[[Monoamine Oxidase]] A (MAO A) oxidizes monoamine neurotransmitters resulting in reactive oxygen species which cause cancer. 

A study shows that MAO A expression is increased in human glioma tissues and cell lines. MAO A inhibitors, clorgyline or the near-infrared-dye MHI-148 conjugated to clorgyline (NMI), were cytotoxic for glioma and decreased invasion in vitro. Using the intracranial TMZ-resistant glioma model, clorgyline or NMI alone or in combination with low-dose TMZ reduced tumor growth and increased animal survival. NMI was localized specifically to the tumor. Immunocytochemistry studies showed that the MAO A inhibitor reduced proliferation, microvessel density and invasion, and increased macrophage infiltration. In conclusion, we have identified MAO A inhibitors as potential novel stand-alone drugs or as combination therapy with low dose TMZ for drug-resistant gliomas. NMI can also be used as a non-invasive imaging tool. Thus has a dual function for both therapy and diagnosis
((Kushal S, Wang W, Vaikari VP, Kota R, Chen K, Yeh TS, Jhaveri N, Groshen SL,
Olenyuk BZ, Chen TC, Hofman FM, Shih JC. Monoamine oxidase A (MAO A) inhibitors
decrease glioma progression. Oncotarget. 2016 Mar 22;7(12):13842-53. doi:
10.18632/oncotarget.7283. PubMed PMID: 26871599; PubMed Central PMCID:
PMC4924682.
)).