Prospective metabolomics investigation of gastric cancer risk in African Americans and European Whites with a low socioeconomic status

ABSTRACT Gastric cancer is one of the most common and deadly cancers globally, accounting for over one million new cancer diagnoses and 783,000 deaths in 2018. Infection of Helicobacter pylori (H. pylori) is the most important risk factor and a necessary cause for non-cardia gastric cancer. While targeting high-risk populations who are

infected with H. pylori seems a compelling strategy for gastric cancer screening and prevention, a significant concern not addressed is that only ~1 to 3% of the H. pylori infected individuals develop gastric cancer, indicating that such strategy based on H. pylori status alone is insufficient, particularly among populations with a relatively

low prevalence of H. pylori infection. Thus, discovering and validating additional biomarkers, especially non- invasive ones, are needed to facilitate the development of novel risk assessment tools for gastric cancer. The human metabolome reflects endogenous responses and processes to exposures, including environmental and

lifestyle factors that are related to carcinogenesis. The use of advanced metabolomics techniques in prospective population-based cohort studies have successfully identified both novel etiologic factors and risk biomarkers for different cancers. However, few prior studies have focused on identifying novel risk biomarkers for gastric cancer

using metabolomics techniques, particularly in prospective design settings. We recently conducted the first nested case-control study within two large prospective cohorts. Our study identified 5 metabolites associated with risk of gastric cancer after correction for multiple comparisons and 13 additional metabolite candidates for

further investigations. These include metabolites related to vitamin B12 deficiency, green tea/coffee intake, and two progestin steroids, representing a few biologically plausible mechanisms involved in gastric cancer etiology. Herein, we propose to conduct a large prospective investigation within a newly formed international consortium

to validate these highly promising findings, as well as discovering novel risk biomarkers, using both untargeted and targeted metabolomics approaches. Pre-diagnostic plasma samples and epidemiologic data including demographics, lifestyle factors, and dietary intakes will be harmonized for >1,600 incident cases and about 2,000

matched controls from eight prospective cohorts. The proposed study will incorporate a rigorous two-stage design to screen and validate circulating metabolite biomarkers for gastric cancer risk in Asians and Whites (Aim 1). We will further assess the generalizability of the validated biomarkers in Asian Americans, African Americans,

and Hispanics/Latinos as well as discover novel race-specific biomarkers in these populations for future investigation (Aim 2). Finally, we will assess mediating effects of the identified metabolites on the associations between known risk factors and gastric cancer to facilitate the understanding of involved biological mechanisms

(Aim 3). Through a series of rigorously designed research activities, fresh insights into mechanism of gastric carcinogenesis and novel biomarkers for future development of risk assessment tools are expected.