SynNotch-Programmed Macrophages for Cancerous Cell\nDetection and Sensing

Synthetic\nNotch (synNotch) receptors have enabled mammalian cells\nto sense extracellular ligands and respond by activating user-prescribed\ntranscriptional programs. Based on the synNotch system, we describe\na cell-based in vivo sensor for cancerous cell detection. We attempted\nto engineer synNotch-programmed macrophages to sense cancer cells\nvia urinary analysis of human chorionic gonadotropin (HCGB5). Principally,\nwhen the synNotch receptors of macrophages bind to the ligands of\ncancer cells, Notch is activated and undergoes intramembrane proteolysis\nto release the transcriptional activator into the nucleus. The transcriptional\nactivator targets and activates downstream gene expression, such as\nhuman chorionic gonadotropin (HCGB5) in macrophages. When HCGB5 is\nsecreted extracellularly into urine, it can be detected with commercial\nHCGB5 colloidal gold test strips. As a proof of principle, we demonstrated\nthe feasibility of synNotch-programmed macrophages in detecting breast\ncancer cells engineered with artificial EGFP ligands. We demonstrated\nthat HCGB5 expression was only induced when the cancer cell expressing\nEGFP ligands is present; thereby, extracellular HCGB5 expression is\ndirectly proportional to the number of cancer cells. Further optimizations\nof the synNotch system can realize the ultimate goal of establishing\ncell-based in vivo sensors as the paragon of cancer diagnostics for\npoint-of-care testing and home self-test.