Covalent Targeting of Fibroblast Growth Factor Receptor Inhibits Metastatic Breast Cancer

Abstract

Therapeutic targeting of late-stage breast cancer is limited by an inadequate understanding of how tumor cell signaling evolves during metastatic progression and by the currently available small molecule inhibitors capable of targeting these processes. Herein, we demonstrate that both β3 integrin and fibroblast growth factor receptor-1 (FGFR1) are part of an epithelial-mesenchymal transition (EMT) program that is required to facilitate metastatic outgrowth in response to fibroblast growth factor-2 (FGF2). Mechanistically, β3 integrin physically disrupts an interaction between FGFR1 and E-cadherin, leading to a dramatic redistribution of FGFR1 subcellular localization, enhanced FGF2 signaling and increased three-dimensional (3D) outgrowth of metastatic breast cancer cells. This ability of β3 integrin to drive FGFR signaling requires the enzymatic activity of focal adhesion kinase (FAK). Consistent with these mechanistic data, we demonstrate that FGFR, β3 integrin and FAK constitute a molecular signature capable of predicting decreased survival of patients with the basal-like subtype of breast cancer. Importantly, covalent targeting of a conserved cysteine in the P-loop of FGFR1-4 with our newly developed small molecule, FIIN-4, more effectively blocks 3D metastatic outgrowth as compared to currently available FGFR inhibitors. In vivo application of FIIN-4 potently inhibited the growth of metastatic, patient-derived breast cancer xenografts and murine-derived metastases growing within the pulmonary microenvironment. Overall, the current studies demonstrate that FGFR1 works in concert with other EMT effector molecules to drive aberrant downstream signaling, and that these events can be effectively targeted using our novel therapeutics for the treatment of the most aggressive forms of breast cancer.

FGFR signaling maintains a drug persistent cell population following epithelial-mesenchymal transition

“…These data are supported by previous findings that demonstrate an FGF2 signaling loop is at play in basal-like breast cancer [26]. Furthermore, together with our recent study we conclude that FGF2 and β3 integrin are part of an EMT signature that contribute to FGFR1-mediated drug resistance and metastatic progression [15]. Along these lines, recent clinical data indicate that unlike the autoactivation of Her2 upon gene amplification, FGFR1 amplification alone is insufficient to predict patient response to FGFR inhibitor therapy [27].…”

“…However, the role of FGFR may have been underestimated in these studies due to the use of Type I ATP competitive FGFR kinase inhibitors. Indeed, the findings herein and our recently published studies clearly point to the enhanced efficacy of covalent FGFR inhibitors as compared to ATP competitive molecules [15]. Furthermore, our utilization of both the HMLE and BT474 models of Her2+ breast cancer clearly demonstrate that enhanced FGFR1 expression when in the presence of FGF ligand is sufficient to facilitate resistance to Lapatinib treatment.…”

Integrins in the Spotlight of Cancer

“…Moreover, during EMT and the reverse mechanism known as mesenchymal-epithelial transition (MET), FGFR1 was found to be upregulated upon stimulation with TGF-β1 in a breast cancer cell model [135]. A novel study showed that FGFR is associated to E-cadherin, but under expression of β3 integrin subunit, which is upregulated upon TGF-β stimulation [136], FGFR dissociates from E-cadherin and associates with β3 integrin, leading to Erk1/2 phosphorylation in response to FGF2 [137,138]. Bone morphogenic protein 7 (BMP-7) is a cytokine that belongs to the TGF-β superfamily [139] and was shown to induce invasion in hepatocellular carcinoma cells [140], breast cancer cells [141] and chondrosarcoma cells [142].…”

Transglutaminase-2 facilitates extracellular vesicle-mediated establishment of the metastatic niche

“…Luciferase expressing 4T1 and HMLE cells were transformed via overexpression of Her2 and their mesenchymal variants were described previously 20,34 . Ca1a cells were kindly provided by Dr. Fred Miller (Wayne St. University).…”