CD8A and breast cancer: The expression of TTK promotes cell proliferation, migration and invasion, suggesting that TTK may be an oncogene.[32,33] Inhibition of TTK expression caused chromosomal missegregation and tumor cell death, conversely, HER2-positive breast and hepatocellular carcinomas were associated with poor prognosis after overexpression of TTK.[34,35] The abnormal expression of TTK is involved in breast cancer cell cycle pathway, DNA replication pathway, and P53 signaling pathway.[36] TTK expression was also negatively correlated with T cells CD8.