MULTIPLE-MYELOMA CELLS AND CELLS OF THE HUMAN OSTEOCLAST LINEAGE SHARE MORPHOLOGICAL AND CELL-SURFACE MARKERS

This study demonstrates that the multiple myeloma cell (MMC) in its pl asma cell form is morphologically indistinguishable from human osteocl ast-like cells that form in culture when peripheral blood mononuclear cells (PBMCs) are plated at high density in serum containing medium. M M has been described as a disease of B-cell lineage, monoclonal immuno globulin (lg) producing cells with unique properties: MM precursor cel ls lodge in bone, where they proliferate and differentiate into plasma cell tumors. Then, by some mechanism, presumably involving cytokines, these cells mediate an increase in neighboring osteoclast numbers and activity leading to excessive bone erosion and hypercalcemia. Three d ays after plating PBMCs, tartrate resistant acid phosphatase- (TRAP-) blasts as well as TRAP+ cells, each with an eccentric nucleus, appear in culture. By day 10, TRAP+, vitronectin+ (VR+) cells, appear to be m orphologically indistinguishable from multiple myeloma plasma cells (M MPCs) on cytocentrifuge preparations. These cells are CD19- and CD38+, as are MMCs reported by others. Other surface markers are also share d. Furthermore, Ig mRNA is demonstrated in the cytoplasm of cells at 8 days by in situ hybridization with the IgG FcA3 sequence. This novel finding is not unusual, in light of reports, demonstrating non-B-linea ge Ig-producing cells. Thus, this study raises some serious questions about the true nature of MMCs. (C) 1998 Wiley-Liss, Inc.