Abstract
PURPOSE The increased glucose metabolism of cancer cells is the basis for 18F-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 feasibility of imaging engineered 3D tumor models with high resolution using FDG.
METHOD 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 thin 3D layer over a transparent CdWO4 scintillator plate to allow high-resolution imaging of the cultured cells. The radioluminescence signal was collected by a highly sensitive microscope and camera. Fluorescence microscopy was performed in the same instrument to localize endothelial and tumor cells.
RESULTS Simultaneous brightfield and fluorescence imaging, co-localized with radioluminescence signal, provided high-resolution information on FDG accumulation in the engineered tissue. The microvascular stromal compartment took up a large fraction of FDG, comparable to the tumor spheroids. In vitro gamma counting also revealed that both A549 and HUVEC cells were highly glycolytic and characterized by rapid FDG-uptake kinetics.
CONCLUSION Our study demonstrates the feasibility of imaging FDG distribution in tumor and stromal components separately with high spatial resolution in engineered in vitro tumor models. Our imaging method is safe, simple, rapid, and can be easily used for other in vitro cancer models, surgical tissue slices, and tumor biopsies to interrogate PET radiotracer uptake at high resolution.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Declarations
Funding: This project was funded in part by a grant from the Stanford-Tuebingen Collaboration on Imaging Immunotherapy
Availability of data and material: All data related to this study is included in the manuscript. Additional data that support the findings of this study are available from the corresponding author upon reasonable request.
Code availability: Not applicable