The SEI1 directly interacts with the enhancer factors CREB‐binding protein (CBP)/p300 and RNA polymerase II (pol II)‐associated factor 1 (PAF1) complex, promoting transcriptional activity and leading to upregulation of programmed death ligand‐1 (PD‐L1) and immune escape in myeloma. This evidence concerns the gene EP300 and plasma cell myeloma.