Cloning and characterization of an androgen-induced growth factor essential for the androgen-dependent growth of mouse mammary carcinoma cells

Proteomics and Bioinformatics Investigations Link Overexpression of FGF8 and Associated Hub Genes to the Progression of Ovarian Cancer and Poor Prognosis

Ovarian cancer's asymptomatic nature, high recurrence rate, and resistance to platinum-based chemotherapy highlight the need to find and characterize new diagnostic and therapeutic targets. While prior studies have linked aberrant expression of fibroblast growth factor 8 (FGF8) to various cancer types, its precise role has remained elusive. Recently, we observed that FGF8 silencing reduces the cancer-promoting properties of ovarian cancer cells, and thus, this study aimed to understand how FGF8 regulates the development of ovarian cancer. LC-MS/MS-based quantitative proteomics analysis identified 418 DEPs, and most of them were downregulated in FGF8-silenced ovarian cancer cells. Many of these DEPs are associated with cancer progression and unfavorable prognosis. To decipher the biological significance of DEPs, bioinformatics analyses encompassing gene ontology, pathway analysis, protein-protein interaction networks, and expression analysis of hub genes were carried out. Hub genes identified in the FGF8 protein network were upregulated in ovarian cancer compared to controls and were linked to poor prognosis. Subsequently, the expression of hub genes was correlated with patient survival and regulation of the tumor microenvironment. Conclusively, FGF8 and associated hub genes help in the progression of ovarian cancer, and their overexpression may lead to higher immune infiltration, poor prognosis, and poor survival.

Real-time monitoring of an endogenous Fgf8a gradient attests to its role as a morphogen during zebrafish gastrulation

Morphogen gradients impart positional information to cells in a homogenous tissue field. Fgf8a, a highly conserved growth factor, has been proposed to act as a morphogen during zebrafish gastrulation. However, technical limitations have so far prevented direct visualization of the endogenous Fgf8a gradient and confirmation of its morphogenic activity. Here, we monitor Fgf8a propagation in the developing neural plate using a CRISPR/Cas9-mediated EGFP knock-in at the endogenous fgf8a locus. By combining sensitive imaging with single-molecule fluorescence correlation spectroscopy, we demonstrate that Fgf8a, which is produced at the embryonic margin, propagates by diffusion through the extracellular space and forms a graded distribution towards the animal pole. Overlaying the Fgf8a gradient curve with expression profiles of its downstream targets determines the precise input-output relationship of Fgf8a-mediated patterning. Manipulation of the extracellular Fgf8a levels alters the signaling outcome, thus establishing Fgf8a as a bona fide morphogen during zebrafish gastrulation. Furthermore, by hindering Fgf8a diffusion, we demonstrate that extracellular diffusion of the protein from the source is crucial for it to achieve its morphogenic potential.

Unveiling the Significance of FGF8 Overexpression in Orchestrating the Progression of Ovarian Cancer

The asymptomatic nature, high rate of disease recurrence, and resistance to platinum-based chemotherapy highlight the need to identify and characterize novel target molecules for ovarian cancer. Fibroblast growth factor 8 (FGF8) aids in the development and metastasis of ovarian cancer; however, its definite role is not clear. We employed ELISA and IHC to examine the expression of FGF8 in the saliva and tissue samples of epithelial ovarian cancer (EOC) patients and controls. Furthermore, various cell assays were conducted to determine how FGF8 silencing influences ovarian cancer cell survival, adhesion, migration, and invasion to learn more about the functions of FGF8. In saliva samples, from controls through low-grade to high-grade EOC, a stepped overexpression of FGF8 was observed. Similar expression trends were seen in tissue samples, both at protein and mRNA levels. FGF8 gene silencing in SKOV3 cells adversely affected various cell properties essential for cancer cell survival and metastasis. A substantial reduction was observed in the cell survival, cell adhesion to the extracellular matrix, migration, and adhesion properties of SKOV3 cells, suggesting that FGF8 plays a crucial role in the development of EOC. Conclusively, this study suggests a pro-metastatic function of FGF8 in EOC.

Fibroblast growth factor 8 facilitates cell-cell communication in chondrocytes via p38-MAPK signaling

Gap junction intercellular communication (GJIC) is essential for regulating the development of the organism and sustaining the internal environmental homeostasis of multi-cellular tissue. Fibroblast growth factor 8 (FGF8), an indispensable regulator of the skeletal system, is implicated in regulating chondrocyte growth, differentiation, and disease occurrence. However, the influence of FGF8 on GJIC in chondrocytes is not yet known. The study aims to investigate the role of FGF8 on cell-cell communication in chondrocytes and its underlying biomechanism. We found that FGF8 facilitated cell-cell communication in living chondrocytes by the up-regulation of connexin43 (Cx43), the major fundamental component unit of gap junction channels in chondrocytes. FGF8 activated p38-MAPK signaling to increase the expression of Cx43 and promote the cell-cell communication. Inhibition of p38-MAPK signaling impaired the increase of Cx43 expression and cell-cell communication induced by FGF8, indicating the importance of p38-MAPK signaling. These results help to understand the role of FGF8 on cell communication and provide a potential cue for the treatment of cartilage diseases.

Immunoreactivity against fibroblast growth factor 8 in alveolar rhabdomyosarcoma patients and its involvement in tumor aggressiveness

Rhabdomyosarcoma (RMS) is an aggressive pediatric soft tissue sarcoma characterized by a very poor prognosis when relapses occur after front-line therapy. Therefore, a major challenge for patients’ management remains the identification of markers associated with refractory and progressive disease. In this context, cancer autoantibodies are natural markers of disease onset and progression, useful to unveil novel therapeutic targets. Herein, we matched autoantibody profiling of alveolar RMS (ARMS) patients with genes under regulatory control of PAX3-FOXO1 transcription factor and revealed fibroblast growth factor 8 (FGF8) as a novel ARMS tumor antigen of diagnostic, prognostic, and therapeutic potential. We demonstrated that high levels of FGF8 autoantibodies distinguished ARMS patients from healthy subjects and represented an independent prognostic factor of better event-free survival. FGF8 was overexpressed in ARMS tumors compared to other types of pediatric soft tissue sarcomas, acting as a positive regulator of cell signaling. Indeed, FGF8 was capable of stimulating ARMS cells migration and expression of pro-angiogenic and metastasis-related factors, throughout MAPK signaling activation. Of note, FGF8 was found to increase in recurrent tumors, independently of PAX3-FOXO1 expression dynamics. Risk of recurrence correlated positively with FGF8 expression levels at diagnosis and reduced FGF8 autoantibodies titer, almost as if to suggest a failure of the immune response to control tumor growth in recurring patients. This study provides evidence about the crucial role of FGF8 in ARMS and the protective function of natural autoantibodies, giving new insights into ARMS biology and laying the foundations for the development of new therapeutic strategies.

