All medical doctors are concerned by the medical scientific, ethical, economic and reglementary aspects of cells transplantation. However, hematopoietic stem cells are the most used cells in transplantation in case of leukemia, and solid tumor. Other human or animal cells are used to graft burned patients, patients with severe liver failure, knee traumatism and other exceptional disease. Autologous expanded keratinocytes, chondrocytes, hepatocytes are sometime transplanted. Most cellular products are processed before being transplanted. These processes, more or less complicated, use physical, immunological and functional characteristics of the cells. Most cellular products are processed by non profit organisms as said by the "94 bioethic law".

When allogeneic stem cells transplantations are still considered as high risk therapies concerning few people, at present autologous stem cells transplantations take place in many therapeutic protocols of many malignant diseases even if clinical evaluation is not always really performed. Challenges in a close future consist in the decrease of the incidence of complications (of the immunological type essentially) of allogenic transplants without reducing the "graft versus leukemia effect", and the decrease of the risk of relapses after autologous transplantations.

Despite important initial chemosensitivity, advanced ovarian cancer has a bad prognosis with a median survival of 20 to 30 months. These results might be better with intensive chemotherapy. We analysed 67 patients treated by intensive chemotherapy with autologous stem cell transplantation for advanced ovarian cancer at Institute Paoli-Calmettes between 1980 and 1994. Population was divided in two groups: salvage group (n = 30) for initial chemotherapy-refractory patients and consolidation group (n = 37) for sensitive patients. Several successive conditioning regimens were used, all based on alkylating agents. Principal toxicities were severe aplasia and mucositis. Four patients died from toxicity related to infection during strong immunosuppression. In salvage group, 9 out of 21 evaluable patients responded (43%), but duration of responses was short (median range of 5 months) and 2-year overall survival rate was 8% after transplantation. In consolidation group, 19 patients are alive and 15 are without disease progression with a median follow-up of 42 months (17, 161) after diagnosis. Five-year disease-free survival rate is 28% (median range of 35 months) and 5-year overall survival rate is 48% (median range of 41 months). Intensification does not seem to be long term beneficial for initial chemotherapy refractory patients, despite objective responses rate better than classical treatment. On the other hand, results seem better than conventional treatments in case of chemosensitive disease and should be confirmed prospectively in larger cohort of patients. Moreover, other research directions are open like intensification supported by hematopoietic growth-factors and peripheral stem cells, definition of best conditioning regimen, use of taxanes, and intensification in first line chemotherapy after initial surgery.

Few genes have a proven role in the pathogenesis of myelodysplastic syndromes (MDS). The most common abnormalities involve the RAS genes, most notably the N-RAS gene, and are present in 10% of cases at diagnosis and in 30% to 40% during the course of the disease. Mutations of the p53 are found in 5% to 10% of cases. Mutations of the cFMS genes are less common, abnormalities of the NF1 genes seem to occur only in children, and abnormalities of the RB genes are exceedingly rare. A few instances of t(5;12) or t(3;21) translocation have been demonstrated, and their study has provided evidence that the TEL, EVI1, MDS1, and AML1 genes are involved in some cases of MDS. The presence in MDS of recurrent chromosome 7, 5q, and 20q deletions suggests that these chromosomal segments may bear tumor suppressor genes involved in MDS. The gene(s) involved remain(s) to be identified. Clonality studies have shown that stem cell involvement usually occurs at the myeloid level and that normal multipotent stem cells persist in many patients with MDS. This opens up the promising possibility that transplantation of autologous multipotent stem cells may be an effective therapeutic approach.

Like all new and emerging technologies, cell therapy has raised many hopes for the treatment of some severe diseases. However, its development needs first a clear ethical and legal framework. Because of the complexity and cost of these therapies, development has to be focused on fields where clinical benefits appear greater and where therapeutic alternatives are limited. Since 28 May, 1996 France has had a law (No. 96-452) which defines the 'biological products for therapeutic use' and therefore cell therapy. Many different therapeutic domains are concerned, depending on cell type. The level of development already reached and the number of patients concerned are quite variable. The grafting of hematopoietic stem cells and of expanded keratinocytes, which concerns in France 2500 and 100 patients per year respectively, are well characterized. The clinical trial of dendritic cells for vaccination is just starting but could represent a very large field of application with more than 10,000 patients per year. The grafting of hepatocytes, and the production of antiviral CTL and encapsulated cells (Langerhans islets of allo- or xenogenic origin), nerve cells, and myocytes are still at an early stage of development. Whatever the field, before entering clinical trials, a clear scientific and medical rationale must exist. The efficacy and security of the proposed treatment should be established on relevant models. Cell processing protocols must be well characterized and reproducibility proven with quality controls in place and the cell processing facilities approved by the relevant authorities. Partnership with industry could take many different forms. It should speed up development by providing access to reagents, growth factor of clinical grade, devices, cell processing technologies, etc., without preventing investigators from conducting their trial as planned.

