Lack of HLA-class I antigens in human neuroblastoma cells: analysis of its relationship to TAP and tapasin expression

: We studied the constitutive and the interferon (IFN)‐γ‐induced expression of HLA class I antigen heavy chain, β2‐microglobulin (β2m), TAP‐1, TAP‐2 and tapasin in a panel of eleven neuroblastoma cell lines. Surface expression of HLA class I antigens was low in eight out of eight neuroblastoma cell lines bearing MYC‐N amplification and/or 1p deletion, while two out of three neuroblastoma cell lines lacking these genetic alterations showed normal expression. IFN‐γ treatment restored HLA class I antigen surface expression in all neuroblastoma cell lines. Eight out of 11 neuroblastoma cell lines did not express TAP‐1 mRNA and three of them also lacked TAP‐2 mRNA. β2 m mRNA was barely detectable or absent in five neuroblastoma cell lines, while tapasin mRNA was always expressed. IFN‐γ upregulated the expression of HLA class I heavy chain, β2 m, TAP‐1, TAP‐2 and tapasin, as detected at mRNA or protein level. Post‐transcriptional events were involved in altered TAP‐1 and β2 m expression in one peculiar neuroblastoma cell line. These data indicate that multiple mechanisms play a role in the HLA class I antigen‐deficient phenotype of human neuroblastoma.