From September 1992 to January 1994, we evaluated the use of the CEPRATE SC stem cell concentrator (CellPro, Inc, Bothell, WA) to select CD34+ cells from the bone marrow (BM) of 25 patients with non-Hodgkin's lymphoma in complete remission. This system uses the biotinylated 12.8 IgM MoAb to select CD34+ cells. Cells are retained on an avidin column and detached by agitation. Fifteen patients have been transplanted with the CD34+ purified fraction. The CD34+ purified fraction of the 25 processed BMs contained a median of 0.54% of the original nucleated cells in a volume of 5 to 10 mL. The median concentration of CD34+ cells was 49% (range, 12% to 80%), and the median enrichment of CD34+ cells was 33-fold (range, 9- to 85-fold). This selected CD34+ fraction retained 60% (range, 15% to 95%) of late granulocyte-macrophage colony- forming units (CFU-GM), 55% (range, 12% to 99%) of early CFU-GM, and 31% (range, 2% to 100%) erythroid burst-forming units (BFU-E) corresponding to median enrichments of 22-fold (range, 1- to 71-fold), 19-fold (range, 2- to 58-fold), and 14-fold (range, 2- to 200-fold), respectively. There was a correlation between immune phenotypes and progenitor cells. In the initial buffy-coat fractions, the percentage of CD34+ cells was correlated to the cloning efficiency of both late CFU-GM (P < .05) and early CFU-GM (P < .001). In the final selected fraction, there was a correlation between the percentage of CD34+/CD33- and the cloning efficiency of early CFU-GM (P < .05) and between the percentage of CD34+/CD33+ and the cloning efficiency of late CFU-GM (P < .05). Lymphoma cells positive for t(14; 18) were found by polymerase chain reaction in 9 of 14 buffy coats tested before CD34+ cell purification. In 8 cases, the CD34(+)-selected fraction was found to be negative, and the CD34- fraction was found to be positive. After cryopreservation, the recoveries of progenitor cells in the CD34(+)- purified fraction were 79% for late CFU-GM, 71% for early CFU-GM, and 73% for BFU-E. The 15 patients transplanted with the concentrated CD34+ fraction received a median dose of 1 x 10(6) CD34+ cells/kg (range, 0.3 to 2.96) and 10.62 x 10(4) early CFU-GM/kg (range, 0.92 to 25.55). Median days to recovery to 0.5 x 10(9)/L neutrophils and 50 x 10(9)/L platelets were days 15 (range, 10 to 33) and 23 (range, 11 to 68), respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

To study the frontiers between pluripotent stem cells and committed progenitors and to further define the B-cell pathway in adult bone marrow (BM), CD34+ subpopulations and CD34- B-lineage cells were analyzed by multiparameter flow cytometry, studied by light and electron microscopy, and in short-term and long-term cultures (LTC). While the total CD34+ cells represent 4.9% +/- 0.8 of BM mononuclear cells within the lymphoid-blast window, 73.8 +/- 3.5%, 14.4 +/- 1.8% and 8.8 +/- 2.9% of them were CD34+ CD10- CD19-, CD34+ CD10+ CD19+, and CD34+ CD10+ CD19-, respectively. CD34+ CD10+ CD19+ cells represent a smal homogeneous TdT4 c micro-blast population. Although expressing CD38 and high level of HLA-DR antigens, like myeloid committed progenitors, they did not generate LTC, myeloid, and T lymphoid colonies suggesting that the CD34+ CD10+ CD19+ population represents exclusively B lymphoid committed progenitors. By contrast, all myeloid progenitors and LTC-initiating cells were found in the CD34+ CD10- CD19- cell fraction. This fraction appeared more heterogeneous and contained CD38- HLA-DRlow small cells, larger blasts, and promonocyte-like cells exhibiting small peroxidase-positive granules. Interestingly, CD10 was also present on CD34+ CD19- cells. This population mainly coexpressed CD33 and gave rise to macrophagic colonies.

