Negative immunomagnetic ex vivo purging combined with high-dose chemotherapy with peripheral blood progenitor cell autograft in follicular lymphoma patients: evidence for long-term clinical and molecular remissions.

The feasibility and efficacy of a novel immunomagnetic ex vivo negative purging method was evaluated on peripheral blood progenitor cells (PBPC) from 13 non-Hodgkin's lymphoma patients (eight follicular, FL; three mantle cell, MCL; two FL with histologic transformation). A peculiar feature of the study was the collection of PBPC after prolonged tumor debulking. Our method included a stem cell enrichment phase followed by cell incubation with anti-B cell MoAbs (anti-CD19, CD20, CD22, CD23), addition of immunobeads, and then positive cell removal by passage on a Max-Sep (Baxter Immunotherapy) cell separator. Engraftment was rapid and stable. Hematological values were assessed 1 and 2 years after the autograft. Purging efficacy was molecularly assessed in a panel of 11 patients who showed persistence of PCR-detectable lymphoma cells on PBPC harvests despite intensified chemotherapeutic debulking. PCR-negativity was obtained in vitro and persisted in vivo after autograft in three FL patients; five more FL patients, whose purged PBPC were PCR+, converted to stable (3 patients) or fluctuating (two patients) PCR negativity after autograft. MCL patients never reached PCR negativity. Thus, ex vivo purging may have a role for FL patients harvesting PCR-positive PBPC after intensified chemotherapy. In contrast, the addition of ex vivo purging seems to be of little if any benefit for MCL patients.

In vitro growth and quantification of early (CD33-/CD38-) myeloid progenitor cells: stem cell factor requirement and effects of previous chemotherapy.

BACKGROUND AND OBJECTIVE: All culture systems exploring the early (pre-CFU) hematopoietic compartment are generally complex, time-consuming and unsuitable for routine application. The aim of our study was to develop a stroma-free culture system to quantify early bone marrow (BM) myeloid progenitor cells. DESIGN AND METHODS: Low density, progenitor cell enriched BM cells underwent a double cytotoxic treatment with CD38 and CD33 monoclonal antibodies + rabbit complement, which depleted 99% of CFU-GM and BFU-E. Then they were cultured, both in agar and in limiting-dilution liquid culture, in the presence of 5637 cell line supernatant (containing GM-CSF, G-CSF and interleukin 1 ), stem cell factor (SCF) and interleukin 3 (IL3). RESULTS: The largest number (median 14.9 on 1x10(5) cells) and size (>50,000 cells) of myelomonocytic cell clones from CD33Eth /CD38Eth progenitors was reached after 3-4 weeks of liquid culture. SCF, but not IL3, was essential for that growth. The frequency of CD33-/ CD38- progenitors grown in liquid culture was approximately three times greater than the LTC-IC frequency in the same cell suspension. An average 93% of CD33-/CD38- progenitors displayed HLA-DR antigens and 43% generated secondary CFU-GM. In the BM of 9/10 patients, previously exposed to chemotherapy, CD33-/CD38- progenitor frequency was quite low (median 0.9 on 1x10(5) cells), in spite of normal cellularity and morphology and sustained disease remission. INTERPRETATION AND CONCLUSIONS: CD33-/CD38- progenitors can be grown and quantified in a stroma-free culture system in a relatively short time. The test can reveal long-lasting, subclinical BM damage induced by chemotherapy and could also be valuable for estimating the amount of early myeloid progenitors for transplantation purposes.

Hemopoietic progenitor cell mobilization and harvest following an intensive chemotherapy debulking in indolent lymphoma patients.

