Functional imaging of multidrug resistant phenotype by 99mTc-MIBI scan in patients with multiple myeloma

Overexpression of P-glycoprotein (Pgp) is one of the primary mechanisms of multidrug resistance (MDR) in several diseases, including multiple myeloma. The aim of this study was to investigate whether the washout of 99mTc-MIBI, a transport substrate of Pgp, is enhanced in the bone marrow of patients with multiple myeloma overexpressing Pgp. Seventeen (17) patients were i.v. injected with 555 MBq of 99mTc-MIBI, and whole-body scans were performed at 10 and 60 minutes. A region of interest (ROI) was drawn over the thoracic spine of each scan, and the washout of 99mTc-MIBI was calculated, after decay correction, as: (10-minute counts/pixel minus 60-minute counts/pixel) divided by 10-minute counts/pixel. Pgp expression was determined in 17 bone marrow samples obtained from the same patients immediately before the 99mTc-MIBI scan. Following centrifugation over the Ficoll-Hypaque gradient, cytospins were obtained and immunostained with C219 monoclonal antibody. The immunostaining of Pgp was graded as 1, 2, or 3 when a faint, moderate, or intense reaction, respectively, was observed in infiltrating plasma cells. Washout of 99mTc-MIBI ranged between 5% and 26%. A statistically significant direct correlation was found between the washout of the tracer and Pgp expression (Spearman rank correlation coefficient r = 0.74, p < 0.001). A partial overlap of washout values was observed in different classes of Pgp expression, thus preventing the discrimination of individual patients. Washout of 99mTc-MIBI, expressed as the percentage of radioactivity cleared from the bone marrow over a 1-hour period, may be used as a noninvasive tool for in vivo whole-body imaging of Pgp expression and function in multiple myeloma patients.     

Staging and therapy monitoring of multiple myeloma by 99mTc-sestamibi scintigraphy: a five year single center experience

The aim of the present study was the evaluation of the diagnostic value of 99mTc-sestamibi (MIBI) in the detection of bone marrow involvement in patients suffering from multiple myeloma (MM) and its possible role in the follow-up. Between 1998 and 2003, 68 patients with MM and 42 pts with monoclonal gammopathy of undetermined significance (MGUS) were consecutively enrolled in this study. 51/68 MM patients had active disease (AD), 11/62 were in complete remission (CR) and 6/68 in partial remission (PR) after chemotherapy. 18 patients with MM repeated a 99mTc-MIBI scintigraphic study at least 2 months after high-dose chemotherapy. All the scans were scored semi quantitatively according to extension and intensity of tracer uptake. All MGUS pts had a negative 99mTc-MIBI. As far as the MM pts are concerned, 54/68 (49%) pts (48 with AD, 5 with PR and 1 with CR) had a positive 99mTc-MIBI scan, while the 99mTc-MIBI scan was negative in 14/68 pts (10 with CR, 1 with PR and 3 with AD). The overall sensitivity of the 99mTc-MIBI scintigraphy was 92%; specificity was 96%. In the follow up of the pts treated with chemotherapy 99mTc-MIBI closely paralleled the activity of myeloma bone disease. In conclusion, these results indicate that 99mTc-MIBI scintigraphy closely reflects myeloma disease activity in the bone marrow, and that a negative 99mTc-MIBI scan in patients with suspected MM clearly, though not absolutely, indicates absence of disease or clinical remission. The results of this study suggest a clear diagnostic value of 99mTc-MIBI scintigraphy in patients with MM and its potential role during the follow-up for the monitoring of MM bone disease.     

99mTc-sestamibi is a substrate for P-glycoprotein and the multidrug resistance-associated protein.

