Wu Jin-feng, Zeng Gui-li, Shen Wei, Yang Mei, Wang Feng, Tian Lü, Li Xuan, Hu Wen-yan, Li Xiao-ping, Ren Hong, Tang Kai-fu
Gastroenterology Department, the Second Affiliated Hospital of Chongqing Medical University, Chongqing 400010, China.
Zhonghua Gan Zang Bing Za Zhi. 2009 Sep;17(9):675-8.
Major histocompatibility complex class I C-related molecules A and B (MICA and MICB) are innate immune system ligands for the NKG2D receptor expressed by natural killer cells and activated CD8(+)T cells. Our previous study showed that 5-aza-2'-deoxycytidine (5-aza-dC), a DNA methyltransferase inhibitor, can induce the expression of MICB and sensitized cells to NKL-cell-mediated cytolysis. The aim of this study was to determine the expression level of MICA in HepG2 cells (an HCC cell line) and L02 cells ( a normal liver cell), and to investigate the effect of 5-aza-dC on MICA expression in HepG2 cells.
Cells were treated with 5-aza-dC, caffeine and ATM-specific siRNA. The cell surface MICA protein on HepG2 cells and L02 cells was determined using flow cytometry. The mRNA level was detected using real time RT-PCR.
MICA was undetectable on the surface of L02 cells, but was highly expressed on HepG2 cells. MICA expression was upregulated in response to 5-aza-dC treatment (P less than 0.05), and the upregulation of MICA was partially prevented by pharmacological or genetic inhibition of ataxia telangiectasia mutated (ATM) kinase (P less than 0.05).
Our data suggest that 5-aza-dC induces the expression of MICA by a DNA damage-dependent mechanism.
主要组织相容性复合体I类C相关分子A和B（MICA和MICB）是自然杀伤细胞和活化的CD8(+)T细胞所表达的NKG2D受体的先天性免疫系统配体。我们之前的研究表明，DNA甲基转移酶抑制剂5-氮杂-2'-脱氧胞苷（5-aza-dC）可诱导MICB的表达，并使细胞对NKL细胞介导的细胞溶解敏感。本研究的目的是确定MICA在HepG2细胞（一种肝癌细胞系）和L02细胞（一种正常肝细胞）中的表达水平，并研究5-aza-dC对HepG2细胞中MICA表达的影响。
用5-aza-dC、咖啡因和ATM特异性小干扰RNA处理细胞。使用流式细胞术测定HepG2细胞和L02细胞表面的MICA蛋白。使用实时逆转录聚合酶链反应检测mRNA水平。
在L02细胞表面未检测到MICA，但在HepG2细胞上高表达。5-aza-dC处理后MICA表达上调（P小于0.05），共济失调毛细血管扩张症突变（ATM）激酶的药理学或遗传学抑制可部分阻止MICA的上调（P小于0.05）。
我们的数据表明，5-aza-dC通过DNA损伤依赖性机制诱导MICA的表达。
