Sialyltransferase activity in plasma cells of multiple myeloma

A marked elevation of sialyltransferase activity (STA) was observed in a solid tumor of plasma cells, which had been removed from a patient with multiple myeloma (MM), as compared to normal lymphatic tissues. STA was also determined in mononuclear bone marrow cells of 10 patients with MM and found to be 12 times higher than that of bone marrow mononuclear cells from 5 patients with non-malignant disorders (with less than 1% plasma cells in the bone marrow aspirate). A significant correlation was found between STA and the number of plasma cells in the bone marrow aspirate.     

Circulating monoclonal B lymphocytes in multiple myeloma

Peripheral blood mononuclear cells from 28 patients with multiple myeloma (MM) and nine patients with monoclonal gammopathy of unknown significance (MGUS) were studied by immunoglobulin gene analysis. Clonal immunoglobulin gene rearrangements in peripheral blood mononuclear cells (PBIGRA) were demonstrated in 10 of the 28 MM patients (36%). Bone marrow and peripheral blood mononuclear cells were studied simultaneously in five of these 10 patients, and identical gene rearrangements were demonstrated in both. The incidence of such gene arrangements was higher in patients with active disease (cases at presentation or relapsed = 10/19 [47%]) compared to remission status (0/9) and higher in untreated (47%) compared to treated patients (11%) (P less than 0.05). Patients with this phenomenon had higher serum calcium levels (P less than 0.001), and higher bone marrow plasma cell counts (P less than 0.05). Serum creatinine and beta 2-microglobulin were also higher but did not reach statistical significance. None of the patients with monoclonal gammopathy of uncertain significance had gene arrangements. Our findings confirm that circulating B lymphocytes are part of the malignant clone in MM and their presence correlates with high tumour volume.     

Tumour necrosis factor-α and interleukin 4 promote the differentiation of myeloma cell precursors in multiple myeloma

Summary. The effects of tumour necrosis factor-α (TNF-α) and interleukin 4 (IL-4) on peripheral blood mononuclear cells (PBMC) from 36 patients with multiple myeloma (MM), 12 with monoclonal gammopathy of undetermined significance (MGUS) and 21 normal controls, were investigated. In 16/36 patients with MM, monoclonal plasma cells appeared after 4d in cultures containing TNF-α and IL-4. These changes were not observed in PBMC from patients with MGUS or from normal controls. These findings suggest that myeloma cell precursors do exist in the peripheral blood of MM patients and differentiate into plasma cells in the presence of TNF-α and IL-4. Based on these observations, we think that the variation in the number of myeloma cell precursors in peripheral blood could be used as a prognostic parameter of response to chemotherapy in myeloma patients. In addition, this assay may be useful to distinguish early-stage MM from MGUS.     

Evidence for the existence of circulating monoclonal B-lymphocytes in multiple myeloma patients

Multiple myeloma is characterized by the proliferation of a single clone of plasma cells producing a homogeneous immunoglobulin fraction. In this disease, plasma cells home essentially in the bone marrow. However, controversy exists whether peripheral blood B-lymphocytes in patients with multiple myeloma (MM) are part of the malignant clone. We investigated clonal immunoglobulin gene rearrangement (IgGR) in T-cell-depleted peripheral blood mononuclear cells as well as in bone marrow of these patients. Seven out of 17 MM patients demonstrated an identical IgGR in bone marrow and peripheral mononuclear cells, these patients were in an active stage of the disease. In nine patients in plateau phase, clonal IgGR could not be detected in peripheral blood. Peripheral mononuclear cells from ten patients with monoclonal gammopathies of undetermined significance (MGUS) were also examined and no IgGR was detected. The existence of monoclonal B-lymphocytes in the circulation of patients with MM suggests a mechanism whereby the malignant clone homes in the bone marrow through peripheral blood. These findings may also be used for the evaluation of patients with active myeloma and the determination of plateau phase.     

