Production of stem-cell transplants according to good manufacturing practice.

Peripheral blood stem cells (PBSCs) are used for transplantation to reconstitute the hematopoietic system after high-dose chemotherapy. They are harvested from peripheral blood after mobilization by cytokines and/or chemotherapy. Further ex vivo manipulation steps (e.g., selection of CD34+ PBSCs, purging, expansion, and differentiation or gene transfer) can be performed. In 1997, more than 12,000 PBSC preparations were transplanted in Europe and the total number is steadily increasing [1]. To ensure quality and safety of the final cell products intended for clinical use, national and international guidelines and regulations have been issued. The implementation of a quality assurance (QA) program including the principles of good manufacturing practice (GMP) and a quality control system is a major requirement. GMP regulations apply to all phases of cell collection, processing, and storage, and to documentation, training of personnel, and equipment of the cell processing laboratory. They have to be followed by pharmaceutical companies and medical doctors who are involved in PBSC processing at academic institutions. The complicated regulatory network for the manufacturing of cell products will help to standardize these procedures and ensure consistent quality and safety in the long term. This will be in the interest of patients and reduce risks of application of individual cell preparations.

Pro-inflammatory and T cell inhibitory cytokines are secreted at high levels in tumor cell cultures of human renal cell carcinoma.

OBJECTIVES: The objectives of this study were to assess cytokine secretion in human renal cell carcinoma (RCC) and to identify cytokines contributing to the immunomodulatory effect of tumor cells. METHODS: Cytokine secretion in the supernatant of primary tumor cell cultures (PTCC) and corresponding cell lines (CL) was assayed using ELISA. Tumor cells were characterized by morphology, immunocytochemistry, and flow-cytometric analysis. Tumor-cell-induced T cell activation was determined by coculture of gamma delta and alpha beta T cell clones with tumor CL. RESULTS: We assessed the cytokine secretion of tumor cells from 27 PTCC and their corresponding CL (3/27) of RCC. We found that RCC predominantly produced both pro-inflammatory and T-cell-inhibitory cytokines, such as IL-8, IL-6, GM-CSF, TNF-alpha, IL-10 and TGF-beta 1. CL were adapted to serum-free medium which may prove as a useful tool in future studies of cytokine secretion in RCC. In addition, we used gamma delta and alpha beta T cell clones to assess the immunomodulatory effect of tumor cells from RCC and found that predominantly gamma delta T cells were activated by RCC. CONCLUSIONS: Our data suggest that RCC produce large amounts of both pro-inflammatory and T-cell-inhibitory cytokines that potentially could influence the immune response of the host, especially tumor-specific cytotoxic T cells.

[Continuous delivery of epidermal growth factor to wounds in vivo by genetically modified fibroblasts transfected with a novel chimeric construct].

OBJECTIVE: This paper aims to explore the new method of continuous delivery of epidermal growth factor to wounds by transfected fibroblasts to promote wound repair. METHODS: It was constructed a novel chimeric expression plasmid in which the biologically active portion of the human epidermal growth factor (EGF) gene was fused in-frame to the human granulocyte colony-stimulating factor signal sequence. RESULTS: Clonally selected human fibroblasts transfected with this construct could secrete biologically active EGF. After the transplantation of irradiated gene-transfected fibroblasts suspended in fibrin glue to murine full-thickness wounds, EGF could be demonstrated for at least seven days in the wounds, slowly decreasing from initially 470 ng/L to 140 ng/L in 7 days. No EGF was found in the wound at 14 days. CONCLUSION: A single application of irradiated EGF gene transfected fibroblasts to wounds can continuously deliver the transgene in vivo and can be used to administer drugs to the wound bed during the crucial first seven days of wound-healing.

Enhancement of a constitutively active promoter for gene therapy by a positive feed-back transcriptional activator mechanism.

