2534

FYN

FYN proto-oncogene, Src family tyrosine kinase;FYN;FYN proto-oncogene, Src family tyrosine kinase

FYN oncogene related to SRC, FGR, YES|OKT3-induced calcium influx regulator|c-syn protooncogene|proto-oncogene Syn|proto-oncogene c-Fyn|src-like kinase|src/yes-related novel|tyrosine kinase p59fyn(T)|tyrosine-protein kinase Fyn

6q21

protein-coding

We have previously shown that the integrin beta6 is neo-expressed in invasive oral squamous cell carcinoma (SCC) and is correlated with oral tumor progression. However, the mechanism by which the integrin beta6 promotes oral tumor progression is not well understood. The purpose of the present study was to determine whether integrin beta6 signaling activates Fyn and thus promotes oral squamous cell carcinoma progression. We analyzed the integrin beta6 signaling complex and investigated the function of these signaling molecules in oral SCC cells. We found that, upon ligation of the integrin beta6 with fibronectin, beta6 complexed with Fyn and activated it. The activation of Fyn recruited and activated focal adhesion kinase to this complex. This complex was necessary to activate Shc and to couple beta6 signaling to the Raf-ERK/MAPK pathway. This pathway transcriptionally activated the matrix metalloproteinase-3 gene and promoted oral SCC cell proliferation and experimental metastasis in vivo. These findings indicate that integrin beta6 signaling activates Fyn and thus promotes oral cancer progression.

BACKGROUND AND AIMS: Src family kinases have been suggested to be associated with the metastasis of tumors, but their related mechanisms remain unclear. The aims of the present study were to assess the possible mechanisms by which the inhibition of Fyn activation regulates pancreatic cancer metastasis. METHODS: We examined the expressions of Fyn in human pancreatic cancer tissues by immunohistochemistry and systematically investigated the relationship between Fyn expression and pancreatic cancer metastasis. A nude mouse xenograft model induced by BxPC3 cells with or without the inhibition of Fyn activation was used to explore the effect of the inhibition of Fyn on metastasis in vivo. Methyl thiazolyl tetrazolium and terminal deoxynucleotidyl transferase-labeling assays were used to examine the effect of the inhibition of Fyn on the cell proliferation of BxPC3 pancreatic cancer cells in vitro. Reverse transcription polymerase chain reaction and Western blot analysis were performed to explore the possible mechanism of Fyn-induced metastasis. RESULTS: We found that the upregulation of Fyn expression was correlated with human pancreatic cancer metastasis. In BxPC3 pancreatic cancer cells, the inhibition of Fyn activation by kinase-dead Fyn transfection decreased liver metastasis in nude mice. Further analyses showed that Fyn activity modulated pancreatic cell metastasis through the regulation of proliferation and apoptosis. CONCLUSIONS: Our results suggest a possible mechanism by which Fyn activity regulates cell proliferation and apoptosis that exerts an effect on pancreatic cancer metastasis.

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.