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Tirapazamine Cytotoxicity for Neuroblastoma Is p53 Dependent
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| Zeitschriftentitel: | Clinical Cancer Research |
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| Personen und Körperschaften: | , |
| In: | Clinical Cancer Research, 11, 2005, 7, S. 2774-2780 |
| Format: | E-Article |
| Sprache: | Englisch |
| veröffentlicht: |
American Association for Cancer Research (AACR)
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| Schlagwörter: |
| Zusammenfassung: | <jats:title>Abstract</jats:title> <jats:p>Relapse of neuroblastoma commonly occurs in hypoxic tissues, and is associated with an acquired and sustained high-level drug resistance, often due to p53 loss of function. Abrogating p53 function with HPV 16 E6 transduction in drug-sensitive neuroblastoma cell lines caused high-level drug resistance. Tirapazamine (TPZ) is a bioreductive agent that forms a toxic free radical in hypoxia. We determined in six neuroblastoma cell lines the cytotoxicity of TPZ using DIMSCAN, a digital imaging fluorescence assay, apoptosis and mitochondrial membrane potential (ΔΨm) by flow cytometry, and protein expression by immunoblotting. TPZ exhibited high cytotoxicity, especially in hypoxia (2% O2), for all four p53-functional neuroblastoma cell lines, achieving &gt;3 logs of cell kill (LC99 ≤ 0.7 μg/mL). In p53-nonfunctional neuroblastoma cell lines, all TPZ LC99 values were &gt;3.0 μg/mL (average clinically achievable level). TPZ (24 hours) induced apoptosis in &gt;46% of cells in p53-functional cell lines but failed to cause apoptosis in p53 nonfunctional cell lines. Induction of p53 and p21 expression by TPZ was observed in a p53-functional cell line (SMS-SAN) but not in a p53-nonfunctional cell line (CHLA-90). Significant ΔΨm loss and glutathione (GSH) depletion in response to TPZ was observed in p53-functional cell lines (SMS-SAN, SMS-SAN EV, and CHLA-15) but not in p53-nonfunctional cell lines (SMS-SAN E6 and CHLA-90). N-Acetylcysteine inhibited TPZ-mediated ΔΨm loss and GSH depletion, but neither N-acetylcysteine nor Boc-d-fmk inhibited apoptosis caused by TPZ. In response to TPZ, ΔΨm loss preceded apoptosis. Thus, TPZ cytotoxicity for neuroblastoma cell lines in hypoxia occurred via a p53-dependent mitochondrial pathway that caused induction of p53 and p21, ΔΨm decrease, GSH depletion, and apoptosis. These data further define the mechanism of action of TPZ and suggest that as a single agent, TPZ would only have clinical activity against p53-functional neuroblastomas.</jats:p> |
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| Umfang: | 2774-2780 |
| ISSN: |
1078-0432
1557-3265 |
| DOI: | 10.1158/1078-0432.ccr-04-2382 |