[Mechanism of Anti Apoptosis and Immune Evasion in Drug-Resistant Leukemia Cells Mediated by STAT3]

To investigate the mechanisms of anti-apoptosis and immune evasion in drug-resistant leukemia cells mediated by STAT3, further to explore the possible mechanism of leukemia relapse caused by minimal residual.Drug-resistance leukemia cell line was established by transfecting pcDNA3.1-STAT3 into K562 cells (K562/STAT3). The expression of STAT3, BAX and NKG2D ligands (MICA and ULBP1) in K562/-cells, K562/STAT3 were detected by Western blot and/or RQ-PCR. Cells apoptosis and the killing effect of NK cells on leukemia cells were detected by flow cytometry.The expression of the total STAT3, STAT3 phosphorylation in K562/STAT3 was significantly increased, and P-gp mRNA expression was increased also significantly (P0.005). In K562/STAT3 cells, the expression of pro-apoptotic BAX (P=0.005) was significantly lower, and the number of apoptotic cells (P=0.002) induced by adriamycin was significantly decreased as compared with those in K562/- cells. After K562/STAT3 cells were treated by STAT3 inhibitor (SH-4-54), the expression of BAX mRNA (P=0.017) was significantly higher and the number of apoptotic cells (P=0.005) was significantly increased. The MICA and ULBP1 mRNA expression in K562/STAT3 cells was significantly lower than that in K562/- cells, and also for MICA and ULBP1 protein (MICA and ULPB1 mRNA: P0.0001, MICA protein: P=0.001, ULPB1 protein: P=0.022). After K562/STAT3 cells were treated with STAT3 inhibitor (SH-4-54), the expression of MICA mRNA and protein was increased (mRNA: P=0.001, protein: P=0.002), but ULBP1 mRNA and protein showed no significantly change (mRNA: P=0.137, protein: P=0.1905). The cytotoxicity of NK cells to K562/STAT3 cells was susceptible as compared with K562/- (P=0.002), but the cytotoxicity of K562/STAT3 cells to NK cell could be recovered by STAT3 inhibitor (P=0.006).STAT3 phosphorylation can inhibits cell apoptosis and promotes cell immune escape. STAT3 inhibitors can promote the apoptosis of leukemia cells and increase their sensitivity to NK cells.STAT3介导耐药白血病细胞抗凋亡和免疫逃逸机制的研究.研究STAT3在耐药白血病细胞凋亡及免疫逃逸中的作用，并探讨白血病微小残留病引起的白血病复发的可能机制.用pcDNA3.1-STAT3质粒转染K562细胞，建立耐药白血病细胞株K562/STAT3细胞。RQ-PCR和（或）Western blot检测空载质粒转染的对照细胞株K562/-细胞和K562/STAT3细胞中STAT3、BAX以及NKG2D配体的表达。流式细胞术检测K562/-细胞和K562/STAT3细胞的凋亡情况及NK细胞对K562/-细胞和K562/STAT3细胞的杀伤作用.K562/STAT3细胞中总STAT3和STAT3磷酸化水平均明显升高，而且其耐药蛋白P-gp mRNA的表达明显升高（P0.005）。与K562/-细胞相比，K562/STAT3细胞促凋亡基因BAX mRNA的表达水平明显下降（P=0.005），且多柔比星引起的K562/STAT3细胞凋亡明显减少（P=0.002）；用STAT3抑制剂（SH-4-54）处理K562/STAT3细胞后，促凋亡基因BAX mRNA的表达水平明显升高（P=0.017），同时细胞凋亡也明显增加（P=0.005）。与K562/-细胞相比，K562/STAT3细胞NKG2D配体（MICA和ULBP1）mRNA的表达水平明显下降（P0.0001），MICA和ULBP1蛋白的表达水平亦明显下降（MICA：P=0.001，ULBP1：P=0.022）；用STAT3抑制剂（SH-4-54）处理K562/STAT3细胞后，MICA mRNA和蛋白表达水平升高（mRNA：P=0.001，蛋白：P=0.002），但ULBP1 mRNA和蛋白无明显改变（mRNA：P=0.137，蛋白：P=0.1905）。NK细胞对耐药K562/STAT3细胞的杀伤能力较K562/-细胞下降（P=0.002），但是STAT3抑制剂恢复了K562/STAT3细胞对NK细胞的杀伤敏感性（P=0.006）.STAT3磷酸化介导了耐药白血病细胞抗凋亡，降低其对NK细胞的杀伤敏感性。STAT3抑制剂可以促进耐药白血病细胞凋亡并增加其对NK细胞的杀伤敏感性.