5-fluorouracil permits access to a primitive subpopulation of peripheral blood stem cells

Peripheral Blood Stem Cell Transplantation: Critical Review

Autologous blood stem cell transplantations have been increasingly performed worldwide for almost ten years in place of autologous bone marrow transplantation and even of allogenic bone marrow transplantation. Several crucial issues were the subjects of impassioned controversies. Some of them are now satisfactorily answered while others still remain unresolved. First, it is now possible to conclude today that peripheral blood stem cells (PBSC) are undoubtedly capable of restoring short term hematopoiesis when reinfused after myeloablative therapy as well and even more rapidly than bone marrow stem cells, provided that they have been previously collected in sufficient amounts. On the opposite, it is still impossible to firmly prove that their very immature CD34+ cell subset, although in vitro functionally and phenotypically almost identical to their marrow counterpart, is actually responsible for sustained long term hematopoietic recovery, even if it is likely that these cells play a key role.

Most of the time, using chemotherapy alone or a combination of chemotherapy and cytokine(s), mobilizing regimens allow collection of appropriate yields of PBSC with only a small number of apheresis cycles, provided that a sufficient number of residual stem cells remains to be stimulated, when, on the contrary, collection in steady-state is time-consuming and does not provide further accelerated post transplant hematopoietic recovery.

It was initially hypothesized that PBSC could have a lower likelihood of tumoral contamination compared with bone marrow. In fact, biological as well as clinical data are discordant and probably depend largely on the type of disease, its evolutive history and its way of dissemination. Furthermore, the respective impact on the development of further relapse of graft contamination and of residual tumor cells into patient remains to be determined.

Finally, although it has often been claimed that the cost of mobilization, collection and cryopreservation of PBSC would be much higher than the cost of bone marrow harvesting, it is now possible to assert that the whole ABSCT procedure, including this preliminary phase, as well as the post-transplant period, allows an indisputable saving compared with ABMT.

These advantages are already sufficient reasons “per se” to propose ABSCT in place of ABMT or alloBMT in many indications even if their clinical benefit, in terms of disease-outcome, remains to be prospectively explored.

Molecular and phenotypic characterization of CD133 and SSEA4 enriched very small embryonic-like stem cells in human cord blood

Very small embryonic-like stem cells (VSELs) are immature primitive cells residing in adult and fetal tissues. This study describes enrichment strategy and molecular and phenotypic characterization of human cord blood VSELs. Flow cytometry analysis revealed that a majority of VSELs (LIN(-)/CD45(-)/CD34(+)) were present in the red blood cell (RBC) pellet after Ficoll-Hypaque centrifugation in contrast to the hematopoietic stem cells (LIN(-)/CD45(+)/CD34(+)) in the interphase layer. Thus, after lyses of RBCs, VSELs were enriched using CD133 and SSEA4 antibodies. These enriched cells were small in size (4-6 μm), spherical, exhibited telomerase activity and expressed pluripotent stem cell (OCT4A, OCT4, SSEA4, NANOG, SOX2, REX1), primordial germ cell (STELLA, FRAGILIS) as well as primitive hematopoietic (CD133, CD34) markers at protein and transcript levels. Heterogeneity was noted among VSELs based on subtle differences in expression of various markers studied. DNA analysis and cell cycle studies revealed that a majority of enriched VSELs were diploid, non-apoptotic and in G0/G1 phase, reflecting their quiescent state. VSELs also survived 5-fluorouracil treatment in vitro and treated cells entered into cell cycle. This study provides further support for the existence of pluripotent, diploid and relatively quiescent VSELs in cord blood and suggests further exploration of the subpopulations among them.

Effect of 5-FU and MTX on the Expression of Drug-resistance Related Cancer Stem Cell Markers in Non-small Cell Lung Cancer Cells