Effects of interleukin-3 and interleukin-6 on peripheral blood cells from multiple myeloma patients and their clinical significance.

The effects of interleukin-3 (IL-3) and interleukin-6 (IL-6) on nonadherent mononuclear cells (NMC) from the peripheral blood of 28 patients with multiple myeloma (MM), 3 patients with monoclonal gammopathy of undetermined significance (MGUS), and 3 normal controls were investigated. In 15 of 27 evaluable patients with MM, monoclonal-cytoplasmic-immunoglobulin (cIg)-positive plasma cells appeared from the T-cell-depleted NMC after 10 days of culture in the presence of IL-3 and IL-6. These changes were not observed in the T cell fraction of myeloma blood or in the T-cell-depleted NMC obtained from cases of MGUS or from normal controls. The percentage of cIg-positive plasmacytoid cells after 10 days of culture was significantly higher in the presence of both IL-3 and IL-6 than with each interleukin alone or the control medium. Furthermore, these changes were often observed in untreated patients. These findings suggest that myeloma precursor cells exist in the peripheral blood of MM patients, especially at diagnosis, and differentiate into cIg-positive cells in the presence of IL-3 and IL-6. This assay may be useful in discriminating the early stage of myeloma from MGUS.     

Bone marrow neovascularization, plasma cell angiogenic potential, and matrix metalloproteinase-2 secretion parallel progression of human multiple myeloma

To assess whether the progression of plasma cell tumors is accompanied by angiogenesis and secretion of matrix-degrading enzymes, bone marrow biopsy specimens from 20 patients with monoclonal gammopathy of undetermined significance (MGUS), 18 patients with nonactive multiple myeloma (MM), and 26 patients with active MM were evaluated for their angiogenic potential and matrix-metalloproteinase (MMP) production. A fivefold increase of the factor VIII+ microvessel area was measured by a planimetric method of point counting in the bone marrow of patients with active MM as compared with nonactive MM and MGUS patients (P <.01). When serum-free conditioned media (CM) of plasma cells isolated from the bone marrow of each patient were tested in vivo for their angiogenic activity in the chick embryo chorioallantoic membrane (CAM) assay, the incidence of angiogenic samples was significantly higher (P <. 01) in the active MM group (76%) compared with nonactive MM (33%) and MGUS (20%) groups. Moreover, a linear correlation (P <.01) was found between the extent of vascularization of the bone marrow of a given patient and the angiogenic activity exerted in the CAM assay by the plasma cells isolated from the same bone marrow. In vitro, a significantly higher fraction of the plasma cell CM samples from the active MM group stimulated human umbilical vein endothelial cell (HUVEC) proliferation (53%, P <.01), migration (42%, P <.05), and/or monocyte chemotaxis (38%, P <.05) when compared with nonactive MM and MGUS groups (ranging between 5% and 15% of the samples). Also, immunoassay of plasma cell extracts showed significantly higher (P <. 01) levels of the angiogenic basic fibroblast growth factor (FGF)-2 in the active MM patients than in nonactive MM and MGUS patients (153 +/- 59, 23 +/- 17, and 31 +/- 18 pg FGF-2/100 micrograms of protein, respectively). Accordingly, neutralizing anti-FGF-2 antibody caused a significant inhibition (ranging from 54% to 68%) of the biological activity exerted on cultured endothelial cells and in the CAM assay by plasma cell CM samples from active MM patients. Finally, in situ hybridization of bone marrow plasma cells and gelatin-zymography of their CM showed that active MM patients express significantly higher (P <.01) levels of MMP-2 mRNA and protein when compared with nonactive MM and MGUS patients, whereas MMP-9 expression was similar in all groups. Taken together, these findings indicate that the progression of plasma cell tumors is accompanied by an increase of bone marrow neovascularization. This is paralleled by an increased angiogenic and invasive potential of bone marrow plasma cells, which is dependent, at least in part, by FGF-2 and MMP-2 production. Induction of angiogenesis and secretion of MMPs by plasma cells in active disease may play a role in their medullary and extramedullary dissemination, raising the hypothesis that angiostatic/anti-MMP agents may be used for therapy of MM.     

