Regulation of CD38 by STAT1 and STAT3. (A-B) RPMI 8226 (A) and MOLP-8 (B) cells were cultured with IL-6, IFN-β, or IFN-γ for 6 hours, and then subjected to immunoblotting using indicated antibodies. (C) STAT3 stable knockout (KO) RPMI 8226 cells were transfected with scrambled siRNA (si SC) or STAT1 siRNA (si STAT1), and then cultured with BMSC-sup or IL-6 (1 or 2 ng/mL) for 72 hours. CD38 expression was measured by flow cytometry. (D) STAT3 stable knockout RPMI 8226 cells were transfected with scrambled (SC) siRNA or STAT1 siRNA, cultured in the absence or presence of IL-6 (2 ng/mL) for 6 hours, and then subjected to immunoblotting using indicated antibodies. Relative CD38 MFI was calculated in comparison with MFI of control. Data are shown as mean plus or minus standard error of the mean. *P < .05; **P < .01; ***P < .001.