Δ24-hyCD adenovirus suppresses glioma growth in vivo by combining oncolysis and chemosensitization

Abstract

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.

Comparative evaluation of survivin, midkine, and CXCR4 promoters for transcriptional targeting of glioma gene therapy

“…[2][3][4][5][6][7] In virotherapy, tumor cell killing is achieved by oncolysis; that is, virus replication induced cell killing. [8][9][10] Both of these therapeutic interventions allow for specific antitumor effects via molecular targeting strategies that exploit tumor markers.…”

Mutation of Escherichia coli cytosine deaminase significantly enhances molecular chemotherapy of human glioma

“…Adenoviral (Ad)-mediated CD gene therapy have been widely studied for glioma treatment in vitro and in animal tumor models. [5][6][7][8][9] A major problem associated with this suicide GDEPT approach is the low affinity displayed by the CD gene product toward 5-FC in comparison with cytosine. Thus, high doses of this prodrug must be administered in order to achieve cell killing.…”

Viruses, gene therapy and stem cells for the treatment of human glioma

“…54 A Delta-24 construct (Delta24-hyCD) expressing a humanized form of the saccharomyces cerevisiae cytosine deaminase gene (hyCD) administered intracranially with concomitant 5-fluorocytosine in animals with gliomas showed improved cytotoxicity and animal survival compared with Delta-24 alone. 55 OBP-405, an oncolytic adenovirus regulated by the human telomerase reverse transcriptase promoter (hTERT-Ad, OBP-301) with a tropism modification (RGD) showed a strong antitumor effect on glioblastoma cells mediated by autophagy. Moreover, temozolomide and rapamycin administered in combination with OBP-405 in mice with intracranial gliomas resulted in prolonged survival.…”