Downstream signalling and specific inhibition of c-MET/HGF pathway in small cell lung cancer: implications for tumour invasion

Abstract

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- α [S724], adducin- γ [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], p38 α -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.

MET signalling: principles and functions in development, organ regeneration and cancer

“…However, blocking a single network node is sufficient to perturb cellular responses, indicating that the targeted inhibition of a specific signalling pathway cannot be compensated for by other, still active, regulatory tiers. This is in line with the well-established observation that obstruction of individual MET-dependent pathways adversely affects tumour growth, survival and migration in various cancer cell types and under different experimental settings 37,48,50,56,57,58,70,71,72,76,139 . For example, the integrity of JNK-and p38-dependent signals is required for MET-stimulated proliferation and anchorage-independent growth in MET-transformed fibroblasts and melanoma cells 70,71,72 , and STAT3 signalling and NF-κB activity are necessary for MET-induced onset of leiomyosarcomas and for the survival of prostate cancer cells, respectively 48,76 .…”

4-Methylnitrosamino-1-3-pyridyl-1-butanone (NNK) promotes lung cancer cell survival by stimulating thromboxane A2 and its receptor

“…CREB is one such transcription factor (Sakamoto and Frank, 2009), and it is constitutively activated in both NSCLC and SCLC cells (Ma et al, 2007;Aggarwal et al, 2008). Additionally, CREB has been shown to be activated by NNK, TxA 2 or TxA 2 mimetic in lung cancer cells (Laag et al, 2006;Wei et al, 2007;Li and Tai, 2009).…”

MET in Lung Cancer: Biomarker Selection Based on Scientific Rationale

“…Early studies established that MET can be overexpressed or activated [as measured by phosphorylation of the catalytic domain as well as juxtamembrane (JM) domain], or the gene mutated (in the semaphorin or JM domains) and/or amplified in lung cancer. For instance, studies on small cell lung cancer (SCLC) cell lines established the multipurpose nature of MET/HGF pathway activation during tumor progression and invasion, which occurs via dysregulation of diverse biological functions such as proliferation and differentiation, transcriptional control, cell-cycle G 1 /S checkpoint, cytoskeletal functions, survival, motility, and apoptosis (23). Both epidermal growth factor receptor (EGFR) and MET are widely expressed on cancer cells, and both RTKs are implicated in these diverse signaling processes.…”