Curcumin inhibits nuclear β-catenin signaling. (A)Curcumin inhibits β-catenin transcription activity. A2780CP cells were transiently transfected with TOPFlash or FOPFlash and co-transfected with Renilla luciferase to determine β-catenin/TCF transcription activity. The cells were treated with 20 μM curcumin, 5 μM cisplatin or a 6 hr pre-treatment with 20 μM curcumin followed by treatment with 5 μM cisplatin. After 24 hrs of incubation, cell lysates were collected and probed for luciferase activity. Treatment of A2780CP cell line with 20 μM curcumin resulted in over a 60% reduction in β-catenin activity (Mean ± SE, n = 3, *p value p < 0.017, compared to control). (B) Curcumin treatment reduces overall β-catenin and c-Myc protein levels. A2780CP cell lines were treated as in (A), protein lysates were collected and analyzed by immunoblotting for β-catenin, c-Myc and β-actin. Protein bands were quantified by densitometry, normalized to β-actin, scaled to the DMSO control and expressed as relative expression levels (number beneath the blots). Curcumin treatment caused a 50% reduction in β-catenin and c-Myc levels.