A Synthetic Circuit Empowering Reprogrammed B Cells for Therapeutic Proteins Expression Regulated by Tumor Detection.

Cancer remains a leading cause of death worldwide, but immunotherapies hold promises to cure it by awaking the patient's immune system to provide long-term protection. Cell therapies, involving the infusion of immune cells, either directly or genetically modified, are being developed to recognize and destroy cancer cells. Here, we explored the potential of a new synthetic circuit to reprogram B cells to cure cancers. This circuit consists in a sensor (a membrane-anchored IgG1), a transducer (a fragment of the NR4A1 promoter) and an effector molecule. Upon recognition of its target, this sensor triggers signaling pathways leading to the activation of the transducer and to effector expression (here, a reporter molecule). We showed that this circuit could discriminate tumors expressing the target antigen from those that did not, in a dose dependent manner in vitro. Going further, we replaced the original membrane-anchored sensor by an immunoglobulin expression cassette that can not only be membrane-anchored but also be secreted depending on B-cell maturation status. This allowed concomitant activation of the circuit and secretion of transgenic antibodies directed against the targeted antigen. Of note, these antibodies could correctly bind their target and were recognized by FcR expressed at the surface of immune cells, which should synergically amplify the action of the effector. The potential of reprogrammed B cells remains to be assessed in vivo by implementing a therapeutic effector. In the future, B-cell reprogramming platforms should allow personalized cancer treatment by adapting both the sensor and the therapeutic effectors to patients.