99mTc-sestamibi (99mTc-MIBI) is a substrate for the P-glycoprotein (P-gp) pump but it is not known whether it is a substrate for the multidrug resistance-associated protein (MRP) pump. Therefore, 99mTc-MIBI was evaluated in the GLC4 cell line and its doxorubicin-resistant MRP-, but not P-gp-, overexpressing GLC4/ADR sublines as well as in the S1 cell line and its MRP-transfected subline S1-MRP. 99mTc-MIBI concentration decreased in the GLC4/ADR sublines with increasing MRP overexpression and was lower in S1-MRP than in S1. 99mTc-MIBI plus vincristine increased 99mTc-MIBI concentration in GLC4 lines compared with 99mTc-MIBI alone. 99mTc-MIBI efflux raised with increasing MRP expression in the GLC4 lines. Glutathione depletion elevated 99mTc-MIBI concentration in GLC4/ADR150x. Cross resistance for 99Tc-MIBI, used to test cytotoxicity of the Tc compound, was observed in GLC4/ADR150x vs GLC4. 99Tc-MIBI induced a synergistic effect on vincristine cytotoxicity in GLC4/ADR150x. These results show that 99mTc-MIBI is involved in MRP-mediated efflux. The fact that 99mTc-MIBI efflux is influenced by MDR1 and MRP expression must be taken into account when this gamma-rays-emitting complex is tested for tumour efflux measurements.     

The Value of the Bone Marrow Plasma Cell Cytoplasmic Light Chain Ratio in Differentiating Between Multiple Myeloma and Monoclonal Gammopathy of Undetermined Significance

We compared the plasma cell light chain ratios in the bone marrows of 13 patients with multiple myeloma (MM), with those of 13 patients with monoclonal gammopathy of undetermined significance (MGUS). The mean light chain ratio in favour of the paraprotein isotype in the myeloma group was 51.83 (95% confidence limits (CL) 29.52-74.14) while in the MGUS group it was 5.30 (CL 2.07-8.52). The difference between the MGUS and MM groups was significant (p = 0.0005). Neither the bone marrow plasma cell count nor the paraprotein level were significantly correlated with the light chain ratio in either of these two groups. We found a cut-off ratio of 8 to be the most useful in differentiating between myeloma and MGUS. Only one patient with myeloma had a ratio below 8, and one MGUS patient had a ratio above this cut-off point. We conclude that determination of the bone marrow plasma cell light chain ratio is a simple and useful test in differentiating between myeloma and MGUS in difficult cases.     

Elevated level of plasma basic fibroblast growth factor in multiple myeloma correlates with increased disease activity.

Recent reports that bone marrow angiogenesis is increased in multiple myeloma prompted us to examine plasma concentrations of angiogenic growth factors and to elucidate their clinical and biological significance. In 45 cases including 36 cases of multiple myeloma and 9 cases of monoclonal gammopathies of undetermined significance (MGUS), plasma concentrations of basic fibroblast growth factor (FGF-2) and vascular endothelial growth factor (VEGF) were evaluated. FGF-2 was significantly elevated in 25 out of 45 (56%) of the patients with multiple myeloma compared with control subjects (median 9.01 pg ml vs. 1.58 pg/ml, P < 0.0001). The 25 cases were all active multiple myeloma, and none of the non-active myeloma and MGUS patients showed a high FGF-2 level. VEGF level was also elevated in 26 out of 45 patients (58%) compared with control subjects (median 42.0 pg/ml vs. 15.8 pg/ml, P < 0.0001 for VEGF). VEGF concentration was high in 20 active myelomas, but also in one non-active myeloma and five MGUS. Elevation of FGF-2 level was associated with beta2-microglobulin level, anemia and bone marrow plasma cell percentage, which represent disease activity. Interestingly, none of five Bence-Jones type myelomas, including four clinically active cases, revealed a high plasma FGF-2 level, while all of them showed a high VEGF level. In all five responders, the plasma FGF-2 levels were significantly decreased after chemotherapy. FGF-2 was immunohistochemically detected in the bone marrow myeloma cells of the patients with high plasma FGF-2 level. We conclude that plasma concentration of FGF-2 can be a useful indicator of disease activity.     

P-glycoprotein expression and in vitro reversion of doxorubicin resistance by verapamil in clinical specimens from acute leukaemia and myeloma.