An Update on the Molecular Mechanism of the Vertebrate Isthmic Organizer Development in the Context of the Neuromeric Model

A crucial event during the development of the central nervous system (CNS) is the early subdivision of the neural tube along its anterior-to-posterior axis to form neuromeres, morphogenetic units separated by transversal constrictions and programed for particular genetic cascades. The narrower portions observed in the developing neural tube are responsible for relevant cellular and molecular processes, such as clonal restrictions, expression of specific regulatory genes, and differential fate specification, as well as inductive activities. In this developmental context, the gradual formation of the midbrain-hindbrain (MH) constriction has been an excellent model to study the specification of two major subdivisions of the CNS containing the mesencephalic and isthmo-cerebellar primordia. This MH boundary is coincident with the common Otx2-(midbrain)/Gbx2-(hindbrain) expressing border. The early interactions between these two pre-specified areas confer positional identities and induce the generation of specific diffusible morphogenes at this interface, in particular FGF8 and WNT1. These signaling pathways are responsible for the gradual histogenetic specifications and cellular identity acquisitions with in the MH domain. This review is focused on the cellular and molecular mechanisms involved in the specification of the midbrain/hindbrain territory and the formation of the isthmic organizer. Emphasis will be placed on the chick/quail chimeric experiments leading to the acquisition of the first fate mapping and experimental data to, in this way, better understand pioneering morphological studies and innovative gain/loss-of-function analysis.

New Insights in the Interaction of FGF/FGFR and Steroid Receptor Signaling in Breast Cancer

Luminal breast cancer (BrCa) has a favorable prognosis compared with other tumor subtypes. However, with time, tumors may evolve and lead to disease progression; thus, there is a great interest in unraveling the mechanisms that drive tumor metastasis and endocrine resistance. In this review, we focus on one of the many pathways that have been involved in tumor progression, the fibroblast growth factor/fibroblast growth factor receptor (FGFR) axis. We emphasize in data obtained from in vivo experimental models that we believe that in luminal BrCa, tumor growth relies in a crosstalk with the stromal tissue. We revisited the studies that illustrate the interaction between hormone receptors and FGFR. We also highlight the most frequent alterations found in BrCa cell lines and provide a short review on the trials that use FGFR inhibitors in combination with endocrine therapies. Analysis of these data suggests there are many players involved in this pathway that might be also targeted to decrease FGF signaling, in addition to specific FGFR inhibitors that may be exploited to increase their efficacy.

Potential biomarkers and signaling pathways associated with the pathogenesis of primary salivary gland carcinoma: a bioinformatics study

Salivary gland carcinoma (SGC) is rare cancer, constituting 6% of neoplasms in the head and neck area. The most responsible genes and pathways involved in the pathology of this disorder have not been fully understood. We aimed to identify differentially expressed genes (DEGs), the most critical hub genes, transcription factors, signaling pathways, and biological processes (BPs) associated with the pathogenesis of primary SGC. The mRNA dataset GSE153283 in the Gene Expression Omnibus database was re-analyzed for determining DEGs in cancer tissue of patients with primary SGC compared to the adjacent normal tissue (adjusted p-value < 0.001; |Log2 fold change| > 1). A protein interaction map (PIM) was built, and the main modules within the network were identified and focused on the different pathways and BP analyses. The hub genes of PIM were discovered, and their associated gene regulatory network was built to determine the master regulators involved in the pathogenesis of primary SGC. A total of 137 genes were found to be differentially expressed in primary SGC. The most significant pathways and BPs that were deregulated in the primary disease condition were associated with the cell cycle and fibroblast proliferation procedures. TP53, EGF, FN1, NOTCH1, EZH2, COL1A1, SPP1, CDKN2A, WNT5A, PDGFRB, CCNB1, and H2AFX were demonstrated to be the most critical genes linked with the primary SGC. SPIB, FOXM1, and POLR2A significantly regulate all the hub genes. This study illustrated several hub genes and their master regulators that might be appropriate targets for the therapeutic aims of primary SGC.

The role of fibroblast growth factor 8 in cartilage development and disease

Fibroblast growth factor 8 (FGF‐8), also known as androgen‐induced growth factor (AIGF), is presumed to be a potent mitogenic cytokine that plays important roles in early embryonic development, brain formation and limb development. In the bone environment, FGF‐8 produced or received by chondrocyte precursor cells binds to fibroblast growth factor receptor (FGFR), causing different levels of activation of downstream signalling pathways, such as phospholipase C gamma (PLCγ)/Ca²⁺, RAS/mitogen‐activated protein kinase‐extracellular regulated protein kinases (RAS/MAPK‐MEK‐ERK), and Wnt‐β‐catenin‐Axin2 signalling, and ultimately controlling chondrocyte proliferation, differentiation, cell survival and migration. However, the molecular mechanism of FGF‐8 in normal or pathological cartilage remains unclear, and thus, FGF‐8 represents a novel exploratory target for studies of chondrocyte development and cartilage disease progression. In this review, studies assessing the relationship between FGF‐8 and chondrocytes that have been published in the past 5 years are systematically summarized to determine the probable mechanism and physiological effect of FGF‐8 on chondrocytes. Based on the existing research results, a therapeutic regimen targeting FGF‐8 is proposed to explore the possibility of treating chondrocyte‐related diseases.

[Research Progress of Fibroblast Growth Factor 8's Role in the Regulation of Bone Development and Homeostasis]

The proper development and the homeostasis maintenance of bones are important prerequisites for the normal functioning of the human body. Bone developmental deformities or homeostasis disorders, such as Kashin-Beck disease, craniosynostosis, cleft palate and osteoarthritis, severely affect the life of patients, causing significant stress to the family and the society. Fibroblast growth factor 8 (FGF8) plays multiple functions through the course of the life of organisms. Abnormal expression of FGF8 may cause disorders of bone homeostasis and developmental abnormalities of bones. More and more studies have found that FGF8 may play an important role in bone development and may become a potential therapeutic target. Herein, we reviewed the role of FGF8 in a variety of skeletal abnormalities, intending to provide new perspectives for the prevention and treatment of related diseases in the future.

