NOS2 and neoplasm: Compared to normal tissues, the expression of TFAP2C, SLC39A8, NOS2, HAMP, GDF15, FDFT1, CDKN2A, and ALOX12 was significantly upregulated, while the expression of AKR1C1 and ATP6V1G2 was downregulated in CRC tumor tissues in the TCGA training group (P < 0.05, Figure 13A).