Seven studies compared the expression level of HDAC1 between gastrointestinal cancer tissues and noncancerous tissues, including 1 study concerning colorectal, gastric and esophageal cancer, 3 studies concerning only colorectal cancer, 1 study concerning only gastric cancer, 1 study concerning only liver cancer and 1 study concerning only pancreatic cancer. Here, HDAC1 is linked to colorectal cancer.