Success of gene replacement therapy depends on long-term, high level expression of the transgene. Gene therapy vectors incorporating a promoter of a constitutively active eukaryotic gene may allow long-term expression in vivo, but the expression level may be insufficient for therapeutic effects. To enhance transcription from eukaryotic promoters, a strategy with dicistronic vectors encoding the therapeutic gene of interest together with a transcription factor that binds and activates the promoter was tested. Expression vectors for the chimeric tet repressor/VP16 transcription factor (tTA) driven by the human beta-actin promoter were constructed, and tandem tet operators were inserted within the promoter. This arrangement significantly enhanced expression of G-CSF in fibroblasts to higher levels than the immediate/early CMV promoter. Stably transfected fibroblast clones produced up to 2.4 microg G-CSF per 10(6) cells x 24 h. After injection of genetically engineered cells into SCID mice, the enhanced beta-actin promoter construct resulted in marked leukocytosis, whereas the unmodified promoter had only a marginal therapeutic effect. Transcription factor-enhanced, feed-back-activated human promoters may thus achieve higher expression levels than viral control elements, and may be advantageous for gene therapy due to high constitutive activity in vivo.

Tumor-infiltrating lymphocytes exhibiting high ex vivo cytolytic activity fail to prevent murine melanoma tumor growth in vivo.

The identification of tumor-associated Ags recognized by CD8+ CTL and prevention of tumor outgrowth by adoptive transfer of these CTL demonstrates that CD8+ T cells play a major role in antitumor immunity. We have generated B16.F10 melanoma cells that express the glycoprotein epitope amino acid 33-41 (GP33) of the lymphocytic choriomeningitis virus (LCMV) to examine antitumor CD8+ T cell response in C57BL/6 mice immune to LCMV and in mice transgenic for the LCMV GP33-specific P14 TCR (P14 TCR mice). We find that B16.F10GP33 tumor cells grew in syngeneic C57BL/6 mice without inducing T cell tolerance. LCMV infection or adoptive transfer of LCMV-specific effector T cells delayed but did not prevent growth of preestablished tumors in these mice. However, B16.F10GP33 tumor cells were rejected in mice immune to LCMV and in mice treated with LCMV-specific effector T cells on the same day as the tumor. Surprisingly, B16.F10GP33 tumor cells grew in P14 TCR transgenic mice despite an abundance of tumor-associated Ag-specific CD8+ T cells. In these mice, freshly isolated tumor-infiltrating lymphocytes exhibited an activated phenotype and displayed high GP33-specific cytolytic activity when assessed ex vivo. Thus, B16.F10GP33 melanoma cells are able to initiate, but not to sustain, a GP33-specific CTL response sufficient to clear the tumor enduringly.

Lymphotoxin-alpha is an autocrine growth factor for chronic lymphocytic leukemia B cells.

Lymphotoxin-alpha (LT), also called TNF-beta, which belongs to the 'TNF family' was originally isolated from a lymphoblastoid cell line. LT enhances the proliferation of activated B cells and augments B cell proliferation induced by IL-2. It functions as an autocrine growth factor for EBV-infected B cell lines and has been implicated in the pathogenesis of B cell malignancies. We tested the expression of LT mRNA in B-CLL and found that LT was expressed in highly purified leukemic cells in 11 out of 11 patients examined. Regulation of expression of LT mRNA is aberrant in B-CLL cells, since LT mRNA expression was not detected in fresh peripheral blood mononuclear cells or B cells identified in seven out of seven normal individuals. In addition, LT mRNA expression was detected for up to 6 days in purified unstimulated in vitro cultures of B-CLL cells. Glucocorticosteroids, that have been effectively used in the treatment of lymphoid malignancies, were added to the cultures and abrogated the LT mRNA expression after an incubation time of 12 h. Addition of recombinant LT to cultures increased proliferation of B-CLL cells while proliferation of these cells was inhibited by antisense oligonucleotides against LT mRNA. B-CLL cells cultured with LT antisense oligonucleotides (asLT) as well as glucocorticoid-treated cells showed reduced viability and a DNA fragmentation ladder characteristic of apoptosis suggesting a relationship between down-regulation of LT mRNA expression and the induction of apoptosis. These studies support the role of LT in the growth regulation and development of B-CLL cells.

Cytokine gene transfer in cancer therapy.

New strategies based on gene transfer technology are employed in cancer therapy. Cytokines are polypeptides involved in immunity and inflammation, and essentially control the magnitude of the immune response. Genetically modified tumor cells releasing various cytokines have been shown to enhance tumor immunogenicity and to induce the regression of preexisting tumors. In some instances, immunological memory has been generated to resist the subsequent challenge with unmodified, parental tumor cells. Cytokine gene transfer into antitumor effector cells, as well as antigen presenting cells, is also being investigated to augment antitumor immune responses.

