Abstract 761: Integrated environmental, lifestyle, and epigenetic risk prediction of primary gastric cancer
Authors: Usui Genki , Matsusaka Keisuke , Huang Kie K. , Zhu Feng , Shinozaki Tomohiro , Fukuyo Masaki , Rahmutulla Bahityar , Yogi Norikazu , Okada Tomoka , Seki Motoaki , Sakai Eiji , Fujibayashi Kazutoshi , Tsao Stephen K. , Khor Christopher , Ang Tiing L. , Abe Hiroyuki , Matsubara Hisahiro , Fukayama Masashi , Gunji Toshiaki , Matsuhashi Nobuyuki , Morikawa Teppei , Ushiku Tetsuo , Yeoh Khay G. , Tan Patrick , Kaneda Atsushi 
Published: April 2023

Abstract
Aberrant DNA methylation accumulates in non-malignant gastric mucosa after exposure to environmental pathogens such as H. pylori (HP). To understand how environmental factors and DNA methylation interplay to influence primary gastric cancer (GC) risk, we performed an integrated analysis of clinical factors and DNA methylation data of gastric tissues from a longitudinally monitored cohort in Japan, with validation in a separate cohort from Singapore. The Japanese check-up cohort included 4,234 healthy subjects who underwent gastric mucosal biopsy. The median observation period was 4.2 years, and 77 subjects developed GC. GC incidence correlated with age, drinking, smoking, GC family history, and HP status in the multivariable Cox model. Next, we conducted comprehensive DNA methylation analysis using Infinium MethylationEPIC arrays on gastric tissues (n=164), including (1) mucosal biopsies from subjects who later developed GC (“future GC patients”), (2) mucosal biopsies from HP(+) subjects who did not later develop GC (“future non-GC subjects”), (3) mucosal biopsies from future non-GC HP(−) subjects (“control mucosae”), and (4) GCs and surrounding mucosae. Infinium data of gastric mucosae (n=137) collected in the GCEP cohort (Singapore) were also analyzed. DNA methylation of promoter region observed in GCs, accumulated not only in mucosae adjacent to GCs but also in the biopsy mucosae of future GC patients. Mucosae of future non-GC subjects were more methylated than control mucosae but less methylated than mucosae of future GC patients. Similar findings were observed in the GCEP cohort. DNA methylation levels were associated with clinical factors and histopathological alterations - however, in multivariable analyses, DNA methylation remained an independent GC risk factor. Methylation levels were predictive of not only higher GC risk but also a shorter period to GC incidence. We then focused on the associations between environmental factors and methylation. Heavy drinking and smoking were associated with the accumulation of DNA methylation only in HP(+) subjects. The increases in methylation over time in subjects who quit smoking were significantly attenuated compared to continuous smokers. These results suggest that pro-carcinogenic epigenetic alterations initiated by HP exposure are amplified by unfavorable but modifiable lifestyle choices. Furthermore, target genes methylated by each environmental factor may overlap in part; however, they were not necessarily methylated similarly, suggesting that the best markers for stratifying GC risk may differ for each subgroup classified by exposure to environmental factors. Indeed, candidate markers for stratifying GC risk overlapped among subgroups, whereas markers unique to each subgroup were also identified, highlighting the potential of integrating environmental, lifestyle, and epigenetic information to inform GC precision prevention.
Citation Format: Genki Usui, Keisuke Matsusaka, Kie K. Huang, Feng Zhu, Tomohiro Shinozaki, Masaki Fukuyo, Bahityar Rahmutulla, Norikazu Yogi, Tomoka Okada, Motoaki Seki, Eiji Sakai, Kazutoshi Fujibayashi, Stephen K. Tsao, Christopher Khor, Tiing L. Ang, Hiroyuki Abe, Hisahiro Matsubara, Masashi Fukayama, Toshiaki Gunji, Nobuyuki Matsuhashi, Teppei Morikawa, Tetsuo Ushiku, Khay G. Yeoh, Patrick Tan, Atsushi Kaneda. Integrated environmental, lifestyle, and epigenetic risk prediction of primary gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 761.