Engineering a PD-L1-sensing synthetic receptor for programmable macrophage-mediated phagocytosis

Macrophages are abundant immune cells within the tumor microenvironment with intrinsic phagocytic capabilities, yet their antitumor functions are frequently suppressed by inhibitory signals. Synthetic biology enables the rational design of ligand-responsive genetic circuits to reprogram immune cell behavior. Here, we report the engineering of a synthetic Notch-based receptor that detects PD-L1, an immune-checkpoint broadly expressed by cancer cells. Upon PD-L1 engagement, the circuit triggers programmable outputs, including expression of a fluorescent reporter or CV1-Fc, that locally blocks the CD47 "dont eat me" signal. We show that circuit activation scales with PD-L1 levels, partially attenuates PD-1/PD-L1 signaling, and that conditional CV1-Fc expression enhances engulfment of SKOV-3 ovarian cancer cells by THP-1-derived macrophages in vitro. Collectively, this work reframes PD-L1 from an end-point therapeutic target to a primary input signal for synthetic circuit activation and establishes a modular framework for engineering macrophage behaviour through spatially confined, ligand-responsive control. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/700810v1_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@1cbb391org.highwire.dtl.DTLVardef@7a0900org.highwire.dtl.DTLVardef@1e4f6d6org.highwire.dtl.DTLVardef@109838d_HPS_FORMAT_FIGEXP M_FIG Graphical abstract. A novel -PDL1 SNIPR receptor to program macrophage outputs. PD-L1 expressed on cancer cells is detected by -PD-L1 SNIPR-engineered macrophages, triggering release of the GAL4-VP64 transcription factor and activation of a programmable actuator. Circuit activation leads to customized outputs, including biosensing and enhanced macrophage phagocytosis via CD47 blockade, as well as immunomodulatory effects through interference with the PD-1/PD-L1 checkpoint axis. This sensor-actuator framework enables spatially confined and ligand-dependent reprogramming of macrophage function. C_FIG