Rehemtulla Alnawaz, Hall Daniel E, Stegman Lauren D, Prasad Uttara, Chen Grace, Bhojani Mahaveer Swaroop, Chenevert Thomas L, Ross Brian D
University of Michigan School of Medicine, USA.
Mol Imaging. 2002 Jan-Mar;1(1):43-55. doi: 10.1162/15353500200200005.
Cancer gene therapy is an active area of research relying upon the transfer and subsequent expression of a therapeutic transgene into tumor cells in order to provide for therapeutic selectivity. Noninvasive assessment of therapeutic response and correlation of the location, magnitude, and duration of transgene expression in vivo would be particularly useful in the development of cancer gene therapy protocols by facilitating optimization of gene transfer protocols, vector development, and prodrug dosing schedules. In this study, we developed an adenoviral vector containing both the therapeutic transgene yeast cytosine deaminase (yCD) along with an optical reporter gene (luciferase). Following intratumoral injection of the vector into orthotopic 9 L gliomas, anatomical and diffusion-weighted MR images were obtained over time in order to provide for quantitative assessment of overall therapeutic efficacy and spatial heterogeneity of cell kill, respectively. In addition, bioluminescence images were acquired to assess the duration and magnitude of gene expression. MR images revealed significant reduction in tumor growth rates associated with yCD/5-fluorocytosine (5FC) gene therapy. Significant increases in mean tumor diffusion values were also observed during treatment with 5FC. Moreover, spatial heterogeneity in tumor diffusion changes were also observed revealing that diffusion magnetic resonance imaging could detect regional therapeutic effects due to the nonuniform delivery and/or expression of the therapeutic yCD transgene within the tumor mass. In addition, in vivo bioluminescence imaging detected luciferase gene expression, which was found to decrease over time during administration of the prodrug providing a noninvasive surrogate marker for monitoring gene expression. These results demonstrate the efficacy of the yCD/5FC strategy for the treatment of brain tumors and reveal the feasibility of using multimodality molecular and functional imaging for assessment of gene expression and therapeutic efficacy.
癌症基因治疗是一个活跃的研究领域，它依赖于将治疗性转基因转移并随后在肿瘤细胞中表达，以实现治疗的选择性。对治疗反应进行无创评估以及对体内转基因表达的位置、强度和持续时间进行关联分析，对于优化基因转移方案、载体开发和前药给药方案，从而推动癌症基因治疗方案的发展将特别有用。在本研究中，我们构建了一种腺病毒载体，其既包含治疗性转基因酵母胞嘧啶脱氨酶（yCD），又包含一个光学报告基因（荧光素酶）。将该载体瘤内注射到原位9L胶质瘤后，随时间获取解剖学和扩散加权磁共振图像，以便分别对总体治疗效果和细胞杀伤的空间异质性进行定量评估。此外，还采集生物发光图像以评估基因表达的持续时间和强度。磁共振图像显示，yCD/5-氟胞嘧啶（5FC）基因治疗使肿瘤生长速率显著降低。在用5FC治疗期间，平均肿瘤扩散值也显著增加。而且，还观察到肿瘤扩散变化存在空间异质性，这表明扩散磁共振成像能够检测到由于治疗性yCD转基因在肿瘤块内递送和/或表达不均匀而产生的局部治疗效果。此外，体内生物发光成像检测到荧光素酶基因表达，发现在给予前药期间其随时间下降，为监测基因表达提供了一种无创替代标志物。这些结果证明了yCD/5FC策略治疗脑肿瘤的有效性，并揭示了使用多模态分子和功能成像评估基因表达和治疗效果的可行性。