Decreased ecto-5'nucleotidase activity of peripheral blood lymphocytes in human monoclonal gammopathies: correlation with tumor cell kinetics

Ecto-5'nucleotidase (5'NT) activity of peripheral blood (PB) lymphocytes was determined in 31 patients with serum monoclonal gammopathies (MG). Twenty-one patients had a diagnosis of multiple myeloma (MM), and ten patients had monoclonal gammopathy of undetermined significance (MGUS). The proliferative activity of the bone marrow plasma cells (LI%) was investigated in 28 of these MG patients by means of tritiated thymidine uptake evaluated by simultaneous autoradiography and cytoplasmic immunofluorescence. 5'NT activity was significantly lower in MG patients as compared with normal controls. MM patients had lower 5'NT activity than MGUS patients, but the difference was not significant. By contrast, MM had significantly higher LI% than MGUS patients. There was a linear regression of 5'NT on LI% which was statistically significant: the higher the LI%, the lower the 5'NT. Because the LI% is an accurate prognostic and monitoring factor in MG, this correlation indicates that 5'NT may be of assistance in predicting the clinical progress of MG patients. In seven MGs, the PB T and B lymphocytes were studied separately. The T cell subpopulation was 5'NT deficient compared to the normal controls, shown as a significant linear regression of T cell 5'NT on the LI%. This suggests that in MG there may be an alteration of nonneoplastic T lymphocytes correlated with tumor growth. The OKT8+ lymphocytes were mainly responsible for the 5'NT deficiency of unseparated T lymphocytes.     

Bone marrow angiogenesis and plasma cell angiogenic and invasive potential in patients with active multiple myeloma

Factor VIII-related antigen-positive microvessel areas were measured by both immunohistochemistry and computerized image analysis in patients with active multiple myeloma (MM), nonactive MM and monoclonal gammopathies of undetermined significance (MGUS). A 5- to 6-fold larger area was found in patients with active MM compared to the other two groups. The conditioned medium (CM) of their bone marrow plasma cells stimulated endothelial cell proliferation and chemotaxis, monocyte chemotaxis and angiogenesis in vivo [chick embryo chorioallantoic membrane (CAM) system] more strongly and frequently than the CM of patients with nonactive MM and MGUS. An immunoassay of plasma cell lysates gave significantly higher levels of fibroblast growth factor-2 (FGF-2) in patients with active MM than in the other two groups, and a neutralizing anti-FGF-2 antibody inhibited by 54-68% the biological activity exerted by the CM in vitro and in the CAM. In situ hybridization of bone marrow plasma cells and gelatin zymography of CM showed that patients with active MM express higher levels of matrix metalloproteinase-2 (MMP-2) mRNA and protein than those with nonactive MM and MGUS, whereas MMP-9 expression and secretion overlapped in all groups. Overall data suggest that patients with active MM represent the vascular phase of plasma cell tumors that is triggered by bone marrow plasma cells, at least partly, through FGF-2 and MMP-2. Both angiogenesis and MMP-2 secretion can account for intramedullary and extramedullary spreading of plasma cells during the active MM.     

The SCID mouse as a model for multiple myeloma

Summary. The SCID mouse was investigated as a potential animal model for human multiple myeloma (MM). Duplicate samples of bone marrow mononuclear cells (BMMC) and/or peripheral blood mononuclear cells (PBMC) of six MM patients in different clinical phases and one patient with monoclonal gammapathy of undetermined significance (MGUS) were injected intraperitoneally into SCID mice. Human immunoglobulins (Ig) in the SCID sera were quantified with a light-chain isotype-specific ELISA, and their monoclonality biochemically characterized, using a sensitive immunoblotting technique after agar gel electrophoresis. Successful transplantation of bone marrow derived-tumour cells in SCID mice was obtained with BMCC of two MM patients with progressive disease. Human plasma cells were detected in the mesenteric fat tissue around the pancreas and the spleen. This model in SCID mice may facilitate studies on processes involved in tumour progression and provides a new tool for therapeutic approaches in MM.     

