PLK1

PLK1 is a serine/threonine Polo-like kinase that orchestrates cell division through mitotic entry, spindle-pole functions, and cytokinesis[1]. Mechanistically, mammalian PLK1 controls centrosome maturation, spindle assembly, and microtubule attachment to kinetochores in early mitosis[2]. This mitotic role makes PLK1 relevant to cancer biology, because dysfunction may promote cancerous transformation and drive progression, and overexpression occurs in diverse human cancers with poor prognosis[3]. Compared with related isoforms, PLK1-PLK4 participate in cell-cycle processes, but reported functional emphasis differs: PLK2 and PLK4 regulate centriole duplication, PLK3 regulates DNA replication, and PLK1 regulates centrosome separation and maturation[4]. For experimental applications, PLK1 inhibition provides a direct way to perturb mitosis, because BI 2536 inhibits mammalian PLK1 at low nanomolar concentrations, induces mitotic arrest and apoptosis in human cancer cell lines, and inhibits human tumor xenograft growth in nude mice[5].