PTK2 and esophageal squamous cell carcinoma: Univariate Cox regression analysis showed that PTK2 hazard ratio (HR) was 1.483 (95% confidence interval [CI]: 1.018-2.161) and TIMP1 HR was 1.340 (95% CI: 1.067-1.682), which were risk factors for OS in ESCC patients (Figure 5A).