Overexpressed tumor-associated antigens [for example, epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2)] are attractive targets for therapeutic T cells, but toxic “off-tumor” cross-reaction with normal tissues that express low levels of target antigen can occur with chimeric antigen receptor (CAR)–T cells. Inspired by natural ultrasensitive response circuits, we engineered a two-step positive-feedback circuit that allows human cytotoxic T cells to discriminate targets on the basis of a sigmoidal antigen-density threshold. In this circuit, a low-affinity synthetic Notch receptor for HER2 controls the expression of a high-affinity CAR for HER2. Increasing HER2 density thus has cooperative effects on T cells—it increases both CAR expression and activation—leading to a sigmoidal response. T cells with this circuit show sharp discrimination between target cells expressing normal amounts of HER2 and cancer cells expressing 100 times as much HER2, both in vitro and in vivo.

过度表达的肿瘤相关抗原 [例如表皮生长因子受体 (EGFR) 和人表皮生长因子受体 2 (HER2)] 是治疗性 T 细胞的有吸引力的靶点，但与正常组织发生有毒的“肿瘤外”交叉反应嵌合抗原受体 (CAR)-T 细胞可能会出现低水平的靶抗原。受天然超灵敏反应电路的启发，我们设计了一个两步正反馈电路，使人类细胞毒性 T 细胞能够根据 S 形抗原密度阈值来区分目标。在该电路中，HER2 的低亲和力合成 Notch 受体控制 HER2 的高亲和力 CAR 的表达。因此，增加 HER2 密度对 T 细胞具有协同作用，它会增加 CAR 表达和激活，从而导致 S 形反应。无论在体外还是体内，具有该电路的 T 细胞都能清晰地区分表达正常量 HER2 的靶细胞和表达 100 倍 HER2 的癌细胞。