裸鼠体内组织特异性胞嘧啶脱氨酶抗人类肿瘤的基因治疗

Tissue-specific cytosine deaminase gene therapy of human carcinomas in nude mice

目的：研究组织特异性表达的胞嘧啶脱氨酶（ＣＤ）基因在裸鼠体内对人类大肠癌和肝细胞癌的治疗作用。方法：将ＣＤ基因修饰的大肠癌ＬｏＶｏ细胞移植到裸鼠体内，观察对全身给予５－氟胞嘧啶（５－ＦＣ）的反应，用含ＣＤ基因的重组病毒产生细胞和５－ＦＣ治疗人肝癌裸鼠模型，并用ＰＣＲ法确定体内基因转移效果，骨髓涂片检查体内基因治疗对造血细胞的影响。结果：转ＣＤ基因对ＬｏＶｏ细胞的致瘤性无影响，全身给予５－ＦＣ治疗６０ｄ，转ＣＤ基因的大肠癌肿瘤明显缩小；ＣＥＡ启动子调控的ＣＤ（ＣＥＡ／ＣＤ）基因修饰的ＬｏＶｏ细胞形成的肿瘤在５－ＦＣ作用下消退。重组病毒在体内可以感染肿瘤、骨髓细胞，给予５－ＦＣ后取得了一定的抗肝细胞癌效果。ＣＥＡ／ＣＤ治疗组未发现明显的骨髓抑制，而ＬＴＲ调控ＣＤ的治疗组出现了明显的骨髓抑制。结论：组织特异性转录调控序列调控的ＣＤ基因体内基因治疗，较普通启动子调控的ＣＤ基因具有明显的安全性和有效性。

Objective: To investigate the therapeutic effect of tissue-specifically expressed cytosine deaminase gene on human colorectal and hepatocellular carcinomas. Methods: CD genemodified LoVo cells were implanted into BALB/c nude mice. The retrovirusproducing cells were introduced into established human hepatocellular carcinoma models. 5fluorocytosine (5FC) was systemically administrated. PCR was employed to examine in vivo infection of the retroviruses and smear examination of bone marrow was used to evaluate effect of the in vivo gene therapy on hematopoietic cells. Results: CD gene transfer alone did not alter the tumorigenicity of LoVo cells. The tumor established by modified LoVo cells significantly regressed following 5FC treatment. Complete regression was achieved in the colorectal carcinoma modified with the CEA promoter drived CD gene (CEA/CD) following 5 FC treatment for 60 d. The recombinant retrovirus produced  in situ can infect cancer cells and bone marrow cells in vivo. Anti -hepatoma effect was achieved in the models following 5FC treatment. Significant arrest of bone marrow was found in the LTR drived CD gene (LTR/CD) group. But in the CEA/CD treatment group, arrest of bone marrow could not be found. Conclusion: In vivo gene therapy with CD gene under the control of tumor tissue specific promoter is effective and safe, as compared with the universal promoter.