Curcumin and RL197 decrease RKO and SW480 cell growth and downregulate Sp1, Sp3 and Sp4 proteins. RKO (A) and SW480 (B) cells were treated with DMSO or different concentrations of curcumin and RL197, and after 24 hr, cell growth was determined as outlined in the Materials and Methods. Results are means ± S.E. for at least 3 replicate determinations and significant (p < 0.05) inhibition compared to DMSO (set at 100%) is indicated (*). Downregulation of Sp1, Sp3 and Sp4 proteins by different concentrations of curcumin (C) and RL197 (D) (after 24 hr) in RKO and SW480 cells was determined by western blot analysis of whole cell lysates as described in the Materials and Methods.