Abstract 3356: Novel evidence for AZIN1 RNA editing-mediated oncogenic role in colorectal cancer

Abstract

Abstract Introduction: Colorectal cancer (CRC) is the third most frequent malignancy in males and second most common disease in females worldwide. CRC pathogenesis is intimately associated to lifestyles, such as diet, obesity, and smoking. Multiple evidences have revealed that these risk factors can trigger specific epigenetic alterations and subsequently promote carcinogenesis. Recently, adenosine (A)-to-inosine (I) RNA editing has been shown to be a potential epigenetic event in human cancers. One of the most important RNA editing gene targets is the antizyme inhibitor 1 (AZIN1), and edited AZIN1 promotes accumulation of ornithine decarboxylase and polyamines, leading to promotion and development of carcinogenesis. However, the oncogenic role and the clinical significance of RNA editing in CRC has not been investigated, which led us to undertake this present study. Materials and methods: We systematically and comprehensively investigated RNA editing in the AZIN1 gene using the RNA editing site specific PCR (RESSqPCR) in CRC patients. We further validates these results using multiple independent cohorts of CRC patients comprising of 329 colorectal cancer and adenoma patients. In addition, we performed a series of functional assays to elucidate the functional role of AZIN1 RNA editing in CRC pathogenesis. Results: Using RESSqPCR, AZIN1 RNA editing levels were analyzed in two CRC cohorts. AZIN1 editing levels were significantly higher in cancer tissues at all stages (I thru IV) compared with normal mucosa. Additionally, AZIN1 was highly edited in colorectal adenoma tissues compared to adjacent normal mucosa, suggesting this epigenetic event to be critical in normal-adenoma-carcinoma cascade. Additionally, the expression of RNA editing enzyme (ADAR1) was also upregulated in cancerous tissues compared to normal mucosa, and positively correlated with AZIN1 editing levels. To interrogate whether AZIN1 editing has an oncogenic role, overexpression of edited-AZIN1 in CRC cell lines resulted in increased cell proliferation, invasion, migration, and stemness. More importantly, AZIN1 editing was significantly enhanced in cancer stem cells, suggesting its importance for the development and maintenance of stemness features. Finally, establishment of xenograft tumors in an animal model resulted in significantly larger tumors in edited vs. wild type-AZIN1 groups. Taken together, these results highlight the oncogenic role of AZIN1 RNA editing in CRC. Conclusion: Our systematic and comprehensive study, which is first of its kind, reveals that AZIN1 RNA editing is novel epigenetic alteration that promotes an oncogenic behavior in colorectal cancer. In addition to its functional role, AZIN1 editing levels may be one of the important facilitators of adenoma-carcinoma sequence in CRC and serve as an important clinical biomarker in this disease. Citation Format: Kunitoshi Shigeyasu, Shusuke Toden, Yoshinaga Okugawa, Jinsei Miyoshi, Takeshi Nagasaka, Toshiyoshi Fujiwara, Leilei Chen, Ajay Goel. Novel evidence for AZIN1 RNA editing-mediated oncogenic role in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3356. doi:10.1158/1538-7445.AM2017-3356