Curcumin and RL197-mediated activation of proteasomes and ROS. RKO (A) and SW480 (B) cells were treated with DMSO (control), curcumin, or RL197 alone or in combination with 1 μM lactacystin for 24 hr ,and effects on cell proliferation or expression of Sp1, Sp3 or Sp4 proteins (western blots) were determined as outlined in the Materials and Methods. RKO (C) and SW480 (D) cells were treated with DMSO, curcumin, RL197 alone or in combination with 5 mM GSH for 24 hr, and whole cell lysates were analyzed by western blot analysis as described in the Materials and Methods. Cell proliferation results (A, B) are means ± S.E. for at least 3 replicate experiments, and significant (p < 0.05) growth inhibition is indicated (*).