To evaluate the correlation between gut microbiota and metabolites in Borrmann type IV gastric cancer; To find the effects of microflora and metabolites on target organs; To detect the mechanism of key flora and metabolite by in vitro and in vivo experiments; To construct models of gut microbiota and metabonomics by machine learning.

Inclusion Criteria:

1. Patients who sign informed consent.
2. Borrmann classification of gastric cancer is determined by more than 2 pathologists.
3. Patients with BMI 24-28.
4. Karnofsky (KPS) score >80.

Exclusion Criteria:

1. Patients who take any aspirin, antibiotics, prebiotics, or probiotics within 4 weeks and steroids or immunosuppressants within 6 months prior to specimen collection.
2. Patients who complicate with other malignant tumors.
3. Patients who complicate with diabetes, hypertension, heart disease and infectious diseases.
4. Patients who complicate with inflammatory bowel disease or irritable bowel syndrome.
5. Patients with metastasis.

Healthy population will be selected from community samples. Non-Borrmann IV and Borrmann IV patients will be selected from Department of Oncology in hospitals.