A novel colchicine-based microtubule inhibitor exhibits potent antitumor activity by inducing mitochondrial mediated apoptosis in MIA PaCa-2 pancreatic cancer cells.

Colchicine, an antimitotic alkaloid isolated from Colchicum autumnale, is a classical drug for treatment of gout and familial Mediterranean fever. It causes antiproliferative effects through the inhibition of microtubule formation, which leads to mitotic arrest and cell death by apoptosis. Here, we report that a novel colchicine analog, 4o (N-[(7S)-1,2,3-trimethoxy-9-oxo-10-[3-(trifluoromethyl)-4-chlorophenylamino]-5,6,7,9-tetrahydrobenzo[a]heptalen-7-yl]acetamide), which exhibited potent anticancer activities both in vitro and in vivo. In this study, 4o with excellent pharmacokinetic profile and no P-gp induction liability displayed strong inhibition of proliferation against various human cancer cell lines. However, pancreatic cancer cell line MIA PaCa-2 was found to be more sensitive towards 4o and showed strong inhibition in concentration and time-dependent manner. By increasing intracellular reactive oxygen species (ROS) levels, 4o induced endoplasmic reticular stress and mitochondrial dysfunction in MIA PaCa-2 cells. Blockage of ROS production reversed 4o-induced endoplasmic reticulum (ER) stress, calcium release, and cell death. More importantly, it revealed that increased ROS generation might be an effective strategy in treating human pancreatic cancer. Further 4o treatment induced mitotic arrest, altered the expression of cell cycle-associated proteins, and disrupted the microtubules in MIA PaCa-2 cells. 4o treatment caused loss of mitochondrial membrane potential, cytochrome c release, upregulation of Bax, downregulation of Bcl-2, and cleavage of caspase-3, thereby showing activation of mitochondrial mediated apoptosis. The in vivo anticancer activity of the compound was studied using sarcoma-180 (ascitic) and leukemia (P388 lymphocytic and L1210 lymphoid) models in mice and showed promising antitumor activity with the least toxicity unlike colchicine. Such studies have hitherto not been reported. Taken together, these findings highlighted that 4o, a potent derivative of colchicine, causes tumor regression with reduced toxicity and provides a novel anticancer candidate for the therapeutic use.