Evidence for distinct alterations in the FGF axis in prostate cancer progression to an aggressive clinical phenotype

Golgi Complex: A Signaling Hub in Cancer

The Golgi Complex is the central hub in the endomembrane system and serves not only as a biosynthetic and processing center but also as a trafficking and sorting station for glycoproteins and lipids. In addition, it is an active signaling hub involved in the regulation of multiple cellular processes, including cell polarity, motility, growth, autophagy, apoptosis, inflammation, DNA repair and stress responses. As such, the dysregulation of the Golgi Complex-centered signaling cascades contributes to the onset of several pathological conditions, including cancer. This review summarizes the current knowledge on the signaling pathways regulated by the Golgi Complex and implicated in promoting cancer hallmarks and tumor progression.

The microdissected gene expression landscape of nasopharyngeal cancer reveals vulnerabilities in FGF and noncanonical NF-κB signaling

Nasopharyngeal cancer (NPC) is an Epstein-Barr virus (EBV)-positive epithelial malignancy with an extensive inflammatory infiltrate. Traditional RNA-sequencing techniques uncovered only microenvironment signatures, while the gene expression of the tumor epithelial compartment has remained a mystery. Here, we use Smart-3SEQ to prepare transcriptome-wide gene expression profiles from microdissected NPC tumors, dysplasia, and normal controls. We describe changes in biological pathways across the normal to tumor spectrum and show that fibroblast growth factor (FGF) ligands are overexpressed in NPC tumors, while negative regulators of FGF signaling, including SPRY1, SPRY2, and LGALS3, are down-regulated early in carcinogenesis. Within the NF-κB signaling pathway, the critical noncanonical transcription factors, RELB and NFKB2, are enriched in the majority of NPC tumors. We confirm the responsiveness of EBV-positive NPC cell lines to targeted inhibition of these pathways, reflecting the heterogeneity in NPC patient tumors. Our data comprehensively describe the gene expression landscape of NPC and unravel the mysteries of receptor tyrosine kinase and NF-κB pathways in NPC.

Intrinsically Fluorescent Oligomeric Cytotoxic Conjugates Toxic for FGFR1-Overproducing Cancers

Fibroblast growth factor receptor 1 (FGFR1) is an integral membrane protein that transmits prolife signals through the plasma membrane. Overexpression of FGFR1 has been reported in various tumor types, and therefore, this receptor constitutes an attractive molecular target for selective anticancer therapies. Here, we present a novel system for generation of intrinsically fluorescent, self-assembling, oligomeric cytotoxic conjugates with high affinity and efficient internalization targeting FGFR1. In our approach, we employed FGF1 as an FGFR1 recognizing molecule and genetically fused it to green fluorescent protein polygons (GFPp), a fluorescent oligomerization scaffold, resulting in a set of GFPp_FGF1 oligomers with largely improved receptor binding. To validate the applicability of using GFPp_FGF1 oligomers as cancer probes and drug carriers in targeted therapy of cancers with aberrant FGFR1, we selected a trimeric variant from generated GFPp_FGF1 oligomers and further engineered it by introducing FGF1-stabilizing mutations and by incorporating the cytotoxic drug monomethyl auristatin E (MMAE) in a site-specific manner. The resulting intrinsically fluorescent, trimeric cytotoxic conjugate 3xGFPp_FGF1E_LPET_MMAE exhibits nanomolar affinity for the receptor and very high stability. Notably, the intrinsic fluorescence of 3xGFPp_FGF1E_LPET_MMAE allows for tracking the cellular transport of the conjugate, demonstrating that 3xGFPp_FGF1E_LPET_MMAE is efficiently and selectively internalized into cells expressing FGFR1. Importantly, we show that 3xGFPp_FGF1E_LPET_MMAE displays very high cytotoxicity against a panel of different cancer cells overproducing FGFR1 while remaining neutral toward cells devoid of FGFR1 expression. Our data implicate that the engineered fluorescent conjugates can be used for imaging and targeted therapy of FGFR1-overproducing cancers.

Regulation of stability and inhibitory activity of the tumor suppressor SEF through casein-kinase II-mediated phosphorylation

Inflammation and cancer are intimately linked. A key mediator of inflammation is the transcription-factor NF-κB/RelA:p50. SEF (also known as IL-17RD) is a feedback antagonist of NF-κB/RelA:p50 that is emerging as an important link between inflammation and cancer. SEF acts as a buffer to prevent excessive NF-κB activity by sequestering NF-κB/RelA:p50 in the cytoplasm of unstimulated cells, and consequently attenuating the NF-κB response upon pro-inflammatory cytokine stimulation. SEF contributes to cancer progression also via modulating other signaling pathways, including those triggered by growth-factors. Despite its important role in human physiology and pathology, mechanisms that regulate SEF biochemical properties and inhibitory activity are unknown. Here we show that human SEF is an intrinsically labile protein that is stabilized via CK2-mediated phosphorylation, and identified the residues whom phosphorylation by CK2 stabilizes hSEF. Unlike endogenous SEF, ectopic SEF was rapidly degraded when overexpressed but was stabilized in the presence of excess CK2, suggesting a mechanism for limiting SEF levels depending upon CK2 processivity. Additionally, phosphorylation by CK2 potentiated hSef interaction with NF-κB in cell-free binding assays. Most importantly, we identified a CK2 phosphorylation site that was indispensable for SEF inhibition of pro-inflammatory cytokine signaling but was not required for SEF inhibition of growth-factor signaling. To our knowledge, this is the first demonstration of post-translational modifications that regulate SEF at multiple levels to optimize its inhibitory activity in a specific signaling context. These findings may facilitate the design of SEF variants for treating cytokine-dependent pathologies, including cancer and chronic inflammation.

Fibroblast Growth Factor Receptors (FGFRs) and Noncanonical Partners in Cancer Signaling

Increasing evidence indicates that success of targeted therapies in the treatment of cancer is context-dependent and is influenced by a complex crosstalk between signaling pathways and between cell types in the tumor. The Fibroblast Growth Factor (FGF)/FGF receptor (FGFR) signaling axis highlights the importance of such context-dependent signaling in cancer. Aberrant FGFR signaling has been characterized in almost all cancer types, most commonly non-small cell lung cancer (NSCLC), breast cancer, glioblastoma, prostate cancer and gastrointestinal cancer. This occurs primarily through amplification and over-expression of FGFR1 and FGFR2 resulting in ligand-independent activation. Mutations and translocations of FGFR1-4 are also identified in cancer. Canonical FGF-FGFR signaling is tightly regulated by ligand-receptor combinations as well as direct interactions with the FGFR coreceptors heparan sulfate proteoglycans (HSPGs) and Klotho. Noncanonical FGFR signaling partners have been implicated in differential regulation of FGFR signaling. FGFR directly interacts with cell adhesion molecules (CAMs) and extracellular matrix (ECM) proteins, contributing to invasive and migratory properties of cancer cells, whereas interactions with other receptor tyrosine kinases (RTKs) regulate angiogenic, resistance to therapy, and metastatic potential of cancer cells. The diversity in FGFR signaling partners supports a role for FGFR signaling in cancer, independent of genetic aberration.

The cytotoxic conjugate of highly internalizing tetravalent antibody for targeting FGFR1-overproducing cancer cells

BACKGROUND

Antibody drug conjugates (ADCs) represent one of the most promising approaches in the current immuno-oncology research. The precise delivery of cytotoxic drugs to the cancer cells using ADCs specific for tumor-associated antigens enables sparing the healthy cells and thereby reduces unwanted side effects. Overexpression of fibroblast growth factor receptor 1 (FGFR1) has been demonstrated in numerous tumors and thereby constitutes a convenient molecular target for selective cancer treatment. We have recently engineered tetravalent anti-FGFR1 antibody, T-Fc, and have demonstrated that it displays extremely efficient internalization into FGFR1 producing cells, a feature highly desirable in the ADC approach. We have revealed that T-Fc mediates clustering of FGFR1, largely enhancing the uptake of FGFR1-T-Fc complexes by induction of clathrin-independent endocytic routes. The aim of this study was to obtain highly internalizing cytotoxic conjugate of the T-Fc for specific delivery of drugs into FGFR1-positive cancer cells.

