Synthesis and biological evaluation of novel shikonin-benzo[b]furan derivatives as tubulin polymerization inhibitors targeting the colchicine binding site

A novel series of shikonin-benzo[b]furan derivatives were designed and synthesized as tubulin polymerization inhibitors, and their biological activities were evaluated. Most compounds revealed the comparable anti-proliferation activities against the Cancer cell lines to that of shikonin and simultaneously low cytotoxicity to non-cancer cells. Among them, compound 6c displayed powerful anti-cancer activity with the IC₅₀ value of 0.18 μM against HT29 cells, which was significantly better than that of the reference drugs shikonin and CA-4. What's more, 6c could inhibit tubulin polymerization and compete with [³H] colchicine in binding to tubulin. Further biological studies depicted that 6c can induce cell Apoptosis and cell mitochondria depolarize, regulate the expression of Apoptosis related proteins in HT29 cells. Besides, 6c actuated the HT29 cell cycle arrest at G2/M phase, and influenced the expression of the cell-cycle related protein. Moreover, 6c displayed potent inhibition on cell migration and tube formation that contributes to the antiangiogenesis. These results prompt us to consider 6c as a potential tubulin polymerization inhibitor and is worthy for further study.