It is closely involved in the pathogenesis of MM: 1) IL-6 induces in vitro growth of fresh cells isolated from myeloma patients; 2) The myeloma cells spontaneously produce IL-6 and express the corresponding receptor; 3) antibodies against IL-6 inhibit the growth of myeloma cells; 4) treatment of myeloma patients with antibodies against IL-6 has shown anti-tumor effect [9, 13, 14]; 5) retinoic acid induces apoptosis in myeloma cells by down-regulation expression of the IL-6 receptor [15]. Here, IL6 is linked to plasma cell myeloma.