Activated c-Met[pY1003]: A potential marker of intrinsic resistance and therapy target to restore sensitivity to gefitinib

Abstract

7624 Background: Epidermal growth factor receptor tyrosine-kinase inhibitors (EGFR-TKIs) show anti-tumor activity in only 10% of Caucasian non-small cell lung cancer (NSCLC) patients. Aim of this study was to evaluate several biological parameters potentially related to EGFR, including c-Met activation, as potential markers of intrinsic resistance to EGFR-TKIs in NSCLC. Methods: P-Akt, p-Erk, c-Src, E-Cadherin, c-Met[pY1003] and c-Met[pY1230/1234/1235] status was immunohistochemically determined on a tissue micro-array of tumor samples from 51 NSCLC patients treated with gefitinib. EGFR, k-ras, and c-Met mutation analysis was also carried out. A panel of NSCLC cell lines expressing c-Met[pY1003] were treated with gefitinib (0.01–100μ M) alone or in combination with hepatocyte growth factor (40 ng/ml) and the c-Met-agonistic antibody DN-30 (80 μg/ml) for 72 hours in 0.5% FCS medium. Drug interaction between gefitinib and DN-30 was assessed, at a non-constant concentration ratio, using the combination index (CI) method. Results: There was no association between p-Erk, c-Src, E-Cadherin, c-Met[pY1230/1234/1235], and k-ras status and response or survival. EGFR exon 19 deletion and p-Akt nuclear staining were significantly associated with response (P<0.0001; Fisher's exact test) and longer time to progression (TTP) (P=0.007; log-rank test), respectively. High c-Met[pY1003] membrane staining was significantly associated with progressive disease (P=0.019; Fisher's exact test) and shorter TTP (P=0.0416; log-rank test), but not with survival. Multivariate analysis confirmed a significant relationship between c-Met[pY1003] and increased risk of disease progression (HR=2.464, 95% CI 1.293–4.696, P=0.006). No c-Met mutations were found. In vitro, the combination with DN- 30 synergistically (CI<1) enhanced gefitinib-induced growth inhibition in all c-Met[pY1003]-expressing NSCLC cells studied (H460, SW1573, A549 and H292). Conclusions: Activation of c-MET may be a biological marker of intrinsic resistance to gefitinib in NSCLC patients, and combined inhibition of c-Met and EGFR may be a suitable therapeutic approach in patients with activated c-Met[pY1003] tumors. No significant financial relationships to disclose.