Abstract 2979: Boosting replication and penetration of telomerase-specific replicative virus by paclitaxel induces synthetic lethality in peritoneal metastasis of gastric cancer

Abstract

Abstract Background: Peritoneal metastasis is the most frequent form of distant metastasis and recurrence in gastric cancer and its prognosis is extremely poor. A promising result in phase III trial using intraperitoneal (i.p.) paclitaxel (PTX) for the peritoneal metastasis of gastric cancer has been reported in recent year; however, it is not sufficiently effective to eradicate disseminated gastric cancer. In this study, we investigated whether novel i.p. oncolytic virotherapy could be synthetically lethal with PTX for the peritoneal metastasis of gastric cancer. Methods: OBP-401 (TelomeScan) is a green fluorescence protein (GFP)-expressing attenuated adenovirus with oncolytic potency that is driven by telomerase promoter. We assessed its synergistic effect with PTX using human gastric cancer cell lines (GCIY and KATO III) and xenograft peritoneal metastasis model. The mechanism underlying the synergistic antitumor effect was evaluated by in vitro viral replication, induction of mitotic catastrophe, and in vivo viral penetration into disseminated nodules. Results: OBP-401 synergistically suppressed the viability of human gastric cancer cells in combination with PTX. PTX was synthetically lethal with OBP-401 by enhancing viral replication ability in cancer cells and the combination therapy increased mitotic catastrophe induction, resulted in accelerating autophagy and apoptosis. Peritoneally disseminated nodules were selectively visualized as GFP-positive spots by the i.p. administration of OBP-401 in the orthotopic human gastric cancer peritoneal dissemination model. And, PTX enhanced the penetration of OBP-401 deeply into the disseminated nodules. Moreover, non-invasive in vivo imaging system (IVIS) demonstrated that the combination therapy of i.p. OBP-401 administration with PTX significantly inhibited tumor growth of peritoneal metastasis and the amount of malignant ascites. Conclusions: Intraperitoneal virotherapy with PTX may be a promising treatment strategy for the peritoneal metastasis of gastric cancer. Clinical trials to obtain the proof of concept are warranted in peritoneally disseminated gastric cancer patients. Citation Format: Toshihiro Ogawa, Satoru Kikuchi, Wataru Ishikawa, Hiroshi Tazawa, Motoyasu Tabuchi, Shinji Kuroda, Kazuhiro Noma, Masahiko Nishizaki, Shunsuke Kagawa, Yasuo Urata, Toshiyoshi Fujiwara. Boosting replication and penetration of telomerase-specific replicative virus by paclitaxel induces synthetic lethality in peritoneal metastasis of gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2979.