Role of VHL, HIF1A and SDH on the expression of miR-210: Implications for tumoral pseudo-hypoxic fate.

// Anna Merlo 1, * , Cristobal Bernardo-Castineira 1, * , Ines Saenz-de-Santa-Maria 1 , Ana S Pitiot 2 , Milagros Balbin 2 , Aurora Astudillo 3 , Nuria Valdes 4 , Bartolome Scola 5 , Raquel Del Toro 6, 7 , Simon Mendez-Ferrer 6, 8 , Jose I Piruat 7 , Carlos Suarez 1 , Maria-Dolores Chiara 1 1 Otorhinolaryngology Service, Hospital Universitario Central de Asturias, Instituto Universitario de Oncologia del Principado de Asturias, Universidad de Oviedo, CIBERONC, Oviedo, Spain 2 Service of Molecular Oncology, Hospital Universitario Central de Asturias, Instituto Universitario de Oncologia del Principado de Asturias, Universidad de Oviedo, Oviedo, Spain 3 Service of Pathology, Hospital Universitario Central de Asturias, Instituto Universitario de Oncologia del Principado de Asturias, Universidad de Oviedo, Oviedo, Spain 4 Service of Endocrinology and Nutrition, Hospital Universitario Central de Asturias, Instituto Universitario de Oncologia del Principado de Asturias, Universidad de Oviedo, Oviedo, Spain 5 Otorhinolaryngology Service, Hospital Gregorio Maranon, Madrid, Spain 6 Stem Cell Niche Pathophysiology Group, Centro Nacional de Investigaciones Cardiovasculares, Madrid, Spain 7 Department of Cardiovascular Physiopahology, Instituto de Biomedicina de Sevilla (IBiS), Hospital Universitario Virgen del Rocio, CSIC, Universidad de Sevilla, Sevilla, Spain 8 Stem Cell Institute and Department of Haematology, University of Cambridge and National Health Service Blood and Transplant, Cambridge Biomedical Campus, UK * These authors have contributed equally to this work Correspondence to: Maria-Dolores Chiara, email: mdchiara.uo@uniovi.es Keywords: succinate dehydrogenase, hypoxia inducible factor, von hippel lindau, paragangliomas, miR-210 Received: July 02, 2016      Accepted: December 13, 2016      Published: December 27, 2016 ABSTRACT The hypoxia-inducible factor 1α (HIF-1α) and its microRNA target, miR-210, are candidate tumor-drivers of metabolic reprogramming in cancer. Neuroendocrine neoplasms such as paragangliomas (PGLs) are particularly appealing for understanding the cancer metabolic adjustments because of their associations with deregulations of metabolic enzymes, such as succinate dehydrogenase (SDH), and the von Hippel Lindau ( VHL ) gene involved in HIF-1α stabilization. However, the role of miR-210 in the pathogenesis of SDH -related tumors remains an unmet challenge. Herein is described an in vivo genetic analysis of the role of VHL , HIF1A and SDH on miR-210 by using knockout murine models, siRNA gene silencing, and analyses of human tumors. HIF-1α knockout abolished hypoxia-induced miR-210 expression in vivo but did not alter its constitutive expression in paraganglia. Normoxic miR-210 levels substantially increased by complete, but not partial, VHL silencing in paraganglia of knockout VHL -mice and by over-expression of p76del-mutated pVHL. Similarly, VHL -mutated PGLs, not those with decreased VHL -gene/mRNA dosage, over-expressed miR-210 and accumulate HIF-1α in most tumor cells. Ablation of SDH activity in SDHD -null cell lines or reduction of the SDHD or SDHB protein levels elicited by siRNA-induced gene silencing did not induce miR-210 whereas the presence of SDH mutations in PGLs and tumor-derived cell lines was associated with mild increase of miR-210 and the presence of a heterogeneous, HIF-1α-positive and HIF-1α-negative, tumor cell population. Thus, activation of HIF-1α is likely an early event in VHL-defective PGLs directly linked to VHL mutations, but it is a late event favored but not directly triggered by SDHx mutations. This combined analysis provides insights into the mechanisms of HIF-1α/miR-210 regulation in normal and tumor tissues potentially useful for understanding the pathogenesis of cancer and other diseases sharing similar underpinnings.