MICA and breast cancer: Suppression of NKG2D on primary human NK cells or downregulation of MICA or ULBP2 with siRNA mimicked the effect of miR-519a-3p and reduced NK cell activation as well as cytotoxicity that is in line with previous studies on NKG2D function.59, 67, 68, 72 In addition, low levels of MICA/B and ULBPs correlate with poor clinical outcome in breast cancer patients.36 Besides NK cells, NKG2D is also expressed on the cell surface of human CD8+ T cells and transmits a costimulatory signal.74 Future research will be required to unravel the effect of miR-519a-3p on CD8+ T-cell activation via NKG2D.