Updated project metadata. Melanoma is the most serious and deadly form of skin cancer and with progression to advanced melanoma, the intrinsically disordered protein α-synuclein is upregulated to high levels; and while toxic to dopaminergic neurons in Parkinson’s disease, it is highly beneficial for primary and metastatic melanoma cells. To gain detailed insights, both at the level of the proteome and the transcriptome, into this exact opposite role of α-synuclein in advanced melanoma, we performed proteome and transcriptome studies of high-level α-synuclein-expressing primary and metastatic human melanoma cell lines and metastatic human melanoma xenografts treated with the small-molecule diphenyl-pyrazole compound anle138b, which binds to and interferes with the oligomeric structure of α-synuclein. Our data demonstrate that interfering with oligomerized α-synuclein in these melanoma cells and tumor xenografts leads to a substantial upregulation of major histocompatibility complex (MHC) proteins, which are important for enhancing anti-melanoma immune responses.