In 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

Abstract

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 mm3. 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 T1‐weighted‐spin‐echo ± contrast medium, T2‐weighted‐fast‐spin‐echo, dynamic contrast‐enhanced MRI (DCE‐MRI), and diffusion‐weighted‐stimulated‐echo‐acquisition‐mode‐sequence. The T2 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 mm3). 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; T2‐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 Akep of 67.8% ± 4.3 and 64.8% ± 3.3%, respectively, compared with the baseline. The SNR value (T1‐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.

Imaging tumour distribution of a polymeric drug delivery platform in vivo by PET‐MRI

“…Thus, advanced imaging and analysis have allowed us to show that penetration of the polymeric nanomedicine into the tumour is not homogenous and that the concentration is highest closest to the blood vessels supplying the tumour. Importantly, this is in agreement with a wide body of secondary experimental evidence ( in vitro and ex vivo studies) and with phenomenological in vivo studies . However, unlike previous studies, this work has demonstrated the power of PET‐MRI to directly measure tumour distribution of nanoparticles, in vivo .…”

“…Importantly, this is in agreement with a wide body of secondary experimental evidence (in vitro and ex vivo studies) 19 -21 and with phenomenological in vivo studies. 37 However, unlike previous studies, this work has demonstrated the power of PET-MRI to directly measure tumour distribution of nanoparticles, in vivo. Moreover, our approach allows monitoring of the nanomedicine distribution over time, in the one subject.…”

Evaluation of Antitumor Activity of Long-Circulating and pH-Sensitive Liposomes Containing Ursolic Acid in Animal Models of Breast Tumor and Gliosarcoma

“…The technique is sensitive to alterations in vascular permeability, extracellular extravascular and vascular volumes, and blood flow. 24 , 27 , 28 …”