PO.TB04.02 · 肿瘤生物学
ImmunoPET揭示人源化MDA-MB-231模型中的肿瘤相关巨噬细胞
ImmunoPET reveals tumor-associated macrophages in humanized MDA-MB-231 models
该海报暂无可下载的资料
AACR 官方页面
作者与单位 Authors & Affiliations
摘要 Abstract
中文摘要
背景：肿瘤相关巨噬细胞（TAMs）是肿瘤免疫微环境的主要组成部分，与肿瘤进展和治疗耐药相关。TAMs的无创检测可为免疫浸润提供有价值的见解并指导免疫治疗开发。然而，目前的巨噬细胞成像试剂缺乏对人类泛巨噬细胞的特异性。在本研究中，我们旨在使用我们特异性的巨噬细胞靶向探针在人源化小鼠模型中对人巨噬细胞进行成像。
方法：我们开发了一种人特异性CD68-Fab片段（Fab14），并用锆-89对其进行放射性标记，以获得[89Zr]Zr-DFO-Fab14。将MDA-MB-231三阴性乳腺癌细胞植入人源化NSG-SGM3小鼠和对照NSG-SGM3小鼠的乳腺脂肪垫。当肿瘤可触及时，给小鼠静脉注射6.25 μg人特异性、巨噬细胞选择性的[89Zr]Zr-DFO-Fab14（每只小鼠约30 μCi）。在注射后（p.i.）2、24和48小时进行PET成像，并使用SUVmean对放射性示踪剂摄取进行定量。在48小时通过伽马计数评估离体生物分布，以评价放射性示踪剂的特异性和滞留。收集肿瘤进行人CD68表达的免疫荧光（IF）分析。
结果：在注射后2小时，[89Zr]Zr-DFO-Fab14摄取的定量分析在人源化和对照肿瘤中相似，表明早期分布相当。到24小时，免疫PET示踪剂的摄取在人源化NSG-SGM3小鼠中显著更高且更持久（SUVmean = 0.29 ± 0.04），相比对照小鼠（SUVmean = 0.20 ± 0.03；***p = 0.0002）。48小时的生物分布研究进一步验证了成像特异性，显示人源化NSG-SGM3中的肿瘤滞留（4.66 ± 1.61 %ID/g）明显高于对照NSG-SGM3小鼠（1.71 ± 0.63 %ID/g）。IF分析确认了人源化NSG-SGM3肿瘤中丰富的人CD68⁺巨噬细胞浸润，而NSG-SGM3肿瘤中则没有，证实了[89Zr]Zr-DFO-Fab14对人巨噬细胞的特异性。
结论：人特异性[89Zr]Zr-DFO-Fab14在人源化肿瘤中表现出巨噬细胞特异性滞留，能够在体内对人TAMs进行无创可视化。该放射性示踪剂代表了一种有前景的工具，可用于研究人类免疫重建系统中的巨噬细胞动态并评估癌症中巨噬细胞靶向治疗的疗效。
查看英文原文 English abstract
Background: Tumor-associated macrophages (TAMs) represent a major component of the tumor immune microenvironment and are associated with tumor progression and therapeutic resistance. Noninvasive detection of TAMs can provide valuable insight into immune infiltration and guide immunotherapy development. However, current macrophage imaging agents lack specificity for human pan-macrophages. In this study, we aim to image human macrophages in a humanized mouse model using our specific macrophage-targeted probe.
Methods: We developed a human-specific CD68-Fab fragment (Fab14) and radiolabeled it with zirconium-89 to obtain [ 89 Zr]Zr-DFO-Fab14. Humanized NSG-SGM3 and control NSG-SGM3 mice were implanted with MDA-MB-231 triple-negative breast cancer cells into the mammary fat pad. When tumors were palpable, mice were injected intravenously with 6.25 µg of human-specific, macrophage-selective [ 89 Zr]Zr-DFO-Fab14 (~30 µCi per mouse). PET imaging was performed at 2-, 24- and 48-hours post-injection (p.i.), and radiotracer uptake was quantified using SUVmean. Ex vivo biodistribution at 48 hours was assessed by gamma counting to evaluate radiotracer specificity and retention. Tumors were harvested for immunofluorescence (IF) analysis of human CD68 expression.
Results: At 2 hours p.i., quantitative analysis of [ 89 Zr]Zr-DFO-Fab14 uptake was similar in both humanized and control tumors, indicating comparable early distribution. By 24 hours, uptake of the immunoPET tracer was significantly higher and more sustained in humanized NSG-SGM3 mice (SUVmean = 0.29 ± 0.04) compared to control mice (SUVmean = 0.20 ± 0.03; ***p =0.0002). Biodistribution studies at 48 hours further validated the imaging specificity, showing markedly higher tumor retention in humanized NSG-SGM3 (4.66± 1.61 %ID/g) than in control NSG-SGM3 mice (1.71 ± 0.63 %ID/g). IF analysis confirmed abundant human CD68⁺ macrophage infiltration in humanized NSG-SGM3 tumors but not in NSG-SGM3 tumors, confirming the specificity of [ 89 Zr]Zr-DFO-Fab14 for human macrophages.
Conclusions: The human-specific [ 89 Zr]Zr-DFO-Fab14 demonstrates macrophage-specific retention in humanized tumors, enabling noninvasive visualization of human TAMs in vivo. This radiotracer represents a promising tool for studying macrophage dynamics in human immune-reconstituted systems and evaluating efficacy of macrophage-targeted therapies in cancer.
利益披露 Disclosure
P. Lee, None..
A. Vaughn Embs, None..
C. Mallard, None..
J. Mallard, None.