SPECT imaging of glioma with radioiodinated CLINDE: evidence from a mouse GL26 glioma model

Background: Recent research has demonstrated the potential of 18-kDa translocator protein (TSPO) to serve as a target for nuclear imaging of gliomas. The aim of this study was to evaluate SPECT imaging of GL26 mouse glioma using radioiodinated CLINDE, a TSPO-specific tracer. Methods: GL26 cells, previously transfected with an enhanced green fluorescent protein (EGFP)-expressing lentivirus, were stereotactically implanted in the striatum of C57/Bl6 mice. At 4 weeks post-injection, dynamic SPECT scans with [I-123] CLINDE were performed. A displacement study assessed specificity of tracer binding. SPECT images were compared to results of autoradiography, fluorescence microscopy, in situ nucleic acid hybridization, histology, and immunohistochemistry. Western blotting was performed to verify TSPO production by the tumor. Results: Specific uptake of tracer by the tumor is observed with a high signal-to-noise ratio. Tracer uptake by the tumor is indeed 3.26 +/- 0.32 times higher than that of the contralateral striatum, and 78% of the activity is displaceable by unlabeled CLINDE. Finally, TSPO is abundantly expressed by the GL26 cells. Conclusions: The present study demonstrates the feasibility of [I-123] CLINDE SPECT in translational studies and underlines its potential for clinical glioma SPECT imaging.