The hierarchical level of stem cell involvement in acute promyelocytic leukemia (APL) characterized by the pathognomonic PML-RARA fusion gene is unknown. To determine if the cells of the primitive hematopoietic stem cell compartment are involved in the leukemic process, we have used molecular and cell sorting techniques in peripheral blood and bone marrow (BM) cells at diagnosis from three patients with APL and t(15; 17). In two of them, clonality analysis was also possible using the BstXI polymorphic site of the PGK gene. The PML-RARA fusion gene was readily identified by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of BM cells obtained at diagnosis in all three patients. These same samples were then used to sort CD34+ cells and their CD38+ and CD38-subsets by fluorescence-activated cell sorting. In both female patients, CD34+/CD38+ and CD34+/CD38- cell fractions were polyclonal using PCR, whereas a monoclonal pattern was identified at the BM sample obtained at diagnosis either by Southern blotting or by PCR. Because of the high sensitivity of the PCR analysis, the polyclonal pattern of these cell populations could mask the presence of a minor clone. To detect this clone, we preformed RT-PCR analysis for t(15; 17). In one female patient, the abnormal PML-RAR fusion gene was found only in the more mature CD34+/CD38+ cell fraction using a nested PCR approach, whereas the polyclonal CD34+/CD38- fraction was PML-RARA negative. These findings were confirmed in a third patient with APL in whom the PML-RARA transcripts were absent in the CD34+/CD38- cell fraction. To study the clonality at the level of clonogenic progenitors, we used in one patient PGK analysis by PCR of individual burst-forming units-erythroid and colony-forming units-granulocyte- macrophage obtained from the CD34+/CD38- and CD34+/CD38+ cell populations at diagnosis and from the BM sample obtained during remission. The two highly purified cell populations gave rise to morphologically normal colonies clonal for both the BstXI site containing (A) and the BstXI site lacking (B) PGK allelles, indicating their polyclonal content, a pattern that was also found in clonogenic progenitors obtained at remission. These findings strongly suggest that the primitive hematopoietic stem cells as defined by the CD34+/CD38- antigens are not involved by the neoplastic process in APL. These results may have important implications for autografting strategies of retinoic acid/chemotherapy-resistant or relapsed patients.

The tetrapeptide Acetyl-N-Ser-Asp-Lys-Pro (AcSDKP, Seraspenide; Ipsen- Biotech, Paris, France), an inhibitor of murine spleen colony-forming units reduces the number and the percentage in DNA synthesis of progenitors from human unfractionated bone marrow. To determine whether AcSDKP may directly affect the growth potential of purified progenitors even at the most primitive level, CD34+HLA-DRhigh and CD34++HLA-DRlow cells were highly purified by cell sorting. Then, CD34+ subsets were stimulated in liquid culture with combinations of growth factors (GFs) and AcSDKP was added for 20 hours or 6 days and cells plated in methylcellulose. After a 20-hour incubation, we show that AcSDKP (at 10(-10) mol/L) significantly inhibits the colony formation of both CD34+ subsets. Moreover, when added daily for 6 days, AcSDKP: (1) reduces the proliferation of both CD34+ cell fractions stimulated by 3 or 7 GFs, and (2) decreases the number of progenitors generated from the CD34+HLA-DRhigh and CD34++HLA-DRlow cell fractions. Furthermore, we show for the first time, using both high proliferative potential cell and long-term culture initiating cell assays, that AcSDKP inhibits the most primitive cells contained in the CD34++HLA-DRlow subpopulation. Finally, by using limiting dilution assays we demonstrated that AcSDKP acts directly at a single cell level and that its inhibitory effect is reversible and dose dependent.

Human CD34+ selected cells are able to reconstitute hematopoiesis in patients receiving a myeloablative treatment. Although the role of reinfused tumor cells contaminating the grafts on the determination of postautograft relapses remains unclear, the major interest of CD34+ cell selection is to reduce the tumor contamination of the graft. This can be achieved if tumor cells do not express the CD34 antigen. We previously showed that this approach was effective with bone marrow (BM) collections in patients with non-Hodgkin's lymphoma (NHL). Because peripheral blood progenitor cells (PBPC) allow faster hematologic recovery than BM and are expected to contain less tumor contamination, we have compared the results of CD34+ cell selection in 35 BM and 16 PBPC from 48 patients with NHL. The PBPC were collected after a course of chemotherapy followed by granulocyte colony-stimulating factor (G-CSF ) administration. The data showed that the final CD34+ cell purity achieved with PBPC was higher than with BM (medians, 70% v 50%; P = .02). The CD34+ cell recovery was also better for PBPC (medians, 42% v 24%; P = .001). Tumor contamination was assessed by detection of BCL2/JH rearrangement using polymerase chain reaction (PCR) in 38 of 48 patients (22 BM, 16 PBPC). In addition, immunoglobulin heavy chain gene (IgH) rearrangements were investigated using PCR with consensus IgH primers. At harvesting, 10 of 22 BM and two of 16 PBPC contained BCL2/JH+ cells, one of 22 BM and 14 of 16 PBPC contained abnormal IgH+ cells (one PBPC contained both BCL2/JH+ and abnormal IgH+ cells) at harvesting. However, because lymphoma tissue specimens from patients at diagnosis were not available, the malignant character of IgH rearrangements could not be confirmed by sequencing and probing with allele-specific nucleotides. After CD34+ cell selection, a reduction to below the level of detection of BCL2/JH+ cells of BM and PBPC was effective in seven of 12 informative selections. In contrast, a reduction to below the level of detection of abnormal IgH+ cells was effective in only three of 15 informative selections. However, the detection of cells with an abnormal IgH pattern in the context of chemotherapy plus G-CSF progenitor mobilization in patients with NHL and its correlation with actual tumor contamination needs further investigation.