Imaging vascular characteristics and glycolytic metabolism of glioblastoma in a chick embryo model using 1H MRI and [18F]FDG-PET

Purpose: To assess hypoxia-associated host-tumour vascular adaptations and glycolytic metabolism in the chick chorioallantoic membrane (CAM) glioblastoma model. Procedures: U251 GBM cells were conditioned under normoxia (21% O₂) or hypoxia (1% O₂) for 72 hours before implantation onto the CAM on embryonic day 7 (E7). Imaging was performed on E13 using MRI (control-CAM n=8, normoxic-tumour n=7, hypoxic-tumour n=6) and brightfield microscopy (control-CAM n=7, normoxic-tumour n=8, hypoxic-tumour n=7). Tumours were harvested on E14 for histology and gene expression analyses. In a separate cohort, under normoxic conditioning, glucose metabolism was assessed using [ ¹⁸ F]FDG-PET on E12 followed by lactate MRS on E13 (n=25). Results Normoxia- and hypoxia-conditioned tumour-bearing CAMs exhibited vascular remodelling and significant upregulation of VEGFA and ADM compared to cultured cells . αSMA staining confirmed vessel infiltration in normoxia-conditioned tumours. CAIX staining revealed a hypoxic core in these tumours while hypoxia-conditioned tumours displayed heterogeneous staining. In both conditions, GLUT1 staining colocalised with CAIX staining, indicating hypoxia-associated glycolysis. GLUT1, PDK1 and LDHA expression was elevated in CAM tumours relative to tumour cells in vitro. In the metabolic imaging cohort, most tumours exhibited [¹⁸F]FDG uptake and lactate signal. However, no statistically significant relationship was observed between the two methods. Conclusions The CAM model provides a versatile platform for investigating GBM vascularisation and metabolism. Hypoxic conditioning amplifies transcriptional and vascular changes to the CAM. Although both [¹⁸F]FDG uptake and lactate were measurable, no significant correlation between the two was observed, potentially reflecting variability in tumour engraftment, vascular delivery of [¹⁸F]FDG, and microenvironmental influences on lactate accumulation.