BST2 and esophageal squamous cell carcinoma: Based on AKR1C3 and BST2 expression, all samples of TCGA-ESCC were classified into three subgroups (Figure 7A): AKR1C3 high expression (corresponding to cluster B), AKR1C3 low and BST2 high expression (corresponding to cluster C) and both genes low expression (corresponding to cluster A) groups.