Multiple myeloma: reduced plasma cell contamination in peripheral blood progenitor cell collections performed after repeated high-dose chemotherapy courses

Myeloma cell contamination of peripheral blood stem-cell grafts can predict the outcome in multiple myeloma patients after high-dose chemotherapy and autologous stem-cell transplantation

PURPOSE

High-dose chemotherapy with hematopoietic stem-cell rescue is increasingly being used in the treatment of multiple myeloma. Bone marrow and also peripheral blood stem-cell (PBSC) grafts contain measurable quantities of plasma cells, the biological significance of which is unknown.

METHODS

Patients with multiple myeloma were mobilized with chemotherapy and filgrastim. The number of CD38++/CD138+ cells/kg in the grafts for autologous transplantation was determined by flow cytometry. Patients were stratified into two groups (threshold 4.5 x 10(5) plasma cells kg(-1)) of reinfused plasma cells in the first autologous graft.

RESULTS

The median statistical progression-free survival was 14 months (4-34 months) in the high-contamination group (>4.5 x 10(5) plasma cells kg(-1)) compared to 26 months (4-43 months) in the low-contamination group (<4.5 x 10(5) plasma cells kg(-1), P =0.0096). Patients with 13q deletion were more frequently found to have a high contamination of the stem-cell graft with malignant plasma cells.

CONCLUSIONS

Patients with graft contamination of more than 4.5 x 10(5) plasma cells kg(-1) had a high risk of early disease progression after high-dose chemotherapy. In vivo tumor cell purging prior to mobilization chemotherapy might be one strategy to improve the time to progression of high-risk patients.

Monitoring of residual hematopoiesis after total body irradiation in humans as a model for accidental x-ray exposure: dose-effect and failure of ex vivo expansion of residual stem cells in view of autografting

PURPOSE

To evaluate the residual hematopoiesis at different levels of total body irradiation (TBI) dose in bone marrow (BM) and peripheral blood (PB), and to study the dose-effect relationship on hematopoietic immature and mature progenitors. We also investigated the possibility of expanding ex vivo the residual progenitors exposed to different dose levels of TBI.

METHODS AND MATERIALS

Eight patients treated for AML (n = 3) and myeloma (n = 5) were included. BM and PB samples were harvested before TBI and after doses of: <or=2 Gy, 2.1-5 Gy, and >5 Gy. Mononuclear cells (MNCs) were assayed for burst-forming unit erythroid (BFU-E), granulocyte-forming unit macrophage (CFU-GM), and long-term culture initiating cells (LTC-ICs). Ex vivo expansion: MNCs (after irradiation and controls) were suspended in long-term cultures and expanded with a combination of five cytokines.

RESULTS

CD34+ cells were detectable at 10 Gy. We observed a significant decrease of CFU-GM and BFU-E, respectively, to 13.5% and 8.5% of baseline values for doses <or=2 Gy and to 8.2% and 4.6% for doses ranging between 2.1 and 5 Gy. No dose effect was observed for residual MNCs. LTC-ICs were not detectable after 0.8 Gy. The expansion was not successful after 1.2 Gy.

CONCLUSION

This study confirms the significant decrease of human mature and immature progenitors in BM and PB immediately after low-dose TBI. In addition, the lack of expansion suggests that autografting using BM or PB residual stem cells collected and expanded in vitro in case of accidental whole body exposure may be impractical.

Real-time polymerase chain reaction in multiple myeloma: quantitative analysis of tumor contamination of stem cell harvests

OBJECTIVE

Autologous transplantation of bone marrow (BM) and peripheral blood progenitor cells (PBPC) is commonly used for treatment of multiple myeloma (MM). Although both stem cell sources harbor residual clonal cells, a quantitative evaluation of their level of tumor contamination (LTC) still needs to be performed through highly accurate and reproducible approaches. In this study, we used a validated real-time polymerase chain reaction (PCR) strategy to evaluate LTC of BM and PBPC samples obtained from MM patients.

MATERIALS AND METHODS

The patients underwent two different mobilization courses (defined as early or late course) following two cycles of cyclophosphamide 5 g/m(2). LTC was evaluated by measuring the number of clonal immunoglobulin heavy-chain rearrangements followed by normalization of samples using the GAPDH gene.

