CHEK1 and cancer: Interestingly, tetraploid cancer cells showed sensitivity to some mitotic inhibitors, essentially inhibitors of Checkpoint kinase 1 (CHK1), Aurora B, Kinesin-5 (Eg5), Polo Like Kinase 1 (Plk1) and Monopolar spindle 1 (Mps1 also named threonine tyrosine kinase TTK) [17].