An in vivo purging with intensive debulking chemotherapy prior to peripheral blood progenitor cell (PBPC) collection may reduce the risk of tumor contamination of the harvest products; however, it is usually associated with a marked reduction in PBPC mobilization. These issues have been considered while designing an adapted version of the high-dose sequential regimen for patients with lymphoid malignancies and bone marrow involvement. To reduce tumor contamination risks, PBPC collection was postponed to the end of the high-dose phase; however, in order to enhance progenitor cell mobilization, a chemotherapy-free lag period was introduced prior to the final mobilizing course. Thirty-nine patients (median age 47 years, range 26-62) with previously untreated indolent lymphoma entered this pilot study; all had advanced-stage disease, and 29 had overt marrow involvement. Sufficient numbers of PBPC to perform autograft with safety were harvested in 34 patients, with a median of 3 (range 2-5) leukaphereses. A median of 14.8 x 10(6) (range 2-51) CD34+/kg and 32.6 x 10(4) (range 1.77-250) colony forming units-granulocyte/macrophage/kg were collected per patient. In univariate analysis, the duration of the chemotherapy-free interval prior to the final mobilizing course, i.e. > or <65 days, was the most significant variable influencing progenitor mobilization. These data suggest that extensive in vivo tumor debulking is feasible provided that a sufficient chemotherapy-free period preceding the mobilizing course is allowed in order to allow a full recovery of marrow functions.

A single step density gradient separation for large scale enrichment of mobilized peripheral blood progenitor cells collected for autotransplantation.

Peripheral blood leukocytes are becoming the preferred source of hematopoietic progenitor/stem cells for autologous transplantation. However, in vitro purging procedures are complex and expensive when applied to peripheral blood progenitor cells harvests. This is mainly due to the large quantities of nucleated cells present in leukapheresis collections. Aiming to reduce total cellularity without significant loss of CD34+ cells, we developed an in vitro cell separation procedure based on ficoll/metrizoate gradient used at a final density of 1.067 g/ml. To obtain this density, standard Lympho-prep (1.077 g/ml) was diluted with normal saline solution (NaCl 9 g/l). Twenty-six leukapheresis collections (median cellularity 21.1 x 10(9), range 2.8-60) from 14 patients with non-Hodgkin's lymphoma, multiple myeloma or plasma cell leukemia were processed (median two leukaphereses per patient). Mean (+/- s.d.) recovery of total nucleated cells, CD34+ cells and CFU-GM was 20.9 +/- 10%, 74.7 +/- 22% and 70.5 +/- 19%, respectively. Cumulative per patient progenitor cell recovery was always above 50%, and as high as 80% in 10/14 patients, while total cellularity was reduced to a median 21.5% (10-33%) of pre-separation values. Contaminating neoplastic cells, identified by immunofluorescence in five collections, were reduced by 1-2 logs. The results indicate that our density gradient separation is an effective method to reduce total cellularity prior to immunological purging, without significant loss of progenitor cells.

Peripheral blood progenitor cell mobilization in patients with primary refractory lymphoma or at first relapse: comparison with patients at diagnosis and impact on clinical outcome.

Peripheral blood progenitor cell (PBPC) mobilization was evaluated in 53 patients receiving the high-dose sequential (HDS) regimen: 27 had non-Hodgkin's lymphoma or Hodgkin's disease, primary refractory or at first relapse, 26 had non-Hodgkin's lymphoma at diagnosis. Mobilization was assessed following either 7 g/m2 cyclophosphamide (48 patients) or 2 g/m2 etoposide, both followed by G-CSF (filgrastim) at 5 microg/kg/d. PBPC mobilization was significantly higher in patients at diagnosis compared to refractory/relapsed patients (median peak values of circulating CFU-GM: 25,209/ml v 4270/ml, P < 0.0001 and CD34+ cells: 286/microl v 47/microl, P < 0.0001). All patients receiving HDS as up-front treatment mobilized enough PBPC for an autograft, often requiring a single leukapheresis; whereas only 15 patients under salvage treatment with HDS were able to complete PBPC autograft. Bone marrow (BM) cells, alone or with PBPC, were needed in six patients, and autograft could not be performed in six patients. Among refractory/relapsed patients, those having a high PBPC mobilization experienced a significantly longer EFS compared to those who had not; autograft completion also significantly enhanced EFS. Thus, the use of an effective mobilizing protocol does not ensure adequate PBPC mobilization in moderately pretreated patients; low mobilization must be considered as an early sign of poor outcome in patients receiving a high-dose salvage programme.

Molecular monitoring of minimal residual disease in follicular and mantle cell non-Hodgkin's lymphomas treated with high-dose chemotherapy and peripheral blood progenitor cell autografting.

