Author: Schneider, Marcel Andre; Heeb, Laura; Beffinger, Michal Mateusz; Pantelyushin, Stanislav; Linecker, Michael; Roth, Lilian; Lehmann, Kuno; Ungethum, Udo; Kobold, Sebastian; Graf, Rolf; van den Broek, Maries; Vom Berg, Johannes; Gupta, Anurag; Clavien, Pierre-Alain
Description: Platelet-derived peripheral serotonin has pleiotropic effects on coagulation, metabolism, tissue regeneration, and cancer growth; however, the effect of serotonin on the tumor microenvironment remains understudied. Peripheral serotonin–deficient (Tph1−/−) mice displayed reduced growth of subcutaneous and orthotopically injected syngeneic murine pancreatic and colorectal cancers with enhanced accumulation of functional CD8+ T cells compared to control C57BL/6 mice, resulting in extended overall survival. Subcutaneous and orthotopic syngeneic tumors from Tph1−/− mice expressed less programmed cell death 1 ligand 1 (PD-L1), suggesting serotonin-mediated regulation. Serotonin enhanced expression of PD-L1 on mouse and human cancer cells in vitro via serotonylation, which is the formation of covalent bonds between glutamine residues and serotonin, resulting in activation of small G proteins. Serotonin concentrations in metastases of patients with abdominal tumors negatively correlated to the number of CD8+ tumor-infiltrating T cells. Depletion of serotonin cargo or inhibition of serotonin release from thrombocytes decreased growth of syngeneic pancreatic and colorectal tumors in wild-type mice, increased CD8+ T cell influx, and decreased PD-L1 expression. Pharmacological serotonin depletion with oral fluoxetine or intraperitoneal injection of the TPH1 inhibitor telotristat augmented the effects of programmed cell death protein 1 (PD-1) checkpoint blockade and triggered long-term tumor control in mice subcutaneously inoculated with syngeneic colorectal and pancreatic tumors. Overall, peripheral serotonin weakens effector functions of CD8+ T cells within tumors. Clinically approved serotonin targeting agents alone or in combination with PD-1 blockade provided long-term control of established tumors in murine models, warranting further investigation of the clinical translatability of these findings.
Subject headings: Serotonin; Pancreatic cancer; Colorectal cancer; Tumors; Fluoxetine; Telotristat; Mice; Immunotherapy; Therapy
Publication year: 2021
Journal or book title: Science Translational Medicine
Volume: 13
Issue: 611
Pages: eabc8188
Find the full text: https://www.science.org/doi/abs/10.1126/scitranslmed.abc8188
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Serial number: 3498