中文摘要：

目的探讨替莫唑胺（TMz）短期化疗下P57在胶质母细胞瘤细胞增殖抑制中的作用和机制。方法通过Western blotting检测P57和核增殖抗原（Ki-67）在TMZ短期化疗后U87细胞中的表达情况：通过Western blotting和免疫组化染色比较原发性和复发性（经TMZ治疗）胶质母细胞瘤临床标本中P57的表达差异；通过干扰P57的表达，检测TMZ短期化疗下和撤药后U87细胞凋亡、细胞周期和细胞活力的变化。结果TMZ短期化疗后，U87细胞中P57蛋白表达量明显升高．而Ki-67表达量明显下降；胶质母细胞瘤临床标本中复发性肿瘤的P57表达量高于原发性肿瘤；干扰P57表达后周期素依赖性激酶2（Cdk2）的表达量增加，表现为TMZ对U87细胞的增殖抑制作用减弱．但细胞凋亡率明显升高f未干扰细胞凋亡率为12．83％±1．40％，干扰组细胞凋亡率为31．00％±3．48％1；此外，撤药后，与对照组相比，P57干扰组U87细胞发生明显细胞周期阻滞和细胞活力下降。结论TMZ短期化疗下，U87细胞通过上调P57表达及下调Cdk2表达抑制肿瘤细胞增殖．同时通过抑制细胞周期进程以降低化疗损伤。

英文摘要：

Objective To analyze the relation between short-term chemotherapy of temozolomide （TMZ） and inhibition of proliferation of U87 glioblastoma cells, and investigate the role and mechanism of P57 in inhibiting U87 cells proliferation under treatment of TMZ. Methods Protein levels of P57 and proliferating cell nuclear antigen Ki-67 in U87 cells accepted TMZ short-term chemotherapy were detected by Western blotting. Protein levels of P57 in clinical primary or recurrent glioblastomas accepted TMZ short-term chemotherapy were compared by immunohistochemistry and Western blotting. After P57 was knocked down, apoptosis, cell cycle and cell vitality changes of US7 cells treated with TMZ and U87 cells with TMZ withdrawal were studied. Results After short-term chemotherapy of TMZ in U87 cells, the expression level of P57 increased but the expression level of Ki-67 decreased. The protein level of P57 in recurrent glioblastoma was higher than that in primary tumor. After P57 was knocked down in U87 cells treated with TMZ, apoptosis was enhanced and the protein level of cycle dependent kinase 2 （Cdk2） increased, which indicated that the inhibition of proliferation induced by TMZ was weakened, while the apoptosis rate increased （31.00±3.48 vs. 12.83±1.40） Furthermore, after TMZ was withdrew, the cell cycle and cell vitality in U87 control cells recovered, but in U87 cells with P57 knocked down, the cell cycle was arrested and the cell vitality was reduced. Conclusion P57 inhibits cell cycle progression or proliferation of U87 cells by up-regulating P57 expression and inhibiting Cdk2 expression to reduce the damage caused by TMZ.