Identification of antimitotic sulfonamides inhibiting chromosome congression

The discovery of new small-molecule inhibitors is essential to enhancing our understanding of biological events at the molecular level and driving advancements in drug discovery. Mitotic inhibitors have played a crucial role in development of anticancer drugs. Beyond traditional microtubule inhibitors, various inhibitors targeting specific mitotic factors have been developed. This study aimed to develop novel mitotic inhibitors targeting chromosome alignment. We established a cell-based screening method using Cell Division Cycle Associated 5 (CDCA5) and kinesin-5 as markers, designed to efficiently detect mitotic phenotypes characterized by aberrant bipolar spindles with some misaligned chromosomes. Through this screening, we identified CAIS-1, an aryl sulfonamide with unique antimitotic properties. CAIS-1 exhibits dual functionality by inhibiting chromosome congression at low concentrations and spindle microtubule formation at high concentrations, causing a concentration-dependent mitotic arrest, followed by apoptotic cell death. Mechanistic studies revealed that CAIS-1 directly acts on tubulin at high concentrations, thereby inhibiting tubulin polymerization in vitro. In contrast, at low concentrations, CAIS-1 functions through a mechanism distinct from GSK923295, a conventional chromosome congression inhibitor targeting Centromere-associated protein-E (CENP-E), highlighting its unique mode of action. Moreover, CAIS-2, a structural analog of CAIS-1, selectively inhibits chromosome congression without significantly affecting spindle microtubules. This observation suggests that CAIS-1 and CAIS-2 function as antimitotic sulfonamides with distinct targets beyond tubulin, thus offering additional biological potential of sulfonamide compounds. Together, CAIS-1 and CAIS-2 represent promising tools for providing new molecular insights into kinetochore function during mitosis and for exploring new approaches in anticancer drug development.