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Open Access Highly Accessed Research article

Activation of NAG-1 via JNK signaling revealed an isochaihulactone-triggered cell death in human LNCaP prostate cancer cells

Sheng-Chun Chiu12, Mei-Jen Wang12, Hsueh-Hui Yang2, Shee-Ping Chen3, Sung-Ying Huang4, Yi-Lin Chen5, Shinn-Zong Lin6, Horng-Jyh Harn7* and Cheng-Yoong Pang12*

Author Affiliations

1 Institute of Medical Sciences, Tzu-Chi University, Hualien, Taiwan

2 Department of Medical Research, Buddhist Tzu-Chi General Hospital, Hualien, Taiwan

3 Tzu-Chi Stem Cell Centre, Buddhist Tzu-Chi General Hospital, Hualien, Taiwan

4 Department of Ophthalmology, Mackay Memorial Hospital, Hsinchu, Taiwan

5 Graduate Institute of Biotechnology, National Ilan University, Ilan, Taiwan

6 Center for Neuropsychiatry, China Medical University Hospital, Taichung, Taiwan

7 Pathology Department, China Medical University, Taichung, Taiwan

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BMC Cancer 2011, 11:146  doi:10.1186/1471-2407-11-146

Published: 20 April 2011

Abstract

Background

We explored the mechanisms of cell death induced by isochaihulactone treatment in LNCaP cells.

Methods

LNCaP cells were treated with isochaihulactone and growth inhibition was assessed. Cell cycle profiles after isochaihulactone treatment were determined by flow cytometry. Expression levels of cell cycle regulatory proteins, caspase 9, caspase 3, and PARP were determined after isochaihulactone treatment. Signaling pathway was verified by inhibitors pre-treatment. Expression levels of early growth response gene 1 (EGR-1) and nonsteroidal anti-inflammatory drug-activated gene 1 (NAG-1) were determined to investigate their role in LNCaP cell death. NAG-1 expression was knocked down by si-NAG-1 siRNA transfection. Rate of cell death and proliferation were obtained by MTT assay.

Results

Isochaihulactone caused cell cycle arrest at G2/M phase in LNCaP cells, which was correlated with an increase of p53 and p21 levels and downregulation of the checkpoint proteins cdc25c, cyclin B1, and cdc2. Bcl-2 phosphorylation and caspase activation were also observed. Isochaihulactone induced phosphorylation of c-Jun-N-terminal kinase (JNK), and JNK inhibitor partially reduced isochaihulactone-induced cell death. Isochaihulactone also induced the expressions of EGR-1 and NAG-1. Expression of NAG-1 was reduced by JNK inhibitor, and knocking down of NAG-1 inhibited isochaihulactone-induced cell death.

Conclusions

Isochaihulactone apparently induces G2/M cell cycle arrest via downregulation of cyclin B1 and cdc2, and induces cellular death by upregulation of NAG-1 via JNK activation in LNCaP cells.