The antioxidant GSH attenuates curcumin and RL197-induced responses. RKO cells were treated with curcumin and RL197 for 24 (A) or 18 (B) hr, and induction of ROS was investigated by FACS analysis as outlined in the Materials and Methods. RKO cells were treated with DMSO, curcumin, and RL197 alone and in combination with GSH for 12 (C) or 24 (D) hr, and effects on MMP or cell proliferation, respectively, were determined as outlined in the Materials and Methods. Results are means ± S.E. for at least 3 replicate determinations, and significant (p < 0.05) induction of ROS, MMP or cell proliferation (*) and inhibition after cotreatment with GSH (**) is indicated.