This evidence arose from studies of prognostic value of non-classical HLA class I molecule expression in BC patients which showed that in tumors devoid of classical HLA class I expression, HLA-E and HLA-G expression were of statistically significant influence on outcome of BC patients independently of known clinicopathological parameters, with an almost three-times higher risk of relapse over time for patients with expression of HLA-E/G compared with patients with no expression of HLA-E/G (De Kruijf et al., 2010). Here, HLA-E is linked to breast cancer.