Natural killer (NK) cells are important effector cells for the first line of defense against tumor. Distant MHC class I homolog MICA has been identified as human ligand for NK cell activating receptor NKG2D. Engagement of MICA triggers NK cells and augments antigen-specific CTL anti-tumor immunity. However, the expression level of MICA and its clinical significance in hepatocellular carcinoma remains to be elucidated. In the present study, a hospital-based study cohort of 143 HCC patients was involved. MICA expression levels were determined by immunohistochemical staining. The association of MICA expression with tumor clinicopathologic features, disease-free survival, and overall survival of HCC patients were analyzed. Significantly decreased expression of MICA was detected in tumor specimens. MICA expression was significantly associated with AFP level (P < 0.001) and tumor node metastasis stage (P = 0.003). Patients with reduced level of MICA had a statistically significantly shorter disease-free survival and overall survival duration than patients with preserved expression of MICA. However, in multivariate analysis, MICA expression level was found not to be an independent prognostic factor for both disease-free survival and overall survival of HCC patients. Our findings suggest that decreased MICA expression may play an important role in HCC tumor evasion of host immunity, which warrants further investigation in future studies.
Keywords: MHC class I-related chain; hepatocellular carcinoma; immunohistochemistry.