CTF/NF1 transcription factors act as potent genetic insulators for integrating gene transfer vectors.

Gene transfer-based therapeutic approaches have greatly benefited from the ability of some viral vectors to efficiently integrate within the cell genome and ensure persistent transmission of newly acquired transgenes to the target cell progeny. However, integration of provirus has been associated with epigenetic repercussions that may influence the expression of both the transgene and cellular genes close to vector integration loci. The exploitation of genetic insulator elements may overcome both issues through their ability to act as barriers that limit transgene silencing and/or as enhancer-blockers preventing the activation of endogenous genes by the vector enhancer. We established quantitative plasmid-based assay systems to screen enhancer-blocker and barrier genetic elements. Short synthetic insulators that bind to nuclear factor-I protein family transcription factors were identified to exert both enhancer-blocker and barrier functions, and were compared to binding sites for the insulator protein CTCF (CCCTC-binding factor). Gamma-retroviral vectors enclosing these insulator elements were produced at titers similar to their non-insulated counterparts and proved to be less genotoxic in an in vitro immortalization assay, yielding lower activation of Evi1 oncogene expression and reduced clonal expansion of bone marrow cells.

Relevance of an academic GMP Pan-European vector infra-structure (PEVI).

In the past 5 years, European investigators have played a major role in the development of clinical gene therapy. The provision of substantial funds by some individual member states to construct GMP facilities makes it an opportune time to network available gene therapy GMP facilities at an EU level. The integrated coordination of GMP production facilities and human skills for advanced gene and genetically-modified (GM) cell therapy, can dramatically enhance academic-led "First-in-man" gene therapy trials. Once proof of efficacy is gathered, technology can be transferred to the private sector which will take over further development taking advantage of knowledge and know-how. Complex technical challenges require existing production facilities to adapt to emerging technologies in a coordinated manner. These include a mandatory requirement for the highest quality of production translating gene-transfer technologies with pharmaceutical-grade GMP processes to the clinic. A consensus has emerged on the directions and priorities to adopt, applying to advanced technologies with improved efficacy and safety profiles, in particular AAV, lentivirus-based and oncolytic vectors. Translating cutting-edge research into "First-in-man" trials require that pre-normative research is conducted which aims to develop standard assays, processes and candidate reference materials. This research will help harmonise practices and quality in the production of GMP vector lots and GM-cells. In gathering critical expertise in Europe and establish conditions for interoperability, the PEVI infrastructure will contribute to the demands of the advanced therapy medicinal products* regulation and to both health and quality of life of EU-citizens.

Human skin keratinocytes modified by a Friend-derived retroviral vector: a functional approach.

The goal of this study was to test the efficiency and possible functional effects of a Friend Leukemia derived retrovirus vector (FOCH29-NeoR) on cultured human keratinocytes, obtained from skin biopsy samples. The keratinocytes were grown and infected with filtered Friend vector supernatant. After one or two doses of infection, one duplicate of the culture was submitted to selection with G418; the other one was utilized for DNA extraction and PCR modification detection. Transduction efficiency was 46.66 percent and 47.22 percent for one and two doses of infection respectively (range 100 to 15 %). Colony Forming Efficiency (CFE) assays were done with Rodhamine-B staining in nonselected modified cultures and negative controls. There was no difference in CFE (% CFE= 10.74+/-6.53 negative control vs % CFE= 9.22+/-5.45 with one dose, and % CFE= 10.03+/-5.74 with two doses of infection). Nevertheless, the cell-cycle analysis done by Propidium Iodade (PI) incorporation and colchicine-arrest assays in nonselected transduced and nontransduced cells show that transduced keratinocytes have a longer time to enter G2. As far as we know, this is the first report of retroviral transduction-induced changes in the cell cycle done on human keratinocytes. This observation is very important because retroviral vectors of genes, such as platelet derived growth factor (PDGF) or vascular endothelial growth factor (VEGF), are expected to facilitate the implementation of these modified cultures for tissue grafting and skin substitute development and potentiate the effectiveness of the grafts.

In vivo retroviral mediated gene transfer into bladder urothelium results in preferential transduction of tumoral cells.