Cloning and sequence analysis of the immediate promoter region and cDNA of porcine granulocyte colony-stimulating factor.

Granulocyte colony-stimulating factor (G-CSF) is a cytokine that stimulates the proliferation and differentiation of hematopoietic progenitor cells committed to the neutrophil/granulocyte lineage. Recombinant G-CSF (rG-CSF) is routinely used in the prevention of chemotherapy-induced neutropenia and in the setting of bone marrow transplantation. Chronic idiopathic and congenital neutropenic disorders also show improvement after rG-CSF injections. Applications of either rG-CSF or G-CSF gene transfected cells into mice give rise to leukocytosis, which can be measured easily. This makes G-CSF a versatile tool for studying systemic effects of therapeutic proteins delivered by genetically modified cells in vivo. Although the biological activity of G-CSF is not species-specific, studies on long-term expression would require the use of species-identical proteins in order to avoid host immune reactions against the foreign gene product. Because of the physiological and immunological similarity of pigs and human, the pig has become an important large-animal model for biomedical research. We have therefore cloned porcine G-CSF cDNA from RNA isolated from pig PBLs. Pig G-CSF is a 195-amino-acid polypeptide that shares a high degree of homology to human (78%), murine (71%) as well as rat (68%) G-CSF. In contrast to human and murine, but not to rat G-CSF, a different ATG translation start codon is used, resulting in a shorter, but still functional signal sequence.

Comparison of cytogenetics, cytokine secretion, and oncogene expression in primary cultures of renal carcinoma cells.

We compared the cytogenetic pattern of 20 different primary tumor cell cultures (PTCC) of renal cell carcinoma (RCC) to their cytokine secretion and oncogene expression. High secretion of IL-6 (gene locus on chromosome 7p21-p14) was correlated with the gain of an additional chromosome 7. Structural changes involving chromosome 5q22, the site of the GM-CSF gene, were matched with the high secretion of GM-CSF in PTCC. No such association was found for beta 2-microglobulin, TGF-beta 1, TNF-alpha, IL-8, and oncogenes, such as c-fos, c-myc, and pan-ras. Our approach may be useful in simultaneously analyzing several factors contributing to tumor progression and may contribute to understanding the multistep development of RCC.

Paracrine stimulation of keratinocytes in vitro and continuous delivery of epidermal growth factor to wounds in vivo by genetically modified fibroblasts transfected with a novel chimeric construct.

BACKGROUND: Growth factors play an important role in tissue repair. While the effectiveness of growth factor therapy in animal wound healing models and limited human clinical trials has been demonstrated, the ideal method for their administration to the wound remains unclear. Experimental data suggest that the continuous presence in the early stages of wound repair is beneficial. MATERIALS AND METHODS: We have constructed a novel chimeric expression plasmid in which the biologically active portion of the human epidermal growth factor (EGF) gene is fused in-frame to the human granulocyte colony-stimulating factor signal sequence. RESULTS: Clonally selected human fibroblasts transfected with this construct secrete biologically active EGF. After the transplantation of irradiated gene-transfected fibroblasts suspended in fibrin glue to murine full-thickness wounds, EGF can be demonstrated for at least seven days in the wounds, slowly decreasing from initially 470 pg/ml to 140 pg/ml on day 7. No EGF was found in the wound at day 14. CONCLUSIONS: A single application of irradiated EGF genetransfected fibroblasts to wounds can thus continuously deliver the transgene in vivo and could be used to administer drugs to the wound bed during the crucial first seven days of wound-healing.

Induction of tumor-specific cytotoxic T lymphocytes by immunization with autologous tumor cells and interleukin-2 gene transfected fibroblasts.

