microRNA-558 facilitates the expression of hypoxia-inducible factor 2 alpha through binding to 5'-untranslated region in neuroblastoma.

// Hongxia Qu 1, * , Liduan Zheng 2, 3, * , Huajie Song 1 , Wanju Jiao 2 , Dan Li 1 , Erhu Fang 1 , Xiaojing Wang 1 , Hong Mei 1 , Jiarui Pu 1 , Kai Huang 3 , Qiangsong Tong 1, 3 1 Department of Pediatric Surgery, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, Hubei Province, P. R. China 2 Department of Pathology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, Hubei Province, P. R. China 3 Clinical Center of Human Genomic Research, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, Hubei Province, P. R. China * These authors have contributed equally to this work Correspondence to: Qiangsong Tong, email: qs_tong@hotmail.com Keywords: neuroblastoma, microRNA-558, hypoxia-inducible factor 2 alpha, Argonaute 2, eukaryotic translation initiation factor 4E Received: February 12, 2016     Accepted: May 20, 2016     Published: June 3, 2016 ABSTRACT Neuroblastoma (NB) is the most common extracranial solid tumor in childhood. Our previous studies have shown that hypoxia-inducible factor 2 alpha (HIF-2α), one member of the bHLH-PAS transcription factor family, facilitates the progression of NB under non-hypoxic conditions. However, the mechanisms underlying HIF-2α expression in NB still remain largely unknown. Herein, through analyzing the computational algorithm programs, we identified microRNA-558 (miR-558) as a crucial regulator of HIF-2α expression in NB. We demonstrated that miR-558 promoted the expression of HIF-2α at translational levels in NB cells through recruiting Argonaute 2 (AGO2). Mechanistically, miR-558 directly bound with its complementary site within 5’-untranslated region (5’-UTR) to facilitate the binding of AGO2 to eukaryotic translation initiation factor 4E (eIF4E) binding protein 1, resulting in increased eIF4E enrichment and HIF-2α translation. In addition, miR-558 promoted the growth, invasion, metastasis, and angiogenesis of NB cells in vitro and in vivo , and these biological features were rescued by knockdown of AGO2 , eIF4E , or HIF-2α . In clinical NB specimens, miR-558, AGO2, and eIF4E were highly expressed and positively correlated with HIF-2α expression. Patients with high miR-558, HIF-2α, AGO2, or eIF4E levels had lower survival probability. Taken together, these results demonstrate that miR-558 facilitates the expression of HIF-2α through bindingto its 5’-UTR, thus promoting the tumorigenesis and aggressiveness of NB.