Journal Article

Cathepsin D protects human neuroblastoma cells from doxorubicin-induced cell death

Vitalia Sagulenko, Daniel Muth, Evgeny Sagulenko, Tobias Paffhausen, Manfred Schwab and Frank Westermann

in Carcinogenesis

Volume 29, issue 10, pages 1869-1877
Published in print October 2008 | ISSN: 0143-3334
Published online June 2008 | e-ISSN: 1460-2180 | DOI: http://dx.doi.org/10.1093/carcin/bgn147
Cathepsin D protects human neuroblastoma cells from doxorubicin-induced cell death

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High incidence of chemotherapy resistance is the primary cause of treatment failure in a subset of neuroblastomas with amplified MYCN. We have reported previously that ectopic MYCN expression promotes proliferation of neuroblastoma Tet21N cells and simultaneously sensitizes them to the drug-induced apoptosis. In search for genes that are involved in MYCN-dependent regulation of drug resistance, we used a function-based gene cloning approach and identified CTSD encoding for a lysosomal aspartyl protease cathepsin D. Downregulation of cathepsin D expression by RNA interference or inhibition of its enzymatic activity increased sensitivity of MYCN-expressing Tet21N cells to doxorubicin. Overexpression of cathepsin D in Tet21N cells attenuated doxorubicin-induced apoptosis. It was accompanied by activation of protein kinase B (Akt) and persistent antiapoptotic activity of Bcl-2. In primary neuroblastomas, high CTSD messenger RNA (mRNA) levels were associated with amplified MYCN, a strong predictive marker of adverse outcome. Chromatin immunoprecipitation and luciferase promoter assays revealed that MYCN protein binds to the CTSD promoter and activates its transcription, suggesting a direct link between deregulated MYCN and CTSD mRNA expression. We further show that neuroblastoma cells can secrete mitogenic procathepsin D and that MYCN expression and especially doxorubicin treatment promote procathepsin D secretion. Extracellular exogenous cathepsin D induces Akt-1 phosphorylation and doxorubicin resistance in sensitive cells. These results demonstrate an important role of cathepsin D in antiapoptotic signaling in neuroblastoma cells and suggest a novel mechanism for the development of chemotherapy resistance in neuroblastoma.

Journal Article.  6722 words.  Illustrated.

Subjects: Clinical Cytogenetics and Molecular Genetics

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