Delta-24 Increases the Expression and Activity of Topoisomerase I and Enhances the Antiglioma Effect of Irinotecan

Abstract

Purpose: 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. Experimental Design: 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-11to 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-11resulted in significantly prolonged animal survival. Conclusions: The combination of Delta-24 treatment with CPT-11showed 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.Tumor-selective replication is one of the most relevant advances in adenovirus-based anticancer therapies. The oncolytic virus is itself capable of lysing the infected tumor cell to eradicate or reduce tumor mass. Replication amplifies the input dose of the oncolytic virus and helps disseminate the agent to adjacent tumor cells. We have described previously such a conditionally replicative adenovirus, called Delta-24, which expresses a mutant E1A protein that is unable to bind to Rb (1). Because of this inability to bind to Rb, Delta-24 behaves like a wild-type adenovirus in cancer cells but does not replicate efficiently in nondividing normal cells. It has been reported that adenoviruses infect primarily quiescent cells and then induce them to enter the S phase of the cell cycle so that viral DNA synthesis can occur (2, 3). This ability to induce quiescent cells to enter the S phase makes these viruses attractive for use with agents, such as topoisomerase I inhibitors, which target cells in the S phase. Of particular interest, Delta-24 induces the accumulation of infected cancer cells in the S phase (1).Previ...

The oncolytic adenovirus AdΔΔ enhances selective cancer cell killing in combination with DNA-damaging drugs in pancreatic cancer models

“…4,9,26,38,40,42,43 Here, we demonstrate that the potency of AdDD was increased in combination with both gemcitabine and irinotecan. In previous studies we found that AdD19K in PT45 and SUIT-2 cells could enhance gemcitabine-induced apoptosis and that AdDD interacted synergistically with docetaxel in prostate cancer cells.…”

“…31 This deletion restricts replication mainly to cancer cells as demonstrated for E1ACR2-deleted viruses. 21,[37][38][39][40] The additional E1B19K deletion also attenuates viral replication in normal cells through abortive replication in response to extrinsically induced apoptosis. 28,29,35,36 Therefore, the double-deleted AdDD mutant has two viral functions deactivated to prevent amplification in normal tissue while potent replication and spread can proceed in pancreatic tumors that frequently have both deregulated cell cycle and apoptosis pathways.…”

“…It was previously reported that a single-deleted E1ACR2-deletion mutant could also enhance the antitumor effect of irinotecan in glioma cells. 40 Treatment of gemcitabine-resistant pancreatic cancers with low doses of irinotecan in combination with AdDD, therefore, seems a promising future option.…”

Targeting glioblastoma with oncolytic adenovirus delta 24

“…Treatment to glioma with Ad-Δ24 or its derivatives has been observed to enhance when combined with TRAIL, [16] adenovirus expressing p53, [22] temozolomide, [23] radiation [24] and topoisomerase I inhibitor irinotecan. [25] Autophagic induced cell death and induction of apoptosis are well-characterized results of Ad-Δ24 infection giving the erratum for combination treatments. [26] ANTITUMOR IMMUNE RESPONSE Another important aspect of oncolytic virotherapy is the induction of augmented antitumor immune response.…”

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

“…50 Equally, the combination of Delta-24 with irinotecan (CPT-11) showed an enhanced anticancer effect, suggesting that Delta-24 could sensitize glioma cells to the topoisomerase I inhibitor irinotecan. 51 Delta-24-RGD, in combination with everolimus (RAD001), resulted in an enhanced antiglioma effect in vivo via autophagy and increased long-term survival of glioma-bearing animals. 52 Combination of ICOVIR-5 with RAD001 or TMZ showed a potent antiglioma effect both in vitro and in vivo in athymic mice bearing glioma xenografts.…”