RESULTS

Overall, 26 PBPC and 12 BM samples were analyzed. Main results are as follows. 1) PBPC harvests are less contaminated than BM samples taken immediately after each mobilization course (median difference 2.68 logs; range 1.7 to 4.6) (p < 0.0001). 2) LTC of PBPC harvests has only minimal variation among different leukaphereses performed during the same mobilization course (median difference 0.45 logs; range 0.22 to 1.2). 3) No difference was observed among PBPC and BM samples obtained after the late mobilization course as compared to the early mobilization course (median reduction 0.21 logs; range -0.39 to 1.3) (p = 0.84). 4) In PBPC but not in BM samples, there is a clear overestimation of the percentage of plasma cells when flow cytometric evaluation of CD38(bright) cells is compared to real-time PCR results. This suggests that in PBPC, most CD38(bright) cells do not belong to the neoplastic clone.

CONCLUSIONS

Real-time PCR using the IgH rearrangement proved an effective tool for monitoring LTC in stem cell harvests from MM patients. The smaller LTC of PBPC harvests supports the role of PBPC as stem cell rescue for MM patients compared to BM cells.

Tumor cell contamination in re-infused stem cell autografts: does it have clinical significance?

Tumor cells frequently contaminate autologous stem cell products in patients having a variety of malignancies. Mobilized peripheral blood stem cells may be less contaminated with tumor cells than bone marrow harvests are, but they are still frequently infiltrated. Gene-marking studies using retroviral vectors provide evidence that tumor cells contained in autografts contribute to relapse in myeloid leukemia and neuroblastoma patients. Also clinical studies have shown that tumor cell contamination of autografts is associated with shortened disease-free survival; on the other hand, successful ex vivo purging of tumor cells is associated with superior clinical outcome. However, the presence of tumor cells in autografts or insufficient purging may correlate with the extent of systemic residual disease and/or tumor chemosensitivity; therefore, there is no direct evidence that reinfused tumor cells alone cause relapse. Particularly in patients having highly chemosensitive disease and no detected systemic residual disease following high-dose transplant chemotherapy, the relative number of tumor cells contained in autografts and eventually reinfused, may become a determining factor for clinical outcome. There are no randomized trials showing improved (disease-free) survival with purging. In the absence of such trials, the contribution of tumor cells in the stem cell autografts to subsequent relapse remains controversial.

Dexamethasone, paclitaxel, etoposide, cyclophosphamide (d-TEC) and G-CSF for stem cell mobilisation in multiple myeloma

Forty-one patients with multiple myeloma were treated with a novel stem cell mobilisation regimen. The primary end points were adequate stem cell mobilising ability (>1% circulating CD34-positive cells) and collection (> or = 4 x 10(6) CD34-positive cells/kg), and safety. The secondary end point was activity against myeloma. The regimen (d-TEC) consisted of dexamethasone, paclitaxel 200 mg/m(2) i.v., etoposide 60 mg/kg i.v., cyclophosphamide 3 g/m(2) i.v., and G-CSF 5-10 microg/kg/day i.v. A total of 84 cycles were administered to these 41 individuals. Patient characteristics included a median age of 53 years, a median of five prior chemotherapy cycles, and a median interval of 10 months from diagnosis of myeloma to first cycle of d-TEC. Seventy-five percent of the patients had stage II or III disease, 50% had received carmustine and/or melphalan previously, and 25% had received prior radiation therapy. Eighty-eight percent of patients mobilised adequately after the first cycle of d-TEC and 91% mobilized adequately after the second cycle. An adequate number of stem cells were collected in 32 patients. Of the remaining nine patients, three mobilised, but stem cells were not collected, two mobilised but stem cell collection was < 4 x 10(6) CD34-positive cells/kg, three did not mobilise, and one died of disease progression. Major toxicities included pancytopenia, alopecia, fever and stomatitis. One patient died from multi-organ failure and progressive disease. Fifty percent of evaluable patients demonstrated a partial response and 28.6% of patients had a minor response. This novel dose-intense regimen was safe, capable of stem cell mobilisation and collection, even in heavily pre-treated patients, and active against the underlying myeloma.

