ALDH5A1 and neoplasm: Then, HIF-1 polarized macrophages to the M2 phenotype, which secreted tumor-promoting factors (e.g., IL-6) and promoted tumor growth and metastasis.[47]ALDH5A1 had been detected as over-expressed in several other tumor tissues,[48,49] and some studies had also confirmed that the ALDH gene family was over-expressed in COAD stem cells and then initiated COAD tumorigenesis.[45] Increased concentrations of succinic acid were found in a variety of tumors, including COAD.[50,51] These previous studies further confirmed the reliability of the mechanism proposed in this study.