Minimal residual disease (MRD) was evaluated in 30 patients with follicular or mantle cell non-Hodgkin's lymphoma (NHL) undergoing an intensive treatment with high-dose sequential (HDS) chemotherapy and peripheral blood progenitor cell (PBPC) autografting. To minimize the potential tumor cell contamination, PBPC harvests were scheduled at the end of HDS pretransplant phase. All patients had advanced-stage disease and most of them presented with bone marrow (BM) involvement. A tumor marker could be generated in 90% of patients using bcl-2 or lg heavy-chain genes. MRD was analyzed on PBPC, BM harvests, and after autografting by polymerase chain reaction (PCR). All evaluable follicular and 6 of 9 mantle cell patients achieved clinical complete remission. PCR negativity of PBPC and/or BM harvests was documented in 68% of follicular and 12% of mantle cell lymphomas. Molecular remission of PBPC and/or BM harvests was achieved in 9 of 15 patients with overt marrow involvement and in all patients with only molecular marrow infiltration at onset. Molecular follow-up was conducted on 14 patients: all 7 evaluable patients who received at least one PCR-negative graft maintained the negative status at a median follow-up of 24 months and none of them relapsed so far. Thus, the results show that (1) a molecular marker to monitor MRD can be obtained in most follicular and mantle cell NHL patients, (2) the HDS regimen may provide PCR-negative PBPC and/or BM harvests even from patients with BM disease, and (3) autograft with at least one PCR-negative harvest is associated with a durable clinical and molecular remission.

Both early and committed haemopoietic progenitors are more frequent in peripheral blood than in bone marrow during mobilization induced by high-dose chemotherapy + G-CSF.

Haemopoietic growth factor administration following high-dose chemotherapy markedly amplifies progenitor cell pool in the peripheral blood (PB). Collection and reinfusion of these cells enable rapid haemopoietic reconstitution following autograft. Less is known on engraftment potentiality of bone marrow (BM) cells taken under analogous conditions. To investigate this tissue, PB and BM were evaluated simultaneously during maximal mobilization in a series of 14 patients undergoing the HDS chemotherapy programme. A significantly higher growth of committed progenitors was found from PB rather than from BM (663 +/- 123 v 267 +/- 40 CFU-GM/10(5) MNC, respectively). Also, significantly more CFU-GM could be collected by a median of three leukaphereses, compared to those harvested from BM (158 +/- 31 v 16 +/- 4 x 10(4) CFU-GM/kg, respectively). Most mobilized CFU-GM were phenotypically immature (CD15-); in addition, circulating cells included primitive progenitors, as assessed by LTC-IC assay, or by evaluation of non-proliferating pre-CFU-GM, selected by an anti-CD71 immunotoxin. The amount of pre-CFU-GM determined by both techniques was consistently higher in PB than in BM. Moreover, a direct correlation could be established between circulating CFU-GM and primitive precursors. Thus, during optimally induced mobilization, PB contains many more haemopoietic progenitors, of both committed and primitive stages, than does BM. Under such conditions, PB is probably the best source of material for graft purposes.

Circulating progenitors following high-dose sequential (HDS) chemotherapy with G-CSF: short intervals between drug courses severely impair progenitor mobilization.

Sequential administration of high-dose chemotherapy courses possibly allows extensive in vivo purging before circulating progenitor collection for autograft. To evaluate whether progenitor cell mobilization was negatively affected by repeated high-dose chemotherapy courses, we studied 23 lymphoma patients undergoing the HDS regimen. The scheme includes the sequential administration of cyclophosphamide (CY) given at 7 g/m2 and etoposide (VP16) given at 2 g/m2, each followed by G-CSF (filgrastim) at 5 micrograms/kg/day. Eleven patients received the standard HDS sequence, with a short interval between first and second myelotoxic courses of less than 45 days (median: 30 days); the remaining 12 patients received a modified HDS where the interval between first and second high-dose course was protracted over 2 months (median: 70 days); in this latter group, 2 to 4 conventional debulking courses were delivered prior to HDS. In patients receiving the standard HDS, progenitor mobilization following the first course was consistently high (median circulating CFU-GM/ml peak value: 29,022); however, significantly lower values were observed at the second course (median CFU-GM/ml peak value 3757, P = 0.002). Circulating BFU-E and CD34+ cell values paralleled those of CFU-GM. No significant difference was observed in progenitor mobilization following either course in patients receiving HDS with extended interval (median circulating CFU-GM/ml peak value: 14,363 vs 9208, at first and second course respectively, P = 0.27). Eleven patients had their progenitor cells harvested following the second delayed course and 2-4 leucaphereses allowed very satisfactory harvests in all of them (CFU-GM/kg ranging from 39-340 x 10(4)).(ABSTRACT TRUNCATED AT 250 WORDS)

Haematological support of high-dose sequential chemotherapy: clinical evidence for reduction of toxicity and high response rates in poor risk lymphomas.

