Somatic rearrangements causing oncogenic ectodomain deletions of FGFR1 in squamous cell lung cancer.

The discovery of frequent 8p11-p12 amplifications in squamous cell lung cancer (SQLC) has fueled hopes that FGFR1, located inside this amplicon, might be a therapeutic target. In a clinical trial, only 11% of patients with 8p11 amplification (detected by FISH) responded to FGFR kinase inhibitor treatment. To understand the mechanism of FGFR1 dependency, we performed deep genomic characterization of 52 SQLCs with 8p11-p12 amplification, including 10 tumors obtained from patients who had been treated with FGFR inhibitors. We discovered somatically altered variants of FGFR1 with deletion of exons 1-8 that resulted from intragenic tail-to-tail rearrangements. These ectodomain-deficient FGFR1 variants (ΔEC-FGFR1) were expressed in the affected tumors and were tumorigenic in both in vitro and in vivo models of lung cancer. Mechanistically, breakage-fusion-bridges were the source of 8p11-p12 amplification, resulting from frequent head-to-head and tail-to-tail rearrangements. Generally, tail-to-tail rearrangements within or in close proximity upstream of FGFR1 were associated with FGFR1 dependency. Thus, the genomic events shaping the architecture of the 8p11-p12 amplicon provide a mechanistic explanation for the emergence of FGFR1-driven SQLC. Specifically, we believe that FGFR1 ectodomain-deficient and FGFR1-centered amplifications caused by tail-to-tail rearrangements are a novel somatic genomic event that might be predictive of therapeutically relevant FGFR1 dependency.

Synergistic anti-angiogenic treatment effects by dual FGFR1 and VEGFR1 inhibition in FGFR1-amplified breast cancer.

FGFR1 amplification has been found in 15% of patients with breast cancer and has been postulated as a promising marker to predict response against FGFR inhibitors. However, early phase clinical trials of selective FGFR inhibitors demonstrated only limited efficacy in FGFR1-amplified breast cancer patients. We found that BGJ398, an FGFR inhibitor, effectively inhibited phosphorylation of FGFR1 and MEK/ERK signaling in FGFR1-amplified breast cancer without affecting tumor cell proliferation. However, FGFR1 knockout inhibited tumor angiogenesis in vivo. We unraveled that FGFR1 regulates the secretion of the proangiogenic vascular endothelial growth factor (VEGF) in a MAPK-dependent manner. We further found that FGF-FGFR1 signaling induces an autocrine activation of VEGF-VEGFR1 pathway that again amplifies VEGF secretion via VEGF-VEGFR1-AKT signaling. Targeting both VEGFR1 and FGFR1 resulted in synergistic anti-angiogenic treatment effects in vivo. We thus postulate synergistic treatment effects in FGFR1/VEGFR1-positive breast cancer patients by dual targeting of FGFR and VEGFR.

Integrative genomic profiling of large-cell neuroendocrine carcinomas reveals distinct subtypes of high-grade neuroendocrine lung tumors.

Pulmonary large-cell neuroendocrine carcinomas (LCNECs) have similarities with other lung cancers, but their precise relationship has remained unclear. Here we perform a comprehensive genomic (n = 60) and transcriptomic (n = 69) analysis of 75 LCNECs and identify two molecular subgroups: "type I LCNECs" with bi-allelic TP53 and STK11/KEAP1 alterations (37%), and "type II LCNECs" enriched for bi-allelic inactivation of TP53 and RB1 (42%). Despite sharing genomic alterations with adenocarcinomas and squamous cell carcinomas, no transcriptional relationship was found; instead LCNECs form distinct transcriptional subgroups with closest similarity to SCLC. While type I LCNECs and SCLCs exhibit a neuroendocrine profile with ASCL1high/DLL3high/NOTCHlow, type II LCNECs bear TP53 and RB1 alterations and differ from most SCLC tumors with reduced neuroendocrine markers, a pattern of ASCL1low/DLL3low/NOTCHhigh, and an upregulation of immune-related pathways. In conclusion, LCNECs comprise two molecularly defined subgroups, and distinguishing them from SCLC may allow stratified targeted treatment of high-grade neuroendocrine lung tumors.

Mechanisms of Primary Drug Resistance in FGFR1-Amplified Lung Cancer.