Functional Roles of FGF Signaling in Early Development of Vertebrate Embryos

Fibroblast growth factors (FGFs) comprise a large family of growth factors, regulating diverse biological processes including cell proliferation, migration, and differentiation. Each FGF binds to a set of FGF receptors to initiate certain intracellular signaling molecules. Accumulated evidence suggests that in early development and adult state of vertebrates, FGFs also play exclusive and context dependent roles. Although FGFs have been the focus of research for therapeutic approaches in cancer, cardiovascular disease, and metabolic syndrome, in this review, we mainly focused on their role in germ layer specification and axis patterning during early vertebrate embryogenesis. We discussed the functional roles of FGFs and their interacting partners as part of the gene regulatory network for germ layer specification, dorsal-ventral (DV), and anterior-posterior (AP) patterning. Finally, we briefly reviewed the regulatory molecules and pharmacological agents discovered that may allow modulation of FGF signaling in research.

Fibroblast growth factor induced Ucp1 expression in preadipocytes requires PGE2 biosynthesis and glycolytic flux

High uncoupling protein 1 (Ucp1) expression is a characteristic of differentiated brown adipocytes and is linked to adipogenic differentiation. Paracrine fibroblast growth factor 8b (FGF8b) strongly induces Ucp1 transcription in white adipocytes independent of adipogenesis. Here, we report that FGF8b and other paracrine FGFs act on brown and white preadipocytes to upregulate Ucp1 expression via a FGFR1-MEK1/2-ERK1/2 axis, independent of adipogenesis. Transcriptomic analysis revealed an upregulation of prostaglandin biosynthesis and glycolysis upon Fgf8b treatment of preadipocytes. Oxylipin measurement by LC-MS/MS in FGF8b conditioned media identified prostaglandin E₂ as a putative mediator of FGF8b induced Ucp1 transcription. RNA interference and pharmacological inhibition of the prostaglandin E₂ biosynthetic pathway confirmed that PGE2 is causally involved in the control over Ucp1 transcription. Importantly, impairment of or failure to induce glycolytic flux blunted the induction of Ucp1, even in the presence of PGE₂ . Lastly, a screening of transcription factors identified Nrf1 and Hes1 as required regulators of FGF8b induced Ucp1 expression. Thus, we conclude that paracrine FGFs co-regulate prostaglandin and glucose metabolism to induce Ucp1 expression in a Nrf1/Hes1-dependent manner in preadipocytes, revealing a novel regulatory network in control of Ucp1 expression in a formerly unrecognized cell type.

A Fusion Transcription Factor-Driven Cancer Progresses to a Fusion-Independent Relapse via Constitutive Activation of a Downstream Transcriptional Target

Targeted monotherapies usually fail due to development of resistance by a subgroup of cells that evolve into recurrent tumors. Alveolar rhabdomyosarcoma is an aggressive myogenic soft-tissue cancer that is associated with a characteristic PAX3-FOXO1 gene fusion encoding a novel fusion transcription factor. In our myoblast model of PAX3-FOXO1-induced rhabdomyosarcoma, deinduction of PAX3-FOXO1 simulates a targeted therapy that antagonizes the fusion oncoprotein. This simulated therapy results initially in regression of the primary tumors, but PAX3-FOXO1-independent recurrent tumors eventually form after a delay. We report here that upregulation of FGF8, a direct transcriptional target of PAX3-FOXO1, is a mechanism responsible for PAX3-FOXO1-independent tumor recurrence. As a transcriptional target of PAX3-FOXO1, FGF8 promoted oncogenic activity in PAX3-FOXO1-expressing primary tumors that developed in the myoblast system. In the recurrent tumors forming after PAX3-FOXO1 deinduction, FGF8 expression was necessary and sufficient to induce PAX3-FOXO1-independent tumor growth through an autocrine mechanism. FGF8 was also expressed in human PAX3-FOXO1-expressing rhabdomyosarcoma cell lines and contributed to proliferation and transformation. In a human rhabdomyosarcoma cell line with reduced PAX3-FOXO1 expression, FGF8 upregulation rescued oncogenicity and simulated recurrence after PAX3-FOXO1-targeted therapy. We propose that deregulated expression of a PAX3-FOXO1 transcriptional target can generate resistance to therapy directed against this oncogenic transcription factor and postulate that this resistance mechanism may ultimately be countered by therapeutic approaches that antagonize the corresponding downstream pathways. SIGNIFICANCE: In a model of cancer initiated by a fusion transcription factor, constitutive activation of a downstream transcriptional target leads to fusion oncoprotein-independent recurrences, thereby highlighting a novel progression mechanism and therapeutic target.

The role of the fibroblast growth factor family in bone-related diseases

Fibroblast growth factor (FGF) family members are important regulators of cell growth, proliferation, differentiation, and regeneration. The abnormal expression of certain FGF family members can cause skeletal diseases, including achondroplasia, craniosynostosis syndrome, osteoarthritis, and Kashin-Beck disease. Accumulating evidence shows that FGFs play a crucial role in the growth and proliferation of bone and in the pathogenesis of certain bone-related diseases. Here, we review the involvement of FGFs in bone-related processes and diseases; FGF1 in the differentiation of human bone marrow mesenchymal stem cells and fracture repair; FGF2, FGF9, and FGF18 in osteoarthritis; FGF6 in bone and muscle injury; FGF8 in osteoarthritis and Kashin-Beck disease; and FGF21 and FGF23 on bone regulation. These findings indicate that FGFs are targets for novel therapeutic interventions for bone-related diseases.

Comparative study on seasonal hair follicle cycling by analysis of the transcriptomes from cashmere and milk goats

Guard hair and cashmere undercoat are developed from primary and secondary hair follicle, respectively. Little is known about the gene expression differences between primary and secondary hair follicle cycling. In this study, we obtained RNA-seq data from cashmere and milk goats grown at four different seasons. We studied the differentially expressed genes (DEGs) during the yearly hair follicle cycling, and between cashmere and milk goats. WNT, NOTCH, MAPK, BMP, TGFβ and Hedgehog signaling pathways were involved in hair follicle cycling in both cashmere and milk goat. However, Milk goat DEGs between different months were significantly more than cashmere goat DEGs, with the largest difference being identified in December. Some expression dynamics were confirmed by quantitative PCR and western blot, and immunohistochemistry. This study offers new information sources related to hair follicle cycling in milk and cashmere goats, which could be applicable to improve the wool production and quality.