The expression of the P-glycoprotein which is associated with the development of multidrug resistance in various cell lines was investigated in 87 fresh acute leukaemia and multiple myeloma samples using the specific mouse monoclonal antibody MRK16 in an indirect immunofluorescence assay. Considering a 10% positive cell cut-off value, a heterogeneous expression of P-glycoprotein was observed in 5/22 (22.7%) de novo acute leukaemias, 7/22 (31.8%) relapse or secondary acute leukaemias, 14/27 (51.8%) acute transformation of myeloproliferative or myelodysplastic syndromes and 5/16 (31.2%) multiple myelomas. This expression was not associated with specific cytogenetic abnormalities, especially alterations of chromosome 7q. Verapamil, a calcium channel blocker, has been demonstrated to circumvent the multidrug resistance in cell lines, possibly by interfering with P-glycoprotein function. Using the microculture tetrazolium assay, verapamil was demonstrated to increase the sensitivity of fresh leukaemic or myeloma cells to doxorubicin in 19/43 (43.1%) samples. The doxorubicin IC50 level and the capacity of verapamil to increase the sensitivity of blast cells to doxorubicin in vitro did not correlate with the expression of P-glycoprotein. We conclude that high non-cytotoxic concentrations of verapamil were able to increase the in vitro doxorubicin sensitivity of fresh acute leukaemia and myeloma cells without detectable expression of the P-glycoprotein.     

Elevated Level of Plasma Basic Fibroblast Growth Factor in Multiple Myeloma Correlates with Increased Disease Activity

Recent reports that bone marrow angiogenesis is increased in multiple myeloma prompted us to examine plasma concentrations of angiogenic growth factors and to elucidate their clinical and biological significance. In 45 cases including 36 cases of multiple myeloma and 9 cases of monoclonal gammopathies of undetermined significance (MGUS), plasma concentrations of basic fibroblast growth factor (FGF-2) and vascular endothelial growth factor (VEGF) were evaluated. FGF-2 was significantly elevated in 25 out of 45 (56%) of the patients with multiple myeloma compared with control subjects (median 9.01 pg/ml vs. 1.58 pg/ml, P <0.0001). The 25 cases were all active multiple myeloma, and none of the non-active myeloma and MGUS patients showed a high FGF-2 level. VEGF level was also elevated in 26 out of 45 patients (58%) compared with control subjects (median 42.0 pg/ml vs. 15.8 pg/ml, P <0.0001 for VEGF). VEGF concentration was high in 20 active myelomas, but also in one non-active myeloma and five MGUS. Elevation of FGF-2 level was associated with β2-microglobulin level, anemia and bone marrow plasma cell percentage, which represent disease activity. Interestingly, none of five Bence-Jones type myelomas, including four clinically active cases, revealed a high plasma FGF-2 level, while all of them showed a high VEGF level. In all five responders, the plasma FGF-2 levels were significantly decreased after chemotherapy. FGF-2 was immunohistochemically detected in the bone marrow myeloma cells of the patients with high plasma FGF-2 level. We conclude that plasma concentration of FGF-2 can be a useful indicator of disease activity.     

Bone marrow angiogenesis in 400 patients with monoclonal gammopathy of undetermined significance, multiple myeloma, and primary amyloidosis.

PURPOSE: To determine whether bone marrow (BM) angiogenesis progressively increases along the spectrum of plasma cell disorders ranging from monoclonal gammopathy of undetermined significance (MGUS) to advanced myeloma. EXPERIMENTAL DESIGN: Four hundred patients with the following disorders were studied: MGUS (76 patients); smoldering (indolent; early-stage) multiple myeloma (SMM; 112 patients); newly diagnosed, active multiple myeloma (MM; 99 patients); relapsed (advanced) multiple myeloma (RMM; 26 patients); and primary amyloidosis (AL; 87 patients). Forty-two normal control BM samples were studied for comparison. BM angiogenesis was studied in a blinded manner by immunohistochemical staining for CD34 to identify microvessels. RESULTS: The median (range) microvessel density (MVD) per x400 high power field was 1.3 (0-11) in the controls, 1.7 (0-10) in AL, 3 (0-23) in MGUS, 4 (1-30) in SMM, 11 (1-48) in newly diagnosed MM, and 20 (6-47) in RMM; P < 0.001. MVD was significantly higher in MGUS, SMM, newly diagnosed MM, and RMM compared with controls and AL; P < 0.001. MVD was not significantly different between controls and AL. By grading, high-grade angiogenesis was present in 0% of controls and AL, 1% of MGUS, 3% of SMM, 29% of newly diagnosed MM, and 42% of RMM; P < 0.001. MVD correlated with the BM plasma cell labeling index (rho = 0.46, P < 0.001) and BM plasma cell percentage (rho 0.5, P < 0.001). Survival was 28 months in SMM and newly diagnosed MM with high-grade angiogenesis, compared with 53 months for those with low- and intermediate-grade angiogenesis; P = 0.02. CONCLUSIONS: BM angiogenesis progressively increases along the spectrum of plasma cell disorders, from the more benign MGUS stage to advanced myeloma, indicating that angiogenesis may be related to disease progression.     