METHODS

Conjugation of the T-Fc to a cytotoxic payload, vcMMAE, was carried out via maleimide chemistry, yielding the T-Fc-vcMMAE. The specific binding of the T-Fc-vcMMAE conjugate to FGFR1 was confirmed in vitro with BLI technique. Confocal microscopy and flow cytometry were applied to determine FGFR1-dependence of the T-Fc-vcMMAE internalization. Western blot analyses of FGFR1-dependent signaling were conducted to assess the impact of the T-Fc-vcMMAE on FGFR1 activation and initiation of downstream signaling cascades. Finally, using FGFR1-negative and FGFR1-possitive cell lines, the cytotoxic potential of the T-Fc-vcMMAE was evaluated.

RESULTS

We have performed the efficient conjugation of the tetravalent engineered antibody with a cytotoxic drug and generated FGFR1-specific ADC molecule, T-Fc-vcMMAE. We have demonstrated that T-Fc-vcMMAE conjugate exhibits high selectivity and affinity for FGFR1, similarly to T-Fc. Furthermore, we have shown that T-Fc constitutes an effective drug delivery vehicle as T-Fc-vcMMAE was efficiently and selectively internalized by FGFR1-producing cells leading to their death. Interestingly, we show that the efficiency of the uptake of T-Fc-vcMMAE corresponds well with the cytotoxicity of the conjugate, but doesn't correlate with the FGFR1expression level.

CONCLUSION

Our results show that T-Fc-vcMMAE fulfills the key criteria for the successful cytotoxic drug carrier in a targeted approach against FGFR1-positive cancer cells. Furthermore, our data implicate that not solely expression level of the receptor, but rather its cellular trafficking should be taken into account for selection of suitable molecular targets and cancer models for successful ADC approach.

Interleukin-17 receptor D (Sef) is a multi-functional regulator of cell signaling

Interleukin-17 receptor D (IL17RD or IL-17RD) also known as Sef (similar expression to fibroblast growth factor), is a single pass transmembrane protein that is reported to regulate several signaling pathways . IL17RD was initially described as a feedback inhibitor of fibroblast growth factor (FGF) signaling during zebrafish and frog development. It was subsequently determined to regulate other receptor tyrosine kinase signaling cascades as well as several proinflammatory signaling pathways including Interleukin-17A (IL17A), Toll-like receptors (TLR) and Interleukin-1α (IL1α) in several vertebrate species including humans. This review will provide an overview of IL17RD regulation of signaling pathways and functions with emphasis on regulation of development and pathobiological conditions. We will also discuss gaps in our knowledge about IL17RD function to provide insight into opportunities for future investigation.

Loss of interleukin-17 receptor D promotes chronic inflammation-associated tumorigenesis

Interleukin-17 receptor D (IL-17RD), also known as similar expression to Fgf genes (SEF), is proposed to act as a signaling hub that negatively regulates mitogenic signaling pathways, like the ERK1/2 MAP kinase pathway, and innate immune signaling. The expression of IL-17RD is downregulated in certain solid tumors, which has led to the hypothesis that it may exert tumor suppressor functions. However, the role of IL-17RD in tumor biology remains to be studied in vivo. Here, we show that genetic disruption of Il17rd leads to the increased formation of spontaneous tumors in multiple tissues of aging mice. Loss of IL-17RD also promotes tumor development in a model of colitis-associated colorectal cancer, associated with an exacerbated inflammatory response. Colon tumors from IL-17RD-deficient mice are characterized by a strong enrichment in inflammation-related gene signatures, elevated expression of pro-inflammatory tumorigenic cytokines, such as IL-17A and IL-6, and increased STAT3 tyrosine phosphorylation. We further show that RNAi depletion of IL-17RD enhances Toll-like receptor and IL-17A signaling in colon adenocarcinoma cells. No change in the proliferation of normal or tumor intestinal epithelial cells was observed upon genetic inactivation of IL-17RD. Our findings establish IL-17RD as a tumor suppressor in mice and suggest that the protein exerts its function mainly by limiting the extent and duration of inflammation.

FGFR1 clustering with engineered tetravalent antibody improves the efficiency and modifies the mechanism of receptor internalization

Fibroblast growth factor receptor 1 (FGFR1) transmits signals through the plasma membrane regulating essential cellular processes like division, motility, metabolism, and death. Overexpression of FGFR1 is observed in numerous tumors and thus constitutes an attractive molecular target for selective cancer treatment. Targeted anti‐cancer therapies aim for the precise delivery of drugs into cancer cells, sparing the healthy ones and thus limiting unwanted side effects. One of the key steps in targeted drug delivery is receptor‐mediated endocytosis. Here, we show that the efficiency and the mechanism of FGFR1 internalization are governed by the spatial distribution of the receptor in the plasma membrane. Using engineered antibodies of different valency, we demonstrate that dimerization of FGFR1 with bivalent antibody triggers clathrin‐mediated endocytosis (CME) of the receptor. Clustering of FGFR1 into larger oligomers with tetravalent antibody stimulates fast and highly efficient uptake of the receptor that occurs via two distinct mechanisms: CME and dynamin‐dependent clathrin‐independent endocytic routes. Furthermore, we show that all endocytic pathways engaged in FGFR1 internalization do not require receptor activation. Our data provide novel insights into the mechanisms of intracellular trafficking of FGFR1 and constitute guidelines for development of highly internalizing antibody‐based drug carriers for targeted therapy of FGFR1‐overproducing cancers.

Resistance to MET/VEGFR2 Inhibition by Cabozantinib Is Mediated by YAP/TBX5-Dependent Induction of FGFR1 in Castration-Resistant Prostate Cancer

The overall goal of this study was to elucidate the role of FGFR1 induction in acquired resistance to MET and VEGFR2 inhibition by cabozantinib in prostate cancer (PCa) and leverage this understanding to improve therapy outcomes. The response to cabozantinib was examined in mice bearing patient-derived xenografts in which FGFR1 was overexpressed. Using a variety of cell models that reflect different PCa disease states, the mechanism underpinning FGFR1 signaling activation by cabozantinib was investigated. We performed parallel investigations in specimens from cabozantinib-treated patients to confirm our in vitro and in vivo data. FGFR1 overexpression was sufficient to confer resistance to cabozantinib. Our results demonstrate transcriptional activation of FGF/FGFR1 expression in cabozantinib-resistant models. Further analysis of molecular pathways identified a YAP/TBX5-driven mechanism of FGFR1 and FGF overexpression induced by MET inhibition. Importantly, knockdown of YAP and TBX5 led to decreased FGFR1 protein expression and decreased mRNA levels of FGFR1, FGF1, and FGF2. This association was confirmed in a cohort of hormone-naïve patients with PCa receiving androgen deprivation therapy and cabozantinib, further validating our findings. These findings reveal that the molecular basis of resistance to MET inhibition in PCa is FGFR1 activation through a YAP/TBX5-dependent mechanism. YAP and its downstream target TBX5 represent a crucial mediator in acquired resistance to MET inhibitors. Thus, our studies provide insight into the mechanism of acquired resistance and will guide future development of clinical trials with MET inhibitors.

The discovery of potent and stable short peptide FGFR1 antagonist for cancer therapy

Fibroblast growth factor receptor 1 (FGFR1) is one of the attractive pharmaceutical targets for cancer therapy. The FGFR1 targeting antagonist peptides, especially of the short peptides harbouring only coding amino acid might highlights promising aspects for their higher affinity, specificity and lower adverse reactions. However, most of peptides inhibitors remain in preclinical research, likely associating with their instability and short half-life. In this study, we found a stable short peptide inhibitor P48 and speculated that its stability might be related to its non-linear spatial structure. In addition, P48 could target the extracellular immunoglobulin domain of FGFR1, and effectively block the particular signaling pathways of FGFR1, which lead to the inhibition of cancer proliferation, invasion in vitro and restraint of tumor growth in vivo. Together, this study provided a promising FGFR1 inhibitor with the potential to be developed as an antitumor drug.

