Significance: Microbial neurotransmitters, as potential targets for cancer therapy, are expected to provide a new perspective on the interaction between the gut microbiome and cancer immunotherapy.

Recent Advances: Mounting data reveal that most neurotransmitters can be derived from gut microbiota. Furthermore, modulation of neurotransmitter signaling can limit tumor growth and enhance antitumor immunity.

Critical Issues: Here, we first present the relationships between microbial neurotransmitters and cancer cells mediated by immune cells. Then, we discuss the microbial neurotransmitters recently associated with cancer immunotherapy. Notably, the review emphasizes that neurotransmitter signaling plays a substantial role in cancer immunotherapy as an emerging cancer treatment target by regulating targeted receptors and interfering with the tumor microenvironment.

Future Directions: Future studies are required to uncover the antitumor mechanisms of neurotransmitter signaling to develop novel treatment strategies to overcome cancer immunotherapy resistance. Antioxid. Redox Signal. 38, 298-315.