Fyn Is Downstream of the HGF/MET Signaling Axis and Affects Cellular Shape and Tropism in PC3 Cells

Purpose: Fyn is a member of the Src family of kinases that we have previously shown to be overexpressed in prostate cancer. This study defines the biological impact of Fyn inhibition in cancer using a PC3 prostate cancer model. Experimental Design: Fyn expression was suppressed in PC3 cells using an shRNA against Fyn (PC3/FYN-). Knockdown cells were characterized using standard growth curves and time-lapse video microscopy of wound assays and Dunn Chamber assays. Tissue microarray analysis was used to verify the physiologic relevance of the HGF/MET axis in human samples. Flank injections of nude mice were performed to assess in vivo growth characteristics. Results: HGF was found to be sufficient to drive Fyn-mediated events. Compared to control transductants (PC3/Ctrl), PC3/FYN-showed a 21% decrease in growth at 4 days (P=0.05). PC3/FYN-cells were 34% longer than control cells (P=0.018) with 50% increase in overall surface area (P < 0.001). Furthermore, when placed in a gradient of HGF, PC3/FYN-cells showed impaired directed chemotaxis down an HGF gradient in comparison to PC3/Ctrl (P=0.001) despite a 41% increase in cellular movement speed. In vivo studies showed 66% difference of PC3/FYN-cell growth at 8 weeks using bidimensional measurements (P=0.002). Conclusions: Fyn plays an important role in prostate cancer biology by facilitating cellular growth and by regulating directed chemotaxis-a key component of metastasis. This finding bears particular translational importance when studying the effect of Fyn inhibition in human subjects. Clin Cancer Res; 17(10); 3112-22. (C) 2011 AACR.