Cross-Talk between Fibroblast Growth Factor Receptors and Other Cell Surface Proteins

Fibroblast growth factors (FGFs) and their receptors (FGFRs) constitute signaling circuits that transmit signals across the plasma membrane, regulating pivotal cellular processes like differentiation, migration, proliferation, and apoptosis. The malfunction of FGFs/FGFRs signaling axis is observed in numerous developmental and metabolic disorders, and in various tumors. The large diversity of FGFs/FGFRs functions is attributed to a great complexity in the regulation of FGFs/FGFRs-dependent signaling cascades. The function of FGFRs is modulated at several levels, including gene expression, alternative splicing, posttranslational modifications, and protein trafficking. One of the emerging ways to adjust FGFRs activity is through formation of complexes with other integral proteins of the cell membrane. These proteins may act as coreceptors, modulating binding of FGFs to FGFRs and defining specificity of elicited cellular response. FGFRs may interact with other cell surface receptors, like G-protein-coupled receptors (GPCRs) or receptor tyrosine kinases (RTKs). The cross-talk between various receptors modulates the strength and specificity of intracellular signaling and cell fate. At the cell surface FGFRs can assemble into large complexes involving various cell adhesion molecules (CAMs). The interplay between FGFRs and CAMs affects cell–cell interaction and motility and is especially important for development of the central nervous system. This review summarizes current stage of knowledge about the regulation of FGFRs by the plasma membrane-embedded partner proteins and highlights the importance of FGFRs-containing membrane complexes in pathological conditions, including cancer.

Selected Golgi-Localized Proteins and Carcinogenesis: What Do We Know?

The role of the Golgi apparatus in carcinogenesis still remains unclear. A number of structural and functional cis-, medial-, and trans-Golgi proteins as well as a complexity of metabolic pathways which they mediate may indicate a central role of the Golgi apparatus in the development and progression of cancer. Pleiotropy of cellular function of the Golgi apparatus makes it a "metabolic heart" or a relay station of a cell, which combines multiple signaling pathways involved in carcinogenesis. Therefore, any damage to or structural abnormality of the Golgi apparatus, causing its fragmentation and/or biochemical dysregulation, results in an up- or downregulation of signaling pathways and may in turn promote tumor progression, as well as local nodal and distant metastases. Three alternative or parallel models of spatial and functional Golgi organization within tumor cells were proposed: (1) compacted Golgi structure, (2) normal Golgi structure with its increased activity, and (3) the Golgi fragmentation with ministacks formation. Regardless of the assumed model, the increased activity of oncogenesis initiators and promoters with inhibition of suppressor proteins results in an increased cell motility and migration, increased angiogenesis, significantly activated trafficking kinetics, proliferation, EMT induction, decreased susceptibility to apoptosis-inducing factors, and modulating immune response to tumor cell antigens. Eventually, this will lead to the increased metastatic potential of cancer cells and an increased risk of lymph node and distant metastases. This chapter provided an overview of the current state of knowledge of selected Golgi proteins, their role in cytophysiology as well as potential involvement in tumorigenesis.

Nonsteroidal FXR Ligands: Current Status and Clinical Applications

FXR agonists have demonstrated very promising clinical results in the treatment of liver disorders such as primary biliary cirrhosis (PBC), primary sclerosing cholangitis (PSC), and nonalcoholic steatohepatitis (NASH). NASH, in particular, is one of the last uncharted white territories in the pharma landscape, and there is a huge medical need and a large potential pharmaceutical market for a NASH pharmacotherapy. Clinical efficacy superior to most other treatment options was shown by FXR agonists such as obeticholic acid (OCA) as they improved various metabolic features including liver steatosis as well as liver inflammation and fibrosis. But OCA's clinical success comes with some major liabilities such as pruritus, high-density lipoprotein cholesterol (HDL_c) lowering, low-density lipoprotein cholesterol (LDL_c) increase, and a potential for drug-induced liver toxicity. Some of these effects can be attributed to on-target effects exerted by FXR, but with others it is not clear whether it is FXR- or OCA-related. Therefore a quest for novel, proprietary FXR agonists is ongoing with the aim to increase FXR potency and selectivity over other proteins and to overcome at least some of the OCA-associated clinical side effects through an improved pharmacology. In this chapter we will discuss the historical and ongoing efforts in the identification and development of nonsteroidal, which largely means non-bile acid-type, FXR agonists for clinical use.

Targeting Cellular Trafficking of Fibroblast Growth Factor Receptors as a Strategy for Selective Cancer Treatment

Fibroblast growth factor receptors (FGFRs) in response to fibroblast growth factors (FGFs) transmit signals across the cell membrane, regulating important cellular processes, like differentiation, division, motility, and death. The aberrant activity of FGFRs is often observed in various diseases, especially in cancer. The uncontrolled FGFRs' function may result from their overproduction, activating mutations, or generation of FGFRs' fusion proteins. Besides their typical subcellular localization on the cell surface, FGFRs are often found inside the cells, in the nucleus and mitochondria. The intracellular pool of FGFRs utilizes different mechanisms to facilitate cancer cell survival and expansion. In this review, we summarize the current stage of knowledge about the role of FGFRs in oncogenic processes. We focused on the mechanisms of FGFRs' cellular trafficking-internalization, nuclear translocation, and mitochondrial targeting, as well as their role in carcinogenesis. The subcellular sorting of FGFRs constitutes an attractive target for anti-cancer therapies. The blocking of FGFRs' nuclear and mitochondrial translocation can lead to the inhibition of cancer invasion. Moreover, the endocytosis of FGFRs can serve as a tool for the efficient and highly selective delivery of drugs into cancer cells overproducing these receptors. Here, we provide up to date examples how the cellular sorting of FGFRs can be hijacked for selective cancer treatment.

Prostate Organogenesis

The prostate is a male exocrine gland that secretes components of the seminal fluid. In men, prostate tumors are one of the most prevalent cancers. Studies on the development of the prostate have given a better understanding of the processes and genes that are important in the formation of this organ and have provided insights into the mechanisms of prostate tumorigenesis. These developmental studies have provided evidence that some of the genes and signaling pathways involved in development are reactivated or deregulated during prostate cancer. The prostate goes through a number of different stages during organogenesis, which include organ specification, epithelial budding, branching morphogenesis, canalization, and cytodifferentiation. During development, these processes are tightly regulated, many of which are controlled by the male hormone androgens. The majority of prostate tumors remain hormone regulated, and antiandrogen therapy is a first-line therapy, highlighting the important link between prostate organogenesis and cancer. In this review, we describe some of the data on genes that have important roles during prostate development that also have strong evidence linking them to prostate cancer.

FGF-2 is a driving force for chromosomal instability and a stromal factor associated with adverse clinico-pathological features in prostate cancer

BACKGROUND

There is mounting evidence to suggest that stromal cells play an integral role in the progression of prostate cancer (PCa). One of the most frequently altered growth factors in PCa is fibroblast growth factor-2 (FGF-2). It has previously been proposed that early stages of PCa are characterized by a primarily exogenous, that is, stromal cell-derived FGF-2 production, whereas advanced tumors rely more on an autocrine FGF-2 production. Prostate cancer progression is characterized by an increase of genomic instability including aneuploidy and structural chromosomal alterations. Herein, we address 2 problems that have not been comprehensively answered. First, we ask whether exogenous FGF-2 can directly drive genomic instability to promote PCa progression. Second, we investigate whether and to what extent stromal FGF-2 expression is maintained in advanced PCa and whether this influences tumor progression and patient prognosis.

METHODS

In vitro experiments to investigate the role of FGF-2 in numerical and structural chromosomal instability were performed using immunofluorescence microscopy, fluorescence in situ hybridization and single cell electrophoresis. A human patient-derived xenograft mouse model recapitulating osteoblastic PCa bone metastasis was used for in vivo validation experiments. The prognostic role of stromal FGF-2 expression was analyzed using immunohistochemical staining of a tissue microarray with primary tumor specimens from 162 predominantly high-risk patients with PCa.

