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Protéine NS1 du parvovirus H-1 et induction de la mort cellulaire dans des cellules humaines normales et transformées

Abstract : H-1 parvovirus (H-1PV) exerts several anticancer properties. It preferentially replicates within human transformed cells (oncotropism). This could lead to cell destruction (oncolysis) and to release of progeny viral particles that could thus infect and destroy nearby transformed cells. These in vitro properties could be extended to in vivo situations. Indeed, H-1PV protects laboratory animals from tumor development (oncosuppression). For instance, H-1PV prevents the onset of induced tumors establishment in infected animals and can induce tumor growth stop or even tumor regression. All these properties enlighten the rising interest in the use of H 1PV as an alternative to current antimitotic treatments. Though, putative use of this virus for human cancer therapy requires a deeper understanding of its mode of action. Our aim was to determine whether H-1PV could offer a satisfying solution to two of the most worrying aspects of current anticancer therapeutics. The specificity of current anticancer drugs is somewhat limited, often leading to the induction of side effects in normal cells. H-1PV generally is non-toxic in human non-transformed cells. This is due to the lack of activation of parvoviral P4 promoter, which controls production of viral NS1 protein, the main effector in H-1PV induced cytotoxicity. Our aim was to investigate the putative consequences of NS1 overexpression within cells insensitive to H-1PV infection. To this attempt, we used a model in which NS1 was ectopically expressed in human normal embryonary cells with limited life span, MRC-5 cells. Our work show that CMV-driven NS1 protein overexpression in these cells results in actin filaments alterations and cell death, both effects being prevented by serine 473 mutation. The same substitution preserves actin filaments of transfected MRC-5 SV2 cells, MRC-5 transformed counterparts, but does not impair NS1-induced cytotoxicity. Another big issue with current therapeutics is cell resistance to treatment. Recent data have shown that H-1PV is efficient in inducing cell lysis in some brain and pancreatic tumors resistant to classical anticancer approaches. We investigated whether H-1PV infection could induce cell death in SK-BR-7, a human breast cancer cell line with high metastatic potential. SK-BR-7 cells are constitutively resistant to apoptosis by means of an autocrine system that inhibits apoptosis induction. Our results indicate that H-1PV infection of these cells leads to death while being inefficient in inducing the caspase 3 activation predicted by the model. We nevertheless were not able to determine which pathway(s) is (are) involved in H-1PV-induced SK-BR-7 cell death. Indeed, it appeared that the non-commercial component we used failed to exert its expected autocrine system inhibition. As this component is critical for model robustness, and as production of new doses by our collaborators in Lyon was severely delayed, we were not able to firmly address conclusions about this project. Data acquired thanks to these two ongoing projects raise interesting questions. It would be interesting to use the NS1 expression tools we constructed to investigate effects of NS1 overexpression on a broader range of normal human cells. We also would like to decipher the molecular pathways leading to human normal cell death. Moreover, as soon as the autocrine system inhibitor is available again, we plan to use it in order to precisely analyze which pathways are involved in H-1PV-induced SK-BR-7 cell death. It would notably be interesting to see whether H-1PV is able to interfere with the autocrine-related apoptosis inhibition. Altogether, our results will be of interest when considering the use of H-1PV for human anticancer therapy.
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https://tel.archives-ouvertes.fr/tel-00499417
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Submitted on : Friday, July 9, 2010 - 2:37:43 PM
Last modification on : Monday, October 19, 2020 - 11:11:46 AM
Long-term archiving on: : Monday, October 11, 2010 - 9:37:54 AM

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Pierre Wizla. Protéine NS1 du parvovirus H-1 et induction de la mort cellulaire dans des cellules humaines normales et transformées. Biologie cellulaire. Université du Droit et de la Santé - Lille II, 2010. Français. ⟨tel-00499417⟩

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