DKK1 and gastric cancer: Another 2nd generation NKG2D-CAR-T cells with Dickkopf WNT Signaling Pathway Inhibitor 1 (DKK1) inhibition on gastric cancers showed the reversal of the suppressive tumor immune environment, increased NKG2DL expression, and significantly enhanced the immune-activating and tumor-killing capabilities of NKG2D-CAR-T cells in vitro and in vivo (41).