5‐HT suppresses the induction of MAO‐A expression; promotes cancer cell proliferation and migration by activating downstream molecules, such as p21, matrix metalloproteinases 2 (MMP2), and vascular endothelial growth factor (VEGF); and promotes epithelial‐to‐mesenchymal transition (EMT) and hypoxia inducible factor‐1 (HIF1) α protein accumulation [367, 368]. Here, MMP2 is linked to cancer.