ERAP1-dependent antigen cross-presentation determines efficacy of adoptive T cell therapy in mice

Cytotoxic T lymphocytes can reject established tumors if their target peptide is efficiently presented by major histocompatibility complex class I molecules (pMHC-I) on the surface of cancerous cells. Therapeutic success upon adoptive T cell transfer (ATT), however, requires additional cross-presentation of the same pMHC-I on non-cancerous cells. Endoplasmic reticulum aminopeptidase 1 (ERAP1) is an enzyme that customizes the N-terminus of proteasome-generated peptides so they can be loaded onto MHC-I molecules in the endoplasmic reticulum (ER). We show here that ERAP1 is critically involved in the process of tumor rejection and assumes a dual role by independently operating on both sides. Direct presentation of two MHC-I restricted epitopes of a cancer-driving transplantation rejection antigen through ERAP1 moderately affected tumor rejection by adoptively transferred T-cell receptor (TCR) gene-modified T cells in each case. ERAP1 expression by antigen cross-presenting cells of the ATT recipients was critical for expansion of therapeutic monospecific T cells and correlated with tumor rejection. Specifically, lack of ERAP1 expression in the ATT recipient's non-cancerous cells enabled progression of pMHC-I-positive, IFNγ-responsive tumors, despite the presence of antigen-specific functional cytotoxic T lymphocytes. These data reveal a decisive role for ERAP1 in T cell mediated tumor rejection and will enhance the choice of MHC-I-restricted epitopes targeted by adoptive T cell transfer. Significance: This study demonstrates a role of ERAP1 in the efficacy of adoptive T-cell transfer and has potential to improve personalized T-cell therapy for solid tumors.