Design, synthesis, and biological evaluation of novel diphenylamine derivatives as tubulin polymerization inhibitors targeting the colchicine binding site

A novel series of diphenylamine derivatives were designed and synthesized, and their biological activities were evaluated. The anti-proliferative activities of the derivatives were tested against five human cancer cell lines (MCF-7, MDA-MB-231, A549, HeLa and HT29). Among them, compound 5f exhibited the promising anti-proliferative activity against HT29 cell lines with the IC50 value of 23 nM. Further biological studies depicted that compound 5f inhibited cancer cell migration, colony formation and angiogenesis. Besides, dynamics studies and molecular docking studies revealed that compound 5f inhibited tubulin polymerization which may be a result of the compound binding to the colchicine site of tubulin. Furthermore, compound 5f arrested HT29 cell cycle at G2/M phase, and induced HT29 cell apoptosis by upregulating cyclin B1, Bcl-2, Bax, Cleaved-caspase9, Cleaved-caspase3, PARP, Cleaved-PARP proteins, and downregulating p-cdc25c (S216), p-cdc2 (T15) proteins. Mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) were also determined to confirm the cell apoptosis process. Finally, compound 5f greatly inhibited the tumor growth in HT29 xenograft mice by 75.5% at 10 mg/kg. Meanwhile, compound 5f owned the good pharmacokinetic properties. All the results promised that 5f is of potential to act as an antitumor candidate and worthy of further investigation.