Potassium antimonyl tartrate induces caspase- and reactive oxygen species-dependent apoptosis in lymphoid tumoral cells

The metalloid salt potassium antimonyl tartrate (PAT), previously used as an antiparasitic agent, has recently been shown to exert cytotoxicity towards acute promyelocytic leukaemia cells like arsenical compounds. In this study, we have investigated its effects towards human lymphoid malignant cells and compared them with those of arsenic trioxide (As2O3). Like As2O3, PAT was found to inhibit cell growth of various lymphoid cell lines, deriving from either acute lymphoid leukaemias (Jurkat, Molt-4 and Nalm-6) or lymphomas (Daudi, Raji and Rec1). PAT toxicity was linked, at least in part, to induction of apoptosis in both Daudi and Jurkat cells, which was dependent on caspase activity. This apoptotic process was also associated, similarly to that triggered by As2O3, with loss of mitochondrial potential and enhanced cellular production of reactive oxygen-related species. It was enhanced by co-treatment with the pro-oxidant buthionine sulphoximine and abolished in response to the antioxidant N-acetylcysteine, thus underlining that PAT toxicity, similarly to that of As2O3, is probably modulated by the redox status of the cells. PAT, used at concentrations in the micromolar range that are thought to be clinically achievable, was also demonstrated to markedly decrease the viability of primary cultured tumoral B cells that originated from 18 patients suffering from chronic lymphoid leukaemia whereas normal lymphocytes were less sensitive. These data therefore suggest that PAT may deserve to be evaluated in the treatment of some lymphoid malignancies.

High multidrug resistance protein activity in acute myeloid leukaemias is associated with poor response to chemotherapy and reduced patient survival

Multidrug resistance protein (MRP) activity was investigated in 44 newly diagnosed acute myeloid leukaemia (AML) patients using a functional assay based on efflux of carboxy-2',7'-dichlorofluorescein, an anionic dye handled by both MRP1 and MRP2. Elevated MRP transport was detected in 29% of cases, but was not significantly correlated with sex, age, white blood cell count at diagnosis or karyotype. In contrast, it was associated with secondary AML (P = 0.002), CD34 positivity (P = 0.041) and P-glycoprotein activity (P = 0.01). There was a lower rate of complete remission in MRP-positive patients versus MRP-negative patients (23% versus 81%; P = 0.001); overall survival was also better for MRP-negative patients (P = 0.004). These data indicate a probable role for MRP activity in the clinical outcome of AML.

Treatment of metastatic renal cell carcinoma with activated autologous macrophages and granulocyte--macrophage colony-stimulating factor

Fifteen patients with progressive metastatic renal cell carcinoma were treated with granulocyte-macrophage colony-stimulating factor and intravenous infusions of activated autologous macrophages (AAMs). The latter were prepared from leukapheresis-separated mononuclear cells cultured in the presence of granulocyte-macrophage colony-stimulating factor, exposed to gamma interferon, and submitted to elutriation to separate AAMs. Three intravenous injections of AAMs were performed within a 2-week interval. This treatment cycle was repeated once or twice, in cases of tumor response or stabilization. Ninety-seven preparations containing a mean 3 x 10(9) AAMs were administered and usually well tolerated. One partial response, eight stabilizations and six progressions were observed. The median time to progression and median overall survival time after inclusion were 7 and 9 months, respectively. The cells injected did not accumulate substantially in tumor lesions, as shown by scintigraphic imaging of indium-111-labeled AAMs. Thus, combined granulocyte-macrophage colony-stimulating factor and AAM treatment was well tolerated and resulted in transitory stabilization (n = 8) or partial regression (n = 1) in 9 of 15 patients.

Jumping translocation in acute leukemia of myelomonocytic lineage: a case report and review of the literature

Jumping translocation (JT) is a very rare cytogenetic event, occurring especially in cancer. We describe a case of secondary acute monocytic leukemia (AML5b) with a JT involving the 3q13-3qter segment and leading to a partial trisomy 3. Each clone with JT was associated with trisomy 8 or tetrasomy 8. The literature of JT in AML cases is reviewed: only 13 cases of AML associated with JT have been previously described, seven of which are AML4/5 FAB subtype. Jumping translocation involvement in leukemogenesis is discussed. Leukemia (2000) 14, 119-122.

