gms | German Medical Science

27th German Cancer Congress Berlin 2006

German Cancer Society (Frankfurt/M.)

22. - 26.03.2006, Berlin

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Cell death is not effected by the apoptosis enhancer Daxx in drug and CD95-mediated apoptosis in renal cell carcinoma

Meeting Abstract

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  • corresponding author presenting/speaker Csaba Mahotka - Universitätsklinikum, Düsseldorf, Deutschland
  • Nils Wethkamp - Universitätsklinikum, Düsseldorf
  • Petra Reinecke - Universitätsklinikum, Düsseldorf
  • Helmut E. Gabbert - Universitätsklinikum, Düsseldorf

27. Deutscher Krebskongress. Berlin, 22.-26.03.2006. Düsseldorf, Köln: German Medical Science; 2006. DocPO511

The electronic version of this article is the complete one and can be found online at: http://www.egms.de/en/meetings/dkk2006/06dkk621.shtml

Published: March 20, 2006

© 2006 Mahotka et al.
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Outline

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Introduction: Deregulation of apoptosis is involved in the development of cancer. Expression of Daxx is implicated in apoptosis but whether its function is pro- or anti-apoptotic is still discussed controversial. Daxx is involved in the regulation of p53 dependent transcription and associates with the promyelocytic leukemia protein (PML) in speckled subnuclear structures so called PML oncogenic domains (PODs). Overexpression-based experiments in renal cell carcinoma (RCC) were used to explore the impact of Daxx on the CD95-dependent apoptosis and cell death induced by different anticancer agents such as Etoposide, Topotecan, Taxol® and Doxorubicine.

Methods: Retrovirus-based transduction of GFP/GFP-Daxx expression constructs and generation of stably expressing RCC cell lines, MTT-Assay, Western Blot and in vitro kinase assay.

Results:1. Constitutive overexpression of Daxx in the CD95-ligand sensitive human RCC cell line clearCa-6 (clear-Ca-6/GFP-Daxx) has no influence on cell growth. 2. Treatment of clearCa-6/GFP-Daxx with the CD95-receptor agonistic antibody CH11 leads to no further enhancement of the CD95-dependent apoptosis compared to control cell line clear-Ca-6/GFP as analyzed by MTT Assay and Caspase-8 and PARP Western Blot, respectively. 3. Daxx overexpression in the CD95-ligand resistent RCC cell line clearCa-2 (clearCa-2/GFP-Daxx) also causes no sensitization to the CD95-dependent apoptosis. 4. Although Daxx is known to trigger CD95-mediated apoptosis via the activation of JNK by a Caspase-8 independent mechanism, even under Caspase-8 inhibition no Daxx-mediated modulation of the CD95-mediated apoptosis was detectable and moreover, no differences in CD95-mediated JNK aktivation were obvious as shown by in vitro kinase assays. 5.Treatment of both GFP-Daxx transduced cell lines with various anticancer drugs points to a protective role of Daxx during Taxol®-dependent apoptosis of clearCa-2/GFP-Daxx, which is probably mediated by an enhanced activation of the p38/JNK pathway as shown by in vitro kinase assays.

Conclusions: Our study suggests that the CD95-mediated apoptosis in renal cell carcinoma is not effected by the overexpression of the apoptosis enhancer Daxx. In contrast, the data indicate a rather anti-apoptotic than pro-apoptotic role for Daxx in human RCC as shown by the Daxx overexpression-mediated protective effect during Taxol-dependent apoptosis in the RCC cell line clearCa-2.