NORAD and esophageal squamous cell carcinoma: To investigate whether NORAD could sponge miR-224-3p in ESCC cells, we constructed luciferase reporters harbouring NORAD with mutations in predicted sites #1 and #2 (i.e., NORAD-Mut#1 and NORAD-Mut#2) for binding to miR-224-3p (Additional file 2: Fig. S6a-b).