Engineering of double recombinant vaccinia virus with enhanced oncolytic potential for solid tumor virotherapy

// Galina Kochneva 1, 2 , Galina Sivolobova 1, 2 , Anastasiya Tkacheva 1, 2 , Antonina Grazhdantseva 1, 2 , Olga Troitskaya 1, 3 , Anna Nushtaeva 1 , Anastasiya Tkachenko 1 , Elena Kuligina 1 , Vladimir Richter 1 , Olga Koval 1, 3 1 Institute of Chemical Biology and Fundamental Medicine SB RAS, Novosibirsk, Russia 2 State Research Center of Virology and Biotechnology “Vector”, Koltsovo, Russia 3 Novosibirsk State University, Novosibirsk, Russia Correspondence to: Olga Koval, email: o.koval@niboch.nsc.ru Keywords: vaccinia virus, chemoresistant tumor, apoptosis, lactaptin, GM-CSF Received: June 03, 2016     Accepted: September 21, 2016     Published: September 30, 2016 ABSTRACT Vaccinia virus (VACV) oncolytic therapy has been successful in a number of tumor models. In this study our goal was to generate a double recombinant vaccinia virus (VV-GMCSF-Lact) with enhanced antitumor activity that expresses exogenous proteins: the antitumor protein lactaptin and human granulocyte-macrophage colony-stimulating factor (GM-CSF). Lactaptin has previously been demonstrated to act as a tumor suppressor in mouse hepatoma as well as MDA-MB-231 human adenocarcinoma cells grafted into SCID mice. VV-GMCSF-Lact was engineered from Lister strain (L-IVP) vaccinia virus and has deletions of the viral thymidine kinase and vaccinia growth factor genes. Cell culture experiments revealed that engineered VV-GMCSF-Lact induced the death of cultured cancer cells more efficiently than recombinant VACV coding only GM-CSF (VV-GMCSF-dGF). Normal human MCF-10A cells were resistant to both recombinants up to 10 PFU/cell. The selectivity index for breast cancer cells measured in pair cultures MCF-7/MCF-10A was 200 for recombinant VV-GMCSF-Lact coding lactaptin and 100 for VV-GMCSF-dGF. Using flow cytometry we demonstrated that both recombinants induced apoptosis in treated cells but that the rate in the cells with active caspase-3 and -7 was higher after treatment with VV-GMCSF-Lact than with VV-GMCSF-dGF. Tumor growth inhibition and survival outcomes after VV-GMCSF-Lact treatment were estimated using immunodeficient and immunocompetent mice models. We observed that VV-GMCSF-Lact efficiently delays the growth of sensitive and chemoresistant tumors. These results demonstrate that recombinant VACVs coding an apoptosis-inducing protein have good therapeutic potential against chemoresistant tumors. Our data will also stimulate further investigation of coding lactaptin double recombinant VACV in clinical settings.