Stromal and antitumor effects of BIBF 1120 (nintedanib) in a preclinical lung cancer model.

Abstract

e13563 Background: BIBF 1120 is an angiogenic receptor tyrosine kinase inhibitor that potently inhibits VEGFR, PDGFR and FGFR kinase activity in in vitro enzymatic assays. This study investigated the effect and mechanism of BIBF 1120, in vitro and in vivo, as a single agent and in combination with chemotherapy in preclinical models of lung cancer. Methods: Anti-tumor effects of BIBF 1120 in vitro were assessed using cell proliferation assays on five lung cancer lines (A549, Calu-3, Calu-6, H1993, H1703) with BIBF 1120 as a single agent and in combination with gemcitabine and cisplatin. To demonstrate anti-tumor activity in vivo, NOD/SCID mice bearing subcutaneous A549 grafts were treated daily with BIBF 1120 or BIBF 1120 plus chemotherapy. Perfusion studies were conducted using labeled dextrans. Ex vivo tumor tissues were assessed for architecture, microvessel density, pericyte coverage, proliferation, and apoptosis. Results: In vitro, BIBF 1120 did not show anti-proliferative effects at pharmacologically achievable concentrations (IC50>20μM) as a single agent; nor did it sensitize tumor cells to chemotherapy. However, BIBF 1120 inhibited primary tumor growth as a single agent and in combination therapy in subcutaneous endpoint studies with A549 xenografts. There was no significant difference in tumor architecture between BIBF 1120 and control-treated animals. Microvessel density (CD31,endomucin) and pericyte-covered vessels (NG2) were significantly decreased in BIBF 1120-treated animals compared to the control and chemotherapy only groups. Proliferation (phospho-histone 3) was decreased and apoptosis (cleaved caspase 3) was increased in BIBF 1120-treated animals compared to the control and chemotherapy only groups. Finally, BIBF 1120 significantly decreased perfusion in A549 xenografts. Conclusions: BIBF 1120 demonstrated potent anti-tumor and anti-angiogenic activity in a preclinical model of lung cancer. Because A549 was previously demonstrated to be an anti-VEGFR therapy resistant cell line, this study highlights the importance of FGFR and PDGFR pathways in the treatment of lung cancer.