SynNotch-Programmed Macrophages for Cancerous Cell Detection and Sensing.

Synthetic Notch (synNotch) receptors have enabled mammalian cells to sense extracellular ligands and respond by activating user-prescribed transcriptional programs. Based on the synNotch system, we describe a cell-based in vivo sensor for cancerous cell detection. We attempted to engineer synNotch-programmed macrophages to sense cancer cells via urinary analysis of human chorionic gonadotropin (HCGB5). Principally, when the synNotch receptors of macrophages bind to the ligands of cancer cells, Notch is activated and undergoes intramembrane proteolysis to release the transcriptional activator into the nucleus. The transcriptional activator targets and activates downstream gene expression, such as human chorionic gonadotropin (HCGB5) in macrophages. When HCGB5 is secreted extracellularly into urine, it can be detected with commercial HCGB5 colloidal gold test strips. As a proof of principle, we demonstrated the feasibility of synNotch-programmed macrophages in detecting breast cancer cells engineered with artificial EGFP ligands. We demonstrated that HCGB5 expression was only induced when the cancer cell expressing EGFP ligands is present; thereby, extracellular HCGB5 expression is directly proportional to the number of cancer cells. Further optimizations of the synNotch system can realize the ultimate goal of establishing cell-based in vivo sensors as the paragon of cancer diagnostics for point-of-care testing and home self-test.