PLK1 is a serine/threonine kinase that plays a pivotal role in cell division. Its dysregulation is tightly linked to malignant transformation. In human cancers, there is growing evidence coupling PLK1 activity to tumor development, progression, and therapy resistance. PLK1 is overexpressed in various cancers, and its expression levels correlate with poor prognosis. During cell division, the most prominent network or chestrating mitotic onset consists of the PLK1-Aurora A-Cyclin B1/CDK1 feedback loop. In this respect, PLK1 activity is reported to be a critical prerequisite for mitotic entry.