GDF15 and colorectal cancer: Notably, experimental and epidemiological evidence has demonstrated that GDF-15 levels are up-regulated in many types of DST, such as colorectal cancer (CRC) [8–13], gastrointestinal cancer (GC) [14, 15], pancreatic cancer (PC) [16–20], esophageal carcinoma (EC) [21, 22], and liver cancer [23, 24].