Abstract 3748: Virally enhanced p53 reactivation impairs KRAS-driven pancreatic cancer invasion
Authors: Koujima Takeshi , Tazawa Hiroshi , Ieda Takeshi , Kuwada Kazuya , Tanimoto Terutaka , Kuroda Shinji , Kishimoto Hiroyuki , Nishizaki Masahiko , Urata Yasuo , Kagawa Shunsuke , Fujiwara Toshiyoshi 
Published: July 2016

Background: Pancreatic ductal adenocarcinoma (PDAC) is the worst prognosis disease with an overall 5-year survival rate of less than 5%. More than 80% of patients are not eligible for curative surgical resection due to extensive local tumor invasion and early systemic metastasis at the time of diagnosis. Moreover, even after curative surgery, PDAC patients still have poor prognosis due to local recurrence and systemic metastasis. Although activation of oncogenic KRAS is implicated in the initiation, promotion and progression of pancreatic cancer, the development of cancer treatment targeting KRAS remains unsuccessful. Moreover, tumor suppressor p53 is also frequently inactivated in PDAC patients. We recently developed two types of tumor-specific replication-competent oncolytic adenoviruses, OBP-301 and OBP-702, which is modified OBP-301 to express tumor suppressor p53 protein. In this study, we investigated whether oncolytic adenoviruses inhibit cell viability, migration, invasion and KRAS-driven signaling pathway in PDAC cells.

Methods: We used 4 PDAC cells (MIA PaCa-2, Capan-1, Panc-1, BxPC-3). The cell viability was examined by XTT assay. Migration and invasion properties were assessed using transwell chamber assay. The modulation of KRAS-driven signaling pathway was investigated by Western blot analysis.

Results: OBP-301 induced moderate antitumor effect in MIA Paca-2, Capan-1 and BxPC-3 cells and strong antitumor effect in Panc-1 cells in a dose-dependent manner, whereas OBP-702 induced profound antitumor effect in all human PDAC cells, suggesting the broad spectrum of OBP-702's efficacy. OBP-301 induced autophagy-related cell death, whereas OBP-702 induced autophagy- and apoptosis-related cell deaths. In migration and invasion assays, MIA Paca-2 and Capan-1 cells were low-invasive type, and Panc-1 and BxPC-3 cells were high-invasive type. OBP-301 and OBP-702 inhibited migration and invasion properties of high-invasive type PDAC cells, and the inhibitory effect of OBP-702 was stronger than that of OBP-301. We also found that oncolytic adenoviruses inhibited the expression of KRAS and KRAS-downstream target MEK/ERK proteins in high-invasive type PDAC cells.

Conclusions: Our results suggest that oncolytic adenoviruses, OBP-301 and OBP-702, inhibit the survival and invasive phenotype of pancreatic cancer by suppressing KRAS-driven signaling pathway and reactivating p53-driven signaling pathway. In vivo experiments are under way to investigate the anti-tumor and anti-invasive effects of oncolytic adenoviruses using BxPC-3 xenograft tumors. The clinical trial of intratumoral administration of oncolytic adenoviruses in patients with invasive PDAC should be also warranted.

Citation Format: Takeshi Koujima, Hiroshi Tazawa, Takeshi Ieda, Kazuya Kuwada, Terutaka Tanimoto, Shinji Kuroda, Hiroyuki Kishimoto, Masahiko Nishizaki, Yasuo Urata, Shunsuke Kagawa, Toshiyoshi Fujiwara. Virally enhanced p53 reactivation impairs KRAS-driven pancreatic cancer invasion. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3748.