title: 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 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.
authors: Department of Radiology, Lucas MRS Research Center, Stanford School of Medicine, Stanford, CA 94305, USA. hundt@med.uni-marburg.de
authors: Walter
authors: W
authors: Hundt
authors: Silke
authors: S
authors: Steinbach
authors: Caitlin E
authors: CE
authors: O'Connell-Rodwell
authors: Dirk
authors: D
authors: Mayer
authors: Mykhaylo
authors: M
authors: Burbelko
authors: Samira
authors: S
authors: Guccione
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D003287:Contrast Media; D017930:Genes, Reporter; D015316:Genetic Therapy; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D008156:Luciferases / Q000235:genetics* / Q000378:metabolism; D008163:Luminescent Measurements; D008279:Magnetic Resonance Imaging / Q000379:methods; D008545:Melanoma / Q000098:blood supply / Q000473:pathology / Q000628:therapy*; D051379:Mice; D008819:Mice, Nude; D053758:Nanoparticles; D009368:Neoplasm Transplantation; D009842:Oligopeptides; D011401:Promoter Regions, Genetic; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics*; D014162:Transfection
chemical_list: D003287:Contrast Media; D018840:HSP70 Heat-Shock Proteins; D009842:Oligopeptides; C047981:arginyl-glycyl-aspartic acid; D008156:Luciferases; D019908:Proto-Oncogene Proteins c-raf