Circulating IL-6-type cytokines and sIL-6R in patients with multiple myeloma

We investigated the serum concentration of interleukin-6 (IL-6) and four IL -6 family cytokines oncostatin M (OSM), leukaemia inhibitory factor (LIF), interleukin-ll (IL-11) and ciliary neurotrophic factor (CNTF) as well as IL -6 soluble receptor (sIL-6R) - using an enzyme-linked immunosorbent assay ( ELISA) in 67 patients with multiple myeloma (MM) and 24 healthy controls, f or a possible association between the serum levels of these peptides with d isease activity and known prognostic factors. sIL-6R was detectable in all 67 and IL-6 in 65 (97%) patients. Both peptides were measurable in all heal thy controls. In contrast, OSM was detectable in 30 (44.8%) MM patients and in only four (16.6%) normal individuals. The serum levels of IL-6, OSM and sIL-6R were significantly higher in MM patients compared with control grou p (P<0.001, P<0.03 and P<0.001 respectively), The highest concentrations of these cytokines were found in patients with progressive disease and the lo west in MM patients with stable disease and in healthy persons, LIF was det ectable in four (6%), CNTF in 28 (41.8%) and IL-ll in eight (11.9%) of the patients with MM. In the control group LIF CNTF and IL-11 were measurable i n 8.3%, 33.3% and 8.3% respectively. The serum concentration of these cytok ines did not correlate either with clinical stage or with the phase of dise ase and was similar to those in healthy individuals. We found significant p ositive correlation between IL-6 levels and OSM (P<0.001). Mie also observe d positive correlation between beta 2-M concentration and serum levels of I L-6 (P<0.002), sIL-6R (P<0.002) and OSM(P<0.04) as well as a positive relat ionship between CRP and IL-6 (P<0.001) and OSM (P < 0.002). In conclusion, the serum levels of IL-6, OSM and sIL-6R, but not LIF IL-11 and CNTF may be useful markers of MM activity.