Circulating monotypic B-cells in multiple myeloma: association with lambda paraproteins

The peripheral blood and bone marrow mononuclear cell immunophenotype was investigated in series of 41 patients with plasma cell dyscrasias (29 with multiple myeloma and 12 with monoclonal gammopathy of undetermined significance (MGUS) or solitary plasmacytoma). A statistically significant relationship between the presence of monotypic B-cells (MBC) in the peripheral blood and the paraprotein light chain isotype was found in the myeloma patients (P = 0.0025). MBCs were documented in 71% of patients with lambda paraproteins, compared with only 13% of patients with kappa paraproteins. The difference in MBC was independent of disease stage as well as of individual prognosticators such as haemoglobin, renal function, paraprotein size and beta-2-microglobulin, although lambda producers had significantly higher calcium levels than patients with kappa paraproteins (P = 0.03). A similar trend was also noted for MBC to be found more commonly in patients with lambda producing MGUS and solitary plasmacytoma. This phenomenon may account for the worse prognosis in patients with lambda paraproteins. In our hands, immunophenotypic detection of peripheral blood involvement in plasma cell dyscrasias is more sensitive than investigation of karyotype or immunoglobulin gene rearrangements.     

CD5 B lymphocyte antigen in monoclonal gammopathy.

Because B lymphocytes bearing the CD5 antigen have been involved in many B-cell malignancies, we have investigated the presence of the CD5 B-cell antigen on B and plasma cells in monoclonal gammopathy. Quantification of CD5 B cells was made in the peripheral blood of seven individuals with monoclonal gammopathy of undetermined significance (MGUS) and in that of 21 patients with multiple myeloma (MM). The bone marrow of ten patients with MM was also studied. Patients with progressive MM presented a significant reduction in both B and CD5 B lymphocytes (i.e., percentages and absolute numbers), when compared with individuals with MGUS and patients with stable MM. These latter individuals and patients did not differ from healthy donors. No CD5 B cells were found in the bone marrow of patients with MM. Moreover, no CD5 antigen could be detected on eight freshly established human myeloma cells lines including six totally dependent on interleukin-6. However, it was weakly expressed on two standard myeloma cell lines not requiring exogenous interleukin-6 (i.e., RPMI 8226 and U 266). In conclusion, our data show mainly an overall reduction of the polyclonal CD5 B lymphocytes similar to what is observed for the other polyclonal B lymphocytes in patients with active MM. Finally, the expression of the CD5 antigen human myeloma cell lines is not constant.     

Clonal circulating cells are common in plasma cell proliferative disorders: a comparison of monoclonal gammopathy of undetermined significance, smoldering multiple myeloma, and active myeloma

The blood of most patients with active multiple myeloma (MM) contains cells related to the bone marrow tumor. However, identifying clonal cells in the blood of patients with monoclonal gammopathy of undetermined significance (MGUS) has been difficult. In this study, we analyzed blood mononuclear cells (BMNCs) from 16 patients with MGUS, 2 with amyloidosis, 8 with smoldering MM (SMM), 2 with indolent MM (IMM), and 15 with active MM using three different methods to detect and quantitate clonal cells, ie, immunofluorescence microscopy (IM) for monoclonal plasma cells, three-color flow cytometry (FC) for CD38(+)CD45- CD45(dim) cells, and the allele-specific oligonucleotide polymerase chain reaction (ASO-PCR). Using ASO-PCR, we were able to detect clonal cells in the blood in 13 of 16 patients with MGUS, 2 of 2 with amyloid, 6 of 8 with SMM, 2 of 2 with IMM, and 13 of 15 with MM. In 9 of the 13 patients with MGUS with blood involvement, the number of clonal cells was very small ( < 0.04% of the BMNCs). The median percentage of clonal cells as determined by ASO-PCR was 0.02 for MGUS, 0.02 for SMM, and 0.24 for MM. Clonal plasma cells or CD38+CD45- CD45(dim) cells were identified by IM or FC in 6 of 16 MGUS patients, 4 of 8 with SMM, and 11 of 15 with MM. In all cases in which IM or FC detected clonal cells, the ASO-PCR was positive. This study shows that, by using ASO-PCR, clonal cells can be found at very low levels in the blood in most patients with MGUS. However, the number of clonal cells in the blood of MGUS patients is less than those with overt MM (P = .006). In contrast to MGUS, patients with active MM are more likely to have identifiable clonal circulating plasma cells (P = .05).     

