Molecular abnormalities in the expression of HLA class-I antigens by melanoma cells.

Testing of a panel of cultured human melanoma cells with radiolabelled anti-HLA-class-I monoclonal antibodies (MAbs) in a binding assay has shown lack of reactivity of FO-I and SK-MEL-33 cells and low reactivity of SK-MEK-19 cells. SDS-PAGE analysis of the components immunoprecipitated from the 3 intrinsically radiolabelled melanoma cell lines by antibodies to the 2 subunits of HLA-class-I antigens has not detected beta 2-mu in the immunoprecipitates from melanoma cells FO-I and SK-MEL-33 and only a low level of HLA-class-I heavy chain in the immunoprecipitate from SK-MEL-19 cells. Northern blotting analysis with probes specific for HLA-class-I heavy chain and for beta 2-mu indicates that the abnormalities in HLA-class-I-antigen expression reflects a defect at the transcriptional level in FO-I cells and at the post-transcriptional level in SK-MEL-19 and in SK-MEL-33 cells. FO-I, SK-MEL-19 and SK-MEL-33 cells represent useful models to analyze the molecular mechanisms underlying the loss of HLA-class-I-antigen expression which is often associated with malignant transformation of melanocytes and to characterize the role of HLA-class-I antigens in the biology of melanoma cells and in their interactions with effector cells.