NOS2 and malignant colon neoplasm: Accumulating studies show that increased NO production as a result of upregulation of iNOS or eNOS can promote the stemness phenotypes of cancer cells derived from various tumor sources or experimental models, including glioma [48, 49], liver cancer [50], colon cancer and intestinal tumors [51, 52], prostate cancer [47] and bladder cancer [53].