RESULTS

Our results show that FGF-2 not only rapidly induces mitotic defects and numerical chromosomal imbalances but also an enhanced DNA breakage to promote chromosomal instability. Using the patient-derived xenograft model, we show that a deregulation of the FGF axis results in an increase of mitotic aberrations as well as DNA damage checkpoint activation in vivo. The FGFR inhibitor dovitinib was found to reduce numerical chromosomal instability as well as DNA breakage, thus underscoring the relevance of the FGF axis in promoting genomic instability. An overexpression of tumor cell-associated FGF-2 was detected in 52 of 162 patients (32.1%), whereas a stromal overexpression was found in 27 of 165 patients (16%). Remarkably, a strong stromal FGF-2 expression was associated with a significantly higher clinical stage and higher biochemical recurrence rate. Patients with strong stromal FGF-2 expression also had a significantly worse biochemical recurrence-free survival.

CONCLUSIONS

Our results underscore that exogenous FGF-2 can shape PCa cell genomes and that stromal FGF-2 expression is detectable in a sizeable proportion of advanced PCa where it is associated with adverse clinico-pathological features. Our results highlight the impact of the tumor stroma on malignant progression and provide a rationale for a further exploration of components of the tumor stroma as therapeutic targets in PCa.

Combination treatment of prostate cancer with FGF receptor and AKT kinase inhibitors

Activation of the PI3K/AKT pathway occurs in the vast majority of advanced prostate cancers (PCas). Activation of fibroblast growth factor receptor (FGFR) signaling occurs in a wide variety of malignancies, including PCa. RNA-Seq of castration resistant PCa revealed expression of multiple FGFR signaling components compatible with FGFR signaling in all cases, with multiple FGF ligands expressed in 90% of cases. Immunohistochemistry confirmed FGFR signaling in the majority of xenografts and advanced PCas. AZD5363, an AKT kinase inhibitor and AZD4547, a FGFR kinase inhibitor are under active clinical development. We therefore sought to determine if these two drugs have additive effects in PCa models. The effect of both agents, singly and in combination was evaluated in a variety of PCa cell lines in vitro and in vivo. All cell lines tested responded to both drugs with decreased invasion, soft agar colony formation and growth in vivo, with additive effects seen with combination treatment. Activation of the FGFR, AKT, ERK and STAT3 pathways was examined in treated cells. AZD5363 inhibited AKT signaling and increased FGFR1 signaling, which partially compensated for decreased AKT kinase activity. While AZD4547 could effectively block the ERK pathway, combination treatment was needed to completely block STAT3 activation. Thus combination treatment with AKT and FGFR kinase inhibitors have additive effects on malignant phenotypes in vitro and in vivo by inhibiting multiple signaling pathways and mitigating the compensatory upregulation of FGFR signaling induced by AKT kinase inhibition. Our studies suggest that co-targeting these pathways may be efficacious in advanced PCa.

Loss of TGF-β signaling in osteoblasts increases basic-FGF and promotes prostate cancer bone metastasis

TGF-β plays a central role in prostate cancer (PCa) bone metastasis, and it is crucial to understand the bone cell-specific role of TGF-β signaling in this process. Thus, we used knockout (KO) mouse models having deletion of the Tgfbr2 gene specifically in osteoblasts (Tgfbr2^Col1CreERT KO) or in osteoclasts (Tgfbr2^LysMCre KO). We found that PCa-induced bone lesion development was promoted in the Tgfbr2^Col1CreERT KO mice, but was inhibited in the Tgfbr2^LysMCre KO mice, relative to their respective control Tgfbr2^FloxE2 littermates. Since metastatic PCa cells attach to osteoblasts when colonized in the bone microenvironment, we focused on the mechanistic studies using the Tgfbr2^Col1CreERT KO mouse model. We found that bFGF was upregulated in osteoblasts from PC3-injected tibiae of Tgfbr2^Col1CreERT KO mice and correlated with increased tumor cell proliferation, angiogenesis, amounts of cancer-associated fibroblasts and osteoclasts. In vitro studies showed that osteoblastogenesis was inhibited, osteoclastogenesis was stimulated, but PC3 viability was not affected, by bFGF treatments. Lastly, the increased PC3-induced bone lesions in Tgfbr2^Col1CreERT KO mice were significantly attenuated by blocking bFGF using neutralizing antibody, suggesting bFGF is a promising target inhibiting bone metastasis.

Delivery of the gene encoding the tumor suppressor Sef into prostate tumors by therapeutic-ultrasound inhibits both tumor angiogenesis and growth

Carcinomas constitute over 80% of all human cancer types with no effective therapy for metastatic disease. Here, we demonstrate, for the first time, the efficacy of therapeutic-ultrasound (TUS) to deliver a human tumor suppressor gene, hSef-b, to prostate tumors in vivo. Sef is downregulated in various human carcinomas, in a manner correlating with tumor aggressiveness. In vitro, hSef-b inhibited proliferation of TRAMP C2 cells and attenuated activation of ERK/MAPK and the master transcription factor NF-κB in response to FGF and IL-1/TNF, respectively. In vivo, transfection efficiency of a plasmid co-expressing hSef-b/eGFP into TRAMP C2 tumors was 14.7 ± 2.5% following a single TUS application. Repeated TUS treatments with hSef-b plasmid, significantly suppressed prostate tumor growth (60%) through inhibition of cell proliferation (60%), and reduction in blood vessel density (56%). In accordance, repeated TUS-treatments with hSef-b significantly inhibited in vivo expression of FGF2 and MMP-9. FGF2 is a known mitogen, and both FGF2/MMP-9 are proangiogenic factors. Taken together our results strongly suggest that hSef-b acts in a cell autonomous as well as non-cell autonomous manner. Moreover, the study demonstrates the efficacy of non-viral TUS-based hSef-b gene delivery approach for the treatment of prostate cancer tumors, and possibly other carcinomas where Sef is downregulated.

FGF23 promotes prostate cancer progression

Prostate cancer is the most common cancer in US men and the second leading cause of cancer deaths. Fibroblast growth factor 23 (FGF23) is an endocrine FGF, normally expressed by osteocytes, which plays a critical role in phosphate homeostasis via a feedback loop involving the kidney and vitamin D. We now show that FGF23 is expressed as an autocrine growth factor in all prostate cancer cell lines tested and is present at increased levels in prostate cancer tissues. Exogenous FGF23 enhances proliferation, invasion and anchorage independent growth in vitro while FGF23 knockdown in prostate cancer cell lines decreases these phenotypes. FGF23 knockdown also decreases tumor growth in vivo. Given that classical FGFs and FGF19 are also increased in prostate cancer, we analyzed expression microarrays hybridized with RNAs from of LNCaP cells stimulated with FGF2, FGF19 or FGF23. The different FGF ligands induce overlapping as well as unique patterns of gene expression changes and thus are not redundant. We identified multiple genes whose expression is altered by FGF23 that are associated with prostate cancer initiation and progression. Thus FGF23 can potentially also act as an autocrine, paracrine and/or endocrine growth factor in prostate cancer that can promote prostate cancer progression.

Aberrant expression of hSef and Sprouty4 in endometrial adenocarcinoma

Fibroblast growth factor (FGF) 2-mediated signaling of the mitogen-activated protein kinase/RAS/extracellular signal-regulated kinase 1/2 pathway is a critical modulator in angiogenesis and is therefore essential for the pathogenesis of endometrial carcinoma. Human similar expression to FGFs (hSef) and Sprouty4 have each been reported to be negative regulators of FGF signaling. The aim of the present study was to investigate the expression of hSef and Sprouty4 in human endometrial adenocarcinoma. Using immunohistochemistry analysis, the expression of hSef and Sprouty4 was detected in human endometrial adenocarcinomas. Increased hSef expression was found to be present in endometrial adenocarcinomas. In addition, decreased hSef expression was identified in the blood vessels of endometrial adenocarcinoma samples. However, the expression of Sprouty4 was downregulated in human endometrial adenocarcinoma. Aberrant expression of hSef and Sprouty4 are involved in the pathogenesis of human endometrial adenocarcinoma.

