Recombinant Vaccinia Viruses Coding Transgenes of Apoptosis-Inducing Proteins Enhance Apoptosis But Not Immunogenicity of Infected Tumor Cells.

Olga Koval,Vladimir Richter,Anastasiya Tkachenko,Antonina Grazhdantseva,Olga Troitskaya,Anna Nushtaeva,Galina Sivolobova,Galina Kochneva,Elena Kuligina

doi:10.1155/2017/3620510

Abstract

Genetic modifications of the oncolytic vaccinia virus (VV) improve selective tumor cell infection and death, as well as activation of antitumor immunity. We have engineered a double recombinant VV, coding human GM-CSF, and apoptosis-inducing protein apoptin (VV-GMCSF-Apo) for comparing with the earlier constructed double recombinant VV-GMCSF-Lact, coding another apoptosis-inducing protein, lactaptin, which activated different cell death pathways than apoptin. We showed that both these recombinant VVs more considerably activated a set of critical apoptosis markers in infected cells than the recombinant VV coding GM-CSF alone (VV-GMCSF-dGF): these were phosphatidylserine externalization, caspase-3 and caspase-7 activation, DNA fragmentation, and upregulation of proapoptotic protein BAX. However, only VV-GMCSF-Lact efficiently decreased the mitochondrial membrane potential of infected cancer cells. Investigating immunogenic cell death markers in cancer cells infected with recombinant VVs, we demonstrated that all tested recombinant VVs were efficient in calreticulin and HSP70 externalization, decrease of cellular HMGB1, and ATP secretion. The comparison of antitumor activity against advanced MDA-MB-231 tumor revealed that both recombinants VV-GMCSF-Lact and VV-GMCSF-Apo efficiently delay tumor growth. Our results demonstrate that the composition of GM-CSF and apoptosis-inducing proteins in the VV genome is very efficient tool for specific killing of cancer cells and for activation of antitumor immunity.

Highlights

Oncolytic viruses are novel multifunctional anticancer agents with increasingly promising outcomes in patients [1]
The vaccinia virus has been shown to preferably trigger programmed necrosis we reported in our previous investigation that the double recombinant vaccinia virus VV-GMCSF-Lact, coding proapoptotic protein lactaptin and human GM-CSF, induced cancer cell death with caspase-3 and caspase-7 activation [6, 24]
The GM-CSF sequence was inserted into the structural part of the viral thymidine kinase gene, and the apoptin sequence was inserted into the vaccinia growth factor gene deleted region

Summary

Introduction

Oncolytic viruses are novel multifunctional anticancer agents with increasingly promising outcomes in patients [1] They can directly lyse tumor cells and be vectors coding specific molecules (proteins or RNAs with regulatory functions), which assist in killing or inhibiting the growth of tumor cells, and stimulate the immune system [2]. Viral proteins interact with a number of intracellular signaling pathways; it is expected that they have the potential to regulate various cell death modalities. These include apoptosis, necrosis, necroptosis, pyroptosis, and autophagic cell death, often with one as the predominant form of death for a particular OV [3]. Since OVs usually code many proteins, helping viruses to avoid host immune response, various recombinant OVs

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