Abstract: Objective To explore the correlation of CPNE3 expression with long- term prognosis of patients with gastric cancer (GC) and the possible mechanism. Methods We retrospectively collected the data of 104 GC patients undergoing radical surgery in our hospital from February, 2013 to October, 2017. TCGA database and immunohistochemistry were used to analyze CPNE3 expression level in GC tissues and its effects on tumor progression and long-term prognosis of the patients. GO analysis was performed to predict the biological role of CPNE3 in GC. We also conducted cell experiments with MGC803 cells and observed the effects of CPNE3 knockdown, CPNE3 overexpression and LY294002 (a PI3K/AKT inhibitor) treatment on cell apoptosis and cellular expressions of apoptotic proteins using flow cytometry and Western blotting. Results TCGA analysis and immunohistochemistry both showed high expressions of CPNE3 in GC (P<0.05). The patients with high CPNE3 expressions had a reduced 5-year survival (P<0.01), and a high CPNE3 expression, CEA level≥5 μg/L, CA19-9 level ≥37 kU/L, T3-T4 stage, and N2-N3 stage were all independent risk factors for a lowered 5-year survival rate after surgery. The sensitivity and specificity of CPNE3 for predicting 5-year mortality was 79.59% and 74.55%, respectively (P<0.05). GO analysis predicted that CPNE3 negatively regulated GC cell apoptosis. In MGC803 cells, CPNE3 knockdown significantly increased cell apoptosis, enhanced Bax and Cleaved Caspase-3 expressions and decreased Bcl-2 expression, while CPNE3 overexpression produced the opposite results (P<0.05). The cellular expressions of p-PI3K and p-AKT were significantly decreased following CPNE3 knockdown and increased following CPNE3 overexpression (P<0.05). Treatment with LY294002 obviously attenuated the inhibitory effect of CPNE3 overexpression on apoptosis of MGC803 cells (P<0.05). Conclusion CPNE3 is highly expressed in GC tissues and affects the long-term prognosis of the patients possibly by inhibiting GC cell apoptosis through activation of PI3K/AKT signaling.

Key words: gastric cancer; CPNE3; cell apoptosis; prognosis; PI3K/AKT