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To study the mechanism(s) underlying the proliferation of heterogeneous cell populations within a solid tumour, the NBT-II rat bladder carcinoma system was used. It has been first investigated whether the different cell populations are coupled through gap junctions (GJIC). Cells overexpressing the Cx43 were generated to test for any tumour suppressive activity in vivo. To determine whether GJIC is essential for tumour proliferation and the establishment of a cooperative community effect, NBT-II cells that are incompetent for cell coupling were generated. The data report that (i) carcinoma cells expressing or not FGF-1 are coupled through GJIC in vitro and in coculture and express the gap junction protein Cx43, (ii) overexpression of Cx43 in these cells does not affect their in vitro coupling capacities and in vivo tumourigenic growth properties, (iii) inhibition of GJIC through antisense strategy has no in vivo obvious consequence on the tumour growth properties of the carcinoma, and (iv) the community effect between two carcinoma cell populations does not critically involve cell coupling through gap junctions. [Copyright &y& Elsevier]

Provides information on a study which examined the bystander effect on anti-tumoral suicide gene therapy. Mechanisms proposed to explain such a phenomenon; What mediates the gap-junctional communicaton; How to increase gap junctional intercellular communication.

We evaluated the gain in long-term survival of BDIX rats bearing DHDProB colon cancer developed in the peritoneal cavity after in vivo therapy with the tk gene and GCV. The sensitivity and the bystander effect of DHDProB cells stably transduced with the tk gene evaluated in vitro were low, as one tk+ cell killed two tk- cells. This correlated with the low ability of a fluorescent dye to diffuse through gap junctions. In vivo, more than 75% of tk-transduced cells were required and at least 100 mg/kg/day of GCV had to be injected no later than day 5 after tumor implantation to obtain a curative effect. A partial protection of the cured animals against rechallenge with the parental cells was also observed. Based on these results, a protocol of in vivo gene therapy was designed in which the tk/GCV treatment was combined with IL-2 gene expression. When the tk- and IL-2 encoding plasmids were injected twice i.p. with DOTAP and the animals treated with GCV, three of five rats were cured. This antitumoral activity resulted from the combined toxic effects of DNA/DOTAP and tk/GCV plus a potential immune response mediated by IL-2. [ABSTRACT FROM AUTHOR]

Introduction Le sévoflurane inhalé, administré via le dispositif Anaconda (ACD, Sebac © ), permet une sédation stable, bien tolérée et rapidement réversible en réanimation [1] . À la phase initiale de prise en charge des patients traumatisés crâniens, une sédation par sévoflurane pourrait permettre une évaluation neurologique clinique précoce. Cependant, les halogénés, du fait de leurs propriétés vasodilatatrices, pourraient augmenter le débit sanguin cérébral et donc la pression intracrânienne (PIC) [2] . Il n’existe aucune donnée clinique chez les patients traumatisés crâniens. Le but de ce travail est donc de déterminer l’effet d’une sédation par sévoflurane sur la pression intracrânienne chez des patients traumatisés crâniens. Matériel et méthodes Cette étude a l’accord du CPP Paris-Hôtel Dieu (protocole P100206). Après obtention du consentement d’un proche, les patients de plus de 18 ans admis en réanimation avec un traumatisme crânien sévère (Glasgow ≤ 8), après stabilisation de la PIC sont sédatés par sévoflurane administré par l’ACD en fonction du BIS pendant 12 h. Le sévoflurane est arrêté en cas d’augmentation de la PIC > 30 mmHg pendant plus de 15 minutes, et le traitement par sévoflurane est considéré comme un échec. Il s’agit d’une étude en ouvert, monocentrique en en 2 étapes (Design optimal de Simson) : une 1 re étape consiste à inclure 6 patients. L’étude sera arrêtée et le traitement sera considéré comme non acceptable si le nombre d’échec est supérieur à 2. La 2 e étape est la poursuite de l’étude jusqu’à 27 patients. Le traitement est considéré comme non acceptable si le nombre de succès est inférieur ou égal à 22. Si 5 patients sont en échec avant la fin de l’étude celle-ci sera arrêtée. Les critères secondaires sont la tolérance hémodynamique systémique (PAM : Pression artérielle moyenne) et cérébrale (IP : Index de pulsatilité au Doppler transcrânien) ( Tableau 1 et Fig. 1 ). Résultats Les résultats sont exprimés en médiane (min-max). Dix patients ont été inclus pour l’instant : 1 femme et 9 hommes, âgés de 40 ans (21–52), avec un IGS 2 à 48 (24–62). Le Glasgow initial médian était de 5 (3–8), avec une PIC à la pose de 16 mmHg (1–40). Le délai par rapport au jour du traumatisme crânien est de 7 jours (2–18). Aucun échec n’a été observé. Discussion Les résultats préliminaires de cette étude pilote sont encourageants quant à la faisabilité d’une sédation par sévoflurane chez les patients traumatisés crâniens. Deux augmentations isolées et transitoires de PIC ont été observées, correspondant à des soins (mobilisation et aspiration trachéale). Aucune augmentation durable de PIC n’a été constatée, et la tolérance hémodynamique et cérébrale semble bonne. [ABSTRACT FROM AUTHOR]

