PTTG1 and esophageal squamous cell carcinoma: The expression of PTTG1 was negatively correlated with the age of ESCC patients (r = −0.3097, P = 0.004), and the expression of PTTG1 in young patients was higher (11.8 ± 0.7 vs. 11.3 ± 0.6, P = 0.004) (Supplementary Table 3).