Fig. 6.

Comparative effects of hydrogen peroxide and arsenic trioxide on Sp proteins and MMP in KU7 cells. [A] Hydrogen peroxide downregulates Sp proteins and inhibits proliferation. KU7 cells were treated with 500 μM hydrogen peroxide alone or in combination with GSH or DTT, and Sp protein expression and cell growth were determined by western blot analysis and cell counting as described in the Materials and Methods. Cell proliferation results are given as means ± SE for replicate (3) determinations, and significant (p < 0.05) growth inhibition by hydrogen peroxide (*) and reversal of this effect by GSH (**) are indicated. [B] Effects of arsenic trioxide and hydrogen peroxide on MMP. KU7 cells were treated with the compounds or catalase, and MMP was determined by confocal microscopy as described in the Materials and Methods. Effects of various inhibitors on hydrogen peroxide [C]- or arsenic trioxide [D]-induced downregulation of Sp1, Sp3 and Sp4. KU7 cells were treated with the compounds alone or in combination with various inhibitors, and Sp proteins were examined by western blot analysis as described in the Materials and Methods. β-Actin served as a loading control for the western blots. The following concentrations of inhibitors were used: SB203580 (20 μM); SP6000125 (20 μM); NAC (10 mM), ascorbic acid (200 μM); BHA (200 μM); DPI (10 μM), and catalase (2 KU).