The toxicity and feasibility of a high-dose sequential (HDS) chemotherapy programme delivered with growth factor support were evaluated in patients with intermediate and high-grade non-Hodgkin's lymphoma (NHL) or with progressive Hodgkin's disease. The scheme includes the sequential administration of single cytotoxic drugs at very high doses followed by intensified treatment with circulating progenitor autograft. In some instances, the original HDS scheme, initially designed at the Milan Cancer Center, was partially modified and intensified with a preliminary debulking phase. The use of G-CSF (filgrastim) made toxicity in the high-dose phase acceptable and allowed good harvests of peripheral blood progenitor cells (PBPC); the use of PBPC in the final autografting phase resulted in low haematological toxicity. Of 71 patients with NHL treated at our institution with either the original or the intensified HDS version, the overall toxicity-related mortality was 5.6%, thus comparable to lethal toxicity commonly associated with conventional chemotherapy. Adequate PBPC harvests are crucial for good tolerability of the programme. Optimal harvests are generally obtained in patients without neoplastic marrow infiltration while patients with marrow disease often have a poorer mobilisation. However, an optimally time-spaced chemotherapy debulking might also restore sufficient mobilisation in these latter patients. In terms of therapeutic efficacy, HDS had produced promising results since the initial experience in relapsed patients. More recently, HDS was evaluated as first-line treatment in a series of 22 consecutive patients, presenting with advanced-stage, intermediate-grade NHL other than diffuse large cell subtype. A CR rate of 82% was obtained following HDS, with a projected survival of 86% at five years. Thus, delivery of an intensive high-dose chemotherapy programme with haematopoietic growth factor support was found to be feasible and reasonably safe. The high anti-tumour efficacy of such a scheme makes it suitable for wider applicability in all those chemosensitive tumours where a dose increase might enhance the chance of cure.

Selection and characterization of early hematopoietic progenitors using an anti-CD71/S06 immunotoxin.

Most recently reported methods to select early hematopoietic cells basically rely on the depletion of committed progenitors. This task is generally accomplished by laborious procedures, which are sometimes difficult to reproduce. To simplify the selection method, we took advantage of the expression of the transferrin receptor (CD71) by proliferating committed progenitors and the lack of CD71 on noncycling immature progenitors. A monoclonal antibody (MAB) reactive with CD71 has been conjugated to the Saponaria officinalis seed ribosome-inactivating protein (SO6). The immunotoxin (IT) complex was used at increasing concentrations on normal non-phagocytizing bone marrow cells. A complete and reproducible killing effect on myeloid (colony-forming unit-granulocyte/macrophage [CFU-GM]) and erythroid (burst-forming unit-erythroid [BFU-E]) progenitors was observed for IT concentrations of 1 x 10(-7) M. Unconjugated SO6 or anti-CD71 MAB had no effect on cell growth and viability. IT-resistant cells were able to generate CFU-GM after 7, 14, and 21 days of suspension culture in the presence of 5637 CM. Maximal CFU-GM values were obtained at day 21 and nearly approached the pretreatment values (mean 2587 vs. 3877 CFU-GM/mL). Growth factor enhancement of CFU-GM yield was obtained only by stem cell factor (SCF) at day 7; SCF, as well as granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-3 (IL-3), had an enhancing effect at days 14 and 21. IT toxicity on highly immature progenitors was ruled out by evaluating the growth of long-term culture-initiating cells (LTC-IC) from IT-treated cultures. LTC-IC frequency was found to be 1 out of 1506 seeded cells, which is within the range of normal untreated BM cells. In conclusion, anti-CD71 IT allows a simple and complete depletion of committed progenitors while sparing immature hematopoietic cells. The high CD71 expression by leukemic cells makes the procedure potentially suitable for in vitro purging.