[Malignant clonogenic precursors in the peripheral blood of patients with multiple myeloma]

To study the clonogenic potential of circulating malignant precursors in the peripheral blood of patients with multiple myeloma (MM).

A new cell culture system was used to expand putative malignant precursor clones and promote their differentiation. Meanwhile, immunocytochemical staining, Giemsa-Wright staining and scanning electron microscopy were employed to reveal the growth properties and biological features of fresh and expanded malignant precursors and plasmacytes.

Small lymphocyte-like B cells, which were actively proliferative and grew in the form of clusters, were found at the third day after culture. They accounted for 38% +/- 14%. The cells didn't express cytoplasmic immunoglobulin (CyIg) and CD38 antigen. In addition, no typical plasmacytes were observed. At the sixth day of culture, morphologically discernible plasmacytes, which grew in the form of large clumps in this culture system, were detected and represented 58% +/- 8%. These plasmacytes strongly expressed CD38 antigen and monoclonal CyIg identical to that of the original myeloma cells.

Malignant clonogenic precursor cells, which have high proliferative potential, are present in the peripheral blood of MM cases, and could proliferate and differentiate into myeloma cells.