CHEK1 and gastric cancer: In addition, the phosphorylation of CHK1 can upregulate the expression of the CIP2A/p90 gene through phosphorylation of serine 345 of CHK1 via DNA damage response kinases (DNA-PK) in human gastric cancer, ovarian cancer, colon cancer, and neuroblastoma (Khanna et al., 2013; Khanna et al., 2020).