Autocrine stimulation of clear-cell renal carcinoma cell migration in hypoxia via HIF-independent suppression of thrombospondin-1

Thrombospondin-1 is a matricellular protein with potent antitumour activities, the levels of which determine the fate of many different tumours, including renal carcinomas. However, the factors that regulate this protein remain unclear. In renal carcinomas, hypoxic conditions enhance the expression of angiogenic factors that help adapt tumour cells to their hostile environment. Therefore, we hypothesized that anti-angiogenic factors should correspondingly be dampened. Indeed, we found that hypoxia decreased the thrombospondin-1 protein in several clear cell renal carcinoma cell lines (ccRCC), although no transcriptional regulation was observed. Furthermore, we proved that hypoxia stimulates multiple signals that independently contribute to diminish thrombospondin-1 in ccRCC, which include a decrease in the activity of oxygen-dependent prolylhydroxylases (PHDs) and activation of the PI3K/Akt signalling pathway. In addition, thrombospondin-1 regulation in hypoxia proved to be important for ccRCC cell migration and invasionThis work was supported by the Ministerio de Ciencia e Innovacion (MCINN) SAF2009-11113 and METOXIA, a Collaborative Project under the 7th Research Framework Programme of the European Union FP7-HEALTH-2007B (ref. HEALTH-F2-2009-222741

Induction of the mitochondrial NDUFA4L2 protein by HIF-1α decreases oxygen consumption by inhibiting complex i activity

The fine regulation of mitochondrial function has proved to be an essential metabolic adaptation to fluctuations in oxygen availability. During hypoxia, cells activate an anaerobic switch that favors glycolysis and attenuates the mitochondrial activity. This switch involves the hypoxia-inducible transcription factor-1 (HIF-1). We have identified a HIF-1 target gene, the mitochondrial NDUFA4L2 (NADH dehydrogenase [ubiquinone] 1 alpha subcomplex, 4-like 2). Our results, obtained employing NDUFA4L2-silenced cells and NDUFA4L2 knockout murine embryonic fibroblasts, indicate that hypoxia-induced NDUFA4L2 attenuates mitochondrial oxygen consumption involving inhibition of Complex I activity, which limits the intracellular ROS production under low-oxygen conditions. Thus, reducing mitochondrial Complex I activity via NDUFA4L2 appears to be an essential element in the mitochondrial reprogramming induced by HIF-1This work was supported by Ministerio de Ciencia e Innovación (SAF 2007-06592, SAF2010-14851), Comunidad Autónoma de Madrid (SAL 2006/ 0311), Metoxia Project-Health (F2 2009-222741), and Recava Network (RD 06/0014/0031) to M.O.L.; PS09/00101 and CP07/00143 to A.M.-R.; PI060701, PS09/00116, and CP08/00204 to S.C.; BFU2008-03407/BMC to J.A.; SAF2009-08007 to J.A.E.; and CSD2007-00020 to A.M.-R. and J.A.E. The CNIC is supported by the Instituto de Salud Carlos III-MICINN and the Pro-CNIC Foundation. We are grateful to Mike Murphy (Mitochondrial Biology Unit, MRC, Cambridge, UK) for the gift of MitoQ. We also thank Stephen Y. Chan and Joseph Loscalzo (Harvard Medical School, Boston, MA) for providing us ISCU expression vector

VHL promotes immune response against renal cell carcinoma via NF-κB–dependent regulation of VCAM-1

Vascular cell adhesion molecule 1 (VCAM-1) is an adhesion molecule assigned to the activated endothelium mediating immune cells adhesion and extravasation. However, its expression in renal carcinomas inversely correlates with tumor malignancy. Our experiments in clear cell renal cell carcinoma (ccRCC) cell lines demonstrated that von Hippel Lindau (VHL) loss, hypoxia, or PHD (for prolyl hydroxylase domain–containing proteins) inactivation decreased VCAM-1 levels through a transcriptional mechanism that was independent of the hypoxia-inducible factor and dependent on the nuclear factor κB signaling pathway. Conversely, VHL expression leads to high VCAM-1 levels in ccRCC, which in turn leads to better outcomes, possibly by favoring antitumor immunity through VCAM-1 interaction with the α4β1 integrin expressed in immune cells. Remarkably, in ccRCC human samples with VHL nonmissense mutations, we observed a negative correlation between VCAM-1 levels and ccRCC stage, microvascular invasion, and symptom presentation, pointing out the clinical value of VCAM-1 levels as a marker of ccRCC progression.This work was supported by grants from the Instituto de Salud Carlos III (co-funded by the European Union and Fondo Europeo de Desarrollo Regional; grants PI16/02166 and PIE13/00041), a grant from Red Cardiovascular (RD12/0042/0065 to M.J. Calzada), and a grant from Ministerio de Economía y competitividad (SAF2015-64215R to R. Sánchez-Prieto).Peer reviewe