RUNX2 and acute myeloid leukemia: To test if IGK is expressed in AML cells, we performed immunocytochemical studies using monoclonal anit-human IgK in 6 AML cell lines, HEL, HL-60, KG-1, NB4, OCI-AML3 and THP-1, and found strong cytoplasmic staining in all 6 AML cell lines (Figure 1A).