Correct regulation of spermatogonial mitosis and, more specifically, the control of the balance between differentiation and proliferation to allow renewal of the stem cell stock, are essential for the maintenance of spermatozoa production throughout life. The mechanisms underlying this control are still unknown. However, recent studies suggest that some locally produced cytokines may be involved in the regulation of spermatogonial activity. In this context, Leukemia Inhibitory Factor (LIF) exhibits interesting properties regarding stem cells and, particularly, primordial germ cells. The present study aimed at investigating LIF production and LIF binding abilities by/of the different testicular cells types (somatic and germ cells). Our study demonstrates that LIF is produced within the testis, mainly by peritubular cells which are in the vicinity of spermatogonia, the latter cells expressing high levels of LIF receptors. These results strongly suggest an involvement of LIF in the control of spermatogonial activity.

The best regimen for mobilizing hematopoietic stem cells (HSC) into peripheral blood is not yet defined. The efficiency of FEC chemotherapy in the treatment of breast cancer is well established and the effects of FEC on HSC mobilization have been characterized. We tested the feasibility and the toxicity of a high-dose FEC regimen which may improve the mobilizing capacity of conventional FEC. Twenty patients with poor prognosis breast cancer received high-dose FEC and filgrastim 5 micrograms/kg. Three leukaphereses were performed on each patient for 3 consecutive days. Total numbers of CFU-GM and CD34+ cells were assessed, and a retrospective analysis was made. The numbers of CFU-GM/kg and CD34+ cells/kg collected (mean +/- standard error) were respectively 12.2 x 10(5) (+/- 2.4) and 14.6 x 10(6) (+/- 2.5). Extra-hematologic toxicity was negligible. Hematologic recovery after CTCb high-dose chemotherapy and HSC infusion was rapid. High-dose FEC is efficient for collecting HSC in peripheral blood. Extra-hematologic toxicity is weak and hematologic recovery after autograft is normal. Increased dosage of epirubicin and cyclophosphamide could allow a single leukapheresis collection of sufficient HSC from peripheral blood.

Since the introduction of melphalan, little progress has be obtained in the treatment of multiple myeloma. Complete remission is rarely achieved with classical single-drug or combined chemotherapy protocols: median survival remains low at 2 to 3 years. A NEW APPROACH: High-dose melphalan therapy with hemopoietic stem cell support it a new approach providing promising results. There is a dose effect and 70 to 80% of naive patients, at the cost of severe prolonged aplasia, respond to high-dose melphalan. HEMATOPOIETIC SUPPORT: Allogeneic or autologous bone marrow or blood stem cell grafts are used. Peripheral blood autographs can be used in most patients; contamination with tumoural cells is generally lower. The period of aplasia after chemotherapy and hematopoietic autograft is relatively short. MAIN INDICATIONS: For most authors, high-dose melphalan should be reserved for younger patients with active myeloma: complete remission is achieved in 20 to 30% of cases although relapse still occurs. Other techniques under study (several sequences of high-dose sessions, reduction of graft contamination) should help improve results.

Cutaneous B cell lymphomas, especially when appearing as a monomelic papulonodular eruption, are rare.

Bone marrow is a tissue with a high mitotic activity, and consequently exquisitely radiosensitive. The clinical effects of bone marrow irradiation and its ability of regeneration are related to the volume irradiated. Management of hematopoietic side effects of radiation include surveillance, antibiotics, blood products transfusion, and more scarcely hematopoietic growth factors, bone marrow transplantation and peripheral blood stem cells reinfusion.

The early steps of cellular radiation response have been investigated using a linear electron accelerator operated in a split-dose mode, in such a way that the time intervals between pulse exposures to relativistic electrons ranged from fractions of a second to a few minutes. The initial dose brought about large, synchronous changes in radiation sensitivity and generated a tetraphasic, W-shaped time-dependent profile of cell survival upon the second radiation exposure. While this time-related process was observed in most cell lines investigated, its kinetic parameters varied significantly from one cell line to the other. The number of DNA strand breaks (neutral and alkaline DNA filter elution) and the level of apoptosis (gel electrophoresis and flow cytometry) induced at the different phases of the time-dependent profile showed no relationship with the W-effect. It is presently hypothesized that mechanisms involved in molecular recognition of radio-induced lesions and initiation of genomic instability play a major role in this effect. Whatever the mechanism involved, the split-dose irradiation in the range of seconds enables dissecting the early steps of radiation response. The relevance of the W-effect to radiation therapy and technical drawbacks are discussed.

