Delta24-hyCD adenovirus suppresses glioma growth in vivo by combining oncolysis and chemosensitization.
Replication-competent adenoviruses could provide an efficient method for delivering therapeutic genes to tumors. The most promising strategies among adenovirus-based oncolytic systems are designed to exploit free E2F-1 activity in cancer cells, which in the absence of pRb activates transcription and regulates the expression of genes involved in differentiation, proliferation, and apoptosis. We previously developed Delta24, an E1A-mutant, conditionally replicative oncolytic adenovirus. Here, we examine the ability of a second-generation Delta24 (Delta24-hyCD) engineered to express a humanized form of the Saccharomyces cerevisiae cytosine deaminase gene (hyCD). Real-time quantitative PCR, Western blotting, thin-layer chromatography, and radioisotope quantitative enzymatic assays confirmed the production of a catalytically active hyCD enzyme in the setting of an oncolytic infection in vitro; other experiments assessing local production of 5-fluorouracil and a concomitant bystander effect showed improved cytotoxicity. The IC50 dose of 5-fluorocytosine (5-FC) required for a complete cytopathic effect by the Delta24-hyCD virus was fivefold lower than with Delta24 alone in U251MG and U87MG malignant glioma (MG) cell lines. Intratumoral treatment of mice bearing intracranial U87MG xenografts with Delta24-hyCD+5-FC significantly improved survival, confirming that Delta24-hyCD with 5-FC is a more efficient anticancer tool than Delta24 alone. Histopathologically, Delta24-hyCD replication was accompanied by progressively augmented oncolysis and drug-induced necrosis. These findings demonstrate that Delta24-hyCD with concomitant systemic 5-FC is a significant improvement over the earlier Delta24 oncolytic tumor-selective strategy for therapy of experimental gliomas.
Conrad
Charles
C
Department of Neuro-Oncology, The Brain Tumor Center, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030-4009, USA. cconrad@mdanderson.org
Miller
C Ryan
CR
Ji
Yongjie
Y
Gomez-Manzano
Candeleria
C
Bharara
Suman
S
McMurray
John S
JS
Lang
Frederick F
FF
Wong
Franklin
F
Sawaya
Raymond
R
Yung
W K Alfred
WK
Fueyo
Juan
J
D000256:Adenoviridae; D017500:Adenovirus E1A Proteins / Q000235:genetics; D001483:Base Sequence; D015153:Blotting, Western; D045744:Cell Line, Tumor; D002855:Chromatography, Thin Layer; D043525:Cytosine Deaminase / Q000235:genetics / Q000627:therapeutic use*; D017931:DNA Primers; D005437:Flucytosine / Q000378:metabolism; D005472:Fluorouracil / Q000378:metabolism* / Q000627:therapeutic use; D015316:Genetic Therapy / Q000379:methods*; D005822:Genetic Vectors / Q000235:genetics / Q000627:therapeutic use*; D005910:Glioma / Q000235:genetics / Q000628:therapy*; D006801:Humans; D007150:Immunohistochemistry; D020128:Inhibitory Concentration 50; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae; D014183:Transplantation, Heterologous; D014780:Viruses
D017500:Adenovirus E1A Proteins; D017931:DNA Primers; D005437:Flucytosine; D043525:Cytosine Deaminase; D005472:Fluorouracil