Cancer stem cells (CSCs) are often characterized by the elevated expression of drug-resistance related stem-cell surface markers, such as CD133 and ABCG2. Recently, we reported that CSCs have a high level of expression of the IL-6 receptor (IL-6R). The purpose of this study was to investigate the effect of anticancer drugs on the expression of the drug resistance-related cancer stem cell markers, ABCG2, IL-6R, and CD133 in non-small cell lung cancer (NSCLC) cell lines. A549, H460, and H23 NSCLC cell lines were treated with the anticancer drugs 5-fluorouracil (5-FU; 25 µg/ml) and methotrexate (MTX; 50 µg/ml), and the expression of putative CSC markers was analyzed by fluorescent activated cell sorter (FACS) and the gene expression level of abcg2, il-6r and cd133 by reverse transcriptasepolymerase chain reaction (RT-PCR). We found that the fraction of ABCG2-positive(+) cells was significantly increased by treatment with both 5-FU and MTX in NSCLC cells, and the elevation of abcg2, il-6r and cd133 expressions in response to these drugs was also confirmed using RT-PCR. Also, the number of IL-6R(+) cells was increased by MTX in the 3 cell lines mentioned and increased by 5-FU in the H460 cell line. The number of CD133(+) cells was also significantly increased by both 5-FU and MTX treatment in all of the cell lines tested. These results indicate that 5-FU and MTX considerably enhance the expression of drug-resistance related CSC markers in NSCLC cell lines. Thus, we suggest that antimetabolite cancer drugs, such as 5-FU and MTX, can lead to the propagation of CSCs through altering the expression of CSC markers.

Multilevel Regulation of IL-6R by IL-6-sIL-6R Fusion Protein According to the Primitiveness of Peripheral Blood-Derived CD133+Cells

Interleukin-6 (IL-6) and its soluble receptor (sIL-6R) are major factors for maintenance and expansion of hematopoietic stem cells (HSCs). Sensitivity of HSCs to IL-6 has been previously studied, in part by measuring the expression of IL-6R on the membrane (mIL-6R). Several studies have described the regulation of cell surface expression of IL-6R by several cytokines, but the role of glycoprotein 130 activation has not yet been investigated. In this study, CD133(+) cells were purified from adult peripheral blood and were precultured in the absence or presence of 5-fluorouracil (5-FU) for selection of quiescent HSCs. Cells were cultured with continuous or pulsed stimulations of an IL-6-sIL-6R fusion protein (hyperinterleukin-6 [HIL-6]) to 1) detect mIL-6R by flow cytometry, 2) assess mIL-6R and sIL-6R RNAs by reverse transcription-polymerase chain reaction, 3) measure sIL-6R in supernatants by enzyme-linked immunosorbent assay, 4) analyze cell-cycle status, and 5) perform long-term culture-initiating cell assays. The level of mIL-6R(-) cells was preserved by 5-FU incubation. HIL-6 increased steady-state mIL-6R RNA and expression rate on HSCs, independently of treatment with 5-FU. Enhanced production of sIL-6R was observed with short pulses of HIL-6 on CD133(+) 5-FU-pretreated cells. This overproduction of sIL-6R was abrogated by tumor necrosis factor-alpha protease inhibitor-1, an inhibitor of a disintegrin and metalloprotease proteases, suggesting the shedding of mIL-6R. This phenomenon was mediated through the phosphatidylinositol-3'-kinase pathway and was involved in the maintenance of primitive HSCs. In conclusion, expression and production of IL-6R are tightly regulated and stage specific. We assume that sIL-6R produced by shedding should be involved in autocrine and paracrine loops in the HSC microenvironment.

Recruitment of primitive peripheral blood cells: synergism of interleukin 12 with interleukin 6 and stromal cell-derived FACTOR-1

In bone marrow, haematopoietic stem cells (HSC) rely on close contact with stromal cells for proliferation and differentiation. Stromal cell-derived factor (SDF-1) is a chemokine produced by bone marrow stromal cells and has been reported to be a chemoattractant for CD34(+)cells. SDF-1 was evaluated for effects on proliferation of both mature and immature human progenitor cells in vitro. Neither proliferation nor maturation of peripheral blood cells was stimulated by SDF-1 alone. Moreover, we have previously demonstrated that 5-fluorouracile (5-FU) resistant HSC require a combination of interleukin 12 (IL-12), IL-6 and SCF for the production of morphologically recognizable clonogenic elements at day 14 in semisolid medium. Our data reported a strong enhancement of the IL-6, IL-12, SCF-induced synergism (172%) by SDF-1 (296.5%). Furthermore, our data suggest that this chemokine alone had no effect on triggering quiescent cells and may preserve these cells from 5-FU cell damage or upregulate early-acting cytokine receptors. Thus, SDF-1 might play a key role in early human haematopoiesis through its potent synergistic effects in combination with early-acting cytokines. These results suggest that a programmed response to sequential cytokine stimulation may be part of a control mechanism required for maintenance of proliferation of primitive HSC.

