Increased expression of fibroblast growth factor 8 in human breast cancer

An Integrated Proteomics and Bioinformatics Analysis of the Anticancer Properties of RT2 Antimicrobial Peptide on Human Colon Cancer (Caco-2) Cells

New selective, efficacious chemotherapy agents are in demand as traditional drugs display side effects and face growing resistance upon continued administration. To this end, bioactive molecules such as peptides are attracting interest. RT2 is a cationic peptide that was used as an antimicrobial but is being repurposed for targeting cancer. In this work, we investigate the mechanism by which this peptide targets Caco-2 human colon cancer cells, one of the most prevalent and metastatic cancers. Combining label-free proteomics with bioinformatics data, our data explore over 1000 proteins to identify 133 proteins that are downregulated and 79 proteins that are upregulated upon treatment with RT2. These changes occur in a dose-dependent manner and suggest the former group are related to anticancer cell proliferation; the latter group is closely related to apoptosis levels. The mRNA levels of several genes (FGF8, PAPSS2, CDK12, LDHA, PRKCSH, CSE1L, STARD13, TLE3, and OGDHL) were quantified using RT-qPCR and were found to be in agreement with proteomic results. Collectively, the global change in Caco-2 cell protein abundance suggests that RT2 triggers multiple mechanisms, including cell proliferation reduction, apoptosis activation, and alteration of cancerous cell metabolism.

Fibroblast growth factor receptor signalling dysregulation and targeting in breast cancer

Fibroblast Growth Factor Receptor (FGFR) signalling plays a critical role in breast embryonal development, tissue homeostasis, tumorigenesis and metastasis. FGFR, its numerous FGF ligands and signalling partners are often dysregulated in breast cancer progression and are one of the causes of resistance to treatment in breast cancer. Furthermore, FGFR signalling on epithelial cells is affected by signals from the breast microenvironment, therefore increasing the possibility of breast developmental abnormalities or cancer progression. Increasing our understanding of the multi-layered roles of the complex family of FGFRs, their ligands FGFs and their regulatory partners may offer novel treatment strategies for breast cancer patients, as a single agent or rational co-target, which will be explored in depth in this review.

Rlip Depletion Alters Oncogene Transcription at Multiple Distinct Regulatory Levels

Simple Summary

Rlip76 is a multifunctional membrane protein that facilitates cancer growth, and its depletion kills cancer cells. We recently found that Rlip depletion also results in broad changes to oncogene and tumor suppressor transcription. The present studies were designed to decipher the unknown downstream signaling pathways and transcriptional regulatory mechanisms driving the effect. Building on prior findings that Rlip depletion induces broad methylomic changes, we found using bioluminescence reporter assays that depletion of Rlip also exerts transcriptional control over several cancer genes through methylation-independent changes in transcription factor-mediated activation of their promoter regions and through additional as yet unidentified mechanisms. These findings have important implications for Rlip-targeted cancer therapy.

Abstract

Rlip76 (Rlip) is a multifunctional membrane protein that facilitates the high metabolic rates of cancer cells through the efflux of toxic metabolites and other functions. Rlip inhibition or depletion results in broad-spectrum anti-cancer effects in vitro and in vivo. Rlip depletion effectively suppresses malignancy and causes global reversion of characteristic CpG island methylomic and transcriptomic aberrations in the p53-null mouse model of spontaneous carcinogenesis through incompletely defined signaling and transcriptomic mechanisms. The methylome and transcriptome are normally regulated by the concerted actions of several mechanisms that include chromatin remodeling, promoter methylation, transcription factor interactions, and miRNAs. The present studies investigated the interaction of Rlip depletion or inhibition with the promoter methylation and transcription of selected cancer-related genes identified as being affected by Rlip depletion in our previous studies. We constructed novel promoter CpG island/luciferase reporter plasmids that respond only to CpG methylation and transcription factors. We found that Rlip depletion regulated expression by a transcription factor-based mechanism that functioned independently of promoter CpG methylation, lipid peroxidation, and p53 status.

Gene expression in regenerating and scarring tails of lizard evidences three main key genes (wnt2b, egfl6, and arhgap28) activated during the regulated process of tail regeneration

We have analyzed the expression of key genes orchestrating tail regeneration in lizard under normal and scarring conditions after cauterization. At 1-day post-cauterization (1 dpc), the injured blastema contains degenerating epithelial and mesenchymal cells, numerous mast cells, and immune cells. At 3 and 7 dpc, a stratified wound epidermis is forming while fibrocytes give rise to a scarring connective tissue. Oncogenes such as wnt2b, egfl6, wnt6, and mycn and the tumor suppressor arhgap28 are much more expressed than other oncogenes (hmga2, rhov, fgf8, fgfr4, tert, shh) and tumor suppressors (apcdd1, p63, rb, fat2, bcl11b) in the normal blastema and at 7 dpc. Blastemas at 3 dpc feature the lowest upregulation of most genes, likely derived from damage after cauterization. Immunomodulator genes nfatc4 and lef1 are more expressed at 7 dpc than in normal blastema and 3 dpc suggesting the induction of immune response favoring scarring. Balanced over-expression of oncogenes, tumor suppressor genes, and immune modulator genes determines regulation of cell proliferation (anti-oncogenic), of movement (anti-metastatic), and immunosuppression in the normal blastema. Significant higher expression of oncogenes wnt2b and egfl6 in normal blastema and higher expression of the tumor suppressor arhgap28 in the 7 dpc blastema indicate that they are among the key/master genes that determine the regulated regeneration of the tail.

SP8 Promotes an Aggressive Phenotype in Hepatoblastoma via FGF8 Activation

Hepatoblastoma (HB) is the most common malignant liver tumor in childhood and it generally has a good prognosis. However, if associated with aggressive metastatic disease, outcome is still poor. The molecular mechanisms leading to metastatic spread in HB patients are still unknown. By combining RNA-sequencing and a genome-wide methylome analysis, we identified the transcription factor SP8 and the growth factor FGF8 among the most strongly upregulated genes in metastatic HB cases, with a concomitant robust demethylation of the respective promoter regions. Of note, high expression of both candidates was associated with the aggressive C2 subtype of the 16-gene signature and poor survival. Chromatin immunoprecipitation revealed a direct transcriptional regulation of FGF8 through binding of SP8 to the FGF8 promoter. Gain- and loss-of-function experiments proved promoting effects of SP8 on motility, self-renewal, migration, and the invasive potential of HB cells. Moreover, stable overexpression of SP8 in Hep3B cells resulted in the acquisition of a mesenchymal phenotype and a strong upregulation of epithelial-mesenchymal transition-associated genes. Using KRAB-mediated CRISPR-dCas9 interference directed against FGF8, we could show that FGF8 is essential for the SP8-mediated aggressive tumor behavior. Treatment of HB cell lines with the pan SP family inhibitor mithramycin A resulted in a significant inhibition of their clonogenic growth. In summary, we identified SP8 and FGF8 as key players in aggressive traits of HB and propose SP8 inhibiting drugs as a new effective treatment strategy especially for metastatic tumors.

