Abstract
Waldenström macroglobulinemia (WM) is a monoclonal B cell disorder characterized by a circulating monoclonal IgM protein that may lead to serum hyperviscosity in association with an infiltration of lymphoplasmacytic cells into the bone marrow. Although proinflammatory and chemotactic cytokines can profoundly affect tumor cells and the tumor microenvironment, and many cytokines have been shown to have potent therapeutic efficacy in preclinical cancer models, the role of cytokine networks in WM is not fully understood. In this study, we used a high-throughput xMAP multiplex immunobead assay technology (Luminex Corp., Austin, TX) to simultaneously test 30 cytokines, chemokines, angiogenic factors as well as growth factors and soluble receptors in the sera of WM patients and compared them with other B cell malignancies including IgM monoclonal gammopathy of undetermined significance (MGUS), follicular lymphoma, chronic lymphocytic leukemia (CLL) as well as healthy controls. Using a Mann-Whitney U test to analyze the differences between the groups, 15 of the 30 cytokines tested had significantly different levels in WM compared to healthy controls. Of those 15 cytokines, 11 were elevated in WM patients and 4 were decreased. Cytokines were grouped into 3 groups; those with < 2-fold difference, 2–8 fold difference and those having > 8-fold difference in their cytokine levels compared to healthy donors. There was a greater than 8-fold increase in the serum levels of Rantes, G-CSF and IL-2R (p<0.0001) in WM patients. Furthermore, 3 cytokines had between 2–8-fold increase in WM patients including IL-4 (p<0.0001), IL-6 (p<0.0019) and IP-10 (p<0.0006). Five cytokines had statistically elevated levels in WM patients compared to healthy controls, however the fold increase was < 2 including HGF (p<0.0185), IL-10 (p<0.0002), MIP-1α (P<0.0484), IL-2 (P<0.0130) and IL-12 (P<0.0155). Of the cytokines that had significantly lower levels in the sera of WM patients, IL-8 (p<0.0001) and EGF (p<0.0001) were > 8-fold decreased, MCP-1 (p<0.0001) was 2–8 fold lower and Eotaxin (p<0.0004) was < 2-fold lower in WM patients. All of the cytokines that had the greatest fold difference (> 8-fold) in WM patients compared to healthy donors also differed significantly from the MGUS patients. Rantes, G-CSF, IL-2R and EGF had significantly different levels compared to other B cell malignancies. We tested for a correlation between the cytokines that had > 2-fold difference between the WM group and control group with clinical features of the disease and found the cytokines IL-6 and IL-2R had a significant correlation with β2-microglobulin levels (p<0.01). We analyzed cytokine levels in the bone marrow plasma of the same patients and found that high levels of IL-2R in the bone marrow microenvironment significantly correlated with anemia and elevated serum β2-microglobulin (p<0.01). In conclusion, we have simultaneously analyzed sera from WM patients for 30 cytokines and found the most significantly elevated cytokines are Rantes, G-CSF and IL-2R and the most significantly downregulated cytokines are IL-8 and EGF. Furthermore, we found that elevated serum levels of IL-6 and IL-2R correlated with β2-microglobulin levels, a measure of disease activity. Further analysis of the biological role of these cytokines in WM may offer insight into disease pathogenesis and provide a basis for novel targeted therapies.
