MHCI类样分子(MICA)在部分肿瘤组织和肿瘤细胞系中的表达及临床意义

目的:探讨MHC Ⅰ类样分子(MICA)在肿瘤组织和肿瘤细胞系中的表达及其临床意义.方法:分别采用半定量RT-PCR和免疫组织化学技术检测肿瘤组织和肿瘤细胞系MICA表达,MTT法测定NK细胞细胞毒活性.结果:人红白血病细胞K562、喉癌细胞系Hep2、宫颈癌细胞系Hela、肝癌细胞系HepG2和结直肠癌细胞系HT29均有MICA mRNA和蛋白表达,而人Burkitt淋巴瘤Raji和高转移肺癌PG不表达MICA.MICA表达阳性的肿瘤细胞对NK杀伤敏感性明显高于MICA阴性者.多数肿瘤组织存在MICA mRNA和蛋白表达,但并非在所有肿瘤均有表达,癌旁组织均无MICA表达.结论:肿瘤细胞表达MICA可激发NK细胞对肿瘤的杀伤,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,肿瘤细胞分泌sMICA分子为肿瘤发生免疫逃逸的机制之一.

The Expression of MICA in Some Tumor Specimens and Tumor Cells and the Clinical Significance

Objective: To investigate the expression of MHC class I chain-related gene A (MICA) in some tumor specimens and tumor cells and the clinical significance. Methods: The expression of MICA was measured by RT-PCR and by immunohistochemical method (SABC technique). The cytotoxicity of human NK cells were detected by MTT method. Results: The expression of MICA mRNA and protein was found in most tumor cell lines and tumor tissues, but was not found in paraneoplastic specimens. NK cells exert higher cytotoxicity to tumor cells with MICA expression, while tumors without MICA expression do resist against NK lysis. Conclusions: The expression of MICA on tumor cell surface can enhance the cytotoxicity of NK cells through interaction of MICA and NKG2D. Shedding of sMICA from tumor cells may promote tumor immune evasion.