<p><b>OBJECTIVE</b>To explore the mechanism of action of RbAp46 gene on leukemic cells.</p><p><b>METHODS</b>K562 leukemic cells and SHG44 glioma cells were transfected with eukaryotic expression vector carrying full-length cDNA of RbAp46 driven by the cytomegalovirus promoter mediated by lipofectamine transfection reagent. Empty vector were transfected at the same time as control. G418-resistant colonies were selected after 3 weeks culturing. Series genes were amplified using RT-PCR. Growth curve and colony formation assays were performed.</p><p><b>RESULTS</b>The number of K562/RbAp46 and K562/CMV cells were (90.00 +/- 8.40) x 10(4) and (119.58 +/- 9.87) x 10(4), respectively after 4 days growth, and SHG44/RbAp46 and SHG44/CMV cells were (89.13 +/- 4.88) x 10(4) and (149.42 +/- 10.83) x 10(4), respectively after 5 days growth. Seven-day yields of K562/RbAp46 and K562/CMV cell colonies were 131.67 +/- 15.57 and 250.33 +/- 26.31, respectively (P < 0.01), while those of SHG44/RbAp46 and SHG44/CMV cells were 50.78 +/- 6.77 and 206.67 +/- 37.18, respectively (P < 0.01). The fraction of K562/RbAp46 and K562/CMV cells in S phase was (48.88 +/- 4.35)% and (62.78 +/- 4.78)% (P < 0.01), and in G(0)/G(1) phase was (29.10 +/- 4.14)% and (22.40 +/- 2.43)%, respectively (P < 0.05), and that of SHG44/RbAp46 and SHG44/CMV cells in G(0)/G(1) phase was 65.6% and 48.8%, and in S phase was 22.6% and 38.4%, respectively. Insulin-like growth factor binding protein-related protein-1 (IGFBP-rP1) gene was induced to express only in the RbAp46-over expressing K562 cells and was not in SHG44 cells.</p><p><b>CONCLUSION</b>A regulatory pathway between RbAp46 and IGFBP-rP1 genes might exit in K562 leukemic cells.</p>

Inhibition of K562 cell growth and tumor angiogenesis in nude mice by transfection of anti-VEGF hairpin ribozyme gene into the cells / 中华血液学杂志

<p><b>OBJECTIVE</b>To explore the effect of anti-VEGF hairpin ribozyme gene on the tumor cell growth and tumor angiogenesis in nude mice.</p><p><b>METHODS</b>The recombinant eukaryotic expression plasmid pcDNA-RZ containing anti-VEGF hairpin ribozyme gene and the empty vector plasmid pcDNA were introduced separately into K562 cells by lipofectamine mediation and positive clones were screened by G418. Ribozyme gene in K562 cells was confirmed by PCR. Fluorescent real time RT-PCR and Western blot were used to detect the expression of VEGF mRNA and protein in the leukemia cells. The tumorigenicity of transfected K562 cells were transplanted in nude mice and tumor microvascular density (MVD) were observed by morphology and vWF immunohistochemistry stain.</p><p><b>RESULTS</b>Stable expression of the ribozyme gene in K562 cells was confirmed by PCR. The level of VEGF mRNA and protein decreased dramatically in K562/RZ cells when compared with K562 or K562/PC (K562 cells transfected with empty vector) cells. The tumor volumes were (4.43 +/- 0.87), (3.96 +/- 0.94), (2.24 +/- 0.56) cm3; tumor weight was (4.43 +/- 0.87), (3.96 +/- 0.94), (2.24 +/- 0.56)g; and tumor microvascular density was 4.70 +/- 1.25, 4.67 +/- 1.31, 1.80 +/- 1.55 in K562, K562/PC and K562/RZ cell groups, respectively.</p><p><b>CONCLUSION</b>Transfection with anti-VEGF ribozyme gene can inhibit tumor growth and vessel formation by down-regulating the VEGF gene expression in K562 cells.</p>

