Fibroblast growth factors and their receptors in hematopoiesis and hematological tumors

Exploiting the fibroblast growth factor receptor-1 vulnerability to therapeutically restrict the MYC-EZH2-CDKN1C axis-driven proliferation in Mantle cell lymphoma

Mantle cell lymphoma (MCL) is a lethal hematological malignancy with a median survival of 4 years. Its lethality is mainly attributed to a limited understanding of clinical tumor progression and resistance to current therapeutic regimes. Intrinsic, prolonged drug treatment and tumor-microenvironment (TME) facilitated factors impart pro-tumorigenic and drug-insensitivity properties to MCL cells. Hence, elucidating neoteric pharmacotherapeutic molecular targets involved in MCL progression utilizing a global "unified" analysis for improved disease prevention is an earnest need. Using integrated transcriptomic analyses in MCL patients, we identified a Fibroblast Growth Factor Receptor-1 (FGFR1), and analyses of MCL patient samples showed that high FGFR1 expression was associated with shorter overall survival in MCL patient cohorts. Functional studies using pharmacological intervention and loss of function identify a novel MYC-EZH2-CDKN1C axis-driven proliferation in MCL. Further, pharmacological targeting with erdafitinib, a selective small molecule targeting FGFRs, induced cell-cycle arrest and cell death in-vitro, inhibited tumor progression, and improved overall survival in-vivo. We performed extensive pre-clinical assessments in multiple in-vivo model systems to confirm the therapeutic potential of erdafitinib in MCL and demonstrated FGFR1 as a viable therapeutic target in MCL.

Hormone regulation of thrombospondin-1 mRNA in porcine granulosa cells in vitro

Thrombospondin-1 (THBS1) is involved in the process of angiogenesis and is down-regulated by insulin-like growth factor 1 (IGF1) in porcine granulosa cells (GC), but what other hormones regulate GC THBS1 and its role in follicular growth is unclear. Thus, six experiments were conducted to determine the influence of other hormones on THBS1 gene expression in porcine GC, and to determine if THBS1 mRNA changes during follicular development. For Exp. 1-5, small (1-5 mm) follicles from ovaries of abattoir gilts were aspirated, GC collected and treated with FSH, IGF1, fibroblast growth factor 9 (FGF9), Sonic hedgehog (SHH), estradiol, cortisol, and/or prostaglandin E2 (PGE2). FSH, IGF1 and FGF9 each decreased (P < 0.05) THBS1 mRNA abundance. Alone, PGE2 increased (P < 0.05) THBS1 mRNA abundance. PGE2 significantly attenuated the FSH-induced inhibition of THBS1 mRNA expression. Estradiol, cortisol, and SHH had no effect on THBS1 mRNA abundance. In Exp. 6, small (1-3 mm), medium (4-6 mm) and large (7-14 mm) follicles were aspirated to measure abundance of THBS1 mRNA in GC which did not differ (P > 0.10) between small and medium-sized follicles but was threefold greater (P < 0.05) in large compared to small or medium follicles. We hypothesize that the inhibitory effects of FSH, IGF1 and FGF9 on the antiangiogenic gene THBS1 could contribute to promoting angiogenesis in the developing follicle, while stimulation of THBS1 mRNA by PGE2 may help reduce angiogenesis during the preovulatory period when PGE2 and THBS1 mRNA are at their greatest levels.

Fibroblast growth factor receptor signaling in pediatric B-cell precursor acute lymphoblastic leukemia

The FGF receptor signaling pathway is recurrently involved in the leukemogenic processes. Oncogenic fusions of FGFR1 with various fusion partners were described in myeloid proliferative neoplasms, and overexpression and mutations of FGFR3 are common in multiple myeloma. In addition, fibroblast growth factors are abundant in the bone marrow, and they were shown to enhance the survival of acute myeloid leukemia cells. Here we investigate the effect of FGFR stimulation on pediatric BCP-ALL cells in vitro, and search for mutations with deep targeted next-generation sequencing of mutational hotspots in FGFR1, FGFR2, and FGFR3. In 481 primary BCP-ALL cases, 28 samples from 19 unique relapsed BCP-ALL cases, and twelve BCP-ALL cell lines we found that mutations are rare (4/481 = 0.8%, 0/28 and 0/12) and do not affect codons which are frequently mutated in other malignancies. However, recombinant ligand FGF2 reduced the response to prednisolone in several BCP-ALL cell lines in vitro. We therefore conclude that FGFR signaling can contribute to prednisolone resistance in BCP-ALL cells, but that activating mutations in this receptor tyrosine kinase family are very rare.

Hematopoietic growth factors and tumor angiogenesis

Angiogenesis is regulated by numerous "classic" factors such as vascular endothelial growth factor (VEGF) and many other endogenous "non-classic"peptides, including erythropoietin (Epo), and granulocyte-/granulocyte macrophage colony stimulating factor (G-/GM-CSF). The latter play an important regulatory role in angiogenesis, especially under pathological conditions and constitute a crosslink between angiogenesis and hematopoiesis. This article reviews studies on the ability of hematopoietic cytokines to affect several endothelial cell functions in tumor angiogenesis. These findings in all these studies support the hypothesis formulated at the beginning of this century that a common ancestral cell, the hemangioblast, gives rise to cells of both the endothelial and the hematopoietic lineages.