Is fibroblast growth factor receptor 4 a suitable target of cancer therapy?

Fibroblast growth factors (FGF) and their tyrosine kinase receptors (FGFR) support cell proliferation, survival and migration during embryonic development, organogenesis and tissue maintenance and their deregulation is frequently observed in cancer development and progression. Consequently, increasing efforts are focusing on the development of strategies to target FGF/FGFR signaling for cancer therapy. Among the FGFRs the family member FGFR4 is least well understood and differs from FGFRs1-3 in several aspects. Importantly, FGFR4 deletion does not lead to an embryonic lethal phenotype suggesting the possibility that its inhibition in cancer therapy might not cause grave adverse effects. In addition, the FGFR4 kinase domain differs sufficiently from those of FGFRs1-3 to permit development of highly specific inhibitors. The oncogenic impact of FGFR4, however, is not undisputed, as the FGFR4-mediated hormonal effects of several FGF ligands may also constitute a tissue-protective tumor suppressor activity especially in the liver. Therefore it is the purpose of this review to summarize all relevant aspects of FGFR4 physiology and pathophysiology and discuss the options of targeting this receptor for cancer therapy.

Targeting the heparin-binding domain of fibroblast growth factor receptor 1 as a potential cancer therapy

Background

Aberrant activation of fibroblast growth factor receptors (FGFRs) deregulates cell proliferation and promotes cell survival, and may predispose to tumorigenesis. Therefore, selective inactivation of FGFRs is an important strategy for cancer therapy. Here as a proof-of-concept study, we developed a FGFR1 neutralizing antisera, IMB-R1, employing a novel strategy aimed at preventing the access of essential heparan sulfate (HS) co-receptors to the heparin-binding domain on FGFR1.

Methods

The mRNA and protein expression level of FGFR1 and other FGFRs were examined in several lines of breast cancer and osteosarcoma cells and corresponding normal cells using Taqman real-time quantitative PCR and Western blot analysis. The specificity of IMB-R1 against FGFR1 was assessed with various ELISA-based approaches and Receptor Tyrosine Kinase array. Proliferation assay and apoptosis analysis were performed to assess the effect of IMB-R1 on cancer cell growth and apoptosis, respectively, in comparison with known FGFR1 inhibitors. The IMB-R1 induced alteration of intracellular signaling and gene expression were analysed using Western blot and microarray approaches. Immunohistochemical staining of FGFR1 using IMB-R1 were carried out in different cancer tissues from clinical patients. Throughout the study, statistical differences were determined by Student’s t test where appropriate and reported when a p value was less than 0.05.

Results

We demonstrate that IMB-R1 is minimally cross-reactive for other FGFRs, and that it potently and specifically inhibits binding of heparin to FGFR1. Furthermore, IMB-R1 blocks the interaction of FGF2 with FGFR1, the kinase activity of FGFR1 and activation of intracellular FGFR signaling. Cancer cells treated with IMB-R1 displayed impaired FGF2 signaling, were unable to grow and instead underwent apoptosis. IMB-R1-induced cell death correlated with a disruption of antioxidative defense networks and increased expression of several tumor suppressors and apoptotic proteins, including p53. Immunostaining with IMB-R1 was stronger in human cancer tissues in which the FGFR1 gene is amplified.

Conclusion

Our study suggests that blocking HS interaction with the heparin-binding domains of FGFR1 inhibited cancer cell growth, which can be an attractive strategy to inactivate cancer-related heparin-binding proteins.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-015-0391-4) contains supplementary material, which is available to authorized users.

FGF19 promotes progression of prostate cancer

BACKGROUND

Fibroblast growth factor (FGF) signaling pathways have been reported to play important roles in prostate cancer (PCa) progression. FGF19 is one of a subfamily of FGFs that circulate in serum and act in an endocrine manner. Our objective was to investigate its role in the progression of PCa.

METHODS

The effect of FGF19 on the proliferation and epithelial-mesenchymal transition of LNCaP and PC3 cells was examined using MTT assay and Western blotting. Serum concentration of FGF19 was measured by ELISA in 209 patients with PCa, and the association between clinicopathological features and the presence of FGF19-positive cells in tissues derived from 155 patients who undergone radical prostatectomy was investigated.

RESULTS

Under androgen-deprived conditions achieved by incubation in medium with FGF19, the expression of N-cadherin in LNCaP cells was enhanced, that of E-cadherin and caspase 3 was suppressed, and the viability of LNCaP and PC3 cells was significantly enhanced. Significantly higher levels of PSA were recorded in the group determined by immunohistochemistry staining to be FGF19-positive (P = 0.0046). The 5-year biochemical recurrence-free survival rate after radical prostatectomy was 46.4% in the FGF19-positive group and 70.0% in the FGF19-negative group (P = 0.0027). In multivariate analysis, the presence of FGF19-positive tissues was an independent factor for worse prognosis after radical prostatectomy (P = 0.0052). Serum FGF19 levels in high Gleason grade group were higher than that in low Gleason grade group (P = 0.0009).

CONCLUSIONS

FGF19 might be associated with biochemical recurrence after radical prostatectomy by promoting cell proliferation and epithelial-mesenchymal transition of PCa.

Crosstalk between KIT and FGFR3 Promotes Gastrointestinal Stromal Tumor Cell Growth and Drug Resistance

Kinase inhibitors such as imatinib have dramatically improved outcomes for patients with gastrointestinal stromal tumor (GIST), but many patients develop resistance to these treatments. Although in some patients this event corresponds with mutations in the GIST driver oncogenic kinase KIT, other patients develop resistance without KIT mutations. In this study, we address this patient subset in reporting a functional dependence of GIST on the FGF receptor FGFR3 and its crosstalk with KIT in GIST cells. Addition of the FGFR3 ligand FGF2 to GIST cells restored KIT phosphorylation during imatinib treatment, allowing sensitive cells to proliferate in the presence of the drug. FGF2 expression was increased in imatinib-resistant GIST cells, the growth of which was blocked by RNAi-mediated silencing of FGFR3. Moreover, combining KIT and FGFR3 inhibitors synergized to block the growth of imatinib-resistant cells. Signaling crosstalk between KIT and FGFR3 activated the MAPK pathway to promote resistance to imatinib. Clinically, an IHC analysis of tumor specimens from imatinib-resistant GIST patients revealed a relative increase in FGF2 levels, with a trend toward increased expression in imatinib-naïve samples consistent with possible involvement in drug resistance. Our findings provide a mechanistic rationale to evaluate existing FGFR inhibitors and multikinase inhibitors that target FGFR3 as promising strategies to improve treatment of patients with GIST with de novo or acquired resistance to imatinib.

Expression and regulation of the tumor suppressor, SEF, during folliculogenesis in humans and mice

Similar expression to FGF (Sef or IL17-RD), is a tumor suppressor and an inhibitor of growth factors as well as of pro-inflammatory cytokine signaling. In this study, we examined the regulation of Sef expression by gonadotropins during ovarian folliculogenesis. In sexually immature mice, in situ hybridization (ISH) localized Sef gene expression to early developing oocytes and granulosa cells (GC) but not to theca cells. Sef was also expressed in mouse ovarian endothelial cells, in the fallopian tube epithelium as well as in adipose tissue venules. SEF protein expression, determined by immunohistochemistry (IHC), correlated well with Sef mRNA expression in GC, while differential expression was noticed in oocytes. High Sef mRNA but undetectable SEF protein levels were observed in the oocytes of primary/secondary follicles, while an inverse correlation was found in the oocytes of preantral and small antral follicles. Sef mRNA expression dropped after pregnant mare's serum gonadotropin (PMSG) administration, peaked at 6-8 h after human chorionic gonadotropin (hCG) treatment, and declined by 12 h after this treatment. ISH and IHC localized the changes to oocytes and mural GC following PMSG treatment, whereas Sef expression increased in mural GC and declined in granulosa-lutein cells upon hCG treatment. The ovarian expression of SEF was confirmed using human samples. ISH localized SEF transcripts to human GC of antral follicles but not to corpora lutea. Furthermore, SEF mRNA was detected in human GC recovered from preovulatory follicles. These results are the first to demonstrate SEF expression in a healthy ovary during folliculogenesis. Hormonal regulation of its expression suggests that SEF may be an important factor involved in intra-ovarian control mechanisms.