Human umbilical cord blood myeloid progenitor cells are relatively chemoresistant: a potential model for autologous transplantations in HIV-infected newborns

Vertical transmission from mother to child occurs in 15-39% of women infected with the human immunodeficiency virus (HIV). Stem cell transplantation has recently been suggested as a potential therapy for patients with HIV infection. We have examined the possible advantages of human cord blood (HUCB) stem cells over bone marrow (BM) stem cells in the treatment of HIV-infected newborns. HUCB myeloid progenitors were found to be statistically more resistant to interferon-alpha (IFN-alpha), cytarabine (ARA-C), and eilatin than BM myeloid progenitor cells grown with IL-3 (P < 0.05). HUCB treated with IFN-alpha, ARA-C, and eilatin demonstrated a significantly higher capacity for self-renewal manifested by delta assay following 7 days in liquid culture. We, therefore, suggest that HUCB purged by anti-HIV drugs may be a source for autologous transplantation in HIV-infected newborns.

Expansion of blood CD34+ cells: committed precursor expansion does not affect immature hematopoietic progenitors

The CD34 antigen is present at all differentiation stages of hematopoietic cells, from immature progenitor cells to committed precursor cells. In vivo, transplantation of CD34+ cells is sufficient to allow hematopoietic recovery after myeloablative chemotherapy, but a neutropenic period of 9-12 days still exists, even when hematopoietic growth factors are given posttransplantation. After ex vivo expansion cultures in the presence of cytokines, CD34+ cells can generate mature precursor cells in a stroma-free liquid culture system. This could lead to a shortening of the aplasia duration, but the persistence of primitive progenitor cells in the expanded CD34+ compartment remains to be demonstrated. In this study, CD34+ cells were isolated from eight peripheral blood (PB) and eight cord blood (CB) samples using either Isolex 50 (n = 6), Ceprate LC CD34 kit (n = 6), or Microcellector T-25 Stem Cell kit (n = 4). We have evaluated the functional potential of CD34+ cells after 7 days of ex vivo expansion culture in the presence of 500 UI/ml of interleukin-1 (IL-1), 10 ng/ml of IL-3, and 10 ng/ml of stem cell factor (SCF). The expansions of nucleated cells, granulocyte-macrophage colony-stimulating factor (GM-CSF)-responsive committed precursors, IL-1 + IL-3 + SCF + erythropoietin (EPO)-responsive multilineage progenitors, and 5-fluorouracil (5-FU)-resistant quiescent progenitor were 8-fold, 59-fold, 4.4-fold, and 2.2-fold, respectively. There was no significant difference in the amplification/expansion parameters between cultures initiated with CD34+ cells from PBSC or CB. Our data confirm that cytokine-mediated ex vivo expansion of blood CD34+ cells can produce large numbers of committed precursors and does not significantly affect the compartment containing more immature progenitors. Cytokine-mediated expansion could be of great interest in autologous transplantation to decrease the duration of marrow aplasia.

Transplantation of allogeneic peripheral blood stem cells mobilized by recombinant human granulocyte colony stimulating factor

Recombinant G-CSF has been given to over 150 normal donors for the collection of allogeneic or syngeneic peripheral blood stem cells (PBSC). G-CSF was found to be well-tolerated with mild-moderate bone pain, edema and mild thrombocytopenia being the observed side effects. To date, approximately 90 unmodified primary PBSC transplants from HLA-identical related donors have been performed with engraftment that is, in general, considerably more rapid than marrow. Acute graft-versus-host-disease (GVHD), grades II-IV occurred in 47% of patients and grades III-IV in 17%. Despite the infusion of one to two logs more T cells, these results are not remarkably different than would be expected with marrow transplantation. There have also been successful reports of using G-CSF mobilized allogeneic PBSC following second transplants for graft rejection or relapse. Allogeneic PBSC have been infused without reconditioning for correction of graft failure and unmodified or CD34 selected PBSC have also been given with marrow to augment the dose of hematopoietic cells. Further studies are needed to define the role of allogeneic PBSC for transplantation, refine PBSC mobilization and collection techniques and to evaluate the long-term effects of cytokines in normal donors.

Transplantation of allogeneic peripheral blood stem cells

Recombinant G-CSF has been given to over 150 normal donors for the collection of allogeneic or syngeneic peripheral blood stem cells (PBSCs). G-CSF was found to be well-tolerated with mild-moderate bone pain, edema and mild thrombocytopenia being the observed side effects. To date, approximately 100 unmodified primary PBSC transplants from HLA-identical related donors have been performed with engraftment that is, in general, considerably more rapid than marrow. Acute graft-versus-host-disease (GVHD) grades II-IV occurred in 44% of patients and grades III-IV in 16%. From a small number of evaluable patients surviving for more than 100 days, it appears the incidence of chronic GVHD is approximately 50%. Despite the infusion of one to two logs more T cells, these results are not remarkably different than would be expected with marrow transplantation. Further studies are needed to define the role of allogeneic PBSCs for transplantation, to refine PBSC mobilization and collection techniques, and to evaluate the long-term effects of cytokines in normal donors.

