title: Serum levels of soluble IL-6 receptor in multiple myeloma as indicator of disease activity.
abstract: Serum soluble interleukin-6 receptor (sIL-6R) concentrations were measured in 50 patients with plasma cell dyscrasias using a commercially available immunoenzymatic assay kit. There were 40 patients with multiple myeloma (MM), 5 patients with monoclonal gammopathy of undetermined significance (MGUS), 3 patients with solitary plasmacytoma (SPC), 1 patient with chronic myelogenous leukaemia and multiple myeloma (CML/MM), and 1 patient with plasma cell leukaemia (PCL). We found that serum sIL-6R concentrations were higher in MM patients (62.53 +/- 38.85 ng/ml) than in 20 normal volunteers studied (36.75 +/- 13.79 ng/ml) (p < 0.01). The cut-off value of 65 ng/ml seen in 2 of our controls was arbitrarily taken as the upper limit of the control range for serum sIL-6R; according to this criterion, 14 patients with MM (35%), 1 patient with SPC, the unique patient with CML + MM, and the unique patient with PCL had elevated concentrations of the receptor. Patients with MGUS had normal sIL-6R values. In MM patients, serum sIL-6R levels correlated with the clinical phase of the disease: they were elevated in patients with early or late active disease and ranged within normal limits in patients with plateau-phase disease (p < 0.001). Thirteen of 27 patients with active MM had elevated serum sIL-6R values, i.e. 48.1%, but only 1 out of 13 patients with disease in the plateau phase, i.e. 7.7% (p < 0.05). Furthermore, in the entire group of MM patients, serum sIL-6R levels correlated with the concentrations of serum beta 2-microglobulin, (p < 0.02), CRP (p < 0.01), ferritin (p < 0.01) and LDH (p < 0.01), while they did not correlate with disease stage, haemoglobin levels, proportion of marrow myeloma cells, the values of serum IL-6, the levels of serum albumin, or the grade of bone lesions. We conclude that elevated serum sIL-6R levels should be related to the growth of myeloma cells and suggest that serum sIL-6R concentrations may be used as an indicator of disease activity.
authors.affiliation: Division of Haematology, University of Crete School of Medicine, Greece.
authors.forename: H
authors.initials: H
authors.lastname: Papadaki
authors.forename: D
authors.initials: D
authors.lastname: Kyriakou
authors.forename: A
authors.initials: A
authors.lastname: Foudoulakis
authors.forename: F
authors.initials: F
authors.lastname: Markidou
authors.forename: M
authors.initials: M
authors.lastname: Alexandrakis
authors.forename: G D
authors.initials: GD
authors.lastname: Eliopoulos
mesh_terms: D015703:Antigens, CD / Q000097:blood*; D014408:Biomarkers, Tumor / Q000097:blood*; D001853:Bone Marrow / Q000473:pathology; D005293:Ferritins / Q000097:blood; D006801:Humans; D007124:Immunoenzyme Techniques; D007770:L-Lactate Dehydrogenase / Q000097:blood; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000097:blood; D009101:Multiple Myeloma / Q000097:blood* / Q000150:complications / Q000473:pathology; D009363:Neoplasm Proteins / Q000097:blood*; D009378:Neoplasms, Multiple Primary / Q000097:blood; D010014:Osteolysis / Q000097:blood / Q000209:etiology; D010265:Paraproteinemias / Q000097:blood; D010954:Plasmacytoma / Q000473:pathology; D018123:Receptors, Interleukin / Q000097:blood*; D019947:Receptors, Interleukin-6; D012720:Severity of Illness Index; D001613:beta 2-Microglobulin / Q000032:analysis
chemical_list: D015703:Antigens, CD; D014408:Biomarkers, Tumor; D009363:Neoplasm Proteins; D018123:Receptors, Interleukin; D019947:Receptors, Interleukin-6; D001613:beta 2-Microglobulin; D005293:Ferritins; D007770:L-Lactate Dehydrogenase