NKG2D配体在13种肿瘤细胞系中的表达及意义

Expression and Significance of NKG2D Ligandsin 13 Tumor Cell Lines

背景与目的:NKG2D及其配体的相互作用在肿瘤免疫监视中起着非常重要的作用。本研究探讨NKG2D配体在13种肿瘤细胞系中的表达及其意义。方法:采用半定量RT-PCR法检测肿瘤细胞系中NKG2D配体的mRNA表达。应用MTT法检测人NK细胞对肿瘤细胞的杀伤活性,免疫组织化学技术和Western blot法检测肿瘤细胞中MHCⅠ类相关蛋白A(MHC classⅠchain-related A)蛋白表达情况。结果:13种肿瘤细胞系表达不同水平的NKG2D配体mRNA。其中Hep2细胞中MICA强阳性表达,HeLa、HepG2、MDA231、HT29、SGC7901、M21、K562、Jurkat细胞MICA表达阳性,而Caski、PG、HL-60和Raji细胞中MICA mRNA阴性。MICA和MICB的表达水平与NK细胞杀伤活性具有高度相关性(r=0.851,P<0.001;r=0.652,P<0.05)。除ULBP3外,其余ULBP成员的表达水平与NK细胞杀伤均无相关性。结论:在6种人NKG2D配体中,MICA的表达水平与肿瘤细胞对NK细胞杀伤的敏感性关系最为密切,肿瘤细胞MICA的表达水平可能决定着机体NK细胞抗肿瘤免疫应答的强弱。

BACKGROUND ＆ OBJECTIVE： The interaction between NKG2D and its ligands plays a major role in immune surveillance against tumor. This study was to observe the expression and analyze the significance of NKG2D ligands in 13 tumor cell lines. METHODS： The mRNA expression of NKG2D ligands in K562, Raji, PG, Hep2, HepG2, HeLa, HT29, M21, MDA231, SGC7901, Caski, HL-60 and Jurkat cells was measured by reverse transcription-polymerase chain reaction （RT-PCR）, The cytotoxicity of natural killer （NK） cells to the tumor cells at different effector-to-target cell （E：T） ratios were detected by MTT assay. The expression of MICA protein was measured by SABC immunohistochemistry and Western blot. RESULTS： The 13 tumor cell lines expressed different levels of NKG2D ligands. MICA was highly expressed in Hep2 cells, but not expressed in Caski, PG, HL-60 and Raji cells. The expression of MICA and MICB were positively correlated to the cytotoxicity of NK cells （r=0.851, P〈0.001; r=0.652, P〈0.05）. Except for ULBP3, the expression of ULBP1, 2, 4 had no correlations to the cytotoxicity of NK cells. CONCLUSION： Among the 6 human NKG2D ligands, the expression of MICA is most intimate to the cytotoxicity of NK cells to tumor cells, and its expression level may determine the degree of immune response of NK cells to tumor.