Hypoxia-Induced WSB1 Promotes the Metastatic Potential of Osteosarcoma Cells

Intratumoral hypoxia occurs in many solid tumors, where it is associated with the development of metastatic character. However, the connections between these phenomena are not fully understood. In this study, we define an integrative role for the E3 ubiquitin ligase subunit WSB1. In primary osteosarcomas, increased levels of WSB1 correlated with pulmonary metastatic potential. RNAi-mediated attenuation of WSB1 or disruption of its E3 ligase activity potently suppressed tumor metastasis. Quantitative proteomic and functional analyses revealed that WSB1 ubiquitylates the Rho-binding protein RhoGDI2 and promotes its proteasomal degradation, thereby activating Rac1 to stimulate tumor cell motility and invasion. Our findings show how WSB1 regulates key steps of the metastatic cascade in hypoxia-driven osteosarcoma, and they highlight a candidate therapeutic target to potentially improve the survival of patients with metastatic disease. (C) 2015 AACR.