Expression of interleukin-1beta and tumour necrosis factor-alpha in plasma cells from patients with multiple myeloma

Interleukin-1beta(IL-1beta) and tumour necrosis factor-alpha (TNF-alpha) are potent bone resorbing cytokines that may contribute to the development of the osteolytic bone disease observed in patients with multiple myeloma (MM). Although these factors have been identified in cultures of bone marrow mononuclear cells isolated from patients, the identity of the cells responsible for producing IL-1beta and TNFalpha remains unclear. Using a sensitive dual-colour fluorescence in situ hybridization (FISH) technique and a two-colour immunofluorescence method we have investigated the expression of the mRNA and protein, for IL-1beta and TNFalpha, by individual bone marrow plasma cells from patients with MM and monoclonal gammopathy of undetermined significance (MGUS). The mRNA for IL-1beta and TNFalpha was identified in all cells expressing the immunoglobulin light chain from all patients with MM and MGUS. However, the IL-1beta protein could not be detected in cytoplasmic light chain positive cells in any of the patients examined. In contrast, the TNFalpha protein was detected in clonal plasma cells from patients with both MM and MGUS. Interestingly, the IL-1beta and TNFalpha mRNA and proteins were readily detected within a small proportion of the non-plasma cells from patients with both MM and MGUS. These data suggest that myeloma cells in vivo are able to produce TNFalpha but not IL-1beta. In addition, a small proportion of accessory cells are likely to be able to contribute to the production of both ILbeta and TNFalpha.     

RANK (receptor activator of nuclear factor-kappaB) and RANKL expression in multiple myeloma

The new members of the tumour necrosis factor (TNF) receptor-ligand family, receptor activator of nuclear factor-kappaB ligand (RANKL) and its receptor RANK, play a crucial role in osteoclast differentiation and activation. An increased expression of RANKL and/or RANK may be involved in the excessive bone resorption observed in multiple myeloma (MM). We used immunohistochemistry to study RANK and RANKL expression in bone marrow (BM) biopsies obtained at diagnosis in 15 MM patients, six patients with monoclonal gammopathy of undetermined significance (MGUS) and 10 normal BM biopsies. Plasma cells were not labelled with anti-RANKL or anti-RANK antibodies. In all biopsies, RANKL was expressed in endosteal bone surface, around vessels and in cells characterized by cytoplasmic expansions. These last cells did not express CD45 and were vimentin positive, corresponding to bone marrow stromal cells. Numerous stromal cells expressed RANKL in MM and MGUS specimens, with a greater expression in MM than in MGUS. Very few cells were stained with anti-RANKL in normal BM specimens. With the anti-RANK antibody, small mononuclear cells in the bone microenvironment were positive and were identified as erythroblast cells. In conclusion, we showed that RANKL was expressed in reticular stromal cells, with a greater intensity in myeloma specimens. These results suggest that RANKL overexpressed by bone marrow stromal cells may contribute to the high rate of bone resorption observed in MM.     

