Since both Plk2 and Plk3 are required for promoting cell survival (Burns et al. 2003; Xie et al. 2005) and they exhibit properties similar to tumor suppressors (Smith et al. 2006; Yang et al. 2008; Coley et al. 2012), specific inhibition of Plk1, but not Plk2 or Plk3, would be important for selectively killing cancer cells, but not normal cells. This evidence concerns the gene PLK3 and neoplasm.