Post-transcriptional regulation of BRG1 by FIRΔexon2 in gastric cancer

Brahma-related gene 1 (BRG1), an ATPase subunit of the SWItch/sucrose non-fermentable (SWI/SNF) chromatin remodeling complex controls multipotent neural crest formation by regulating epithelial-mesenchymal transition (EMT)-related genes with adenosine triphosphate-dependent chromodomain-helicase DNA-binding protein 7 (CHD7). The expression of BRG1 engages in pre-mRNA splicing through interacting RNPs in cancers; however, the detailed molecular pathology of how BRG1and CHD7 relate to cancer development remains largely unveiled. This study demonstrated novel post-transcriptional regulation of BRG1 in EMT and relationship with FIRΔexon2, which is a splicing variant of the far-upstream element-binding protein (FUBP) 1-interacting repressor (FIR) lacking exon 2, which fails to repress c-myc transcription in cancers. Previously, we have reported that FIR complete knockout mice (FIR-/-) was embryonic lethal before E9.5, suggesting FIR is crucial for development. FIRΔexon2 acetylated H3K27 on promoter of BRG1 by CHIP-sequence and suppressed BRG1 expression post-transcriptionally; herein BRG1 suppressed Snai1 that is a transcriptional suppressor of E-cadherin that prevents cancer invasion and metastasis. Ribosomal proteins, hnRNPs, splicing-related factors, poly (A) binding proteins, mRNA-binding proteins, tRNA, DEAD box, and WD-repeat proteins were identified as co-immunoprecipitated proteins with FIR and FIRΔexon2 by redoing exhaustive mass spectrometry analysis. Furthermore, the effect of FIRΔexon2 on FGF8 mRNA splicing was examined as an indicator of neural development due to impaired CHD7 revealed in CHARGE syndrome. Expectedly, siRNA of FIRΔexon2 altered FGF8 pre-mRNA splicing, indicated close molecular interaction among FIRΔexon2, BRG1 and CHD7. FIRΔexon2 mRNA was elevated in human gastric cancers but not in non-invasive gastric tumors in FIR+/ mice (K19-Wnt1/C2mE x FIR+/-). The levels of FIR family (FIR, FIRΔexon2 and PUF60), BRG1, Snai1, FBW7, E-cadherin, c-Myc, cyclin-E, and SAP155 increased in the gastric tumors in FIR+/- mice compared to those expressed in wild-type mice. FIR family, Snai1, cyclin-E, BRG1, and c-Myc showed trends toward higher expression in larger tumors than in smaller tumors in Gan-mice (K19-Wnt1/C2mE). The expressions of BRG1 and Snai1 were positively correlated in the gastric tumors of the Gan-mice. Finally, BRG1 is a candidate substrate of F-box and WD-repeat domain-containing 7 (FBW7) revealed by three-dimensional crystal structure analysis that the U2AF-homology motif (UHM) of FIRΔexon2 interacted with tryptophan-425 and asparate-399 (WD)-like motif in the degron pocket of FBW7 as a UHM-ligand motif. Together, FIRΔexon2 engages in multi-step post-transcriptional regulation of BRG1, affecting EMT through the BRG1/Snai1/E-cadherin pathway and promoting tumor proliferation and invasion of gastric cancers.

A short peptide reverses the aggressive phenotype of prostate cancer cells

Previous studies have demonstrated that fibroblast growth factor 8b (FGF8b) is up-regulated in a large proportion of prostate cancer patients, and plays a key role in the aggressive progress of prostate cancer. Herein, we investigated the effects of a short peptide derived from the gN helix domain of FGF8b on the metastatic behaviors of prostate cancer cells. The results demonstrated that the synthetic peptide might reverse the effects of FGF8b on cell proliferation, migration and invasion by suppressing the activation of MAPK and Akt signaling cascades, and reducing the expressions of the metastasis-related proteins, resulting in suppression of the aggressive phenotype of the prostate cancer cells. Collectively, these results underline the therapeutic potential of the FGF8b mimic peptide in advanced prostate cancer.

Expression of teneurins is associated with tumor differentiation and patient survival in ovarian cancer

Teneurins are a family of highly conserved pair-rule proteins involved in morphogenesis and development of the central nervous system. Their function in adult tissues and in disease is largely unknown. Recent evidence suggests a role for dysregulated expression of Teneurins in human tumors, but systematic investigations are missing. Here, we investigated Teneurin-2 and Teneurin-4 expression in various cancer cell lines and in ovarian tumor tissues. Teneurin-2 and Teneurin-4 were expressed in most of the breast cancer cell lines tested. Teneurin-4 was also detected in ovarian cancer cell lines, and throughout ovarian tumors and normal ovary tissue. Ovarian tumors with low Teneurin-4 expression showed less differentiated phenotypes and these patients had shorter mean overall survival. Similarly, Teneurin-2 expression correlated with overall survival as well, especially in patients with serous tumors. In the various cell lines, 5-Aza-cytidine-induced changes in DNA methylation did not alter expression of Teneurin-2 and Teneurin-4, despite the existence of predicted CpG islands in both genes. Interestingly, however, we found evidence for the control of Teneurin-2 expression by the oncogenic growth factor FGF8. Furthermore, we identified multiple transcript splicing variants for Teneurin-2 and Teneurin-4, indicating complex gene expression patterns in malignant cells. Finally, downregulation of Teneurin-4 expression using siRNA caused a cell-type dependent increase in proliferation and resistance to cisplatin. Altogether, our data suggest that low Teneurin-4 expression provides a growth advantage to cancer cells and marks an undifferentiated state characterized by increased drug resistance and clinical aggressiveness. We conclude that Teneurin-2 and Teneurin-4 expression levels could be of prognostic value in ovarian cancer.

A long pentraxin-3-derived pentapeptide for the therapy of FGF8b-driven steroid hormone-regulated cancers

Fibroblast growth factor-8b (FGF8b) affects the epithelial/stromal compartments of steroid hormone-regulated tumors by exerting an autocrine activity on cancer cells and a paracrine pro-angiogenic function, thus contributing to tumor progression. The FGF8b/FGF receptor (FGFR) system may therefore represent a target for the treatment of steroid hormone-regulated tumors. The soluble pattern recognition receptor long pentraxin-3 (PTX3) binds various FGFs, including FGF2 and FGF8b, thus inhibiting the angiogenic and tumorigenic activity of androgen-regulated tumor cells. Nevertheless, the complex/proteinaceous structure of PTX3 hampers its pharmacological exploitation. In this context, the acetylated pentapeptide Ac-ARPCA-NH₂ (ARPCA), corresponding to the N-terminal amino acid sequence PTX3(100-104), was identified as a minimal FGF2-binding peptide able to antagonize the biological activity of FGF2. Here, we demonstrate that ARPCA binds FGF8b and inhibits its capacity to form FGFR1-mediated ternary complexes with heparan sulphate proteoglycans. As a FGF8b antagonist, ARPCA inhibits FGFR1 activation and signalling in endothelial cells, hampering the angiogenic activity exerted in vitro and in vivo by FGF8b. Also, ARPCA suppresses the angiogenic and tumorigenic potential of prototypic androgen/FGF8b-dependent Shionogi 115 mammary carcinoma cells and of androgen/FGF8b/FGF2-dependent TRAMP-C2 prostate cancer cells. In conclusion, ARPCA represents a novel FGF8b antagonist with translational implications for the therapy of steroid hormone-regulated tumors.

FGF8 promotes colorectal cancer growth and metastasis by activating YAP1

Colorectal cancer (CRC) is a major cause of cancer-related death worldwide. The poor prognosis of CRC is mainly due to uncontrolled tumor growth and distant metastases. In this study, we found that the level of FGF8 was elevated in the great majority of CRC cases and high FGF8 expression was significantly correlated with lymph nodes metastasis and worse overall survival. Functional studies showed that FGF8 can induce a more aggressive phenotype displaying epithelial-to-mesenchymal transition (EMT) and enhanced invasion and growth in CRC cells. Consistent with this, FGF8 can also promote tumor growth and metastasis in mouse models. Bioinformatics and pathological analysis suggested that YAP1 is a potential downstream target of FGF8 in CRC cells. Molecular validation demonstrated that FGF8 fully induced nuclear localization of YAP1 and enhanced transcriptional outcomes such as the expression of CTGF and CYR61, while decreasing YAP1 expression impeded FGF-8–induced cell growth, EMT, migration and invasion, revealing that YAP1 is required for FGF8-mediated CRC growth and metastasis. Taken together, these results demonstrate that FGF8 contributes to the proliferative and metastatic capacity of CRC cells and may represent a novel candidate for intervention in tumor growth and metastasis formation.

