Abstract 3322: Chronology and risk-dependence of age-related remodelling of oesophageal epithelia
Authors: Yokoyama Akira , Kakiuchi Nobuyuki , Yoshizato Tetsuichi , Nannya Yasuhito , Suzuki Hiromichi , Takeuchi Yasuhide , Shiozawa Yusuke , Sato Yusuke , Aoki Kosuke , kim Soo , Fujii Yoichi , Yoshida Kenichi , Kataoka Keisuke , Nakagawa Masahiro M. , Inoue Yoshikage , Hirano Tomonori , Shiraishi Yuichi , Chiba Kenichi , Tanaka Hiroko , Sanada Masashi , Ohashi Shinya , Miyamoto Shin’ichi , Tsunoda Shigeru , Mimori Koshi , Minamiguchi Sachiko , Miyano Satoru , Makishima Hideki , Muto Manabu , Ogawa Seishi 
Published: August 2019

Abstract
Clonal expansion in aged normal tissues has been implicated in cancer development. However, its chronology and risk-dependence are poorly understood. Esophageal squamous cell carcinoma (ESCC) is a predominant esophageal cancer among Asian populations and substantially affected by heavy smoking and drinking, likely through a ‘field effect’. To elucidate the role of these lifestyle risks on ESCC development, we investigated clonal expansion in physiologically normal esophageal epithelia (PNE) using multiple microscale sampling, as small as 0.2 mm2 in size, followed by an unbiased detection of somatic mutations with whole exome sequencing. Mutations were detected in most of PNE samples (151/157), where none of the mutations were shared between samples collected &gt;10 mm apart. The number of mutations and their allele frequency increased with age, suggesting age-related clonal expansion in PNE (ARCE), which was significantly promoted by heavy smoking and drinking. Mutations were dominated by age-related patterns and a still poorly-defined, ‘esophagus-specific signature, as well as a COSMIC 16-like signature. The latter has recently been related to alcohol drinking and was enriched in high-risk samples, which was confirmed by whole genome sequencing of single cell-derived colonies. As many as 10 genes were significantly mutated or positively selected in ARCE. Among most commonly affected genes were NOTCH1, TP53, FAT1, PPM1D, NOTCH2, and NOTCH3, which substantially differed from those in ESCC, showing prominent over-representation of NOTCH1, PPM1D, FAT1 and NOTCH2, and significant underrepresentation of TP53, NFE2L2, and CDKN2A were significantly underrepresented, suggesting different mechanisms of positive selection between ARCE and ESCC. Driver mutations were detected more frequently and in higher numbers in high-risk PNE samples than low-risk ones, with accentuated NOTCH1, TP53 and PPM1D mutations. Analyses of densely collected micro-scale samples (0.2 mm2) disclosed fine structure of ARCE with its chronological history. Driver-mutated clones emerge multifocally from early childhood as early as &lt;2 years and accompanying their own phylogenetic structures, increase their number and size with aging, ultimately replacing almost entire oesophageal epithelia in the extreme elderly. In conclusion, remodelling of oesophageal epithelia by driver-mutated clones is an inevitable consequence of normal aging, impacting cancer development depending on lifestyle.
Citation Format: Akira Yokoyama, Nobuyuki Kakiuchi, Tetsuichi Yoshizato, Yasuhito Nannya, Hiromichi Suzuki, Yasuhide Takeuchi, Yusuke Shiozawa, Yusuke Sato, Kosuke Aoki, Soo kim, Yoichi Fujii, Kenichi Yoshida, Keisuke Kataoka, Masahiro M. Nakagawa, Yoshikage Inoue, Tomonori Hirano, Yuichi Shiraishi, Kenichi Chiba, Hiroko Tanaka, Masashi Sanada, Shinya Ohashi, Shin’ichi Miyamoto, Shigeru Tsunoda, Koshi Mimori, Sachiko Minamiguchi, Satoru Miyano, Hideki Makishima, Manabu Muto, Seishi Ogawa. Chronology and risk-dependence of age-related remodelling of oesophageal epithelia [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 3322.