Monitoring serum levels ELR+ CXC chemokines and the relationship between microvessel density and angiogenic growth factors in multiple myeloma

Abstract

Background: The ELR+ CXC chemokines are important mediators of tumorigenesis, related to their angiogenic properties. Angiogenesis appears to be a prominent feature in the progression of multiple myeloma (MM). CXC chemokines have four highly conserved cysteine amino acid residues, with the first two cysteine molecules separated by a single amino acid. The angiogenic potential of this group is determined by the presence of three amino acid residues (Glu-Leu-Arg: the ELR motif) preceding the first cysteine amino acid, in the NH2 terminus.

Aims: The purpose of this study was to determine serum concentrations of angiogenesis-related chemokines ELR+ motif, such as interleukin-8 (IL-8), epithelial neutrophil activating protein-78 (ENA-78) and growth-related gene alpha (GRO-α), as well the bone marrow microvascular density (MVD) in patients with MM at diagnosis and after treatment, in plateau phase. We also evaluated the relationship among them with other known growth factors involved in angiogenesis.

Methods: Serum levels of the ELR+ CXC chemokines: IL-8, ENA-78 and GRO-α as well as of the angiogenic factors: hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF) and tumor necrosis factor-α (TNF-α) were determined in 63 newly diagnosed MM patients, in 30 in plateau phase and in 20 healthy controls. Serum measurements of them were performed with commercially available kits for ELISA. Bone marrow biopsies were performed before and after treatment, in plateau phase, in order to determine MVD by staining vessels with anti-CD31.

Results: Serum concentrations of IL-8, ENA-78, GRO-α and TNF-α were significantly higher in the group of MM patients (44.5±25.3, 765±572.1, 186.5±129.1 and 4.2±2.8 pg/ml, respectively) in comparison to control group (27.3±6.4, 335.1±268.6, 112.5±76.1 and 1.3±0.8 pg/ml) (p<0.02 for GRO-α, p<0.001 for other cases). We also found that untreated patients had higher levels of IL-8, ENA-78, GRO-α than post treatment patients, but statistical significant difference was found only for IL-8 (48.36±30.93 pg/ml vs. 35.05±19.77 pg/ml, p<0.001). Furthermore IL-8, GRO-α, TNF-α, HGF and VEGF were significantly higher with increasing disease stage (p<0.001 in all cases). ENA-78 serum levels were higher in stage III than in stage I and II, but without statistical significance. Additionally we correlated each proinflammatory cytokine with well known angiogenic factors such as HGF, VEGF and TNF-α. A positive correlation was found between serum HGF and IL-8 and GRO-α (r=0.316 p<0.01, r=0.297 p<0.02, respectively). Similarly serum VEGF correlated with ENA-78 and GRO-α (r=0.323 p<0.01, r=0.469 p<0.001, respectively). In the pretreatment group of patients a positive correlation between bone marrow MVD and serum levels of GRO-α was found (r=0.304 p<0.01). There was a difference in survival times between patients with higher than median versus low IL-8, ENA-78 and GRO-α levels, but the differences could not reach statistical significance in either case.

Conclusions: These findings support the hypothesis that ELR+ motif CXC chemokines, such as IL-8, ENA-78 and GRO-α correlate with angiogenic growth factors and may play a role in the progression of MM. Further studies are needed to determine their prognostic and predictive significance.