六亚甲基二乙酰胺体外对白血病细胞株的抗增殖作用及其机理研究

目的　研究抗肿瘤药物六亚甲基二乙酰胺 (HMBA)在体外对人白血病细胞株U937,K5 6 2增殖和凋亡的作用 ,初步从细胞周期调控的角度探讨其作用机理。方法　应用MTT比色法和锥虫蓝拒染法观察HMBA对细胞增殖的抑制作用。用细胞周期素A/DNA双染色法检测不同浓度HMBA(1、2、4mmol/L)实验组细胞胞浆内细胞周期素A蛋白表达水平 ,并进行DNA含量分析。用异硫酸盐荧光素标记的膜联蛋白V/碘化丙啶双染色法 ,DNA片段变化和亚G1峰检测细胞凋亡。结果　 (1)HMBA能明显地抑制K5 6 2 ,U937细胞增殖 ,呈剂量依赖性 (K5 6 2细胞经HMBA干预后第六天 ,对照组、1、2、4mmol/L组MTT法的 5 95nm吸光度值分别为 1 0 3、0 81、0 5 8、0 36 )。 (2 )HMBA能剂量依赖性地下调胞浆内细胞周期素A表达水平 ,(K5 6 2细胞经HMBA干预后 ,对照组 ,1、2、4mmol/L组细胞周期素A阳性率分别为 34 4 %± 5 2 % ,16 1%± 2 5 % ,9 9%± 1 7% ,7 6 %± 2 0 % ) ,S期细胞比例与细胞周期素A的改变趋势是一致的。 (3)各实验组均未检测到有凋亡发生。结论　HMBA通过下调S G2期周期素A表达而打破了K5 6 2 ,U937细胞增殖的环节 ,是其发挥抑制白血病细胞增殖的机理之一

Effect of hexamethylene bisacetamine on proliferation and apoptosis of human leukemia cells in vitro and relevant mechanisms

OBJECTIVES: To investigate the in vitro effect of hexamethylene bisacetamine (HMBA) on the proliferation, cell cycle regulation, and apoptosis of human leukemia cells and to study the relevant mechanisms. METHODS: K562 and U937 human leukemia cells were cultured and then suspensions thereof without HMBA or with HMBA of different concentrations (1, 2, and 4 mmol/L) were made. The optical absorbance value at 595 nm of these suspensions were tested every 24 hours. The suspensions were mixed with 4% trypan blue dye solution. Live and dead cells were observed with microscope and the live cell rate was calculated. Double staining of cellular cyclin A protein/DNA was used to detect the expression levels of cyclin A protein in cytoplasm. Fluorescein isothiocyanate (FITC)-labeled annexin V/Propidiumiodide) was used to detect the apototic cells fluorescence-activated cell sorter. Gel electrophoresis was conducted to detect DNA contents. RESULT: After exposure to HMBA for 6 days, the optical absorbance values at 595nm of K562 leukemia cells of the control group and groups with 1, 2, and 4mmol/L HMBA were 1.03, 0.81, 0.58, and 0.36 respectively. After treatment of HMBA, the percentages of cyclin A positive K562 leukemia cells in control group and groups with 1, 2, and 4 mmol/L HMBA were 34.4% +/- 5.2%, 16.1% +/- 2.5%, 9.9% +/- 1.7%, and 7.6% +/- 2.0% respectively (P < 0.01). No drug-related apoptosis was found in both cell lines. CONCLUSION: HMBA inhibits cell proliferation and reduces S-phase-fraction in both cell lines dose-dependently through down-regulating the expression of cyclin A. Apoptosis is not a consequence of the proceeding mitosis arrest and is induced p53-dependently by HMBA. In both leukemia cell lines (U937 and K562) lacking wt-p53, a nonapoptotic death pathway may exist during HMBA induction.