Wu Ching-An, Chao Yee, Shiah Shine-Gwo, Lin Wan-Wan
Department of Pharmacology, National Taiwan University, Taipei, Taiwan.
Biochim Biophys Acta. 2013 May;1833(5):1147-56. doi: 10.1016/j.bbamcr.2013.01.025. Epub 2013 Jan 31.
The Warburg effect is known to be crucial for cancer cells to acquire energy. Nutrient deficiencies are an important phenomenon in solid tumors, but the effect on cancer cell metabolism is not yet clear. In this study, we demonstrate that starvation of HeLa cells by incubation with Hank's buffered salt solution (HBSS) induced cell apoptosis, which was accompanied by the induction of reactive oxygen species (ROS) production and AMP-activated protein kinase (AMPK) phosphorylation. Notably, HBSS starvation increased lactate production, cytoplasmic pyruvate content and decreased oxygen consumption, but failed to change the lactate dehydrogenase (LDH) activity or the glucose uptake. We found that HBSS starvation rapidly induced pyruvate dehydrogenase kinase (PDK) activation and pyruvate dehydrogenase (PDH) phosphorylation, both of which were inhibited by compound C (an AMPK inhibitor), NAC (a ROS scavenger), and the dominant negative mutant of AMPK. Our data further revealed the involvement of ROS production in AMPK activation. Moreover, DCA (a PDK inhibitor), NAC, and compound C all significantly decreased HBSS starvation-induced lactate production accompanied by enhancement of HBSS starvation-induced cell apoptosis. Not only in HeLa cells, HBSS-induced lactate production and PDH phosphorylation were also observed in CL1.5, A431 and human umbilical vein endothelial cells. Taken together, we for the first time demonstrated that a low-nutrient condition drives cancer cells to utilize glycolysis to produce ATP, and this increases the Warburg effect through a novel mechanism involving ROS/AMPK-dependent activation of PDK. Such an event contributes to protecting cells from apoptosis upon nutrient deprivation.
已知瓦伯格效应对于癌细胞获取能量至关重要。营养缺乏是实体瘤中的一种重要现象，但对癌细胞代谢的影响尚不清楚。在本研究中，我们证明用汉克氏平衡盐溶液（HBSS）孵育使HeLa细胞饥饿会诱导细胞凋亡，同时伴有活性氧（ROS）生成增加和AMP激活的蛋白激酶（AMPK）磷酸化。值得注意的是，HBSS饥饿增加了乳酸生成、细胞质丙酮酸含量并降低了耗氧量，但未能改变乳酸脱氢酶（LDH）活性或葡萄糖摄取。我们发现HBSS饥饿迅速诱导丙酮酸脱氢酶激酶（PDK）激活和丙酮酸脱氢酶（PDH）磷酸化，这两者均被化合物C（一种AMPK抑制剂）、NAC（一种ROS清除剂）和AMPK的显性负突变体抑制。我们的数据进一步揭示了ROS生成参与AMPK激活。此外，二氯乙酸（DCA，一种PDK抑制剂）、NAC和化合物C均显著降低了HBSS饥饿诱导的乳酸生成，并伴随着HBSS饥饿诱导的细胞凋亡增强。不仅在HeLa细胞中如此，在CL1.5、A431和人脐静脉内皮细胞中也观察到了HBSS诱导的乳酸生成和PDH磷酸化。综上所述，我们首次证明低营养条件驱使癌细胞利用糖酵解产生ATP，并且这通过一种涉及ROS/AMPK依赖性激活PDK的新机制增加了瓦伯格效应。这样的事件有助于保护细胞在营养剥夺时免于凋亡。