Rapid generation of antiplasma cell activity in the bone marrow of myeloma patients by CD3-activated T cells

We have recently shown that peripheral blood T cells of multiple myeloma (MM) patients are very susceptible to stimulation of the T-cell receptor/CD3 complex with anti-CD3 monoclonal antibodies (MoAbs). CD3 stimulation is currently under clinical investigation as a nonspecific approach to boost antitumor effector mechanisms. The aim of this study was to determine whether the hyperreactivity of MM T cells to CD3 stimulation could be exploited to generate antitumor activity. Bone marrow mononuclear cells (BMMCs) from 65 MM patients were stimulated with the anti-CD3 MoAb OKT3 and the effect of this stimulation on autologous T cells and plasma cells was evaluated. The number of CD3+ CD25+ cells on day 6 was significantly higher in MM than the controls (30 normal individuals) (P = .001). Kinetic studies showed that 3H- thymidine incorporation peaked on day 3 and that the T-cell expansion peaked on days 5 and 6. In MM, T-cell activation markedly affected the survival of autologous plasma cells; their number in OKT3-treated cultures was significantly lower than in unstimulated cultures (P < .0001). T-cell activation and plasma cell decrease were not observed when T cells were removed from BMMC preparations. MM produced significantly higher levels of interferon-gamma (P = .005) and tumor necrosis factor-beta (P = .001), but lower levels of tumor necrosis factor-alpha (P < .001) than normal individuals. Interferon-gamma only was partially involved in CD3-induced plasma cell killing. Transwell cultures showed that the main mechanism by which CD3+ CD25+ cells affected plasma cells was direct cell-to-cell contact rather than cytokines. In conclusion, T cells in MM BMMCs possess distinct features in terms of susceptibility to CD3 stimulation and cytokine production compared with normal bone marrow T cells that can be exploited to generate antiplasma cell activity.     

Detection of monoclonal B lymphocytes in bone marrow and peripheral blood of multiple myeloma patients by immunoglobulin gene rearrangement studies

To investigate whether B lymphocytes are involved in the malignant cell clone of multiple myeloma (MM), we performed immunoglobulin gene rearrangement analysis of mononuclear cells and separated B lymphocytes, isolated from bone marrow and peripheral blood of MM patients. The B lymphocytes were separated by immunomagnetic beads, coated with an HLA class II specific antibody. Southern blot analysis with a JH probe revealed in the bone marrow of three out of seven patients identical immunoglobulin gene rearrangements in the B lymphocytes when compared to the plasma cells. Out of 10 patients, two patients with a high tumour burden were found to have monoclonal B lymphocytes in the peripheral blood. These results suggest that B lymphocytes in the bone marrow are part of the myeloma clone and that they can circulate in the peripheral blood. Although previous studies indicated that the ratio of K to lambda bearing lymphocytes in the peripheral blood can provide evidence for B cell monoclonality, we did not find a correlation between the results of K/lambda analysis and immunoglobulin gene rearrangement.     

Differentiation of monoclonal gammopathy of undetermined significance and multiple myeloma using flow cytometric characteristics of plasma cells

BACKGROUND AND OBJECTIVES: The differential diagnosis between multiple myeloma (MM) and monoclonal gammopathy of undetermined significance (MGUS) may be uncertain in some cases; this problem is reflected by discrepancies between different classification systems with an accordance in only 2/3 of cases. We studied whether flow-cytometric characteristics of plasma cells (PC) can be used for the differentiation between MGUS and MM. DESIGN AND METHODS: Patients were divided into 3 groups: Group A included 13 myeloma patients with a plasma cell infiltration of the bone marrow of 10-30%, serum M-protein < or = 3.5 g/dL (IgG) or < or = 2 g/dl (IgA) and without bone lesions in conventional radiography. Group B consisted of 53 patients who fulfilled the Durie and Salmon diagnostic criteria including at least one major criterion, and group C individuals with MGUS (n=17). The ratio of immunophenotypically normal (i.e. CD19(+)/CD56(-)) to all bone marrow plasma cells (BMPC), the number of peripheral blood PC (PBPC), the percentage of BMPC in S-phase and the DNA content of BMPC were analyzed. RESULTS: All individuals with MGUS and no patient with MM in group A or group B had a ratio of phenotypically normal to all BMPC > or = 20%. The median of monoclonal PBPC was 0/microL (range 0-2/ microL) in MGUS, 1/microL (range 0-30/microL) in MM group A and 2.4/microL (range 0-211/microL) in MM group B. The median percentage of BMPC in S-phase was 1.6% both in MGUS and in group A and 3% in group B. Aneuploidy was found in 12%, 11% and 41% in MGUS, group A and group B, respectively. INTERPRETATION AND CONCLUSIONS: The ratio of immunophenotypically normal to all BMPC was the only flow-cytometric parameter for the differentiation of MGUS and MM group A (p<0.0005). The other parameters were significantly different between MGUS and MM group B, but not group A.     

