A gp130 interleukin-6 transducer-dependent SCID model of human multiple myeloma

Agonist antihuman gp130 transducer monoclonal antibodies (MoAbs) were used in SCID mice to grow myeloma cells whose survival and proliferation is dependent on gp130 transducer activation. The agonist anti-gp130 MoAbs neither bound to murine gp130 nor activated murine cells and, as a consequence, did not induce interleukin-6 (IL-6)-related toxicities in mice. They have a 2-week half-life in vivo when injected in the peritoneum. The agonist antibodies made possible the in vivo growth of exogenous IL-6-dependent human myeloma cells as well as that of freshly explanted myeloma cells from 1 patient with secondary plasma cell leukemia. Tumors occurred 4 to 10 weeks after myeloma cell graft and weighed 3 to 5 g. They grew as solid tumors in the peritoneal cavity and metastasized to the different peritoneal organs: liver, pancreas, spleen, and intestine. Tumoral cells were detected in blood and bone marrow of mice grafted with the XG-2 myeloma cells. Tumoral cells grown in SCID mice had kept the phenotypic characteristics of the original tumoral cells and their in vitro growth required the presence of IL-6 or agonist anti-gp130 MoAbs. Myeloma cells from 4 patients with medullary involvement persisted for more than 1 year as judged by detectable circulating human Ig. However, no tumors were detected, suggesting a long-term survival of human myeloma cells without major proliferation. These observations paralleled those made in in vitro cultures as well as the tumor growth pattern in these patients. This gp130 transducer-dependent SCID model of multiple myeloma should be useful to study various therapeutical approaches in multiple myeloma in vivo.