Effect of basic fibroblast growth factor on radiation-induced oral mucositis in male Syrian hamsters

PURPOSE

Oral mucositis is a frequent and dose-limiting side effect of radiotherapy or chemotherapy in cancer patients. We investigated the effect of basic fibroblast growth factor on radiation-induced oral mucositis in male Syrian hamsters.

METHOD

Oral mucositis was induced in male Syrian hamsters by a single dose of 30-Gy irradiation. Eight days after irradiation, treatment with gel containing trafermin (basic fibroblast growth factor) at 1 or 10 μg up to day-21 was initiated. Re-epithelialization was graded using a six-point scoring system for oral mucositis. Samples of hamster cheek pouches were removed for histopathologic analyses and immunohistochemistry.

RESULTS

The oral-mucositis score decreased in a dose-dependent manner upon trafermin treatment. Trafermin (10 μg) improved oral mucositis significantly compared with vehicle. Histopathology revealed that the degree of re-epithelialization was improved by treatment with trafermin (10 μg) compared with treatment with vehicle.

CONCLUSIONS

Administration of trafermin (10 μg) can prevent mucosal damage to hamster cheek pouches induced by irradiation.

Receptor Tyrosine Kinases: Translocation Partners in Hematopoietic Disorders

Receptor tyrosine kinases (RTKs) activate various signaling pathways and regulate cellular proliferation, survival, migration, and angiogenesis. Malignant neoplasms often circumvent or subjugate these pathways by promoting RTK overactivation through mutation or chromosomal translocation. RTK translocations create a fusion protein containing a dimerizing partner fused to an RTK kinase domain, resulting in constitutive kinase domain activation, altered RTK cellular localization, upregulation of downstream signaling, and novel pathway activation. While RTK translocations in hematological malignancies are relatively rare, clinical evidence suggests that patients with these genetic abnormalities benefit from RTK-targeted inhibitors. Here, we present a timely review of an exciting field by examining RTK chromosomal translocations in hematological cancers, such as Anaplastic Lymphoma Kinase (ALK), Fibroblast Growth Factor Receptor (FGFR), Platelet-Derived Growth Factor Receptor (PDGFR), REarranged during Transfection (RET), Colony Stimulating Factor 1 Receptor (CSF1R), and Neurotrophic Tyrosine Kinase Receptor Type 3 (NTRK3) fusions, and discuss current therapeutic options.

Molecular and clinical significance of fibroblast growth factor 2 (FGF2 /bFGF) in malignancies of solid and hematological cancers for personalized therapies

Fibroblast growth factor (FGF) signaling is essential for normal and cancer biology. Mammalian FGF family members participate in multiple signaling pathways by binding to heparan sulfate and FGF receptors (FGFR) with varying affinities. FGF2 is the prototype member of the FGF family and interacts with its receptor to mediate receptor dimerization, phosphorylation, and activation of signaling pathways, such as Ras-MAPK and PI3K pathways. Excessive mitogenic signaling through the FGF/FGFR axis may induce carcinogenic effects by promoting cancer progression and increasing the angiogenic potential, which can lead to metastatic tumor phenotypes. Dysregulated FGF/FGFR signaling is associated with aggressive cancer phenotypes, enhanced chemotherapy resistance and poor clinical outcomes. In vitro experimental settings have indicated that extracellular FGF2 affects proliferation, drug sensitivity, and apoptosis of cancer cells. Therapeutically targeting FGF2 and FGFR has been extensively assessed in multiple preclinical studies and numerous drugs and treatment options have been tested in clinical trials. Diagnostic assays are used to quantify FGF2, FGFRs, and downstream signaling molecules to better select a target patient population for higher efficacy of cancer therapies. This review focuses on the prognostic significance of FGF2 in cancer with emphasis on therapeutic intervention strategies for solid and hematological malignancies.

MiR-24 is required for hematopoietic differentiation of mouse embryonic stem cells

Overexpression of miRNA, miR-24, in mouse hematopoietic progenitors increases monocytic/ granulocytic differentiation and inhibits B cell development. To determine if endogenous miR-24 is required for hematopoiesis, we antagonized miR-24 in mouse embryonic stem cells (ESCs) and performed in vitro differentiations. Suppression of miR-24 resulted in an inability to produce blood and hematopoietic progenitors (HPCs) from ESCs. The phenotype is not a general defect in mesoderm production since we observe production of nascent mesoderm as well as mesoderm derived cardiac muscle and endothelial cells. Results from blast colony forming cell (BL-CFC) assays demonstrate that miR-24 is not required for generation of the hemangioblast, the mesoderm progenitor that gives rise to blood and endothelial cells. However, expression of the transcription factors Runx1 and Scl is greatly reduced, suggesting an impaired ability of the hemangioblast to differentiate. Lastly, we observed that known miR-24 target, Trib3, is upregulated in the miR-24 antagonized embryoid bodies (EBs). Overexpression of Trib3 alone in ESCs was able to decrease HPC production, though not as great as seen with miR-24 knockdown. These results demonstrate an essential role for miR-24 in the hematopoietic differentiation of ESCs. Although many miRNAs have been implicated in regulation of hematopoiesis, this is the first miRNA observed to be required for the specification of mammalian blood progenitors from early mesoderm.

