Tai Kuo-Feng, Chen Pei-Jer, Chen Ding-Shinn, Hwang Lih-Hwa
Graduate Institute of Microbiology, National Taiwan University College of Medicine, Taipei 10016, Taiwan.
J Gene Med. 2003 May;5(5):386-98. doi: 10.1002/jgm.376.
The immune resistance of large tumors represents a major problem for cancer immunotherapy, whereas the need for repeated injections of high doses of recombinant anti-angiogenic proteins represents a similar problem for anti-angiogenic therapy. To test whether antitumor activity could be increased by combining the above two mechanisms, this study examined the therapeutic effect of combination gene therapy using a murine granulocyte-macrophage colony-stimulating factor (mGM-CSF) gene and a human endostatin (hED) gene on a rat orthotopic liver tumor model.
An adenoviral vector was constructed that simultaneously carried two transcriptional cassettes, for the expression of mGM-CSF and hED, respectively, or that carried a single cassette of either gene. The adenoviruses were intratumorally administered to 3-day-old or 7-day-old tumors. Moreover, the antitumor effects of the combination therapy and monotherapy were assessed and compared.
The double-gene-containing adenoviral vector expressed transgenes as efficiently as the single-gene-containing vector. Moreover, the adenovirally expressed endostatin was biologically active, as demonstrated in vitro and in vivo. Results from animal experiments demonstrated a synergistic antitumor effect induced by the combined mGM-CSF and hED therapy. The combination of hED with mGM-CSF enhanced tumor-specific CTL activity, but did not interfere with the infiltration of cellular effectors in the tumor regions. The blood vessel density of the liver tumors markedly reduced as a result of hED expression in both monotherapy and combination therapy. Furthermore, combination therapy significantly increased the number of apoptotic cells in the tumor regions.
The experimental results suggest that the combined gene therapy against tumor cells and the tumor vascular system using antitumor immune mechanisms and anti-angiogenic mechanisms holds promise as a strategy for treating cancers.
大肿瘤的免疫抗性是癌症免疫治疗面临的一个主要问题，而反复注射高剂量重组抗血管生成蛋白的需求是抗血管生成治疗中类似的问题。为了测试联合上述两种机制是否可以提高抗肿瘤活性，本研究检测了使用小鼠粒细胞巨噬细胞集落刺激因子（mGM-CSF）基因和人内皮抑素（hED）基因的联合基因疗法对大鼠原位肝肿瘤模型的治疗效果。
构建了一种腺病毒载体，其同时携带两个转录盒，分别用于表达mGM-CSF和hED，或者携带单个基因的转录盒。将腺病毒瘤内注射到3日龄或7日龄的肿瘤中。此外，评估并比较了联合疗法和单一疗法的抗肿瘤效果。
含双基因的腺病毒载体与含单基因的载体一样有效地表达转基因。此外，腺病毒表达的内皮抑素具有生物活性，这在体外和体内均得到证实。动物实验结果表明，联合mGM-CSF和hED疗法可诱导协同抗肿瘤作用。hED与mGM-CSF的联合增强了肿瘤特异性CTL活性，但不干扰肿瘤区域细胞效应器的浸润。由于hED在单一疗法和联合疗法中的表达，肝肿瘤的血管密度显著降低。此外，联合疗法显著增加了肿瘤区域凋亡细胞的数量。
实验结果表明，利用抗肿瘤免疫机制和抗血管生成机制联合针对肿瘤细胞和肿瘤血管系统的基因疗法有望成为一种治疗癌症的策略。
