Inhibition of fibroblast growth factor receptor 3-dependent lung adenocarcinoma with a human monoclonal antibody

Identification of a myofibroblast differentiation program during neonatal lung development

Alveologenesis is the final stage of lung development in which the internal surface area of the lung is increased to facilitate efficient gas exchange in the mature organism. The first phase of alveologenesis involves the formation of septal ridges (secondary septae) and the second phase involves thinning of the alveolar septa. Within secondary septa, mesenchymal cells include a transient population of alveolar myofibroblasts (MyoFBs) and a stable but poorly described population of lipid-rich cells that have been referred to as lipofibroblasts or matrix fibroblasts (MatFBs). Using a unique Fgf18CreER lineage trace mouse line, cell sorting, single-cell RNA sequencing and primary cell culture, we have identified multiple subtypes of mesenchymal cells in the neonatal lung, including an immature progenitor cell that gives rise to mature MyoFB. We also show that the endogenous and targeted ROSA26 locus serves as a sensitive reporter for MyoFB maturation. These studies identify a MyoFB differentiation program that is distinct from other mesenchymal cell types and increases the known repertoire of mesenchymal cell types in the neonatal lung.

Identification of a myofibroblast differentiation program during neonatal lung development

Alveologenesis is the final stage of lung development in which the internal surface area of the lung is increased to facilitate efficient gas exchange in the mature organism. The first phase of alveologenesis involves the formation of septal ridges (secondary septae) and the second phase involves thinning of the alveolar septa. Within secondary septa, mesenchymal cells include a transient population of alveolar myofibroblasts (MyoFB) and a stable but poorly described population of lipid rich cells that have been referred to as lipofibroblasts or matrix fibroblasts (MatFB). Using a unique Fgf18CreER lineage trace mouse line, cell sorting, single cell RNA sequencing, and primary cell culture, we have identified multiple subtypes of mesenchymal cells in the neonatal lung, including an immature progenitor cell that gives rise to mature MyoFB. We also show that the endogenous and targeted ROSA26 locus serves as a sensitive reporter for MyoFB maturation. These studies identify a myofibroblast differentiation program that is distinct form other mesenchymal cells types and increases the known repertoire of mesenchymal cell types in the neonatal lung.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

Semi-Automated Cell Panning for Efficient Isolation of FGFR3-Targeting Antibody

Phage display technology is a widely used practical tool for isolating binding molecules against the desired targets in phage libraries. In the case of targeting the membrane protein with its natural conformation, conventional bio-panning has limitations on the efficient screening of the functionally relevant antibodies. To enrich the single-chain variable fragment (scFv) pools for recognizing the natural conformation of the membrane targets, the conventional bio-panning and screening process was modified to include the semi-automated cell panning protocol. Using FGFR3-overexpressing patient-derived cancer cells, biotin-X-DHPE was introduced and coupled to Streptavidin-coated magnetic beads for use in the solution-phage bio-panning procedure. The resulting clones of scFv were compared to the diversity of the binding region, especially on CDR-H3. The clones enriched further by cell-based panning procedure possessed a similar binding site and the CDR-H3 loop structure. The resulting antibodies inhibited cell growth and induced target degradation. This process may be a useful tool for screening biologically related antibodies that recognize natural conformational structure on cell membrane protein. Furthermore, cell-based panning has the potential to further expand to a high-throughput screening (HTS) system and automation process.

Novel therapeutic approaches for the treatment of achondroplasia

Achondroplasia is the most common form of human dwarfism. The molecular basis of achondroplasia was elucidated in 1994 with the identification of the fibroblast growth factor receptor 3 (FGFR3) as the causative gene. Missense mutations causing achondroplasia result in activation of FGFR3 and its downstream signaling pathways, disturbing chondrogenesis, osteogenesis, and long bone elongation. A more accurate understanding of the clinical and molecular aspects of achondroplasia has allowed new therapeutic approaches to be developed. These are based on: clear understanding of the natural history of the disease; proof-of-concept preclinical studies in mouse models; and the current state of knowledge regarding FGFR3 and related growth plate homeostatic pathways. This review provides a brief overview of the preclinical mouse models of achondroplasia that have led to new, non-surgical therapeutic strategies being assessed and applied to children with achondroplasia through pioneering clinical trials.