Objectives: Connexins (Cx) are proteins that form the gap junctional channels at neighbouring plasma membranes between adjacent cells. Cxs are involved in cell communication, which is reportedly correlated with cell proliferation and differentiation. Alterations in connexin expression and/or gap junctional intercellular communication (GJIC) capacity have long been postulated to be important in a number of pathological conditions including cancer. This study was performed to determine the consequences of the deletion of a single allele of Gja1 (Cx43 gene) in Alveolar Type II cells (APTIIs), and its impact on GJIC and cell proliferation. Material and methods: In order to do so, APTIIs from wild type (Cx43+/+) and heterozygous (Cx43+/–) mice were harvested and cultured for 4 days. The GJIC capacity was evaluated by scrape-loading method, with the transfer of lucifer yellow dye. The expression of Cx43 was evaluated by immunofluorescence method and Western blotting. Cell proliferation was evaluated by 3-(4,5-dimethylthazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Results: It was observed that GJIC capacity was significantly reduced and cell proliferation index was significantly higher in Cx43+/– cells compared to Cx43+/+ cells. Conclusions: These results show that knocking out one allele of Cx43 leads to a lower cell to cell communication capacity, and consequently induces a higher cell proliferation. Because chemically induced lung adenomas in mice are known to originate from APTIIs, these alterations may play a critical role in their susceptibility to lung carcinogenesis. [ABSTRACT FROM AUTHOR]

In tumors, gap junctional intercellular communication (GJIC) is usually down-regulated and the expression of connexins, membrane proteins constituting gap junction channels, is often low or altered. GJIC, allowing the intercellular diffusion of ganciclovir (GCV) triphosphate, is also one mediator of the ‘bystander effect’, the phenomenon by which herpes simplex virus thymidine kinase (HSVtk)-transduced, neoplastic cells kill surrounding HSVtk-negative cells when treated with GCV. We set up experiments to evaluate the effects of retrovirus-mediated in vivo gene transfer of connexin 43 in malignancies with low GJIC capacity. We found that U-87 human glioblastoma cells transfected in vitro by the human Cx43 cDNA grow signifi- cantly more slowly than control U-87 cells and lose their tumorigenicity when injected subcutaneously in nude mice. When the Cx43 gene was transduced in vitro in U-87 cells by a retroviral producer cell line (N3.2.ii, titer 1.5 × 106 c.f.u./ml) in vivo results were similar. However, only when U-87 cells were co-injected with N3.2.ii cells in nude mice in a 1:5 ratio, a 50% reduction in tumor size was obtained during the first 3 weeks. Moreover the co-injection of U-87 cells with N3.2.ii and SBA cells (a retroviral producer cell line expressing the HSVtk gene), was not able to potentiate the effects of GCV administration, suggesting that Cx43 gene transfer requires more efficient vectors to increase the bystander effect in vivo. [ABSTRACT FROM AUTHOR]

Gene therapy via the herpes simplex virus thymidine kinase (tk) gene and ganciclovir (GCV) treatment eliminates experimental tumors. In this approach, cells expressing the tk gene (tk+) and neighboring tumor cells which do not express the gene are killed. We have demonstrated this bystander effect is enhanced in vitro by gap junctional intercellular communication (GJIC). In order to extend our in vitro results into in vivo situations, we injected into nude mice different ratios of tk+/tk- HeLa cells, either lacking or transfected with connexin43 (Cx43), a gene coding for a gap junction protein. When GCV was administered before tumors were palpable, fewer animals developed tumors, even after a longer period, if the injected cells were mixtures of Cx43+-tk+ and Cx43+-tk- while tumor growth was not prevented with mixtures of HeLa cells not expressing Cx43, ie Cx43--tk+/Cx43--tk-. When GCV was given after the appearance of tumors, the size of the tumors from Cx43- cells was 30% reduced for 3 weeks if 50% of the injected cells were tk+. However, for cells expressing Cx43, the tumor size was 66% reduced if 10% of the cells were tk+. Such a reduction demonstrates a long-term bystander effect which is dependent on Cx43 expression. [ABSTRACT FROM AUTHOR]