The Fibroblast Growth Factor signaling pathway

The signaling component of the mammalian Fibroblast Growth Factor (FGF) family is comprised of eighteen secreted proteins that interact with four signaling tyrosine kinase FGF receptors (FGFRs). Interaction of FGF ligands with their signaling receptors is regulated by protein or proteoglycan cofactors and by extracellular binding proteins. Activated FGFRs phosphorylate specific tyrosine residues that mediate interaction with cytosolic adaptor proteins and the RAS-MAPK, PI3K-AKT, PLCγ, and STAT intracellular signaling pathways. Four structurally related intracellular non-signaling FGFs interact with and regulate the family of voltage gated sodium channels. Members of the FGF family function in the earliest stages of embryonic development and during organogenesis to maintain progenitor cells and mediate their growth, differentiation, survival, and patterning. FGFs also have roles in adult tissues where they mediate metabolic functions, tissue repair, and regeneration, often by reactivating developmental signaling pathways. Consistent with the presence of FGFs in almost all tissues and organs, aberrant activity of the pathway is associated with developmental defects that disrupt organogenesis, impair the response to injury, and result in metabolic disorders, and cancer. For further resources related to this article, please visit the WIREs website.

The FGFR/MEK/ERK/brachyury pathway is critical for chordoma cell growth and survival

Recent evidence suggests that the expression of brachyury is necessary for chordoma growth. However, the mechanism associated with brachyury-regulated cell growth is poorly understood. Fibroblast growth factor (FGF), a regulator of brachyury expression in normal tissue, may also play an important role in chordoma pathophysiology. Using a panel of chordoma cell lines, we explored the role of FGF signaling and brachyury in cell growth and survival. Western blots showed that all chordoma cell lines expressed fibroblast growth factor receptor 2 (FGFR2), FGFR3, mitogen-activated protein kinase kinase (MEK) and extracellular signal-regulated kinase (ERK), whereas no cell lines expressed FGFR1 and FGFR4. Results of enzyme-linked immunosorbent assay indicated that chordoma cells produced FGF2. Neutralization of FGF2 inhibited MEK/ERK phosphorylation, decreased brachyury expression and induced apoptosis while reducing cell growth. Activation of the FGFR/MEK/ERK/brachyury pathway by FGF2-initiated phosphorylation of FGFR substrate 2 (FRS2)-α (Tyr196) prevented apoptosis while promoting cell growth and epithelial-mesenchymal transition (EMT). Immunofluorescence staining showed that FGF2 promoted the translocation of phosphorylated ERK to the nucleus and increased brachyury expression. The selective inhibition of FGFR, MEK and ERK phosphorylation by PD173074, PD0325901 and PD184352, respectively, decreased brachyury expression, induced apoptosis, and inhibited cell growth and EMT. Moreover, knockdown of brachyury by small hairpin RNA reduced FGF2 secretion, inhibited FGFR/MEK/ERK phosphorylation and blocked the effects of FGF2 on cell growth, apoptosis and EMT. Those findings highlight that FGFR/MEK/ERK/brachyury pathway coordinately regulates chordoma cell growth and survival and may represent a novel chemotherapeutic target for chordoma.

The FGF/FGFR axis as a therapeutic target in breast cancer

Fibroblast growth factor receptor (FGFR) signaling is a vital component of both embryonic and postnatal mammary gland development, which has prompted researchers to investigate both its relevance to breast cancer and its potential as a therapeutic target. Deregulated FGFR signaling during breast cancer occurs through various mechanisms, including amplification of the receptor genes, aberrant ligand expression, receptor mutations and translocations. Recent experimental outcomes involving both animal models and human breast cancer cell lines have led to the initiation of multiple early clinical trials investigating the safety and efficacy of small molecule FGFR inhibitors. In this article we review both the most recent discoveries and the need for further investigation of the mechanisms through which FGF/FGFR signaling has emerged as an oncogenic driver.

Combinatorial targeting of FGF and ErbB receptors blocks growth and metastatic spread of breast cancer models

Introduction

Targeting receptor tyrosine kinases (RTKs) with kinase inhibitors is a clinically validated anti-cancer approach. However, blocking one signaling pathway is often not sufficient to cause tumor regression and the effectiveness of individual inhibitors is often short-lived. As alterations in fibroblast growth factor receptor (FGFR) activity have been implicated in breast cancer, we examined in breast cancer models with autocrine FGFR activity the impact of targeting FGFRs in vivo with a selective kinase inhibitor in combination with an inhibitor of PI3K/mTOR or with a pan-ErbB inhibitor.

Methods

Using 4T1 or 67NR models of basal-like breast cancer, tumor growth was measured in mice treated with an FGFR inhibitor (dovitinib/TKI258), a PI3K/mTOR inhibitor (NVP-BEZ235) or a pan-ErbB inhibitor (AEE788) individually or in combination. To uncover mechanisms underlying inhibitor action, signaling pathway activity was examined in tumor lysates and transcriptome analysis carried out to identify pathways upregulated by FGFR inhibition. Anti-phosphotyrosine receptor antibody arrays (P-Tyr RTK) were also used to screen 4T1 tumors.

Results

The combination of dovitinib + NVP-BEZ235 causes tumor stasis and strong down-regulation of the FRS2/Erk and PI3K/Akt/mTOR signaling pathways. P-Tyr RTK arrays identified high levels of P-EGFR and P-ErbB2 in 4T1 tumors. Testing AEE788 in the tumor models revealed that the combination of dovitinib + AEE788 resulted in blockade of the PI3K/Akt/mTOR pathway, prolonged tumor stasis and in the 4T1 model, a significant decrease in lung metastasis. The results show that in vivo these breast cancer models become dependent upon co-activation of FGFR and ErbB receptors for PI3K pathway activity.

Conclusions

The work presented here shows that in the breast cancer models examined, the combination of dovitinib + NVP-BEZ235 or dovitinib + AEE788 results in strong inhibition of tumor growth and a block in metastatic spread. Only these combinations strongly down-regulate the FGFR/FRS2/Erk and PI3K/Akt/mTOR signaling pathways. The resultant decrease in mitosis and increase in apoptosis was consistently stronger in the dovitinib + AEE788 treatment-group, suggesting that targeting ErbB receptors has broader downstream effects compared to targeting only PI3K/mTOR. Considering that sub-classes of human breast tumors co-express ErbB receptors and FGFRs, these results have implications for targeted therapy.

Identification of fibroblast growth factor-8b target genes associated with early and late cell cycle events in breast cancer cells

Fibroblast growth factor-8 (FGF-8) is implicated in the development and progression of breast cancer and its levels are frequently elevated in breast tumors. The mechanisms driving FGF-8-mediated tumorigenesis are not well understood. Herein we aimed to identify target genes associated with FGF-8b-mediated breast cancer cell proliferation by carrying out a cDNA microarray analysis of genes expressed in estrogen receptor negative S115 breast cancer cells treated with FGF-8b for various time periods in comparison with those expressed in non-treated cells. Gene and protein expression was validated for selected genes by qPCR and western blotting respectively. Furthermore, using TRANSBIG data, the expression of human orthologs of FGF-8-regulated genes was correlated to the Nottingham prognostic index and estrogen receptor status. The analysis revealed a number of significantly up- and down-regulated genes in response to FGF-8b at all treatment times. The most differentially expressed genes were genes related to cell cycle regulation, mitosis, cancer, and cell death. Several key regulators of early cell cycle progression such as Btg2 and cyclin D1, as well as regulators of mitosis, including cyclin B, Plk1, survivin, and aurora kinase A, were identified as novel targets for FGF-8b, some of which were additionally shown to correlate with prognosis and ER status in human breast cancer. The results suggest that in stimulation of proliferation FGF-8b not only promotes cell cycle progression through the G1 restriction point but also regulates key proteins involved in chromosomal segregation during mitosis and cytokinesis of breast cancer cells.

