Department of Pediatrics, Stanford University School of Medicine, Stanford, California.
Stanford Cancer Institute, Stanford University School of Medicine, Stanford, California.
Cancer Discov. 2020 May;10(5):702-723. doi: 10.1158/2159-8290.CD-19-0945. Epub 2020 Mar 19.
Insufficient reactivity against cells with low antigen density has emerged as an important cause of chimeric antigen receptor (CAR) T-cell resistance. Little is known about factors that modulate the threshold for antigen recognition. We demonstrate that CD19 CAR activity is dependent upon antigen density and that the CAR construct in axicabtagene ciloleucel (CD19-CD28ζ) outperforms that in tisagenlecleucel (CD19-4-1BBζ) against antigen-low tumors. Enhancing signal strength by including additional immunoreceptor tyrosine-based activation motifs (ITAM) in the CAR enables recognition of low-antigen-density cells, whereas ITAM deletions blunt signal and increase the antigen density threshold. Furthermore, replacement of the CD8 hinge-transmembrane (H/T) region of a 4-1BBζ CAR with a CD28-H/T lowers the threshold for CAR reactivity despite identical signaling molecules. CARs incorporating a CD28-H/T demonstrate a more stable and efficient immunologic synapse. Precise design of CARs can tune the threshold for antigen recognition and endow 4-1BBζ-CARs with enhanced capacity to recognize antigen-low targets while retaining a superior capacity for persistence. SIGNIFICANCE: Optimal CAR T-cell activity is dependent on antigen density, which is variable in many cancers, including lymphoma and solid tumors. CD28ζ-CARs outperform 4-1BBζ-CARs when antigen density is low. However, 4-1BBζ-CARs can be reengineered to enhance activity against low-antigen-density tumors while maintaining their unique capacity for persistence..
针对低抗原密度细胞的反应不足已成为嵌合抗原受体 (CAR) T 细胞耐药的一个重要原因。对于调节抗原识别阈值的因素知之甚少。我们证明 CD19 CAR 的活性取决于抗原密度，并且 axicabtagene ciloleucel（CD19-CD28ζ）中的 CAR 构建物比 tisagenlecleucel（CD19-4-1BBζ）更能抵抗抗原低的肿瘤。通过在 CAR 中包含额外的免疫受体酪氨酸基激活基序 (ITAM) 来增强信号强度，可实现对低抗原密度细胞的识别，而 ITAM 缺失则会削弱信号并增加抗原密度阈值。此外，用 CD28-H/T 替换 4-1BBζ CAR 的 CD8 铰链-跨膜 (H/T) 区，尽管信号分子相同，但会降低 CAR 反应的阈值。包含 CD28-H/T 的 CAR 表现出更稳定和有效的免疫突触。CAR 的精确设计可以调整抗原识别的阈值，并赋予 4-1BBζ-CAR 增强识别抗原低目标的能力，同时保留其优越的持久性能力。意义：最佳 CAR T 细胞活性取决于抗原密度，而许多癌症（包括淋巴瘤和实体瘤）中的抗原密度都是可变的。当抗原密度低时，CD28ζ-CAR 比 4-1BBζ-CAR 更有效。然而，4-1BBζ-CAR 可以被重新设计以增强对低抗原密度肿瘤的活性，同时保持其独特的持久性能力。
