According to the median expression values of PTK2 and TIMP1, ESCC patients were classified into subtype I: PTK2 high + TIMP1 high ; subtype II: PTK2high + TIMP1 low ; subtype III: PTK2 low + TIMP1high ; subtype IV: PTK2low + TIMP1 low We observed significant OS differences among the four subtypes (Figure 5C). Here, PTK2 is linked to esophageal squamous cell carcinoma.