Expression profiling identifies the cytoskeletal organizer ezrin and the developmental homeoprotein Six-1 as key metastatic regulators.

Patients presenting with metastatic rhabdomyosarcoma (RMS), the most common soft-tissue sarcoma in children, have a very poor clinical prognosis. This is due, in large part, to our rudimentary knowledge of the molecular events that dictate metastatic potential. We used cDNA microarray analysis of RMS cell lines, derived from Ink4a/Arf-deficient mice transgenic for hepatocyte growth factor/scatter factor (HGF/SF), to identify a set of genes whose expression was significantly different between highly and poorly metastatic cells. Subsequent in vivo functional studies revealed that the actin filament-plasma membrane linker ezrin (encoded by Vil2) and the homeodomain-containing transcription factor Six-1 (sine oculis-related homeobox-1 homolog) had essential roles in determining the metastatic fate of RMS cells. VIL2 and SIX1 expression was enhanced in human RMS tissue, significantly correlating with clinical stage. The identification of ezrin and Six-1 as critical regulators of metastasis in RMS provides new mechanistic and therapeutic insights into this pediatric cancer.