Decitabine Enhances the Sensitivity of Leukemia Stem Cell to Allo-NK Cell-Mediated Killing / 中国实验血液学杂志

<p><b>OBJECTIVE</b>To investigate the allo-NK cell-mediated killing effect enhanced by decitabine on leukemia stem cells(LSC) and the underlying mechanisms.</p><p><b>METHODS</b>LSC were separated from KG1a cells by using immunomagnetic beads. Allo-NK cells were isolated and purified from PBMC of healthy donors. Cytotoxicity of allo-NK cells against LSC were measured by LDH releasing assay. The apoptosis induced by allo-NK cells in LSC and the expressions of NKG2D ligands including MICA/B and ULBP1-3 on LSC were detected by flow cytometry.</p><p><b>RESULTS</b>The killing rate of allo-NK cells to LSC treated with 10 µmol/L decitabine for 24 hours was significant higher than that to LSC without treatment(60.52%±3.52% vs 22.08%±2.07%, 73.93%±2.33% vs 28. 99%±3.13%, 83.08%±1.32% vs 36.44%±2.40%, respectively)at the effector-target ratios of 5:1, 10:1, 20:1 (P<0.05). At the effector-target ratio of 10:1, decitabine significantly enhanced the apoptosis of LSC induced by allo-NK cells (7.84%±0.34% vs 3.33%±0.64%)(P<0.05). The expressions of NKG2D ligands(MICA/B,ULBP1,ULBP2,ULBP3) on LSC treated with decitabine 10 µmol/L for 24 hours were significantly increased (P<0.05).</p><p><b>CONCLUSION</b>Decitabine may enhance the allo-NK cell-mediated killing effects on LSC by up-regulation of the expressions of NKG2D ligands on LSC.</p>

Drug resistance of leukemic stem cells mediated by hedgehog signaling pathway / 中国实验血液学杂志

Drug resistance and relapse are the major challenge for current treatment of acute leukemia. It is critical for ultimately curing leukemia to overcome chemoresistance of leukemic stem cells (LSC) and to eradicate LSC. Recent studies have found that abnormal activated Hedgehog (HH) signaling pathway plays an important role in a wide variety of tumors and regulates multi-drug resistance of LSC. This review briefly summarizes the molecular mechanism of HH signal pathway inducing drug resistance of LSC and leading to novel strategies for eradicating LSC.

Cytotoxicity of allogenetic natural killer cells against CD34+ acute myelogenous leukemia cells / 南方医科大学学报

<p><b>OBJECTIVE</b>To study the cytotoxic effect of allogenetic natural killer (NK) cells in vitro on human CD34+ acute myelogenous leukemia cells.</p><p><b>METHODS</b>CD34 expression on acute myelogenous leukemia KG1a cells was detected by flow cytometry. KG1a cells were co-cultured at different effector-to-target (E:T) ratios with NK cells isolated from 5 healthy individuals using magnetic cell sorting. Lactate dehydrogenase (LDH) release assay was employed to examine the cytolysis of KG1a cells in the co-culture, and the inhibition rate of the KG1a cell colony formation in methylcellulose was determined with K562 cells sensitive to NK cells as the control.</p><p><b>RESULTS</b>A expression rate as much as (98.0-/+1.1)% was detected for CD34 antigen on KG1a cells, and the isolated NK cells (CD3(-)CD16+CD56+ cells) had a purity of (93.2-/+3.7)% after magnetic cell sorting. Allogenetic NK cells exhibited obvious cytotoxicity and colony inhibition in vitro against KG1a cells at different E:T ratios, and the effects were significantly enhanced as the E:T ratios increased (P<0.05). At the same E:T ratio, the cytotoxicity and colony inhibition rate of allogenetic NK cells against KG1a cells was lower than those against K562 cells (P<0.05).</p><p><b>CONCLUSION</b>Allogenetic NK cells exhibit obvious cytotoxicity and colony formation against CD34+ acute myelogenous leukemia cells.</p>

Involvement of mitochondria apoptotic pathway in the manumycin inducing apoptosis of U937 and HL-60 / 中华血液学杂志

<p><b>OBJECTIVE</b>To investigate the apoptosis induced by manumycin in U937 and HL-60 cell lines, and to explore the role of mitochondria apoptotic pathway in manumycin-inducing apoptosis.</p><p><b>METHODS</b>Leukemic cells line U937 and HL-60 were treated by manumycin at 2 micromol/L for different time. Apoptosis of leukemia cells was detected by flow cytometry. The cytosolic proteins were extracted using a digitonin buffer. The protein expression of cytochrome C, caspase-9, caspase-8, and caspase-3 were determined by western blot. Mitochondrial membrane potential was detected by JC-1.</p><p><b>RESULTS</b>In U937 and HL-60 cells, manumycin induced mitochondrial depolarization after 6 h treatment. The average red/green fluorescence ratios at 6 h were significantly (P < 0.01) lower than those at time 0, being 0.51 +/- 0.07 and 0.41 +/- 0.06 for control group respectively. Manumycin induced cytochrome C release from the mitochondria into the cytosol after 6 h treatment, and activated caspase-9, caspase-8, and caspase-3 after a 16h treatment. The broad-spectrum caspase-inhibitor Z-VAD-fmk at 50 micromol/L was able to inhibit caspase cleavage completely, but only reduced the manumycin-induced apoptosis rates by 51.69% and 56.47% in U937 and HL-60, respectively.</p><p><b>CONCLUSION</b>Manumycin induced apoptosis in U937 and HL-60 cell lines via mitochondria apoptotic pathway.</p>