STAT3 and plasma cell myeloma: Interleukin-6 is produced by MM cells and promotes myeloma cell proliferation in an autocrine manner (Klein et al, 1995; Chauhan et al, 1996; Jemal et al, 2003; Anderson, 2004) through phosphorylation of the signalling protein STAT3 (Kaptein et al, 1996; Hirano et al, 2000; Chatterjee et al, 2002).