IL-6 is one of the major growth factors involved in the pathogenesis of multiple myeloma, a cancer seen in older individuals. IL-6 mediates its effects by binding to a receptor complex. After binding of IL-6 to a membrane bound IL-6R, the complex of IL-6 and IL-6R associates with gp130. The gp130 molecule has no IL-6 binding capacity by itself but conveys high-affinity binding and is responsible for signal transduction. Furthermore, soluble forms of both IL-6R and gp130 exist. The sIL-6R acts as an agonist for IL-6-induced myeloma cell proliferation.

The activation of gp130 is central event in the stimulation of myeloma cell growth. The activation of gp130 by the IL-6/IL-6R complex, results in homodimerization and phosphorylation of tyrosine residues in the intracellular part of gp130 by the JAK family of enzymes consisting of protein tyrosine kinases, which play a pivotal role in the signal transduction process mediated by many cytokines.