Use of the anionic dye carboxy-2',7'-dichlorofluorescein for sensitive flow cytometric detection of multidrug resistance-associated protein activity

Multidrug resistance-associated protein (MRP) and P-glycoprotein are drug efflux pumps conferring multidrug resistance to tumor cells and sharing numerous substrates. In order to determine a flow cytometric assay allowing to analyse MRP activity in cancerous cells in a sensitive and specific manner, cellular accumulation and efflux of the anionic fluorescent dye carboxy-2',7'-dichlorofluorescein (CDF) were studied by flow cytometry using mainly MRP-overexpressing lung GLC4/Sb30 cells and parental GLC4 cells. GLC4/Sb30 cells were found to display reduced accumulation and enhanced efflux of the dye when compared to their parental counterparts. Probenecid, a well known blocker of MRP, strongly enhanced CDF accumulation in GLC4/Sb30 cells through inhibiting efflux of the dye; it also increased CDF levels in GLC4 cells, although to a lesser extent, which may likely be linked to the low, but detectable, expression of MRP in these cells. Comparison of CDF retention with that of calcein demonstrated that the former dye was the most efficiently effluxed by GLC4/Sb30 cells. In contrast to MRP overexpression, that of P-glycoprotein was not found to alter cellular CDF labelling whereas it strongly impaired calcein staining. These results indicate that CDF is a substrate for MRP, but not for P-gp, which may likely be useful for sensitive and specific flow cytometric determination of MRP activity in clinical samples.

HLA-G protein expression is not induced during malignant transformation

To evaluate the biological relevance of HLA-G expression during tumoral transformation, we analyzed its expression in different malignant cells and immune effector cells infiltrating solid tumors. Our analysis of 33 tumor cell lines and 53 tumoral biopsies demonstrated that: i) six tumor cell lines display HLA-G transcription with differential alternative splicing patterns and only Jeg3 choriocarcinoma and MCF-7 breast adenocarcinoma cell lines express HLA-G translated products; and ii) HLA-G antigens are not expressed in malignantly transformed cells derived from lung (n=18), liver (n=5), colon (n=5), breast (n=10), kidney (n=5), ovary (n=5), and larynx (n=5) tissues ex vivo. The healthy tissues surrounding these tumor tissues do not express HLA-G molecules either. On the other hand, surprisingly, HLA-G products were detected in activated macrophages and dendritic cells localized in tumoral biopsies of 5 out of 18 different lung carcinomas. No HLA-G labelling was observed in resident mononuclear phagocytes of surrounding healthy tissues. Our observations clearly demonstrate that HLA-G is not a marker of malignant cells but appears as a gene expressed in tumor-associated macrophages and dendritic cells, preferentially in those recruited in lung carcinomas. Our findings suggest that specific environmental factors around lung tumors could be involved in the induction of HLA-G protein expression.

Multidrug resistance analysis in lymphoproliferative disease of large granular lymphocytes

Multi-drug resistance (MDR) phenotype contributes to the ineffectiveness of chemotherapy. P-glycoprotein (PgP) and lung resistance protein (LRP) are proteins implicated in chemoresistance. We analysed the expression of PgP and LRP respectively in 17 and 15 cases of lymphoproliferative disease of granular lymphocytes (LDGL) including 10 cases of clonal large granular lymphocytic (LGL) leukaemia, six cases of oligoclonal (n = 5) and polyclonal (n = 1) CD3+ lymphoproliferation and one case of CD3- NK lymphocytosis. Functional PgP activity, as determined by Rh123 dye efflux assay, was found in all the patients. The mean percentage of effluxing cells was 47 +/- 22%, compared to 35 +/- 8% on normal lymphocytes (P<0.04). The efflux was blocked in the presence of verapamil, a PgP revertant agent. A high proportion of CD57+ cells (66 +/- 10%) from these patients expelled Rh123. Functional PgP activity was associated with expression of MDR1 mRNA. By using immunocytochemistry, LRP expression was detected in 11/15 patients (73%). 7/10 LGL leukaemia patients presented a LRP+/Efflux+ phenotype and 5/7 had LRP+/Efflux+/MDR1 mRNA+ phenotype. These findings suggest that the PgP+/LRP+ phenotype is frequently observed in LDGL. Its clinical relevance in aggressive cases remains to be determined.

