Department of Biological Science and Technology, School of Life Sciences, Longyan University, Longyan University, China.
Key Laboratory of Preventive Veterinary Medicine and Biotechnology (Longyan University), Fujian Province University, Longyan, China.
Biomed Res Int. 2018 May 24;2018:4780612. doi: 10.1155/2018/4780612. eCollection 2018.
Kitam. belongs to the Compositae family and has been traditionally used for the prevention of cancer, diabetes, and inflammation in China. Previous studies had indicated that the ethyl acetate extract of Kitam. leaves (EAEG) exhibited antioxidant and anti-inflammatory activity. In this report, we demonstrated that EAEG possessed potent anticancer activity through autophagy-mediated inhibition of cell proliferation. EAEG induced a strong cytostatic effect towards HeLa cells and, to a lesser extent, HepG2 and MCF-7 cells. This cytostatic effect of EAEG was not a consequence of increased apoptosis, as neither DNA fragmentation nor change in protein expression level for a number of apoptosis-related genes including Bid, Bax, Bcl-2, and caspase-3 was observed after EAEG treatment, and the apoptosis inhibitor Z-VAD-FMK did not inhibit the EAEG-elicited cytostatic effect. On the other hand, EAEG induced autophagy in a dose-dependent fashion, as shown by increased GFP puncta formation, enhanced conversion of the microtubule-associated protein light chain LC3-I to LC3-II, and downregulation of the p62 protein. Treating the HeLa cells with EAEG together with Chloroquine (CQ) further accelerated LC3 conversion and p62 clearance, indicating that EAEG induced complete autophagy flux. Importantly, the autophagy inhibitor 3-methyladenine (3MA) significantly abrogated the cytostatic effect of EAEG, strongly suggesting that EAEG inhibited HeLa cell proliferation through the induction of autophagy rather than apoptosis. Our results provided a novel and interesting mechanistic insight into the anticancer action of EAEG, supporting the traditional use of this plant for the treatment of the cancer.
Kitam. 属于菊科，在中国传统上被用于预防癌症、糖尿病和炎症。先前的研究表明，Kitam. 叶的乙酸乙酯提取物 (EAEG) 具有抗氧化和抗炎活性。在本报告中，我们证明 EAEG 通过自噬介导的细胞增殖抑制具有强大的抗癌活性。EAEG 对 HeLa 细胞表现出强烈的细胞生长抑制作用，对 HepG2 和 MCF-7 细胞的抑制作用较小。EAEG 的这种细胞生长抑制作用不是细胞凋亡增加的结果，因为在 EAEG 处理后，既没有观察到 DNA 片段化，也没有观察到包括 Bid、Bax、Bcl-2 和 caspase-3 在内的许多凋亡相关基因的蛋白表达水平发生变化，并且凋亡抑制剂 Z-VAD-FMK 不能抑制 EAEG 诱导的细胞生长抑制作用。另一方面，EAEG 以剂量依赖性方式诱导自噬，如 GFP 斑点形成增加、微管相关蛋白轻链 LC3-I 向 LC3-II 的转化增强以及 p62 蛋白下调。用 EAEG 和氯喹 (CQ) 共同处理 HeLa 细胞进一步加速了 LC3 的转化和 p62 的清除，表明 EAEG 诱导了完全的自噬流。重要的是，自噬抑制剂 3-甲基腺嘌呤 (3MA) 显著消除了 EAEG 的细胞生长抑制作用，强烈表明 EAEG 通过诱导自噬而不是凋亡抑制 HeLa 细胞增殖。我们的研究结果为 EAEG 的抗癌作用提供了一个新颖而有趣的机制见解，支持了该植物在癌症治疗中的传统用途。
