Delineation of a novel pre-B cell component in plasma cell myeloma: immunochemical, immunophenotypic, genotypic, cytologic, cell culture, and kinetic features

Abstract

A novel pre-B cell component in direct and cultured myeloma bone marrow material has been delineated by using immunochemistry and flow cytometry techniques. Our phenotypic studies suggest a novel hybrid expression of pre-B and plasma cell antigens with coexpression of cytoplasmic mu, common acute lymphoblastic leukemia antigen, terminal deoxynucleotidyl transferase, and plasma cell antigens (PCA-1 and PC- 1). This suggests that myeloma pre-B-like cells are aberrant malignant cells and not normal pre-B lymphocytic counterparts. With the advantage of a pure and stable source of these cells from M3 culture to allow molecular characterization, we performed one- and two-dimensional gel electrophoresis and Western blotting. We found that the cytoplasmic mu in myeloma pre-B-like cells has a molecular weight of 74,000 daltons and an isoelectric point of 6.3 and that it is strikingly homogeneous and discrete in size and charge compared with standard secretory mu, which suggests an aberrant, mutant, or monoclonal form of mu. Monoclonality was further evidenced by heavy- and light-chain immunoglobulin gene rearrangements demonstrated with JH and C kappa probes. We also established that this novel myeloma pre-B component is a major proliferative element as determined by double-labeling experiments with phenotype coupled to labeling/proliferative indexes. Our stimulatory studies indicate some capacity of these cells to mature on exposure to phorbol esters. These myeloma pre-B cells may represent the stem cell or self-renewal component in myeloma. Our establishment of these cells in long-term culture offers a considerable asset in studying the immature cells, which may be critical to the immortalization of myeloma.

S‐Phase cells of the lymphoplasmocytic compartment in hyperdiploid multiple myeloma are diploid cells

“…The second supposition cannot be ruled out but gives no explanation for the existence of a proliferating B lymphocyte population, which has been observed carrying the same idiotype and the same gene rearrangement as the plasmocytic cells and which have been recognized as malignant progenitor cells by various investigators (5, (,,8,22,31,40-42,4(,,48,53). There are studies showing that, in MM, a population of pre-B cells is the target for an oncogenic event, which does not block differentiation to plasmocytic cells ( 12,17,22,23,27,32,37,43,45,47). The third possiblity is equivocal but may be correct.…”

“…Evaluation of cellular DNA content by flow cytometry (FCM) has revealed the existence of an aneuploid plasma cell population in 65-75% of the MM bone marrow samples with a median DNA index of 15% above normal (2,3, 9,11,34,35,53). Most aneuploid tumor cells show a cell marker that is consistent with differentiated B cells, but subpopulations of tumor cells have been observed that express pre-B, early-B, or T lymphocytic, and even myelomonocytic or erythroid, features (16,17,22,23). Differentiation and lineage infedilities of plasmocytic cells in MM suggest that the malignant transformation involves a more pluripotent lymphoplasmacytoid precursor cell with a flexible pattern of gene expression.…”

Autologous bone marrow transplantation therapy for multiple myeloma

“…Moreover, recent reports document the presence of pre-B and B-cell antigens, and even of non-B cell (i.e. myelomonocytic) antigens on myeloma cells, suggesting that an early marrow progenitor cell may be part of the myeloma clone (37)(38)(39)(40)(41)(42)(43). Nonetheless, the phenotype of the "clonogenic" cell remains undefined.…”

“…Several antigens have been described to date on the surface of normal and neoplastic plasma cells and are candidates for use in depleting these cells from autologous marrow prior to BMT for myeloma (29,(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47). We have utilized anti-PCA-1, a MoAb directed to a 26-kilodalton protein on the surface of myeloma cells which is of the IgG2a isotype and therefore capable of complementmediated lysis of antigen-bearing tumor cells in vitro.…”

CD34 selection for purging in multiple myeloma and analysis of CD34+b cell precursors

“…This approach requires the tumor cells to be CD34-. In multiple myeloma the malignant transformation supposedly occurs in a highly proliferative pre-B cell [7], and others even postulate an earlier malignant pluripotent progenitor cell [8]. It has been shown that circulating lymphocytes bearing the early B cell marker CDlO can differentiate into myeloma cells [9].…”