Delta-24 increases the expression and activity of topoisomerase I and enhances the antiglioma effect of irinotecan.
OBJECTIVE
In this study, we sought to determine whether Delta-24 could sensitize glioma cells to the topoisomerase I inhibitor irinotecan (CPT-11) and to identify the mechanisms underlying this enhanced anticancer effect.


METHODS
We used human glioblastoma cell lines for the in vitro studies. The expression of topoisomerase I was determined in Western blot analyses, and topoisomerase I activity was determined by measuring the relaxation of a supercoiled DNA. The cell cycle distribution of cells was determined by flow cytometry analysis of the cellular DNA content. Cell viability was quantified by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Tissue culture infection dose assays were used to quantitate adenovirus replication. For the in vivo studies, athymic mice received intracranial/intratumoral injections of Delta-24 in combination with CPT-11, after which animal survival was monitored.


RESULTS
Delta-24 infection caused human glioma cells to accumulate in the S phase and induced the expression and activity of topoisomerase I as shown by Western blot and in vitro enzymatic activity assays. Further, we showed that the sequential administration of Delta-24 and CPT-11 to human glioma cell cultures potentiated the CPT-11-mediated anticancer effect in vitro without modifying the replicative phenotype of the oncolytic adenovirus. In vivo experiments showed that the single intratumoral administration of Delta-24 to intracranially implanted human glioma xenografts followed by the systemic administration of CPT-11 resulted in significantly prolonged animal survival.


CONCLUSIONS
The combination of Delta-24 treatment with CPT-11 showed an enhanced anticancer effect, which suggests that the interaction between adenoviral and human proteins can be exploited in rational anticancer therapies comprising replication-competent adenoviruses and conventional chemotherapeutic agents.
Gomez-Manzano
Candelaria
C
Department of Neuro-Oncology, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
Alonso
Marta M
MM
Yung
W K Alfred
WK
McCormick
Frank
F
Curiel
David T
DT
Lang
Frederick F
FF
Jiang
Hong
H
Bekele
B Nebiyou
BN
Zhou
Xian
X
Alemany
Ramon
R
Fueyo
Juan
J
D000256:Adenoviridae; D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000627:therapeutic use*; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000201:enzymology; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000627:therapeutic use; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004357:Drug Synergism; D005434:Flow Cytometry; D005909:Glioblastoma / Q000188:drug therapy* / Q000201:enzymology; D006801:Humans; D000077146:Irinotecan; D051379:Mice; D008819:Mice, Nude; D016196:S Phase; D015996:Survival Rate; D059004:Topoisomerase I Inhibitors; D014183:Transplantation, Heterologous; D014407:Tumor Cells, Cultured
D000972:Antineoplastic Agents, Phytogenic; D059004:Topoisomerase I Inhibitors; D000077146:Irinotecan; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin