Fibroblast growth factor receptors are components of autocrine signaling networks in head and neck squamous cell carcinoma cells.
ABSTRACT: We previously reported that a fibroblast growth factor (FGF) receptor (FGFR) signaling pathway drives growth of lung cancer cell lines of squamous and large cell histologies. Herein, we explored FGFR dependency in cell lines derived from the tobacco-related malignancy, head and neck squamous cell carcinoma (HNSCC).FGF and FGFR mRNA and protein expression was assessed in nine HNSCC cell lines. Dependence on secreted FGF2 for cell growth was tested with FP-1039, an FGFR1-Fc fusion protein. FGFR and epidermal growth factor receptor (EGFR) dependence was defined by sensitivity to multiple inhibitors selective for FGFRs or EGFR.FGF2 was expressed in eight of the nine HNSCC cell lines examined. Also, FGFR2 and FGFR3 were frequently expressed, whereas only two lines expressed FGFR1. FP-1039 inhibited growth of HNSCC cell lines expressing FGF2, identifying FGF2 as an autocrine growth factor. FGFR inhibitors selectively reduced in vitro growth and extracellular signal-regulated kinase signaling in three HNSCC cell lines, whereas three distinct lines exhibited responsiveness to both EGFR and FGFR inhibitors. Combinations of these drugs yielded additive growth inhibition. Finally, three cell lines were highly sensitive to EGFR tyrosine kinase inhibitors (TKI) with no contribution from FGFR pathways.FGFR signaling was dominant or codominant with EGFR in six HNSCC lines, whereas three lines exhibited little or no role for FGFRs and were highly EGFR dependent. Thus, the HNSCC cell lines can be divided into subsets defined by sensitivity to EGFR and FGFR-specific TKIs. FGFR inhibitors may represent novel therapeutics to deploy alone or in combination with EGFR inhibitors in HNSCC.
Project description:UNLABELLED:Activation of fibroblast growth factor receptors (FGFR) is a common oncogenic event. Little is known about the determinants of sensitivity to FGFR inhibition and how these may vary between different oncogenic FGFRs. Using parallel RNA interference (RNAi) genetic screens, we show that the EGF receptor (EGFR) limits sensitivity to FGFR inhibition in FGFR3-mutant and -translocated cell lines, but not in other FGFR-driven cell lines. We also identify two distinct mechanisms through which EGFR limits sensitivity. In partially FGFR3-dependent lines, inhibition of FGFR3 results in transient downregulation of mitogen-activated protein kinase signaling that is rescued by rapid upregulation of EGFR signaling. In cell lines that are intrinsically resistant to FGFR inhibition, EGFR dominates signaling via repression of FGFR3, with EGFR inhibition rescued by delayed upregulation of FGFR3 expression. Importantly, combinations of FGFR and EGFR inhibitors overcome these resistance mechanisms in vitro and in vivo. Our results illustrate the power of parallel RNAi screens in identifying common resistance mechanisms to targeted therapies. SIGNIFICANCE:Our data identify a novel therapeutic approach to the treatment of FGFR3-mutant cancer, emphasizing the potential of combination approaches targeting both FGFR3 and EGFR. Our data extend the role of EGFR in mediating resistance to inhibitors targeting a mutant oncogene, showing that EGFR signaling can repress mutant FGFR3 to induce intrinsic resistance to FGFR targeting.
Project description:The epidermal growth factor receptor (EGFR) is overexpressed in approximately 90% of head and neck squamous cell carcinomas (HNSCC), and molecularly targeted therapy against the EGFR with the monoclonal antibody cetuximab modestly increases overall survival in head and neck cancer patients. We hypothesize that co-signaling through additional pathways limits the efficacy of cetuximab and EGFR-specific tyrosine kinase inhibitors (TKIs) in the clinical treatment of HNSCC. Analysis of gene expression changes in HNSCC cell lines treated 4 days with TKIs targeting EGFR and/or fibroblast growth factor receptors (FGFRs) identified transforming growth factor beta 2 (TGF-β2) induction in the three cell lines tested. Measurement of TGF-β2 mRNA validated this observation and extended it to additional cell lines. Moreover, TGF-β2 mRNA was increased in primary patient HNSCC xenografts treated for 4 weeks with cetuximab, demonstrating in vivo relevance of these findings. Functional genomics analyses with shRNA libraries identified TGF-β2 and TGF-β receptors (TGFβRs) as synthetic lethal genes in the context of TKI treatment. Further, direct RNAi-mediated silencing of TGF-β2 inhibited cell growth, both alone and in combination with TKIs. Also, a pharmacological TGFβRI inhibitor similarly inhibited basal growth and enhanced TKI efficacy. In summary, the studies support a TGF-β2-TGFβR pathway as a TKI-inducible growth pathway in HNSCC that limits efficacy of EGFR-specific inhibitors. HNSCC cell lines treated 4 days with TKIs targeting EGFR and/or fibroblast growth factor receptors (FGFRs) identified transforming growth factor beta 2 (TGF-β2) induction in the three cell lines tested
Project description:The estrogen receptor (ER) promotes non-small cell lung cancer (NSCLC) proliferation. Since fibroblast growth factors (FGFs) are known regulators of stem cell markers in ER positive breast cancer, we investigated whether a link between the ER, FGFs, and stem cell markers exists in NSCLC. In lung preneoplasias and adenomas of tobacco carcinogen exposed mice, the anti-estrogen fulvestrant and/or the aromatase inhibitor anastrozole blocked FGF2 and FGF9 secretion, and reduced expression of the stem cell markers SOX2 and nanog. Mice administered ?-estradiol during carcinogen exposure showed increased FGF2, FGF9, SOX2, and Nanog expression in airway preneoplasias. In normal FGFR1 copy number NSCLC cell lines, multiple FGFR receptors were expressed and secreted several FGFs. ?-estradiol caused enhanced FGF2 release, which was blocked by fulvestrant. Upon co-inhibition of ER and FGFRs using fulvestrant and the pan-FGFR inhibitor AZD4547, phosphorylation of FRS2, the FGFR docking protein, was maximally reduced, and enhanced anti-proliferative effects were observed. Combined AZD4547 and fulvestrant enhanced lung tumor xenograft growth inhibition and decreased Ki67 and stem cell marker expression. To verify a link between ER?, the predominant ER in NSCLC, and FGFR signaling in patient tumors, mRNA analysis was performed comparing high versus low ER? expressing tumors. The top differentially expressed genes in high ER? tumors involved FGF signaling and human embryonic stem cell pluripotency. These results suggest interaction between the ER and FGFR pathways in NSCLC promotes a stem-like state. Combined FGFR and ER inhibition may increase the efficacy of FGFR inhibitors for NSCLC patients lacking FGFR genetic alterations.
Project description:The epidermal growth factor receptor (EGFR) is overexpressed in approximately 90% of head and neck squamous cell carcinomas (HNSCC), and molecularly targeted therapy against the EGFR with the monoclonal antibody cetuximab modestly increases overall survival in head and neck cancer patients. We hypothesize that co-signaling through additional pathways limits the efficacy of cetuximab and EGFR-specific tyrosine kinase inhibitors (TKIs) in the clinical treatment of HNSCC. Analysis of gene expression changes in HNSCC cell lines treated 4 days with TKIs targeting EGFR and/or fibroblast growth factor receptors (FGFRs) identified transforming growth factor beta 2 (TGF-?2) induction in the three cell lines tested. Measurement of TGF-?2 mRNA validated this observation and extended it to additional cell lines. Moreover, TGF-?2 mRNA was increased in primary patient HNSCC xenografts treated for 4 weeks with cetuximab, demonstrating in vivo relevance of these findings. Functional genomics analyses with shRNA libraries identified TGF-?2 and TGF-? receptors (TGF?Rs) as synthetic lethal genes in the context of TKI treatment. Further, direct RNAi-mediated silencing of TGF-?2 inhibited cell growth, both alone and in combination with TKIs. Also, a pharmacological TGF?RI inhibitor similarly inhibited basal growth and enhanced TKI efficacy. In summary, the studies support a TGF-?2-TGF?R pathway as a TKI-inducible growth pathway in HNSCC that limits efficacy of EGFR-specific inhibitors.
Project description:Cutaneous melanoma is a tumor with rising incidence and a very poor prognosis at the disseminated stage. Melanomas are characterized by frequent mutations in BRAF and also by overexpression of fibroblast growth factor 2 (FGF2), offering opportunities for therapeutic intervention. We investigated inhibition of FGF signaling and its combination with dacarbazine or BRAF inhibitors as an antitumor strategy in melanoma. The majority of melanoma cell lines displayed overexpression of FGF2 but also FGF5 and FGF18 together with different isoforms of FGF receptors (FGFRs) 1-4. Blockade of FGF signals with dominant-negative receptor constructs (dnFGFR1, 3, or 4) or small-molecule inhibitors (SU5402 and PD166866) reduced melanoma cell proliferation, colony formation, as well as anchorage-independent growth, and increased apoptosis. DnFGFR constructs also significantly inhibited tumor growth in vivo. Combination of FGF inhibitors with dacarbazine showed additive or antagonistic effects, whereas synergistic drug interaction was observed when combining FGFR inhibition with the multikinase/BRAF inhibitor sorafenib or the V600E mutant-specific BRAF inhibitor RG7204. In conclusion, FGFR inhibition has antitumor effects against melanoma cells in vitro and in vivo. Combination with BRAF inhibition offers a potential for synergistic antimelanoma effects and represents a promising therapeutic strategy against advanced melanoma.
Project description:Despite initial and often dramatic responses of epidermal growth factor receptor (EGFR)-addicted lung tumors to the EGFR-specific tyrosine kinase inhibitors (TKIs), gefitinib and erlotinib, nearly all develop resistance and relapse. To explore novel mechanisms mediating acquired resistance, we employed non-small-cell lung cancer (NSCLC) cell lines bearing activating mutations in EGFR and rendered them resistant to EGFR-specific TKIs through chronic adaptation in tissue culture. In addition to previously observed resistance mechanisms including EGFR-T790M 'gate-keeper' mutations and MET amplification, a subset of the seven chronically adapted NSCLC cell lines including HCC4006, HCC2279 and H1650 cells exhibited marked induction of fibroblast growth factor (FGF) 2 and FGF receptor 1 (FGFR1) mRNA and protein. Also, adaptation to EGFR-specific TKIs was accompanied by an epithelial to mesenchymal transition (EMT) as assessed by changes in CDH1, VIM, ZEB1 and ZEB2 expression and altered growth properties in Matrigel. In adapted cell lines exhibiting increased FGF2 and FGFR1 expression, measures of growth and signaling, but not EMT, were blocked by FGFR-specific TKIs, an FGF-ligand trap and FGFR1 silencing with RNAi. In parental HCC4006 cells, cell growth was strongly inhibited by gefitinib, although drug-resistant clones progress within 10 days. Combined treatment with gefitinib and AZD4547, an FGFR-specific TKI, prevented the outgrowth of drug-resistant clones. Thus, induction of FGF2 and FGFR1 following chronic adaptation to EGFR-specific TKIs provides a novel autocrine receptor tyrosine kinase-driven bypass pathway in a subset of lung cancer cell lines that are initially sensitive to EGFR-specific TKIs. The findings support FGFR-specific TKIs as potentially valuable additions to existing targeted therapeutic strategies with EGFR-specific TKIs to prevent or delay acquired resistance in EGFR-driven NSCLC.
Project description:Malignant pleural mesothelioma (MPM) is associated with asbestos exposure and is a cancer that has not been significantly affected by small molecule-based targeted therapeutics. Previously, we demonstrated the existence of functional subsets of lung cancer and head and neck squamous cell carcinoma (HNSCC) cell lines in which fibroblast growth factor receptor (FGFR) autocrine signaling functions as a nonmutated growth pathway. In a panel of pleural mesothelioma cell lines, FGFR1 and FGF2 were coexpressed in three of seven cell lines and were significantly associated with sensitivity to the FGFR-active tyrosine kinase inhibitor (TKI), ponatinib, both in vitro and in vivo using orthotopically propagated xenografts. Furthermore, RNAi-mediated silencing confirmed the requirement for FGFR1 in specific mesothelioma cells and sensitivity to the FGF ligand trap, FP-1039, validated the requirement for autocrine FGFs. None of the FGFR1-dependent mesothelioma cells exhibited increased FGFR1 gene copy number, based on a FISH assay, indicating that increased FGFR1 transcript and protein expression were not mediated by gene amplification. Elevated FGFR1 mRNA was detected in a subset of primary MPM clinical specimens and like MPM cells; none harbored increased FGFR1 gene copy number. These results indicate that autocrine signaling through FGFR1 represents a targetable therapeutic pathway in MPM and that biomarkers distinct from increased FGFR1 gene copy number such as FGFR1 mRNA would be required to identify patients with MPM bearing tumors driven by FGFR1 activity.FGFR1 is a viable therapeutic target in a subset of MPMs, but FGFR TKI-responsive tumors will need to be selected by a biomarker distinct from increased FGFR1 gene copy number, possibly FGFR1 mRNA or protein levels.
Project description:Most NSCLC patients with EGFR mutations benefit from treatment with EGFR-TKIs, but the clinical efficacy of EGFR-TKIs is limited by the appearance of drug resistance. Multiple kinase inhibitors of EGFR family proteins such as afatinib have been newly developed to overcome such drug resistance. We established afatinib-resistant cell lines after chronic exposure of activating EGFR mutation-positive PC9 cells to afatinib. Afatinib-resistant cells showed following specific characteristics as compared to PC9:  Expression of EGFR family proteins and their phosphorylated molecules was markedly downregulated by selection of afatinib resistance;  Expression of FGFR1 and its ligand FGF2 was alternatively upregulated;  Treatment with anti-FGF2 neutralizing antibody blocked enhanced phosphorylation of FGFR in resistant clone;  Both resistant clones showed collateral sensitivity to PD173074, a small-molecule FGFR-TKIs, and treatment with either PD173074 or FGFR siRNA exacerbated suppression of both afatinib-resistant Akt and Erk phosphorylation when combined with afatinib;  Expression of twist was markedly augmented in resistant sublines, and twist knockdown specifically suppressed FGFR expression and cell survival. Together, enhanced expression of FGFR1 and FGF2 thus plays as an escape mechanism for cell survival of afatinib-resistant cancer cells, that may compensate the loss of EGFR-driven signaling pathway.
Project description:Fibroblast growth factors receptors (FGFRs) have been widely characterized in somatic cells, but there is scarce evidence of their expression and function in mammalian gametes. The objective of the present study was to evaluate the expression of FGFRs in human male germ cells, to determine sperm FGFR activation by the FGF2 ligand and their participation in the regulation of sperm motility. The expression of FGFR1, 2, 3 and 4 mRNAs and proteins in human testis and localization of these receptors in germ cells of the seminiferous epithelium was demonstrated. In ejaculated sperm, FGFRs were localized to the acrosomal region and flagellum. Sperm exposure to FGF2 caused an increase in flagellar FGFR phosphorylation and activation of extracellular signal-regulated kinase (ERK) and protein kinase B (PKB or Akt) signaling pathways. Incubation with FGF2 led to a significant increase in the percentage of total and progressive sperm motility, as well as in sperm kinematics. All responses were prevented by sperm preincubation with BGJ398, a specific inhibitor of FGFR tyrosine kinase activity. In addition to confirming the expression of FGFRs in germ cells of the human testis, our study describes for the first time the presence, localization and functionality of human sperm FGFRs, and provides evidence of the beneficial effect of FGF2 upon sperm motility.
Project description:PURPOSE:The oncogenic drivers of triple-negative (TN) and basal-like breast cancers are largely unknown. Substantial evidence now links aberrant signaling by the fibroblast growth factor receptors (FGFR) to the development of multiple cancer types. Here, we examined the role of FGFR signaling in TN breast cancer. EXPERIMENTAL DESIGN:We examined the sensitivity of a panel of 31 breast cancer cell lines to the selective FGFR inhibitor PD173074 and investigated the potential mechanisms underlying sensitivity. RESULTS:TN breast cancer cell lines were more sensitive to PD173074 than comparator cell lines (P = 0.011), with 47% (7/15) of TN cell lines showing significantly reduced growth. The majority of TN cell lines showed only modest sensitivity to FGFR inhibition in two-dimensional growth but were highly sensitive in anchorage-independent conditions. PD173074 inhibited downstream mitogen-activated protein kinase and PI3K-AKT signaling and induced cell-cycle arrest and apoptosis. Basal-like breast cancer cell lines were found to express FGF2 ligand (11/21 positive) and, similarly, 62% of basal-like breast cancers expressed FGF2, as assessed by immunohistochemistry compared with 5% of nonbasal breast cancers (P < 0.0001). RNA interference targeting of FGF2 in basal-like cell lines significantly reduced growth in vitro and reduced down stream signaling, suggesting an autocrine FGF2 signaling loop. Treatment with PD173074 significantly reduced the growth of CAL51 basal-like breast cancer cell line xenografts in vivo. CONCLUSIONS:Basal-like breast cancer cell lines, and breast cancers, express autocrine FGF2 and show sensitivity to FGFR inhibitors, identifying a potential novel therapeutic approach for these cancers.