Phage displayed peptides/antibodies recognizing growth factors and their tyrosine kinase receptors as tools for anti-cancer therapeutics

The basic idea of displaying peptides on a phage, introduced by George P. Smith in 1985, was greatly developed and improved by McCafferty and colleagues at the MRC Laboratory of Molecular Biology and, later, by Barbas and colleagues at the Scripps Research Institute. Their approach was dedicated to building a system for the production of antibodies, similar to a naïve B cell repertoire, in order to by-pass the standard hybridoma technology that requires animal immunization. Both groups merged the phage display technology with an antibody library to obtain a huge number of phage variants, each of them carrying a specific antibody ready to bind its target molecule, allowing, later on, rare phage (one in a million) to be isolated by affinity chromatography. Here, we will briefly review the basis of the technology and the therapeutic application of phage-derived bioactive molecules when addressed against key players in tumor development and progression: growth factors and their tyrosine kinase receptors.

Mechanisms of FGFR-mediated carcinogenesis

In this review, the evidence for a role of fibroblast growth factor receptor (FGFR) mediated signalling in carcinogenesis are considered and relevant underlying mechanisms highlighted. FGF signalling mediated by FGFR follows a classic receptor tyrosine kinase signalling pathway and its deregulation at various points of its cascade could result in malignancy. Here we review the accumulating reports that revealed the association of FGF/FGFRs to various types of cancer at a genetic level, along with in vitro and in vivo evidences available so far, which indicates the functional involvement of FGF signalling in tumour formation and progression. An increasing number of drugs against the FGF pathways is currently in clinical testing. We will discuss the strategies for future FGF research in cancer and translational approaches.

Semi-synthetic heparinoids

New chemical-enzymatic technology based on the modification of the bacterial polysaccharide K5 from Escherichia coli leads to the synthesis of a number of heparin/heparan sulfate-like molecules with different biological activities. With this technology, two families of sulfated compounds were synthesized, which differ in their uronic acid content. The first group contains only glucuronic acid, whereas the second group contains about 50% iduronic acid following epimerization by immobilized recombinant C5 epimerase. This has led to the development of various anticoagulant and nonanticoagulant K5 derivatives endowed with different - and sometimes highly specific - antitumor, antiviral, and/or anti-inflammatory activities.

Fibroblast growth factors and their receptors in cancer

FGFs (fibroblast growth factors) and their receptors (FGFRs) play essential roles in tightly regulating cell proliferation, survival, migration and differentiation during development and adult life. Deregulation of FGFR signalling, on the other hand, has been associated with many developmental syndromes, and with human cancer. In cancer, FGFRs have been found to become overactivated by several mechanisms, including gene amplification, chromosomal translocation and mutations. FGFR alterations are detected in a variety of human cancers, such as breast, bladder, prostate, endometrial and lung cancers, as well as haematological malignancies. Accumulating evidence indicates that FGFs and FGFRs may act in an oncogenic fashion to promote multiple steps of cancer progression by inducing mitogenic and survival signals, as well as promoting epithelial-mesenchymal transition, invasion and tumour angiogenesis. Therapeutic strategies targeting FGFs and FGFRs in human cancer are therefore currently being explored. In the present review we will give an overview of FGF signalling, the main FGFR alterations found in human cancer to date, how they may contribute to specific cancer types and strategies for therapeutic intervention.

Functional interaction of fibroblast growth factor-8, bone morphogenetic protein and estrogen receptor in breast cancer cell proliferation

Estrogen is involved in the development and progression of breast cancer. Here we investigated the effect of fibroblast growth factor (FGF)-8 on breast cancer cell proliferation caused by estrogen using human breast cancer MCF-7 cells. MCF-7 cells express estrogen receptor (ER)α, ERβ, FGF receptors, and Smad signaling molecules. Estradiol stimulated MCF-7 cell proliferation in a concentration-responsive manner, whereas BSA-bound estradiol had a weak effect on MCF-7 cell mitosis compared with the effect of free estradiol. It is notable that estrogen-induced cell proliferation was enhanced in the presence of FGF-8 and that the combined effects were reversed in the presence of an FGF-receptor kinase inhibitor or an ER antagonist. It was also revealed that FGF-8 increased the expression levels of ERα, ERβ and aromatase mRNAs, while estradiol reduced the expression levels of ERs, aromatase and steroid sulfatase in MCF-7 cells. FGF-8-induced phosphorylation of FGF receptors was augmented by estradiol, which was reversed by an ER antagonist. FGF-8-induced activation of MAPKs and AKT signaling was also upregulated in the presence of estrogen. On the other hand, FGF-8 suppressed BMP-7 actions that are linked to mitotic inhibition by activating the cell cycle regulator cdc2. FGF-8 was revealed to inhibit BMP receptor actions including Id-1 promoter activity and Smad1/5/8 phosphorylation by suppressing expression of BMP type-II receptors and by increasing expression of inhibitory Smads. Collectively, the results indicate that FGF-8 acts to facilitate cell proliferation by upregulating endogenous estrogenic actions as well as by suppressing BMP receptor signaling in ER-expressing breast cancer cells.

Stromal activation associated with development of prostate cancer in prostate-targeted fibroblast growth factor 8b transgenic mice

Expression of fibroblast growth factor 8 (FGF-8) is commonly increased in prostate cancer. Experimental studies have provided evidence that it plays a role in prostate tumorigenesis and tumor progression. To study how increased FGF-8 affects the prostate, we generated and analyzed transgenic (TG) mice expressing FGF-8b under the probasin promoter that targets expression to prostate epithelium. Prostates of the TG mice showed an increased size and changes in stromal and epithelial morphology progressing from atypia and prostatic intraepithelial neoplasia (mouse PIN, mPIN) lesions to tumors with highly variable phenotype bearing features of adenocarcinoma, carcinosarcoma, and sarcoma. The development of mPIN lesions was preceded by formation of activated stroma containing increased proportion of fibroblastic cells, rich vasculature, and inflammation. The association between advancing stromal and epithelial alterations was statistically significant. Microarray analysis and validation with quantitative polymerase chain reaction revealed that expression of osteopontin and connective tissue growth factor was markedly upregulated in TG mouse prostates compared with wild type prostates. Androgen receptor staining was decreased in transformed epithelium and in hypercellular stroma but strongly increased in the sarcoma-like lesions. In conclusion, our data demonstrate that disruption of FGF signaling pathways by increased epithelial production of FGF-8b leads to strongly activated and atypical stroma, which precedes development of mPIN lesions and prostate cancer with mixed features of adenocarcinoma and sarcoma in the prostates of TG mice. The results suggest that increased FGF-8 in human prostate may also contribute to prostate tumorigenesis by stromal activation.

Roles of fibroblast growth factor receptors in carcinogenesis

The fibroblast growth factor receptors (FGFR) play essential roles both during development and in the adult. Upon ligand binding, FGFRs induce intracellular signaling networks that tightly regulate key biological processes, such as cell proliferation, survival, migration, and differentiation. Deregulation of FGFR signaling can thus alter tissue homeostasis and has been associated with several developmental syndromes as well as with many types of cancer. In human cancer, FGFRs have been found to be deregulated by multiple mechanisms, including aberrant expression, mutations, chromosomal rearrangements, and amplifications. In this review, we will give an overview of the main FGFR alterations described in human cancer to date and discuss their contribution to cancer progression.

Mammary gland growth factors: roles in normal development and in cancer

Normal development of the mammary gland proceeds via interactions between the epithelium and the mesenchyme that start during embryogenesis and continue during pubertal outgrowth and differentiation. The function of specific peptide growth factors that bind members of the receptor tyrosine kinase family and the cytokine receptor family are required at each stage. In many cases the peptides are produced in one compartment and act on receptors in the other compartment. One of the striking differences between normal development and cancer is the loss of this cross-talk. Mammary tumor cells often produce a peptide and express the receptor on the same cell leading to autocrine activation of signaling pathways, a mechanism that is characteristic for cancer cells. We will discuss different peptides in the context of normal development and cancer in this review.

