Liao Zheng-Kai, Zhou Fu-Xiang, Luo Zhi-Guo, Zhang Wen-Jie, Xiong Jie, Bao Jie, Han Guang, Zhang Ming-Sheng, Xie Cong-Hua, Zhou Yun-Feng
Department of Cancer Radiochemotherapy, Wuhan University Zhongnan Hospital and Cancer Research Center, Hubei 430071, PR China.
Oncol Rep. 2008 Jan;19(1):281-6.
The usefulness of human telomerase reverse transcriptase (hTERT) gene promoter has been proposed in cancer-targeted gene therapy. However, this promoter may not be strong enough to achieve therapeutic levels of transgene expression. In this study, we tested an 'indirected-activator' strategy that utilizes radiation to increase the activity of the hTERT gene promoter. We demonstrated that hTERT may participate in the process of DNA repair induced by irradiation. We found that Zidovudine (AZT, an hTERT inhibitor) can decrease the telomerase activity in human HEp-2 larynx squamous carcinoma cells and lower the survival fraction of HEp-2 cells exposed to radiation. In HEp-2 cells exposed to 6 Gy-radiation, the hTERT promoter showed 2.9-fold higher activity compared with unirradiated cells. Importantly, an increased expression of enzyme horseradish peroxidase (HRP) controlled by the hTERT promoter was found in the transfected cells after irradiation, which coincided with a higher killing rate for HEp-2 cells after prodrug indole-3-acetic acid (IAA; converted by HRP into a cytotoxin) incubation combined with irradiation or not. Our observations suggest that hTERT promoter-mediated gene therapy could be improved in combination with radiotherapy, which may be due to cellular DNA damage responses.
人端粒酶逆转录酶（hTERT）基因启动子在癌症靶向基因治疗中的应用已被提出。然而，该启动子可能不够强大，无法实现治疗水平的转基因表达。在本研究中，我们测试了一种“间接激活剂”策略，该策略利用辐射来增加hTERT基因启动子的活性。我们证明hTERT可能参与了辐射诱导的DNA修复过程。我们发现齐多夫定（AZT，一种hTERT抑制剂）可以降低人HEp-2喉鳞状癌细胞中的端粒酶活性，并降低暴露于辐射的HEp-2细胞的存活分数。在暴露于6 Gy辐射的HEp-2细胞中，hTERT启动子的活性比未辐照细胞高2.9倍。重要的是，在辐照后的转染细胞中发现了由hTERT启动子控制的辣根过氧化物酶（HRP）的表达增加，这与在前药吲哚-3-乙酸（IAA；由HRP转化为细胞毒素）孵育后，无论是否联合辐照，HEp-2细胞的更高杀伤率相一致。我们的观察结果表明，hTERT启动子介导的基因治疗与放疗联合应用可能会得到改善，这可能是由于细胞DNA损伤反应所致。