The down regulation of VEGF gene expression may link to change the expression profile of genes in leukemia cell line K562 / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To explore the potential effects of anti-VEGF hairpin ribozyme gene to gene expression profiles in leukemia cell line K562.</p><p><b>METHODS</b>The lipofectamine mediation was used to transfect the recombinant eukaryotic expression plasmid (pcDNA3-RZ) containing anti-VEGF hairpin ribozyme gene and the non-recombinant vector as control into K562 cells. And the positive clones were screened by G418. Ribozyme gene in K562 cells was confirmed by PCR. Fluorescent real time reverse transcription-PCR(RT-PCR) and Western blotting were employed to detect the expression of VEGF mRNA and protein in leukemia cells. cDNA microarray was used to explore the alteration of gene expression profiles when decreasing VEGF gene expression in leukemia cells. Expression of PCNA and GSN genes were verified by semi-quantitative RT-PCR.</p><p><b>RESULTS</b>The pcDNA3-RZ and pcDNA3 had been transfected into the human leukemia cell line K562 and positive clones been screened by G418. Stable expression of the ribozyme gene in K562 cells was confirmed by PCR. The level of VEGF mRNA and protein decreased dramatically in K562-RZ cells when compared with K562 or K562-PC (K562 cell transfected with empty vector) cells. The gene expression profiles were changed by transfection of anti-VEGF hairpin ribozyme gene into K562 cells. Among 4096 gene clones on the microarray, 191 (4.86%) genes were detected to have the marked changes with 104 down-regulated and 87 up-regulated, that were functionally related to cell cycle progression, gene replication, metabolism, cell apoptosis, cell signal transduction, and oncogenes etc. An increased expression of GSN gene and a decreased expression of PCNA gene in K562/RZ cells have been detected by RT-PCR.</p><p><b>CONCLUSION</b>Down-regulation of VEGF gene by introducing anti-VEGF hairpin ribozyme gene can alter the gene expression profiles in K562 cells, leading to change of cell growth, differentiation and apoptosis in K562/RZ cells.</p>

Inhibition of vascular endothelial growth factor gene expression and proliferation of leukemia cells by RNA interference / 中华血液学杂志

<p><b>OBJECTIVE</b>To explore the feasibility of selective inhibiting VEGF expression using VEGF short hairpin RNA (shRNA) interference, and observe the effects of VEGF gene silencing on NB4 cells growth.</p><p><b>METHODS</b>Three 19 bp reverse repeated motifs targeting exons 3, 4, 5 respectively of VEGF gene were synthesized and cloned into eukaryotic expression plasmid pGenesil-1 containing U6 shRNA promoter and termination signal of RNA polymerase. The recombinant plasmids pGenesil-VR1, pGenesil-VR2, pGenesil-VR3 and pGenesil-con (plasmid containing random DNA fragment) were transfected into NB4 cells respectively through lipofectamine reagent. The alteration of VEGF expression was examined by fluorescent real time RT-PCR and Western blot. The proliferation capacity of leukemia cells was measured by trypan blue exclusion, MTT assay, colony formation assay and cell cycles analysis.</p><p><b>RESULTS</b>Recombinant plasmids containing three shRNAs and random fragment were successfully constructed and transfected into NB4 cells respectively by liposome-mediated gene transfer method. shRNA in pGenesil-VR3 cells knocked down the expression of VEGF mRNA and protein dramatically in a sequence-specific manner when compared with that of pGenesil-VR1, Genesil-VR2 and pGenesil-con. The NB4 cells transfected with pGenesil-VR3 (NB4-VR3) had a more significant decrease in proliferation ability than NB4 and that transfected with pGenesil-con (NB4-con). The colony forming efficiencies of NB4-VR3, NB4-con and NB4 cell were (13.3 +/- 3.8)%, (21.3 +/- 6.4)% and (24.5 +/- 5.2)%, respectively (P < 0.05). Higher G(1) and lower S proportion were found in cell cycle distribution in comparison with the control groups by FCM.</p><p><b>CONCLUSIONS</b>The shRNA can efficiently suppress VEGF expression in NB4 cells. Selective VEGF gene silence can inhibit the malignant proliferation of leukemia cells.</p>

Experimental study on apoptosis of leukemia cell line NB4 transfected with WT1 gene / 中国实验血液学杂志

