Deregulated hepatocyte growth factor (HGF)/c-MET axis has been correlated with poor clinical outcome and drug resistance in many human cancers. Identification of novel regulatory mechanisms influencing HGF/c-MET signaling may therefore be necessary to develop more effective cancer therapies. In our study, we show that multiple human cancer tissues and cells express filamin A (FLNA), a large cytoskeletal actin-binding protein, and expression of c-MET is significantly reduced in human tumor cells deficient for FLNA. The FLNA-deficient tumor cells exhibited poor migrative and invasive ability in response to HGF. On the other hand, the anchorage-dependent and independent tumor cell proliferation was not altered by HGF. The FLNA-deficiency specifically attenuated the activation of the c-MET downstream signaling molecule AKT in response to HGF stimulation. Furthermore, FLNA enhanced c-MET promoter activity by its binding to SMAD2. The impact of FLNA deficiency on c-MET expression and HGF-mediated cell migration in human tumor cells was confirmed in primary mouse embryonic fibroblasts deficient for Flna. These data suggest that FLNA is one of the important regulators of c-MET signaling and HGF-induced tumor cell migration.
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