EphA2 receptor is a key player in the metastatic onset of Ewing sarcoma

Ewing sarcoma (ES) is the second most common bone malignancy affecting children and young adults with poor prognosis due to high metastasis incidence. Our group previously described that EphA2, a tyrosine kinase receptor, promotes angiogenesis in ES cells via ligand-dependent signaling. EphA2 ligand-independent activity, controlled upon phosphorylation at S897 (p-EphA2S897), has been linked to metastasis in several malignancies. Here, we stablish a correlation between ES cells aggressiveness and p-EphA2S897. Moreover, stable overexpression of EphA2 in low EphA2 expression ES cells enhanced proliferation and migration, but not a nonphosphorylable mutant (S987A). Consistently, silencing of EphA2 reduced tumorigenicity, migration and invasion in vitro, and lung metastasis incidence in experimental and spontaneous metastasis assays in vivo. A gene expression microarray revealed the implication of EphA2 in cell signaling, cellular movement and survival. Altogether, our results suggest that p-EphA2S897 correlates with aggressiveness in ES, so blocking its function may be a promising treatment. 9 samples were analyzed: A673 parental or transfected with control shRNA (n=2); TC252 parental or transfected with control shRNA (n=2); A673 transfected with EphA2 shRNA (n=2), TC252 transfected with EphA2 shRNA (n=3),