Angiogenesis represents an essential step of disease progression in several hematological malignancies, including multiple myeloma (MM). Angiopoietin-1 (Ang-1) and its natural antagonist angiopoietin-2 (Ang-2), both ligands for the receptor tyrosine kinase Tie-2, are essential cytokines for angiogenesis process. Maturation and stabilization of the vascular wall are critically regulated by Ang-1 binding to Tie-2 receptor, while Ang2- antagonizes Tie-2 binding and induces vessel destabilization, which leads to the angiogenic sprouting. Vascular endothelial growth factor (VEGF), angiogenin and basic fibroblast growth factor (bFGF) are also potent stimulators of both physiological and pathological angiogenesis. The aim of this study was to evaluate the serum levels of the above angiogenesis cytokines and explore possible correlations with clinical data, including survival, in 143 newly diagnosed, untreated, MM patients (75M/68F; median age: 68 years, range: 40–94 years). According to ISS, 49 patients had stage 1, 46 stage 2 and 48 stage 3 disease. Serum levels of Ang-1, Ang-2, VEGF, VEGF-A (the major angiogenesis component of VEGF), angiogenin, and bFGF were evaluated using ELISA methodology (R&D Systems, Minneapolis, MN, USA, for all, except VEGF-A: Diaclone, Bensancon, France). MM patients had increased serum levels of Ang-2 (p<0.0001), angiogenin (p<0.0001), VEGF (p=0.033) and VEGF-A (p=0.010) compared with 25 controls of similar age and gender. Ang-1 levels were not different between patients and controls; thus the ratio of Ang-1/Ang-2 was reduced in MM (p<0.0001). Ang-1/Ang-2 ratio correlated with ISS (p=0.022) and beta2-microglobulin (p=0.03), while angiogenin showed strong correlations with ISS (p<0.0001), bone disease status (p=0.01) and hemoglobin (p=0.01). Interestingly, VEGF levels correlated with both Ang-1 (p<0.0001) and Ang-2 (p<0.0001) as well as with bFGF (p<0.0001) and LDH (p=0.01) serum levels. The median survival of all patients was 47 months and the median follow-up was 20 months. The univariate analysis revealed that ISS stage (p=0.001), serum LDH (p=0.001), serum beta2-microglobulin (p=0.0002), bone disease status (p=0.0007), serum creatinine (p=0.045), and the ratio of Ang-1/Ang-2 predicted for survival. Patients with serum Ang-1/Ang-2 of below or equal to the median value (4.8) had a median survival of 25 months, while patients with Ang-1/Ang-2 values of above the median value of 4.8 had a median survival of 53 months (p=0.0065). The multivariate analysis revealed that only serum LDH (p=0.003), Ang-1/Ang-2 ratio (p=0.005) and bone disease status (p=0.015) could independently predict for survival. These results reveal for the first time in MM patients the correlation of reduced Ang-1/Ang-2 ratio with advanced disease and highlight the role of Ang-1/Ang-2 pathway in the biology of plasma cell growth as reflected by its influence on survival. These observations reveal Ang-1/Ang-2/Tie-2 system as a possible target for the development of novel anti-myeloma agents.

Author notes

Disclosure: No relevant conflicts of interest to declare.