Induction of microtubule hyper stabilization and robust G2 /M arrest by N-4-CN in human breast carcinoma MDA-MB-231 cells.

Abstract

Elucidation of the antiproliferative efficacy and mechanism of action of a design-optimized noscapine analog, N-4-CN. Cell viability was studied using an MTT assay. The drug-tubulin interactions were investigated using spectrofluorometry. The architectural defects, hyper stabilization, and recovery competence of cellular microtubules were studied using immunofluorescence microscopy. DCF-DH and rhodamine 123 were used as probes to to examine the levels of reactive oxygen species and the loss of mitochondrial membrane potential, respectively. Flow cytometry revealed the cell cycle progression pattern of the drug-treated cells. Among the cell lines tested, N-4-CN showed the strongest inhibition of the viability of the triple-negative breast cancer (TNBC) cell line MDA-MB-231(IC50 , 2.7±0.1µmol/L) and weakest inhibition of the noncancerous epithelial cell line, VERO (IC50 , 60.2±3µmol/L). It perturbed tertiary structure of tubulin and stabilized colchicine binding to the protein. In cells, N-4-CN hyperstabilized the microtubules, and prevented the recovery of cold-depolymerized microtubules. Its multitude of effects on tubulin and microtubules facilitated cell cycle arrest and subsequent cell death that were complemented by elevated levels of reactive oxygen species (ROS). Owing to its ability to perturb a well-defined cancer drug target, tubulin, and to promote ROS-facilitated apoptosis, N-4-CN could be investigated further as a potential therapeutic against many neoplasms, including TNBC.