Selective inhibition of spindle microtubules by a tubulin-binding quinazoline derivative.

In the research field of tubulin-binding agents for the development of anticancer agents, hidden targets are emerging as a problem in understanding the exact mechanisms of actions. The quinazoline derivative 1-(4-methoxyphenyl)-1-(quinazolin-4yl)-ethan-1-ol (PVHD121) has anti-cell proliferative activity and inhibits tubulin polymerization by binding to the colchicine site of tubulin. However, the molecular mechanism of action of PVHD121 in cells remains unclear. Here, we demonstrate that PVHD121 delays mitotic entry and efficiently causes mitotic arrest with spindle checkpoint activation, leading to subsequent cell death. The dominant phenotype induced by PVHD121 was aberrant spindles with robust microtubules and unseparated centrosomes. The microtubules were radially distributed, and their ends appeared to adhere to kinetochores, and not to centrosomes. Extensive inhibition by high concentrations of PVHD121 eliminated all microtubules from cells. PVHD277 [1(4-methoxyphenyl)-1-(2-morpholinoquinazolin-4-yl)ethan-1- ol], a PVHD121 derivative with fluorescence, tended to localize close to the centrosomes when cells prepared to enter mitosis. Our results show that PVHD121 is an antimitotic agent that selectively disturbs microtubule formation at centrosomes during mitosis. This antimitotic activity can be attributed to the targeting of centrosome maturation in addition to the interference with microtubule dynamics. Due to its unique bioactivity, PVHD121 is a potential tool for studying the molecular biology of mitosis and a potential lead compound for the development of anticancer agents.