THAP9 and esophageal squamous cell carcinoma: LncRNA THAP domain containing 9 antisense RNA 1 (THAP9-AS1), which is an antisense transcript of THAP9 and locates at chromosome 4q21.22, has been reported to act a key role in the tumorigenesis of gastric cancer (72) and esophageal squamous cell carcinoma (73, 74).