RBC4 is a murine anti-human TfR1 IgM antibody that has been shown to inhibit the proliferation and induce cell death in vitro in a range of hematological cancer cell lines, such as human chronic myelogenous leukemias (CML) RPMI 8866 and UC7296 cells, as well as human Jurkat acute T-cell leukemia cells, MOLT-4 ALL (T-cell origin) cells, and HL-60 acute promyelocytic leukemia cells (APL), a subtype of AML (135). This evidence concerns the gene CD40LG and acute promyelocytic leukemia.