Establishment of an HS23 stromal cell-dependent myeloma cell line: fibronectin and IL-6 are critical.

A multiple myeloma (MM) cell line, MSG1, which depends on HS23 stromal cells for its survival, was established from the pleural effusion of a patient with MM who expressed the M-protein of IgA-λ in his serum. During the first 2 months of culture, the myeloma cells survived on adhesive cells from the pleural effusion and, subsequently, they continued to proliferate on HS23 stromal cells. The phenotype of the established MSG1 cell line was: CD138(+), CD38(++), CD19⁻, CD56⁻, VLA-4(+), VEGFR1(+) and VEGFR2(+). Immunohistochemical staining also demonstrated expression of the IgA and λ chain in MSG1 cytoplasm. Karyotype analysis indicated complex chromosomal abnormalities; hypertriploidy, including the deletion of chromosomes 13 and 17, and c-myc translocation. MSG1 cells continued to proliferate, not only when co-cultured with HS23 cells, but also when cultured only on fibronectin-coated plates with the supernatant of HS23 cells or with control medium containing IL-6. Tocilizumab, an anti-IL-6 receptor antibody, inhibited MSG1 survival under these conditions. Therefore, MSG1 may be a unique myeloma cell line that is useful for the study of cell adhesion-mediated drug resistance induced by adhesion molecules and IL-6 stimulation of myeloma cells.