miR-101 reverses hypomethylation of the PRDM16 promoter to disrupt mitochondrial function in astrocytoma cells

// Qianqian Lei 1, 3, * Xiaoping Liu 2, * , Haijuan Fu 3 , Yingnan Sun 1, 3 , Liping Wang 4 , Gang Xu 3 , Wei Wang 3 , Zhibin Yu 3 , Changhong Liu 3 , Peiyao Li 3 , Jianbo Feng 3 , Guiyuan Li 1, 3 , Minghua Wu 3 1 Hunan Provincial Tumor Hospital and The Affiliated Tumor Hospital of Xiangya Medical School, Central South University, Changsha 410013, Hunan, China 2 Department of Breast Oncology, Sun Yat-Sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou 510060, Guangdong, China 3 Cancer Research Institute, School of Basic Medical Science, Central South University, Key Laboratory of Carcinogenesis and Cancer Invasion, Ministry of Education, Key Laboratory of Carcinogenesis, Ministry of Health, Changsha 410078, Hunan, China 4 Department of Oncology, The First Hospital of Chenzhou City, 423000, Hunan, China * These authors have contributed equally to this work Correspondence to: Minghua Wu, e-mail: wuminghua554@aliyun.com Keywords: hypomethylation, mitochondria, miR-101, ROS, PRDM16 Received: August 16, 2015     Accepted: December 05, 2015     Published: December 18, 2015 ABSTRACT Our previous report identified PR domain containing 16 (PRDM16), a member of the PR-domain gene family, as a new methylation associated gene in astrocytoma cells. This previous study also reported that miR-101 is a tumor suppressor in glioma. The present study confirms that PRDM16 is a hypomethylated gene that can be overexpressed in astrocytoma patients and demonstrates that the hypomethylation status of the PRDM16 promoter can predict poor prognoses for astrocytoma patients. The results reported herein show that PRDM16 was inhibited by miR-101 directly and also through epigenetic regulation. PRDM16 was confirmed as a new target of miR-101 and shown to be directly inhibited by miR-101. miR-101 also decreased the expression of PRDM16 by altering the methylation status of the PRDM16 promoter. miR-101 was associated with a decrease in the methylation-related histones H3K4me2 and H3K27me3 and an increase in H3K9me3 and H4K20me3 on the PRDM16 promoter. In addition, EZH2, EED and DNMT3A were identified as direct targets of miR-101, and miR-101 suppressed PRDM16 expression by targeting DNMT3A which decreases histone H3K27me3 and H3K4me2 at the PRDM16 core promoter. The results reported here demonstrate that miR-101 disrupted cellular mitochondrial function and induced cellular apoptosis via the mitochondrial pathway; for example, MMP and ATP levels decreased, while there was an increase in ADP/ATP ratios and ROS levels, levels of cleaved Caspase-9 and cleaved-PARP, the Bax/Bcl-2 ratios, and Smac release from the mitochondria to the cytoplasm. Knockdown of PRDM16 reversed the anti-apoptotic effect of miR-101 inhibition. In summary, miR-101 reversed the hypomethylation of the PRDM16 promoter which suppressed the expression of PRDM16, disrupted cellular mitochondrial function, and induced cellular apoptosis.