14q32 translocations and monosomy 13 observed in monoclonal gammopathy of undetermined significance delineate a multistep process for the oncogenesis of multiple myeloma. Intergroupe Francophone du Myélome.

Clonal plasma cells in monoclonal gammopathy of undetermined significance (MGUS) have been shown to bear copy number chromosome changes. To extend our knowledge of MGUS to structural chromosomal abnormalities, we have performed fluorescence in situ hybridization experiments with probes directed to the 14q32 and 13q14 chromosomal regions in 100 patients with either MGUS or smoldering multiple myeloma (SMM). 14q32 abnormalities were observed in at least 46% of patients with MGUS/SMM, with these abnormalities being present in the majority of clonal plasma cells. Whereas t(11;14)(q13;q32) occurs in 15% of MGUS/SMM patients, an incidence similar to that of overt multiple myeloma (MM) patients, translocation t(4;14)(p16;q32) is observed in only 2% of these cases [P = 0.002 for difference with t(11;14)], as compared with 12% in MM patients (P = 0.013). Monoallelic deletions of the 13q14 region were found in 21% of patients, with two types of situations. In half of the evaluable patients, and especially in patients with SMM, the deletion is present in the majority of clonal plasma cells, as in MM, whereas in the other half of the evaluable patients (essentially in MGUS patients), it is observed in subclones only. These data enable us to elaborate a plasma cell oncogenesis model from MGUS to MM.     

Is Multidrug Resistance (P-Glycoprotein) an Intrinsic Characteristic of Plasma Cells in Patients with Monoclonal Gammopathy of Undetermined Significance, Plasmacytoma, Multiple Myeloma and Amyloidosis?

Multiple myeloma is not a curable disease, and most patients relapse after plateau phase. Drug resistance is a major problem in effective chemotherapy in this kind of disease. Current approaches are aimed at reversing or preventing drug resistance late in the disease. We studied a drug resistance marker, P-glycoprotein (P-gp), in a total of 43 patients with monoclonal gammopathy. This group included eight with monoclonal gammopathy of undetermined significance (MGUS), five with plasmacytoma (PCM), nineteen with multiple myeloma (MM; six newly diagnosed, seven plateau, five refractory, one relapse) and eleven amyloidosis (seven newly diagnosed, four after treatment). Using 3-color flow cytometry, a plasma cell gate was selected on the basis of CD38⁺/45^- (dim) staining and the population was examined for the expression of P-gp using two monoclonal antibodies (MRK16 and UIC2). P-gp expression was positive on marrow plasma cells in 42/43 patients. The resistance index (RI) in these cases (range 2.0-7.07) is comparable to that in the positive cell line KG-1A (3.05-3.08). In 2 of 5 patients with refractory MM, the RI for P-gp (5.4, 6.36) was higher than in plateau phase. These data suggest that relative resistance due to the P-gp mechanism is likely to be an intrinsic property of plasma cells in monoclonal gammopathies and may provide a partial explanation as to why these diseases always relapse. The results of our study support strategies for MDR reversal earlier in the course.     

Elevated circulating sclerostin correlates with advanced disease features and abnormal bone remodeling in symptomatic myeloma: reduction post-bortezomib monotherapy

Sclerostin is a Wingless and Int-1 inhibitor, which is produced by osteocytes and inhibits osteoblast-driven bone formation. Sclerostin is implicated in the pathogenesis of bone loss in metabolic bone disorders but there is no information for its effect on multiple myeloma (MM)-related osteolytic disease. We evaluated circulating sclerostin in 157 newly diagnosed patients with symptomatic myeloma, in 25 with relapsed myeloma who received bortezomib monotherapy, in 21 patients with monoclonal gammopathy of undetermined significance (MGUS), and in 21 healthy controls. Patients with active myeloma had elevated circulating sclerostin compared to MGUS patients and controls (p < 0.01). MM patients who presented with fractures at diagnosis (n = 34) had very high levels of circulating sclerostin compared with all others (p < 0.01), whereas sclerostin correlated negatively with bone specific alkaline phosphatase (a bone formation marker; r = -0.541, p < 0.0001) and positively with C-telopeptide of collagen type-1 (a bone resorption marker; r = 0.524, p < 0.0001). Patients with International Staging System (ISS)-3 disease had higher circulating sclerostin compared to ISS-1 and ISS-2 MM (p = 0.001). Furthermore, patients with high sclerostin (upper quartile, n = 40) had a median survival of 27 months versus 98 months of all others (p = 0.031). Relapsed MM patients had higher levels of circulating sclerostin even compared to newly diagnosed patients (p < 0.01). Bortezomib monotherapy resulted in a reduction of sclerostin by almost 50% in both responders and non-responders. These results suggest that patients with active myeloma have elevated circulating sclerostin, which correlated with advanced disease features including severe bone disease. Our study indicates sclerostin as a possible target for the development of novel therapies to enhance osteoblast function in myeloma.     