The ubiquitin ligase HECTD1 promotes retinoic acid signaling required for development of the aortic arch

The development of the aortic arch is a complex process that involves remodeling of the bilaterally symmetrical pharyngeal arch arteries (PAAs) into the mature asymmetric aortic arch. Retinoic acid signaling is a key regulator of this process by directing patterning of the second heart field (SHF), formation of the caudal PAAs and subsequent remodeling of the PAAs to form the aortic arch. Here, we identify the HECTD1 ubiquitin ligase as a novel modulator of retinoic acid signaling during this process. Hectd1^opm/opm homozygous mutant embryos show a spectrum of aortic arch abnormalities that occur following loss of 4th PAAs and increased SHF marker expression. This sequence of defects is similar to phenotypes observed in mutant mouse models with reduced retinoic acid signaling. Importantly, HECTD1 binds to and influences ubiquitination of the retinoic acid receptor, alpha (RARA). Furthermore, reduced activation of a retinoic acid response element (RARE) reporter is detected in Hectd1 mutant cells and embryos. Interestingly, Hectd1^opm/+ heterozygous embryos exhibit reduced retinoic acid signaling, along with intermediate increased expression of SHF markers; however, heterozygotes show normal development of the aortic arch. Decreasing retinoic acid synthesis by reducing Raldh2 (also known as Aldh1a2) gene dosage in Hectd1^opm/+ heterozygous embryos reveals a genetic interaction. Double heterozygous embryos show hypoplasia of the 4th PAA and increased incidence of a benign aortic arch variant, in which the transverse arch between the brachiocephalic and left common carotid arteries is shortened. Together, our data establish that HECTD1 is a novel regulator of retinoic acid signaling required for proper aortic arch development.

Editor's choice: The HECTD1 ubiquitin ligase is a novel modulator of retinoic acid signaling during aortic arch development and provides a model for complex interactions underlying variations in aortic arch development.

The fibroblast growth factor 8 family in the female reproductive tract

Several growth factor families have been shown to be involved in the function of the female reproductive tract. One subfamily of the fibroblast growth factor (FGF) superfamily, namely the FGF8 subfamily (including FGF17 and FGF18), has become important as Fgf8 has been described as an oocyte-derived factor essential for glycolysis in mouse cumulus cells and aberrant expression ofFGF18has been described in ovarian and endometrial cancers. In this review, we describe the pattern of expression of these factors in normal ovaries and uteri in rodents, ruminants and humans, as well as the expression of their receptors and intracellular negative feedback regulators. Expression of these molecules in gynaecological cancers is also reviewed. The role of FGF8 and FGF18 in ovarian and uterine function is described, and potential differences between rodents and ruminants have been highlighted especially with respect to FGF18 signalling within the ovarian follicle. Finally, we identify major questions about the reproductive biology of FGFs that remain to be answered, including (1) the physiological concentrations within the ovary and uterus, (2) which cell types within the endometrial stroma and theca layer express FGFs and (3) which receptors are activated by FGF8 subfamily members in reproductive tissues.

Supt20 is required for development of the axial skeleton

Somitogenesis and subsequent axial skeletal development is regulated by the interaction of pathways that determine the periodicity of somite formation, rostrocaudal somite polarity and segment identity. Here we use a hypomorphic mutant mouse line to demonstrate that Supt20 (Suppressor of Ty20) is required for development of the axial skeleton. Supt20 hypomorphs display fusions of the ribs and vertebrae at lower thoracic levels along with anterior homeotic transformation of L1 to T14. These defects are preceded by reduction of the rostral somite and posterior shifts in Hox gene expression. While cycling of Notch target genes in the posterior presomitic mesoderm (PSM) appeared normal, expression of Lfng was reduced. In the anterior PSM, Mesp2 expression levels and cycling were unaffected; yet, expression of downstream targets such as Lfng, Ripply2, Mesp1 and Dll3 in the prospective rostral somite was reduced accompanied by expansion of caudal somite markers such as EphrinB2 and Hes7. Supt20 interacts with the Gcn5-containing SAGA histone acetylation complex. Gcn5 hypomorphic mutant embryos show similar defects in axial skeletal development preceded by posterior shift of Hoxc8 and Hoxc9 gene expression. We demonstrate that Gcn5 and Supt20 hypomorphs show similar defects in rostral-caudal somite patterning potentially suggesting shared mechanisms.

Fibroblast Growth Factor 8 Expression in GT1-7 GnRH-Secreting Neurons Is Androgen-Independent, but Can Be Upregulated by the Inhibition of DNA Methyltransferases

Fibroblast growth factor 8 (FGF8) is a potent morphogen that regulates the embryonic development of hypothalamic neuroendocrine cells. Indeed, using Fgf8 hypomorphic mice, we showed that reduced Fgf8 mRNA expression completely eliminated the presence of gonadotropin-releasing hormone (GnRH) neurons. These findings suggest that FGF8 signaling is required during the embryonic development of mouse GnRH neurons. Additionally, in situ hybridization studies showed that the embryonic primordial birth place of GnRH neurons, the olfactory placode, is highly enriched for Fgf8 mRNA expression. Taken together these data underscore the importance of FGF8 signaling for GnRH emergence. However, an important question remains unanswered: How is Fgf8 gene expression regulated in the developing embryonic mouse brain? One major candidate is the androgen receptor (AR), which has been shown to upregulate Fgf8 mRNA in 60-70% of newly diagnosed prostate cancers. Therefore, we hypothesized that ARs may be involved in the regulation of Fgf8 transcription in the developing mouse brain. To test this hypothesis, we used chromatin-immunoprecipitation (ChIP) assays to elucidate whether ARs interact with the 5'UTR region upstream of the translational start site of the Fgf8 gene in immortalized mouse GnRH neurons (GT1-7) and nasal explants. Our data showed that while AR interacts with the Fgf8 promoter region, this interaction was androgen-independent, and that androgen treatment did not affect Fgf8 mRNA levels, indicating that androgen signaling does not induce Fgf8 transcription. In contrast, inhibition of DNA methyltransferases (DNMT) significantly upregulated Fgf8 mRNA levels indicating that Fgf8 transcriptional activity may be dependent on DNA methylation status.

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.

The tumor suppressor PTEN and the PDK1 kinase regulate formation of the columnar neural epithelium

Epithelial morphogenesis and stability are essential for normal development and organ homeostasis. The mouse neural plate is a cuboidal epithelium that remodels into a columnar pseudostratified epithelium over the course of 24 hr. Here we show that the transition to a columnar epithelium fails in mutant embryos that lack the tumor suppressor PTEN, although proliferation, patterning and apical-basal polarity markers are normal in the mutants. The Pten phenotype is mimicked by constitutive activation of PI3 kinase and is rescued by the removal of PDK1 (PDPK1), but does not depend on the downstream kinases AKT and mTORC1. High resolution imaging shows that PTEN is required for stabilization of planar cell packing in the neural plate and for the formation of stable apical-basal microtubule arrays. The data suggest that appropriate levels of membrane-associated PDPK1 are required for stabilization of apical junctions, which promotes cell elongation, during epithelial morphogenesis.

