Development of new adherent mutant from human myeloma-derived cell line: In vitro model of anaplastic transformation of myeloma

Anaplastic myeloma is a rare but distinct, biologically aggressive variant of myeloma which usually results from dedifferentiation or anaplastic trans formation of the myeloma cells. The molecular mechanisms that determine the biologic behavior of anaplastic myeloma and effective treatment modalities have not been well known due to lack of in vitro models. In the present st udy, we have developed an anaplastically transformed mutant from a human my eloma-derived cell line. In the process of long-term culture of the myeloma -derived IM-9 cell line in low serum and nutrient conditions, an adherent m utant line was developed and named IM-9/AD. This mutant cell line displayed several characteristics resembling anaplastic myeloma such as: 1, large ce lls with large vesicular nucleus and prominent nucleolus, multinuclearity a nd high mitotic figures; 2, loss of leukocyte-associated antigens; and 3, h igher tumorigenecity in scid mice than its parental cell line. This newly d eveloped mutant cell line may serve as a readily available in vitro model t o investigate the biology of anaplastic myeloma.