420. Improvement of Antitumor Activity in Intraperitoneal Ovarian Cancer Model by a Noble Cloned Carrier Cell Infected with Oncolytic Adenovirus

Abstract

Infection inhibition of virus by antiviral antibodies is one of the major problems that cancer gene therapy has never shown the significant antitumor activity in human clinical trial. Oncolytic adenovirus-infected A549 carrier cells develop cell fragments and exosomes containing oncolytic adenoviral particles and could infect target cancer cells by overcoming antiadenoviral immunogenicity. A549 carrier cells induce complete tumor reduction in syngeneic subcutaneous mouse tumor model by direct antitumor activity of oncolytic adenovirus, antiadenoviral cytotoxic T lymphocyte and antitumor immunity but not in syngeneic intraperitoneal ovarian cancer mouse model. In this study, we cloned and established a noble carrier cell by limiting dilution to induce the complete tumor reduction of the intraperitoneal ovarian tumor by increasing antitumor activity of carrier cells. Oncolytic adenovirus AdE3-midkine driven by midkine promoter and non-replicative adenovirus Ad-mGM-CSF were used in this study. We cloned a nobel carrier cell from EHMK adenocarcinoma cells by limiting dilution, which were established in our laboratory. EHMK cells were infected with AdE3-midkine and co-cultured with ovarian adenocarcinoma HEY cells with or without antiadenoviral antibodies. In vitro antitumor activity of cloned EHMK carrier cells was calculated by IC50 and compared with that of A549 carrier cells infected with AdE3-midkine. B6C3F1 mouse and cognate ovarian cancer OVHM cell line were used in this study. Mice were injected intraperitoneally with OVHM cells after immunization with adenovirus and treated by carrier cells infected with AdE-midkine with or without Ad-mGM-CSF. Antitumor activity of carrier cells was analyzed by Kaplan Meier survival curve. In vitro antitumor activity of EHMK carrier cells was 1.0±0.1 and 1.1±0.2 that of A549 carrier cells with or without antiadenoviral antibodies, respectively. In vitro antitumor activity of EHMK-51 carrier cells after limiting dilution of EHMK cells was 4.5±1.1 and 3.4±1.9 that of A549 carrier cells with or without antiadenoviral antibodies, respectively. EMHK-51 cells were further cloned by limiting dilution. In vitro antitumor activity of EHMK-51-35 carrier cells was 3.1±1.5 and 2.8±0.9 that of EHMK-51 carrier cells with or without antiadenoviral antibodies, respectively. In comparison with A549 carrier cells, in vitro antitumor activity of EHMK-51-35 carrier cells was 12.5±4.3 and 10.5±5.0 that of A549 carrier cells with or without antiadenoviral antibodies, respectively. In mouse intraperitoneal tumor model, A549 carrier cells infected with AdE3-midkine ± Ad-mGM-CSF did not show any antitumor effect but EHMK carrier cells infected with AdE3-midkine with or without Ad-mGM-CSF showed 40% and 70% complete tumor reduction, respectively. From these results, it is concluded that EHMK-51-35 carrier cells might be potent to treat intraperitoneally metastasized ovarian cancer