Apelin is a novel circulating biomarker for the diagnosis of lung cancer

Apelin was an important factor tumor development but its role in diagnosis of lung cancer remained unknown. In this study, ELISA assay was performed to measure the circulating level of Apelin in plasma samples from 129 lung cancer patients and 57 healthy controls. The aim of this study was to evaluate whether the circulating Apelin could act as biomarker in lung cancer diagnosis. The results indicated that plasma Apelin levels were significantly lower in lung cancer patients than in healthy controls (P<0.0001). Receiver operating characteristic (ROC) analysis showed that Apelin displayed higher SN/SP and AUC (SN: 84.1%, SP: 71.5%, AUC: 77.3%) than two clinical existing biomarkers: CEA (SN: 74.1%, SP: 73.5%, AUC: 81.01%) and Cyfra21-1 (SN: 81.5%, SP: 70.2%, AUC: 78.9%). In addition, the plasma levels of Apelin could contribute to diagnosis of adenocarcinoma patients with high efficiency (SN: 84.2%, SP: 71.4%, AUC: 77.7%). Besides, the expression of Apelin was related to metastasis (P<0.01) in lung cancer patients. Combined analysis of Apelin with CEA and Cyfra21-1 was more effective for lung cancer diagnosis (AUC: 0.980, 95% CI, 0.952-1.000) and lung adenocarcinoma diagnosis (AUC: 0.970, 95% CI: 0.9251.000) than Apelin alone. All these results showed that Apelin can be used as a novel biomarker for the diagnosis of lung cancer with high sensitivity and specificity.