PDCD1 and colorectal cancer: The studies showed that some markers are specifically linked to particular types of cancers (such as 27‐OHC, ATF‐2, TNFRSF10B, HER2, and MET, which are linked to breast cancer; iNOS and NO, which are linked to thyroid cancer; GLUT1 and GLUT4, HIF‐1α, MCT4, PKM2, PD‐1, PD‐L1, and CTLA‐4, which are linked to colorectal cancer).