KLRK1 and squamous cell carcinoma: Illustrating this, the sustained transgenic expression of an NKG2DL in vivo in a mouse model led to widespread NKG2D downregulation [138], reduced NK cell cytotoxicity mediated via NKG2D [139] and alternative receptor systems [140], sustained NK cell IFN-γ production [139] and enhanced susceptibility to chemically induced squamous cell carcinoma formation [138].