Upregulation of FGFR1 expression is associated with parathyroid carcinogenesis in HPT-JT syndrome due to an HRPT2 splicing mutation

Mutations of the HRPT2 gene, which are responsible for hyperparathyroidism-jaw tumor (HPT-JT) syndrome, have been implicated in the development of a high proportion of parathyroid carcinomas. The aim of this study was to investigate differences in expression of the most important genes connected with parathyroid carcinoma between HPT-JT syndrome due to an HRPT2 splicing mutation, normal parathyroid tissue and sporadic parathyroid adenoma. Total RNAs were extracted from parathyroid carcinoma in HPT-JT syndrome harbouring HRPT2 splicing mutation or sporadic parathyroid adenoma and normal parathyroid gland, and subjected to Illumina DASL-based gene expression assay. Unsupervised hierarchical clustering analysis was used to compare gene expression in HPT-JT syndrome, sporadic parathyroid adenoma and normal parathyroid glands. We identified differentially regulated genes in HPT-JT syndrome and sporadic parathyroid adenoma relative to normal parathyroid glands using a combination of Welch's t-test and fold-change analysis. Quantitative PCR, RT-PCR and IHC were used for validation. Sixteen genes differentially regulated in the parathyroid carcinoma were associated with signal pathways, MAPK, regulation of actin cytoskeleton, prostate cancer and apoptosis. FGFR1 expression was confirmed to be significantly upregulated by validation experiments. Our gene expression profiling experiments suggest that upregulated FGFR1 expression appears to be associated with parathyroid carcinoma in HPT-JT syndrome due to an HRPT2 splicing mutation.

Genomic aberrations in the FGFR pathway: opportunities for targeted therapies in solid tumors

The fibroblast growth factor receptor (FGFR) cascade plays crucial roles in tumor cell proliferation, angiogenesis, migration and survival. Accumulating evidence suggests that in some tumor types, FGFRs are bona fide oncogenes to which cancer cells are addicted. Because FGFR inhibition can reduce proliferation and induce cell death in a variety of in vitro and in vivo tumor models harboring FGFR aberrations, a growing number of research groups have selected FGFRs as targets for anticancer drug development. Multikinase FGFR/vascular endothelial growth factor receptor (VEGFR) inhibitors have shown promising activity in breast cancer patients with FGFR1 and/or FGF3 amplification. Early clinical trials with selective FGFR inhibitors, which may overcome the toxicity constraints raised by multitarget kinase inhibition, are recruiting patients with known FGFR(1-4) status based on genomic screens. Preliminary signs of antitumor activity have been demonstrated in some tumor types, including squamous cell lung carcinomas. Rational combination of targeted therapies is expected to further increase the efficacy of selective FGFR inhibitors. Herein, we discuss unsolved questions in the clinical development of these agents and suggest guidelines for management of hyperphosphatemia, a class-specific mechanism-based toxicity. In addition, we propose standardized definitions for FGFR1 and FGFR2 gene amplification based on in situ hybridization methods. Extended access to next-generation sequencing platforms will facilitate the identification of diseases in which somatic FGFR(1-4) mutations, amplifications and fusions are potentially driving cancer cell viability, further strengthening the role of FGFR signaling in cancer biology and providing more possibilities for the therapeutic application of FGFR inhibitors.

Functional roles of fibroblast growth factor receptors (FGFRs) signaling in human cancers

The fibroblast growth factor receptors (FGFRs) regulate important biological processes including cell proliferation and differentiation during development and tissue repair. Over the past decades, numerous pathological conditions and developmental syndromes have emerged as a consequence of deregulation in the FGFRs signaling network. This review aims to provide an overview of FGFR family, their complex signaling pathways in tumorigenesis, and the current development and application of therapeutics targeting the FGFRs signaling for treatment of refractory human cancers.

Genetic variants in the fibroblast growth factor pathway as potential markers of ovarian cancer risk, therapeutic response, and clinical outcome

BACKGROUND

The fibroblast growth factor (FGF) and FGF receptor (FGFR) axis plays a critical role in tumorigenesis, but little is known of its influence in ovarian cancer. We sought to determine the association of genetic variants in the FGF pathway with risk, therapeutic response, and survival of patients with ovarian cancer.

METHODS

We matched 339 non-Hispanic white ovarian cancer cases with 349 healthy controls and genotyped them for 183 single-nucleotide polymorphisms (SNPs) from 24 FGF (fibroblast growth factor) and FGFR (fibroblast growth factor receptor) genes. Genetic associations for the main effect, gene-gene interactions, and the cumulative effect were determined.

RESULTS

Multiple SNPs in the FGF-FGFR axis were associated with an increased risk of ovarian cancer. In particular, FGF1 [fibroblast growth factor 1 (acidic)] SNP rs7727832 showed the most significant association with ovarian cancer (odds ratio, 2.27; 95% CI, 1.31-3.95). Ten SNPs were associated with a reduced risk of ovarian cancer. FGF18 (fibroblast growth factor 18) SNP rs3806929, FGF7 (fibroblast growth factor 7) SNP rs9920722, FGF23 (fibroblast growth factor 23) SNP rs12812339, and FGF5 (fibroblast growth factor 5) SNP rs3733336 were significantly associated with a favorable treatment response, with a reduction of risk of nonresponse of 40% to 60%. Eleven SNPs were significantly associated with overall survival. Of these SNPs, FGF23 rs7961824 was the most significantly associated with improved prognosis (hazard ratio, 0.55; 95% CI, 0.39-0.78) and was associated with significantly longer survival durations, compared with individuals with the common genotype at this locus (58.1 months vs. 38.0 months, P = 0.005). Survival tree analysis revealed FGF2 rs167428 as the primary factor contributing to overall survival.

CONCLUSIONS

Significant associations of genetic variants in the FGF pathway were associated with ovarian cancer risk, therapeutic response, and survival. The discovery of multiple SNPs in the FGF-FGFR pathway provides a molecular approach for risk assessment, monitoring therapeutic response, and prognosis.

Targeting fibroblast growth factor pathways in prostate cancer

Advanced prostate cancer carries a poor prognosis and novel therapies are needed. Research has focused on identifying mechanisms that promote angiogenesis and cellular proliferation during prostate cancer progression from the primary tumor to bone-the principal site of prostate cancer metastases. One candidate pathway is the fibroblast growth factor (FGF) axis. Aberrant expression of FGF ligands and FGF receptors leads to constitutive activation of multiple downstream pathways involved in prostate cancer progression including mitogen-activated protein kinase, phosphoinositide 3-kinase, and phospholipase Cγ. The involvement of FGF pathways in multiple mechanisms relevant to prostate tumorigenesis provides a rationale for the therapeutic blockade of this pathway, and two small-molecule tyrosine kinase inhibitors-dovitinib and nintedanib-are currently in phase II clinical development for advanced prostate cancer. Preliminary results from these trials suggest that FGF pathway inhibition represents a promising new strategy to treat castrate-resistant disease.