Purpose: The 8p12-p11 locus is frequently amplified in squamous cell lung cancer (SQLC); the receptor tyrosine kinase fibroblast growth factor receptor 1 (FGFR1) being one of the most prominent targets of this amplification. Thus, small molecules inhibiting FGFRs have been employed to treat FGFR1-amplified SQLC. However, only about 11% of such FGFR1-amplified tumors respond to single-agent FGFR inhibition and several tumors exhibited insufficient tumor shrinkage, compatible with the existence of drug-resistant tumor cells.Experimental Design: To investigate possible mechanisms of resistance to FGFR inhibition, we studied the lung cancer cell lines DMS114 and H1581. Both cell lines are highly sensitive to three different FGFR inhibitors, but exhibit sustained residual cellular viability under treatment, indicating a subpopulation of existing drug-resistant cells. We isolated these subpopulations by treating the cells with constant high doses of FGFR inhibitors.Results: The FGFR inhibitor-resistant cells were cross-resistant and characterized by sustained MAPK pathway activation. In drug-resistant H1581 cells, we identified NRAS amplification and DUSP6 deletion, leading to MAPK pathway reactivation. Furthermore, we detected subclonal NRAS amplifications in 3 of 20 (15%) primary human FGFR1-amplified SQLC specimens. In contrast, drug-resistant DMS114 cells exhibited transcriptional upregulation of MET that drove MAPK pathway reactivation. As a consequence, we demonstrate that rational combination therapies resensitize resistant cells to treatment with FGFR inhibitors.Conclusions: We provide evidence for the existence of diverse mechanisms of primary drug resistance in FGFR1-amplified lung cancer and provide a rational strategy to improve FGFR inhibitor therapies by combination treatment. Clin Cancer Res; 23(18); 5527-36. ©2017 AACR.

CD74-NRG1 fusions in lung adenocarcinoma.

UNLABELLED: We discovered a novel somatic gene fusion, CD74-NRG1, by transcriptome sequencing of 25 lung adenocarcinomas of never smokers. By screening 102 lung adenocarcinomas negative for known oncogenic alterations, we found four additional fusion-positive tumors, all of which were of the invasive mucinous subtype. Mechanistically, CD74-NRG1 leads to extracellular expression of the EGF-like domain of NRG1 III-ß3, thereby providing the ligand for ERBB2-ERBB3 receptor complexes. Accordingly, ERBB2 and ERBB3 expression was high in the index case, and expression of phospho-ERBB3 was specifically found in tumors bearing the fusion (P < 0.0001). Ectopic expression of CD74-NRG1 in lung cancer cell lines expressing ERBB2 and ERBB3 activated ERBB3 and the PI3K-AKT pathway, and led to increased colony formation in soft agar. Thus, CD74-NRG1 gene fusions are activating genomic alterations in invasive mucinous adenocarcinomas and may offer a therapeutic opportunity for a lung tumor subtype with, so far, no effective treatment. SIGNIFICANCE: CD74­NRG1 fusions may represent a therapeutic opportunity for invasive mucinous lung adenocarcinomas, a tumor with no effective treatment that frequently presents with multifocal unresectable disease.

Cell-autonomous and non-cell-autonomous mechanisms of transformation by amplified FGFR1 in lung cancer.

UNLABELLED: The 8p12 locus (containing the FGFR1 tyrosine kinase gene) is frequently amplified in squamous cell lung cancer. However, it is currently unknown which of the 8p12-amplified tumors are also sensitive to fibroblast growth factor receptor (FGFR) inhibition. We found that, in contrast with other recurrent amplifications, the 8p12 region included multiple centers of amplification, suggesting marked genomic heterogeneity. FGFR1-amplified tumor cells were dependent on FGFR ligands in vitro and in vivo. Furthermore, ectopic expression of FGFR1 was oncogenic, which was enhanced by expression of MYC. We found that MYC was coexpressed in 40% of FGFR1-amplified tumors. Tumor cells coexpressing MYC were more sensitive to FGFR inhibition, suggesting that patients with FGFR1-amplified and MYC-overexpressing tumors may benefit from FGFR inhibitor therapy. Thus, both cell-autonomous and non-cell-autonomous mechanisms of transformation modulate FGFR dependency in FGFR1-amplified lung cancer, which may have implications for patient selection for treatment with FGFR inhibitors. SIGNIFICANCE: Amplification of FGFR1 is one of the most frequent candidate targets in lung cancer. Here, we show that multiple factors affect the tumorigenic potential of FGFR1, thus providing clinical hypotheses for refinement of patient selection.

A framework for identification of actionable cancer genome dependencies in small cell lung cancer.

