From synthetic biology to human therapy: engineered mammalian cells

•Engineered receptors reroute tumor antigens to therapeutic responses.•Translating soluble markers of the tumor microenvironment into immunostimulatory cell behavior.•Targeting infectious diseases by pathogen sensing cell implants.•Establishing novel cell types for more effective cell therapy. Mammalian synthetic biology has evolved to become a key driver of biomedical innovation in the area of cell therapy. Advances in receptor engineering, immunotherapy and cell implants promise new treatment options for complex diseases. Synthetic receptors have already found applications in cellular immunotherapy for cancer treatment, and are being introduced into the field of cell implants. Here, we discuss prospects for the next generation of engineered mammalian cells for human therapy, highlighting selected recent studies.