High Apelin Level Indicates a Poor Prognostic Factor in Muscle-Invasive Bladder Cancer

PURPOSE: To compare the expression level of apelin in muscle-invasive bladder cancer and matched paracarcinoma tissues and investigate the relationship between apelin and clinical prognosis in the patients. METHODS: To assess apelin expression by using immunohistochemical method compared with bladder tumors and matched paracarcinoma tissues. Subsequently, the correlation of apelin expression with the clinicopathological features of bladder cancer patients was analyzed. Kaplan-Meier survival curves method was used to analyze apelin prognostic significance for muscle-invasive bladder cancer patients (including 404 muscle-invasive bladder cancer patients and 28 normal bladder tissues, in TCGA dataset). RESULTS: Apelin protein level was overexpressed in bladder tumor tissues compared with paracarcinoma tissues. Furthermore, high apelin expression was associated with high tumor stage (P < 0.05), distant metastasis (P < 0.05), and vascular invasion (P < 0.05). Kaplan-Meier curve analyses showed that the overexpression of apelin was a potential predictor of overall survival and disease-free survival. CONCLUSION: Apelin was upregulated in bladder tumor tissues compared with matched adjacent noncancer tissues, especially in the high tumor stage, distant metastasis, and vascular invasion. What is more, high expression of apelin in muscle-invasive bladder cancer indicates the poor prognosis. These data suggested that apelin might be a therapeutic potential biomarker in muscle-invasive bladder cancer patients.