Fig. 1

Histology profiling in gastric cardiac mucosa from tumor-free individuals. a Flow chart illustrating study design. Step 1, Gastric cardiac mucosa biopsies were obtained from a total of 150 tumor-free individuals. Tissue samples were then stratified into two groups (Normal and IM) based on histopathology. Red dashed circle denotes the biopsy location. Step 2, A total of 11 freshly frozen samples (four normal controls and seven IMs) were assayed for DNA methylation profiling to identify IM-specific DNA methylation markers. Step 3, Verification of IM-specific DNA methylation markers at the transcriptional level. Yellow closed and open circles indicate methylated and unmethylated CpGs, respectively. b Representative endoscopic images illustrating the biopsy location of the gastric cardiac mucosa (indicated by yellow arrows). Before, endoscopic image showing gastric cardiac mucosa before sampling. After, endoscopic image showing gastric cardiac mucosa after sampling. Red dashed lines denote the gastro-esophageal junction. c Hematoxylin and eosin-stained sections show the normal (upper left) and IM (upper right) gastric cardiac mucosa. The intestinal metaplastic epithelium is composed of goblet cells interspersed between mucous cells, both at the surface and in the glandular epithelium (outlined by red dashed lines). Horizontal slice bar depicts the proportion of histology-based detected IM in gastric cardia in a total of 118 tissue samples. Source data are presented in Additional file 2: Table S1