Downstream signalling and specific inhibition of c-MET/HGF pathway in small cell lung cancer: implications for tumour invasion.
The c-MET receptor can be overexpressed, amplified, or mutated in solid tumours including small cell lung cancer (SCLC). In c-MET-overexpressing SCLC cell line NCI-H69, hepatocyte growth factor (HGF) dramatically induced c-MET phosphorylation at phosphoepitopes pY1230/1234/1235 (catalytic tyrosine kinase), pY1003 (juxtamembrane), and also of paxillin at pY31 (CRKL-binding site). We utilised a global proteomics phosphoantibody array approach to identify further c-MET/HGF signal transduction intermediates in SCLC. Strong HGF induction of specific phosphorylation sites in phosphoproteins involved in c-MET/HGF signal transduction was detected, namely adducin-alpha [S724], adducin-gamma [S662], CREB [S133], ERK1 [T185/Y187], ERK1/2 [T202/Y204], ERK2 [T185/Y187], MAPKK (MEK) 1/2 [S221/S225], MAPKK (MEK) 3/6 [S189/S207], RB [S612], RB1 [S780], JNK [T183/Y185], STAT3 [S727], focal adhesion kinase (FAK) [Y576/S722/S910], p38alpha-MAPK [T180/Y182], and AKT1[S473] and [T308]. Conversely, inhibition of phosphorylation by HGF in protein kinase C (PKC), protein kinase R (PKR), and also CDK1 was identified. Phosphoantibody-based immunohistochemical analysis of SCLC tumour tissue and microarray established the role of c-MET in SCLC biology. This supports a role of c-MET activation in tumour invasive front in the tumour progression and invasion involving FAK and AKT downstream. The c-MET serves as an attractive therapeutic target in SCLC, as shown through small interfering RNA (siRNA) and selective prototype c-MET inhibitor SU11274, inhibiting the phosphorylation of c-MET itself and its downstream molecules such as AKT, S6 kinase, and ERK1/2. Investigation of mechanisms of invasion and, ultimately, metastasis in SCLC would be very useful with these signal transduction molecules.
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Division of Hematology/Oncology, Department of Medicine, University Hospitals of Case Medical Center and Ireland Cancer Center, Case Western Reserve University, Case Comprehensive Cancer Center, Cleveland, OH 44106, USA.
Tretiakova
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Nallasura
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Jagadeeswaran
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Husain
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Salgia
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D018288:Carcinoma, Small Cell / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D017228:Hepatocyte Growth Factor / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology*; D009361:Neoplasm Invasiveness; D019859:Proto-Oncogene Proteins c-met / Q000037:antagonists & inhibitors* / Q000378:metabolism; D034741:RNA, Small Interfering; D015398:Signal Transduction
D034741:RNA, Small Interfering; D017228:Hepatocyte Growth Factor; D019859:Proto-Oncogene Proteins c-met