Open AccessIn vivo monitoring of antiangiogenic therapy by magnetic resonance and bioluminescence imaging in an M21 tumor model through activation of an hsp70 promoter–luciferase reporter construct
Author(s) -
Hundt Walter,
Steinbach Silke,
O'ConnellRodwell Caitlin E.,
Mayer Dirk,
Burbelko Mykhaylo,
Guccione Samira
Publication year - 2012
Publication title -
contrast media & molecular imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.714
H-Index - 50
eISSN - 1555-4317
pISSN - 1555-4309
DOI - 10.1002/cmmi.1472
Subject(s) - luciferase , bioluminescence imaging , magnetic resonance imaging , in vivo , bioluminescence , microbiology and biotechnology , nuclear magnetic resonance , chemistry , electroporation , transfection , medicine , biology , gene , physics , biochemistry , radiology
We have investigated the effect of targeted gene therapy on the melanoma cell line M21, using a combination of bioluminescence imaging (BLI) and magnetic resonance imaging (MRI). M21 cells transfected with a plasmid containing either an hsp70 ( Hspa1b ) or a CMV promoter fragment, along with the luciferase reporter gene, were grown to a tumor size of 900 mm 3 . Five mice in each group were intravenously treated every 72 h with a complex consisting of a nanoparticle, an Arg–Gly–Asp–peptide, and a dominant negative mutant protein kinase inhibitor gene. BLI and MRI were performed at specific time intervals. The MRI scan protocol included T 1 ‐weighted‐spin‐echo ± contrast medium, T 2 ‐weighted‐fast‐spin‐echo, dynamic contrast‐enhanced MRI (DCE‐MRI), and diffusion‐weighted‐stimulated‐echo‐acquisition‐mode‐sequence. The T 2 times were obtained using a 1.5 T GE MRI scanner. The size of the treated M21 tumors remained almost constant during the treatment phase (837.8 ± 133.4 vs 914.8 ± 134.4 mm 3 ). BLI showed that, if transcription was controlled by the CMV promoter, the luciferase activity decreased to 51.1 ± 8.3%. After transcription was controlled by the hsp70 promoter, the highest luciferase activity (4.4 ± 0.3 fold) was seen after 24 h. The signal‐to‐noise ratio (SNR; T 2 ‐weighted images) of the tumors was 36.7 ± 0.6 and subsequently dropped to 31.2 ± 4.4 ( p = 0.004). DCE‐MRI showed a reduction of the slope and the Ak ep of 67.8% ± 4.3 and 64.8% ± 3.3%, respectively, compared with the baseline. The SNR value ( T 1 ‐weighted images) of the tumors was 42.3 ± 1.9 immediately following contrast medium application and subsequently dropped to 28.5 ± 3.0 ( p < 0.001). In the treatment group, the diffusion coefficient increased significantly under therapy (0.66 ± 0.05 vs the pretreatment value of 0.54 ± 0.009 p < 0.01). Thus, we observed that targeted antiangiogenic therapy can induce activation of the hsp70 promoter through a heat shock/luciferase reporter system. Moreover, MRI showed a significant reduction of the contrast medium uptake parameters and an increase in the diffusion coefficient of the tumors. Copyright © 2012 John Wiley & Sons, Ltd.