In a phase I trial designed to study a vaccine composed of autologous tumor cells and interleukin-2 gene transfected fibroblasts we analyzed lymphocytes infiltrating the vaccination site (VIL) in two melanoma patients. Functional studies demonstrated that numbers of MHC class I restricted cytotoxic T cells directed against the autologous tumor had increased at the immunization site in both cases. Analysis of the variability of T cell receptors (TCR) in the VIL of one patient revealed that the cytotoxic T lymphocytes consisted of a predominant population of TCRBV21S3+ T cells. Enrichment of this subpopulation to more than 99% by specific anti-TCRBV21S3 monoclonal antibody linked immunomagnetic beads and sequencing of the TCR-beta chain disclosed exactly the same V-D-J junctional sequence in all eight TCRBV21 transcripts from these VIL. The identical sequence was also detected in all eight TCRBV21 transcripts from the patient's tumor-infiltrating lymphocytes, indicating that the same CTL clone had infiltrated the tumor, circulated in the peripheral blood, and was amplified at the vaccination site. The TCRBV21S3+ T cells were also found to display an MHC class I restricted cytotoxic activity specifically directed against the autologous tumor cells. At the beginning of treatment these cells were undetectable at the vaccination site and delayed-type hypersensitivity testing was negative, contrasting with the positive results after therapy. Thus it is likely that vaccination with autologous tumor cells plus interleukin-2 gene transfected allogeneic fibroblasts had induced not only local accumulation but also an increase in the frequency of circulating tumor specific CTL.

NTS influence on transgene expression from mono- and bicistronic plasmid vectors after lipofection in a human fibroblast cell line.

We evaluated the survival, transgene production, and copy numbers of integrated plasmid units per host genome after lipofection with mono- and bicistronic plasmid vectors in different cell lines and under various conditions. The addition of an integration enhancing murine sequence nontranscribed spacer (NTS) to the plasmids increased transfection efficiency, survival, and transgene expression. However, in human fibroblast cells this sequence had only marginal effects on overall plasmid copy number in bulk cultures. Clones producing the highest amounts of the transgene contained only one or two copies of plasmid per genome, independent of cell type and plasmid design.

A phase-I clinical study of autologous tumor cells plus interleukin-2-gene-transfected allogeneic fibroblasts as a vaccine in patients with cancer.

Tumor cells transfected to express immunostimulatory cytokines, or admixed with similarly modified bystander cells, are able to induce immune responses against unmodified tumor cells in animal models. For treatment of human patients, a vaccine composed of autologous tumor cells and IL-2-secreting allogeneic fibroblasts was developed. Autologous tumor cells were isolated from biopsy specimens. A clone (KMST 6.14) of an immortalized human fibroblast line that stably secreted 5290 IU IL-2 per 10(6) cells and per 24 hr was obtained by cationic lipofection with an expression construct for human IL-2 and Neo(r). Fifteen patients with refractory malignant tumors received 3-4 injections of irradiated KMST6.14 and autologous tumor cells in a phase-I clinical trial. Increasing transient inflammatory responses without systemic toxicity developed at vaccination sites and after injections with irradiated tumor cells only (p < 0.05). These sites contained a dense infiltrate of CD3+ T cells with numbers of CD4+ helper cells exceeding those of CD8+ cytotoxic T cells (CTL). CD8+ T-cell lines isolated from vaccination sites of 2 malignant melanoma patients but not of renal-cell carcinoma patients exhibited a dominant lytic activity against autologous tumor cells in vitro. CD8+ T-cell clones established from the vaccination site of 1 of 2 renal-cell carcinoma patients preferentially lysed autologous and partially matched allogeneic renal-cell carcinoma cells. In conclusion, a vaccine composed of IL-2 gene-transfected allogeneic fibroblasts and autologous tumor cells is able to enhance specific anti-tumor T-cell responses in vivo without major side-effects. Malignant melanoma and renal-cell carcinoma appear to be promising entities for testing of similar approaches in future therapeutic trials.

Processing of tumor tissues for vaccination with autologous tumor cells.