Scintigraphic detection of multidrug resistance in cancer

One of the most extensively studied mechanisms of drug resistance involves the drug efflux pump P-glycoprotein (Pgp). The availability of radiolabeled substrates of Pgp such as 99mTc-MIBI and analogous 99mTc-labeled agents allows the clinical assessment of Pgp function in cancer patients. The consistency of the results from different institutions and trials strongly support the clinical application of this imaging technique for individual tailoring of chemotherapeutic regimens and for designing clinical trials with Pgp modulators.     

The role of interleukin-1 beta in the pathogenesis of multiple myeloma

Interleukin-1 beta has potent OAF activity, can increase the expression of adhesion molecules, and can induce paracrine IL-6 production (see Fig. 1). These biologic effects of IL-1 beta closely parallel several of the clinical features of human myeloma, such as osteolytic bone lesions, homing of myeloma cells to the bone marrow, and IL-6-induced cell growth. The increased production of adhesion molecules could explain why myeloma cells are found predominantly in the bone marrow. These fixed monoclonal plasma cells could subsequently stimulate osteoclasts through the production of IL-1 beta and paracrine generation of IL-6, resulting in osteolytic disease. Also, IL-6 produced by either a paracrine or autocrine mechanism can support the growth of the myeloma cells that may be manifested clinically by an elevated labeling index. In the future, continued follow-up of IL-1 beta-positive and IL-1 beta-negative MGUS patients should determine whether aberrant expression of IL-1 beta by monoclonal plasma cells is a critical genetic event in the progression of MGUS to myeloma. Because MGUS is relatively common in the general population and myeloma is incurable in almost all cases, identification of MGUS patients who are likely to progress to active myeloma will be important in the development of new therapeutic strategies. For example, an effective chemopreventive agent that prevents or delays the transition from MGUS to myeloma could have a major effect on the treatment of patients with monoclonal gammopathies.     

Technetium-99m tetrofosmin SPECT predicts chemotherapy response in small cell lung cancer.

The multidrug resistance gene 1 encoding human P-glycoprotein (Pgp) is thought to play an important role in the multidrug resistance of lung cancer. The purpose of this study was to predict chemotherapy response by technetium-99m tetrofosmin (Tc-99m TF) lung single photon emission computed tomography (SPECT) and compare Pgp expression in patients with untreated small cell lung cancer (SCLC). Forty patients with untreated SCLC received Tc-99m TF lung SPECT prior to chemotherapy. The chemotherapy response was evaluated in the 3rd month after completion of treatment. Immunohistochemical staining of Pgp expression was performed on multiple nonconsecutive sections of biopsy specimens. By quantitative analyses, tumor to background ratios were 1.86 +/- 0.27 and 1.17 +/- 0.26 for patients with a good and poor response, respectively (p < 0.05). All of the 20 patients with a good chemotherapy response also had a positive Tc-99m TF lung SPECT and negative Pgp expression. In contrast, only 4 of the 20 patients with a poor chemotherapy response had a positive Tc-99m TF lung SPECT. Moreover, 10 of the 20 patients with a poor chemotherapy response also had negative Pgp expression (p < 0.05). Therefore, we concluded that Tc-99m TF lung SPECT can accurately predict the chemotherapy response, and Tc-99m TF lung SPECT findings can be partially compatible with Pgp expression in patients with untreated SCLC.     

Total soluble HLA class I and soluble HLA-G in multiple myeloma and monoclonal gammopathy of undetermined significance.

