Department of Oncology, Johns Hopkins University School of Medicine and the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore MD 21231, USA.
Breast Cancer Res. 2012 Feb 21;14(1):R35. doi: 10.1186/bcr3128.
Honokiol, a small-molecule polyphenol isolated from magnolia species, is widely known for its therapeutic potential as an antiinflammatory, antithrombosis, and antioxidant agent, and more recently, for its protective function in the pathogenesis of carcinogenesis. In the present study, we sought to examine the effectiveness of honokiol in inhibiting migration and invasion of breast cancer cells and to elucidate the underlying molecular mechanisms.
Clonogenicity and three-dimensional colony-formation assays were used to examine breast cancer cell growth with honokiol treatment. The effect of honokiol on invasion and migration of breast cancer cells was evaluated by using Matrigel invasion, scratch-migration, spheroid-migration, and electric cell-substrate impedance sensing (ECIS)-based migration assays. Western blot and immunofluorescence analysis were used to examine activation of the liver kinase B1 (LKB1)-AMP-activated protein kinase (AMPK) axis. Isogenic LKB1-knockdown breast cancer cell line pairs were developed. Functional importance of AMPK activation and LKB1 overexpression in the biologic effects of honokiol was examined by using AMPK-null and AMPK-wild type (WT) immortalized mouse embryonic fibroblasts (MEFs) and isogenic LKB1-knockdown cell line pairs. Finally, mouse xenografts, immunohistochemical and Western blot analysis of tumors were used.
Analysis of the underlying molecular mechanisms revealed that honokiol treatment increases AMP-activated protein kinase (AMPK) phosphorylation and activity, as evidenced by increased phosphorylation of the downstream target of AMPK, acetyl-coenzyme A carboxylase (ACC) and inhibition of phosphorylation of p70S6kinase (pS6K) and eukaryotic translation initiation factor 4E binding protein 1 (4EBP1). By using AMPK-null and AMPK-WT (MEFs), we found that AMPK is required for honokiol-mediated modulation of pACC-pS6K. Intriguingly, we discovered that honokiol treatment increased the expression and cytoplasmic translocation of tumor-suppressor LKB1 in breast cancer cells. LKB1 knockdown inhibited honokiol-mediated activation of AMPK and, more important, inhibition of migration and invasion of breast cancer cells. Furthermore, honokiol treatment resulted in inhibition of breast tumorigenesis in vivo. Analysis of tumors showed significant increases in the levels of cytoplasmic LKB1 and phospho-AMPK in honokiol-treated tumors.
Taken together, these data provide the first in vitro and in vivo evidence of the integral role of the LKB1-AMPK axis in honokiol-mediated inhibition of the invasion and migration of breast cancer cells. In conclusion, honokiol treatment could potentially be a rational therapeutic strategy for breast carcinoma.
厚朴酚是一种从小茴香属植物中分离出来的小分子多酚，因其具有抗炎、抗血栓形成和抗氧化作用而被广泛应用，最近又因其在致癌发生过程中的保护作用而备受关注。在本研究中，我们试图研究厚朴酚抑制乳腺癌细胞迁移和侵袭的有效性，并阐明其潜在的分子机制。
用厚朴酚处理检测克隆形成和三维集落形成实验检测乳腺癌细胞的生长。通过 Matrigel 侵袭、划痕迁移、球体迁移和基于电细胞-底物阻抗感应（ECIS）的迁移实验评估厚朴酚对乳腺癌细胞侵袭和迁移的影响。Western blot 和免疫荧光分析用于检测肝激酶 B1（LKB1）-AMP 激活蛋白激酶（AMPK）轴的激活。建立 LKB1 敲低的乳腺癌细胞系对。使用 AMPK 缺陷型和 AMPK 野生型（WT）永生化小鼠胚胎成纤维细胞（MEFs）和 LKB1 敲低的细胞系对，研究 AMPK 激活和 LKB1 过表达在厚朴酚生物学效应中的功能重要性。最后，进行了小鼠异种移植、肿瘤免疫组织化学和 Western blot 分析。
对潜在分子机制的分析表明，厚朴酚处理增加了 AMPK 磷酸化和活性，这表现为 AMPK 的下游靶标乙酰辅酶 A 羧化酶（ACC）的磷酸化增加，以及 p70S6 激酶（pS6K）和真核翻译起始因子 4E 结合蛋白 1（4EBP1）磷酸化的抑制。通过使用 AMPK 缺陷型和 AMPK-WT（MEFs），我们发现 AMPK 是厚朴酚介导的 pACC-pS6K 调节所必需的。有趣的是，我们发现厚朴酚处理增加了乳腺癌细胞中肿瘤抑制因子 LKB1 的表达和细胞质易位。LKB1 敲低抑制了厚朴酚介导的 AMPK 激活，更重要的是，抑制了乳腺癌细胞的迁移和侵袭。此外，厚朴酚处理还导致体内乳腺癌肿瘤发生的抑制。肿瘤分析显示，厚朴酚处理的肿瘤中细胞质 LKB1 和磷酸化 AMPK 的水平显著增加。
综上所述，这些数据提供了 LKB1-AMPK 轴在厚朴酚介导的抑制乳腺癌细胞侵袭和迁移中的整体作用的第一个体外和体内证据。总之，厚朴酚治疗可能是治疗乳腺癌的合理治疗策略。
Zotero 插件