Studies of mouse embryos and embryonic stem cells (ESCs) have defined the ontogeny of mammalian embryonic hematopoietic cells. The ESC differentiation system has been valuable for dissecting the molecular regulation of the development of mesoderm into HPCs. Extracellular signals regulate a complex network of transcription factors to direct embryonic hematopoietic development. Mammalian miRNAs have previously not been described to regulate this genetic network during embryonic hematopoiesis. However, a role for miRNAs in producing the hemangioblast, and hemogenic endothelium in Xenopus has been described. Our work with ESCs demonstrates a specific requirement for the miRNA, miR-24, in the development of hematopoietic progenitors cells (HPCs). Antagonizing miR-24 in ESCs does not affect generation of BL-CFCs, the in vitro equivalent of the hemangioblast, but does compromise the ability of those BL-CFCs to produced HPCs. Expression of transcription factors required for HPC production downstream of the hemangioblast, Scl, and Runx1, is greatly reduced by antagonizing miR-24. These results identify miR-24, as a mammalian miRNA required for the development of blood from newly formed mesoderm.

Directed differentiation of embryonic stem cells using a bead-based combinatorial screening method

We have developed a rapid, bead-based combinatorial screening method to determine optimal combinations of variables that direct stem cell differentiation to produce known or novel cell types having pre-determined characteristics. Here we describe three experiments comprising stepwise exposure of mouse or human embryonic cells to 10,000 combinations of serum-free differentiation media, through which we discovered multiple novel, efficient and robust protocols to generate a number of specific hematopoietic and neural lineages. We further demonstrate that the technology can be used to optimize existing protocols in order to substitute costly growth factors with bioactive small molecules and/or increase cell yield, and to identify in vitro conditions for the production of rare developmental intermediates such as an embryonic lymphoid progenitor cell that has not previously been reported.

Critical signal transduction pathways in CLL

Receptor tyrosine kinases (RTKs) are cell-surface transmembrane receptors that contain regulated kinase activity within their cytoplasmic domain and play a critical role in signal transduction in both normal and malignant cells. Besides B cell receptor (BCR) signaling in chronic lymphocytic leukemia (CLL), multiple RTKs have been reported to be constitutively active in CLL B cells, resulting in enhanced survival and resistance to apoptosis of the leukemic cells induced by chemotherapeutic agents. In addition to increased plasma levels of various types of cytokines/growth factors in CLL, we and others have detected that CLL B cells spontaneously produce multiple cytokines in vitro which may constitute an autocrine loop of RTK activation on the leukemic B cells. Moreover, aberrant expression and activation of non-RTKs, for example, Src/Syk kinases, induce resistance of the leukemic B cells to therapy. Based on current available knowledge, we detailed the impact of aberrant activities of various RTKs/non-RTKs on CLL B cell survival and the potential of using these signaling components as future therapeutic targets in CLL therapy.

Effects of fibroblast growth factor 9 on steroidogenesis and control of FGFR2IIIc mRNA in porcine granulosa cells

The objectives of this study were to investigate the effects of fibroblast growth factor 9 (FGF9) on hormone-stimulated porcine granulosa cell proliferation and steroid production and to further elucidate the hormonal and developmental control of FGFR2IIIc gene expression in granulosa cells. Porcine ovaries were collected from a local slaughterhouse and granulosa cells were collected from small to medium (1 to 5 mm) follicles for 5 in vitro studies that were conducted. Cells were cultured for 48 h in 5% fetal calf serum plus 5% porcine serum and then treated with various combinations of FSH, IGF-I, FGF9, Sonic hedgehog (SHH), cortisol, PGE2, and/or wingless-type mouse mammary tumor virus integration site family member 5A (WNT5A) in serum-free medium for an additional 24 or 48 h. Medium was collected for analysis of steroid concentration via RIA, or RNA was collected for gene expression analysis of FGFR2IIIc via quantitative reverse transcription PCR. Fibroblast growth factor 9 stimulated (P < 0.05) IGF-I-induced estradiol production in the presence of FSH and testosterone. However, FGF9 had inconsistent effects on progesterone production, stimulating progesterone production in the presence of FSH and testosterone but inhibiting progesterone production in the presence of IGF-I, FSH, and testosterone. Cell numbers were increased (P < 0.05) by FGF9 in the presence of IGF-I and FSH but not in the presence of FSH and absence of IGF-I. For FGFR2IIIc mRNA studies, granulosa cells were treated with FSH, IGF-I, FGF9, SHH, cortisol, PGE2, or WNT5A. Follicle-stimulating hormone alone had no effect (P > 0.10) whereas IGF-I increased (P < 0.05) FGFR2IIIc mRNA abundance. Cortisol, PGE2, SHH, and WNT5A had no effect (P > 0.10) on FGFR2IIIc gene expression whereas FGF9 in the presence of FSH and IGF-I inhibited (P < 0.05) FGFR2IIIc gene expression. In an in vivo study, granulosa cells from large (7 to 14 mm) follicles had greater (P < 0.05) abundance of FGFR2IIIc mRNA than small (1 to 3 mm) or medium (4 to 6 mm) follicles. In conclusion, IGF-I-induced FGFR2IIIc mRNA may be a mechanism for increased responses to FGF9 in FSH plus IGF-I-treated granulosa cells. Fibroblast growth factor 9 and IGF-I may work together as amplifiers of follicular growth and granulosa cell differentiation by stimulating estradiol production and concomitantly stimulating granulosa cell growth in pigs.

