In a variety of tumors that target LILRB4 as a protein, such as AML, a commonly used immunotherapeutic strategy is to use a monoclonal antibody or inhibitor against LILRB4 to inhibit the attachment of LILRB4 to its ligands, such as APOE/FN, to block LILRB4 signaling, inhibit tumor cell invasion and migration and restore the immune effector activity of immune cells. Here, APOE is linked to acute myeloid leukemia.