Small molecule inhibition of fibroblast growth factor receptors in cancer

Fibroblast growth factors (FGFs) signal through FGF receptors (FGFRs), which are a sub-family of the superfamily of receptor tyrosine kinases, to regulate human development and metabolism. Uncontrolled FGF signaling is responsible for diverse array of developmental disorders, most notably skeletal syndromes due to FGFR gain-of-function mutations. Studies in the last few years have provided significant evidence for the importance of FGF signaling in the pathogenesis of diverse cancers, including endometrial and bladder cancers. FGFs are both potent mitogenic and angiogenic factors and can contribute to carcinogenesis by stimulating cell proliferation and tumor angiogenesis. Gene knockout and pharmacological inhibition of FGFRs in in vivo and in vitro models validate FGFRs as a target for cancer treatment. Considerable efforts are being expended to develop specific, small-molecule inhibitors for treating FGFR-driven cancers. Recent reviews on the FGF/FGFR system have focused primarily on signaling, pathophysiology, and functions in cancer. In this article, we review the key roles of FGFR in cancer, provide an update on the status of clinical trials with small-molecule FGFR inhibitors, and discuss how the current structural data on FGFR kinases guide the design and characterization of new FGFR inhibitors.

The role of endosomal signaling triggered by metastatic growth factors in tumor progression

Within tumor microenvironment, a lot of growth factors such as hepatocyte growth factor and epidermal growth factor may induce similar signal cascade downstream of receptor tyrosine kinase (RTK) and trigger tumor metastasis synergistically. In the past decades, the intimate relationship of RTK-mediated receptor endocytosis with signal transduction was well established. In general, most RTK undergoes clathrin-dependent endocytosis and/or clathrin-independent endocytosis. The internalized receptors may sustain the signaling within early endosome, recycling to plasma membrane for subsequent ligand engagement or sorting to late endosomes/lysosome for receptor degradation. Moreover, receptor endocytosis influences signal transduction in a temporal and spatial manner for periodical and polarized cellular processes such as cell migration. The endosomal signalings triggered by various metastatic factors are quite similar in some critical points, which are essential for triggering cell migration and tumor progression. There are common regulators for receptor endocytosis including dynamin, Rab4, Rab5, Rab11 and Cbl. Moreover, many critical regulators within the RTK signal pathway such as Grb2, p38, PKC and Src were also modulators of endocytosis. In the future, these may constitute a new category of targets for prevention of tumor metastasis.

Endocrine fibroblast growth factor FGF19 promotes prostate cancer progression

Prostate cancer is the most common visceral malignancy and the second leading cause of cancer deaths in US men. There is broad evidence that fibroblast growth factor (FGF) receptors are important in prostate cancer initiation and progression, but the contribution of particular FGFs in this disease is not fully understood. The FGF family members FGF19, FGF21, and FGF23 comprise a distinct subfamily that circulate in serum and act in an endocrine manner. These endocrine FGFs require α-Klotho (KL) and/or β-Klotho (KLB), two related single-pass transmembrane proteins restricted in their tissue distribution, to act as coreceptors along with classic FGF receptors (FGFR) to mediate potent biologic activity. Here we show that FGF19 is expressed in primary and metastatic prostate cancer tissues, where it functions as an autocrine growth factor. Exogenous FGF19 promoted the growth, invasion, adhesion, and colony formation of prostate cancer cells at low ligand concentrations. FGF19 silencing in prostate cancer cells expressing autocrine FGF19 decreased invasion and proliferation in vitro and tumor growth in vivo. Consistent with these observations, KL and/or KLB were expressed in prostate cancer cells in vitro and in vivo, raising the possibility that additional endocrine FGFs may also exert biologic effects in prostate cancer. Our findings support the concept that therapies targeting FGFR signaling may have efficacy in prostate cancer and highlight FGF19 as a relevant endocrine FGF in this setting.

Sef is an inhibitor of proinflammatory cytokine signaling, acting by cytoplasmic sequestration of NF-κB

The NF-κB transcription factor controls diverse biological processes. According to the classical model, NF-κB is retained in the cytoplasm of resting cells via binding to inhibitory, IκB proteins and translocates into the nucleus upon their ligand-induced degradation. Here we reveal that Sef, a known tumor suppressor and inhibitor of growth factor signaling, is a spatial regulator of NF-κB. Sef expression is regulated by the proinflammatory cytokines tumor necrosis factor and interleukin-1, and Sef specifically inhibits "classical" NF-κB (p50:p65) activation by these ligands. Like IκBs, Sef sequesters NF-κB in the cytoplasm of resting cells. However, contrary to IκBs, Sef continues to constrain NF-κB nuclear entry upon ligand stimulation. Accordingly, endogenous Sef knockdown markedly enhances stimulus-induced NF-κB nuclear translocation and consequent activity. This study establishes Sef as a feedback antagonist of proinflammatory cytokines and highlights its potential to regulate the crosstalk between proinflammatory cytokine receptors and receptor tyrosine kinases.

Targeting fibroblast growth factor receptor signaling inhibits prostate cancer progression

PURPOSE

Extensive correlative studies in human prostate cancer as well as studies in vitro and in mouse models indicate that fibroblast growth factor receptor (FGFR) signaling plays an important role in prostate cancer progression. In this study, we used a probe compound for an FGFR inhibitor, which potently inhibits FGFR-1-3 and significantly inhibits FGFR-4. The purpose of this study is to determine whether targeting FGFR signaling from all four FGFRs will have in vitro activities consistent with inhibition of tumor progression and will inhibit tumor progression in vivo.

EXPERIMENTAL DESIGN

Effects of AZ8010 on FGFR signaling and invasion were analyzed using immortalized normal prostate epithelial (PNT1a) cells and PNT1a overexpressing FGFR-1 or FGFR-4. The effect of AZ8010 on invasion and proliferation in vitro was also evaluated in prostate cancer cell lines. Finally, the impact of AZ8010 on tumor progression in vivo was evaluated using a VCaP xenograft model.

RESULTS

AZ8010 completely inhibits FGFR-1 and significantly inhibits FGFR-4 signaling at 100 nmol/L, which is an achievable in vivo concentration. This results in marked inhibition of extracellular signal-regulated kinase (ERK) phosphorylation and invasion in PNT1a cells expressing FGFR-1 and FGFR-4 and all prostate cancer cell lines tested. Treatment in vivo completely inhibited VCaP tumor growth and significantly inhibited angiogenesis and proliferation and increased cell death in treated tumors. This was associated with marked inhibition of ERK phosphorylation in treated tumors.

CONCLUSIONS

Targeting FGFR signaling is a promising new approach to treating aggressive prostate cancer.

Sef downregulation by Ras causes MEK1/2 to become aberrantly nuclear localized leading to polyploidy and neoplastic transformation

Subcellular trafficking of key oncogenic signal pathway components is likely to be crucial for neoplastic transformation, but little is known about how such trafficking processes are spatially controlled. In this study, we show how Ras activation causes aberrant nuclear localization of phosphorylated mitogen-activated protein (MAP)/extracellular signal-regulated kinase (ERK; MEK) MEK1/2 to drive neoplastic transformation. Phosphorylated MEK1/2 was aberrantly located within the nucleus of primary colorectal tumors and human colon cancer cells, and oncogenic activation of Ras was sufficient to induce nuclear accumulation of phosphorylated MEK1/2 and ERK1/2 in intestinal epithelial cells. Enforced nuclear localization of MEK1 in epithelial cells or fibroblasts was sufficient for hyperactivation of ERK1/2, thereby driving cell proliferation, chromosomal polyploidy, and tumorigenesis. Notably, Ras-induced nuclear accumulation of activated MEK1/2 was reliant on downregulation of the spatial regulator Sef, the reexpression of which was sufficient to restore normal MEK1/2 localization and a reversal of Ras-induced proliferation and tumorigenesis. Taken together, our findings indicate that Ras-induced downregulation of Sef is an early oncogenic event that contributes to genetic instability and tumor progression by sustaining nuclear ERK1/2 signaling.

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.

Role and expression of FRS2 and FRS3 in prostate cancer

Background

FGF receptor substrates (FRS2 and FRS3) are key adaptor proteins that mediate FGF-FGFR signalling in benign as well as malignant tissue. Here we investigated FRS2 and FRS3 as a means of disrupting global FGF signalling in prostate cancer.

