Activation of the epidermal growth factor signalling pathway by tissue plasminogen activator in pancreas cancer cells.
BACKGROUND
Tissue plasminogen activator (tPA) is the major activator of plasminogen in plasma. This serine protease is overexpressed by exocrine pancreas tumour cells, where it promotes tumour cell proliferation, growth, and invasion. Here we have explored the signalling pathways used by tPA to activate the proliferation of pancreatic cancer cells.


METHODS
Transcriptional profiling on cDNA micro arrays was used to analyse the pattern of gene expression in response to tPA compared to the response to epidermal growth factor (EGF) and platelet derived growth factor (PDGF). Results were confirmed using different biochemical assays in which specific kinase inhibitors or RNA interference were used.


RESULTS
Transcriptional profiling showed that tPA modulates the expression of a set of genes commonly regulated by EGF, but distinct from the major set of genes modulated by PDGF. This suggested that tPA and EGF share common signalling pathways, a conclusion supported by further experimental evidence. Firstly, we found that tPA induced a rapid and transient phosphorylation of the EGFR. Secondly, specific EGFR kinase inhibitors, but not PDGFR kinase inhibitors, abolished the tPA induced phosphorylation of the ERK1/2 kinases and cell proliferation. The mitogenic activity of tPA was also inhibited by siRNA depletion of EGFR, thus confirming the involvement of this receptor in tPA triggered signalling. Thirdly, we show that the signalling and mitogenic effects of tPA require its proteolytic activity, the activity of the metalloprotease-9 and active hb-EGF.


CONCLUSIONS
Our results suggest that tPA induces proliferation by triggering a proteolytic cascade that sequentially activates plasmin, metalloprotease-9 (MMP-9) and hb-EGF. These events are required to activate the EGFR signalling pathway and cell proliferation.
Hurtado
Mariano
M
Unitat de Recerca Biomédica, Institut de Recerca, Hospital Vall d'Hebrón, Pg Vall d'Hebrón 119-129, Barcelona 08035, Spain.
Lozano
Juan José
JJ
Castellanos
Elisabeth
E
López-Fernández
Luis A
LA
Harshman
Keith
K
Martínez-A
Carlos
C
Ortiz
Angel R
AR
Thomson
Timothy M
TM
Paciucci
Rosanna
R
D002455:Cell Division / Q000187:drug effects; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000378:metabolism*; D066246:ErbB Receptors / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005341:Fibrinolysin / Q000378:metabolism; D005343:Fibrinolytic Agents / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D045726:Metalloproteases / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics; D010959:Tissue Plasminogen Activator / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000235:genetics
D005343:Fibrinolytic Agents; C587883:HBEGF protein, human; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D010982:Platelet-Derived Growth Factor; D034741:RNA, Small Interfering; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases; D045726:Metalloproteases; D010959:Tissue Plasminogen Activator; D005341:Fibrinolysin; D020780:Matrix Metalloproteinase 9