Fibroblast growth factors, old kids on the new block

The fibroblast growth factors (FGFs) are a family of cell intrinsic regulatory peptides that control a broad spectrum of cellular activities. The family includes canonic FGFs that elicit their activities by activating the FGF receptor (FGFR) tyrosine kinase and non-canonic members that elicit their activities intracellularly and via FGFR-independent mechanisms. The FGF signaling axis is highly complex due to the existence of multiple isoforms of both ligands and receptors, as well as cofactors that include the chemically heterogeneous heparan sulfate (HS) cofactors, and in the case of endocrine FGFs, the Klotho coreceptors. Resident FGF signaling controls embryonic development, maintains tissue homeostasis, promotes wound healing and tissue regeneration, and regulates functions of multiple organs. However, ectopic or aberrant FGF signaling is a culprit for various diseases, including congenital birth defects, metabolic disorder, and cancer. The molecular mechanisms by which the specificity of FGF signaling is achieved remain incompletely understood. Since its application as a druggable target has been gradually recognized by pharmaceutical companies and translational researchers, understanding the determinants of FGF signaling specificity has become even more important in order to get into the position to selectively suppress a particular pathway without affecting others to minimize side effects.

The Regulation and Function of Fibroblast Growth Factor 8 and Its Function during Gonadotropin-Releasing Hormone Neuron Development

Over the last few years, numerous studies solidified the hypothesis that fibroblast growth factor (FGF) signaling regulates neuroendocrine progenitor cell proliferation, fate specification, and cell survival and, therefore, is critical for the regulation and maintenance of homeostasis of the body. One important example that underscores the involvement of FGF signaling during neuroendocrine cell development is gonadotropin-releasing hormone (GnRH) neuron ontogenesis. Indeed, transgenic mice with reduced olfactory placode (OP) Fgf8 expression do not have GnRH neurons. This observation indicates the requirement of FGF8 signaling for the emergence of the GnRH neuronal system in the embryonic OP, the putative birth place of GnRH neurons. Mammalian reproductive success depends on the presence of GnRH neurons to stimulate gonadotropin secretion from the anterior pituitary, which activates gonadal steroidogenesis and gametogenesis. Together, these observations are critical for understanding the function of GnRH neurons and their control of the hypothalamus-pituitary-gonadal (HPG) axis to maintain fertility. Taken together, these studies illustrate that GnRH neuron emergence and hence HPG function is vulnerable to genomic and molecular signals that abnormally modify Fgf8 expression in the developing mouse OP. In this short review, we focus on research that is aimed at unraveling how androgen, all-trans retinoic acid, and how epigenetic factors modify control mouse OP Fgf8 transcription in the context of GnRH neuronal development and mammalian reproductive success.

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.

Regulatory effects of fibroblast growth factor-8 and tumor necrosis factor-α on osteoblast marker expression induced by bone morphogenetic protein-2

BMP induces osteoblast differentiation, whereas a key proinflammatory cytokine, TNF-α, causes inflammatory bone damage shown in rheumatoid arthritis. FGF molecules are known to be involved in bone homeostasis. However, the effects of FGF-8 on osteoblast differentiation and the interaction between FGF-8, BMPs and TNF-α have yet to be clarified. Here we investigated the effects of FGF-8 in relation to TNF-α actions on BMP-2-induced osteoblast marker expression using myoblast cell line C2C12, osteoblast precursor cell line MC3T3-E1 and rat calvarial osteoblasts. It was revealed that FGF-8 inhibited BMP-2-induced expression of osteoblast differentiation markers, including Runx2, osteocalcin, alkaline phosphatase, type-1 collagen and osterix, in a concentration-dependent manner. The inhibitory effects of FGF-8 on BMP-induced osteoblast differentiation and Smad1/5/8 activation were enhanced in the presence of TNF-α action. FGF-8 also inhibited BMP-2-induced expression of Wnt5a, which activates a non-canonical Wnt signaling pathway. FGF-8 had no significant influence on the expression levels of TNF receptors, while FGF-8 suppressed the expression of inhibitory Smad6 and Smad7, suggesting a possible feedback activity through FGF to BMP receptor (BMPR) signaling. Of note, inhibition of ERK activity and FGF receptor (FGFR)-dependent protein kinase, but not JNK or NFκB pathway, suppressed the FGF-8 actions on BMP-induced osteoblast differentiation. FGF-8 was revealed to suppress BMP-induced osteoblast differentiation through the ERK pathway and the effects were enhanced by TNF-α. Given the finding that FGF-8 expression was increased in synovial tissues of rheumatoid arthritis, the functional interaction between FGFR and BMPR signaling may be involved in the development process of inflammatory bone damage.

Enhanced Expression of Fibroblast Growth Factor Receptor 3 IIIc Promotes Human Esophageal Carcinoma Cell Proliferation

Deregulated expression of fibroblast growth factor receptors (FGFRs) and their ligands plays critical roles in tumorigenesis. The gene expression of an alternatively spliced isoforms of FGFR3, FGFR3IIIc, was analyzed by RT-PCR in samples from patients with esophageal carcinoma (EC), including esophageal squamous cell carcinoma (ESCC) and adenocarcinoma (EAC). The incidence of FGFR3IIIc was higher in EC [12/16 (75%); p=0.073] than in non-cancerous mucosa (NCM) [6/16 (38%)]. Indeed, an immunohistochemical analysis of early-stage ESCC showed that carcinoma cells expressing FGFR3IIIc stained positively with SCC-112, a tumor marker, and Ki67, a cell proliferation marker, suggesting that the expression of FGFR3IIIc promotes cell proliferation. We used EC-GI-10 cells endogenously expressing FGFR3IIIc as a model of ESCC to provide mechanistic insight into the role of FGFR3IIIc in ESCC. The knockdown of endogenous FGFR3 using siRNA treatment significantly abrogated cell proliferation and the overexpression of FGFR3IIIc in cells with enhanced cell proliferation. EC-GI-10 cells and ESCC from patients with EC showed endogenous expression of FGF2, a specific ligand for FGFR3IIIc, suggesting that the upregulated expression of FGFR3IIIc may create autocrine FGF signaling in ESCC. Taken together, FGFR3IIIc may have the potential to be an early-stage tumor marker and a molecular target for ESCC therapy.