Clinical applications of palifermin: amelioration of oral mucositis and other potential indications

Mucositis is one of the most significant toxicities in cancer patients undergoing cytotoxic treatment. It can have a negative impact on both quality of life and health economics. Severe oral mucositis can contribute to hospitalization, need for narcotic analgesics, total parentral nutrition, suboptimal delivery of anti-neoplastic treatment, and morbidity and mortality. Palifermin, a recombinant derivative of human keratinocyte growth factor, is the first active agent approved by the FDA for the prevention of severe oral mucositis in patients undergoing haematopoietic stem cell transplantation (HSCT). Several studies have also shown significant reduction in the incidence, severity and/or duration of oral mucositis in other high-risk settings such as concurrent chemoradiotherapy (CT/RT) for patients with head and neck cancer, and use of mucotoxic chemotherapeutic agents such as doxorubicin in sarcoma and fluorouracil for the treatment of colorectal cancer. The reduction in mucositis has translated into amelioration of symptoms and improvement in daily functioning as measured by patient-reported outcome in multiple studies. The clinical response to palifermin appears to be related in part to epithelial proliferation and mucosal thickening. Palifermin also has other potential clinical applications including the acceleration of immune reconstitution and inhibition of graft-versus-host disease in patients undergoing HSCT, and mitigation of dysphagia in lung cancer patients treated with concurrent CT/RT. Palifermin is generally well tolerated with mild-to-moderate skin and oral adverse events. Future studies may expand the use of palifermin into other areas that would benefit from its cytoprotective and regenerative effects.

Fibroblast growth factor signaling promotes physiological bone remodeling and stem cell self-renewal

PURPOSE OF REVIEW

Fibroblast growth factor (FGF) signaling activates many bone marrow cell types, including various stem cells, osteoblasts, and osteoclasts. However, the role of FGF signaling in regulation of normal and leukemic stem cells is poorly understood. This review highlights the physiological roles of FGF signaling in regulating bone marrow mesenchymal and hematopoietic stem and progenitor cells (MSPCs and HSPCs) and their dynamic microenvironment. In addition, this review summarizes the recent studies which provide an overview of FGF-activated mechanisms regulating physiological stem cell maintenance, self-renewal, and motility.

RECENT FINDINGS

Current results indicate that partial deficiencies in FGF signaling lead to mild defects in hematopoiesis and bone remodeling. However, FGF signaling was shown to be crucial for stem cell self-renewal and for proper hematopoietic poststress recovery. FGF signaling activation was shown to be important also for rapid AMD3100 or post 5-fluorouracil-induced HSPC mobilization. In vivo, FGF-2 administration successfully expanded both MSPCs and HSPCs. FGF-induced expansion was characterized by enhanced HSPC cycling without further exhaustion of the stem cell pool. In addition, FGF signaling expands and remodels the supportive MSPC niche cells. Finally, FGF signaling is constitutively activated in many leukemias, suggesting that malignant HSPCs exploit this pathway for their constant expansion and for remodeling a malignant-supportive microenvironment.

SUMMARY

The summarized studies, concerning regulation of stem cells and their microenvironment, suggest that FGF signaling manipulation can serve to improve current clinical stem cell mobilization and transplantation protocols. In addition, it may help to develop therapies specifically targeting leukemic stem cells and their supportive microenvironment.

Carbon nanoparticles downregulate expression of basic fibroblast growth factor in the heart during embryogenesis

Carbon nanoparticles, with their high biocompatibility and low toxicity, have recently been considered for biomedical applications, including antiangiogenic therapy. Critical to normal development and tumor formation, angiogenesis is the process of forming capillary blood vessels from preexisting vessels. In the present study, we evaluated the effects of diamond and graphite nanoparticles on the development of chicken embryos, as well as vascularization of the chorioallantoic membrane and heart at the morphological and molecular level. Nanoparticles did not affect either body/heart weight or serum indices of the embryos’ health. However, vascularization of the heart and the density of branched vessels were significantly reduced after treatment with diamond nanoparticles and, to a lesser extent, graphite nanoparticles. Application of nanoparticles significantly downregulated gene and protein expression of the proangiogenic basic fibroblast growth factor, indicating that both diamond and graphite nanoparticles inhibit angiogenesis.

