Monoamine oxidase A(MAOA)is a membrane-bound mitochondrial enzyme that exists in almost all vertebrate tissues,where it catalyzes the degradation of biogenic and dietary-derived monoamines.MAOA has the function of regulating neurotransmitter metabolism and is associated with anti-tumor immune responses.Most previous studies have focused on the role of MAOA in tumor cells,while more recent findings suggest that MAOA plays an equally significant role in tumor-associated immune cells.In this review,we summarize the regulatory effect of MAOA on the inhibitory tumor microenvironment.The suppressing function of MAOA on various types of tumor-associated immune cells(e.g.,CD8+T cells and tumor-associated macrophages)by its direct effect on monoamines and their metabolic characteristics are discussed.We propose that developing novel MAOA-inhibitor drugs and exploring multidrug-combination strategies may enhance the efficacy of immune therapy for tumors.In conclusion,MAOA may act as a novel target in tumor immunity and influence the effect of tumor immunotherapy.

Monoamine oxidase A(MAOA)is a mitochondrial enzyme that catalyzes the oxidative deamination of monoamine neurotransmitters and dietary amines.It plays a crucial role in the pathogenesis,progress,and treatment of neuropsychiatric disorders.Recent studies have revealed that elevated expression of MAOA in prostate cancer(PCa)is closely associated with tumor progression and drives the heterogeneity of PCa.In this review,we summarize the role of MAOA in the development of PCa in different disease stages,including oncogenesis,development,invasion,metastasis,and drug resistance.We also discuss the involvement of MAOA in the tumor microenvironment and explore the potential utility of MAOA inhibitors.We further propose therapeutic strategies based on targeting MAOA in preclinical models to promote relevant clinical trials.This review aims to provide new potential therapeutic targets for the treatment of PCa.