Serum beta2-microglobulin, the light chain of the HLA class I molecular complex, remains one of the best survival prognostic factors in multiple myeloma, but other HLA class I molecules might be of interest in monoclonal gammopathies. In this study, we evaluate total soluble HLA class I (HLA-Is) and soluble HLA-G (HLA-Gs) in 103 patients with newly diagnosed multiple myeloma, 30 patients with monoclonal gammopathy of undetermined significance (MGUS), and 30 healthy subjects, studying their prognostic value in multiple myeloma. In multiple myeloma patients, HLA-Is and HLA-Gs median values were 0.8 microg/mL and 28 ng/mL, respectively. Median HLA-Is concentration was higher in stage II and III multiple myeloma patients than in stage I multiple myeloma, MGUS, and control patients. Median HLA-Gs was significantly lower in healthy controls than in MGUS and multiple myeloma patients. A high level of HLA-Is (> or =2.1 microg/mL) was predictive of short survival (P = 0.017). For each given level of beta2-microglobulin, the relative risk of death was higher for patients with HLA-Is > or = 2.1 microg/mL than in patients with a lower level (P = 0.047). HLA-Gs, a marker of monoclonal gammopathy, was of no prognostic value, but the addition of HLA-Is to beta2-microglobulin produced an efficient prognostic score (P < 0.0001). HLA-Is is a new marker of multiple myeloma tumor load and provides additional survival prognostic information to beta2-microglobulin.     

P-glycoprotein expression in treated and untreated human breast cancer

The expression of P-glycoprotein in primary and recurrent human breast cancer was investigated by means of immunohistochemistry, using a monoclonal antibody (C219) and the streptavidin-biotin-peroxidase method. Twelve patients received no chemotherapeutic treatment. The other 11 patients were treated with chemotherapy, and all developed clinical resistance to it. No or only minimal reactivity was found in specimens coming from the untreated patients (12 cases) or from patients treated with substances not involved in the multidrug resistance phenomenon (four cases). In contrast, three out of seven tumours from patients treated with multidrug resistance related substances showed clear reactivity (positive staining in more than 20% of the tumour cells). In one of these cases, where specimens of the tumour could be studied before and after treatment, an association between the latter and expression of P-glycoprotein was suggested. Finally, this marked expression of P-glycoprotein only took place in tumours treated over a longer space of time (five courses or more of multidrug resistance related chemotherapy).     

Cytokine and chemokine profiles in multiple myeloma; significance of stromal interaction and correlation of IL-8 production with disease progression

Multiple myeloma (MM) is a product of interactions between tumor plasma cells and multiple cell types native to the bone marrow (BM). We have used antibody array technology to examine the proteins produced by BM stromal cells in response to stimulation by BM taken from patients diagnosed with monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), and MM. We observed increased production of the chemokine IL-8 by stromal cells co-cultured with supernatants from bone marrow cells of patients with active myeloma. IL-8 production is correlated with active disease and is dependent upon IL-1beta and NF-kappaB signaling. Consistent with the pro-angiogenic activity of IL-8, increased BM microvessel density (MVD) correlated with stimulation of stromal cell IL-8 production. In addition, the majority of MM cell lines and MM patient plasma cells were found to express IL-8 receptors CXCR1 and CXCR2. We conclude that stromal cell IL-8 production parallels MM disease activity, is IL-1beta induced, and correlates with bone marrow angiogenesis.     

Multiple myeloma. An update on diagnosis and management

Patients with multiple myeloma must be differentiated from those with monoclonal gammopathy of undetermined significance (MGUS) and smoldering multiple myeloma (SMM). The plasma cell labeling index is helpful in differentiating MGUS or SMM from multiple myeloma (MM). No difference in survival was noted between patients given a single alkylating agent and those given a combination of alkylating agents. Alternating cycles of interferon alpha 2 and VBMCP (vincristine, BCNU, melphalan, cyclophosphamide, prednisone) produced a complete or near-complete response in 41% of patients. Allogeneic or syngeneic bone marrow transplantation has produced some benefit. Autologous bone marrow transplantation is potentially applicable to treat more patients. Major problems are eradication of myeloma cells from the bone marrow and removal of myeloma cells from autologous bone marrow. Purging of myeloma cells with monoclonal antibodies and chemotherapy may be helpful. Stem cells from autologous peripheral blood are being used for rescue after high-dose chemotherapy and total-body irradiation.