Extracellular matrix-modulated Heartless signaling in Drosophila blood progenitors regulates their differentiation via a Ras/ETS/FOG pathway and target of rapamycin function

Maintenance of hematopoietic progenitors ensures a continuous supply of blood cells during the lifespan of an organism. Thus, understanding the molecular basis for progenitor maintenance is a continued focus of investigation. A large pool of undifferentiated blood progenitors are maintained in the Drosophila hematopoietic organ, the larval lymph gland, by a complex network of signaling pathways that are mediated by niche-, progenitor-, or differentiated hemocyte-derived signals. In this study we examined the function of the Drosophila fibroblast growth factor receptor (FGFR), Heartless, a critical regulator of early lymph gland progenitor specification in the late embryo, during larval lymph gland hematopoiesis. Activation of Heartless signaling in hemocyte progenitors by its two ligands, Pyramus and Thisbe, is both required and sufficient to induce progenitor differentiation and formation of the plasmatocyte-rich lymph gland cortical zone. We identify two transcriptional regulators that function downstream of Heartless signaling in lymph gland progenitors, the ETS protein, Pointed, and the Friend-of-GATA (FOG) protein, U-shaped, which are required for this Heartless-induced differentiation response. Furthermore, cross-talk of Heartless and target of rapamycin signaling in hemocyte progenitors is required for lamellocyte differentiation downstream of Thisbe-mediated Heartless activation. Finally, we identify the Drosophila heparan sulfate proteoglycan, Trol, as a critical negative regulator of Heartless ligand signaling in the lymph gland, demonstrating that sequestration of differentiation signals by the extracellular matrix is a unique mechanism employed in blood progenitor maintenance that is of potential relevance to many other stem cell niches.

The biochemistry of hematopoietic stem cell development

BACKGROUND

The cornerstone of the adult hematopoietic system and clinical treatments for blood-related disease is the cohort of hematopoietic stem cells (HSC) that is harbored in the adult bone marrow microenvironment. Interestingly, this cohort of HSCs is generated only during a short window of developmental time. In mammalian embryos, hematopoietic progenitor and HSC generation occurs within several extra- and intraembryonic microenvironments, most notably from 'hemogenic' endothelial cells lining the major vasculature. HSCs are made through a remarkable transdifferentiation of endothelial cells to a hematopoietic fate that is long-lived and self-renewable. Recent studies are beginning to provide an understanding of the biochemical signaling pathways and transcription factors/complexes that promote their generation.

SCOPE OF REVIEW

The focus of this review is on the biochemistry behind the generation of these potent long-lived self-renewing stem cells of the blood system. Both the intrinsic (master transcription factors) and extrinsic regulators (morphogens and growth factors) that affect the generation, maintenance and expansion of HSCs in the embryo will be discussed.

MAJOR CONCLUSIONS

The generation of HSCs is a stepwise process involving many developmental signaling pathways, morphogens and cytokines. Pivotal hematopoietic transcription factors are required for their generation. Interestingly, whereas these factors are necessary for HSC generation, their expression in adult bone marrow HSCs is oftentimes not required. Thus, the biochemistry and molecular regulation of HSC development in the embryo are overlapping, but differ significantly from the regulation of HSCs in the adult.

GENERAL SIGNIFICANCE

HSC numbers for clinical use are limiting, and despite much research into the molecular basis of HSC regulation in the adult bone marrow, no panel of growth factors, interleukins and/or morphogens has been found to sufficiently increase the number of these important stem cells. An understanding of the biochemistry of HSC generation in the developing embryo provides important new knowledge on how these complex stem cells are made, sustained and expanded in the embryo to give rise to the complete adult hematopoietic system, thus stimulating novel strategies for producing increased numbers of clinically useful HSCs. This article is part of a Special Issue entitled Biochemistry of Stem Cells.

The biochemistry of hematopoietic stem cell development

BACKGROUND

The cornerstone of the adult hematopoietic system and clinical treatments for blood-related disease is the cohort of hematopoietic stem cells (HSC) that is harbored in the adult bone marrow microenvironment. Interestingly, this cohort of HSCs is generated only during a short window of developmental time. In mammalian embryos, hematopoietic progenitor and HSC generation occurs within several extra- and intraembryonic microenvironments, most notably from 'hemogenic' endothelial cells lining the major vasculature. HSCs are made through a remarkable transdifferentiation of endothelial cells to a hematopoietic fate that is long-lived and self-renewable. Recent studies are beginning to provide an understanding of the biochemical signaling pathways and transcription factors/complexes that promote their generation.

SCOPE OF REVIEW

The focus of this review is on the biochemistry behind the generation of these potent long-lived self-renewing stem cells of the blood system. Both the intrinsic (master transcription factors) and extrinsic regulators (morphogens and growth factors) that affect the generation, maintenance and expansion of HSCs in the embryo will be discussed.

MAJOR CONCLUSIONS

The generation of HSCs is a stepwise process involving many developmental signaling pathways, morphogens and cytokines. Pivotal hematopoietic transcription factors are required for their generation. Interestingly, whereas these factors are necessary for HSC generation, their expression in adult bone marrow HSCs is oftentimes not required. Thus, the biochemistry and molecular regulation of HSC development in the embryo are overlapping, but differ significantly from the regulation of HSCs in the adult.

GENERAL SIGNIFICANCE

HSC numbers for clinical use are limiting, and despite much research into the molecular basis of HSC regulation in the adult bone marrow, no panel of growth factors, interleukins and/or morphogens has been found to sufficiently increase the number of these important stem cells. An understanding of the biochemistry of HSC generation in the developing embryo provides important new knowledge on how these complex stem cells are made, sustained and expanded in the embryo to give rise to the complete adult hematopoietic system, thus stimulating novel strategies for producing increased numbers of clinically useful HSCs. This article is part of a Special Issue entitled Biochemistry of Stem Cells.

