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). Here, HOXD9 is linked to cancer.