Loss of HLA molecules in B lymphomas is associated with an aggressive clinical course

Major histocompatibility complex class I molecule expression is reduced in some malignant tumours permitting escape from immune surveillance and is therefore associated with a poor prognosis. Seven cases of non-Hodgkin lymphomas out of 300 cases of malignant lymphoproliferative disorders totally lacked expression of class I molecules as determined by flow cytometry. Clinical data confirmed a particular aggressiveness of these cases with frequent extra-nodal involvement, a poor international prognostic index, a histological high grade and a poor outcome leading to early death in five of the seven cases. A previous diagnosis of follicular lymphoma characterized by bcl-2 rearrangements was made in four of these cases. HLA-G (class Ib gene), which is reported to bind killer inhibitory receptors on NK cells, was absent from the cell surface. However, it was detected in three out of four cases at the mRNA level with transcripts encoding soluble forms. Additional analysis revealed other abnormalities: class II was negative in four out of the seven NHL cases and decreased expression of beta2 microglobulin was observed in all cases. Peptide transporter proteins (TAP1) were detected in various degrees by immunocytochemistry. These observations showed that total lack of class I or class II molecules is a rare event in NHL and is associated with a poor prognosis. This could support a role for specific autologous T cells in immune surveillance.

Differential expression and activity of P-glycoprotein and multidrug resistance-associated protein in CD34-positive KG1a leukemic cells

CD34+ acute myeloid leukemias generally respond poorly to chemotherapy when compared to CD34- myeloid leukemias. In order to contribute to the analysis of the mechanisms involved in this drug resistance, expression and activity of P-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP), two drug efflux pumps conferring multidrug resistance, have been investigated in the CD34+ KG1a leukemic myeloid cell line and in two CD34- K562 and HL60 leukemic myeloid cell lines. Reverse transcription-polymerase chain reaction and dye efflux assays revealed that KG1a cells express P-gp but not MRP whereas neither P-gp nor MRP were detected in K562 and HL60 cells. In addition, KG1a cells were demonstrated to display resistance to anticancer drug substrates for P-gp such as vincristine and daunorubicin and to poorly accumulate vincristine. These results indicated that P-gp, in contrast to MRP, is expressed and functional in the drug-resistant CD34+ KG1a cell line, that may constitute a useful cellular model to analyze the constitutive chemoresistance of CD34+ acute myeloid leukemias.

Multicentric evaluation of the MDR phenotype in leukemia. French Network of the Drug Resistance Intergroup, and Drug Resistance Network of Assistance Publique-Hôpitaux de Paris

The wide discrepancies in the frequency of 'positive' samples for multidrug resistance (MDR) phenotype within the same type of tumor observed in the literature justified the need for the definition of consensus recommendations. To define standard techniques of MDR phenotype measurement, we ran a large multicentric evaluation of the different methods available. Thirty-six French centers participated in the study, and 742 samples of 2-10 x 10(6) viable cells were sent by overnight express mail between December 1993 and February 1996. The same batches of MRK16, 4E3 and UIC2 were used. Nineteen samples of leukemia (12 AML, 1 ALL, 6 lymphoproliferative syndromes) and six leukemic cell lines with different levels of MDR expression were tested. Five meetings reached agreement concerning the guidelines for each technique, except immunocytochemistry. The 19 fresh samples were tested by each center using one to four techniques among cytofluorometry, immunocytochemistry, functional tests and RT-PCR. Five samples were diagnosed as 'negative' according to local criteria, with few discordant results (0 to 16% of 'positive' results). For all the 14 remaining samples, large discrepancies were observed from center to center, and from one technique to another. No correlations could be found between techniques. Flow cytometric analysis of cells already exposed to MRK16 or control IgG2A, fixed in paraformaldehyde and sent to centers did not reduce the discrepancies between centers in two of the four samples with moderate expression, emphasizing the role of histogram interpretation. The use of alternative monoclonal antibodies (4E3 and UIC2) did not reduce the discrepancies observed. In a second step, the K562 parental cell line, a low resistant subline (K562/HHT100, x7 resistance index to DNR) and a high resistant subline (K562/HHT300, x125 resistance index to DNR) were sent blindly three times, with an increasing level of recommendations for flow cytometry. Dramatic improvements were observed in cytometric results when the result was expressed as the ratio of arithmetic mean of fluorescence of antibody (10 microg of MRK16)/arithmetic mean of fluorescence of control (10 microg IgG2A): the proportion of expected results increased from 61 to 100% for K562, and from 37 to 85% for K562/HHT100. For uptake and drug efflux measurements, the use of 1 h uptake of 0.1 microM of rhodamine, followed by 1 h efflux +/-10 microM of verapamil, permitted an increased reproducibility of the technique from 71 to 100% for K562 and K562/HHT100. Whatever the technique used, concordant results were obtained for K562/HHT300. The immunocytochemistry, using several antibodies (MRK16, JSB1 and C219) gave many non-interpretable results (44%), due to a frequent high background and discordant results between antibodies in the same centers, and discordant conclusions between centers. The group does not recommend this technique for circulating tumoral cells.

