Analysis of melanoma tumor biopsies revealed consistent patterns of IFN-γ gene expression in patients responding to ICIs, which was associated with increased expression of antigen presentation pathway genes, particularly HLA class I and class II genes, such as beta-2-microglobulin (B2M), transporter 1 ATP-binding cassette subfamily B member (TAP1), TAP2, NLR family CARD domain-containing 5 (NLRC5), and class II major histocompatibility complex transactivator (CIITA), which is the master regulator of MHC-II [51]. Here, B2M is linked to melanoma.