Synergistic activity of combined FGFR and EGFR inhibition in non-small cell lung cancer
Authors: Fischer Hendrik, Ninon Taylor, Sigrid Allerstorfer, Michael Grusch, Gudrun Sonvilla, Klaus Holzmann, Ulrike Setinek, Leonilla Elbling, Heidelinde Cantonati, Bettina Grasl-Kraupp, Christine Gauglhofer, Brigitte Marian, Michael Micksche, Walter Berger
Journal: Cancer Research (2008)

141  Aim of this study was to evaluate the quality of the fibroblast growth factor (FGF)/FGF receptor (FGFR) system as a possible target for combination treatment of human non-small cell lung cancer (NSCLC).  Expression of multiple FGF molecules in NSCLC cell cultures (n=16) was assessed by RT-PCR. In vitro blockade of FGF-mediated pathways was done by small molecular inhibitors and dominant-negative (dn)FGFR1 IIIc-GFP (dnFGFR1) fusion protein introduced by adenoviral transduction. Effects of dnFGFR1 expression on cell growth, cell death (apoptosis), in vivo tumor growth and migration was assessed by trypanblue exclusion assay, DAPI staining, sc growth in SCID/Balb/c recipient mice and scratch assays, respectively. Cytostatic/cytotoxic and anti-migratory effects of small molecular inhibitors were investigated by MTT and transwell chamber assays.  Fibroblast growth factors (FGF) and their high affinity receptors (FGFR) represent a complexe cellular growth and survival system, which have also been associated with malignent growth for several epithelial solid tumors. Here we demonstrate that multiple FGF family members are co-expressed in human NSCLC cell lines of different histological origin. Accordingly we aimed to investigate the consequences of FGF/FGFR-mediated signal inhibition alone or in combination with agents blocking the epidermal growth factor receptor (EGFR) in NSCLC cells. Transient expression of the adenoviral dnFGFR1 construct prohibited FGF-induced phosphorylation of ERK-MAPK. Furthermore in the majority of NSCLC cell lines proliferation was inhibited and massive cell death, representing mainly apoptosis, was induced a few days after transduction. Accordingly, subcutaneous tumor formation in SCID mice was completely inhibited (VL-8) or significantly reduced (A549 and A427) by presence of dnFGFR1 in three NSCLC cell models tested. DnFGFR1-expressing tumors exhibited reduced size, enhanced necrosis and reduced tissue invasion as compared to GFP controls. This is in agreement with the reduction of NSCLC cell migratory potential after FGFR inhibition in vitro. Comparable to the dominant-negative receptor also small molecule FGFR inhibitors inhibited FGF induced phosphorylation of ERK-MAPK and S6 ribosomal protein and exhibited in more than 50% of the investigated cell lines distinct antimigratory as well as cytostatic and in some cases also cytotoxic effects. In addition simultaneous blockage of FGFR and EGFR signals with small molecule inhibitors and the respective dominant-negative receptor constructs generally exerted synergistic antiproliferative effects and further reduced MAPK and PI3K pathway activities.  Summarizing, we suggest that targeting the FGF/FGFR system should be considered as new tool for multimodality treatment of NSCLC especially in combination with EGFR inhibitors.