Neurotransmitters and Drug Repurposing in Cancer Therapy: Targeting the Nervous System for Tumor Suppression

Emerging research indicates that the nervous system plays a complex role in cancer, with neurotransmitters regulating tumour growth, immune evasion, and resistance to therapy. It has been reported that several important oncogenic pathways are modulated by neurotransmitters, including dopamine, serotonin, norepinephrine, and glutamate, thereby governing cell proliferation, angiogenesis, and immune regulation in the tumor microenvironment. This has created new opportunities for therapeutic intervention, particularly drug-repurposing strategies that target neurotransmitter signalling. Previous reports have suggested that various neurons can promote the progression of different tumors through neuropeptide receptors, which may represent a potential drug target. Numerous FDA-approved drugs that target neurotransmitter receptors-ranging from dopamine agonists and beta-blockers to Selective Serotonin Reuptake Inhibitors (SSRIs)-have shown potential anti-cancer activity by modulating tumor-supportive neural signalling. This narrative review synthesizes current literature on the neurobiology of cancer, with an emphasis on the mechanistic roles of dopamine, serotonin, and norepinephrine/epinephrine in tumorigenesis. It further examines the repurposing of neuroactive drugs-dopamine agonists, SSRIs, tricyclic antidepressants, antipsychotics, benzodiazepines, and beta- blockers-for cancer therapy, and discusses the more limited evidence on glutamate, acetylcholine, and GABA signalling in tumor biology.