Methods

FRS2 and FRS3 manipulation was investigated in vitro using over-expression, knockdown and functional assays. FRS2 and FRS3 expression was profiled in cell lines and clinical tumors of different grades.

Results

In a panel of cell lines we observed ubiquitous FRS2 and FRS3 transcript and protein expression in both benign and malignant cells. We next tested functional redundancy of FRS2 and FRS3 in prostate cancer cells. In DU145 cells, specific FRS2 suppression inhibited FGF induced signalling. This effect was not apparent in cells stably over-expressing FRS3. Indeed FRS3 over-expression resulted in enhanced proliferation (p = 0.005) compared to control cells. Given this functional redundancy, we tested the therapeutic principle of dual targeting of FRS2 and FRS3 in prostate cancer. Co-suppression of FRS2 and FRS3 significantly inhibited ERK activation with a concomitant reduction in cell proliferation (p < 0.05), migration and invasion (p < 0.05). Synchronous knockdown of FRS2 and FRS3 with exposure to cytotoxic irradiation resulted in a significant reduction in prostate cancer cell survival compared to irradiation alone (p < 0.05). Importantly, this synergistic effect was not observed in benign cells. Finally, we investigated expression of FRS2 and FRS3 transcript in a cohort of micro-dissected tumors of different grades as well as by immunohistochemistry in clinical biopsies. Here, we did not observe any difference in expression between benign and malignant biopsies.

Conclusions

These results suggest functional overlap of FRS2 and FRS3 in mediating mitogenic FGF signalling in the prostate. FRS2 and FRS3 are not over-expressed in tumours but targeted dual inhibition may selectively adversely affect malignant but not benign prostate cells.

Application of a novel score test for genetic association incorporating gene-gene interaction suggests functionality for prostate cancer susceptibility regions

AIMS

We introduce an innovative multilocus test for disease association. It is an extension of an existing score test that gains power over alternative methods by incorporating a parsimonious one-degree-of-freedom model for interaction. We use our method in applications designed to detect interactions that generate hypotheses about the functionality of prostate cancer (PRCA) susceptibility regions.

METHODS

Our proposed score test is designed to gain additional power through the use of a retrospective likelihood that exploits an assumption of independence between unlinked loci in the underlying population. Its performance is validated through simulation. The method is used in conditional scans with data from stage II of the Cancer Genetic Markers of Susceptibility PRCA genome-wide association study.

RESULTS

Our proposed method increases power to detect susceptibility loci in diverse settings. It identified two high-ranking, biologically interesting interactions: (1) rs748120 of NR2C2 and subregions of 8q24 that contain independent susceptibility loci specific to PRCA and (2) rs4810671 of SULF2 and both JAZF1 and HNF1B that are associated with PRCA and type 2 diabetes.

CONCLUSIONS

Our score test is a promising multilocus tool for genetic epidemiology. The results of our applications suggest functionality for poorly understood PRCA susceptibility regions. They motivate replication study.

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.

Similar expression to FGF (Sef) reduces endometrial adenocarcinoma cells proliferation via inhibiting fibroblast growth factor 2-mediated MAPK/ERK signaling pathway

OBJECTIVE

Fibroblast growth factors (FGF) axis, and in particular FGF2 axis, is an important mitogenic stimulus in endometrial carcinogenesis. hSef is a key inhibitory regulator of FGF signaling and aberrant hSef expression is reported to be present in various human carcinomas. The objective of this study was to investigate the role of hSef in the growth and proliferation of endometrial adenocarcinoma cells and to explore the mechanism that may be involved.

METHODS

Using western blot analysis, we determined the expression of hSef in Ishikawa cells under different conditions. Using luciferase reporter assays and western blot analysis, we detected the effect of hSef on MAPK/ERK-mediated FGF2 signaling. Using MTT, cell counting and colony formation assays, we analyzed the growth and proliferation of Ishikawa cells under different conditions.

RESULTS

We found that the hSef expression was positively regulated by FGF2-induced MAPK/ERK signaling and inversely, hSef expression efficiently inhibited the activity of FGF2-induced MAPK/ERK signaling, indicating the presence of hSef-mediated negative feedback mechanism for FGF signaling in endometrial cancer cells. In addition, we found that MAPK/ERK signaling was essential for the growth and proliferation of endometrial cancer cells in vitro, and hSef expression significantly reduced the cell proliferation.

CONCLUSIONS

hSef expression can inhibit the growth and proliferation of endometrial cancer cells via acting on the FGF2/MAPK/ERK signaling.

FGFR-4 Arg³⁸⁸ enhances prostate cancer progression via extracellular signal-related kinase and serum response factor signaling

PURPOSE

Increased expression of FGFR-4 and its ligands have been linked to lethal prostate cancer (PCa). Furthermore, a germ line polymorphism in the FGFR-4 gene, resulting in arginine at codon 388 (Arg³⁸⁸) instead of glycine (Gly³⁸⁸), is associated with aggressive disease. The FGFR-4 Arg³⁸⁸ variant results in increased receptor stability, sustained receptor activation, and increased motility and invasion compared with Gly³⁸⁸. However, the impact of sustained signaling on cellular signal transduction pathways is unknown.

EXPERIMENTAL DESIGN

Expression microarray analysis of immortalized prostatic epithelial cells lines expressing FGFR-4 Arg³⁸⁸ or Gly³⁸⁸ was used to establish a gene signature associated with FGFR-4 Arg³⁸⁸ expression. Transient transfection of reporters and inhibitors was used to establish the pathways activated by FGFR-4 Arg³⁸⁸ expression. The impact of pathway knockdown in vitro and in an orthotopic model was assessed using inhibitors and/or short hairpin RNA (shRNA).

RESULTS

Expression of the FGFR-4 Arg³⁸⁸ protein leads to increased activity of the extracellular signal-related kinase (ERK) pathway, increased activity of serum response factor (SRF) and AP1, and transcription of multiple genes that are correlated with aggressive clinical behavior in PCa. Increased expression of SRF is associated with biochemical recurrence in men undergoing radical prostatectomy. Consistent with these observations, knockdown of FGFR-4 Arg³⁸⁸ in PCa cells decreases proliferation and invasion in vitro and primary tumor growth and metastasis in vivo.

CONCLUSIONS

These studies define a signal transduction pathway downstream of FGFR-4 Arg³⁸⁸ that acts via ERK and SRF to promote PCa progression.

No evidence of FGFR3 mutations in prostate cancer

BACKGROUND

FGFR3 mutations are associated with a good clinical disease course in bladder tumors. Currently, prognostic markers to stratify prostate cancer (PCa) patients for conservative management are lacking. Conflicting results have been found on the presence of FGFR3 mutations in PCa. Our objective was to determine the prevalence of FGFR3 mutations in a subset of prostate tumors. Next, determine the prevalence of FGFR3 mutations in PCa patients with coexistent tumors in other tissues.

METHODS

Primary and locally advanced prostate tumors (n =132) were collected at our medical center. From the 132 PCa patients, 28 (21%) were diagnosed with coexistent primary tumors (bladder, skin, pancreas, renal cell, gastric, colon, hepatic, and lung). Tumors were analyzed by FGFR3 mutation analysis on exon 7, 10, and 15, known to harbor the most frequent mutations.

RESULTS

The prevalence of FGFR3 mutations in patients with only PCa was 0%. Most PCa patients presented with coexistent bladder (n=12) and bladder and skin tumors (n =7). Other coexistent tumors in PCa patients included: bladder and pancreatic cancer (n=1); bladder and renal cell carcinoma (n=1); bladder and gastric carcinoma (n=1); skin cancer (n=1); colon cancer (n= 3); hepatic carcinoma (n=1); and lung cancer (n = 1). FGFR3 mutations were detected in 9/15 (60%) analyzed bladder tumors.

CONCLUSIONS

FGFR3 mutations were absent in the investigated prostate tumors, suggesting a minor role of these mutations in tumorigenesis. Hence, FGFR3 mutation analysis is not suitable to select patients for conservative management. Interestingly, if a prostate tumor coincided with other tumors these were mostly bladder and skin.