The diagnostic definition of indeterminate lung nodules as malignant or benign poses a major challenge for clinicians. We discovered a potential marker, the sodium glucose transporter 2 (SGLT2), whose activity identified metabolically active lung premalignancy and early-stage lung adenocarcinoma (LADC). We found that SGLT2 is expressed early in lung tumorigenesis and is found specifically in pre-malignant lesions and well-differentiated adenocarcinomas. Of note, SGLT2 activity could be detected in vivo by positron emission tomography (PET) with the tracer methyl-4-[18F] fluorodeoxyglucose (Me4FDG), which specifically detects SGLT activity. Using a combination of immunohistochemistry and Me4FDG PET, we identified high expression and functional activity of SGLT2 in lung premalignancy and early-stage/low-grade LADC. Furthermore, selective targeting of SGLT2 with FDA-approved small molecule inhibitors, the gliflozins, greatly reduced tumor growth and prolonged survival in autochthonous mouse models and patient-derived xenografts of LADC. Targeting SGLT2 in lung tumors may intercept lung cancer progression at early stages of development by pairing Me4FDG PET imaging with therapy using SGLT2 inhibitors.
A.J. performed transthoracic injections. G.A. performed a portion of the CT scans. M.M. and S.T.B. performed IHC staining and analyzed data. M.M. J.T.L. and A.J. performed in vitro 18 FBnTP uptake assays. M.M. did TMRE staining and western blots. M.C.F is a board-certified anatomic pathologist who performed the pathological analysis. L.S. and O.S. performed and guided respirometry experiments. S.S., C.M.W., A.G. and T.H. performed radio-tracer synthesis. D.D. and C.K. performed biochemical analysis of mitochondria. E.S. and H.C. performed metabolic analysis of lung tumors. S.M.D. contributed resources and critical feedback on the project. Data availability Source data for Western blots are provided with the paper as Supplementary Figure 1. Source data for Figures 1b-d; Figures 2d-g; Figures 3b, 3d, 3e; ED Figures 3c-e; ED Figures 4c, 4d; ED Figure 9a are provided with the paper. The data that support the findings of this study are available from the corresponding author upon reasonable request.
Glucose is a major source of energy for most living organisms and its aberrant uptake is linked to many pathological conditions. However, our understanding of disease-associated glucose flux is limited due to the lack of robust tools. To date, positron emission tomography (PET) imaging remains the gold standard for measuring glucose uptake, and no optical tools exist for non-invasive longitudinal imaging of this important metabolite in in vivo settings. Here we report the development of a novel bioluminescent glucose uptake probe (BiGluc) for real-time, non-invasive longitudinal imaging of glucose absorption both in vitro and in vivo. In addition, we demonstrate that the sensitivity of our method is comparable with commonly used 18F-FDG-PET tracers and validate BiGluc as a tool for the identification of novel glucose transport inhibitors. The new imaging reagent enables a wide range of applications in the field of metabolism and drug development.
A hallmark of advanced tumors is a switch to aerobic glycolysis that is readily measured by [18F]-2-fluoro-2-deoxy-D-glucose positron emission tomography (18F-FDG PET) imaging. Co-mutations in the KRAS proto-oncogene and the LKB1 tumor suppressor gene are frequent events in lung cancer that drive hypermetabolic, glycolytic tumor growth. A critical pathway regulating the growth and metabolism of these tumors is the mechanistic target of the rapamycin (mTOR) pathway, which can be effectively targeted using selective catalytic mTOR kinase inhibitors. The mTOR inhibitor MLN0128 suppresses glycolysis in mice bearing tumors with Kras and Lkb1 co-mutations, referred to as KL mice. The therapy response in KL mice is first measured by 18F-FDG PET and computed tomography (CT) imaging before and after the delivery of MLN0128. By utilizing 18F-FDG PET/CT, researchers are able to measure dynamic changes in the glucose metabolism in genetically engineered mouse models (GEMMs) of lung cancer following a therapeutic intervention with targeted therapies. This is followed by ex vivo autoradiography and a quantitative immunohistochemical (qIHC) analysis using morphometric software. The use of qIHC enables the detection and quantification of distinct changes in the biomarker profiles following treatment as well as the characterization of distinct tumor pathologies. The coupling of PET imaging to quantitative histology is an effective strategy to identify metabolic and therapeutic responses in vivo in mouse models of disease.
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