Objective To investigate the expression of calcium-dependent phospholipid binding protein 1 (CPNE1) in gastric cancer (GC) and the correlation with prognosis. MethodsThe clinicopathological data of 121 patients who underwent radical gastrectomy in the Department of General Surgery, The 940th Hospital of Joint Logistics Support Force of the People’s Liberation Army from March 2017 to December 2018 were retrospectively collected. The expression of CPNE1 in gastric cancer tissues was detected by immunohistochemical (IHC) staining, and its relationship with prognosis was analyzed. Gastric cancer tissue samples and adjacent tissue samples from 16 patients in the same time were prospectively collected, and the mRNA and protein expressions of CPNE1 were detected by real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) and western blotting (WB), respectively. Multivariate Cox proportional hazard regression model was used to analyze the prognostic factors of gastric cancer patients. ResultsIHC staining results showed that CPNE1 was mainly expressed in the cell membrane and cytoplasm of gastric epithelial cells, and the color showed different degrees of brown. Among the 121 patients, 70 (57.9%) had high CPNE1 expression and 51 (42.1%) had low CPNE1 expression. The RT-qPCR and WB results of 16 pairs of fresh tissue specimens showed that the expression levels of CPNE1 mRNA and protein in gastric cancer tissues were higher than those in adjacent tissues (gastric cancer tissue vs. adjacent tissue: CPNE1 mRNA 1.451 vs. 1.100, P=0.048; CPNE1, 0.995 vs. 0.521, P=0.001). Multivariate Cox proportional hazards regression analysis showed that high expression of CPNE1 [HR=1.923, 95%CI (1.124, 3.290), P=0.017] was risk factors affecting the prognosis of patients with gastric cancer. ConclusionCPNE1 is highly expressed in gastric cancer tissues and is associated with a poor prognosis in patients, and it may be a potential tumor biomarker.