Incisor degeneration in rats induced by vascular endothelial growth factor/fibroblast growth factor receptor tyrosine kinase inhibition

BMS-645737, an inhibitor of vascular endothelial growth factor (VEGF) receptor-2 and fibroblast growth factor (FGF) receptor-1, has anti-angiogenic activity and was evaluated in nonclinical studies as a treatment for cancer. This article characterizes the BMS-645737-induced clinical, gross, and histologic lesions of incisor teeth in Sprague-Dawley (SD) rats. Rats received 0 800 mg/kg BMS-645737 in a single-dose study or consecutive daily doses of 0 20 mg/kg/day in a 1-month study. The reversibility of these effects was assessed in the 1-month study. White discoloration and fracture of incisors were observed clinically and grossly in the 1-month study. In both studies, dose-dependent histopathologic lesions of incisors were degeneration and/or necrosis of odontoblasts and ameloblasts; decreased mineralization of dentin; inflammation and necrosis of the dental pulp; and edema, congestion, and hemorrhage in the pulp and periodontal tissue adjacent to the enamel organ. Partial recovery was observed at lower doses after a two-week dose-free period in the one-month study. Drug-induced incisor lesions were considered to be related to the pharmacologic inhibitory effects on VEGF and FGF signaling, that is, inhibition of growth and maintenance of small-diameter vessels that support the formation of dentin and enamel in growing teeth and/or to perturbances of function of odontoblasts and ameloblasts or their precursors.

Zebrafish Hagoromo mutants up-regulate fgf8 postembryonically and develop neuroblastoma

We screened an existing collection of zebrafish insertional mutants for cancer susceptibility by histologic examination of heterozygotes at 2 years of age. As most mutants had no altered cancer predisposition, this provided the first comprehensive description of spontaneous tumor spectrum and frequency in adult zebrafish. Moreover, the screen identified four lines, each carrying a different dominant mutant allele of Hagoromo previously linked to adult pigmentation defects, which develop tumors with high penetrance and that histologically resemble neuroblastoma. These tumors are clearly neural in origin, although they do not express catecholaminergic neuronal markers characteristic of human neuroblastoma. The zebrafish tumors result from inappropriate maintenance of a cell population within the cranial ganglia that are likely neural precursors. These neoplasias typically remain small but they can become highly aggressive, initially traveling along cranial nerves, and ultimately filling the head. The developmental origin of these tumors is highly reminiscent of human neuroblastoma. The four mutant Hagoromo alleles all contain viral insertions in the fbxw4 gene, which encodes an F-box WD40 domain-containing protein. However, although one allele clearly reduced the levels of fbxw4 mRNA, the other three insertions had no detectable effect on fbw4 expression. Instead, we showed that all four mutations result in the postembryonic up-regulation of the neighboring gene, fibroblast growth factor 8 (fgf8). Moreover, fgf8 is highly expressed in the tumorigenic lesions. Although fgf8 overexpression is known to be associated with breast and prostate cancer in mammals, this study provides the first evidence that fgf8 misregulation can lead to neural tumors.

A neutralizing anti-fibroblast growth factor (FGF) 8 monoclonal antibody shows anti-tumor activity against FGF8b-expressing LNCaP xenografts in androgen-dependent and -independent conditions

BACKGROUND

Fibroblast growth factor 8-isoform b (FGF8b) has been detected in human clinical sex-organ related cancers including hormone-refractory prostate cancer. There are, however, few relevant experimental models. A murine monoclonal anti-FGF8 antibody, KM1334, has been shown to neutralize FGF8b and inhibit the growth of androgen-dependent mouse mammary SC-3 cells in vitro and in vivo. In the present study, we evaluated the anti-tumor activity of KM1334 against androgen-dependent and -independent progression of FGF8b-expressing human prostate cancer xenografts.

METHODS

FGF8b cDNA was transfected into androgen-dependent human prostate cancer cell line LNCaP, and its xenograft tumors were established subcutaneously in SCID mice with or without castration. KM1334 at the dose of 400 microg/head was injected twice weekly.

RESULTS

FGF8b-expressing LNCaP cells secreted FGF8b, showed enhanced level of Erk1/2 phosphorylation, and showed more potent growth properties than mock-expressing cells in vitro and in vivo. KM1334 reduced these properties in vitro, inhibited tumorigenecity in vivo (T/C=0.33), and showed anti-tumor activity against established tumors (T/C=0.47) of FGF8b-expressing cells. FGF8b-expressing LNCaP tumors were androgen-dependent. However, they recurred as androgen-independent FGF8b positive tumors after castration. KM1334 also inhibited the growth of established FGF8b-expressing tumors in the androgen-independent states (T/C=0.47).

CONCLUSIONS

These results indicate that humanized monoclonal antibodies, conserving the paratope of KM1334, are a promising candidate for therapy of FGF8b-expressing clinical prostate cancers. Follow-up studies using xenograft models with clinical FGF8b-expressing tumors are required to validate these early findings.

Targeting FGF19 inhibits tumor growth in colon cancer xenograft and FGF19 transgenic hepatocellular carcinoma models

Although fibroblast growth factor 19 (FGF19) can promote liver carcinogenesis in mice its involvement in human cancer is not well characterized. Here we report that FGF19 and its cognate receptor FGF receptor 4 (FGFR4) are coexpressed in primary human liver, lung and colon tumors and in a subset of human colon cancer cell lines. To test the importance of FGF19 for tumor growth, we developed an anti-FGF19 monoclonal antibody that selectively blocks the interaction of FGF19 with FGFR4. This antibody abolished FGF19-mediated activity in vitro and inhibited growth of colon tumor xenografts in vivo and effectively prevented hepatocellular carcinomas in FGF19 transgenic mice. The efficacy of the antibody in these models was linked to inhibition of FGF19-dependent activation of FGFR4, FRS2, ERK and beta-catenin. These findings suggest that the inactivation of FGF19 could be beneficial for the treatment of colon cancer, liver cancer and other malignancies involving interaction of FGF19 and FGFR4.

FGFs, Wnts and BMPs mediate induction of VEGFR-2 (Quek-1) expression during avian somite development

Regulation of VEGFR-2 (Quek1) is an important mechanism during blood vessel formation. In the paraxial mesoderm, Quek1 expression is restricted to the lateral portion of the somite and later to sclerotomal cells surrounding the neural tube. By implanting FGF 8b/8c or SU 5402 beads into the paraxial mesoderm, we show that FGF8 in addition to BMP4 from the intermediate mesoderm (IM) is a positive regulator of VEGFR-2 (Quek1) expression in the quail embryo. The expression of Quek1 in the medial somite half is normally repressed by the notochord and Sfrps-expression in the neural tube. Over-expression of Wnt 1/3a also results in an up-regulation of Quek1 expression in the somites. We also show that up-regulation of FGF8/Wnt 1/3a leads to an increase in the number of endothelial cells, whereas inhibition of FGF and Wnt signaling by SU 5402 and Sfrp-2 results in a loss of endothelial cells. Our results demonstrate that the regulation of Quek1 expression in the somites is mediated by the cooperative actions of BMP4, FGF8 and Wnt-signaling pathways.

A critical role for the inflammatory response in a mouse model of preneoplastic progression

The tumor microenvironment, which includes inflammatory cells, vasculature, extracellular matrix, and fibroblasts, is a critical mediator of neoplastic progression and metastasis. Using an inducible transgenic mouse model of preneoplastic progression in the mammary gland, we discovered that activation of inducible fibroblast growth factor receptor-1 (iFGFR1) in the mammary epithelium rapidly increased the expression of several genes involved in the inflammatory response. Further analysis revealed that iFGFR1 activation induced recruitment of macrophages to the epithelium and continued association with the alveolar hyperplasias that developed following long-term activation. Studies using HC-11 mammary epithelial cells showed that iFGFR1-induced expression of the macrophage chemoattractant osteopontin was required for macrophage recruitment in vitro. Finally, conditional depletion of macrophages inhibited iFGFR1-mediated epithelial cell proliferation and lateral budding. These findings show that inflammatory cells, specifically macrophages, are critical for mediating early events in an inducible transgenic mouse model of preneoplastic progression.