Expression of functional recombinant human fibroblast growth factor 8b and its protective effects on MPP⁺-lesioned PC12 cells

Human fibroblast growth factor 8b (FGF8b) was expressed based on a baculovirus expression vector system (BEVS) and identified as having a protective effect on Parkinson's disease. Immunoblotting demonstrated that rhFGF8b proteins were recognized by a human anti-FGF8b antibody. The multiplicity of infection and timing of harvest had a significant effect on protein yield and protein quality. Our results indicated that the rhFGF8b was first detectable at 36 h postinfection and reached a maximum at 60 h. A multiplicity of infection (MOI) of 8 pfu/mL was suitable for harvest. The target protein was purified by heparin-affinity chromatography. In vitro methylthiazol tetrazolium (MTT) assays demonstrated that the purified rhFGF8b could significantly stimulate proliferation of NIH3T3 cells. Furthermore, to elucidate the effect of rhFGF8b on Parkinson's disease, we used FGF8b pretreatment on a cell model of Parkinson's disease. The results indicated that rhFGF8b prevented necrosis and apoptosis of 1-METHYL-4-phenyl pyridine (MPP(+)) treated PC12 cells. Moreover, the effect of FGF8b on messenger RNA (mRNA) levels of apoptosis and ERS genes was investigated to clarify the molecular mechanisms of FGF8b. The results suggest that FGF8b exerts neuroprotective effects by alleviating endoplasmic reticulum (ER) stress during PD. These results suggest that FGF8b may be a promising candidate therapeutic drug for neurodegenerative diseases related to ER stress.

Role of peptide growth factors in the rhythm of change hair

The article presents current data on the role growth factors play in hair physiology. Based on a review of literature, the authors described the role growth factors play for initiating, suppressing the growth and differentiating hair follicles. According to them, each morphologic development stage of hair follicles is characterized by its own factor expression pattern. Referring to experimental and clinical studies, the authors describe the role some growth factors play for mechanisms promoting the development of androgynous and focal alopecia.

Development of the external genitalia and their sexual dimorphic regulation in mice

The study of the external genitalia is divided into 2 developmental stages: the formation and growth of a bipotential genital tubercle (GT) and the sexual differentiation of the male and female GT. The sexually dimorphic processes, which occur during the second part of GT differentiation, are suggested to be governed by androgen signaling and more recently crosstalk with other signaling factors. The process of elucidating the regulatory mechanisms of hormone signaling towards other signaling networks in the GT is still in its early stages. Nevertheless, it is becoming a productive area of research. This review summarizes various studies on the development of the murine GT and the defining characteristics of a masculinized GT and presents the different signaling pathways possibly involved during masculinization.

Fibroblast growth factor control of cartilage homeostasis

Osteoarthritis (OA) and degenerative disc disease (DDD) are similar diseases involving the breakdown of cartilage tissue, and a better understanding of the underlying biochemical processes involved in cartilage degeneration may allow for the development of novel biologic therapies aimed at slowing the disease process. Three members of the fibroblast growth factor (FGF) family, FGF-2, FGF-18, and FGF-8, have been implicated as contributing factors in cartilage homeostasis. The role of FGF-2 is controversial in both articular and intervertebral disc (IVD) cartilage as it has been associated with species- and age-dependent anabolic or catabolic events. Recent evidence suggests that FGF-2 selectively activates FGF receptor 1 (FGFR1) to exert catabolic effects in human articular chondrocytes and IVD tissue via upregulation of matrix-degrading enzyme production, inhibition of extracellular matrix (ECM) accumulation and proteoglycan synthesis, and clustering of cells characteristic of arthritic states. FGF-18, on the other hand, most likely exerts anabolic effects in human articular chondrocytes by activating the FGFR3 pathway, inducing ECM formation and chondrogenic cell differentiation, and inhibiting cell proliferation. These changes result in dispersed chondrocytes or disc cells surrounded by abundant matrix. The role of FGF-8 has recently been identified as a catabolic mediator in rat and rabbit articular cartilage, but its precise biological impact on human adult articular cartilage or IVD tissue remains unknown. The available evidence reveals the promise of FGF-2/FGFR1 antagonists, FGF-18/FGFR3 agonists, and FGF-8 antagonists (i.e., anti-FGF-8 antibody) as potential therapies to prevent cartilage degeneration and/or promote cartilage regeneration and repair in the future.

Prostatic stromal sarcoma with neuroectodermal differentiation

Abstract

Prostatic stromal sarcoma is a fairly rare tumor that constitutes approximately 0.1–0.2% of all prostatic cancers. Detailed characteristics of the tumor are still unclear due to its rarity.

We describe a case of prostatic stromal sarcoma in a 63 year-old man who suffered from urinary obstructive symptoms. Palliative transuterine resection was performed and the preliminary histopathological diagnosis was neuroendocrine carcinoma. After chemotherapy, total pelvic exenteration was performed. Histopathologically, the tumor was composed of monotonously proliferating small to medium-sized round cells, which existed in compact islands with loose or dense fibrovascular networks. Immunohistochemically, the tumor cells were widely positive for vimentin, CD56, CD99 and focally positive for synaptophysin, CD10, progesterone receptor, desmin and CD34, but negative for EMA, cytokeratin, estrogen receptor, S-100 and myoglobin. Most of the previously reported tumors exhibited positive stainability for CD10 and progesterone receptor. In addition to these markers, expressions of CD56, CD99 and synaptophysin were characteristically detected in our case. To the best of our knowledge, we present the first case of prostatic stromal sarcoma with characteristic immunohistochemical staining properties. Although the biological characteristics of this rare tumor have not yet been elucidated, these findings suggest prostatic stromal sarcoma can potentially show neuroectodermal differentiation.

Virtual slide

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/7291874028051262

Changes in expression and secretion patterns of fibroblast growth factor 8 and Sonic Hedgehog signaling pathway molecules during murine neural stem/progenitor cell differentiation in vitro

In the present study, we investigated the dynamic expression of fibroblast growth factor 8 and Sonic Hedgehog signaling pathway related factors in the process of in vitro hippocampal neural stem/progenitor cell differentiation from embryonic Sprague-Dawley rats or embryonic Kunming species mice, using fluorescent quantitative reverse transcription-PCR and western blot analyses. Results demonstrated that the dynamic expression of fibroblast growth factor 8 was similar to fibroblast growth factor receptor 1 expression but not to other fibroblast growth factor receptors. Enzyme-linked immunosorbent assay demonstrated that fibroblast growth factor 8 and Sonic Hedgehog signaling pathway protein factors were secreted by neural cells into the intercellular niche. Our experimental findings indicate that fibroblast growth factor 8 and Sonic Hedgehog expression may be related to the differentiation of neural stem/progenitor cells.