OBJECTIVES: Superficial bladder tumours are at high risk for recurrence, relapse after resection, escape to intravesical immunotherapy and they may become invasive. New therapeutics are therefore needed to achieve cure. Thus, gene therapy is an attractive new treatment modality for malignant bladder tumours. The purpose of this study was to evaluate the feasibility and the efficiency of retroviral mediated reporter gene transfer into malignant urothelial cells both in vitro and in vivo. METHODS: We evaluated the feasibility of the transfection of bladder tumour with direct intravesical instillation of a defective retrovirus. The vector was derived from LXSN. The efficiency of transduction with the Moloney Leukaemia Murine virus-based vector, amphotrophic retroviral vector, was monitored through the expression of two marker genes (nls-LacZ and NeoR). The canine animal was chosen since it can present with spontaneous bladder carcinomas mimicking human pathology. Primary cultures of two normal canine bladder urothelium and two canine primary bladder tumours were first studied. We then investigated in vivo, in two normal and two spontaneous tumour bearing dogs, the transduction of urothelial cells following direct intravesical instillation of 2.10(4) to 3.10(6) of the retroviral vector. RESULTS: Transduced cells were evidenced in all primary cultures of canine normal urothelium and transitional cell carcinoma. Bladder biopsies from sound dogs instilled with the viral solution showed long lasting transduction up to 60 days long. Bladder cryosections from tumour-bearing dogs displayed transduction of superficial layers of urothelial cancer cells without passing through lamina propria. In vivo transduction was evidenced in 1 to 15% (mean 5%) of the cells in the tumours and preferentially addressed malignant cells. Normal epithelium either originating from sound or tumour-bearing animals was not transduced. CONCLUSION: These results demonstrate for the first time the feasibility of in vivo retroviral transduction of bladder cancer using a clinically relevant procedure.

[Li-Fraumeni syndrome: update, new data and guidelines for clinical management]. / Le syndrome de Li-Fraumeni: mise au point, données nouvelles et recommandations pour la prise en charge.

The Li-Fraumeni syndrome (LFS) is an inherited form of cancer, affecting children and young adults, and characterized by a wide spectrum of tumors, including soft-tissue and bone sarcomas, brain tumours, adenocortical tumours and premenopausal breast cancers. In most of the families, LFS results from germline mutations of the tumor suppressor TP53 gene encoding a transcriptional factor able to regulate cell cycle and apoptosis when DNA damage occurs. Recently, germline mutations of hCHK2 encoding a kinase, regulating cell cycle via Cdc25C and TP53, were identified in affected families. The LFS working group recommendations are the following: (i) positive testing (screening for a germline TP53 mutation in a patient with a tumor) can be offered both to children and adults in the context of genetic counseling associated to psychological support, to confirm the diagnosis of LFS on a molecular basis. This will allow to offer to the patient a regular clinical review in order to avoid a delay to the diagnosis of another tumor; (ii) the 3 indications for positive testing are: a proband with a tumor belonging to the narrow LFS spectrum and developed before age 36 and, at least, first- or second-degree relative with a LFS spectrum tumor, before age 46, or a patient with multiple primary tumors, 2 of which belonging to the narrow LFS spectrum, the first being developed before 36 or a child with an adenocortical tumour; (iii) presymptomatic testing must be restricted to adults; (iv) the young age of onset of the LFS tumors the prognosis of some tumors, the impossibility to ensure an efficient early detection and the risk for mutation carriers to develop multiple primary tumors justify that prenatal diagnosis might be considered in affected families.

Efficient transduction of hemopoietic CD34+ progenitors of human origin using an original retroviral vector derived from Fr-MuLV-FB29: in vitro assessment.

