CHEK1 and gastric cancer: We also demonstrated that T-DXd-triggered mRNA expression of CXCL9/10/11 was significantly attenuated by an ATM inhibitor (KU), but not ATR inhibitor (VE) and chk1 inhibitor (UCN) in HER2-positive GC cells (Fig. 4C), suggesting that T-DXd increased mRNA expression of CXCL9/10/11 through the activation of ATM- but not ATR/chk1-mediated DNA damage signaling pathway in HER2-positive GC cells.