Decreased expression of B7 costimulatory molecules and major histocompatibility complex class-I in human hepatocellular carcinoma

Background and Aim: We analyzed the expression of antigen‐processing and antigen‐presenting molecules in surgically resected fresh samples of human hepatocellular carcinoma (HCC) tissue to elucidate a mechanism of immune escape. We also examined the expression of interleukin (IL)‐10 protein, which might act to downregulate expression of antigen‐processing and antigen‐presenting molecules. Methods: Twenty‐eight HCC samples obtained by surgical resection were analyzed for the expression of β2‐microglobulin, heat‐shock protein (HSP)‐70, human leukocyte antigen (HLA) class‐I, CD80 (B7‐1), CD86 (B7‐2) and IL‐10 by immunostaining. Results: β2‐Microglobulin and HSP‐70 were preserved in all samples. In contrast, the expression of HLA class‐I molecules was significantly reduced according to lowering in the histological grading of tumor differentiation (P = 0.024). Furthermore, B7‐1 and B7‐2 expression was reduced in tumor cells compared with corresponding areas of liver tissue without malignant involvement irrespective of the histological grading of tumors (21% and 36%, respectively). Although IL‐10 protein was expressed in 54% of HCC, no relationship between the expression of IL‐10 and downregulation of B7‐1, B7‐2, and HLA class‐I was evident. Conclusion: These findings suggest the potential role of B7 co‐stimulatory molecules and HLA class‐I molecules in facilitating HCC escape from immune surveillance without the involvement of IL‐10.