Johnson et al. [38] analyzed the level of MHC class II cell surface receptor- human leukocyte antigen—DR isotype (HLA-DR) expression in tumor biopsies from melanoma patients treated with anti-PD-1 or anti-PD-L1 therapy and reported the association of a high level of MHC II (HLA-DR) expression with improved clinical response, as well as longer PFS and OS, compared to patients with a low MHC II expression. The gene discussed is CD274; the disease is melanoma.