CpG methylation patterns in the 5' part of the nonclassical HLA-G gene in peripheral blood CD34+ cells and CD2+ lymphocytes

A dominant goal of research focused on the nonclassical human leukocyte antigen G (HLA-G) gene is to understand the molecular mechanism involved in its limited expression. In the present report, we examined DNA methylation as a potential regulatory mechanism of HLA-G transcription in two cell types of the adult lymphomyeloid lineage: CD2+ lymphocytes express several mRNA isoforms while transcripts are undetectable in CD34+ hematopoietic cells. The methylation status of 63 CpG sites in the promoter and in the 5' CpG island was established using bisulfite-treated genomic DNA sequencing. Methylation was first analyzed by the direct sequencing of bisulfite-treated and amplified products. The general patterns of CpG methylation in the 5' part of the gene were found to be similar for CD34+ cells and CD2+ lymphocytes: the distribution of methylation was not uniform across the 63 CpG sites. In the promoter region, both CpG dinucleotides were partially or fully methylated whereas in the CpG island, several CpG sites were totally demethylated. Unexpectedly, in HLA-G positive CD2+ lymphocytes, a great number of CpG dinucleotides displayed a higher frequency of methylation relative to that found in CD34+ cells. However, the sequence analysis of cloned products revealed that the molecules have different methylation patterns which suggests that the HLA-G gene is differentially expressed in CD2+ cells. Our results suggest that methylation is not the sole mechanism that achieves the repression of HLA-G transcription in immature CD34+ cells.

Inapparent polycythemia vera: an unrecognized diagnosis

PURPOSE

The Polycythemia Vera Study Group (PVSG) has established useful criteria for the diagnosis of polycythemia vera. In some circumstances, an increase of plasma volume (PV) masks that of red cell mass (RCM), with hemoglobin (Hb) and hematocrit (Ht) remaining normal. This defines the concept of inapparent polycythemia.

PATIENTS AND METHODS

One hundred and three patients seen in the hematology unit with the diagnosis of polycythemia vera were studied. There were 55 males and 48 females with a median age of 59 years. Ninety-five patients fulfilled the PVSG criteria. Spontaneous erythroid colonies and low serum erythropoietin level confirmed the diagnosis in the 8 other cases. Patients were classified according to Hb and Ht level.

RESULTS

Group A consisted of 85 patients with increased Hb and Ht defined, respectively, by Hb > 18 g/dl, Ht > 0.52 in males and Hb > 16 g/dL, Ht>0.47 in females. Group B included 18 patients (17%) with inapparent polycythemia vera (IPV) defined by a normal Hb and Ht value at diagnosis. In this group, the reasons to perform RCM were as follows: splenomegaly associated with increased platelets and/or leucocytes counts (n = 8), portal vein thrombosis (n = 5), increased platelets or leucocytes counts without splenomegaly (n = 3), and isolated splenomegaly (n = 2). The two groups were balanced in terms of age, sex, leucocyte, serum iron, and platelet level. Hemoglobin and Ht levels were significantly different between the two groups. The difference between the PV was indeed highly significant. The mean PV increase was + 9.5% (nL < +20%) in group A versus + 36.3% in group B (P < 0.00005). Red cell mass was not different between the two groups.

CONCLUSIONS

Increased Hb or Ht should constitute the sole criteria for RCM determination. In the context of portal vein thrombosis, isolated hyperleucocytosis, thrombocytosis, or splenomegaly, a RCM should be performed. The frequency of IPV remains to be specified but the diagnosis of polycythemia vera is probably underestimated.