In order to study the potential effects of exogenous WT1 gene isoform on apoptosis in leukemia cell line NB4 and its possible molecular mechanisms, the eukaryotic expression recombinant vector (pCB6(+)/WTA) containing full-length human WT1 isoform (WTA: -17aa/-KTS) cDNA and the vacant vector-alone were introduced into the leukemia cell line NB4 respectively by electroporation. The WTA mRNA and protein in cells were detected by RT-PCR and Western blot. Binding of Annexin V were tested by flow cytometry and agarose gel electrophoresis to verify whether exogenous WTA could induce apoptosis of NB4 cells. Expressions of p21, p53, bcl-2, bcl-XL and c-myc genes were determined by semi-quantitative RT-PCR after introducing recombinant vectors into the NB4 cells. The results showed that in exposure to As(2)O(3) at 0.8 micromol/L for 48 hours, the NB4/WTA cells exhibited the morphological hallmarks of apoptosis, the marked DNA ladder shown by gel electrophoresis, and the enhanced apoptosis rate marked by Annexin V. RT-PCR showed an increase in p21 and c-myc genes expression, a decrease in bcl-2 and a relative constant expression of p53, bcl-XL in NB4/WTA cells. It is concluded that the introduction and expression of exogenous WTA gene can lead to apoptosis of NB4/WTA cells by down-regulating the Bcl-2 gene expression and up-regulating the p21 and c-myc genes expression.

The influence of different WT1 gene isoforms expression pattern on the differentiation of leukemia cell line NB4 / 中华血液学杂志

<p><b>OBJECTIVE</b>To study the potential effects of exogenous WT1 gene isoform on the differentiation of leukemia cell line NB4 and its possible molecular mechanisms.</p><p><b>METHODS</b>The recombinant eukaryotic expression vector (pCB6 + /WTA) containing full-length human WT1 isoform (WTA: -17AA/ -KTS) cDNA and the blank pCB6 + vector were transfected into leukemia cell line NB4 by electroporation. The WTA mRNA and protein in cells were detected by RT-PCR and Western blot. Cell morphology, NBT reduction and CD11b antigen expression in NB4 cells were assayed to evaluate cell differentiation. Expression of PML/RARalpha, p21 and c-myc genes was determined by semi-quantitative RT-PCR after transfection.</p><p><b>RESULTS</b>Compared with NB4/WTA cells, NB4 and NB4/CMV (NB4 cells transfected with pCB6 + vector) cells had higher morphological differentiation rates and higher CD11b expression levels after exposure to ATRA for 48 hours. The percentage of NBT reduction in NB4/WTA cells was lower than that in control groups. The difference in NBT reduction rate between NB4/WTA and control cells was gradually increased after treated with ATRA for three days. The expression levels of PML/RARalpha, p21 and c-myc genes in NB4/WTA cells were notably increased.</p><p><b>CONCLUSION</b>Overexpression of exogenous WTA gene could partially inhibit the differentiation of NB4 cells by up-regulating the expression of PML/RARalpha, p21 and c-myc genes.</p>

Detection of WT1 expression in bone marrow of acute leukemia patients with real-time quantitative RT-PCR / 中华血液学杂志

<p><b>OBJECTIVE</b>To investigate Wilms' tumor gene (WT1) expression levels in bone marrow (BM) of acute leukemia patients (ALs).</p><p><b>METHODS</b>A real-time quantitative reverse transcriptase polymerase chain reaction (RQ-RT-PCR) method was established for detecting WT1 and internal reference GAPDH expression levels in BM of 108 ALs and 23 non-leukemia controls by Light Cycler.</p><p><b>RESULTS</b>The median expression levels of WT1 in 70 newly diagnosed ALs and 11 relapsed ALs were statistically higher than those in 23 ALs in complete remission (CR) and 23 non-leukemic controls (75.10 and 89.56 vs 2.07 and 1.51 respectively). No statistic differences was found between the CR group and control group, nor between the newly diagnosed group and relapsed group. Of the 70 newly diagnosed ALs, median WT1 expression level of acute granulocytic leukemias was significantly higher than that of acute monocytic leukemias (M(5)), but there was no statistic differences among the M(1), M(2), M(3) and ALL subtypes. Furthermore the WT1 levels were not correlated to peripheral WBC counts, BM blast percentage and multidrug resistant gene (mdr1) expression at presentation, but correlated to chromosome karyotypes. Dynamic analysis of WT1 levels of 2 patients on treatment showed that WT1 expression levels predicted relapse.</p><p><b>CONCLUSION</b>WT1 expression levels in ALs were strikingly higher than that in non-leukemias. WT1 can be a marker for detecting MRD and evaluating therapy efficacy in leukemias.</p>