CKAP4 is under regulation of IL-6. (A) Western blotting shows CKAP4 levels in 13 myeloma cell lines. Red, IL-6–dependent cells. (B) CKAP4 mRNA expressions in MM.1S and OPM-2 cells treated with increasing dosage of IL-6 for 24 hours, and shows the protein levels (C). (D) Schematic illustration of STAT1 binding sites (BS), sequences and positions on the CKAP4 promoter. (E) Luciferase assay of a 1050-bp hCKAP4-promoter in HEK293T cells co-transfected with increasing amount of STAT1 plasmid. (F) The STAT1 BS on the CKAP4 promoter in MM.1S cells by ChIP-PCR. (G) Levels of p-p65 and IκB-α in MM.1S treated with increasing dosage of DKK1 with or without IL-6, or with or without CKAP4 overexpression (H) for 1 hour. (I) Immunohistochemistry staining of IL-6 and CKAP4 proteins in bone marrow biopsies from 2 patients and healthy donor. Scale bar, 100 μm.