Abstract 2448: Suppression of MYCN-driven neuroblastoma malignant phenotype by telomerase-targeted tumor suppressor p53 transactivation

Abstract

Abstract Background: Neuroblastoma (NB) is a primary malignant tumor in the peripheral sympathetic nervous system. High-risk group of NB has an unfavorable clinical course, even after treatment with current chemotherapy regimens and aggressive surgical resection. Therefore, a novel therapeutic strategy is needed for the treatment of high-risk group of NB. Recent accumulating evidences in whole-genome sequencing analysis have shown that human telomerase reverse transcriptase (hTERT) gene rearrangement and MYCN gene amplification are predictive biomarkers for the high-risk group of NB, in which massive transcriptional activation of hTERT mRNA was frequently observed. We recently developed two types of hTERT-driven oncolytic adenoviruses, OBP-301 and OBP-702, in which the hTERT promoter drives the expression of the viral E1A and E1B genes for tumor-specific virus replication, and OBP-702 further expresses tumor suppressor p53 protein. In this study, we investigated whether OBP-301 and OBP-702 inhibit cell viability and MYCN protein expression in human NB cells with different MYCN status. Methods: We used 3 human NB cell lines with or without MYCN amplification, including IMR-32 (MYCN-amplified), LA-N-5 (MYCN-amplified), SK-N-SH (MYCN-not amplified). The antitumor effects of OBP-301, OBP-702, and Ad-p53, a replication-defective adenovirus expressing p53 gene, were evaluated using XTT assay. Virus-induced apoptosis and MYCN suppression were analyzed by Western blot analysis. Results: OBP-301, OBP-702, and Ad-p53 suppressed the viability of all 3 NB cell lines, whereas OBP-702 showed the most profound anti-tumor effect especially in MYCN-amplified NB cells. OBP-702 induced higher p53 expression than Ad-p53, resulting in the p53-mediated apoptotic cell death. Although MYCN expression in NB cells with MYCN amplification was downregulated after infection with all types of adenoviruses, the inhibitory effect of OBP-702 was the strongest among these adenoviruses. Conclusions: These results suggest that a hTERT-driven oncolytic adenovirus OBP-702 is a promising antitumor agent to induce profound apoptotic cell death through p53 transactivation and MYCN suppression in human NB cells with or without MYCN amplification. In vivo experiments are under way to investigate the antitumor effect of OBP-702 against xenograft NB tumors. Citation Format: Terutaka Tanimoto, Hiroshi Tazawa, Hiroshi Noso, Takanori Oyama, Yasuo Urata, Shunsuke Kagawa, Takuo Noda, Toshiyoshi Fujiwara. Suppression of MYCN-driven neuroblastoma malignant phenotype by telomerase-targeted tumor suppressor p53 transactivation. [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 2448.