Effects of fibroblast growth factor 9 (FGF9) on steroidogenesis and gene expression and control of FGF9 mRNA in bovine granulosa cells

Gene expression of fibroblast growth factor-9 (FGF9) is decreased in granulosa cells (GC) of cystic follicles compared with normal dominant follicles in cattle. The objectives of this study were to investigate the effects of FGF9 on GC steroidogenesis, gene expression, and cell proliferation and to determine the hormonal control of GC FGF9 production. GC were collected from small (1-5 mm) and large (8-22 mm) bovine follicles and treated in vitro with various hormones in serum-free medium for 24 or 48 h. In small- and large-follicle GC, FGF9 inhibited (P < 0.05) IGF-I-, dibutyryl cAMP-, and forskolin-induced progesterone and estradiol production. In contrast, FGF9 increased (P < 0.05) GC numbers induced by IGF-I and 10% fetal calf serum. FGF9 inhibited (P < 0.05) FSHR and CYP11A1 mRNA abundance in small- and large-follicle GC but had no effect (P > 0.10) on CYP19A1 or StAR mRNA. In the presence of a 3β-hydroxysteroid dehydrogenase inhibitor, trilostane, FGF9 also decreased (P < 0.05) pregnenolone production. IGF-I inhibited (P < 0.05) whereas estradiol and FSH had no effect (P > 0.10) on FGF9 mRNA abundance. TNFα and wingless-type mouse mammary tumor virus integration site family member-3A decreased (P < 0.05) whereas T(4) and sonic hedgehog increased (P < 0.05) FGF9 mRNA abundance in control and IGF-I-treated GC. Thus, GC FGF9 gene expression is hormonally regulated, and FGF9 may act as an autocrine regulator of ovarian function by slowing follicular differentiation via inhibiting IGF-I action, gonadotropin receptors, the cAMP signaling cascade, and steroid synthesis while stimulating GC proliferation in cattle.

FGF signaling facilitates postinjury recovery of mouse hematopoietic system

Previous studies have shown that fibroblast growth factor (FGF) signaling promotes hematopoietic stem and progenitor cell (HSPC) expansion in vitro. However, it is unknown whether FGF promotes HSPC expansion in vivo. Here we examined FGF receptor 1 (FGFR1) expression and investigated its in vivo function in HSPCs. Conditional knockout (CKO) of Fgfr1 did not affect phenotypical number of HSPCs and homeostatic hematopoiesis, but led to a reduced engraftment only in the secondary transplantation. When treated with 5-fluorouracil (5FU), the Fgfr1 CKO mice showed defects in both proliferation and subsequent mobilization of HSPCs. We identified megakaryocytes (Mks) as a major resource for FGF production, and further discovered a novel mechanism by which Mks underwent FGF-FGFR signaling dependent expansion to accelerate rapid FGF production under stress. Within HSPCs, we observed an up-regulation of nuclear factor κB and CXCR4, a receptor for the chemoattractant SDF-1, in response to bone marrow damage only in control but not in Fgfr1 CKO model, accounting for the corresponding defects in proliferation and migration of HSPCs. This study provides the first in vivo evidence that FGF signaling facilitates postinjury recovery of the mouse hematopoietic system by promoting proliferation and facilitating mobilization of HSPCs.

What role for angiogenesis in childhood acute lymphoblastic leukaemia?

The role of angiogenesis in acute leukaemia has been discussed since the cloning of the gene of vascular endothelial growth factor (VEGF) from the acute myelogenous leukemia cell line (HL60) and, thereafter, when the first studies reported increased bone marrow vascularity and elevation of angiogenic cytokines in acute lymphoblastic leukaemia (ALL). VEGF and basic fibroblast growth factor (bFGF) are the major proangiogenic cytokines that have been studied, and evaluation of their prognostic impact in childhood ALL has been reported in several studies, though with controversial results. The antiangiogenic response, contributing to the angiogenic balance, has scarcely been reported. The origin of the factors, their prognostic value, and their relevance as good markers of what really happens in the bone marrow are discussed in this paper. The place of antiangiogenic drugs in ALL has to be defined in the global treatment strategy.

Keratinocyte growth factor

Mucositis occurs in over 90% of patients undergoing stem cell transplantation for hematological malignancies. It is associated with significant morbidity in the form of pain, dysphagia and decreased oral intake, as well as mortality. Palifermin is a recombinant keratinocyte growth factor that has been shown to be effective in decreasing the incidence, severity and duration of mucositis in Phase III trials. Improvement in patient functioning during hematopoietic stem cell transplants has also been reported. This review deals with the preclinical data and the clinical trials that have been carried out with this agent in patients with hematologic malignancies. In addition limited Phase I and II data on solid tumors is available and will be included.

Distinct roles of Shh and Fgf signaling in regulating cell proliferation during zebrafish pectoral fin development

Background

Cell proliferation in multicellular organisms must be coordinated with pattern formation. The major signaling pathways directing pattern formation in the vertebrate limb are well characterized, and we have therefore chosen this organ to examine the interaction between proliferation and patterning. Two important signals for limb development are members of the Hedgehog (Hh) and Fibroblast Growth Factor (Fgf) families of secreted signaling proteins. Sonic hedgehog (Shh) directs pattern formation along the anterior/posterior axis of the limb, whereas several Fgfs in combination direct pattern formation along the proximal/distal axis of the limb.