The authors analyze the role of G-CSF and GM-CSF in hematological malignancies. These allow correction of drug-induced neutropenias and perhaps more importantly allow the increase of doses of chemotherapy to improve the antitumor effect, and permit the maintenance of full chemotherapy doses in elderly patients. They can also mobilize peripheral blood stem cells for autologous and recent allogeneic transplantation. They can be useful at low doses in correcting the spontaneous neutropenia of bone marrow failures. A specific antitumor effect, on the other hand, is extremely hypothetical. Erythropoietin by contrast has been disappointing in the treatment of anemia in spontaneous bone marrow failures. For the treatment of thrombocytopenias, preliminary results with thrombopoietin are encouraging. Combinations of growth factors will probably improve results obtained with one factor. However, in all cases the cost/benefit of growth factors will have to be strictly established.

Haematopoietic growth factors are glycosylated proteins involved in the differentiation of pluripotent stem cells into committed progenitor cells, which eventually give rise to distinct haematopoietic cell lineages. Three recombinant hematopoietic growth factors--G-CSF, GM-CSF and erythropoietin--are currently commercially available for clinical use. G-CSF and GM-CSF are lineage-specific growth factor that regulate the production and function of granulocytic and monocytic cells. They have been shown to reduce the incidence of febrile neutropenia. Primary prophylactic administration is reserved for patients in which the expected incidence of febrile neutropenia is greater than 40% without haematopoietic growth factor. After a documented occurrence of febrile neutropenia in an earlier cycle, the secondary prophylactic administration of G-CSF or GM-CSF may be considered. However, in the absence of clinical data supporting maintenance of chemotherapy dose-intensity, dose reduction should be considered as an alternative to the use of haematopoietic growth factors. G-CSF and GM-CSF also shorten the period of neutropenia in patients undergoing high-dose chemotherapy with autologous bone marrow support. Erythropoietin is currently approved for treatment of anemia associated with cisplatin-based chemotherapy with the aim to reduce transfusion requirements.

While effectively preventing graft-versus-host disease (GVHD), ex vivo T-lymphocyte depletion of the graft unfortunately increases graft rejection and reduces the graft-versus-leukemia (GVL) effect after allogeneic hematopoietic stem cell transplantation. The ex vivo transfer of the herpes-simplex thymidine-kinase (HS-tk) suicide gene into T-cells before their infusion with the hematopoietic stem cells, should allow for selective in vivo depletion of these T-cells with ganciclovir (GCV), if subsequent GVHD was to occur. We have demonstrated that retroviral-mediated transfer of HS-tk and Neomycine resistance genes in T-lymphocytes, followed by G418 selection, results in T-cells specifically inhibited by GCV with no bystander effect. In a phase I study, escalating amounts of HS-tk expressing T-cells are infused in conjunction with a T-cell depleted marrow graft to allogeneic HLA identical recipients. Toxicity, survival alloreactivity and GCV-sensitivity of the gene-modified cells are monitored.

The gene encoding the CD2 mouse cell surface antigen was retrovirally transduced into cord blood CD34+ cells. On infection by culture at the contact of retrovirus-packaging cells, the mCD2 marker was expressed by 30-40% CD34+ cells, that included the most primitive stem cell-enriched Thy-1+ and CD38- subsets. Accordingly, sorted cord blood CD34+Thy-1+ cells could be directly infected in the same conditions. mCD2- transgenic cord blood CD34+ cells were then used to reconstitute human fetal thymus implanted in SCID mice. Five to 8 weeks later, the mCD2 antigen was detected on approximately 10% of the human thymocytes repopulating the thymus grafts and the transgene genome was detected in graft cell DNA by Southern blot. These results demonstrate efficient gene transfer into primitive cord blood hematopoietic cells endowed with lymphoid potential and suggest gene therapy schemes in neonates suffering inherited or acquired-such as HIV infection-disorders of the T-cell lineage.

CEP is a rare disease inherited as an autosomal recessive trait and characterized by an overproduction and accumulation of porphyrins in the bone-marrow. Because the predominant site of metabolic expression of the disease is the erythropoietic system, bone marrow transplantation represents a curative treatment for patients with severe phenotypes. This treatment can be considered in severe cases when the disease appears in the first few years of life. When bone marrow transplantation is not possible, gene therapy by transplantation of genetically modified hematopoietic cells is an attractive alternative for the future. In this report, we present the restoration of enzymatic activity and the metabolic correction of deficient cells in vitro after transduction with retroviral vectors. The future availability of a mouse model of the disease will permit ex vivo gene therapy experiments on the entire animal.