High Serum Levels of Angiogenic Cytokines in AL Amyloidosis Correlates with Disease Features.

Angiogenesis is a crucial step for disease progression in several hematological malignancies, including plasma cell dyscrasias like multiple myeloma (MM). Angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2) are antagonistic ligands for the receptor tyrosine kinase Tie-2. These cytokines are crucial for maturation and stabilization of the vascular wall: Ang-1 binds to Tie-2 and stabilizes the vascular wall, while Ang2- antagonizes Tie-2 binding and induces vessel destabilization, which leads to the angiogenic sprouting in conjunction with onset of angiogenesis. Vascular endothelial growth factor (VEGF), angiogenin and basic fibroblast growth factor (bFGF) are also potent stimulators of both physiological and pathological angiogenesis. However little is known about the role of these molecules in AL amyloidosis and their possible correlations with the features of the disease. Serum levels of Ang-1, Ang-2, VEGF, and 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). Serum samples were collected from 62 previously untreated AL amyloidosis patients as well as from 35 age-matched healthy controls and 35 newly diagnosed, untreated, myeloma patients. Microvascular Density (MVD) of the bone marrow (BM) was also measured in 15 AL patients who had both serum and trephine biopsies available. Definition of organ involvement was based on established criteria (Gerrtz et al Am J Hematol 2005). Serum levels of VEGF (p<0.001), angiogenin (p<0.001), Ang-1(p=0.002) and Ang-2 (p<0.001) were significantly higher in AL patients than in controls; however the ang1/ang2 ratio was not different. The levels of Ang-2 (r=0.776, p=0.005), angiogenin (r=0.746, p=0.008) and bFGF ((r=0.743, p=0.009) correlated with MVD in BM biopsies of AL patients while VEGF, VEGF-A and Ang-1 were not. When compared to MM patients, AL patients had significantly higher VEGF levels (p=0.007), angiogenin (p=0.003) and Ang-1(p<0.001) levels but lower angiopoietin-2 levels (p=0.09); thus the Ang-1/Ang-2 ratio was higher in AL compared to MM (p=0.08). Both VEGF and VEGF-A were increased in patients with symptoms of peripheral neuropathy (p=0.016 and 0.029 respectively), while Ang-2 was increased in patients with heart involvement (p=0.03). There were no differences between AL patients with a creatinine ≥2 mg/dl and those with creatinine<2 mg/dl. In patients with BM plasma cells (PCs)>10%, Ang-1 was lower than in those with PCs<10% (p=0.013), while Ang-2 was not different (p=0.170); thus the Ang-1/Ang-2 ratio was lower in patients with BMPCs >10% (p=0.021). There was no correlation among the number of involved organs, a significant predictor of survival in AL amyloidosis, and levels of angiogenic cytokines. In conclusion, serum markers of angiogenesis are significantly higher in AL patients compared to both healthy individuals and MM patients indicating a possible pathogenetic role in some features of the disease and also a possible therapeutic target.