Abstract
Monoamine oxidases (MAOs) are a crucial pair of isoenzymes responsible for degrading monoamine neurotransmitters and dietary amines. In addition to extensive studies of their roles in the context of brain functions and disorders over decades, emerging evidence indicates that MAOs are also often dysregulated and associated with clinical outcomes in diverse cancers, with the ability to differentially regulate cancer growth, invasion, metastasis, progression, and therapy response depending on the cancer type. In this review, we summarize recent advances in understanding the clinical relevance, functional importance, and mechanisms of MAOs in a broad range of cancers, and discuss the application and therapeutic benefit of MAO inhibitors (MAOIs) for cancer treatment, highlighting the roles of MAOs as novel regulators, prognostic biomarkers, and therapeutic targets in cancer.