Copper-Plumbagin Complex Produces Potent Anticancer Effects by Depolymerizing Microtubules and Inducing Reactive Oxygen Species and DNA Damage

Here, we have synthesized a copper complex of plumbagin (Cu-PLN) and investigated its antiproliferative activities in different cancer cells. The crystal structure of Cu-PLN showed that the complex was square planar with a binding stoichiometry of 1:2 (Cu/Plumbagin). Cu-PLN inhibited the proliferation of human cervical carcinoma (HeLa), human breast cancer (MCF-7), and murine melanoma (B16F10) cells with half-maximal inhibitory concentrations (IC50) of 0.85 +/- 0.05, 2.3 +/- 0.1, and 1.1 +/- 0.1 mu M, respectively. Plumbagin inhibited the proliferation of HeLa, MCF-7, and B16F10 cells with IC50 of 7 +/- 0.1, 8.2 +/- 0.2, and 6.2 +/- 0.4 mu M, respectively, showing that Cu-PLN is a stronger antiproliferative agent than plumbagin. Interestingly, Cu-PLN showed much stronger toxicity against breast carcinoma and skin melanoma cells than noncancerous breast epithelial and skin fibroblast cells, indicating its specific cytotoxicity toward cancer cells. A short exposure of Cu-PLN triggered microtubule disassembly in cultured cancer cells, and the complex also inhibited the polymerization of purified tubulin much more strongly than plumbagin. Furthermore, Cu-PLN inhibited the binding of colchicine to tubulin. In addition to microtubule depolymerization, the antiproliferative mechanism of Cu-PLN involved induction of reactive oxygen species, reduction of the mitochondrial membrane potential, and DNA damage. Moreover, the cytotoxic effects of Cu-PLN reduced significantly in cells pre-treated with N-acetyl cysteine, suggesting that reactive oxygen species generation is crucial in Cu-PLN's mode of action. Thus, the complexation of plumbagin with copper yields a promising antitumor agent having a stronger antiproliferative activity than cisplatin, a widely used anticancer drug.

Automated summary

We synthesized a copper complex of plumbagin (Cu-PLN) and evaluated its antiproliferative activities in different cancer cells. Cu-PLN showed stronger inhibitory effects on the proliferation of cervical carcinoma, breast cancer, and melanoma cells compared to plumbagin. The mechanism of action of Cu-PLN involved microtubule disassembly, reactive oxygen species generation, mitochondrial membrane potential reduction, and DNA damage. These findings suggest that Cu-PLN has potential as a promising antitumor agent.