B2M and melanoma: Pathological analyses of the resected lesion revealed that tumor-infiltrating CD8+ T cells increased after the treatment, which is different from that in a previously reported patient with melanoma who acquired resistance due to loss of the B2M gene (MEL01) (online supplemental figure S1B and table S1).23 Accordingly, MHC-I was highly expressed in MEL04 tumor cells (online supplemental figure S1C).