PTTG1 and esophageal squamous cell carcinoma: IHC staining of tissue chips showed that the PTTG1 protein expression level in ESCC tissues was significantly higher than in non-cancerous tissues (10.410 ± 1.880 vs. 7.410 ± 2.153, P < 0.0001; AUC = 0.8405, P < 0.0001) (Figure 1).