TNF superfamily cytokines overcome immune evasion in medulloblastoma

Abstract Many immunotherapies act by enhancing T cell killing of tumor cells. CD8+ cytotoxic T cells recognize antigens presented by class I major histocompatibility complex (MHC-I) proteins on tumor cells. Here we show that medulloblastomas lacking the p53 tumor suppressor do not express surface MHC-I and are therefore resistant to immune rejection. Mechanistically, this is because p53 regulates expression of the peptide transporter Tap1 and the aminopeptidase Erap1, which are required for MHC-I trafficking to the cell surface. Treatment with tumor necrosis factor (TNF) or lymphotoxin beta receptor agonist (LTβRag) rescues expression of Erap1, Tap1 and MHC-I on p53-mutant tumor cells. In vivo, TNF treatment prolongs survival and markedly augments the efficacy of the immune checkpoint inhibitor anti-PD-1. These studies identify p53 as a key regulator of immune evasion in vivo, and suggest that TNF could be used to enhance sensitivity of p53-mutant tumors to immunotherapy.