Vaccination with gene-transfected tumor cells has recently been proposed as a new strategy in the immunotherapy of cancer. Since autologous tumor cells provide an optimal antigen profile, the possibility of generating single cell suspensions from renal cell carcinoma (RCC), malignant melanoma (MM), colon carcinoma (CC), and non-small-cell lung cancer (NSCLC) biopsies was investigated. One hundred and seventy-four tumor biopsies were processed by mechanic and enzymatic dissociation, yielding 1-2 x 10(6) cells/g tumor (median), irrespective of tumor type. Primary tumor cell cultures (PTCC) of > or = 10(7) cells were established from 29 of 86 (34%) RCC, 14 of 38 (37%) MM, 11 of 23 (48%) NSCLC and 4 of 27 (15%) CC specimens. The amount of non-tumor cells, as assessed by morphology and immunocytology, was generally low (< 30%) in RCC (35 of 41) and MM (11 of 17), while it exceeded 60% in 8 of 11 PTCC from NSCLC and 3 of 11 CC. A high tumor cell yield was obtained in biopsies with a high degree of vascularization and in the virtual absence of necrosis. Thus, PTCC > or = 10(7) cells were obtained in 73% of MM with a high degree of vascularization and in 22% of MM with a low degree of vascularization (p < 0.007). Long-term tumor cell cultures exceeding 20 passages were established in 24 of 86 (18%) RCC, 7 of 38 (18%) MM and 3 of 27 (11%) CC, while successful implantation in nude mice was achieved in 8 of 20 RCC and 5 of 10 MM. Thus, under the conditions described, > or = 10(7) primary tumor cells of high purity could be generated from about one third of RCC and MM biopsies, while the success rate increased to > 50 and > 70%, respectively, in samples with a high degree of vascularization generated by an optimized biopsy technique excluding necrotic parts.

Systemic hematological effects of granulocyte colony-stimulating factor produced by irradiated gene-transfected fibroblasts.

Although long-term expression of therapeutic molecules is necessary for the treatment of permanent deficiencies, short-term expression of therapeutic molecules inducing local or systemic effects is preferable in clinical situations where temporary substitution is the goal. One such clinical setting is the administration of hematopoietic growth factors in cancer chemotherapy-induced myelosuppression. Several plasmid vectors containing the human granulocyte colony-stimulating factor (G-CSF) gene under transcriptional control of different regulatory elements were constructed. In vitro production of G-CSF by nonvirally transfected murine fibroblast clones initially increased after lethal irradiation and was detectable for at least 12 days. We also demonstrate that a single injection of irradiated G-CSF-secreting fibroblasts leads to accelerated hematopoietic recovery and mobilization of committed peripheral blood progenitor cells equivalent to that achieved by twice daily s.c. administration of high doses of recombinant human G-CSF. Using dicistronic vectors, high levels of G-CSF secretion were also obtained in human fibroblasts.

In vitro differentiation of CD34+ hematopoietic progenitor cells toward distinct dendritic cell subsets of the birbeck granule and MIIC-positive Langerhans cell and the interdigitating dendritic cell type.

We have demonstrated recently that Birbeck granule-positive Langerhans cells (LC) can be derived from CD34+ peripheral blood progenitor cells in the presence of a seven-cytokine cocktail (CC7-7). Here, we show that the sequential use of early-acting hematopoietic growth factors, stem cell factor, interleukin (IL)-3, and IL-6, followed on day 8 by differentiation in the two-factor combination IL-4 plus granulocytemacrophage colony-stimulating factor (GM-CSF) (CC4GM) is more efficient and allows the cells to be arrested in the LC stage for more than 1 week while continuous maturation occurs in CC7-7. Maturation of LC to interdigitating dendritic cells (DC) could specifically be induced within 60 hours by addition of tumor necrosis factor-alpha (20 ng/mL) or lipopolysaccharide (100 ng/mL). Using LC that had been enriched to greater than 90% CD1a+ cells by an immunoaffinity column, we were able to define clear-cut differences between LC and DC that corroborate data of the respective cells derived from epithelial borders (LC) or from lymph nodes (LN) and spleen (DC). Thus, molecules and functions involved in antigen (AG) uptake and processing were highly expressed in LC, while those involved in AG presentation were at maximum in DC. LC were CD1a+2 DR+2, CD23+, CD36+, CD80-, CD86-, and CD25-, while DC were CD1a+/- DR+3, CD23-, CD36-, CD80+, CD86+2, and CD25+, CD40 and CD32 were moderately expressed and nearly unchanged on maturation, in contrast to monocyte-derived DC. Macropinocytosis of fluorescein isothiocyanate-dextran was dominant in LC, as were multilamellar major histocompatibility complex (MHC) class II compartments (MIICs), which were detected by electron microscopy. The functional dichotomy of these cell types was finally supported by testing the AG-presenting cell function for tetanus toxoid to primed autologous T-cell lines, which was optimal when cells were loaded with AG as LC and subsequently induced to become DC.