Functional screen for genes responsible for tamoxifen resistance in human breast cancer cells

Antiestrogens, such as tamoxifen, are widely used for endocrine treatment of estrogen receptor-positive breast cancer. However, as breast cancer progresses, development of tamoxifen resistance is inevitable. The mechanisms underlying this resistance are not well understood. To identify genes involved in tamoxifen resistance, we have developed a rapid screening method. To alter the tamoxifen-sensitive phenotype of human ZR-75-1 breast cancer cells into a tamoxifen-resistant phenotype, the cells were infected with retroviral cDNA libraries derived from human placenta, human brain, and mouse embryo. Subsequently, the cells were selected for proliferation in the presence of 4-hydroxy-tamoxifen (OH-TAM) and integrated cDNAs were identified by sequence similarity searches. From 155 OH-TAM-resistant cell colonies, a total of 25 candidate genes were isolated. Seven of these genes were identified in multiple cell colonies and thus cause antiestrogen resistance. The epidermal growth factor receptor, platelet-derived growth factor receptor-alpha, platelet-derived growth factor receptor-beta, colony-stimulating factor 1 receptor, neuregulin1, and fibroblast growth factor 17 that we have identified have been described as key regulators in the mitogen-activated protein kinase pathway. Therefore, this pathway could be a valuable target in the treatment of patients with breast cancer resistant to endocrine treatment. In addition, the putative gene LOC400500, predicted by in silico analysis, was identified. We showed that ectopic expression of this gene, designated as breast cancer antiestrogen resistance 4 (BCAR4), caused OH-TAM resistance and anchorage-independent cell growth in ZR-75-1 cells and that the intact open reading frame was required for its function. We conclude that retroviral transfer of cDNA libraries into human breast cancer cells is an efficient method for identifying genes involved in tamoxifen resistance.

Androgen and fibroblast growth factor 8 (FGF8) downregulation of thrombospondin 1 (TSP1) in mouse breast cancer cells

In the search for androgen target genes responsible for malignant growth in S115 mouse mammary tumor cells we found that thrombospondin 1 (TSP1) expression was strongly downregulated by testosterone (Te). Experiments with cycloheximide suggested that Te repression of TSP1 was dependent on de novo protein synthesis. TSP1 repression by Te was preceded by the induction of fibroblast growth factor 8 (FGF8) expression. FGF8 has previously been shown to mediate androgen effects on proliferation of S115 cells by autocrine/paracrine mechanisms. It has also been shown to increase breast cancer cell growth as tumors in nude mice and to stimulate tumor angiogenesis. We studied here the possibility that FGF8 belonged to the Te-induced de novo synthesized proteins that mediate the effect of Te on TSP1 expression in these cells. We found that addition of FGF8b to in vitro cultures or ectopic expression of FGF8b in S115 cells repressed TSP1 expression at mRNA and protein levels even in the absence of Te. FGF2, another angiogenic member of FGF family, also downregulated TSP1 mRNA level in the in vitro cultures of S115 cells. The antisense oligonucleotides for FGF8 did not, however, prevent Te-repression of TSP1 mRNA expression and a neutralizing anti-FGF8b antibody only partially opposed Te induced downregulation of TSP1. These results suggest that both androgen and FGF8 inhibit TSP1 expression independently. They also suggest that opposite to many other androgen-induced responses in S115 cells, the effect of Te on the expression TSP1 is not mediated by FGF8.

Vitamin D3 suppresses the androgen-stimulated growth of mouse mammary carcinoma SC-3 cells by transcriptional repression of fibroblast growth factor 8

Active metabolites of vitamin A and D are well known to act as growth inhibitors in hormone-related prostate and breast cancers. When various concentrations of 1alpha,25-dihydroxyvitamin D3 (vitamin D3), all-trans-retinoic acid (ATRA) and 9-cis retinoic acid (9-cis RA) were examined, the androgen-stimulated growth of mouse mammary carcinoma SC-3 cells was inhibited by vitamin D3 alone in a dose-dependent manner. A flow cytometer analysis showed that vitamin D3 leads SC-3 cells to relative G1-growth arrest after 72 h. Characterization of vitamin D3-responsive genes using an oligonucleotide microarray demonstrated that 220 genes were upregulated at more than threefold, and 84 genes were downregulated to less than one-third, compared with the testosterone-stimulated SC-3 cells. Neither cyclin-dependent kinase inhibitors (CDKIs) nor the antiapoptotic bcl-2 gene were induced in vitamin D3-responsive genes, with the exception of a slight induction of p15(INK4B). Importantly, fgf8 was markedly repressed in response to vitamin D3. The exogenous addition of FGF8 canceled the growth suppression by vitamin D3 in SC-3 cells, suggesting that the repression of fgf8 is an indispensable step in vitamin D3-mediated growth inhibition. In reporter assays using the ARE-containing artificial construct and the natural androgen-regulated PSA promoter, co-transfection of the vitamin D receptor (VDR) and androgen receptor (AR) suppressed AR-stimulated promoter activity. In addition, vitamin D3 also suppressed androgen-stimulated promoter activity in the stably transfected SC-3 cells. Moreover, VDR repressed the core promoter activity of fgf8 in COS1 cells and in the SC-3 cells. All these findings strongly suggest that vitamin D3 serves as a negative regulator for both androgen-related and fgf8 transcriptions.

Expression of the fetal-oncogenic fibroblast growth factor-8/17/18 subfamily in human hematopoietic tumors

The fibroblast growth factors (FGFs) are involved in hematopoiesis and tumorigenesis. However, little is known about the contribution of the FGFs identified within the past 10 years to leukemogenesis. To elucidate whether these FGFs (FGF-8, -9, -10, -11, -12, -13, -14, -16, -17, -18, -19, -20, and -21) are expressed in leukemic cells, we performed RT-PCR analyses using 28 cell lines. The members of a fetal-oncogenic subfamily, FGF-8/-17/-18, were often expressed (53.5%, 25.0%, and 32.1%) with the co-expression of their receptors. Realtime quantitative-PCR analysis showed that FGF-8/-17 were aberrantly expressed in patients with acute leukemia. Moreover, cell proliferation assays revealed the proliferation activity of FGF-17 on leukemic cells expressing its receptors. These results demonstrated that certain recently identified FGFs play an important role in the growth of leukemic cells, possibly with an autocrine mode of action, and that these FGFs will become novel biomarkers for hematopoietic tumors.

A neutralizing anti-fibroblast growth factor 8 monoclonal antibody shows potent antitumor activity against androgen-dependent mouse mammary tumors in vivo

PURPOSE

Fibroblast growth factor 8b (FGF8b) has been implicated in oncogenesis of sex hormone-related malignancies. A murine monoclonal anti-FGF8 antibody, KM1334, has been raised against a FGF8b-derived peptide and shown to neutralize FGF8b activity in an androgen-dependent mouse mammary cell line (SC-3) in vitro growth. The purpose of this study was to evaluate KM1334 as a therapeutic agent for FGF8-dependent cancer.

EXPERIMENTAL DESIGN

Specificity and neutralizing activity of KM1334 were examined in vitro. In vivo therapeutic studies were done in nude mice bearing SC-3 tumors s.c.

RESULTS

KM1334 recognized FGF8b and FGF8f specifically out of four human FGF8 isoforms and showed little binding to other members of FGF family. Neutralizing activity of KM1334 was confirmed by both blocking of FGF8b binding to its three receptors (FGFR2IIIc, FGFR3IIIc, and FGFR4) and FGF8b-induced phosphorylation of FGFR substrate 2alpha and extracellular signal-regulated kinase 1/2 in SC-3 cells. The in vitro inhibitory effect could be extended to in vivo tumor models, where KM1334 caused rapid regression of established SC-3 tumors in nude mice. This rapid regression of tumors after KM1334 treatment was explained by two independent mechanisms: (a) decreased DNA synthesis, as evidenced by a decrease in uptake of 5-bromo-2'-deoxyuridine, and (b) induction of apoptosis as shown by the terminal deoxynucleotidyl transferase-mediated nick end labeling assay.

