High apelin levels could be used as a diagnostic marker in multiple myeloma: A comparative study.

Background: Apelin/APJ system regulates angiogenesis and is overexpressed in some malignancies. Apelin can induce lymphangiogenesis and lymph node metastasis.

Objective: We evaluated apelin levels in multiple myeloma (MM) and non-Hodgkin lymphoma (NHL); and analyzed the association between apelin levels and clinical findings.

Methods: We included consecutive 29 MM, 31 NHL patients, and 19 healthy controls. Patients' demographic and clinical features, treatment modalities, and responses were recorded from hospital records. Plasma apelin was determined by enzyme-linked immunosorbent assay (ELISA).

Results: MM patients had significantly higher plasma apelin level than NHL and healthy control groups (p< 0.001). Apelin level in NHL group was similar to controls (p> 0.05). ROC curve analysis showed that the area under the curve value for apelin level in MM was 0.842 ng/ml (95%CI: 0.739-0.945, p< 0.001). Plasma apelin level ≥ 0.827 ng/ml had 76% sensitivity and 86% specificity for the diagnosis of MM. Multivariate Cox regression analysis showed that MM patients with high apelin level had better prognosis and patients with advanced stage of disease (ISS-3) had significantly poor prognosis when compared to others. In the MM group, apelin level correlated negatively with LDH (r = -0.39, p= 0.038).

Conclusions: In MM, plasma apelin level was significantly higher than in NHL and control groups. Apelin could be playing a role in MM pathogenesis; and apelin level could be used as a diagnostic and prognostic biomarker in MM.