Tumour kinetics in multiple myeloma before, during, and after treatment

Tumour progression was monitored in seven multiple myeloma (MM) patients undergoing a novel oral chemotherapy regimen (cyclophosphamide, idarubicin and dexamethasone; CID) followed by early autologous stem cell transplantation (ASCT). Allele-specific oligonucleotide PCR (ASO-PCR) was used to semi-quantitate the number of tumour cells within the peripheral blood (PB) and PB progenitor cell (PBPC) harvests and compared with paraprotein levels and morphological bone marrow (BM) assessments. Tumour cells were detected in the PB of all patients at diagnosis, but decreased in response to CID therapy. All but two of the 22 PBPC collections contained MM cells, the levels of which were statistically correlated with overall clinical response to therapy, but not with individual BM or PB tumour loads prior to mobilisation. We also found no correlation between the day of leucapheresis collection and the number of contaminating MM cells, CD34+ cells or MM cells per CD34+ cell. Regardless of tumour contamination levels in the PBPC collections, the majority of patients demonstrated post-ASCT clearing of circulating MM cells. This study suggests that levels of circulating MM cells may be the best indication of patient response to treatment and argues against the theory of differential mobilisation of tumour cells and CD34+ cells in response to cytokine treatment.

CD34+ selection of autologous peripheral blood stem cells for transplantation following sequential cycles of high-dose therapy and mobilization in multiple myeloma

A potential problem of autologous transplantation in the treatment of multiple myeloma (MM) is the infusion of tumor cells. CD34+ selection has been used to purge autografts in MM and it is also possible to reduce tumour cell contamination of autografts by cytotoxic drug therapy prior to peripheral blood stem cell (PBSC) collection. To evaluate the effectiveness of a protocol combining multiple cycles of high-dose therapy and CD34+ selection to reduce tumour contamination of PBSC autografts, 34 MM patients were entered on a treatment schedule comprising two sequential cycles of mobilisation, CD34+ selection, and transplantation following high-dose therapy. In the second cycle of mobilisation there was a five-fold reduction in tumour contamination of the stem cell harvest (0.5 x 106/kg) compared with the first cycle (2.5 x 106/kg). In the 97 CD34+ selection procedures performed a median of 185 x 108 mononuclear cells (MNC) were processed yielding a median of 0.98 x 108 CD34+-enriched cells. CD34+ cells were enriched 68-fold from 1. 3% to 88.6%. The median yield of CD34+ cells was 42.2%. Following CD34+ selection the tumour cell contamination of the leukapheresis product was reduced by a median of 2.7 logs. This study demonstrates that in multiple myeloma a significant reduction in the malignant contamination of stem cell autografts can be achieved by combining the in vivo purging effect of cytotoxic therapy with in vitro purging by CD34+ selection.

Therapeutic relevance of CD34 cell dose in blood cell transplantation for cancer therapy

PURPOSE

To review recent advances in peripheral-blood progenitor-cell (PBPC) transplantation in order to define the optimal cell dose required for autologous and allogeneic transplantation.

MATERIALS AND METHODS

A search of MEDLINE was conducted to identify relevant publications. Their bibliographies were also used to identify further articles and abstracts for critical review.

RESULTS

The CD34(+) cell content of a graft is regarded as an accurate predictor of engraftment success. Postchemotherapy autologous PBPC transplantation with >/= 5 x 10(6) CD34(+) cells/kg body weight leads to more rapid engraftment than does transplantation of lower cell doses. Further increases in transplant cell dose further accelerate platelet but not neutrophil engraftment. Evidence that long-term hematopoietic recovery may be more accurately predicted by the subpopulation of primitive progenitors transplanted suggests that the content of CD34(+)CD33(-) and long-term culture-initiating cells in cell collection samples may be important for predicting successful engraftment, particularly in patients with poor mobilization. Allogeneic transplantation has been limited by concerns regarding graft-versus-host disease and the use of hematopoietic growth factors in donors. The risk of graft rejection and engraftment failure after HLA-mismatched allogeneic transplantation may be overcome by intensive chemoradiotherapy and the infusion of large numbers of T cell-depleted hematopoietic stem cells.

