IDO1 and colorectal cancer: From a pathological standpoint, specifically from a cancer perspective, IDO1 is known to be significantly up-regulated in various cancer types like the ovarian cancer, malignant melanoma, pediatric and adult acute myelogenous leukemia, colorectal cancer, prostate cancer, endometrial cancer as well as in pancreatic cancer and is known to affect the overall patient survival [7–17].