Inhibition of P-glycoprotein activity in human leukemic cells by mifepristone

The antiprogestatin drug mifepristone has previously been shown to potentiate anti-cancer drug activity in rodent multidrug-resistant cell lines through inhibition of P-glycoprotein (P-gp) function. In order to characterize P-gp-mifepristone interactions in human tumoral cells, we have studied the effect of the antiprogestatin agent on P-gp activity in human CD34+ leukemic cells known to display high levels of P-gp-related drug efflux. P-gp-mediated transport of the fluorescent dye rhodamine 123 occurring in the CD34+ KG1a myeloid leukemia cell line was found to be strongly inhibited by mifepristone in a dose-dependent manner. Similarly to verapamil, a well-known chemosensitizer agent, the antiprogestatin drug increased doxorubicin cytotoxicity in KG1a cells. Mifepristone, when used at a 10 microM concentration thought to be achievable in vivo without major toxicity, was also able to markedly decrease cellular rhodamine 123 efflux occurring in CD34+ blast cells isolated from six patients suffering from myeloid acute leukemias. These results thus indicate that mifepristone can strongly inhibit P-gp activity in human cells, including tumoral cells freshly isolated from patients, therefore suggesting that the clinical use of this compound may contribute to down-modulate P-gp-mediated drug resistance.

Internalization of human macrophage surface antigens induced by monoclonal antibodies

Drugs intended to be endocytosed by macrophages may be transported by MAbs directed against these cells. Twenty MAbs were investigated for this purpose. The binding of these MAbs to macrophages obtained from a 7 day culture of blood monocytes showed that anti-CD11b and anti-CD14 recognized the highest number of cell surface antigen sites. Further assays determined that anti-CD63, Mo5 and anti-CD33 were the MAbs that induced the strongest modulation of the corresponding antigens, the highest rate being with anti-CD63. Endocytosis of antigen-antibody complexes was evidenced by the presence of MAbs in the cytoplasm. Anti-CD63 MAbs induced the highest internalization in this assay. For most MAbs, however, the density of antigen sites and the intensity of antigen modulation were not predictive of the amount of MAb detected in the cytoplasm.

Quantification and molecular analysis of plasmatic HLA-BCw molecules with a locus B and Cw HLA specific mAb (B1.23.2 mAb)

Plasmatic HLA class I molecules were analysed quantitatively and qualitatively with a B and Cw locus-specific mAb, B1.23.2. sHLA-BCw were detected among all individuals with a wide range of concentration. The HLA-A29(19) allele was significantly associated with an increased sHLA-BCw mean concentration. Three different isoforms of relative molecular weights of 44, 39 and 36kDa were detected. The 39 kDa class I heavy chain was not detected after immunoprecipitation with mAb B1.23.2 in 17% of tested plasma, but was immunoprecipitated with W6/32 mAb.

Multi-drug resistance (MDR) activity in acute leukemia determined by rhodamine 123 efflux assay

We prospectively analyzed MDR functional activity by the Rh123 efflux assay in 84 de novo acute leukemias. Thirty of the 60 AML cases (50%) showed a positive dye efflux (in more than 10% of blast cells). In 19 cases, the dye efflux was superior to 30%. Twenty-four of the 30 efflux positive cases were CD34+ and could be studied in double staining. The mean percentage of effluxing CD34+ blast cells was 54%. There was a high correlation between CD34 expression and MDR activity (P < 10(-4)), MDR activity and PgP expression (P < 10(-6)). All the efflux negative samples were PgP negative. Nine efflux positive cases were PgP negative. Five of the 24 ALL were efflux positive. MDR activity did not correlate with FAB subtype (with the exception of AML3: 1/6 was efflux positive), age, white blood cell count or LDH level. Forty-seven AML patients were treated with conventional chemotherapy including cytarabine and an anthracycline. Thirty-one (66%) entered complete remission (CR). CR rate was statistically lower for efflux positive as compared to efflux negative patients, 46 vs 87% (P = 0.003), for PgP+ as compared to PgP- patients, 40 vs 78% (P = 0.01), for CD34+ as compared to CD34- patients, 45 vs 84% (P = 0.005). There was no correlation between P110 expression (32 AML cases studied) and FAB subtype, MDR status and clinical outcome. Two years survival was 20% for efflux positive patients as compared to 54% for efflux negative patients (P < 0.07), 15% for PgP+ vs 54% for PgP- patients (P < 0.04). The finding of efflux+/PgP- cases suggests the existence of other membrane efflux pumps. Rh123 efflux assay is straightforward in routine and could be included in MDR screening because of its potential interest in clinical outcome in AML.

