Abstract 4330: Activation of <i>AZIN1</i> RNA editing facilitates and promotes invasive potential of cancer associated fibroblasts in colorectal cancer
Authors: Sho Takeda, Kunitoshi Shigeyasu, Yoshinaga Okugawa, Kazuhiro Yoshida, Yoshiko Mori, Shuya Yano, Kazuhiro Noma, Yuzo Umeda, Yoshitaka Kondo, Hiroyuki Kishimoto, Fuminori Teraishi, Hiroshi Tazawa, Shunsuke Kagawa, Ajay Goel, Toshiyoshi Fujiwara
Journal: Cancer Research (2019)

Abstract Colorectal cancer (CRC) is a common malignancy worldwide and remains the second leading cause of cancer-related deaths in Western countries. Emerging evidence demonstrates that such lifestyle choices profoundly impact various epigenetic modifications, and lead to cancer.Adenosine-to-inosine (A-to-I) RNA editing is an epigenetic modification mediated by Adenosine Deaminases that act on the RNA (ADAR), and has recently been discovered to be dysregulated in human cancers. However, the clinical significance and the functional role of RNA editing in cancer-associated fibroblasts (CAFs) remains unclear. By systematically analyzing a large cohort of 627 CRC specimens, we investigated the expression pattern of ADAR1 and the its biological significance on the antizyme inhibitor 1(AZIN1)RNA editing levels, which is one of the most frequently edited genes in cancers. Both ADAR1 expression and AZIN1RNA editing levels were significantly elevated in CRC tissues vs. normal mucosa, and these findings correlated with the increased expression of mesenchymal markers, Vimentin (ρ=0.44) and Fibroblast activation protein (ρ=0.38). ADAR1 was specifically upregulated in consensus molecular subtype 4 (CMS4) CRCs, which have mesenchymal characteristics and associate with poor prognosis.Intriguingly, ADAR1 was overexpressed in both cancer cells and fibroblasts from cancerous lesions. We next assessed whether cancer cells can promote ADAR1 expression and enhance AZIN1RNA editing in fibroblasts. Fibroblasts were cultured in the conditioned medium (CM) derived from CRC cells. Fibroblasts cultured with such CM expressed ADAR1 at significantly higher levels when compared to controls. Likewise, the overexpression of ADAR1 was associated with corresponding increase in AZIN1RNA editing. Overexpression of edited AZIN1RNA enhanced invasiveness of fibroblasts relative to wild-type AZIN1(p=0.0079).Previously the oncogene, ODC, was identified as a downstream target of edited AZIN1. The overexpression of edited AZIN1RNA resulted in upregulation of ODC protein in fibroblasts, confirming that edited AZIN1RNA stabilizes ODC more effectively than its wild-type counterpart in fibroblasts. In the previous study, ODC was reported to be the promoter of invasive potential in fibroblasts. Our results suggest that edited AZIN1RNA may promote invasion of fibroblasts via accumulation of ODC.This study is the first to investigate the clinical significance of ADAR1 expression and the degree of AZIN1RNA editing in colorectal CAFs, along with the determination the functional role of AZIN1RNA editing in this malignancy. Taken together, our study suggests that overexpression of ADAR1 in cancer lesion promotes malignant potential in CRC. We present novel evidence that ADAR1 is overexpressed in fibroblasts and may facilitate invasive potential in cancerous lesions in CRC microenvironment. Citation Format: Sho Takeda, Kunitoshi Shigeyasu, Yoshinaga Okugawa, Kazuhiro Yoshida, Yoshiko Mori, Shuya Yano, Kazuhiro Noma, Yuzo Umeda, Yoshitaka Kondo, Hiroyuki Kishimoto, Fuminori Teraishi, Hiroshi Tazawa, Shunsuke Kagawa, Ajay Goel, Toshiyoshi Fujiwara. Activation of AZIN1 RNA editing facilitates and promotes invasive potential of cancer associated fibroblasts in colorectal 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 4330.