Abstract
BackgroundImprovement of transduction and augmentation of cytotoxicity are crucial for adenoviruses (Ad)-mediated gene therapy for cancer. Down-regulated expression of type 5 Ad (Ad5) receptors on human tumors hampered Ad-mediated transduction. Furthermore, a role of the p53 pathways in cytotoxicity mediated by replication-competent Ad remained uncharacterized.MethodsWe constructed replication-competent Ad5 of which the E1 region genes were activated by a transcriptional regulatory region of the midkine or the survivin gene, which is expressed preferentially in human tumors. We also prepared replication-competent Ad5 which were regulated by the same region but had a fiber-knob region derived from serotype 35 (AdF35). We examined the cytotoxicity of these Ad and a possible combinatory use of the replication-competent AdF35 and Ad5 expressing the wild-type p53 gene (Ad5/p53) in esophageal carcinoma cells. Expression levels of molecules involved in cell death, anti-tumor effects in vivo and production of viral progenies were also investigated.ResultsReplication-competent AdF35 in general achieved greater cytotoxic effects to esophageal carcinoma cells than the corresponding replication-competent Ad5. Infection with the AdF35 induced cleavages of caspases and increased sub-G1 fractions, but did not activate the autophagy pathway. Transduction with Ad5/p53 in combination with the replication-competent AdF35 further enhanced the cytotoxicity in a synergistic manner. We also demonstrated the combinatory effects in an animal model. Transduction with Ad5/p53 however suppressed production of replication-competent AdF35 progenies, but the combination augmented Ad5/p53-mediated p53 expression levels and the downstream pathways.ConclusionsCombination of replication-competent AdF35 and Ad5/p53 achieved synergistic cytotoxicity due to enhanced p53-mediated apoptotic pathways.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-015-1482-8) contains supplementary material, which is available to authorized users.
Highlights
Improvement of transduction and augmentation of cytotoxicity are crucial for adenoviruses (Ad)-mediated gene therapy for cancer
Viability of esophageal carcinoma cells that were treated with various doses of Type 5 adenoviruses (Ad5)/MK, a fiber-knob region derived from serotype 35 (AdF35)/MK, Ad5/LacZ or AdF35/LacZ was examined with the WST assay
In this study, we demonstrated that replication-competent AdF35 regulated by an exogenous transcriptional regulatory region induced apoptotic cell death in esophageal carcinoma and that combination of the AdF35 and Ad5 expressing the wild-type p53 gene (Ad5/p53) produced synergistic cytotoxicity through enhanced activation of the p53 pathways
Summary
Improvement of transduction and augmentation of cytotoxicity are crucial for adenoviruses (Ad)-mediated gene therapy for cancer. Down-regulated expression of type 5 Ad (Ad5) receptors on human tumors hampered Ad-mediated transduction. Adenoviruses (Ad)-mediated gene transfer is a possible strategy to improve the prognosis by transducing the tumor cells. The AdF35 can thereby be a vector to transduce low CAR-expressing cells which are resistant to Ad5 infection. The differential receptor usage has an advantage in simultaneously transferring dual genes into the same target cells. Ad5 infection downregulated CAR expression levels on target cells through receptor internalization and hampered subsequent Ad5mediated transduction. AdF35-mediated transduction was not impaired by precedent Ad5 infection since the down-regulated receptor expression was exclusive each other [7]
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