Expression of p-glycoprotein in multidrug-resistant human leukemia k562 cells during erythroid-differentiation

Expression of P-glycoprotein (P-gp), the multidrug resistance gene product, has previously been shown to be downregulated during differentiation of normal haematopoietic cells. In order to determine whether such a regulation also occurs in leukemic cells, we have investigated the relevance of differentiation levels to P-gp expression in multidrug-resistant leukemia K562R/7 cells and in parental drug-sensitive K562 cells. These leukemic cells were exposed to hemin and sodium butyrate, two known inducers of erythroid differentiation. Analysis of hemoglobin-synthesizing cells indicated that hemin induced both K562R/7 and K562 cells to differentiate into erythroid cells while sodium butyrate led to hemoglobin synthesis in only K562 cells. Northern blotting and immunolabelling experiments revealed elevated levels of MDR1 mRNAs and P-gp in both untreated and hemin-treated K562R/7 cells while P-gp expression was not detected in both uninduced and hemin-induced K562 cells. Flow cytometric analysis of cellular doxorubicin retention demonstrated that K562R/7 cells poorly accumulated the anticancer drug regarless their level of differentiation. These results therefore suggest that erythroid differentiation of leukemic drug-resistant K562R/7 cells in response to hemin treatment did not result in major alteration of P-gp expression and activity.

Multidrug resistance in B-cell chronic lymphocytic leukemia

Multidrug resistance (MDR) was investigated in peripheral blood cells isolated from 40 patients with B cell chronic lymphocytic leukemia (B-CLL) and from 7 healthy volunteers, using a flow cytometric assay that detects cellular efflux of the fluorescent dye rhodamine 123 (Rh 123), which has been demonstrated to be transported from the cell by the P-glycoprotein pump. The proportion of B leukemic cells effluxing Rh 123 and thus displaying MDR was low (14 +/- 17%) in B-CLL and in only 4 cases did the contingent of B leukemic cells showing MDR represent more than 30% of the total leukemic cells. In contrast, a higher proportion of cells effluxing Rh 123 (44 +/- 13%) was demonstrated in normal B lymphocytes. No statistical correlation was found between the number of leukemic B cells displaying MDR and clinical parameters or previous treatment. These results clearly suggest that MDR activity is usually low in B-CLL.

Plasmacytoid CD8 lymphoma: morphologic and immunologic characterization

This study describes a 79 year-old female suffering from fever and lymphadenopathy. A lymph node biopsy showed diffuse infiltration of medium-sized cells with plasmacytoid features. The immunologic phenotype determined by cytometric analysis and immunochemistry showed suppressor T antigen (CD2, CD3, CD7, CD8) expression. Absence of CD5 expression characterized this abnormal T cell proliferation. Gamma T cell receptor rearrangement without immunoglobulin heavy-chain gene rearrangement confirmed the T lineage of these plasmacytoid cells and their clonality. Immunological studies are necessary for identification of this T lymphoma with B microscopic findings.

Improvement of hematologic recovery after high-dose intensification using peripheral blood progenitor cells (PBPC) mobilized by chemotherapy and GM-CSF

We have tested the efficiency of GM-CSF to mobilize peripheral blood progenitor cells (PBPC) and evaluated the hematological reconstitution after GM-CSF primed-PBPC infusion following myeloablative therapy. Twenty three patients suffering from hematological malignancies were included in this study. Starting 24 hours after completion of a standard dose chemotherapy including vindesine, cyclophosphamide, adriblastine, prednisone, (VCAP), 5 micrograms/kg sub-cutaneous daily dose GM-CSF was given for a median time of 14 days followed by three consecutives cycles of leukapheresis. Fifteen of these 23 patients underwent GM-CSF primed-PBPC autotransplantation following high dosed intensification regimen. PBPC collection and hematopoietic recovery were compared with a 15 patients control group who did not receive GM-CSF. No marrow or growth factors were administered after PBPC reinfusion in the two groups. VCAP/GM-CSF mobilization induced significantly higher yields of CFU-GM (3.8 fold) than did VCAP mobilization alone, 19 x 10(4)/kg (2-73) vs 5 x 10(4)/kg (2-27), (p < 0.005). The median number of days to achieve 1.10(9)/l neutrophils, platelet count > 20.10(9)/l and > 50.10(9)/l was significantly lower in the GM-CSF group than in the control group, respectively 13 vs 19 days (p = 0.04), 15.5 vs 27 days (p < 0.02), 19 vs 51 days (p < 0.01). When compared with the control group, transfusion requirements and median of hospital stay were both significantly decreased for the patients receiving GM-CSF primed-PBPC. Our study confirms that infusion of GM-CSF primed-PBPC as a sole source of hematopoietic support improves hematopoietic reconstitution following myeloablative therapy.