Insights into the structure and tubulin-targeted anticancer potential of N-(3-bromobenzyl) noscapine

Background: Noscapine is a non-narcotic, antitussive alkaloid isolated from plants of Papaveraceae family. This benzylisoquinoline alkaloid and its synthetic derivatives, called noscapinoids, are being evaluated for their anticancer potential. Methods: The structure of a novel analogue, N-(3-bromobenzyl) noscapine (N-BBN) was elucidated by X-ray crystallography. Effect of N-BBN on cancer cell proliferation and cellular microtubules were studied by sulphorhodamine B assay and immunofluorescence, respectively. Binding interactions of the alkaloid with tubulin was studied using spectrofluorimetry. Results: N-BBN, synthesized by introducing modification at site B ('N' in isoquinoline unit) and a bromo group at the 9th position of the parent compound noscapine, was found to be superior to many of the past-generation noscapinoids in inhibiting cancer cell viability and it showed a strong inhibition of the clonogenic potential of an aggressively metastatic breast tumour cell line, MDA-MB-231. The compound perturbed the tertiary structure of purified tubulin as indicated by an anilinonaphthalene sulfonic acid-binding assay. However, substantiating the common feature of noscapinoids, it did not alter microtubule polymer mass considerably. In cells, the drug-treatment showed a peculiar type of disruption of normal microtubule architecture. Conclusion: N-BBN may be considered for further investigations as a potent antiproliferative agent. (c) 2018 Institute of Pharmacology, Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved.