PLK1 and cancer: In addition, recent genome-wide studies have revealed that Plk1 and a number of other mitotically important regulators, such as the anaphase-promoting complex/cyclosomes and the proteasome, are required for the viability of activated RAS or inactivated TP53 mutation-bearing cancer cells, but not for the respective normal cells (Luo et al. 2009a; Sur et al. 2009).