Tubulin inhibitory activity of a novel colchicine-binding compounds based on a dinaphthospiropyranran scaffold

Spiropyrans have been investigated for their thermo- and photochromic characteristics, but their biotherapeutic properties have not been addressed. We report anti-proliferative properties of a novel dinaphthospiropyran analogue (1). The compound 1 was synthesized by a simple and expedient method using a one-pot acid-catalyzed aldol condensation of 2-hydroxy-1-naphthaldehyde with 4-piperidone followed by an acetalization reaction. Compound 1 was submitted to anticancer drug screen in the National Cancer Institute's panel of 60 human tumor cell lines. The average concentration of 1 to inhibit 50% cell growth was 5.4 ± 0.23 µM. All cell lines responded at almost the same concentration, suggesting that the action of 1 is not selective for cancer of origin. COMPARE analysis of dose-response data revealed interaction with tubulin as the possible mechanism of action of 1. At molecular level, 1 induced tubulin reorganization in colon cancer HCT-116 cells. Under cell-free conditions, the efficacy of 1 to inhibit tubulin polymerization was comparable to that of paclitaxel and vinblastine. Molecular docking showed that compound 1 binds to the colchicine-binding site of tubulin. We conclude that dinaphthospiropyrans present a novel scaffold for the development of tubulin inhibitors.