RhoC and guanine nucleotide exchange factor Net1 in androgen-unresponsive mouse mammary carcinoma SC-4 cells and human prostate cancer after short-term endocrine therapy

BACKGROUND

Endocrine resistance is a critical issue in managing patients with prostate cancer. This study is undertaken to search for a potential molecular target connected with this process using a model system of androgen-dependent and androgen-unresponsive SC-3 and SC-4 cells.

METHODS

Expression profiles, actin stress fiber organization, and the levels of activated Rho GTPases were compared between SC-4 and SC-3 cells using an oligonucleotide microarray, phalloidin staining, and a Rho activation assay. The cell viability was analyzed with a Rho inhibitor or by stable transfection with either a dominant-negative (DN) form of RhoC or a mutant form of NET1 (mutNET1). The expressions of RhoC, NET1, and epithelial-mesenchymal transition (EMT) markers were immunohistochemically analyzed in human prostate cancer specimens after short-term endocrine therapy and in an untreated condition.

RESULTS

SC-4 cells exhibited mesenchymal phenotypes with activation of Rho signals. Treatment with a Rho inhibitor suppressed the cell viability in SC-4 cells, but not in SC-3 cells. The cell viability of SC-4 cells stably expressing DN-RhoC and mutNET1 was also attenuated. In the immunohistochemical analysis, NET1 and the EMT marker of N-cadherin were expressed at higher levels in prostate cancers after short-term endocrine therapy than in untreated tumors, and RhoC expression was maintained after short-term endocrine therapy.

CONCLUSIONS

Rho signaling is involved in the cell survival of SC-4 cells. The higher expressions of RhoC and NET1 in human prostate cancers after short-term endocrine therapy suggest that RhoC and NET1 may become therapeutic targets during endocrine therapy.

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.

Numerous isoforms of Fgf8 reflect its multiple roles in the developing brain

Soluble growth factors play an important role in the coordination and integration of cell proliferation, differentiation, fate determination, and morphogenesis during development of multicellular organisms. Fibroblast growth factors (FGFs) are a large family of polypeptide growth factors that are present in organisms ranging from nematodes to humans. RNA alternative splicing of FGFs and their receptors further enhances the complexity of this ligand-receptor system. The mouse Fgf8 gene produces eight splice variants, which encode isoform proteins with different N-termini and distinct receptor-binding affinity and biological activity. In this article, we review the roles of Fgf8 in vertebrate development and summarize the recent findings on the in vivo function of different Fgf8 splice variants. We propose that multiple Fgf8 isoform proteins act in concert to regulate the overall function of Fgf8 and account for the diverse and essential role of Fgf8 during vertebrate development.

Androgen action during prostate carcinogenesis

Androgens are critical for normal prostate development and function, as well as prostate cancer initiation and progression. Androgens function mainly by regulating target gene expression through the androgen receptor (AR). Many studies have shown that androgen-AR signaling exerts actions on key events during prostate carcinogenesis. In this review, androgen action in distinct aspects of prostate carcinogenesis, including (i) cell proliferation, (ii) cell apoptosis, and (iii) prostate cancer metastasis will be discussed.

Extending the family table: Insights from beyond vertebrates into the regulation of embryonic development by FGFs

Since the discovery of fibroblast growth factors (FGFs) much focus has been placed on elucidating the roles for each vertebrate FGF ligand, receptor, and regulating molecules in the context of vertebrate development, human disorders and cancer. Studies in human, mouse, frog, chick, and zebrafish have made great contributions to our understanding of the role of FGFs in specific processes. However, in recent years, as more genomes are sequenced, information is becoming available from many non-vertebrate models and a more complete picture of the FGF superfamily as a whole is emerging. In some cases, less redundancy in these FGF signaling systems may allow for more mechanistic insights. Studies in sea anemones have highlighted how ancient FGF signaling is and helped provide insight into the evolution of the FGF gene family. Work in nematodes has shown that different splice forms can be used for functional specificity in invertebrate FGF signaling. Comparing FGFs between urochordates and vertebrates as well as between different insect species reveals important clues into the process of gene loss, duplication and subfunctionalization of FGFs throughout evolution. Finally, comparing all members of the FGF ligand superfamily reveals variability in many properties, which may point to a feature of FGFs as being highly adaptable with regards to protein structure and signaling mechanism. Further studies on FGF signaling outside of vertebrates is likely to continue to complement work in vertebrates by contributing additional insights to the FGF field and providing unexpected information that could be used for medical applications.

Fast growth associated with aberrant vasculature and hypoxia in fibroblast growth factor 8b (FGF8b) over-expressing PC-3 prostate tumour xenografts

BACKGROUND

Prostate tumours are commonly poorly oxygenated which is associated with tumour progression and development of resistance to chemotherapeutic drugs and radiotherapy. Fibroblast growth factor 8b (FGF8b) is a mitogenic and angiogenic factor, which is expressed at an increased level in human prostate tumours and is associated with a poor prognosis. We studied the effect of FGF8b on tumour oxygenation and growth parameters in xenografts in comparison with vascular endothelial growth factor (VEGF)-expressing xenografts, representing another fast growing and angiogenic tumour model.

METHODS

Subcutaneous tumours of PC-3 cells transfected with FGF8b, VEGF or empty (mock) vectors were produced and studied for vascularity, cell proliferation, glucose metabolism and oxygenation. Tumours were evaluated by immunohistochemistry (IHC), flow cytometry, use of radiolabelled markers of energy metabolism ([18F]FDG) and hypoxia ([18F]EF5), and intratumoral polarographic measurements of pO2.

RESULTS

Both FGF8b and VEGF tumours grew rapidly in nude mice and showed highly vascularised morphology. Perfusion studies, pO2 measurements, [18F]EF5 and [18F]FDG uptake as well as IHC staining for glucose transport protein (GLUT1) and hypoxia inducible factor (HIF) 1 showed that VEGF xenografts were well-perfused and oxygenised, as expected, whereas FGF8b tumours were as hypoxic as mock tumours. These results suggest that FGF8b-induced tumour capillaries are defective. Nevertheless, the growth rate of hypoxic FGF8b tumours was highly increased, as that of well-oxygenised VEGF tumours, when compared with hypoxic mock tumour controls.

