ADIPOQ/adiponectin induces cytotoxic autophagy in breast cancer cells through STK11/LKB1-mediated activation of the AMPK-ULK1 axis
ADIPOQ/adiponectin induces cytotoxic autophagy in breast cancer cells through STK11/LKB1-mediated activation of the AMPK-ULK1 axis
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DOI：
10.1080/15548627.2017.1332565
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发表时间：
2017-01-01
期刊：
影响因子：
13.3
通讯作者：
Sharma, Dipali
中科院分区：
文献类型：
--
作者：
Chung, Seung J.;Nagaraju, Ganji Purnachandra;Sharma, Dipali
ADIPOQ/脂联素是乳腺肿瘤微环境中脂肪细胞分泌的一种脂肪细胞因子，负调控癌细胞生长，因此ADIPOQ/脂联素水平升高与乳腺癌生长降低相关。然而，其作用机制在很大程度上仍然难以捉摸。我们报告ADIPOQ/脂联素诱导乳腺癌细胞中自噬体的大量积累，增加MAP 1 LC 3B-II/LC 3B-II并降低SQSTM 1/p62。ADIPOQ/脂联素处理的细胞和异种移植物表现出自噬相关蛋白的表达增加。LysoTracker Red染色和Tandemm-Cherry-GFP-LC 3B测定显示，ADIPOQ/脂联素处理后，自噬体和溶酶体的融合增强。ADIPOQ/脂联素在体外和体内均显著抑制乳腺癌生长并诱导细胞凋亡，并且这些事件之前是大自噬/自噬，其是ADIPOQ/脂联素介导的细胞死亡的组成部分。因此，钝化自噬体形成、阻断自噬体-溶酶体融合或基因敲除BECN 1/Beclin 1和ATG 7可有效地阻止ADIPOQ/脂联素诱导的生长抑制和凋亡诱导。机制研究表明，ADIPOQ/脂联素降低细胞内ATP水平并增加PRKAA 1磷酸化，导致ULK 1活化。AMPK抑制消除ADIPOQ/脂联素诱导的ULK 1激活、LC 3B转换和SQSTM 1/p62降解，而AMPK激活增强ADIPOQ/脂联素的作用。此外，ADIPOQ/脂联素介导的AMPK激活和自噬诱导受上游主激酶STK 11/LKB 1调节，这是ADIPOQ/脂联素抗肿瘤功能的关键节点，因为STK 11/LKB 1敲除消除了ADIPOQ/脂联素介导的乳腺肿瘤发生抑制，并且肿瘤的分子分析证实了体外机制发现。ADIPOQ/脂联素增加化疗药物的疗效。值得注意的是，ADIPOQ受体ADIPOR 2、ADIPOQ/脂联素和BECN 1的高表达与化疗治疗的乳腺癌患者的总生存率增加显著相关。总之，这些数据揭示了ADIPOQ/脂联素诱导乳腺癌中的自噬细胞死亡，并为STK 11/LKB 1-AMPK-ULK 1轴在ADIPOQ/脂联素介导的细胞毒性自噬中的整体作用提供了体外和体内证据。
ADIPOQ/adiponectin, an adipocytokine secreted by adipocytes in the breast tumor microenvironment, negatively regulates cancer cell growth hence increased levels of ADIPOQ/adiponectin are associated with decreased breast cancer growth. However, its mechanisms of action remain largely elusive. We report that ADIPOQ/adiponectin induces a robust accumulation of autophagosomes, increases MAP1LC3B-II/LC3B-II and decreases SQSTM1/p62 in breast cancer cells. ADIPOQ/adiponectin-treated cells and xenografts exhibit increased expression of autophagy-related proteins. LysoTracker Red-staining and tandemm-Cherry-GFP-LC3B assay show that fusion of autophagosomes and lysosomes is augmented upon ADIPOQ/adiponectin treatment. ADIPOQ/adiponectin significantly inhibits breast cancer growth and induces apoptosis both in vitro and in vivo, and these events are preceded by macroautophagy/autophagy, which is integral for ADIPOQ/adiponectin-mediated cell death. Accordingly, blunting autophagosome formation, blocking autophagosome-lysosome fusion or genetic-knockout of BECN1/Beclin1 and ATG7 effectively impedes ADIPOQ/adiponectin induced growth-inhibition and apoptosis-induction. Mechanistic studies show that ADIPOQ/adiponectin reduces intracellular ATP levels and increases PRKAA1 phosphorylation leading to ULK1 activation. AMPK-inhibition abrogates ADIPOQ/adiponectin-induced ULK1-activation, LC3B-turnover and SQSTM1/p62-degradation while AMPK-activation potentiates ADIPOQ/adiponectin's effects. Further, ADIPOQ/adiponectin-mediated AMPK-activation and autophagy-induction are regulated by upstream master-kinase STK11/LKB1, which is a key node in antitumor function of ADIPOQ/adiponectin as STK11/LKB1-knockout abrogates ADIPOQ/adiponectin-mediated inhibition of breast tumorigenesis and molecular analyses of tumors corroborate in vitro mechanistic findings. ADIPOQ/adiponectin increases the efficacy of chemotherapeutic agents. Notably, high expression of ADIPOQ receptor ADIPOR2, ADIPOQ/adiponectin and BECN1 significantly correlates with increased overall survival in chemotherapy-treated breast cancer patients. Collectively, these data uncover that ADIPOQ/adiponectin induces autophagic cell death in breast cancer and provide in vitro and in vivo evidence for the integral role of STK11/LKB1-AMPK-ULK1 axis in ADIPOQ/adiponectin-mediated cytotoxic autophagy.