Abstract 2119: Acquired nintedanib resistance in FGFR1-driven small cell but not non-small cell lung cancer is mediated by ABCB1
Authors: Englinger Bernhard , Lötsch Daniela , Pirker Christine , van Schoonhoven Sushilla , Boidol Bernd , Lardeau Charles , Kubicek Stefan , Szabó Pal , Szakacs Gergely , Berger Walter 
Published: July 2016

Abstract
Lung cancer accounts for the highest number of cancer-related deaths worldwide. Patient outcome is dismal and approval of targeted compounds is yet restricted to non-small cell lung cancer (NSCLC) histology. In defined subgroups of NSCLC, but also of small cell lung cancer (SCLC), genetically amplified fibroblast growth factor receptor 1 (FGFR1) is an oncogenic driver and inhibition of the FGFR1 signaling axis exerts potent antitumor effects. The FGFR/PDGFR/VEGFR inhibitor (TKI) nintedanib has recently been approved for second-line treatment of lung adenocarcinoma (AC) and is also being investigated in clinical trials for the treatment of SCLC. Despite initial treatment success, tumor recurrence due to acquired drug resistance is anticipated. We therefore aimed at characterizing the molecular mechanisms underlying resistance development of FGFR1-driven lung cancer against nintedanib.
One SCLC line (DMS114) and two NSCLC squamous cell carcinoma (SCC) lines (NCI-H1703, NCI-H520) driven by FGFR1 based on gene amplification were selected for nintedanib resistance in vitro. Cytotoxicity was evaluated by MTT and FACS. Intracellular responses to drug exposure were analyzed by qPCR and Western Blot. To compare transcription levels of parental cells with their selected sublines, whole-genome gene expression array was performed. Cross-cytotoxicity profiles were determined by a large-scale anticancer compound screen. ATP-binding cassette (ABC) transporter activity was analyzed by calcein AM efflux- and ATPase assay, intracellular Nintedanib levels were determined by liquid chromatograpy-mass spectrometry (LC-MS).
Chronic exposure to the FGFR/PDGFR/VEGFR inhibitor nintedanib led to expression of the ABCB1 multidrug-resistance (MDR) efflux pump in the SCLC cell line DMS114 but not in the NSCLC SCC cell lines NCI-H1703 and NCI-H520. In the nintedanib-selected subline of DMS114 (DMS114/NIN), the FGFR1 signaling axis remained active. Insensitivity of DMS1114/NIN towards Nintedanib was mediated by efflux via ABCB1, revealing Nintedanib as a substrate for this efflux pump. Ponatinib, another non-ABCB1-substrate FGFR inhibitor, retained strong cytotoxic activity. Additionally, DMS114/NIN cells exerted profound and ABCB1-dependent collateral sensitivity against the MDR-selective lanthanum compound KP772.
ABCB1 needs to be considered as a factor underlying intrinsic and acquired nintedanib resistance. On one hand, in second-line therapy, chemotherapy-induced MDR might render tumors resistant to Nintedanib. On the other hand, in first-line treatment, high ABCB1 expression in cancer cells or the microvasculature e.g. in clear-cell renal carcinoma or CNS tumors might account for intrinsic Nintedanib resistance. Switching to MDR-selective anticancer compounds or to non-ABCB1-substrate small molecule TKIs in FGFR/PDGFR/VEGFR-driven tumors might be an option to circumvent nintedanib resistance.
Citation Format: Bernhard Englinger, Daniela Lötsch, Christine Pirker, Sushilla van Schoonhoven, Bernd Boidol, Charles Lardeau, Stefan Kubicek, Pal Szabó, Gergely Szakacs, Walter Berger. Acquired nintedanib resistance in FGFR1-driven small cell but not non-small cell lung cancer is mediated by ABCB1. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2119.