[Congenital erythropoietic porphyria. Apropos of a fatal case in the neonatal period due to acute hemolysis with hepatic failure]

BACKGROUND

Congenital erythropoietic porphyria, an autosomal recessive disease, is characterized by deficiency of uroporphyrinogen III synthase. Clinical variability of the disease is related to the different mutations found in the patients.

CASE REPORT

A newborn suffered one hour after birth from jaundice and polypnea with acute hemolysis. Severe cutaneous photosensitivity occurred after phototherapy. Congenital erythropoietic porphyria was suspected because of reddish-colored urine and confirmed by porphyrin analyses. The baby died one month later due to severe hemolytic anemia with hepatic failure. Uroporphyrinogen III synthase activity was decreased by 99% in bone marrow cells and established lymphoblastoid cells from the patient. Molecular biology studies demonstrated the presence of the Cys 73-->Arg substitution at the homozygous state in the patient.

CONCLUSION

This mutation, the most frequently found in this disease, is responsible for a severe phenotype. Molecular characterization provides genotype/phenotype correlations in this porphyria and allows to clarify unusual cases of porphyrias.

Correction of the enzyme defect in cultured congenital erythropoietic porphyria disease cells by retrovirus-mediated gene transfer

Congenital erythropoietic porphyria (CEP) is a genetic disease characterized by an overproduction and accumulation of porphyrins in bone marrow. The enzyme defect concerns uroporphyrinogen III synthase (UROIIIS), the fourth enzyme of the heme biosynthetic pathway. It is the most severe porphyria and the treatment is largely symptomatic: gene therapy would represent a great therapeutic improvement. As a step toward the development of an effective gene therapy, we have constructed two retroviral vectors, LUSN and pMFG-US (with and without the selectable marker Neo), containing a full-length human cDNA for UROIIIS. Recombinant retroviruses were obtained by transfection of the LUSN or pMFG-US plasmid into the amphotropic packaging cell line psi CRIP. For each construct, three different producing clones were selected for their high titer (LUSN) or for their ability to express the message at a high level (pMFG-US). In vitro amplification of genomic DNA from target tissue demonstrated the presence of vector sequences. Murine fibroblasts infected in vitro expressed the human enzyme efficiently, as indicated by RNA and enzymatic studies. Retroviral-mediated gene transfer was then used to introduce the UROIIIS cDNA into human deficient cells. Enzyme activity was increased from 2% (deficient fibroblasts) to 121-274% of the normal value for the different clones. Transduced cells selected with G418 presented an 18-fold increase in enzyme activity compared to the normal cells. Furthermore, high gene transfer rate into peripheral blood progenitor cells (PBPB) was documented by in vitro amplification (PCR). These results demonstrate the potential usefulness of somatic gene therapy for the treatment of CEP.

Cytokine-mediated expansion of 5-FU resistant peripheral blood stem cells and bone marrow: self-renewal and commitment capacity

To further characterize the primitive stem cell subpopulation present in chemotherapy mobilized peripheral blood stem cells (PBSC), we evaluated the functional characteristics of 5-FU-resistant PBSC and normal bone marrow (BM) cells after 7 days incubation with IL-1 + IL-3+SCF. The resulting 5-FU-resistant cells were evaluated for (1) the production of GM-CSF-responsive clonogenic elements (CE), (2) the production of IL-3+GM-CSF-responsive CE, and (3) their self-renewal capacity (production of IL-1+IL-3+SCF-responsive CE). We also evaluated the percentage of CD34+ cells, the percentage of cells in S phase of the cell cycle, and the number of nucleated cells before and after cytokine-mediated expansion. We demonstrated an overall loss in nucleated cells after cytokine-mediated expansion in all cell fractions. We demonstrated a significantly greater increase in the percentage of CD34+ cells in the 5-FU-resistant PBSC fraction as compared to 5-FU-resistant BM cells (p = 0.012). We also showed that 5-FU-resistant PBSC have a greater capacity for self-renewal, amplification of IL-3+GM-CSF-responsive progenitors, and the production of committed GM-CSF-responsive progenitors as compared with BM cells, but this did not reach statistical significant. These results suggest that PBSC contain a truly primitive stem cell with an enhanced self-renewal and differentiative capacity that is recruited by 5-FU resistance and IL-1+IL-3+CSF-mediated expansion.(ABSTRACT TRUNCATED AT 250 WORDS)