Small cell lung cancer (SCLC) accounts for about 15% of all lung cancers. The prognosis of SCLC patients is devastating and no biologically targeted therapeutics are active in this tumor type. To develop a framework for development of specific SCLC-targeted drugs we conducted a combined genomic and pharmacological vulnerability screen in SCLC cell lines. We show that SCLC cell lines capture the genomic landscape of primary SCLC tumors and provide genetic predictors for activity of clinically relevant inhibitors by screening 267 compounds across 44 of these cell lines. We show Aurora kinase inhibitors are effective in SCLC cell lines bearing MYC amplification, which occur in 3-7% of SCLC patients. In MYC-amplified SCLC cells Aurora kinase inhibition associates with G2/M-arrest, inactivation of PI3-kinase (PI3K) signaling, and induction of apoptosis. Aurora dependency in SCLC primarily involved Aurora B, required its kinase activity, and was independent of depletion of cytoplasmic levels of MYC. Our study suggests that a fraction of SCLC patients may benefit from therapeutic inhibition of Aurora B. Thus, thorough chemical and genomic exploration of SCLC cell lines may provide starting points for further development of rational targeted therapeutic intervention in this deadly tumor type.

Translating the therapeutic potential of AZD4547 in FGFR1-amplified non-small cell lung cancer through the use of patient-derived tumor xenograft models.

PURPOSE: To investigate the incidence of FGFR1 amplification in Chinese non-small cell lung cancer (NSCLC) and to preclinically test the hypothesis that the novel, potent, and selective fibroblast growth factor receptor (FGFR) small-molecule inhibitor AZD4547 will deliver potent antitumor activity in NSCLC FGFR1-amplified patient-derived tumor xenograft (PDTX) models. EXPERIMENTAL DESIGN: A range of assays was used to assess the translational relevance of FGFR1 amplification and AZD4547 treatment including in vitro lung cell line panel screening and pharmacodynamic (PD) analysis, FGFR1 FISH tissue microarray (TMA) analysis of Chinese NSCLC (n = 127), and, importantly, antitumor efficacy testing and PD analysis of lung PDTX models using AZD4547. RESULTS: The incidence of FGFR1 amplification within Chinese patient NSCLC tumors was 12.5% of squamous origin (6 of 48) and 7% of adenocarcinoma (5 of 76). AZD4547 displayed a highly selective profile across a lung cell line panel, potently inhibiting cell growth only in those lines harboring amplified FGFR1 (GI(50) = 0.003-0.111 µmol/L). AZD4547 induced potent tumor stasis or regressive effects in four of five FGFR1-amplified squamous NSCLC PDTX models. Pharmacodynamic modulation was observed in vivo, and antitumor efficacy correlated well with FGFR1 FISH score and protein expression level. CONCLUSIONS: This study provides novel epidemiologic data through identification of FGFR1 gene amplification in Chinese NSCLC specimens (particularly squamous) and, importantly, extends the clinical significance of this finding by using multiple FGFR1-amplified squamous lung cancer PDTX models to show tumor stasis or regression effects using a specific FGFR inhibitor (AZD4547). Thus, the translational science presented here provides a strong rationale for investigation of AZD4547 as a therapeutic option for patients with squamous NSCLC tumors harboring amplification of FGFR1.

Differential protein stability and ALK inhibitor sensitivity of EML4-ALK fusion variants.

PURPOSE: ALK rearrangement-positive lung cancers can be effectively treated with ALK inhibitors. However, the magnitude and duration of response is heterogeneous. In addition, acquired resistance limits the efficacy of ALK inhibitors, with most upfront resistance mechanisms being unknown. EXPERIMENTAL DESIGN: By making use of the Ba/F3 cell line model, we analyzed the cytotoxic efficacy of ALK kinase inhibitors as a function of different EML4-ALK fusion variants v1, v2, v3a, and v3b as well as of three artificially designed EML4-ALK deletion constructs and the ALK fusion genes KIF5b-ALK and NPM1-ALK. In addition, the intracellular localization, the sensitivity to HSP90 inhibition and the protein stability of ALK fusion proteins were studied. RESULTS: Different ALK fusion genes and EML4-ALK variants exhibited differential sensitivity to the structurally diverse ALK kinase inhibitors crizotinib and TAE684. In addition, differential sensitivity correlated with differences in protein stability in EML4-ALK-expressing cells. Furthermore, the sensitivity to HSP90 inhibition also varied depending on the ALK fusion partner but differed from ALK inhibitor sensitivity patterns. Finally, combining inhibitors of ALK and HSP90 resulted in synergistic cytotoxicity. CONCLUSIONS: Our results might explain some of the heterogeneous responses of ALK-positive tumors to ALK kinase inhibition observed in the clinic. Thus, targeted therapy of ALK-positive lung cancer should take into account the precise ALK genotype. Furthermore, combining ALK and HSP90 inhibitors might enhance tumor shrinkage in EML4-ALK-driven tumors.