The tumor associated antigen PRAME exhibits dualistic functions that are targetable in diffuse large B cell lymphoma

PRAME is a prominent member of the cancer germline antigen family of proteins, which triggers autologous T-cell mediated immune responses. Integrative genomic analysis in diffuse large B-cell lymphoma (DLBCL) uncovered recurrent, and highly focal deletions of 22q11.22 including the PRAME gene, which were associated with poor outcome. PRAME-deleted tumors showed cytotoxic T-cell immune escape and were associated with cold tumor microenvironments. In addition, PRAME down-modulation was strongly associated with somatic EZH2 Y641 mutations in DLBCL, and PRC2-regulated genes were repressed in isogenic PRAME KO vs. PRAME wt lymphoma cell lines, with PRAME directly interacting with EZH2 as a negative regulator. EZH2 inhibition with EPZ-6438 abrogated these extrinsic and intrinsic effects leading to PRAME and microenvironment restoration in vivo. Our data highlight multiple functions of PRAME during lymphomagenesis, and provide a preclinical rationale for synergistic therapies combining epigenetic re-programming with PRAME-targeted therapies. Overall design: Isogenic PRAME knock-out (KO) cell lines were created using CRISPR/Cas9 genome editing in DLBCL cell lines SU-DHL-4, Karpas-422 and HBL-1. RNAseq analysis was performed to derive PRAME KO-associated gene signatures.