Department of Radiology, Lucas MRS Research Center, Stanford School of Medicine, Stanford, CA 94305, USA.
Contrast Media Mol Imaging. 2012 Sep-Oct;7(5):450-9. doi: 10.1002/cmmi.1472.
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.
我们使用生物发光成像（BLI）和磁共振成像（MRI）相结合的方法研究了针对基因治疗对黑色素瘤细胞系 M21 的影响。转染含有 hsp70（Hspa1b）或 CMV 启动子片段以及荧光素酶报告基因的质粒的 M21 细胞生长到 900mm3的肿瘤大小。每组 5 只小鼠每隔 72 小时静脉内给予由纳米颗粒、Arg-Gly-Asp 肽和显性负突变蛋白激酶抑制剂基因组成的复合物。在特定的时间间隔进行 BLI 和 MRI 检查。MRI 扫描方案包括 T1 加权自旋回波±对比剂、T2 加权快速自旋回波、动态对比增强 MRI（DCE-MRI）和扩散加权激发回波采集模式序列。T2 时间使用 1.5T GE MRI 扫描仪获得。在治疗阶段，治疗的 M21 肿瘤大小几乎保持不变（837.8 ± 133.4 与 914.8 ± 134.4mm3）。BLI 显示，如果转录受 CMV 启动子控制，荧光素酶活性降至 51.1 ± 8.3%。转录受 hsp70 启动子控制后，在 24 小时后观察到最高的荧光素酶活性（4.4 ± 0.3 倍）。肿瘤的信噪比（T2 加权图像）为 36.7 ± 0.6，随后降至 31.2 ± 4.4（p=0.004）。DCE-MRI 显示斜率和 Ak（ep）分别降低了 67.8%±4.3 和 64.8%±3.3%，与基线相比。肿瘤的 SNR 值（T1 加权图像）在应用对比剂后立即升高至 42.3 ± 1.9，随后降至 28.5 ± 3.0（p<0.001）。在治疗组中，治疗过程中扩散系数显着增加（0.66 ± 0.05 与预处理值 0.54 ± 0.009 相比，p<0.01）。因此，我们观察到针对血管生成的靶向治疗可以通过热休克/荧光素酶报告系统诱导 hsp70 启动子的激活。此外，MRI 显示对比剂摄取参数显着降低，肿瘤的扩散系数增加。