CONCLUSION

An optimal cell dose of >/= 8 x 10(6) CD34(+) cells/kg seems to be recommended for autologous PBPC transplantation. This dose facilitates the administration of scheduled chemotherapy on time and reduces the demand for other supportive therapies. A combination of growth factors may enable patients with poor mobilization to achieve a collection sufficient to allow transplantation. The optimum PBPC dose for allogeneic transplantation remains to be defined.

Multiple myeloma: the number of reinfused plasma cells does not influence outcome of patients treated with intensified chemotherapy and PBPC support

Multiple myeloma (MM) is characterized by the expansion of tumor plasma cells in bone marrow (BM), but neoplastic cells have been consistently detected in peripheral blood (PB). Peripheral blood progenitor cell (PBPC) collections have been widely used to support high-dose therapy for MM patients. A flow cytometric technique has been used to detect plasma cells in PB and PBPC harvests. High CD38 expression identified these cells, and their nature was confirmed by the coexpression of specific antigens, such as CD138 and cytoplasmic immunoglobulins. Malignant plasma cell reinfusion could negatively affect response rate and survival, as demonstrated in other hematological malignancies. To address this issue, the relationship between the number of reinfused plasma cells, response to chemotherapy and event-free survival (EFS) have been analyzed. Sixty-four MM patients were treated with intensified chemotherapy at diagnosis. They were mobilized with cyclophosphamide and G-CSF, and then treated with melphalan 100 mg/m2 (MEL100) followed by PBPC support. A second course was given after 2 months, and a third to patients not in complete remission. There was no correlation between the number of reinfused plasma cells and response rate after this intensified chemotherapy: patients attaining complete remission received 3.6 x 106/kg CD38+ cells, while those with a partial or no response received 5.6 and 2.9 x 106/kg CD38+ cells. Similarly, there was no correlation between the number of reinfused plasma cells and EFS. Patients receiving less than 4.85 x 106/kg CD38+ cells experienced a median EFS of 34.2 months as opposed to 36.4 months for those receiving more than 4.85 x 106/kg CD38+ cells (P = 0.7). Recurrence of the disease is consistently observed in MM: our data suggest that in vivo residual tumor cells, rather than reinfused plasma cells are more likely to be responsible for relapse. Bone Marrow Transplantation (2000) 25, 25-29.

Current drug therapy for multiple myeloma

Recent years have witnessed tremendous advances in the molecular pathogenesis and management of multiple myeloma. Standard chemotherapy (melphalan and prednisone; MP) has been the mainstay of treatment of multiple myeloma for about 3 decades. However, it is no longer considered the 'gold standard', particularly for those patients who will subsequently undergo intensive chemotherapy with autologous or allogeneic peripheral blood stem cell (PBSC) or bone marrow transplantation (BMT), or for patients with refractory myeloma. A variety of induction combination chemotherapy regimens have been developed, some of which have demonstrated an improved response rate and duration and a superior 5-year survival rate when compared with standard chemotherapy. The early use of high dose chemotherapy with autologous PBSC support or BMT has significantly increased the complete remission rate, and has prolonged event-free sur vival and overall survival. Allogeneic bone marrow or PBSC transplantation may be a good option for selected patients with poor prognostic features. The role of interferon-alpha in multiple myeloma is still inconclusive despite many years of clinical evaluation. The clinical application of chemosensitising agents that can inhibit P-glycoprotein (P-gp) expression and function, and particularly the development of more potent P-gp modulators such as valspodar (PSC 833) and elacridar (GF120918) has made it possible to reverse multidrug resistance in some refractory patients and to enhance the efficacy of chemotherapeutic agents. Immunotherapeutic approaches to purging of autologous bone marrow or PBSC, or as adjuvant therapy for minimal residual disease, show great promise. Finally, a number of new therapies specifically designed to treat many of the complications of multiple myeloma are improving clinical outcomes and quality of life for these patients.

