Imaging hNET Reporter Gene Expression with 124I-MIBG

doi:10.2967/jnumed.106.037812

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Imaging hNET Reporter Gene Expression with ¹²⁴I-MIBG

Maxim A. Moroz^*^,1, Inna Serganova^*^,1, Pat Zanzonico², Ludmila Ageyeva¹, Tatiana Beresten¹, Ekaterina Dyomina¹, Eva Burnazi³, Ronald D. Finn^3–5^,, Michael Doubrovin¹ and Ronald G. Blasberg¹^,4^,5

¹ Department of Neurology, Memorial Sloan-Kettering Cancer Center, New York, New York; ² Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York; ³ Cyclotron and Radiochemistry Core Facility, Memorial Sloan-Kettering Cancer Center, New York, New York; ⁴ Department of Radiology, Memorial Sloan-Kettering Cancer Center, New York, New York; and ⁵ Memorial Hospital Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, New York, New York

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FIGURE 1. Development of reporter system and reporter cells. (A) Structure of pQcmv-hNET-IRES-GFP vector. (B) Fluorescence-activated cell sorting (FACS) analyses of C6 (1), COS-7 (2), and Jurkat (3) wild-type and pQcmv-hNET-IRES-GFP transduced cells after FACS. LTR = long terminal repeat; dLTR = LTR with deleted promoter sequence; M1 = range of GFP expression; FLT-1 = fluorescent channel 1.

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FIGURE 2. In vitro assessment of hNET-IRES-GFP reporter system. (A) Time–activity profiles of ¹²³I-MIBG accumulation (mL medium/g cells) in transduced C6 cells (closed diamond), Jurkat cells (open-crossed square), and COS-7 cells (open circle) and in corresponding wild-type cells (open diamond, closed square, and closed circle, respectively). Data were fitted to a 1-compartment model and yielded estimates of K₁, k₂, and V_d (Table 1). (B) ¹²³I-MIBG accumulation (V_d, Table 1) values vs. mean GFP expression values for pQcmv-hNET-IRES-GFP transduced C6 cells (closed diamond), Jurkat cells (open-crossed square), and COS-7 cells (open circle). (C) Western blot analysis for hNET and ß-actin proteins in hNET-IRES-GFP transduced C6 cells (band 2), COS-7 cells (band 4), and Jurkat cells (band 6) and in corresponding wild-type cells (bands 1, 3, and 5, respectively). SK-N-SH neuroblastoma cells served as positive control (band 7).

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FIGURE 3. ${gamma}$ -Camera planar (A) and SPECT (B) images of same tumor-bearing mouse at 4, 24, and 48 h after intravenous injection of 11.1 MBq (300 µCi) of ¹²³I-MIBG. Images are coronal views with animal's head at top and tail at bottom of each image. Mouse has C6/hNET-IRES-GFP and C6 wild-type xenografts in opposite shoulders. Images are semiquantitative, with planar and SPECT image intensities normalized to maximum count-rate density (i.e., counts per minute [cpm] per pixel and per voxel, respectively) in corresponding 24-h image. Arrows identify the thyroid gland, hNET-expressing xenograft, and bladder.

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FIGURE 4. Sequential microPET images of ¹²⁴I-MIBG biodistribution. Sequential coronal (A) and axial (B) images over 72 h of same mouse bearing C6/hNET-IRES-GFP and C6 wild-type xenografts in opposite shoulders after intravenous injection of 7.4 MBq (200 µCi) of ¹²⁴I-MIBG. Arrows identify hNET-expressing xenograft in each image. Max = maximum; Min = minimum.

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FIGURE 5. Time–activity profiles of ¹²⁴I-MIBG accumulation. (A) Tissue radioactivity values (%ID/g) were determined from sequential microPET images (see Fig. 4), and time–activity profiles for C6/hNET-IRES-GFP (circles) and C6 wild-type xenografts (diamonds) are shown. (B) Xenograft-to-muscle profiles are also shown. Values are mean ± SD; n = 10.