Then we detected the phosphorylated forms of ATM and CHK2 in five pairs of tissues, and the results showed that the phosphorylaion of ATM and CHK2 is increased in tumor tissues (Figure 5A), suggesting that the DNA damage events may actually occur in ESCC tissues, which can activate the ATM-CHK2 pathway and prevent tumor cells from growing too quickly. Here, ATM is linked to esophageal squamous cell carcinoma.