In multiple myeloma, circulating hyperdiploid B cells have clonotypic immunoglobulin heavy chain rearrangements and may mediate spread of disease.
DNA aneuploidy characterizes a proportion of malignant bone marrow (BM)-localized plasma cells in multiple myeloma (MM). This analysis shows that for most MM patients, circulating clonotypic B cells in MM are also hyperdiploid. Although all normal B cells and some malignant B cells are diploid, hyperdiploidy is likely to be exclusive to those that are malignant. Hyperdiploid MM B cells express CD34 and have clonotypic IgH transcripts, confirming them as part of the malignant clone. For MM, 92% (70/76) of patients had a DNA hyperdiploid subset [5-30% of peripheral blood mononuclear cells (PBMCs)] of CD19+ B cells. All CD19+ PBMCs in MM expressed CD19 and IgH variable diversity joining (VDJ) transcripts, confirming them as B cells. DNA aneuploid cells were undetectable in T or B lymphocytes from normal blood, spleen or thymus, or in blood from patients with B chronic lymphocytic leukemia. In MM, untreated patients had the highest DNA index (1.12). DNA hyperdiploid PBMCs were most frequent among untreated patients and were significantly reduced after chemotherapy. Diploid B cells were significantly more frequent after chemotherapy than at diagnosis. Of the hyperdiploid PBMCs, 81 +/- 3% expressed CD34 and CD19. In contrast to circulating CD34+ B cells, CD34- B cells in MM are diploid. In MM, unlike hyperdiploid PBMC B cells, hyperdiploid BM plasma cells lack both CD34 and CD19, suggesting that loss of CD34 correlates with differentiation and BM anchoring. In situ reverse transcription-PCR of the CD34+ (hyperdiploid) and CD34- (diploid) PBMC B-cell subsets was performed using patient-specific primers to amplify clonotypic IgH VDJ transcripts. Confirming previous work, CD34+ hyperdiploid MM PBMCs were clonotypic (86 +/- 5%). In contrast, CD34- diploid MM PBMCs had few monoclonal cells (4.8 +/- 2%). The lack of hyperdiploidy, together with the relative absence of cells having clonotypic transcripts, suggests these polyclonal CD34- B cells are normal. After culture in colchicine to arrest mitosis, hyperdiploid B cells were reduced and MM B cells accumulated in a diploid G2-M, suggesting that hyperdiploid in MM may represent a transient S-phase arrest rather than an aneuploid G0 phase. The DNA hyperdiploidy of CD34+ clonotypic B cells suggests these cells may be clinically important constituents of the myeloma clone and that they may play a direct role in the spread of myeloma.
Pilarski
L M
LM
Department of Oncology, University of Alberta, Edmonton, Canada. lpilarsk@gpu.srv.ualberta.ca
Giannakopoulos
N V
NV
Szczepek
A J
AJ
Masellis
A M
AM
Mant
M J
MJ
Belch
A R
AR
D001402:B-Lymphocytes / Q000276:immunology*; D001854:Bone Marrow Cells / Q000276:immunology / Q000473:pathology; D004171:Diploidy; D015321:Gene Rearrangement; D005803:Genes, Immunoglobulin; D006801:Humans; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000097:blood / Q000235:genetics / Q000276:immunology / Q000473:pathology; D009101:Multiple Myeloma / Q000097:blood / Q000235:genetics* / Q000276:immunology* / Q000473:pathology; D011379:Prognosis; D013601:T-Lymphocytes / Q000276:immunology; D014158:Transcription, Genetic
D007143:Immunoglobulin Heavy Chains