Characterisation of fibronectin-mediated FAK signalling pathways in lung cancer cell migration and invasion.
BACKGROUND
Focal adhesion kinase (FAK) is overexpressed in a variety of cancers, such as breast, colon, prostate, ovary, and lung cancers. However, the mechanism by which extracellular matrix fibronectin stimulates lung cancer cell migration and invasion through FAK remains to be investigated.


METHODS
The signalling pathways in fibronectin-mediated lung cancer cell migration and invasion were examined using western blotting. The metastasis function was detected by wound healing, migration and invasion assays. Further, RNA interference and kinase inhibitors were also used to study the downstream signals.


RESULTS
In this study, we examined the FAK signalling pathways in relation to calpain-2 and RhoA in fibronectin-mediated lung cancer cell migration and invasion. We found that A549 lung epithelial cells stimulated by fibronectin showed increased phosphorylation of FAK and its downstream targets, Src, ERK1/2, phosphatidylinositol 3'-kinase (PI3K), and Akt. Consistent with this observation, depletion of FAK by siRNA resulted in the inhibition of Src, ERK1/2, PI3K, and Akt activity. In addition, the Src inhibitor, PP2, blocked the phosphorylation of FAK, ERK1/2, PI3K, and Akt. Conversely, inhibition of MEK1/2 using PD98059 reduced the expression of matrix metalloproteinase-9 (MMP9) and calpain-2. The PI3K inhibitor, LY294002, further blocked the expression of MMP9 and RhoA. Inhibition of both MEK1/2 and PI3K caused reduced cell migration and invasion.


CONCLUSIONS
Our data suggest that fibronectin-mediated activation of FAK that leads to lung cancer metastasis could occur through ERK or PI3K/Akt regulation of MMP9/calpain-2 or MMP9/RhoA activity, respectively.
Meng
X N
XN
Laboratory of Medical Genetics, Department of Biology, Harbin Medical University, Harbin 150086, China.
Jin
Y
Y
Yu
Y
Y
Bai
J
J
Liu
G Y
GY
Zhu
J
J
Zhao
Y Z
YZ
Wang
Z
Z
Chen
F
F
Lee
K-Y
KY
Fu
S B
SB
D000230:Adenocarcinoma / Q000097:blood / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D002154:Calpain / Q000378:metabolism; D002465:Cell Movement / Q000502:physiology; D004789:Enzyme Activation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism*; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism*; D006801:Humans; D008175:Lung Neoplasms / Q000097:blood / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D009361:Neoplasm Invasiveness; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
D005353:Fibronectins; C066737:RHOA protein, human; D019869:Phosphatidylinositol 3-Kinases; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D002154:Calpain; C569870:CAPN2 protein, human; D020780:Matrix Metalloproteinase 9; D020742:rhoA GTP-Binding Protein