Ahn Yong-Tae, Shin Ik Jae, Kim Jong-Myoung, Kim Youn Sook, Lee Chu, Ju Seong-A, An Won G
Department of Biomedical Science, Kyungdong University, Goseong-gun, Gangwon-do 219-832, Republic of Korea.
Oncol Lett. 2013 Nov;6(5):1383-1389. doi: 10.3892/ol.2013.1547. Epub 2013 Aug 26.
The actin cytoskeleton is important in the maintenance of cellular homeostasis and in signal transduction pathways leading to cell growth and apoptotic cell death in eukaryotic cells. Disruption of actin dynamics is associated with morphological changes in cancer cells. Deletion of phosphatase and tensin homolog (PTEN), a tumor suppressor gene involved in the regulation of the cell cycle and apoptosis, leads to cytoskeleton disruption and double-strand breaks (DSBs). To study the mechanism(s) of actin disruption-mediated apoptosis and its potential application for anticancer therapy, PTEN-null PC3M prostate cancer cells were treated with latrunculin B (LB). LB induced destabilization of the actin microfilament and apoptosis in a dose-dependent manner, as demonstrated by morphological changes and nuclear condensation in the PC3M cells. In addition, it resulted in an increase in the levels of γH2AX recruitment, implicating the induction of DNA damage, including DSBs. Induction of Bax, with little effect on Bcl-2 expression, indicated that actin disruption causes apoptosis through activation of Bax signaling in PC3M cells. Treatment with U20126, a mitogen-activated protein kinase kinase (MEK) inhibitor, resulted in attenuated induction of DSBs and apoptosis through activation of protein kinase B (Akt), suggesting that LB-mediated actin dysfunction induces DSBs via the MEK/extracellular signal-regulated kinase (Erk) pathway in cells. Therefore, counteracting activation of phosphorylated Akt stemming from the inhibition of MEK/Erk resulted in attenuation of actin disruption-induced apoptotic events in the PC3M cells. The results of this study provide information not only for use in delineation of the molecular association between actin disruption and tumorigenesis, but also for the development of a strategy for actin-based anticancer chemotherapy against highly metastatic prostate cancer.
肌动蛋白细胞骨架在维持细胞内稳态以及真核细胞中导致细胞生长和凋亡性细胞死亡的信号转导途径中起着重要作用。肌动蛋白动力学的破坏与癌细胞的形态变化相关。磷酸酶和张力蛋白同源物（PTEN）是一种参与细胞周期调控和凋亡的肿瘤抑制基因，其缺失会导致细胞骨架破坏和双链断裂（DSB）。为了研究肌动蛋白破坏介导的凋亡机制及其在抗癌治疗中的潜在应用，用拉特肌毒素B（LB）处理PTEN缺失的PC3M前列腺癌细胞。如PC3M细胞中的形态变化和核浓缩所示，LB以剂量依赖性方式诱导肌动蛋白微丝的不稳定和凋亡。此外，它导致γH2AX募集水平增加，提示包括DSB在内的DNA损伤的诱导。Bax的诱导对Bcl-2表达影响很小，表明肌动蛋白破坏通过激活PC3M细胞中的Bax信号传导导致凋亡。用丝裂原活化蛋白激酶激酶（MEK）抑制剂U20126处理，通过激活蛋白激酶B（Akt）导致DSB和凋亡的诱导减弱，表明LB介导的肌动蛋白功能障碍通过细胞中的MEK/细胞外信号调节激酶（Erk）途径诱导DSB。因此，抵消源于MEK/Erk抑制的磷酸化Akt的激活导致PC3M细胞中肌动蛋白破坏诱导的凋亡事件减弱。本研究结果不仅为阐明肌动蛋白破坏与肿瘤发生之间的分子关联提供了信息，也为开发针对高转移性前列腺癌的基于肌动蛋白的抗癌化疗策略提供了信息。
