Figure S1. Timeline of injections and imaging for the main treatment-response study. Figure S2. Tumor volume measurements for (a) Colo205 and (b) MDA-MB-231 tumors (b & e) before and (c & f) 24 h after MEDI3039 treatment. Figure S3. Confirmation that [18F]FDG uptake was similar before and 24 h after treatment. Examples of autoradiography of whole-body axial sections of Colo205 tumor-bearing mice (the tumors are outlined) before (a - c) and 24 h after treatment (d - f). Figure S4. Dynamic contrast enhanced MRI measurements of perfusion in Colo205 tumors before and 24 h after treatment with MEDI3039. Figure S5. RadioHPLC measurements of [18F]FDG metabolism in Colo205 tumors 24 h after control (drug vehicle) or MEDI3039 treatment. Table S1. Colo205 mice that underwent fluorescence, bioluminescence, hyperpolarized MR and PET-CT imaging and reasons for their exclusion. Table S2. MDA-MB-231 mice that underwent fluorescence, bioluminescence, hyperpolarized MR and PET-CT imaging and reasons for their exclusion. Table S3. Antibodies used for Western blotting. Table S4. Expression of the transporters and enzymes and the activities of the enzymes involved in [18F]FDG and [1-13C]pyruvate uptake and metabolism in Colo205 tumors.
ARTICLE ABSTRACT
Metabolic imaging has been widely used to measure the early responses of tumors to treatment. Here, we assess the abilities of PET measurement of [18F]FDG uptake and MRI measurement of hyperpolarized [1-13C]pyruvate metabolism to detect early changes in glycolysis following treatment-induced cell death in human colorectal (Colo205) and breast adenocarcinoma (MDA-MB-231) xenografts in mice. A TRAIL agonist that binds to human but not mouse cells induced tumor-selective cell death. Tumor glycolysis was assessed by injecting [1,6-13C2]glucose and measuring 13C-labeled metabolites in tumor extracts. Injection of hyperpolarized [1-13C]pyruvate induced rapid reduction in lactate labeling. This decrease, which correlated with an increase in histologic markers of cell death and preceded decrease in tumor volume, reflected reduced flux from glucose to lactate and decreased lactate concentration. However, [18F]FDG uptake and phosphorylation were maintained following treatment, which has been attributed previously to increased [18F]FDG uptake by infiltrating immune cells. Quantification of [18F]FDG uptake in flow-sorted tumor and immune cells from disaggregated tumors identified CD11b+/CD45+ macrophages as the most [18F]FDG-avid cell type present, yet they represented <5% of the cells present in the tumors and could not explain the failure of [18F]FDG-PET to detect treatment response. MRI measurement of hyperpolarized [1-13C]pyruvate metabolism is therefore a more sensitive marker of the early decreases in glycolytic flux that occur following cell death than PET measurements of [18F]FDG uptake.
These findings demonstrate superior sensitivity of MRI measurement of hyperpolarized [1-13C]pyruvate metabolism versus PET measurement of 18F-FDG uptake for detecting early changes in glycolysis following treatment-induced tumor cell death.
