Recent advances in biomolecular engineering have led to novel cancer immunotherapies with sophisticated programmed functions, including chimeric antigen receptor (CAR) T cells that bind tumor-associated antigens (TAA) to direct coordinated immune responses. Extensive engineering efforts have been made to program not only CAR specificity, but also downstream pathways that activate molecular responses. Collectively, these efforts can be conceptualized as an immunotherapy circuit: TAAs bind the CAR as input signals; intracellular signaling cascades process the binding interactions into transcriptional and translational events; and those events program effector output functions. More simply, this sequence may be abstracted as input, processing, and output. In this review, we discuss the increasingly complex scene of synthetic-biology solutions in cancer immunotherapy and summarize recent work within the framework of immunotherapy circuits. In doing so, a toolbox of basic modular circuits may be established as a foundation upon which sophisticated solutions can be constructed to meet more complex problems.

See related article on p. 5.