Komata T, Kondo Y, Kanzawa T, Hirohata S, Koga S, Sumiyoshi H, Srinivasula S M, Barna B P, Germano I M, Takakura M, Inoue M, Alnemri E S, Shay J W, Kyo S, Kondo S
Center for Surgery Research, Department of Neurosurgery, The Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Cancer Res. 2001 Aug 1;61(15):5796-802.
Because the apoptotic pathway is often disrupted in tumor cells, its genetic restoration is a very attractive approach for the treatment of tumors. To treat malignant gliomas with this approach, it would be preferred to restrict induction of apoptosis to tumor cells by establishing a tumor-specific expression system. Telomerase is an attractive target because the vast majority of malignant gliomas have telomerase activity whereas normal brain cells do not. Activation of telomerase is tightly regulated at the transcriptional level of the telomerase catalytic subunit [human telomerase reverse transcriptase, (hTERT)]. Therefore, we hypothesized that using a hTERT promoter-driven vector system, an apoptosis-inducible gene may be preferentially restricted to telomerase- or hTERT-positive tumor cells. In this study, we constructed an expression vector consisting of the constitutively active caspase-6 (rev-caspase-6) under the hTERT promoter (hTERT/rev-caspase-6) and then investigated its antitumor effect on malignant glioma cells. The rationale for using the rev-caspase-6 gene is because it induces apoptosis independent of the initiator caspases. We demonstrated that the hTERT/rev-caspase-6 construct induced apoptosis in hTERT-positive malignant glioma cells, but not in hTERT-negative astrocytes, fibroblasts, and alternative lengthening of telomeres cells. In addition, the growth of s.c. tumors in nude mice was significantly suppressed by the treatment with hTERT/rev-caspase-6 construct. The present results strongly suggest that the telomerase-specific transfer of the rev-caspase-6 gene under the hTERT promoter is a novel targeting approach for the treatment of malignant gliomas.
由于凋亡途径在肿瘤细胞中常常被破坏，因此其基因修复是一种非常有吸引力的肿瘤治疗方法。为了用这种方法治疗恶性胶质瘤，通过建立肿瘤特异性表达系统将凋亡诱导限制在肿瘤细胞中会是更可取的。端粒酶是一个有吸引力的靶点，因为绝大多数恶性胶质瘤具有端粒酶活性，而正常脑细胞则没有。端粒酶的激活在端粒酶催化亚基[人端粒酶逆转录酶，(hTERT)]的转录水平上受到严格调控。因此，我们假设使用hTERT启动子驱动的载体系统，凋亡诱导基因可能会优先限制在端粒酶或hTERT阳性的肿瘤细胞中。在本研究中，我们构建了一个表达载体，其由hTERT启动子(hTERT/ rev-caspase-6)控制下的组成型活性半胱天冬酶-6(rev-caspase-6)组成，然后研究了其对恶性胶质瘤细胞的抗肿瘤作用。使用rev-caspase-6基因的理论依据是它能独立于起始半胱天冬酶诱导凋亡。我们证明hTERT/rev-caspase-6构建体在hTERT阳性的恶性胶质瘤细胞中诱导凋亡，但在hTERT阴性的星形胶质细胞、成纤维细胞和端粒替代延长细胞中不诱导凋亡。此外，用hTERT/rev-caspase-6构建体处理可显著抑制裸鼠皮下肿瘤的生长。目前的结果强烈表明，hTERT启动子控制下的rev-caspase-6基因的端粒酶特异性转移是一种治疗恶性胶质瘤的新型靶向方法。
