Microtubule Dysfunction Induced by Paclitaxel Initiates Apoptosis through Both c-Jun N-terminal Kinase (JNK)-dependent and -Independent Pathways in Ovarian Cancer Cells

• Published in: The Journal of biological chemistry 1999-03, Vol.274 (12), p.8208-8216
• Main Authors: Wang, T H, Popp, D M, Wang, H S, Saitoh, M, Mural, J G, Henley, D C, Ichijo, H, Wimalasena, J
• Format: Article
• Language: English
• Subjects: Antineoplastic Agents, Phytogenic - pharmacology; Apoptosis; Calcium-Calmodulin-Dependent Protein Kinases - metabolism; Female; Humans; JNK Mitogen-Activated Protein Kinases; Microtubules - drug effects; Mitogen-Activated Protein Kinases; Ovarian Neoplasms - physiopathology; Paclitaxel - pharmacology; Proto-Oncogene Proteins c-bcl-2 - metabolism; Signal Transduction; Transfection; Tumor Cells, Cultured
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.12.8208

The antineoplastic agent paclitaxel (Taxol TM ), a microtubule stabilizing agent, is known to arrest cells at the G 2 /M phase of the cell cycle and induce apoptosis. We and others have recently demonstrated that paclitaxel also activates the c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) signal transduction pathway in various human cell types, however, no clear role has been established for JNK/SAPK in paclitaxel-induced apoptosis. To further examine the role of JNK/SAPK signaling cascades in apoptosis resulting from microtubular dysfunction induced by paclitaxel, we have coexpressed dominant negative (dn) mutants of signaling proteins of the JNK/SAPK pathway (Ras, ASK1, Rac, JNKK, and JNK) in human ovarian cancer cells with a selectable marker to analyze the apoptotic characteristics of cells expressing dn vectors following exposure to paclitaxel. Expression of these dn signaling proteins had no effect on Bcl-2 phosphorylation, yet inhibited apoptotic changes induced by paclitaxel up to 16 h after treatment. Coexpression of these dn signaling proteins had no protective effect after 48 h of paclitaxel treatment. Our data indicate that: (i) activated JNK/SAPK acts upstream of membrane changes and caspase-3 activation in paclitaxel-initiated apoptotic pathways, independently of cell cycle stage, (ii) activated JNK/SAPK is not responsible for paclitaxel-induced phosphorylation of Bcl-2, and (iii) apoptosis resulting from microtubule damage may comprise multiple mechanisms, including a JNK/SAPK-dependent early phase and a JNK/SAPK-independent late phase.