NAIP and esophageal squamous cell carcinoma: We found that c-IAP1 (Birc2), XIAP (Birc4), Survivin (Birc5) and Livin (Birc7) were overexpressed in ESCC tissues, while NAIP (Birc1) and c-IAP2 (Birc3) were comparable between tumor tissues and adjacent non-tumor tissues (Supplementary Fig. 2).