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.

[A reduced TKI dosage is not associated with loss of activity in EGFR mutated NSCLC patients]. / Reduzierte Dosis von TKI führt nicht zu Wirkungsverlust bei Patienten mit aktivierender EGFR-Mutation.

BACKGROUND: Patients treated with anti-EGFR tyrosine kinase inhibitors (TKI) may receive dose reduction due to toxicity; however, the impact on treatment efficacy and patient outcome remains unknown. PATIENTS AND METHODS: Patients with stage IV NSCLC harbouring EGFR mutations and treated at our institution were retrospectively analyzed for treatment with TKI in 2012 or later. RESULTS: Thirty patients with EGFR mutated adenocarcinoma were identified meeting the inclusion criteria. Eleven patients received cytotoxic therapy as first line treatment yielding in a response rate of 36 %. All patients were treated with TKI as first or second-line therapy which resulted in disease stabilization (23 %) or response (77 %) in all patients. The median progression-free survival was 21.4 months with 21 patients still on treatment with TKI. For 7 patients, the dose of TKI treatment had to be reduced due to co-morbidities (n = 2) or skin toxicity (rash ≥ grade 3; n = 5). These patients demonstrated a similar response and outcome as compared to patients receiving full dose TKI treatment. CONCLUSION: Patients with EGFR mutated NSCLC and the need for TKI dose reduction seem to benefit in a similar manner from TKI therapy.

Activation of CD95L fusion protein prodrugs by tumor-associated proteases.

To achieve tumor cell-restricted activation of CD95, we developed a CD95L fusion protein format, in which CD95L activity is only unmasked upon antibody-mediated binding to tumor cells and subsequent processing by tumor-associated proteases, such as matrix metalloproteases (MMPs) and urokinase plasminogen activator (uPA). On target-negative, but MMP- and uPA-expressing HT1080 tumor cells, the CD95L prodrugs were virtually inactive. On target antigen-expressing HT1080 cells, however, the CD95L prodrugs showed an apoptotic activity comparable to soluble CD95L artificially activated by crosslinking. CD95 activation by the CD95L prodrugs was preceded by prodrug processing. Apoptosis was blocked by inhibitors of MMPs or uPA and by neutralizing antibodies recognizing the targeted cell surface antigen or the CD95L moiety of the prodrugs. In a xenotransplantation tumor model, local application of the prodrug reduced the growth of target antigen-expressing, but not antigen-negative tumor cells, verifying targeted CD95L prodrug activation in vivo.