Curcumin is a biologically active copper chelator with antitumor activity

Abstract

Background: Curcumin is a natural product with antitumor activity. The compound targets multiple cell signaling pathways, including cell survival and proliferation, caspase activation and oncogene expression. As a β-diketone, curcumin also exists as a keto-enol tautomer that chelates transition metal ions with high affinity.

Purpose: Copper has an integral role in promoting tumor growth and angiogenesis. This study aims to investigate whether curcumin exerts its antitumor activity through copper chelation.

Methods: Copper chelation ability of curcumin was validated by measuring US/VIS spectrum. The antitumor activity and in vivo copper removal ability of curcumin was determined in a murine xenograft model. The effect of curcumin on copper-induced MAPK activation and cell proliferation was determined in cell culture system.

Results: Administration of curcumin to tumor-bearing animals resulted in suppression of A549 xenograft growth, an effect that was also observed in animals treated with ammonium tetrathiomolybdate (TM), a metal chelator used for copper storage disorders clinically. The inhibition on tumor growth was associated with reduction of copper concentrations in the serum of treated groups. In cell culture studies, we showed that copper promoted cell proliferation through Erk/MAPK activation. Treatment with curcumin or U0126, a specific MAPK inhibitor, or suppression of cellular uptake of copper by siRNA knockdown of copper transporter protein 1 (CTR1) blocked copper-induced cell proliferation.

Conclusions: This study therefore demonstrates curcumin antitumor effect to its copper chelation capability. These results also implicate copper chelation as a general mechanism for their action of some biologically active polyphenols like flavonoids.

Keywords: Antitumor; Copper chelation; Curcumin; MAPK.