FGF9 and FGF10 activate distinct signaling pathways to direct lung epithelial specification and branching

Fibroblast growth factors (FGFs) 9 and 10 are essential during the pseudoglandular stage of lung development. Mesothelium-produced FGF9 is principally responsible for mesenchymal growth, whereas epithelium-produced FGF9 and mesenchyme-produced FGF10 guide lung epithelial development, and loss of either of these ligands affects epithelial branching. Because FGF9 and FGF10 activate distinct FGF receptors (FGFRs), we hypothesized that they would control distinct developmental processes. Here, we found that FGF9 signaled through epithelial FGFR3 to directly promote distal epithelial fate specification and inhibit epithelial differentiation. By contrast, FGF10 signaled through epithelial FGFR2b to promote epithelial proliferation and differentiation. Furthermore, FGF9-FGFR3 signaling functionally opposed FGF10-FGFR2b signaling, and FGFR3 preferentially used downstream phosphoinositide 3-kinase (PI3K) pathways, whereas FGFR2b relied on downstream mitogen-activated protein kinase (MAPK) pathways. These data demonstrate that, within lung epithelial cells, different FGFRs function independently; they bind receptor-specific ligands and direct distinct developmental functions through the activation of distinct downstream signaling pathways.

Concomitant genomic alterations in KRAS mutant advanced lung adenocarcinoma

OBJECTIVES

KRAS mutations are one of the most prevalent alterations in non-small cell lung cancer. However, patients with this driver alteration present heterogeneous clinical outcomes. In this study, we have explored the potential clinical impact of coexisting alterations in this subset of patients.

MATERIALS AND METHODS

Samples from a cohort of 69 lung adenocarcinoma patients homogenously treated with platinum doublet as first-line therapy were evaluated using targeted next generation sequencing (NGS). Mutations and copy number alterations were assessed in 37 advanced KRAS-mutant (KRASm) and in 32 KRAS wild-type (KRASwt).

RESULTS

TP53 was the most frequent additional alteration found in both cohorts. Interestingly, TP53 mutations were more frequent in KRASwt than in KRASm patients (80 % vs. 34 %; p <  0.05) as well as STK11 mutations (17 % vs 8 %, p=NS). FGFR3 mutations were only found concomitantly with KRASm (11 %). No genomic co-alteration had an impact on overall survival within the KRASm patients treated with chemotherapy.

CONCLUSIONS

KRAS mutated lung adenocarcinoma is a heterogeneous entity and comprehensive characterization of co-alterations using NGS may lead to more accurate patient stratification.

Development of a Monomeric Inhibitory RNA Aptamer Specific for FGFR3 that Acts as an Activator When Dimerized

There have been limited options for people who suffer from fibroblast growth factor receptor (FGFR) signaling disorders. In this study, we developed RNA aptamers specific for FGFR3 as potential therapeutic agents. Using a structured aptamer library, we performed ten rounds of SELEX (systematic evolution of ligands by exponential enrichment) against mouse FGFR3c protein. Using an engineered BaF3 cell line, one aptamer clone from round 6 of the selection inhibited FGF-dependent cell growth with a concentration at which 50% of growth is observed (IC50) of ∼260 nM and bound both mouse and human FGFR3 but not FGFR1 or FGFR2. This inhibitor of FGFR3 signaling (iR3), when dimerized using a template-driven approach, resulted in a functional activator of FGFR3 (aR3). We validated the activity and specificity of iR3 and aR3 on engineered BaF3 cell lines, mouse and human FGFR protein, and primary cultures of neuroepithelial precursor cells.

