Improved diagnostics targeting c-MET in non-small cell lung cancer: expression, amplification and activation?

BACKGROUND: Several c-MET targeting inhibitory molecules have already shown promising results in the treatment of patients with Non-small Cell Lung Cancer (NSCLC). Combination of EGFR- and c-MET-specific molecules may overcome EGFR tyrosine kinase inhibitor (TKI) resistance. The aim of this study was to allow for the identification of patients who might benefit from TKI treatments targeting MET and to narrow in on the diagnostic assessment of MET. METHODS: 222 tumor tissues of patients with NSCLC were analyzed concerning c-MET expression and activation in terms of phosphorylation (Y1234/1235 and Y1349) using a microarray format employing immunohistochemistry (IHC). Furthermore, protein expression and MET activation was correlated with the amplification status by Fluorescence in Situ Hybridization (FISH). RESULTS: Correlation was observed between phosphorylation of c-MET at Y1234/1235 and Y1349 (spearman correlation coefficient rs = 0.41; p < 0.0001). No significant correlation was shown between MET expression and phosphorylation (p > 0.05). c-MET gene amplification was detected in eight of 214 patients (3.7%). No significant association was observed between c-MET amplification, c-MET protein expression and phosphorylation. CONCLUSION: Our data indicate, that neither expression of c-MET nor the gene amplification status might be the best way to select patients for MET targeting therapies, since no correlation with the activation status of MET was observed. We propose to take into account analyzing the phosphorylation status of MET by IHC to select patients for MET targeting therapies. Signaling of the receptor and the activation of downstream molecules might be more crucial for the benefit of therapeutics targeting MET receptor tyrosine kinases than expression levels alone.

Expression analysis of EML4 in normal lung tissue and non-small cell lung cancer (NSCLC) in the absence and presence of chemotherapeutics.

Despite considerable progress in the development of individualized targeted therapies of tumor diseases, identification of additional reliable target molecules is still mandatory. One of the most recent targets is microtubule-associated human EML4 generating a fusion-type oncogene with ALK demonstrating marked transforming activity in lung cancer. Since EML4 is a poorly characterized protein with regard to expression, function and regulation in human tissue, specimens of human tumor and tumor-free tissues obtained from patients with NSCLC were analyzed to determine the cellular localization. All tissue samples have been previously fixed with the novel HOPE-technique and paraffin embedded. Determination of both gene expression and protein levels of EML4 were performed using RT-PCR, in situ hybridization as well as immunohistochemistry, respectively. In human NSCLC tissue samples, possible regulation of EML4 transcription upon chemotherapy with combinations of most established cytotoxic drugs for NSCLC treatment was also studied employing the recently established ex vivo tissue culture model STST. In normal lung, both marked mRNA and protein levels of EML4 were localized in alveolar macrophages. In contrast, lung tumor tissues always showed consistent transcriptional expression in situ and by RT-PCR. Stimulation of NSCLC tissues with chemotherapeutics revealed heterogeneous effects on EML4 mRNA levels. Based on its expression patterns in both tumor-free lung and NSCLC tissues, human EML4 is likely to be closely associated with processes involved in local inflammation of the lung as well as with tumor behavior. Thus, our results suggest that EML4 may have the potential as a therapeutic target molecule in NSCLC chemotherapy.