Department of Medical Oncology, University of Groningen and University Medical Center Groningen, Groningen, The Netherlands.
J Nucl Med. 2011 Dec;52(12):2001-8. doi: 10.2967/jnumed.111.092809. Epub 2011 Nov 9.
Transforming growth factor-β (TGF-β) promotes cancer invasion and metastasis and is therefore a potential drug target for cancer treatment. Fresolimumab, which neutralizes all mammalian active isoforms of TGF-β, was radiolabeled with (89)Zr for PET to analyze TGF-β expression, antibody tumor uptake, and organ distribution.
(89)Zr was conjugated to fresolimumab using the chelator N-succinyldesferrioxamine-B-tetrafluorphenol. (89)Zr-fresolimumab was analyzed for conjugation ratio, aggregation, radiochemical purity, stability, and immunoreactivity. (89)Zr-fresolimumab tumor uptake and organ distribution were assessed using 3 protein doses (10, 50, and 100 μg) and compared with (111)In-IgG in a human TGF-β-transfected Chinese hamster ovary xenograft model, human breast cancer MDA-MB-231 xenograft, and metastatic model. Latent and active TGF-β1 expression was analyzed in tissue homogenates with enzyme-linked immunosorbent assay.
(89)Zr was labeled to fresolimumab with high specific activity (>1 GBq/mg), high yield, and high purity. In vitro validation of (89)Zr-fresolimumab showed a fully preserved immunoreactivity and long (>1 wk) stability in solution and in human serum. In vivo validation showed an (89)Zr-fresolimumab distribution similar to IgG in most organs, except for a higher uptake in the liver in all mice and higher kidney uptake in the 10-μg group. (89)Zr-fresolimumab induced no toxicity in mice; it accumulated in primary tumors and metastases in a manner similar to IgG. Both latent and active TGF-β was detected in tumor homogenates, whereas only latent TGF-β could be detected in liver homogenates. Remarkably high (89)Zr-fresolimumab uptake was seen in sites of tumor ulceration and in scar tissue, processes in which TGF-β is known to be highly active.
Fresolimumab tumor uptake and organ distribution can be visualized and quantified with (89)Zr-fresolimumab PET. This technique will be used to guide further clinical development of fresolimumab and could possibly identify patients most likely to benefit.
转化生长因子-β（TGF-β）促进癌症侵袭和转移，因此是癌症治疗的潜在药物靶点。Fresolimumab 可中和所有哺乳动物活性 TGF-β 同工型，并用 (89)Zr 进行放射性标记以进行 PET 分析，以分析 TGF-β 表达、抗体肿瘤摄取和器官分布。
用螯合剂 N-琥珀酰亚胺基-去铁胺-B-四氟苯酚将 (89)Zr 与 fresolimumab 连接。分析了 (89)Zr-fresolimumab 的连接比、聚集、放射化学纯度、稳定性和免疫反应性。使用 3 种蛋白质剂量（10、50 和 100μg），并与 TGF-β 转染的中国仓鼠卵巢异种移植模型、人乳腺癌 MDA-MB-231 异种移植和转移性模型中的 (111)In-IgG 进行比较，评估了 (89)Zr-fresolimumab 的肿瘤摄取和器官分布。用酶联免疫吸附试验分析组织匀浆中的潜伏和活性 TGF-β1 表达。
(89)Zr 以高比活度（>1GBq/mg）、高产率和高纯度标记到 fresolimumab 上。(89)Zr-fresolimumab 的体外验证表明，其在溶液中和人血清中具有完全保留的免疫反应性和>1 周的长稳定性。体内验证表明，(89)Zr-fresolimumab 在大多数器官中的分布与 IgG 相似，除了所有小鼠的肝脏摄取更高和 10μg 组的肾脏摄取更高。(89)Zr-fresolimumab 在小鼠中无毒性；它以类似于 IgG 的方式在原发性肿瘤和转移灶中积聚。肿瘤匀浆中检测到潜伏和活性 TGF-β，而肝匀浆中仅检测到潜伏 TGF-β。在肿瘤溃疡和瘢痕组织中观察到显著高的 (89)Zr-fresolimumab 摄取，在这些过程中已知 TGF-β 高度活跃。
用 (89)Zr-fresolimumab PET 可以可视化和定量测定 fresolimumab 的肿瘤摄取和器官分布。该技术将用于指导 fresolimumab 的进一步临床开发，并可能确定最有可能受益的患者。
