Abstract 376: Increased HGF is associated with resistance to VEGFR tyrosine kinase inhibitors (TKIs) in non-small cell lung cancer (NSCLC)

Abstract

Emergence of therapeutic resistance to angiogenesis inhibitors, the mechanisms of which are poorly understood, remains a major obstacle in treatment of NSCLC patients. Previously we reported that mechanisms governing resistance to anti-angiogenic therapy may involve both tumor and stromal cells in the tumor microenvironment. In this study we investigated potential mechanisms of resistance to the multi-tyrosine kinase inhibitors cediranib (AZD2171, Recentin®) and vandetanib (ZD6474, Zactima®) using NSCLC xenografts treated either for 2 weeks (sensitive tumors) or until resistance occurred. Quantification of TUNEL+ staining using laser scanning cytometry (LSC) showed increased apoptosis in H1975 xenografts sensitive to cediranib (p<0.01) and vandetanib (p<0.05) when compared with controls, whereas no changes were noticed at time of resistance. Microvessel density (MVD) was significantly increased in resistant H1975 xenografts compared with controls (p<0.05) and sensitive tumors (p<0.01), whereas in A549 model, vandetanib-resistance was associated with an angiogenic independent phenotype. To investigate stromal mechanisms of Vascular Endothelial Growth Factor Receptor (VEGFR) TKI resistance, we characterized the stromal angiogenic gene expression profiles of H1975 sensitive and resistant tumors using a mouse-specific gene expression array (mouseWG-6 v2 Expression BeadChip, Illumina®). Differentially modulated genes were selected based on a p<0.005 of the univariate t-test and at least a 1.5 fold-change in expression and cross-referenced to defined list(s) of angiogenesis-related genes. Stromal Hgf (hepatocyte growth factor) was up-regulated in VEGFR TKI-resistant xenografts compared to sensitive tumors. Hgf up-regulation was confirmed at the protein level using immunofluorescent staining and confocal microscopy. HGF protein levels were strongly decreased after 2 weeks of treatment with cediranib and vandetanib (p<0.01), whereas a significant increase in HGF was observed in resistant xenografts (p<0.01). To assess whether HGF upregulation contributes to tumor resistance to TKIs, we implanted HGF-overexpressing and vector control HCC827 NSCLC cells into nude mice. In HCC827-vector control xenografts, cediranib inhibited tumor growth by 93%, whereas a 60% of growth inhibition was observed in HGF-overexpressing tumors. These data agree favorably with our previous analysis of clinical specimens from patients with stage IIIB/IV NSCLC that identified HGF as a predictive marker of resistance to vandetanib treatment alone when compared to chemotherapy or the combination of chemotherapy and vandetanib (p=0.033). Our results suggest that HGF up-regulation may resistance to VEGFR pathway inhibition and that the HGF/MET axis may represent a crucial target for NSCLCs that are resistant to anti-angiogenic therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 376.