Abstract: The role of 5-hydroxytryptamine (5-HT) has attracted more and more attention in the development of tumor. In addition to the synthesis of 5-HT by enterochromaffin cells, some tumor cells and immune cells can also secrete 5-HT, and there are different 5-HT receptors on the surface of these cells. 5-HT plays multiple biological effects through activating different receptors. 5-HT promotes the proliferation and invasion of tumor and induces the angiogenesis of tumor tissues through activating its corresponding receptors, such as 5-HT1D, and so on. Furthermore, various 5-HT receptors are expressed on the surface of immune cells. On the one hand, physiological doses of 5-HT promote the proliferation and secretion of immune cells. On the other hand, pathologic 5-HT has an effect on inducing the differentiation of immune cells in the direction of immunosuppression, thus participating in the occurrence and development of tumor.

Key words: Serotonin, Receptors, Immunity, Neoplasms