Department of Medical Oncology and Hematology, University Hospital Zürich (USZ) and University of Zürich (UZH), Comprehensive Cancer Center, Zürich, Switzerland.
Department of Chemistry, Philochem AG, Otelfingen, Switzerland.
Oncoimmunology. 2024 Oct 3;13(1):2412371. doi: 10.1080/2162402X.2024.2412371. eCollection 2024.
Somatostatin receptor type 2 (SSTR2) is one of the five subtypes of somatostatin receptors and is overexpressed on the surface of most gastro-entero-pancreatic neuroendocrine tumors (GEP-NETs), pituitary tumors, paraganglioma, and meningioma, as well as hepatocellular carcinoma and breast cancer. Chimeric antigen receptor (CAR) T-cells are genetically engineered to express an artificial, T-cell activating binder, leading upon ligation to biocidal activity against target-antigen expressing cells. Adaptor-CAR T-cells recognize, via the CAR, a tag on an antigen-binding molecule, building an activating bridge between the CAR and the target cell. We hypothesized that a novel fluorescent-peptide antagonist of SSTR2, called Octo-Fluo, in combination with anti-FITC adaptor CAR (AdFITC(E2)-CAR) T-cells, may function as an on-off tunable activating bridge between the CAR and SSTR2 expressing target cells. In vitro studies confirmed the binding of Octo-Fluo to Bon1-SSTR2 mCherry-Luc cells without evidence of internalization. AdFITC(E2)-CAR T-cells were activated and efficiently induced Bon1-SSTR2 cell death in vitro, in an Octo-Fluo concentration-dependent manner. Similarly, AdFITC(E2)-CAR T-cells in combination with Octo-Fluo efficiently infiltrated the tumor and eliminated Bon1-SSTR2 tumors in immunodeficient mice in therapeutic settings. Both, AdFITC(E2)-CAR T-cell tumor infiltration and biocidal activity were Octo-Fluo concentration-dependent, with high doses of Octo-Fluo, saturating both the CAR and the SSTR2 antigen independently, leading to the loss of tumor infiltration and biocidal activity due to the loss of bridge formation. Our findings demonstrate the potential of using AdFITC(E2)-CAR T-cells with Octo-Fluo as a versatile, on-off tunable bispecific adaptor for targeted CAR T-cell immunotherapy against SSTR2-positive NETs.
生长抑素受体 2 型（SSTR2）是生长抑素受体的五种亚型之一，在大多数胃肠胰神经内分泌肿瘤（GEP-NET）、垂体肿瘤、副神经节瘤和脑膜瘤、以及肝细胞癌和乳腺癌的表面过度表达。嵌合抗原受体（CAR）T 细胞经过基因工程改造，表达一种人工的、T 细胞激活结合物，在与靶抗原表达细胞的连接后，引发针对靶抗原表达细胞的细胞毒性活性。衔接子-CAR T 细胞通过 CAR 识别抗原结合分子上的标签，在 CAR 和靶细胞之间建立激活桥。我们假设，一种新型的 SSTR2 荧光肽拮抗剂，称为 Octo-Fluo，与抗-FITC 衔接子 CAR（AdFITC(E2)-CAR）T 细胞联合使用，可能作为 CAR 和表达 SSTR2 的靶细胞之间的可开启和关闭的可调激活桥。体外研究证实，Octo-Fluo 与 Bon1-SSTR2 mCherry-Luc 细胞结合，没有内化的证据。AdFITC(E2)-CAR T 细胞在体外被激活，并以 Octo-Fluo 浓度依赖性的方式有效地诱导 Bon1-SSTR2 细胞死亡。同样，AdFITC(E2)-CAR T 细胞与 Octo-Fluo 联合使用，在免疫缺陷小鼠的治疗环境中，有效地渗透肿瘤并消除 Bon1-SSTR2 肿瘤。AdFITC(E2)-CAR T 细胞的肿瘤浸润和细胞毒性活性都依赖于 Octo-Fluo 的浓度，高剂量的 Octo-Fluo 可独立地饱和 CAR 和 SSTR2 抗原，导致由于桥接形成的丢失，肿瘤浸润和细胞毒性活性丧失。我们的研究结果表明，使用 AdFITC(E2)-CAR T 细胞与 Octo-Fluo 作为一种多功能的、可开启和关闭的可调双特异性衔接子，用于针对 SSTR2 阳性 NET 的靶向 CAR T 细胞免疫治疗具有潜力。
