Mita et al. demonstrated in CD69–/– mice using 4T1-luc2 murine breast cancer models, a significant reduction in tumour growth and metastasis, increased levels of tumour-infiltrating lymphocytes and a significant reduction in T cell exhaustion and enhanced IFN-γ production compared with wild-type controls (Blackburn et al. 2009). Here, CD69 is linked to breast cancer.