A novel retroviral vector has been designed based on a Friend-murine leukemia virus (Fr-MuLV) FB29 strain. The latter has been selected according to characteristics of pathogenicity in mice where it induces a disease of the haemopoietic system affecting all lineages. Higher infectivity has also been demonstrated as compared to other strains. In accordance with these findings, the amphotropic producer clone used in this study carrying along the neomycine resistance gene (FOCH-Neo), harbors viral titers over 10(7) cfu/ml. To investigate the potential of genetically engineering hematopoietic precursors, CD34+ progenitors were selected from cord blood, bone marrow, and peripheral blood mobilized stem cells (patients + solid tumors) and transduced with FOCH-Neo. High transduction rates were achieved using virus supernatant and minimal doses of hematopoietic growth factors during pretransduction and transduction steps. A polymerase chain reaction (PCR) assay investigating the presence of both neomycin-encoding and viral vector sequences tested positive in 45-90% of granulocyte-macrophage colony-forming units (CFU-GM) generating cells (bone marrow and peripheral blood derived cells) following transduction. An average of 35% colonies showed resistance to G418. Such levels of transduction proved reproducible using only supernatants harboring over 10(7) cfu/ml. In those experiments where long-term in vitro cultures could be maintained over 5 weeks (all cord blood and 5 among 23 PBSC), efficient transduction of long-term culture initiating cell (LTC-IC) hematopoietic progenitors was demonstrated on the basis of both resistance to G418 and virus integration. In the latter case, the PCR assay tested positive in as much as 35-60% of late unselected CFU-colonies. This novel retroviral vector harbors interesting features toward genetic modification of hematopoietic progenitors.

A review of current basic approaches to gene therapy.

Over the past decade methods for delivering genes into mammalian cells aimed at subsequent expression of the transferred sequences from the host cell have been developed. Potential therapeutic applications have been envisaged and have raised great interest. Though procedures based on gene targeting will not enter clinical protocols prior to the solving of fundamental issues, procedures based on gene addition are currently underway. The expected benefit of genetic modification of somatic cells needs to be carefully assessed and confronted to its potential risks. Whatever the technological strategy, non-propagation and non-transmission of the gene transfer delivery system is mandatory. Preclinical studies covering a large range of pathologies are currently underway; primarily aimed at demonstrating rather the technological feasibility of various approaches than true therapeutic efficacy. Technological improvements and the solving of basic issues dealing with both the regulation of gene expression and the biology of cell transplantation are still required in order for gene therapy to enter a phase of clinical efficacy. Pluri-disciplinarity only will allow for fruitful exchanges between investigators in the basic sciences and therapists. This has been the basis for creating a European Working group on human Gene Transfer and therapy (EWGT). Whatever the interest raised by gene therapy and its innovatory potential, the relevance of this approach should carefully be considered 1st) in terms of economical constraints and ethics; 2nd) in the context of an overall therapeutic strategy, in particular in the case of acquired disease like cancer, and confronted to alternative treatments such as targeted drugs.

Detection of quantitative polymerase chain reaction products by hybridization on magnetic support with 125I-radiolabeled probes: quantification of c-myc copy numbers.

We present a technique for determining c-myc copy numbers that can be used as a prognosis index for some cancers. The method is based on the use of both competitive polymerase chain reaction and hybridization of amplified products. Coamplification was performed directly on cells with a synthetic oligonucleotide used as internal standard. It recognized the same primer set as the target. Coamplified products were captured on streptavidin magnetic beads as solid support using a 5' biotinylated primer. DNA immobilized on this support was denatured with alkali. Each coamplified product (target and reference gene) was further hybridized to two distinct specific oligonucleotide probes. Gene amplification levels were determined using a standard curve obtained by serial dilutions of peripheral blood lymphocytes run along with the experimental samples. This approach provides a rapid (less than 2 days) and reproducible method for evaluating c-myc gene copy number and may be used to quantify any gene. Moreover, its format allows for automation.

[Gallium-67 scintigraphy in malignant lymphoma]. / Apport de la scintigraphie au gallium-67 dans les lymphomas malins.

The presence of a residual mass is a frequent and difficult problem in the treatment of Hodgkin's or non-Hodgkin's lymphoma: since it is of major importance to determine whether the lesion is a fibrous mass or a still progressing tumour requiring additional therapy. Gallium-67 scanning, performed in a series of 52 patients, provides an answer to this question since there is an excellent correlation between gallium uptake by the tumoral masses and their progressiveness. Magnetic resonance imaging was carried out in half of our patients: the finding of a low-intensity signal on T2-weighted sequences proved that the residual mass was fibrous, whereas a high-intensity signal on T2-weighted sequences did not distinguish between fibrous and tumour masses. The priceless information provided by the simple and non invasive method that is gallium scanning is extremely useful to evaluate the extension of lymphomas and to determine whether residual masses are tumoral or fibrous.