Effect of FGF/FGFR pathway blocking on lung adenocarcinoma and its cancer-associated fibroblasts

Cancer-associated fibroblasts (CAFs) are known to promote tumourigenesis through various mechanisms. Fibroblast growth factor (FGF)/FGF receptor (FGFR)-dependent lung cancers have been described. We have developed a mouse model of lung adenocarcinoma that was constructed through the induction of Fgf9 overexpression in type 2 alveolar cells. The expression of Fgf9 in adult lungs resulted in the rapid development of multiple adenocarcinoma-like tumour nodules. Here, we have characterised the contribution of CAFs and the Fgf/Fgfr signalling pathway in maintaining the lung tumours initiated by Fgf9 overexpression. We found that CAF-secreted Fgf2 contributes to tumour cell growth. CAFs overexpressed Tgfb, Mmp7, Fgf9, and Fgf2; synthesised more collagen, and secreted inflammatory cell-recruiting cytokines. CAFs also enhanced the conversion of tumour-associated macrophages (TAMs) to the tumour-supportive M2 phenotype but did not influence angiogenesis. In vivo inhibition of Fgfrs during early lung tumour development resulted in significantly smaller and fewer tumour nodules, whereas inhibition in established lung tumours caused a significant reduction in tumour size and number. Fgfr inhibition also influenced tumour stromal cells, as it significantly abolished TAM recruitment and reduced tumour vascularity. However, the withdrawal of the inhibitor caused a significant recurrence/regrowth of Fgf/Fgfr-independent lung tumours. These recurrent tumours did not possess a higher proliferative or propagative potential. Our results provide evidence that fibroblasts associated with the Fgf9-induced lung adenocarcinoma provide multiple means of support to the tumour. Although the Fgfr blocker significantly suppressed the tumour and its stromal cells, it was not sufficient to completely eliminate the tumour, probably due to the emergence of alternative (resistance/maintenance) mechanism(s). This model represents an excellent tool to further study the complex interactions between CAFs, their related chemokines, and the progression of lung adenocarcinoma; it also provides further evidence to support the need for a combinatorial strategy to treat lung cancer. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Fibroblast growth factors in skeletal development

Fibroblast growth factors (FGFs) and their receptors (FGFRs) are expressed throughout all stages of skeletal development. In the limb bud and in cranial mesenchyme, FGF signaling is important for formation of mesenchymal condensations that give rise to bone. Once skeletal elements are initiated and patterned, FGFs regulate both endochondral and intramembranous ossification programs. In this chapter, we review functions of the FGF signaling pathway during these critical stages of skeletogenesis, and explore skeletal malformations in humans that are caused by mutations in FGF signaling molecules.

A novel FGFR1-binding peptide exhibits anti-tumor effect on lung cancer by inhibiting proliferation and angiogenesis

It has been reported that overactivation of fibroblast growth factor receptor 1 (FGFR1) is an important characteristic found in most non-small cell lung cancer (NSCLC) samples. Here, we identified a FGFR1 inhibitory peptide R1-P2 and investigated its effects on the lung cancer cells growth and angiogenesis in vitro and in vivo. Our results demonstrate that R1-P2 bound to human FGFR1 protein, and efficiently blocked the binding of FGF2 to FGFR1 in A549 and NCI-H460 cells. Moreover, this peptide significantly decreased the proliferation, migration and invasion, but promoted the apoptosis in both cell lines. In addition, R1-P2 treatment effectively inhibited the tumor growth and neovascularization in nude mice with xenografted A549 cells, and R1-P2 also significantly inhibited the FGF2-induced angiogenesis in tube formation experiment and CAM model. We further demonstrated that R1-P2 suppressed lung tumor growth through anti-angiogenic and anti-proliferative activity. Our data may provide a novle leading molecule with potential application in the treatment of FGFR1 activation related lung cancers.

Tumor associated macrophages support the growth of FGF9-induced lung adenocarcinoma by multiple mechanisms

OBJECTIVES

Tumor-associated macrophages (TAMs) are known to promote tumorigenesis but the mechanism(s) remain elusive. We have developed a mouse model of lung cancer that is initiated through an inducible overexpression of fibroblast growth factor 9 (FGF9) in type-2 pneumocytes. Expression of FGF9 in adult lungs resulted in a rapid development of multiple adenocarcinoma-like tumor nodules, and is associated with an intense immunological reaction. The purpose of this study is to characterize the immune response to the FGF9-induced lung adenocarcinoma and to determine the contribution of TAMs to growth and survival of these tumors.