CONCLUSIONS

KM1334 possesses strong blocking activity in vitro and antitumor activity in vivo and therefore may be an effective therapeutic candidate for the treatment of cancers that are dependent on FGF8b signaling for growth and survival.

The ras/mitogen-activated protein kinase pathway inhibitor and likely tumor suppressor proteins, sprouty 1 and sprouty 2 are deregulated in breast cancer

Sprouty (Spry) proteins were found to be endogenous inhibitors of the Ras/mitogen-activated protein kinase pathway that play an important role in the remodeling of branching tissues. We investigated Spry expression levels in various cancers and found that Spry1 and Spry2 were down-regulated consistently in breast cancers. Such prevalent patterns of down-regulation may herald the later application of these isoforms as tumor markers that are breast cancer specific and more profound than currently characterized markers. Spry1 and 2 were expressed specifically in the luminal epithelial cells of breast ducts, with higher expression during stages of tissue remodeling when the epithelial ducts are forming and branching. These findings suggest that Sprys might be involved as a modeling counterbalance and surveillance against inappropriate epithelial expansion. The abrogation of endogenous Spry activity in MCF-7 cells by the overexpression of a previously characterized dominant-negative mutant of Spry, hSpry2Y55F resulted in enhanced cell proliferation in vitro. The hSpry2Y55F stably expressing cells also formed larger and greater number of colonies in the soft-agar assay. An in vivo nude mice assay showed a dramatic increase in the tumorigenic potential of hSpry2Y55F stable cells. The consistent down-regulation of Spry1 and 2 in breast cancer and the experimental evidence using a dominant-negative hSpry2Y55F indicate that Spry proteins may actively maintain tissue integrity that runs amok when their expression is decreased below normal threshold levels. This alludes to a previously unrecognized role for Sprys in cancer development.

Fgf10 is an oncogene activated by MMTV insertional mutagenesis in mouse mammary tumors and overexpressed in a subset of human breast carcinomas

Mouse mammary tumor virus (MMTV) infection causes a high incidence of murine mammary carcinomas by insertion of its proviral DNA in the genome of mammary epithelial cells. Retroviral insertion can activate flanking proto-oncogenes by a process called insertional mutagenesis. By sequencing the DNA adjacent to MMTV proviral insertions in mammary tumors from BALB/c mice infected with C3H-MMTV, we have found a common MMTV insertion site in the Fgf10 locus. RT-PCR studies showed that Fgf10 is expressed only in those tumors harboring a MMTV proviral insertion in this locus, suggesting that Fgf10 is a proto-oncogene. The oncogenicity of Fgf10 was evaluated in vivo by subcutaneous transplantation of retrovirally transduced HC11 mammary epithelial cells into BALB/c mice. Highly vascularized invasive subcutaneous tumors developed indicating that Fgf10 can act as an oncogene. A survey of primary human breast carcinomas revealed strongly elevated Fgf10 mRNA levels in approximately 10% of the tumors tested, suggesting that Fgf10 may also be involved in oncogenicity of a subset of human breast cancers.

Roles of FGF receptors in mammalian development and congenital diseases

Four fibroblast growth factor receptors (FGFR1-4) constitute a family of transmembrane tyrosine kinases that serve as high affinity receptors for at least 22 FGF ligands. Gene targeting in mice has yielded valuable insights into the functions of this important gene family in multiple biological processes. These include mesoderm induction and patterning; cell growth, migration, and differentiation; organ formation and maintenance; neuronal differentiation and survival; wound healing; and malignant transformation. Furthermore, discoveries that mutations in three of the four receptors result in more than a dozen human congenital diseases highlight the importance of these genes in skeletal development. In this review, we will discuss recent progress on the roles of FGF receptors in mammalian development and congenital diseases, with an emphasis on signal transduction pathways.

Heparin/Heparan sulfate domains in binding and signaling of fibroblast growth factor 8b

The role of heparin and heparan sulfate in the binding and signaling of fibroblast growth factors (FGFs) has been subject to intense investigation, but the studies have largely been confined to two species (FGF1 and FGF2) of the family with approximately 20 members. We have investigated the structural requirements for heparin/heparan sulfate in binding and activation of FGF8 (splice variant b). We present evidence that the minimal FGF8b-binding saccharide domain encompasses 5-7 monosaccharide units. The N-, 2-O-, and 6-O-sulfate substituents of heparin/heparan sulfate (HS) are all involved in the interaction, preferentially in the form of trisulfated IdoUA(2-OSO(3))-GlcNSO(3)(6-OSO(3)) disaccharide constituents. These structural characteristics resemble those described earlier for FGF1. By contrast, the saccharide structures required for the biological activity of FGF8b differed significantly from those characteristic for FGF1 and FGF2. Experiments with cells lacking active HS indicated that extended >/=14-mer heparin domains were needed to enhance cell proliferation and Erk phosphorylation by FGF8b, whereas in cells stimulated with FGF1 or FGF2 the corresponding responses were achieved by much shorter, 6-8-mer, oligosaccharides. Furthermore, still longer domains were needed to activate FGF8b in cells with "non-optimal" FGF receptor expression. Collectively, our data suggest that the heparin/HS structures enhancing the biological activity of FGFs were influenced by the FGF species involved as well as by the cellular composition of FGF receptors.

DNA methylation and breast carcinogenesis

Knowledge about breast carcinogenesis has accumulated during the last decades but has barely been translated into strategies for early detection or prevention of this common disease. Changes in DNA methylation have been recognized as one of the most common molecular alterations in human neoplasia and hypermethylation of gene-promoter regions is being revealed as one of the most frequent mechanisms of loss of gene function. The heritability of methylation states and the secondary nature of the decision to attract or exclude methylation support the idea that DNA methylation is adapted for a specific cellular memory. According to Hanahan and Weinberg, there are six novel capabilities a cell has to acquire to become a cancer cell: limitless replicative potential, self-sufficiency in growth signals, insensitivity to growth-inhibitory signals, evasion of programmed cell death, sustained angiogenesis and tissue invasion and metastasis. This review highlights how DNA-methylation contributes to these features and offers suggestions about how these changes could be prevented, reverted or used as a 'tag' for early detection of breast cancer or, preferably, for detection of premalignant changes.

A mouse model of hepatocellular carcinoma: ectopic expression of fibroblast growth factor 19 in skeletal muscle of transgenic mice

Most mouse models of hepatocellular carcinoma have expressed growth factors and oncogenes under the control of a liver-specific promoter. In contrast, we describe here the formation of liver tumors in transgenic mice overexpressing human fibroblast growth factor 19 (FGF19) in skeletal muscle. FGF19 transgenic mice had elevated hepatic alpha-fetoprotein mRNA as early as 2 months of age, and hepatocellular carcinomas were evident by 10 months of age. Increased proliferation of pericentral hepatocytes was demonstrated by 5-bromo-2'-deoxyuridine incorporation in the FGF19 transgenic mice before tumor formation and in nontransgenic mice injected with recombinant FGF19 protein. Areas of small cell dysplasia were initially evident pericentrally, and dysplastic/neoplastic foci throughout the hepatic lobule were glutamine synthetase-positive, suggestive of a pericentral origin. Consistent with chronic activation of the Wingless/Wnt pathway, 44% of the hepatocellular tumors from FGF19 transgenic mice had nuclear staining for beta-catenin. Sequencing of the tumor DNA encoding beta-catenin revealed point mutations that resulted in amino acid substitutions. These findings suggest a previously unknown role for FGF19 in hepatocellular carcinomas.