Results

We used the genetic and pharmacological amenability of the zebrafish model system to dissect the relative importance of Shh and Fgf signaling in regulating proliferation during development of the pectoral fin buds. In zebrafish mutants disrupting the shh gene, proliferation in the pectoral fin buds is initially normal, but later is strongly reduced. Correlating with this reduction, Fgf signaling is normal at early stages, but is later lost in shh mutants. Furthermore, pharmacological inhibition of Hh signaling for short periods has little effect on either Fgf signaling, or on expression of G1- and S-phase cell-cycle genes, whereas long periods of inhibition lead to the downregulation of both. In contrast, even short periods of pharmacological inhibition of Fgf signaling lead to strong disruption of proliferation in the fin buds, without affecting Shh signaling. To directly test the ability of Fgf signaling to regulate proliferation in the absence of Shh signaling, we implanted beads soaked with Fgf protein into shh mutant fin buds. We find that Fgf-soaked beads rescue proliferation in the pectoral find buds of shh mutants, indicating that Fgf signaling is sufficient to direct proliferation in zebrafish fin buds in the absence of Shh.

Conclusion

Previous studies have shown that both Shh and Fgf signaling are crucial for outgrowth of the vertebrate limb. The results presented here show that the role of Shh in this process is indirect, and is mediated by its effect on Fgf signaling. By contrast, the activity of the Fgf pathway affects proliferation directly and independently of its effect on Shh. These results show that Fgf signaling is of primary importance in directing outgrowth of the limb bud, and clarify the role of the Shh-Fgf feedback loop in regulating proliferation.

Differential requirements for hematopoietic commitment between human and rhesus embryonic stem cells

Progress toward clinical application of ESC-derived hematopoietic cellular transplantation will require rigorous evaluation in a large animal allogeneic model. However, in contrast to human ESCs (hESCs), efforts to induce conclusive hematopoietic differentiation from rhesus macaque ESCs (rESCs) have been unsuccessful. Characterizing these poorly understood functional differences will facilitate progress in this area and likely clarify the critical steps involved in the hematopoietic differentiation of ESCs. To accomplish this goal, we compared the hematopoietic differentiation of hESCs with that of rESCs in both EB culture and stroma coculture. Initially, undifferentiated rESCs and hESCs were adapted to growth on Matrigel without a change in their phenotype or karyotype. Subsequent differentiation of rESCs in OP9 stroma led to the development of CD34(+)CD45(-) cells that gave rise to endothelial cell networks in methylcellulose culture. In the same conditions, hESCs exhibited convincing hematopoietic differentiation. In cytokine-supplemented EB culture, rESCs demonstrated improved hematopoietic differentiation with higher levels of CD34(+) and detectable levels of CD45(+) cells. However, these levels remained dramatically lower than those for hESCs in identical culture conditions. Subsequent plating of cytokine-supplemented rhesus EBs in methylcellulose culture led to the formation of mixed colonies of erythroid, myeloid, and endothelial cells, confirming the existence of bipotential hematoendothelial progenitors in the cytokine-supplemented EB cultures. Evaluation of four different rESC lines confirmed the validity of these disparities. Although rESCs have the potential for hematopoietic differentiation, they exhibit a pause at the hemangioblast stage of hematopoietic development in culture conditions developed for hESCs.

Negative regulation of primitive hematopoiesis by the FGF signaling pathway

Hematopoiesis is controlled by multiple signaling molecules during embryonic and postnatal development. The function of the fibroblast growth factor (FGF) pathway in this process is unclear. Here we show that FGF plays a key role in the regulation of primitive hematopoiesis in chicks. Using hemoglobin mRNA expression as a sensitive marker, we demonstrate that timing of blood differentiation can be separated from that of initial mesoderm patterning and subsequent migration. High FGF activity inhibits primitive blood differentiation and promotes endothelial cell fate. Conversely, inhibition of FGFR activity leads to ectopic blood formation and down-regulation of endothelial markers. Expression and functional analyses indicate that FGFR2 is the key receptor mediating these effects. The FGF pathway regulates primitive hematopoiesis by modulating Gata1 expression level and activity. We propose that the FGF pathway mediates repression of globin gene expression and that its removal is essential before terminal differentiation can occur.

Activation of FGFR1beta signaling pathway promotes survival, migration and resistance to chemotherapy in acute myeloid leukemia cells

Fibroblast growth factors (FGFs) are important regulators of hematopoiesis and have been implicated in the tumorigenesis of solid tumors. Recent evidence suggests that FGF signaling through FGF receptors (FGFRs) may play a role in the proliferation of subsets of acute myeloid leukemias (AMLs). However, the precise mechanism and specific FGF receptors that support leukemic cell growth are not known. We show that FGF-2, through activation of FGFR1beta signaling, promotes survival, proliferation and migration of AML cells. Stimulation of FGFR1beta results in phosphoinositide 3-kinase (PI3-K)/Akt activation and inhibits chemotherapy-induced apoptosis of leukemic cells. Neutralizing FGFR1-specific antibody abrogates the physiologic and chemoprotective effects of FGF-2/FGFR1beta signaling and inhibits tumor growth in mice xenotransplanted with human AML. These data suggest that activation of FGF-2/FGFR1beta supports progression and chemoresistance in subsets of AML. Therefore, FGFR1 targeting may be of therapeutic benefit in subsets of AML.

