Design, synthesis and anti-cancer activity evaluation of podophyllotoxin-norcantharidin hybrid drugs.

In this study, we designed and synthesized eighteen podophyllotoxin-norcantharidin hybrid drugs which could exhibit more potent anti-cancer activity than the parent drugs. Through the anti-proliferation assay, the most potent anti-cancer agent was screened out, namely Q9 (IC50=0.88±0.18μM against MCF-7 cell line), and it showed lower cytotoxicity against non-cancer cells, human embryonic kidney cells (293T) (IC50=54.38±3.78μM). Additionally, based on the flow cytometry analysis result, it can cause a remarkable cell cycle arrest at G2/M phase and induce apoptosis in MCF-7 cells more significantly than podophyllotoxin or norcantharidin per se. Moreover, the expression of cell cycle relative protein CDK1 was up regulated while a protein required for mitotic initiation, Cyclin B1 was down regulated. Furthermore, according to the confocal microscopy observation results, it was shown that Q9 was a potent tubulin polymerization inhibitor and the effect is comparable to that of colchicine. For further investigation on the aforementioned mechanisms, we performed western blot experiments, thus finding the increase of the cleavage of PARP. Consistent with these new findings, molecular docking observations suggested that compound Q9 could be developed as a potential anticancer agent.