Bone marrow transplantation in multiple myeloma

Experience from around the world now suggests that high response rates can be achieved in patients with multiple myeloma treated with high-dose therapy followed by hematopoietic stem cell transplantation. However, patients are destined to relapse and few, if any, are cured. Major obstacles to cure are the excessive toxicity noted after allografting in multiple myeloma, contaminating tumor cells in multiple myeloma autografts, and most importantly, the persistence of minimal residual disease after high-dose therapy and either allogeneic or autologous stem cell transplantation. In this context, strategies are being developed to decrease the toxicity of allografting and to enhance allogeneic anti-multiple myeloma immunity after transplantation to improve outcome. To improve autografting, better ablative regimens, more efficacious purging of tumor cells from autografts, and enhancement of autologous anti-multiple myeloma immunity post-transplantation are modalities being tested to enhance overall and event-free survival.

Molecular and clinical remissions in multiple myeloma: role of autologous and allogeneic transplantation of hematopoietic cells

PURPOSE

To describe molecular monitoring of minimal residual disease in patients with myeloma who have achieved complete remission (CR) after autologous or allogeneic transplantation of hematopoietic cells.

MATERIALS AND METHODS

Clonal markers based upon the rearrangement of immunoglobulin heavy-chain genes were generated for each patient and used for polymerase chain reaction (PCR) detection of residual myeloma cells. Fifty-one patients entered the program and 36 achieved CR. After transplantation, molecular monitoring was performed on 29 patients (15 autologous and 14 allogeneic transplants) who had molecular markers.

RESULTS

Our data show that molecular remissions are rarely achieved (7%) with high-dose chemotherapy followed by single or double autografting. In addition, virtually all peripheral blood progenitor cell and bone marrow samples contained residual myeloma cells, even when sample collection was scheduled after repeated courses of high-dose chemotherapy. All patients autografted with PCR-positive cells remain positive, and eight of 15 have relapsed. Two patients were autografted with PCR-negative cells: one is in clinical and molecular remission, and one relapsed 25 months after the transplant. In the allografting setting, a higher proportion of patients (50%) achieved molecular remission; there were two relapses, one in the PCR-positive group and one in the PCR-negative group.

CONCLUSION

This is the first large study of molecular remissions in myeloma patients to use a PCR-based approach utilizing patient-specific tumor markers. The sizeable fraction of patients who achieved molecular remission after allografting with peripheral blood progenitor cells represents a promising finding in an incurable disease.

A High Frequency of Circulating B Cells Share Clonotypic Ig Heavy-Chain VDJ Rearrangements With Autologous Bone Marrow Plasma Cells in Multiple Myeloma, as Measured by Single-Cell and In Situ Reverse Transcriptase-Polymerase Chain Reaction

In multiple myeloma (MM), the VDJ rearrangement of the immunoglobulin heavy chain expressed by MM plasma cells provides a unique clonotypic marker. Although clonotypic MM cells have been found in the circulation, their number has been controversial. Our objective was to provide direct evidence, using single-cell assays, for the frequency of clonotypic cells in blood of 18 MM patients, and to confirm their identity as B cells. The clonotypic Ig heavy-chain (IgH) VDJ was determined from single plasma cells using consensus reverse transcriptase-polymerase chain reaction (RT-PCR), subcloning, and sequencing. For all patients, using patient-specific primers, clonotypic transcripts were amplified from 10 or more individual plasma cells. Using in situ RT-PCR, for all patients greater than 80% of plasma cells were found to be clonotypic. Three separate methods, RT-PCR, single-cell RT-PCR, and in situ RT-PCR, were used to analyze clonotypic cells in peripheral blood mononuclear cells (PBMC) from MM patients. Sequencing of the IgH transcripts expressed by individual cells obtained by limiting dilution of freshly isolated PBMC from a MM patient showed that all B cells expressed an identical CDR3. This intraclonal homogeneity indicates an escape from antigenic-selection, characteristic of malignant B cells. For this patient, the frequency of clonotypic PBMC, about 25%, was comparable to the number of PBMC B cells (34%). Because the PBMC included less than 1% plasma cells, virtually all clonotypic PBMC must be B cells. Using single-cell RT-PCR, clonotypic IgH transcripts were identified in individual sorted B cells from blood. To accurately quantify the number of clonotypic B cells, sorted B cells derived from 18 MM patients (36 samples) and 18 healthy donors (53 samples) were analyzed using in situ RT-PCR with patient-specific primers. Clonotypic transcripts were not detectable among normal B cells. For the 18 MM patients, a mean of 66% ± 4% (SE) of blood B cells were clonotypic (range, 9% to 95%), with mean absolute number of 0.15 ± .02 × 109/L blood. Over time in individual patients, conventional chemotherapy transiently decreased circulating clonotypic B cells. Their numbers were increased in granulocyte colony-stimulating factor (G-CSF)– mobilized blood of one patient. However, clonotypic B cells of a one patient became undetectable after allogeneic transplant, correlating with complete remission. Although contributions to MM spread and progression is likely, their malignant status and impact has yet to be clarified. Their high frequency in the blood, and their resistence to conventional chemotherapy suggests that the number of circulating clonotypic cells should be clinically monitored, and that therapeutic targeting of these B cells may benefit myeloma patients.

