The "angiogenic switch" during tumor progression is increasingly recognized as a milestone event in tumorigenesis, although the surprising prometastatic effect of antiangiogenic therapies has recently shaken the scientific community. Tumor hypoxia has been singled out as a possible responsible factor in this prometastatic effect, although the molecular pathways are completely unknown. We report herein that human melanoma cells respond to hypoxia through a deregulation of the mitochondrial release of reactive oxygen species (ROS) by the electron transfer chain complex III. These ROS are mandatory to stabilize hypoxia-inducible factor-1α (HIF-1α), the master transcriptional regulator of the hypoxic response. We found that melanoma cells sense hypoxia-enhancing expression/activation of the Met proto-oncogene, which drives a motogenic escape program. Silencing analyses revealed a definite hierarchy of this process, in which mitochondrial ROS drive HIF-1α stabilization, which in turn activates the Met proto-oncogene. This pathway elicits a clear metastatic program of melanoma cells, enhancing spreading on extracellular matrix, motility, and invasion of 3D matrices, as well as growth of metastatic colonies and the ability to form capillary-like structures by vasculogenic mimicry. Both pharmacological and genetic interference with mitochondrial ROS delivery or Met expression block the hypoxia-driven metastatic program. Hence, we propose that hypoxia-driven ROS act as a primary driving force to elicit an invasive program exploited by aggressive melanoma cells to escape from a hypoxic hostile environment.

HIF-1α stabilization by mitochondrial ROS promotes Met-dependent invasive growth and vasculogenic mimicry in melanoma cells.

MIGLIORE, Cristina;GIORDANO, Silvia;
2011

Abstract

The "angiogenic switch" during tumor progression is increasingly recognized as a milestone event in tumorigenesis, although the surprising prometastatic effect of antiangiogenic therapies has recently shaken the scientific community. Tumor hypoxia has been singled out as a possible responsible factor in this prometastatic effect, although the molecular pathways are completely unknown. We report herein that human melanoma cells respond to hypoxia through a deregulation of the mitochondrial release of reactive oxygen species (ROS) by the electron transfer chain complex III. These ROS are mandatory to stabilize hypoxia-inducible factor-1α (HIF-1α), the master transcriptional regulator of the hypoxic response. We found that melanoma cells sense hypoxia-enhancing expression/activation of the Met proto-oncogene, which drives a motogenic escape program. Silencing analyses revealed a definite hierarchy of this process, in which mitochondrial ROS drive HIF-1α stabilization, which in turn activates the Met proto-oncogene. This pathway elicits a clear metastatic program of melanoma cells, enhancing spreading on extracellular matrix, motility, and invasion of 3D matrices, as well as growth of metastatic colonies and the ability to form capillary-like structures by vasculogenic mimicry. Both pharmacological and genetic interference with mitochondrial ROS delivery or Met expression block the hypoxia-driven metastatic program. Hence, we propose that hypoxia-driven ROS act as a primary driving force to elicit an invasive program exploited by aggressive melanoma cells to escape from a hypoxic hostile environment.
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http://www.sciencedirect.com/science/article/pii/S0891584911003583
Reactive oxygen species; Melanoma; Hypoxia; Met; Invasiveness; Free radicals
Comito G;Calvani M;Giannoni E;Bianchini F;Calorini L;Torre E;Migliore C;Giordano S;Chiarugi P
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2318/113439
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