Department of Radiation Oncology, Stanford University, Stanford, CA, 94305, USA.
Department of Orthopedic Surgery, Stanford University, Stanford, CA, 94305, USA.
Eur J Nucl Med Mol Imaging. 2021 Oct;48(11):3400-3407. doi: 10.1007/s00259-021-05364-6. Epub 2021 Apr 21.
The increased glucose metabolism of cancer cells is the basis for F-fluorodeoxyglucose positron emission tomography (FDG-PET). However, due to its coarse image resolution, PET is unable to resolve the metabolic role of cancer-associated stroma, which often influences the metabolic reprogramming of a tumor. This study investigates the use of radioluminescence microscopy for imaging FDG uptake in engineered 3D tumor models with high resolution.
Multicellular tumor spheroids (A549 lung adenocarcinoma) were co-cultured with GFP-expressing human umbilical vein endothelial cells (HUVECs) within an artificial extracellular matrix to mimic a tumor and its surrounding stroma. The tumor model was constructed as a 200-μm-thin 3D layer over a transparent CdWO scintillator plate to allow high-resolution imaging of the cultured cells. After incubation with FDG, the radioluminescence signal was collected by a highly sensitive widefield microscope. Fluorescence microscopy was performed using the same instrument to localize endothelial and tumor cells.
Simultaneous and co-localized brightfield, fluorescence, and radioluminescence imaging provided high-resolution information on the distribution of FDG in the engineered tissue. The microvascular stromal compartment as a whole took up a large fraction of the FDG, comparable to the uptake of the tumor spheroids. In vitro gamma counting confirmed that A549 and HUVEC cells were both highly glycolytic with rapid FDG uptake kinetics. Despite the relative thickness of the tissue constructs, an average spatial resolution of 64 ± 4 μm was achieved for imaging FDG.
Our study demonstrates the feasibility of imaging the distribution of FDG uptake in engineered in vitro tumor models. With its high spatial resolution, the method can separately resolve tumor and stromal components. The approach could be extended to more advanced engineered cancer models but also to surgical tissue slices and tumor biopsies.
癌细胞葡萄糖代谢增加是 F-氟脱氧葡萄糖正电子发射断层扫描（FDG-PET）的基础。然而，由于其图像分辨率粗糙，PET 无法解析癌症相关基质的代谢作用，而癌症相关基质通常会影响肿瘤的代谢重编程。本研究旨在探讨利用放射发光显微镜以高分辨率对工程化 3D 肿瘤模型中的 FDG 摄取进行成像。
多细胞肿瘤球体（肺腺癌细胞 A549）与人脐静脉内皮细胞（HUVEC）共培养，在人工细胞外基质中构建以模拟肿瘤及其周围基质。肿瘤模型构建为 200μm 厚的 3D 层，覆盖透明的 CdWO 闪烁体板，以允许对培养细胞进行高分辨率成像。孵育 FDG 后，通过高灵敏度宽场显微镜收集放射发光信号。使用同一仪器进行荧光显微镜检查，以定位内皮细胞和肿瘤细胞。
同时进行的明场、荧光和放射发光成像为 FDG 在工程化组织中的分布提供了高分辨率信息。整个微血管基质隔室摄取了大量的 FDG，与肿瘤球体的摄取相当。体外γ计数证实 A549 和 HUVEC 细胞均具有高度糖酵解作用，FDG 摄取动力学迅速。尽管组织构建物的相对厚度较大，但成像 FDG 的平均空间分辨率达到 64±4μm。
本研究证明了在工程化体外肿瘤模型中成像 FDG 摄取分布的可行性。该方法具有高空间分辨率，可以分别解析肿瘤和基质成分。该方法可以扩展到更先进的工程化癌症模型，也可以扩展到手术组织切片和肿瘤活检。