CONCLUSION

FGF8b is able to induce fast growth in strongly hypoxic tumour microenvironment whereas VEGF-stimulated growth advantage is associated with improved perfusion and oxygenation of prostate tumour xenografts.

Research resource: Comprehensive expression atlas of the fibroblast growth factor system in adult mouse

Although members of the fibroblast growth factor (FGF) family and their receptors have well-established roles in embryogenesis, their contributions to adult physiology remain relatively unexplored. Here, we use real-time quantitative PCR to determine the mRNA expression patterns of all 22 FGFs, the seven principal FGF receptors (FGFRs), and the three members of the Klotho family of coreceptors in 39 different mouse tissues. Unsupervised hierarchical cluster analysis of the mRNA expression data reveals that most FGFs and FGFRs fall into two groups the expression of which is enriched in either the central nervous system or reproductive and gastrointestinal tissues. Interestingly, the FGFs that can act as endocrine hormones, including FGF15/19, FGF21, and FGF23, cluster in a third group that does not include any FGFRs, underscoring their roles in signaling between tissues. We further show that the most recently identified Klotho family member, Lactase-like, is highly and selectively expressed in brown adipose tissue and eye and can function as an additional coreceptor for FGF19. This FGF atlas provides an important resource for guiding future studies to elucidate the physiological functions of FGFs in adult animals.

Functional relationship between fibroblast growth factor-8 and bone morphogenetic proteins in regulating steroidogenesis by rat granulosa cells

Bone morphogenetic proteins (BMPs) have been recognized as crucial molecules in regulating ovarian physiology, with different BMPs having differential actions in FSH-induced estradiol production. To identify the roles of oocyte factors that modulate steroidogenesis controlled by BMPs, we here investigated the effects of FGF-8 in rat granulosa/oocyte co-cultures. FGF-8 potently suppressed FSH-induced estradiol production, but did not affect cAMP-induced estradiol produced by rat granulosa cells. FGF-8 had no effects on progesterone and cAMP production induced by FSH and forskolin. The inhibitory effects of FGF-8 on FSH-induced estradiol production were not altered by BMP-2, -4, -6 or -7. In the presence of FGF-8, BMPs suppressed FSH-induced progesterone by reducing cAMP, suggesting that FGF-8 and BMP independently regulate FSH receptor signaling. Notably, FGF-8-induced ERK and SAPK/JNK phosphorylation in granulosa cells, in which ERK activation was further enhanced by FSH and oocytes. Inhibition of ERK and SAPK/JNK reduced FSH-induced progesterone and cAMP levels, suggesting that the activation of these pathways enhances FSH-induced cAMP signaling. In addition, ERK inhibition upregulated FSH-induced estradiol synthesis, indicating that ERK pathway is also involved in suppressing aromatase activity in granulosa cells. Interestingly, FGF-8 enhanced BMP-induced Smad1/5/8 and Id-1-promoter activities with decreased expression of Smad6/7. Since the SAPK/JNK inhibitor inhibited FGF-8 effects in upregulating Id-1 transcription, SAPK/JNK appears to be involved in the mechanism by which FGF-8 enhances BMP-Smad signaling. Furthermore, in the presence of oocytes, the inhibition of endogenous FGF receptor signaling suppressed FSH- and forskolin-induced progesterone and cAMP, showing that endogenous FGF system is involved in activation of FSH-induced cAMP-PKA signaling via ERK and SAPK/JNK. Thus, the oocyte factor, FGF-8, not only suppresses FSH-induced estradiol production by activating ERK, but also enhances BMP-Smad signaling in granulosa cells. This interaction between FGF-8 and BMPs may play a key role in regulating steroidogenesis through oocyte-granulosa cell communication.

Fibroblast growth factor 8 induced downregulation of thrombospondin 1 is mediated by the MEK/ERK and PI3K pathways in breast cancer cells

Expression of fibroblast growth factor 8 (FGF-8) is increased in several forms of hormonal cancer. It was previously shown to regulate expression of thrombospondin 1 (TSP-1), an inhibitor of angiogenesis, in S115 breast cancer cells. Here, we studied the FGF-8-activated signalling pathways mediating TSP-1 repression in S115 cells and in non-tumorigenic MCF10A cells. Inhibition of FGF receptors or of MEK1/2 and PI3K with specific inhibitors (PD173074, U0126 or LY294002, respectively) restored TSP-1 mRNA expression in the presence of FGF-8 in S115 cells. Furthermore, U0126 and LY294002 increased TSP-1 mRNA expression in S115 cells over-expressing FGF-8. In MCF10A cells, FGF-8 treatment also decreased TSP-1 expression and the effect was dependent on active MEK1/2. In conclusion, FGF-8 suppresses TSP-1 expression through two independent pathways, MEK1/2 and PI3K. Repression of TSP-1 may be an important mechanism involved in induction of an angiogenic phenotype and growth of FGF-8-expressing breast cancer.

FGF-8b induces growth and rich vascularization in an orthotopic PC-3 model of prostate cancer

Fibroblast growth factor 8 (FGF-8) is expressed at an increased level in a high proportion of prostate cancers and it is associated with a poor prognosis of the disease. Our aim was to study the effects of FGF-8b on proliferation of PC-3 prostate cancer cells and growth of PC-3 tumors, and to identify FGF-8b-associated molecular targets. Expression of ectopic FGF-8b in PC-3 cells caused a 1.5-fold increase in cell proliferation in vitro and a four- to fivefold increase in the size of subcutaneous and orthotopic prostate tumors in nude mice. Tumors expressing FGF-8b showed a characteristic morphology with a very rich network of capillaries. This was associated with increased spread of the cancer cells to the lungs as measured by RT-qPCR of FGF-8b mRNA. Microarray analyses revealed significantly altered, up- and downregulated, genes in PC-3 cell cultures (169 genes) and in orthotopic PC-3 tumors (61 genes). IPA network analysis of the upregulated genes showed the strongest association with development, cell proliferation (CRIP1, SHC1), angiogenesis (CCL2, DDAH2), bone metastasis (SPP1), cell-to-cell signaling and energy production, and the downregulated genes associated with differentiation (DKK-1, VDR) and cell death (CYCS). The changes in gene expression were confirmed by RT-qPCR. In conclusion, our results demonstrate that FGF-8b increases the growth and angiogenesis of orthotopic prostate tumors. The associated gene expression signature suggests potential mediators for FGF-8b actions on prostate cancer progression and metastasis.