Major (> 50%) or complete loss of MHC-I expression on membranes of melanoma cell was associated with transcriptional repression of HLA-A, HLA-B, HLA-C, and B2M in 78/181 patients (43%), which could predict the resistance to anti-CTLA-4 antibody therapy but not anti-PD-1 therapy. This evidence concerns the gene CTLA4 and melanoma.