Systematic evaluation of chimeric marker genes on dicistronic transcription units for regulated expression of transgenes in vitro and in vivo.

Plasmid expression vectors combining human cytokine cDNAs and selectable marker genes on dicistronic transcription units were functionally characterized in vitro and in vivo. The internal ribosome entry sequence (IRES) of encephalomyocarditis virus mediated cap-independent translation of the downstream cistron. After cationic lipofection of cells with a dicistronic construct containing the Neor gene downstream of a human interleukin-2 (IL-2) cDNA, all G418-resistant clones secreted high amounts of IL-2. Reversal of the order of the cDNAs was associated with less efficient transgene expression and represented no advantage in comparison to separate expression cassettes. To combine direct in vitro selection of expression with in vivo elimination of cytokine-secreting cells, an improved chimeric cDNA of the Neor and herpes simplex virus (HSV) thymidine kinase (TK) genes was constructed and shown to confer sensitivity to ganciclovir concentrations that can be achieved in human patients. This chimeric marker was coupled on dicistronic constructs with a granulocyte colony-stimulating factor (G-CSF) cDNA as a molecule with easily detectable bioactivity in vivo. Subcutaneous implantation of pCMV.GCSF.ires TK/NEO-transfected CMS-5 cells into syngeneic BALB/c mice resulted in excessive leukocytosis and progressively growing tumors. Treatment with ganciclovir led to normalization of leukocyte counts in all animals, whereas complete regression of tumors was observed in only 3/5 mice. Hypermethylation of the transfected promoter was demonstrated in both ganciclovir-resistant tumors. Thus, transcription units combining selectable markers and genes of interest allow selection of high producer cells in vitro and efficient elimination of transgene-expressing cells in vivo. However, cells that hypermethylate transfected genes to terminate gene expression in vivo may escape conditional ablation.

Delineation of the dendritic cell lineage by generating large numbers of Birbeck granule-positive Langerhans cells from human peripheral blood progenitor cells in vitro.

It is well established by in vivo and in vitro studies that dendritic cells (DCs) originate from hematopoietic progenitor cells. However, the presumed intermediate of Birbeck granule (BG)+ Langerhans cells (LCs) has not been detected in cultures derived from bone marrow or peripheral blood progenitor cells (PBPCs), thus contrasting with the data obtained with cord blood. We show here that large numbers of BG+ LCs can be generated from human CD34+ PBPCs in vitro, when granulocyte-macrophage colony-stimulating factor and interleukin-4, potent promotors of LC/DC differentiation, are combined with a cocktail of early acting hematopoietic growth factors. LCs were found to emerge from CD33+CD11b+CD14- progenitor cells that they share with the monocytic lineage. During culture, these cells exhibited a sequence of dramatic morphologic changes, starting with a major increase in granularity followed by an increase in size herein exceeding that of all peripheral blood cells. At the same time, CD1a and major histocompatibility complex class II expression were upregulated and virtually all CD1a++ cells were BG+ by electron microscopy. With prolonged culture, CD1a was downregulated on a major population of cells, paralleled by a loss of BG and an increase of CD4, CD25, and CD80 expression that may correspond to the maturation of epidermal LC in vitro. However, these cells were consistently CD5- and did not exhibit changes in the CD45-isoform expression during culture. The availability of large numbers of these highly purified BG+ LCs and mature DCs allows for specific analysis of these subpopulations and provides a source of potent antigen-presenting cells from individual patients for vaccination protocols against infectious or tumor-associated antigens.

The nomenclature of chemokines.

Migration of leukocytes to injured tissues is a hallmark of inflammation. The recruitment phase of cells can be subdivided into three steps: the rolling phase, the firm adhesion phase, and the transendothelial migration phase. Each step is mediated by a complex interplay of endothelial/leukocyte surface molecule interactions (mostly of selectin and integrin families) as well as a group of small, secreted peptides, called chemokines. Chemokines activate on the one hand, the leukocytes to express the appropriate adhesion molecules and on the other hand, they lead to transendothelial migration via chemotaxis (migration along a gradient in solution) and haptotaxis (migration along a gradient bound to extracellular martrices or cell membranes). The structure, biology and pathobiology of the more than 22 known members of this group of soluble mediators, with a particular emphasis on their past and present nomenclature, is the topic of this minireview.