Department of Surgery, Rutgers Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, 1 Robert Wood Johnson Place, New Brunswick, NJ, 08903, USA.
Molecular Design and Synthesis, RUBRIC, Office for Research, Rutgers Translational Science, Rutgers University, Piscataway, NJ, 08854, USA.
Cell Commun Signal. 2022 Jun 27;20(1):99. doi: 10.1186/s12964-022-00905-4.
Bone morphogenetic proteins (BMP) are evolutionarily conserved morphogens that are reactivated in lung carcinomas. In lung cancer cells, BMP signaling suppresses AMP activated kinase (AMPK) by inhibiting LKB1. AMPK is activated by mitochondrial stress that inhibits ATP production, which is enhanced 100-fold when phosphorylated by LKB1. Activated AMPK can promote survival of cancer cells but its "hyperactivation" induces cell death. The studies here reveal novel cell death mechanisms induced by BMP inhibitors, together with agents targeting the mitochondria, which involves the "hyperactivation" of AMPK.
This study examines the synergistic effects of two BMP inhibitors together with mitochondrial targeting agents phenformin and Ym155, on cell death of lung cancer cells expressing LKB1 (H1299), LKB1 null (A549), and A549 cells transfected with LKB1 (A549-LKB1). Cell death mechanisms evaluated were the activation of caspases and the nuclear localization of apoptosis inducing factor (AIF). A769662 was used to allosterically activate AMPK. Knockdown of BMPR2 and LKB1 using siRNA was used to examine their effects on nuclear localization of AMPK. Validation studies were performed on five passage zero primary NSCLC.
Both BMP inhibitors synergistically suppressed growth when combined with Ym155 or phenformin in cells expressing LKB1. The combination of BMP inhibitors with mitochondrial targeting agents enhanced the activation of AMPK in lung cancer cells expressing LKB1. Allosteric activation of AMPK with A769662 induced cell death in both H1299 and A549 cells. Cell death induced by the combination of BMP inhibitors and mitochondrial-targeting agents did not activate caspases. The combination of drugs induced nuclear localization of AIF in cells expressing LKB1, which was attenuated by knockdown of LKB1. Knockdown of BMPR2 together with Ym155 increased nuclear localization of AIF. Combination therapy also enhanced cell death and AIF nuclear localization in primary NSCLC.
These studies demonstrate that inhibition of BMP signaling together with mitochondrial targeting agents induce AIF caspase-independent cell death, which involves the "hyperactivation" of AMPK. AIF caspase-independent cell death is an evolutionarily conserved cell death pathway that is infrequently studied in cancer. These studies provide novel insight into mechanisms inducing AIF caspase-independent cell death in cancer cells using BMP inhibitors. Video Abstract.
骨形态发生蛋白（BMP）是进化上保守的形态发生素，在肺癌中被重新激活。在肺癌细胞中，BMP 信号通过抑制 LKB1 来抑制 AMP 激活的蛋白激酶（AMPK）。AMPK 被抑制 ATP 产生的线粒体应激激活，而当被 LKB1 磷酸化时，这种抑制作用会增强 100 倍。激活的 AMPK 可以促进癌细胞的存活，但它的“过度激活”会诱导细胞死亡。本研究揭示了 BMP 抑制剂与靶向线粒体的药物联合使用所诱导的新型细胞死亡机制，这涉及到 AMPK 的“过度激活”。
本研究检测了两种 BMP 抑制剂与线粒体靶向药物二甲双胍和 Ym155 联合使用对表达 LKB1（H1299）、缺乏 LKB1（A549）的肺癌细胞以及转染 LKB1 的 A549 细胞（A549-LKB1）的细胞死亡的协同效应。评估的细胞死亡机制包括半胱天冬酶的激活和凋亡诱导因子（AIF）的核定位。A769662 用于别构激活 AMPK。使用 siRNA 敲低 BMPR2 和 LKB1 以研究它们对 AMPK 核定位的影响。在五个零传代的原发性 NSCLC 中进行了验证研究。
在表达 LKB1 的细胞中，两种 BMP 抑制剂与 Ym155 或二甲双胍联合使用均能协同抑制生长。BMP 抑制剂与线粒体靶向药物联合使用可增强表达 LKB1 的肺癌细胞中 AMPK 的激活。A769662 对 AMPK 的别构激活可诱导 H1299 和 A549 细胞的细胞死亡。BMP 抑制剂与线粒体靶向药物联合使用诱导的细胞死亡不激活半胱天冬酶。药物联合使用可诱导表达 LKB1 的细胞中 AIF 的核定位，LKB1 的敲低可减弱这一作用。BMPR2 与 Ym155 的联合敲低增加了 AIF 的核定位。联合治疗还增强了原发性 NSCLC 中的细胞死亡和 AIF 核定位。
这些研究表明，抑制 BMP 信号与靶向线粒体的药物联合使用可诱导 AIF 不依赖半胱天冬酶的细胞死亡，这涉及到 AMPK 的“过度激活”。AIF 不依赖半胱天冬酶的细胞死亡是一种进化上保守的细胞死亡途径，在癌症中很少被研究。这些研究为使用 BMP 抑制剂诱导癌细胞中 AIF 不依赖半胱天冬酶的细胞死亡提供了新的见解。
