Institute of Nutrition, College of Biopharmaceutical and Food Sciences, China Medical University, 91, Hsueh-Shih Road, Taichung, 40402, Taiwan.
Department of Cosmeceutics, College of Biopharmaceutical and Food Sciences, China Medical University, 91, Hsueh-Shih Road, Taichung, 40402, Taiwan.
Arch Toxicol. 2017 Oct;91(10):3341-3364. doi: 10.1007/s00204-017-1967-0. Epub 2017 Apr 3.
Flavokawain B (FKB), a naturally occurring chalcone in kava extracts, has been reported to possess anticancer activity. However, the effect of FKB on gastric cancer remains unclear. We examined the in vitro and in vivo anticancer activity and autophagy involvement of FKB and determined the underlying molecular mechanisms. FKB is potently cytotoxic to human gastric cancer cells (AGS/NCI-N87/KATO-III/TSGH9201) and mildly toxic towards normal (Hs738) cells and primary mouse hepatocytes. FKB-induced AGS cell death was characterized by autophagy, not apoptosis, as evidenced by increased LC3-II accumulation, GFP-LC3 puncta and acidic vesicular organelles (AVOs) formation, without resulting procaspase-3/PARP cleavage. FKB further caused p62/SQSTM1 activation, mTOR downregulation, ATG4B inhibition, and Beclin-1/Bcl-2 dysregulation. Silencing autophagy inhibitors CQ/3-MA and LC3 (shRNA) significantly reversed the FKB-induced cell death of AGS cells. FKB-triggered ROS generation and ROS inhibition by NAC pre-treatment diminished FKB-induced cell death, LC3 conversion, AVO formation, p62/SQSTM1 activation, ATG4B inhibition and Beclin-1/Bcl-2 dysregulation, which indicated ROS-mediated autophagy in AGS cells. Furthermore, FKB induces G/M arrest and alters cell-cycle proteins through ROS-JNK signaling. Interestingly, FKB-induced autophagy is associated with the suppression of HER-2 and PIK/AKT/mTOR signaling cascades. FKB inhibits apoptotic Bax expression, and Bax-transfected AGS cells exhibit both apoptosis and autophagy; thus, FKB-inactivated Bax results in apoptosis inhibition. In vivo data demonstrated that FKB effectively inhibited tumor growth, prolonged the survival rate, and induced autophagy in AGS-xenografted mice. Notably, silencing of LC3 attenuated FKB-induced autophagy in AGS-xenografted tumors. FKB may be a potential chemopreventive agent in the activation of ROS-mediated autophagy of gastric cancer cells.
flavokawain B（FKB）是卡瓦提取物中的一种天然查尔酮，据报道具有抗癌活性。然而，FKB 对胃癌的影响尚不清楚。我们研究了 FKB 的体外和体内抗癌活性和自噬作用，并确定了潜在的分子机制。FKB 对人胃癌细胞（AGS/NCI-N87/KATO-III/TSGH9201）具有很强的细胞毒性，对正常（Hs738）细胞和原代小鼠肝细胞具有轻度毒性。FKB 诱导的 AGS 细胞死亡的特征是自噬，而不是凋亡，这表现在 LC3-II 积累增加、GFP-LC3 斑点和酸性囊泡细胞器（AVOs）形成，而没有导致 procaspase-3/PARP 裂解。FKB 进一步导致 p62/SQSTM1 激活、mTOR 下调、ATG4B 抑制和 Beclin-1/Bcl-2 失调。沉默自噬抑制剂 CQ/3-MA 和 LC3（shRNA）显著逆转了 FKB 诱导的 AGS 细胞死亡。FKB 触发的 ROS 生成和 NAC 预处理抑制 ROS 生成减少了 FKB 诱导的细胞死亡、LC3 转化、AVO 形成、p62/SQSTM1 激活、ATG4B 抑制和 Beclin-1/Bcl-2 失调，表明 AGS 细胞中的 ROS 介导的自噬。此外，FKB 通过 ROS-JNK 信号诱导 G/M 期阻滞和改变细胞周期蛋白。有趣的是，FKB 诱导的自噬与 HER-2 和 PIK/AKT/mTOR 信号通路的抑制有关。FKB 抑制凋亡 Bax 表达，转染 Bax 的 AGS 细胞表现出凋亡和自噬；因此，FKB 失活 Bax 导致凋亡抑制。体内数据表明，FKB 有效抑制肿瘤生长，延长存活率，并在 AGS 异种移植小鼠中诱导自噬。值得注意的是，沉默 LC3 减弱了 FKB 诱导的 AGS 异种移植瘤中的自噬。FKB 可能是一种潜在的化学预防剂，可激活胃癌细胞中的 ROS 介导的自噬。
