Regulation of Apelin Is Associated with Proliferation and Angiogenesis in Gastric Cancer

Abstract Background: Apelin is an emerging endogenous ligand, which is involved in proliferation and angiogenesis in certain cancers. However, few studies have reported its functions and underlying mechanisms in human gastric cancer (GC). Therefore, the present study aimed to investigate the effect of Apelin expression in human GC and the underlying mechanisms of Apelin in the promotion of proliferation both in vitro and in vivo.Methods: A total of 178 patients diagnosed with GC under postoperative care were enrolled for the study to investigate clinicopathological and immunohistochemical factors of Apelin expression. Survival of patients was analyzed using the Kaplan-Meier method and Cox regression model. We adopted quantitative real-time reverse transcription-polymerase chain reaction (RT-PCR), western blot and ELISA to analyze human GC specimens and cell lines. The role and mechanisms of Apelin were evaluated by performing in vitro and in vivo experiments to analyze exogenous Apelin and its overexpression in human GC cells. Results: The expression of Apelin was higher in human gastric cancer cells than in adjacent normal tissues. Apelin, which was overexpressed in vessel invasion (P <0.01), lymph node metastasis (P <0.01), late-staged tumor (T) status (P <0.05), pathological type (P <0.05) and nerve invasion (P <0.05), also exhibited a positive correlation with vascular endothelial growth factor (VEGF). Apelin overexpression or exogenous Apelin activated downstream of ERK/Cyclin D1/MMP-9 signaling pathway to promote MGC-803 cell proliferation and invasion in vitro. Apelin overexpression promoted angiogenesis aiming at accelerating growth of subcutaneous xenograft in vivo.Conclusions: This study has elucidated the relationship between Apelin and its clinicopathological features in human GC, and the role of Apelin in tumor cell proliferation in human GC cell lines. This is the first study to elucidate underlying mechanisms of Apelin in the proliferation of GC. Apelin can be a potential therapeutic target for human GC.