Function of specificity protein 1 on cell viability and protein expression of MSTO-211H cells. Sp1 expression is inhibited by mithramycin A (Mith A), a Sp1 regulatory inhibitor. (A) The cell viability effects of mithrramycin on MSTO-211H cells. MSTO-211H cells (3 × 103 cells/200 μl) were treated with Mith A of various concentrations (10–40 μM) in 5% FBS-RPMI 1640 for 24 and 48 hours. The cell proliferation effects of Mith A-treated MSTO-211H cells was determined by the MTS assay. (B) Analysis of DNA fragmentation and nuclear condensation by fluorescence microscopy (magnification X600) after Mith A treatment in MSTO-211H cells. DNA fragmentation and nuclear condensation were quantified, and the results in triplicate are expressed as the mean ± SD. Data are indicated from three independent experiments. The asterisks (*) indicates p < 0.05 versus control cells. (C) The effect of Mith A on the expression of Sp1 protein, Sp1 regulatory proteins and apoptotic proteins in MSTO-211H cells. MSTO-211H cells were treated with Mith A of 20 μM for 48 hours. The effect of Mith A on Sp1 protein expression levels was determined by immunoblotting, as described in the Materials and Methods.