Behnam Azad Babak, Lisok Ala, Chatterjee Samit, Poirier John T, Pullambhatla Mrudula, Luker Gary D, Pomper Martin G, Nimmagadda Sridhar
Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, Maryland.
Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, New York.
J Nucl Med. 2016 Jun;57(6):981-8. doi: 10.2967/jnumed.115.167932. Epub 2016 Feb 23.
The atypical chemokine receptor ACKR3 (formerly CXCR7), overexpressed in various cancers compared with normal tissues, plays a pivotal role in adhesion, angiogenesis, tumorigenesis, metastasis, and tumor cell survival. ACKR3 modulates the tumor microenvironment and regulates tumor growth. The therapeutic potential of ACKR3 has also been demonstrated in various murine models of human cancer. Literature findings underscore the importance of ACKR3 in disease progression and suggest it as an important diagnostic marker for noninvasive imaging of ACKR3-overexpressing malignancies. There are currently no reports on direct receptor-specific detection of ACKR3 expression. Here we report the evaluation of a radiolabeled ACKR3-targeted monoclonal antibody (ACKR3-mAb) for the noninvasive in vivo nuclear imaging of ACKR3 expression in human breast, lung, and esophageal squamous cell carcinoma cancer xenografts.
ACKR3 expression data were extracted from Cancer Cell Line Encyclopedia, The Cancer Genome Atlas, and the Clinical Lung Cancer Genome Project. (89)Zr-ACKR3-mAb was evaluated in vitro and subsequently in vivo by PET and ex vivo biodistribution studies in mice xenografted with breast (MDA-MB-231-ACKR3 [231-ACKR3], MDA-MB-231 [231], MCF7), lung (HCC95), or esophageal (KYSE520) cancer cells. In addition, ACKR3-mAb was radiolabeled with (125)I and evaluated by SPECT imaging and ex vivo biodistribution studies.
ACKR3 transcript levels were highest in lung squamous cell carcinoma among the 21 cancer type data extracted from The Cancer Genome Atlas. Also, Clinical Lung Cancer Genome Project data showed that lung squamous cell carcinoma had the highest CXCR7 transcript levels compared with other lung cancer subtypes. The (89)Zr-ACKR3-mAb was produced in 80% ± 5% radiochemical yields with greater than 98% radiochemical purity. In vitro cell uptake of (89)Zr-ACKR3-mAb correlated with gradient levels of cell surface ACKR3 expression observed by flow cytometry. In vivo PET imaging and ex vivo biodistribution studies in mice with breast, lung, and esophageal cancer xenografts consistently showed enhanced (89)Zr-ACKR3-mAb uptake in high-ACKR3-expressing tumors. SPECT imaging of (125)I-ACKR3-mAb showed the versatility of ACKR3-mAb for in vivo monitoring of ACKR3 expression.
Data from this study suggest ACKR3 to be a viable diagnostic marker and demonstrate the utility of radiolabeled ACKR3-mAb for in vivo visualization of ACKR3-overexpressing malignancies.
非典型趋化因子受体ACKR3（原CXCR7），与正常组织相比在多种癌症中过表达，在黏附、血管生成、肿瘤发生、转移及肿瘤细胞存活中起关键作用。ACKR3调节肿瘤微环境并调控肿瘤生长。ACKR3的治疗潜力也已在多种人类癌症的小鼠模型中得到证实。文献研究结果强调了ACKR3在疾病进展中的重要性，并表明其可作为过表达ACKR3的恶性肿瘤非侵入性成像的重要诊断标志物。目前尚无关于直接受体特异性检测ACKR3表达的报道。在此，我们报告了一种放射性标记的靶向ACKR3的单克隆抗体（ACKR3 - mAb）用于人乳腺癌、肺癌和食管鳞状细胞癌异种移植瘤中ACKR3表达的体内非侵入性核成像评估。
从癌症细胞系百科全书、癌症基因组图谱和临床肺癌基因组计划中提取ACKR3表达数据。通过PET在体外及随后在体内对89Zr - ACKR3 - mAb进行评估，并通过对移植有乳腺癌（MDA - MB - 231 - ACKR3 [231 - ACKR3]、MDA - MB - 231 [231]、MCF7）、肺癌（HCC95）或食管癌（KYSE520）细胞的小鼠进行离体生物分布研究。此外，用125I对ACKR3 - mAb进行放射性标记，并通过SPECT成像和离体生物分布研究进行评估。
在从癌症基因组图谱提取的21种癌症类型数据中，肺鳞状细胞癌中ACKR3转录水平最高。临床肺癌基因组计划数据也显示，与其他肺癌亚型相比，肺鳞状细胞癌具有最高的CXCR7转录水平。89Zr - ACKR3 - mAb的放射化学产率为80%±5%，放射化学纯度大于98%。体外细胞对89Zr - ACKR3 - mAb的摄取与通过流式细胞术观察到的细胞表面ACKR3表达梯度水平相关。对移植有乳腺癌、肺癌和食管癌异种移植瘤的小鼠进行的体内PET成像和离体生物分布研究一致显示，高表达ACKR3的肿瘤对89Zr - ACKR3 - mAb的摄取增加。125I - ACKR3 - mAb的SPECT成像显示了ACKR3 - mAb在体内监测ACKR3表达方面的通用性。
本研究数据表明ACKR3是一种可行的诊断标志物，并证明了放射性标记的ACKR3 - mAb在体内可视化过表达ACKR3的恶性肿瘤方面的实用性。
