Mitochondrial calcium uniporter as a target of microRNA-340 and promoter of metastasis via enhancing the Warburg effect

// Changhui Yu 1, 2 , Yuhao Wang 1 , Jiawen Peng 1 , Qiang Shen 3 , Mimi Chen 1 , Wei Tang 1 , Xiumei Li 4 , Chunqing Cai 1 , Bin Wang 1 , Shaoxi Cai 2 , Xiaojing Meng 1 and Fei Zou 1 1 Department of Occupational Health and Occupational Medicine, Guangdong Provincial Key Laboratory of Tropical Disease Research, School of Public Health, Southern Medical University, Guangzhou, China 2 Department of Respiratory and Critical Care Medicine, Chronic Airways Diseases Laboratory, Nanfang Hospital, Southern Medical University, Guangzhou, China 3 Department of Clinical Cancer Prevention, The University of Texas MD Anderson Cancer Center, Houston, Texas, U.S.A 4 Guangdong Provincial Key Laboratory of Gastroenterology, Department of Gastroenterology, Nanfang Hospital, Southern Medical University, Guangzhou, China Correspondence to: Xiaojing Meng, email: Xiaojingmeng@smu.edu.cn Fei Zou, email: zoufei616@163.com Keywords: breast cancer, metastasis, Warburg effect, mitochondrial calcium uniporter, microRNA-340 Received: March 26, 2017      Accepted: June 19, 2017      Published: July 31, 2017 ABSTRACT Background: A shift from oxygen phosphorylation to aerobic glycolysis was known as the Warburg effect and a characteristic of cancer cell metabolism facilitating metastasis. Mitochondrial calcium uniporter (MCU), a key ion channel that mediates Ca 2+ uptake into mitochondria, was found to promote cancer progression and metastasis. However, its explicit role in shifting metabolism of breast cancer cells has not been defined. Methods: We evaluated MCU overexpression or knock-down on migration, invasion and glucose metabolismin breast cancer cells. Mitochondrial Ca 2+ dynamics were monitored with Rhod-2 fluorescence imaging. Luciferase reporter assay was used to confirm the interaction between miR-340 and 3’-untranslated region (3’-UTR) of MCU gene. Mouse models of lung metastasis were used to determine whether gain-/loss-of-MCU impacts metastasis. MCU expression was assessed in 60 tumor samples from breast cancer patients by immunohistochemistry (IHC). Results: Knockdown of MCU in MDA-MB-231 cells significantly reduced cell migration and invasion in vitro and lung metastasis in vivo ; whereas overexpression of MCU in MCF-7 cells significantly increased migration and invasion in vitro and lung metastasis in vivo . Overexpression of MCU promoted lung metastasis by enhancing glycolysis, whereas suppression of MCU abolished this effect. Moreover, a novel mechanism was identified that MCU was a direct target of microRNA-340, which suppressed breast cancer cell motility by inhibiting glycolysis. Consistently, significantly increased MCU protein was found in metastatic breast cancer patients. Conclusions: We identified a novel mechanism that upregulated MCU promotes breast cancer metastasis via enhancing glycolysis, and that this process is posttranscriptionally and negatively regulated by microRNA-340.