Abstract 4110: Metabolic imaging of glioblastoma using hyperpolarized 13C-MRI: Glycolytic metabolism in cancer stem cell-like cell-derived tumor model

Abstract

Abstract OBJECTIVES: Since the cancer stem-like cells (CSCs) play an important role in the resistance against radiation and/or chemotherapy due to its different metabolic profile, to investigate the specific metabolic characteristics of CSCs is valuable. Dynamic nuclear polarization (DNP) technique using 13C-labeled substrates enables magnetic resonance imaging (MRI) to monitor specific enzymatic reactions in tumors. In this study, DNP-MRI along with hyperpolarized [1-13C] pyruvate was conducted to evaluate the difference in glycolytic profile between a glioblastoma cell line and a CSC-derived glioma using orthotopic xenograft mouse model. The imaging findings were compared to those in immunohistology and cell cultures. METHODS: A 3T MRI scanner along with a custom-made head coil was used for imaging. To obtain hyperpolarized [1-13C] pyruvate, 30 μL of [1-13C] pyruvic acid containing 15 mM of OX063 (trityl radical compound) and 2.5 mM of the gadolinium chelate were polarized at 3.35 T and 1.4 K in the Hypersense DNP polarizer. The hyperpolarized sample dissolved in a buffered medium was injected via the tail vein followed by a 13C-two-dimensional spectroscopic imaging. During the acquisition, the body temperature was kept in the range of 35.0 to 36.9 Celsius degrees. Orthotopic brain tumor model was developed in nude mice by intracranial implantation of glioblastoma cell lines, U251 and glioma stem-like cells, NSC11. DNP-MRI was performed when the tumor size ranged 50 + 10 mm3 on T2-weighted MRI. Independently, immunofluorescent analyses of monocarboxylate transporter 1(MCT1) and MCT4 was performed using paraffin-embedded tumor tissue. Expressed protein level of lactate dehydrogenase A (LDHA), LDHB, MCT1 and MCT4 under the normal cell culture conditions were evaluated by Western blotting. RESULTS: 13C-MRI showed an increase in lactate-to-pyruvate ratio (Lac/Pyr) both in U251 and NSC11 compared to the contralateral normal brain tissue, suggested elevated anaerobic glycolysis (P<0.05). The extent of the increase in Lac/Pyr compared to the normal brain tissue was higher in U251 than NSC11 except for one U251 case. Western blotting showed both LDHA and LHDB expression in U251 was lower than NSC11. The expression of MCT4 was higher in U251 than NSC11, whereas they were almost the same for MCT1. Immunohistochemistry showed relative weak staining for MCT4 in NSC11, consistent with the result of Western blotting. CONCLUSION: The quality of 13C-DNP-MRI using [1-13C] pyruvate was validated and considered to be feasible to apply to the brain tumors. The result was reasonable in that malignant tumors enhance anaerobic glycolytic pathway even in the aerobic environment. 13C-DNP-MRI also demonstrated a difference in the extent of Lac/Pyr in relation to the normal brain between the two tumor models probably related to expression levels of glycolysis-related proteins. Citation Format: Tatsuya Kawai, Murali C. Krishna, Jeffery R. Brender, Jennifer Lee, Tamalee Kramp, Kazu Yamamoto, Shun Kishimoto, Tomohiro Seki, Kevin A. Camphausen. Metabolic imaging of glioblastoma using hyperpolarized 13C-MRI: Glycolytic metabolism in cancer stem cell-like cell-derived tumor model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4110.