[Myeloma precursor cells].

Heterogenous biological character of myeloma cells was associated with different expression of adhesion molecules. Myeloma cells could be phenotypically divided into two subpopulations: CD38++/VLA5+/MPC-1+(VLA-5+) cells and CD38++/VLA5-/MPC-1-(VLA-5-) cells. VLA-5- myeloma cells were morphologically immature and proliferated markedly with response to IL-6 in vitro, while VLA-5+ cells showed very low uptakes of 3H-TdR but secreted higher amounts of M-protein in vitro. These results suggest VLA-5- cells are proliferative precursor in myeloma. With respect to VLA-5 and MPC-1 expression, myeloma precursor cells (CD38++/VLA-5-/MPC-1-/CD10-/CD24-) showed similar phenotype to germinal center B cells (CD38+/VLA-5-/MPC-1-/CD10+/CD24-), rather than that of pre-B cells in the bone marrow (CD38+/VLA-5+/MPC-1-/CD10+/CD24+). Identification of precursor cells and characterization of their growth is important for the understanding of pathophysiology of myeloma and the therapeutic strategy.