Treatment of malignant glioma cells with the transfer of constitutively active caspase-6 using the human telomerase catalytic subunit (human telomerase reverse transcriptase) gene promoter.
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.
Komata
T
T
Center for Surgery Research, Department of Neurosurgery, The Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Kondo
Y
Y
Kanzawa
T
T
Hirohata
S
S
Koga
S
S
Sumiyoshi
H
H
Srinivasula
S M
SM
Barna
B P
BP
Germano
I M
IM
Takakura
M
M
Inoue
M
M
Alnemri
E S
ES
Shay
J W
JW
Kyo
S
S
Kondo
S
S
D000818:Animals; D017209:Apoptosis / Q000235:genetics; D053178:Caspase 6; D020169:Caspases / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins; D018014:Gene Transfer Techniques; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000235:genetics; D005910:Glioma / Q000201:enzymology / Q000235:genetics / Q000473:pathology / Q000628:therapy*; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012313:RNA; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D019098:Telomerase / Q000096:biosynthesis / Q000235:genetics*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
D004268:DNA-Binding Proteins; D012333:RNA, Messenger; C422952:telomerase RNA; D012313:RNA; D019098:Telomerase; C505514:CASP6 protein, human; C505516:Casp6 protein, mouse; D053178:Caspase 6; D020169:Caspases