Targeted gene therapy for brain tumor

恶性胶质瘤患者的预后非常差，尽管他们接受了广泛的手术治疗，并且最近在辅助放疗和化疗方面有所改善。在本研究中，我们建议使用基因修饰的间充质干细胞（MSCs）作为恶性脑肿瘤基因治疗的新工具。Fischer 344大鼠原代MSCs具有良好的体外迁移能力，对9L胶质瘤细胞的增殖有抑制作用。我们还证实了MSCs在体内的迁移能力，并表明当MSCs接种到对侧半球时，它们通过胼胝体向9L胶质瘤细胞迁移。直接植入肿瘤的MSCs主要定位于9L肿瘤细胞与正常脑实质交界处，也向肿瘤床浸润。瘤内单独注射MSCs可显著抑制9L肿瘤生长，提高9L胶质瘤大鼠的存活率。由于MSCs上缺乏受体（CAR），利用带有野生型AdS纤维（Adv- f /wt）的腺病毒载体（Adv）将基因转入MSCs的效率很低。与此形成鲜明对比的是，使用靶向整合素的纤维突变体Adv-F/RGD实现了近100%的MSCs遗传转导，该突变体在纤维旋环的hi环上具有CDCRGDCFC肽基序。用编码人白细胞介素-2（il -2）的腺病毒载体感染MSCs进行基因修饰，明显增强了其抗肿瘤作用，并进一步延长了荷瘤大鼠的生存期。因此，利用间充质干细胞作为靶向载体的基因治疗将有望成为治疗难治性侵袭性脑肿瘤的新方法。

The prognosis of patients with malignant glioma is extremely poor, despite the extensive surgical treatment that they receive and recent improvements in adjuvant radio-and chemotherapy. In the present study, we propose the use of gene-modified mesenchymal stem cells(MSCs) as a new tool for gene therapy of malignant brain neoplasms. Primary MSCs isolated from Fischer 344 rats possessed excellent migratory ability and exerted inhibitory effects on the proliferation of 9L glioma cells in vitro. We also confirmed the migratory capacity of MSCs in vivo and showed that when they were inoculated into the contralateral hemisphere, they migrated towards 9L glioma cells through the corpus callosum. MSCs implanted directly into the tumor localized mainly at the border between the 9L tumor cells and normal brain parenchyma, and also infiltrated into the tumor bed. Intratumoral injection of MSCs alone caused significant inhibition of 9L tumor growth and increased the survival of 9L glioma-bearing rats.Due to the lack of the receptor(CAR) on MSCs, the efficiency of gene transfer into MSCs by the adenoviral vector(Adv) with the wild-type AdS fiber(Adv-F/wt) was very poor. In clear contrast, nearly 100% genetic transduction of MSCs was achieved using the integrin-targeting fiber-mutant Adv-F/RGD, which possesses a CDCRGDCFC peptide motif at the HI-loop of the fiber knob. Gene-modification of MSCs by infection with an adenoviral vector encoding human interleukin-2(IL2) clearly augmented the antitumor effect and further prolonged the survival of tumor-bearing rats. Thus, gene therapy employing MSCs as a targeting vehicle would be promising as a new therapeutic approach for refractory, invasive brain tumors.