Inducible dimerization of FGFR1: development of a mouse model to analyze progressive transformation of the mammary gland

To develop an inducible and progressive model of mammary gland tumorigenesis, transgenic mice were generated with a mouse mammary tumor virus-long terminal repeat-driven, conditional, fibroblast growth factor (FGF)-independent FGF receptor (FGFR)1 (iFGFR1) that can be induced to dimerize with the drug AP20187. Treatment of transgenic mice with AP20187 resulted in iFGFR1 tyrosine phosphorylation, increased proliferation, activation of mitogen-activated protein kinase and Akt, and lateral budding. Lateral buds appeared as early as 3 d after AP20187 treatment and initially consisted of bilayered epithelial cells and displayed apical and basolateral polarity appeared after 13 d of AP20187 treatment. Invasive lesions characterized by multicell-layered lateral buds, decreased myoepithelium, increased vascular branching, and loss of cell polarity were observed after 2-4 wk of treatment. These data indicate that acute iFGFR1 signaling results in increased lateral budding of the mammary ductal epithelium, and that sustained activation induces alveolar hyperplasia and invasive lesions.

Fibroblast growth factor 8 is expressed at higher levels in lactating human breast and in breast cancer

Fibroblast growth factor 8 can transform NIH3T3 cells and its expression has been found to be associated with breast and prostate cancer. Following our finding that fibroblast growth factor 8 mRNA expression is increased in breast cancer, we have undertaken an immunohistochemistry study of fibroblast growth factor 8 expression in a series of human breast tissues and other normal tissues. Our findings confirm increased expression of fibroblast growth factor 8 in malignant breast tissue but also show significant fibroblast growth factor 8 expression in non-malignant breast epithelial cells. No significant difference in fibroblast growth factor 8 expression was found between different grades of ductal carcinoma, lobular carcinoma and ductal carcinoma in-situ or cancer of different oestrogen receptor, progesterone receptor or nodal status. The highest levels of fibroblast growth factor 8 expression were found in lactating breast tissues and fibroblast growth factor 8 was also detected in human milk. A survey of other normal tissues showed that fibroblast growth factor 8 is expressed in the proliferative cells of the dermis and epithelial cells in colon, ovary fallopian tube and uterus. Fibroblast growth factor 8 appears to be expressed in several organs in man and appears to have an importance in lactation.

Fibroblast growth factor receptor (FGFR) 4 correlated with the malignancy of human astrocytomas

Fibroblast growth factor receptor (FGFR) 4 possesses high affinity to acidic and basic fibroblast growth factors (FGFs). The authors focused on FGFR 4 expression in astrocytoma because the FGF expression increases as the tumor malignancy progresses. Forty-one astrocytoma specimens were examined by immunohistochemistry and polymerase chain reaction-Southern blot. FGFR 4 was negative in all seven Grade II astrocytomas by immunohistochemistry, while positive in four among 15 Grade III and in 13 among 19 Grade IV astrocytomas. The median survival time of Grade III astrocytoma patients was 22.3 months in FGFR 4 negative group and 14.5 months in positive group (p < 0.05). Those of Grade IV patients were 14.2 months in FGFR 4 negative group and 11.9 months in positive group (p > 0.05, not significant). However, FGFR 4 mRNA was detected in all specimens suggesting activated translation system of FGFR 4 in progression of the tumor malignancy. Histologically diagnosed Grade III astrocytoma patients can be divided into two groups; one with median survival time close to those with Grade II astrocytoma patients, and the other similar to that of glioblastoma patients. The authors concluded that FGFR 4 must be an important factor which predicts short survival Grade III astrocytoma patients, who require strict adjuvant therapy in accordance with glioblastoma.

Wnt-1 and int-2 mammary oncogene effects on the beta-catenin pathway in immortalized mouse mammary epithelial cells are not sufficient for tumorigenesis

Development of strategies for prevention of breast cancer development requires an understanding of the effects of mammary oncogenes on mammary cells at early stages in neoplastic transformation. As mammary oncogenes wnt-1 and int-2 affect different signal transduction pathways, we investigated their effects on established mouse mammary epithelial cell lines (MMECLs) reflecting early stages in tumorigenesis. Normal interactions between beta-catenin and E-cadherin were abrogated in all three immortalized MMECLs and the cells lacked beta-catenin-mediated transactivation activity, detectable using a reporter assay, suggesting that alterations in cell adhesion may be very early events in mammary tumorigenesis. Immortalized FSK4 and EL12 cells and hyperplastic TM3 cells were stably transfected with expression vectors encoding wnt-1 or int-2 or the control vector, and drug-selected pooled cells from each line were confirmed by reverse transcription-polymerase chain reaction to express the transfected oncogene; this expression persisted in the cells analysed in vitro and in vivo. Resultant phenotypic changes depended both on the oncogene and the target mammary cell line. In FSK4 cells, expression of wnt-1 or int-2 resulted in proliferative changes in vitro, including reduced contact inhibition, increased beta-catenin expression, and decreased p53 transcriptional activity, but neither oncogene conferred upon those cells the ability to produce tumors in vivo. EL12 cells were highly refractory to the effects of both oncogenes, with the only measurable changes being increased E-cadherin levels induced by both oncogenes and increased proliferation of the int-2-transfected cells in the absence of serum. Parental TM3 cells were phenotypically similar to wnt-1- or int-2-transfected FSK4 cells and displayed an increased rate of proliferation in vitro and markedly increased tumorigenicity in vivo following transfection with int-2 but not with wnt-1. These results suggest that wnt-1 signaling is redundant in the hyperplastic TM3 cells and indicate that wnt-1-induced effects in the immortalized FSK4 and EL12 cells were not sufficient to mediate a tumorigenic phenotype. This study showed that the wnt-1 and int-2 oncogenes have similar but distinguishable effects on immortalized MMECLs and that the genetic background of the mammary cells greatly influences the consequences of oncogene expression at early stages of cell transformation.

Mechanisms of estrogen action

Our appreciation of the physiological functions of estrogens and the mechanisms through which estrogens bring about these functions has changed during the past decade. Just as transgenic mice were produced in which estrogen receptors had been inactivated and we thought that we were about to understand the role of estrogen receptors in physiology and pathology, it was found that there was not one but two distinct and functional estrogen receptors, now called ER alpha and ER beta. Transgenic mice in which each of the receptors or both the receptors are inactive have revealed a much broader role for estrogens in the body than was previously thought. This decade also saw the description of a male patient who had no functional ER alpha and whose continued bone growth clearly revealed an important function of estrogen in men. The importance of estrogen in both males and females was also demonstrated in the laboratory in transgenic mice in which the aromatase gene was inactivated. Finally, crystal structures of the estrogen receptors with agonists and antagonists have revealed much about how ligand binding influences receptor conformation and how this conformation influences interaction of the receptor with coactivators or corepressors and hence determines cellular response to ligands.

Proteoglycans: pericellular and cell surface multireceptors that integrate external stimuli in the mammary gland

Proteoglycans consist of a core protein and an associated glycosaminoglycan (GAG) chain of heparan sulfate, chondroitin sulfate, dermatan sulfate or keratan sulfate, which are attached to a serine residue. The core proteins of cell surface proteoglycans may be transmembrane, e.g., syndecan, or GPI-anchored, e.g., glypican. Many different cell surface and matrix proteoglycan core proteins are expressed in the mammary gland and in mammary cells in culture. The level of expression of these core proteins, the structure of their GAG chains, and their degradation are regulated by many of the effectors that control the development and function of the mammary gland. Regulatory proteins of the mammary gland that bind GAG include many growth factors and morphogens (fibroblast growth factors, hepatocyte growth factor/scatter factor, members of the midkine family, wnts), matrix proteins (collagen, fibronectin, and laminin), enzymes (lipoprotein lipase) and microbial surface proteins. Structural diversity within GAG chains ensures that each protein-GAG interaction is as specific as necessary and a number of sequences of saccharides that recognize individual proteins have been elucidated. The GAG-protein interactions serve to regulate the signal output of growth factor receptor tyrosine kinase and hence cell fate as well as the storage and diffusion of extracellular protein effectors. In addition, GAGs clearly coordinate stromal and epithelial development, and they are active participants in mediating cell-cell and cell-matrix interactions. Since a single proteoglycan, even if it carries a single GAG chain, can bind multiple proteins, proteoglycans are also likely to act as multireceptors which promote the integration of cellular signals.