© 1998 by The American Society of Hematology.

A High Frequency of Circulating B Cells Share Clonotypic Ig Heavy-Chain VDJ Rearrangements With Autologous Bone Marrow Plasma Cells in Multiple Myeloma, as Measured by Single-Cell and In Situ Reverse Transcriptase-Polymerase Chain Reaction

In multiple myeloma (MM), the VDJ rearrangement of the immunoglobulin heavy chain expressed by MM plasma cells provides a unique clonotypic marker. Although clonotypic MM cells have been found in the circulation, their number has been controversial. Our objective was to provide direct evidence, using single-cell assays, for the frequency of clonotypic cells in blood of 18 MM patients, and to confirm their identity as B cells. The clonotypic Ig heavy-chain (IgH) VDJ was determined from single plasma cells using consensus reverse transcriptase-polymerase chain reaction (RT-PCR), subcloning, and sequencing. For all patients, using patient-specific primers, clonotypic transcripts were amplified from 10 or more individual plasma cells. Using in situ RT-PCR, for all patients greater than 80% of plasma cells were found to be clonotypic. Three separate methods, RT-PCR, single-cell RT-PCR, and in situ RT-PCR, were used to analyze clonotypic cells in peripheral blood mononuclear cells (PBMC) from MM patients. Sequencing of the IgH transcripts expressed by individual cells obtained by limiting dilution of freshly isolated PBMC from a MM patient showed that all B cells expressed an identical CDR3. This intraclonal homogeneity indicates an escape from antigenic-selection, characteristic of malignant B cells. For this patient, the frequency of clonotypic PBMC, about 25%, was comparable to the number of PBMC B cells (34%). Because the PBMC included less than 1% plasma cells, virtually all clonotypic PBMC must be B cells. Using single-cell RT-PCR, clonotypic IgH transcripts were identified in individual sorted B cells from blood. To accurately quantify the number of clonotypic B cells, sorted B cells derived from 18 MM patients (36 samples) and 18 healthy donors (53 samples) were analyzed using in situ RT-PCR with patient-specific primers. Clonotypic transcripts were not detectable among normal B cells. For the 18 MM patients, a mean of 66% ± 4% (SE) of blood B cells were clonotypic (range, 9% to 95%), with mean absolute number of 0.15 ± .02 × 109/L blood. Over time in individual patients, conventional chemotherapy transiently decreased circulating clonotypic B cells. Their numbers were increased in granulocyte colony-stimulating factor (G-CSF)– mobilized blood of one patient. However, clonotypic B cells of a one patient became undetectable after allogeneic transplant, correlating with complete remission. Although contributions to MM spread and progression is likely, their malignant status and impact has yet to be clarified. Their high frequency in the blood, and their resistence to conventional chemotherapy suggests that the number of circulating clonotypic cells should be clinically monitored, and that therapeutic targeting of these B cells may benefit myeloma patients.

© 1998 by The American Society of Hematology.