Human bone marrow stroma-dependent myeloma sister cell lines MOLP-6 and MOLP-7 derived from a patient with multiple myeloma.

Human bone marrow stroma (BST)-dependent myeloma sister cell lines MOLP-6 and MOLP-7 were established from the peripheral blood of a multiple myeloma (MM) patient with IgA kappa type MM (stage IIIB). The growth of the cell lines is constitutively dependent on BST cells; none of the cytokines tested nor the culture supernatant of the BST cells could support the growth. Both cell lines showed typical plasma cell morphology with abundant cytoplasm and one to four nuclei under Wright staining. The immunoprofiles of MOLP-6 and MOLP-7 correspond to that seen typically in primary MM cells: positive for cytoplasmic immunoglobulin (Ig) chains, a heavy and kappa light chains, CD9, CD28, CD40, CD44, CD45, CD56, and PCA-1; the cells were negative for surface Igs and various other B-cell, T-cell and myelomonocyte associated markers. Both cell lines also expressed adhesion molecules including HCAM (CD44), VLA-4 (CD49d/CD29), VLA-6 (CD49f/CD29), ICAM-1 (CD54), NCAM (CD56), LFA-3 (CD58) and L-selectin (CD62L). The doubling time of MOLP-6 and MOLP-7 was 48 and 168 hours, respectively. In addition to this growth characteristic, the maximum cell density of each cell line was obtained at 1.7 x 10(6) cells/ml and 9.7 x 10(5) cells/ml, respectively. The characteristics of each cell line may reflect intraclonal variation of the proliferative capacity. The MOLP-6 together with the MOLP-7 sister will be useful model systems for the investigation of the biology of myeloma.