TTK and ovarian cancer: ES-2 and HEY ovarian cancer cells are characterized by hyper-activating mutations in the B-Raf oncogene [39]; constitutively active B-Raf (V600E) interacts with, stabilizes and hyper-activates Mps1 in melanoma cells [62]; thus, ES-2 and HEY cells may be particularly sensitive to Mps1-mediated regulation of Smad3.