Abstract: Objective To explore the biological functions of latent transforming growth factor beta binding protein 1 (LTBP1) in the occurrence, development, and immune microenvironment ofgastric cancer. Methods The expression level of LTBP1 in gastric cancer was analyzed by using TCGA databases, the results were then validated in the gastric cancer tissues and the para-cancerous tissues. The association between LTBP1 expression level and the clinicopathological variables were analyzed by regression proportional analysis method. Cox regression analysis and Kaplan-Meier plots were used to assess the prognostic value of LTBP1 in gastric cancer. The correlation between the expression level of LTBP1 and the immune cells infiltration was analyzed by TIMER. Immunohistochemical staining was used to detect the expression level of LTBP1 protein in gastric cancer tissues and adjacenttissues. Results LTBP1 was significantly up-regulated in the gastric cancer tissues when comparedwith that in the normal samples. Its expression level was significantly correlated with the pathologic TNM stages. Higher LTBP1 expression indicated poor overall survival (OS) in patients with gastric cancer. We identified that LTBP1 expression had a positive correlation with 3 kinds of immune cells infiltration by TIMER. Immunohistochemical results showed that LTBP1 was significantly overexpressedin gastric cancer tissues. Conclusion LTBP1 can be a potential prognostic biomarker for gastric cancer patients and influences tumor immune microenvironment in gastric cancer.

Key words: gastric cancer, latent transforming growth factor beta binding protein 1, survival analysis, tumor microenvironment