HLA-G and breast cancer: Regarding the latter, HLA-G expression, a nonclassical MHC-I molecule frequently expressed by BC [163], can engage the KIR2DL4 receptor expressed in NK cells; this can limit trastuzumab-mediated killing in HER2+ BC, while also inducing the expression of PD-1 on the NK cells’ surface, which is a resistance mechanism that could render them susceptible to PD-L1-mediated immune suppression [149].