Induction of apoptosis coupled to endoplasmic reticulum stress in human prostate cancer cells by n-butylidenephthalide.

Mei-Jen Wang,Shinn-Zong Lin,Sheng-Chun Chiu,Horng-Jyh Harn,Ashraf B. Abdel-Naim,Cheng-Yoong Pang,Shee-Ping Chen,Sung-Ying Huang

doi:10.1371/journal.pone.0033742

Abstract

Background N-butylidenephthalide (BP) exhibits antitumor effect in a variety of cancer cell lines. The objective of this study was to obtain additional insights into the mechanisms involved in BP induced cell death in human prostate cancer cells.Methods/Principal FindingsTwo human prostate cancer cell lines, PC-3 and LNCaP, were treated with BP, and subsequently evaluated for their viability and cell cycle profiles. BP caused cell cycle arrest and cell death in both cell lines. The G0/G1 phase arrest was correlated with increase levels of CDK inhibitors (p16, p21 and p27) and decrease of the checkpoint proteins. To determine the mechanisms of BP-induced growth arrest and cell death in prostate cancer cell lines, we performed a microarray study to identify alterations in gene expression induced by BP in the LNCaP cells. Several BP-induced genes, including the GADD153/CHOP, an endoplasmic reticulum stress (ER stress)-regulated gene, were identified. BP-induced ER stress was evidenced by increased expression of the downstream molecules GRP78/BiP, IRE1-α and GADD153/CHOP in both cell lines. Blockage of IRE1-α or GADD153/CHOP expression by siRNA significantly reduced BP-induced cell death in LNCaP cells. Furthermore, blockage of JNK1/2 signaling by JNK siRNA resulted in decreased expression of IRE1-α and GADD153/CHOP genes, implicating that BP-induced ER stress may be elicited via JNK1/2 signaling in prostate cancer cells. BP also suppressed LNCaP xenograft tumor growth in NOD-SCID mice. It caused 68% reduction in tumor volume after 18 days of treatment.ConclusionsOur results suggest that BP can cause G0/G1 phase arrest in prostate cancer cells and its cytotoxicity is mediated by ER stress induction. Thus, BP may serve as an anticancer agent by inducing ER stress in prostate cancer.

Highlights

Prostate cancer is the most common malignancy in American men and the second leading cause of deaths from cancer [1]
Our results suggest that BP can cause G0/G1 phase arrest in prostate cancer cells and its cytotoxicity is mediated by endoplasmic reticulum (ER) stress induction
BP may serve as an anticancer agent by inducing ER stress in prostate cancer

Summary

Introduction

Prostate cancer is the most common malignancy in American men and the second leading cause of deaths from cancer [1]. One of the most common chemotherapy agent used for the treatment of prostate cancer are the taxanes, such as the first generation drug paclitaxel (Taxol, a trademark of Bristol-Myers Squibb) [2,3]. N-butylidenephthalide (BP), a compound isolated from Angelica sinensis chloroform extract, exhibits growth inhibitory activity on various human cancer cell lines, including brain, lung and liver cancer cells. BP caused growth arrest and apoptosis in these tumor cells in vitro and in vivo [5,6,7]. These findings indicate that BP is a promising new anticancer compound with a potential for clinical application. The objective of this study was to obtain additional insights into the mechanisms involved in BP induced cell death in human prostate cancer cells

Objectives

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Results

Conclusion