Expression of the nonclassical HLA class I and MICA/B molecules in human hepatocellular carcinoma

HLA-G and HLA-E are nonclassical human MHC class I molecules, which promote tolerance to NK cytotoxicity. MICA and MICB are known to enhance the functions of NK and T cells. However, the expression of these molecules has never been investigated in liver cancer. Using RT-PCR and western blot, we aimed to identify the expression of HLA-G, HLA-E, MICA and MICB in a panel of 41 tissues dissecting from liver cancer patients in China. HLA-G mRNA was expressed in 8 of 41 Human Hepatocellular Carcinoma (HCC) specimens and in 1 adjacent normal hepatocellular tissue. The expression of HLA-G protein was found in 7 of the 8 HLA-G mRNA-positive HCC tissues. HLA-E mRNA was up-regulated in 56% HCC specimens but the expression of HLA-E protein was only upregulated in 29% HCC tissues in comparison with their adjacent normal counterpart. MICA and MICB mRNA was decreased in 5% and 8% HCC specimens, while the expression of their proteins decreased in 21% and 24% HCC tissues. These results suggested that the expressions of HLA-G, HLA-E, MICA and MICB were differently up-regulated in HCC tissues. Furthermore, HLA-E and MICA/B genes showed obviously distinctive expression pattern at transcription and translation level.