In the firebrowse database (http://firebrowse.org/), HOXD9 is upregulated in gastric (STAD), stomach and esophageal (STES), thyroid (THCA), bladder urothelial (BLCA), bile duct (CHOL), esophageal (ESCA), head and neck (HNSC), hepatocellular (LIHC), lung adenocarcinoma (LUAD) and lung squamous (LUSC) cancer tissues compared with that in corresponding normal tissues (Additional file 2: Figure S1). This evidence concerns the gene HOXD9 and lung adenocarcinoma.