Telomere shortening in patients with plasma cell disorders

OBJECTIVES: Telomeres are essential for maintaining chromosomal integrity; their shortening is associated with chromosome instability. The aim of this work was to study telomere length (TL) on bone marrow (BM) cells from patients with multiple myeloma (MM) and monoclonal gammopathy of undetermined significance (MGUS). METHODS: Thirty-one MM patients: 12 at diagnosis (D), 11 at relapse (R) and eight at remission (RE) and two cases with MGUS were studied. TL based on terminal restriction fragment (TRF) assay was evaluated. Cytogenetic and molecular cytogenetic analyses were performed. Telomeric associations (TAs) on BM metaphases were also studied. RESULTS: TRF analysis in total MM patients showed a mean TRF peak value (5.20 +/- 0.35 kb) shorter than those observed in controls (8.5 +/- 0.5 kb) (P < 0.001). Moreover, TRF at D and R showed a significant telomere shortening (P < 0.001), with TL restored at RE. A strong correlation with the percentage of BM plasma cell infiltration (BMPCI) (rK = -0.540; P = 0.002) was found. Patients with abnormal karyotypes (AK) had significantly shorter TRFs than that observed in MM patients with normal karyotypes (P < 0.05). TRFs in MGUS patients did not differ with respect to controls. TA analysis showed an increased percentage in MM (19.46 +/- 1.98%) with respect to MGUS (6.12 +/- 1.87%) and normal BM cells (2.00 +/- 0.93%) (P < 0.001). CONCLUSIONS: MM patients showed a significant reduction in TL (> 60% of BMPCI and AK), suggesting a probable association with clinical evolution. Moreover, our findings support the idea that telomere shortening usually leads to increased frequencies of TAs and chromosome instability.     

Clinical, morphological, and cell kinetic differences among multiple myeloma, monoclonal gammopathy of undetermined significance, and smoldering multiple myeloma

We reviewed the clinical and morphological findings in 43 cases of monoclonal gammopathy of undetermined significance (MGUS), 9 of smoldering multiple myeloma (SMM), and 23 of overt multiple myeloma (MM). In all cases, the patients' physicians had requested a bone marrow examination because of the possibility of MM. In all 75 cases, 3H-thymidine labeling indices were performed. The plasma cell labeling index correctly classified 62 of the 75 cases (83%). A linear discriminant function combining the labeling index and percentage of plasma cells improved the accuracy to 92% (69/75), or to 95% (71/75) if patients in whom MM developed within 6 mo were considered to have MM. The labeling index was most critical for the differential diagnosis of MM from SMM (p less than 0.001). Serum or urine M-protein level, percentage of plasma cells or lymphocytes in the bone marrow, and plasma cell grade, asynchrony, and nucleolar size failed to discriminate the group with SMM from the group with MM. In patients with MGUS or SMM, a plasma cell labeling index greater than 0.4% warned of impending MM. The plasma cell labeling index is a reliable diagnostic test when applied in cases of monoclonal gammopathy, especially when differentiation from MM is difficult using standard clinical criteria.