Transcriptomics and Transposon Mutagenesis Identify Multiple Mechanisms of Resistance to the FGFR Inhibitor AZD4547.

Sjors M Kas,Eva Schut,Lorenzo Bombardelli,Renske De Korte-Grimmerink,Sunny Mahakena,Jos Jonkers,Paul D Smith,Julian R De Ruiter,Anne Paulien Drenth,Koen Schipper,Christopher Phillips,Koen Van De Wetering,Anton Berns,Sjoerd Klarenbeek,Ellen Wientjens,Lodewyk F.A Wessels

doi:10.1158/0008-5472.can-18-0757

Abstract

In human cancers, FGFR signaling is frequently hyperactivated by deregulation of FGF ligands or by activating mutations in the FGFR receptors such as gene amplifications, point mutations, and gene fusions. As such, FGFR inhibitors are considered an attractive therapeutic strategy for patients with mutations in FGFR family members. We previously identified Fgfr2 as a key driver of invasive lobular carcinoma (ILC) in an in vivo insertional mutagenesis screen using the Sleeping Beauty transposon system. Here we explore whether these FGFR-driven ILCs are sensitive to the FGFR inhibitor AZD4547 and use transposon mutagenesis in these tumors to identify potential mechanisms of resistance to therapy. Combined with RNA sequencing-based analyses of AZD4547-resistant tumors, our in vivo approach identified several known and novel potential resistance mechanisms to FGFR inhibition, most of which converged on reactivation of the canonical MAPK-ERK signaling cascade. Observed resistance mechanisms included mutations in the tyrosine kinase domain of FGFR2, overexpression of MET, inactivation of RASA1, and activation of the drug-efflux transporter ABCG2. ABCG2 and RASA1 were identified only from de novo transposon insertions acquired during AZD4547 treatment, demonstrating that insertional mutagenesis in mice is an effective tool for identifying potential mechanisms of resistance to targeted cancer therapies.Significance: These findings demonstrate that a combined approach of transcriptomics and insertional mutagenesis in vivo is an effective method for identifying potential targets to overcome resistance to therapy in the clinic. Cancer Res; 78(19); 5668-79. ©2018 AACR.

Highlights

FGFRs are members of the receptor tyrosine kinase (RTK) family that bind to different FGF family members and areNote: Supplementary data for this article are available at Cancer Research Online.S.M
We identified Fgfr2 as a key driver of invasive lobular breast carcinoma (ILC) using a Sleeping Beauty (SB)-based transposon insertional mutagenesis screen in mice [19]
Activation of Fgfr2 induces mouse ILCs (mILC) formation In a previous study, we performed a SB insertional mutagenesis screen in mice with mammary-specific inactivation of Cdh1 to identify genes and pathways driving the development of invasive lobular carcinoma (ILC) [19]

Summary

Introduction

FGFRs are members of the receptor tyrosine kinase (RTK) family that bind to different FGF family members and areNote: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/).S.M. FGFRs are members of the receptor tyrosine kinase (RTK) family that bind to different FGF family members and are. Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/). Upstream of both the MAPK–ERK and PI3K–AKT signaling pathways. FGFRs dimerize upon FGF ligand binding, which results in cross-phosphorylation of the receptors cognate kinase domains and allows the binding of the adaptor protein FGFR substrate 2a (FRS2a), a key transducer of FGFR signaling [1]. Subsequent phosphorylation of FRS2a induces the recruitment of growth factor receptor-bound 2 (GRB2) and son of sevenless (SOS), resulting in activation of the MAPK–ERK signaling pathway. Activation of the PI3K–AKT signaling pathway is mediated by interactions between the FRS2a complex and GRB2associated binding protein 1 Activation of the PI3K–AKT signaling pathway is mediated by interactions between the FRS2a complex and GRB2associated binding protein 1 (GAB1; ref. 1)

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Conclusion