HDAC9 and gastric adenocarcinoma: To validate the prediction of circATP2B1’s tumor promoting role, we first evaluated circATP2B1 expression levels in normal gastric tissues (GT, n = 18), highly differentiated gastric adenocarcinoma specimens (HDAC, n = 17), poorly differentiated gastric adenocarcinoma specimens (PDAC, n = 15) as well as MKN45 and SGC7901 cell lines.