MATERIALS AND METHODS

We used flow cytometry, immunostaining, RT-PCR and in vitro culture system on various cell populations isolated from the FGF9-induced adenocarcinoma mouse lungs.

RESULTS

Immunostaining demonstrated that the majority of the inflammatory cells recruited to FGF9-induced lung tumors were macrophages. These TAMs were enriched for the alternatively activated (M2) macrophage subtype. TAMs performed a significantly high immune suppressive function on T-cells and displayed high levels of arginase-1 expression and activity. The growth and colony forming potential of tumor cells was induced by co-culture with TAMs. Additionally, TAMs were shown to promote fibroblast proliferation and angiogenesis. TAMs had high expression of Tgf-β, Vegf, Fgf2, Fgf10, Fgfr2 and several matrix metalloproteinases; factors that play multiple roles in supporting tumor growth, immune protection, fibroblast activation and angiogenesis.

CONCLUSION

Our results provide evidence that the Fgf9-induced lung adenocarcinoma is associated with recruitment and activation of M2-biased TAMs, which provided multiple means of support to the tumor. This model represents an excellent means to further study the complex interactions between TAMs, their related chemokines, and progression of lung adenocarcinoma, and adds further evidence to support the importance of TAMs in tumorigenesis.

Pulmonary fibrosis requires cell-autonomous mesenchymal fibroblast growth factor (FGF) signaling

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive pulmonary scarring, decline in lung function, and often results in death within 3-5 five years after diagnosis. Fibroblast growth factor (FGF) signaling has been implicated in the pathogenesis of IPF; however, the mechanism through which FGF signaling contributes to pulmonary fibrosis remains unclear. We hypothesized that FGF receptor (FGFR) signaling in fibroblasts is required for the fibrotic response to bleomycin. To test this, mice with mesenchyme-specific tamoxifen-inducible inactivation of FGF receptors 1, 2, and 3 (Col1α2-CreER; TCKO mice) were lineage labeled and administered intratracheal bleomycin. Lungs were collected for histologic analysis, whole lung RNA and protein, and dissociated for flow cytometry and FACS. Bleomycin-treated Col1α2-CreER; TCKO mice have decreased pulmonary fibrosis, collagen production, and fewer α-smooth muscle actin-positive (αSMA+) myofibroblasts compared with controls. Freshly isolated Col1α2-CreER; TCKO mesenchymal cells from bleomycin-treated mice have decreased collagen expression compared with wild type mesenchymal cells. Furthermore, lineage labeled FGFR-deficient fibroblasts have decreased enrichment in fibrotic areas and decreased proliferation. These data identify a cell autonomous requirement for mesenchymal FGFR signaling in the development of pulmonary fibrosis, and for the enrichment of the Col1α2-CreER-positive (Col1α2+) mesenchymal lineage in fibrotic tissue following bleomycin exposure. We conclude that mesenchymal FGF signaling is required for the development of pulmonary fibrosis, and that therapeutic strategies aimed directly at mesenchymal FGF signaling could be beneficial in the treatment of IPF.

Achondroplasia: Development, pathogenesis, and therapy

Autosomal dominant mutations in fibroblast growth factor receptor 3 (FGFR3) cause achondroplasia (Ach), the most common form of dwarfism in humans, and related chondrodysplasia syndromes that include hypochondroplasia (Hch), severe achondroplasia with developmental delay and acanthosis nigricans (SADDAN), and thanatophoric dysplasia (TD). FGFR3 is expressed in chondrocytes and mature osteoblasts where it functions to regulate bone growth. Analysis of the mutations in FGFR3 revealed increased signaling through a combination of mechanisms that include stabilization of the receptor, enhanced dimerization, and enhanced tyrosine kinase activity. Paradoxically, increased FGFR3 signaling profoundly suppresses proliferation and maturation of growth plate chondrocytes resulting in decreased growth plate size, reduced trabecular bone volume, and resulting decreased bone elongation. In this review, we discuss the molecular mechanisms that regulate growth plate chondrocytes, the pathogenesis of Ach, and therapeutic approaches that are being evaluated to improve endochondral bone growth in people with Ach and related conditions. Developmental Dynamics 246:291-309, 2017. © 2016 Wiley Periodicals, Inc.