Investigations of 99mTc-labeled glucarate as a SPECT radiotracer for non-small cell lung cancer (NSCLC) and potential tumor uptake mechanism

This study attempted to evaluate the feasibility of 99mTc-labeled glucarate (99mTc-GLA) imaging in non-small cell lung cancer (NSCLC) and the potential tumor uptake mechanism. Cell lysates from two NSCLC cell lines, H292 and H1975, were immunoblotted with anti-glucose transporter 5 (GLUT5) antibody for Western blotting. Thereafter, the two cell lines were used to examine cellular uptake of 99mTc-GLA with or without fructose. SPECT/CT imaging studies were performed on small animals bearing H292 and H1975 tumors. Biodistribution studies were also conducted to achieve accurate tissue uptake of this tracer in two tumor models. Hematoxylin & eosin (H&E) staining and GLUT5, Ki67 and cytokeratin-7 (CK-7) immunohistochemistry (IHC) analysis were further investigated on tumor tissues. In Western blotting, H292 cells showed higher levels of GLUT5 compared to the H1975 cells. Meanwhile, the in vitro cell assays indicated GLUT5-dependent uptake of 99mTc-GLA in H292 and H1975 cells. The fructose competition assays showed a significant decrease in 99mTc-GLA uptake by H292 and H1975 cells when fructose was added. The 99mTc-GLA accumulation was as much as two-fold higher in H292 implanted tumors than in H1975 implanted tumors. 99mTc-GLA exhibited rapid clearance pharmacokinetics and reasonable uptake in human NSCLC H292 (1.69 ± 0.37 ID%/g) and H1975 (0.89 ± 0.06 ID%/g) implanted tumors at 30 min post injection. Finally, the expression of GLUT5, Ki67 and CK-7 on tumor tissues also exhibited positive correlation with the in vitro cell test results and in vivo SPECT/CT imaging results in xenograft tumors. Both in vitro and ex vivo studies demonstrated that the uptake of 99mTc-GLA in NSCLC is highly related to GLUT5 expression. Imaging and further IHC results support that 99mTc-GLA could be a promising SPECT imaging agent for NSCLC diagnosis and prognosis evaluation.