Identification of novel 1-indolyl acetate-5-nitroimidazole derivatives of combretastatin A-4 as potential tubulin polymerization inhibitors

Abstract

Microtubules are essential for the mitotic division of cells and have become an attractive target for anti-tumour drugs due to the increased incidence of cancer and significant mitosis rate of tumour cells. In this study, a total of six indole 1-position modified 1-indolyl acetate-5-nitroimidazole derivatives were designed, synthesized, and evaluated for their ability to inhibit tubulin polymerization caused by binding to the colchicine-binding site of tubulin. Among them, compound 3 displayed the best ability to inhibit tubulin polymerization; it also exhibited better anti-proliferative activities than colchicine against a panel of human cancer cells (with IC₅₀ values ranging from 15 to 40nM), especially HeLa cells (with IC₅₀ values of 15nM), based on the cellular cytotoxicity assay results. Moreover, cellular mechanism studies indicated that compound 3 could induce G2/M phase arrest and apoptosis of HeLa and MCF-7 cells, which were associated with alterations in the expression of cell cycle-checkpoint related proteins (Cyclin B1, Cdc2, and P21) and a reduction in the mitochondrial membrane potential as well as alterations in the levels of apoptosis-related proteins (PARP, Caspase 9, Bcl-2, and Bax) of these cells, respectively. Importantly, in vivo studies further revealed that compound 3 could dramatically suppress HeLa cell xenograft tumour growth compared with vehicle and CA-4 phosphate (CA-4P), and no signs of toxicity were observed in these mice. Collectively, these in vitro and in vivo results indicated that compound 3 might be a promising lead compound for further development as a potential anti-cancer drug.

Keywords: Apoptosis; Cell cycle; Colchicine; Colchicine (PubChem CID: 6167); Combretastatin A-4 (CA-4); Combretastatin A-4 (PubChem CID: 5351344); Microtubule; Paclitaxel (PubChem CID: 36314).