Palifermin (recombinant keratinocyte growth factor-1): a pleiotropic growth factor with multiple biological activities in preventing chemotherapy- and radiotherapy-induced mucositis

Oral and intestinal mucositis are among the most significant dose-limiting toxic effects of intensive cancer treatment and are associated with adverse clinical and economic outcomes. Palifermin (Kepivancetrade mark), an N-truncated recombinant human keratinocyte growth factor-1, is the first agent to be approved for prevention of oral mucositis. Keratinocyte growth factor, a potent epithelial mitogen, appears to play a major role in the healing process. Palifermin has multiple biological activities that appear to protect the mucosal epithelium and promote its early regeneration after irradiation- and chemotherapy-induced injury. These include inhibition of epithelial cell apoptosis and DNA damage, up-regulation of detoxifying enzymes and down-regulation of pro-inflammatory cytokines, as well as enhanced migration, proliferation and differentiation of epithelial cells. Palifermin reduces the incidence, severity and duration of oral mucositis in patients with haematological malignancies undergoing myelotoxic conditioning therapy and haematopoietic stem-cell transplantation. Clinical sequelae, including febrile neutropenia and resource use (opioid analgesia and parenteral feeding), are concomitantly reduced. Other potential applications being explored include use in the solid tumour setting, reduction of intestinal mucositis and reduction of GVHD in allogenic transplantation. Thus, the development of palifermin and other potential new agents for preventing chemotherapy- and radiotherapy-induced mucositis represents an important breakthrough in oncological supportive care.

Keratinocyte growth factor expression and activity in cancer: implications for use in patients with solid tumors

Keratinocyte growth factor (KGF) is a locally acting epithelial mitogen that is produced by cells of mesenchymal origin and has an important role in protecting and repairing epithelial tissues. Use of recombinant human KGF (palifermin) in patients with hematologic malignancies reduces the incidence and duration of severe oral mucositis experienced after intensive chemoradiotherapy. These results suggest that KGF may be useful in the treatment of patients with other kinds of tumors, including those of epithelial origin. However, its application in this context raises issues that were not pertinent to its use in hematologic cancer because epithelial tumor cells, unlike blood cells, often express the KGF receptor (FGFR2b). Thus, it is important to examine whether KGF could promote the growth of epithelial tumors or protect such tumor cells from the effects of chemotherapy agents. Analyses of KGF and FGFR2b expression in tumor specimens and of KGF activity on transformed cells in vitro and in vivo do not indicate a definitive role for KGF in tumorigenesis. On the contrary, restoring FGFR2b expression to certain malignant cells can induce cell differentiation or apoptosis. However, other observations suggest that, in specific situations, KGF may contribute to epithelial tumorigenesis. Thus, further studies are warranted to examine the nature and extent of KGF involvement in these settings. In addition, clinical trials in patients with solid tumors are underway to assess the potential benefits of using KGF to protect normal tissue from the adverse effects of chemoradiotherapy and its possible impact on clinical outcome.

Fgf21 is essential for haematopoiesis in zebrafish

Fibroblast growth factors (Fgfs) function as key secreted signalling molecules in many developmental events. The zebrafish is a powerful model system for the investigation of embryonic vertebrate haematopoiesis. Although the effects of Fgf signalling on haematopoiesis in vitro have been reported, the functions of Fgf signalling in haematopoiesis in vivo remain to be explained. We identified Fgf21 in zebrafish embryos. Fgf21-knockdown zebrafish embryos lacked erythroid and myeloid cells but not blood vessels and lymphoid cells. The knockdown embryos had haemangioblasts and haematopoietic stem cells. However, the knockdown embryos had significantly fewer myeloid and erythroid progenitor cells. In contrast, Fgf21 had no significant effect on cell proliferation and apoptosis in the intermediate cell mass. These results indicate that Fgf21 is a newly identified factor essential for the determination of myelo-erythroid progenitor cell fate in vivo.

Canine retinal angioblasts are multipotent

The purpose of this study was to culture and characterize endothelial cells and angioblasts, vascular precursors, from adult and neonatal dog retina and determine if angioblasts are committed to endothelial cell lineage or have the potential to be multipotent, i.e. express phenotypic characteristics of other vascular cell types. Endothelial cells were established from adult dog retina (ADREC) by the technique of Gitlin and D'Amore. For angioblasts, pieces of neonatal day 2 (P2) avascular peripheral retina were placed under coverslips until sufficient cells had explanted. All cells were maintained initially on hyaluronic acid (HA)/fibronectin (FN) substratum. Neonatal canine retinal angioblasts (NCRA) were maintained initially on retinal-derived growth factor with alpha-amino adipic acid to inhibit growth of Muller cells. Cell lines were characterized by enzyme histochemistry [menadione-dependent alpha glycerophosphate dehydrogenase (alphaGPDH), marker for angioblasts] and immunocytochemistry. Once characterized, cells were grown on FN, or collagens I or IV substrata and fed platelet-derived growth factor-BB (PDGF-BB) or fibroblast growth factor-2 (FGF-2). The phenotypic expression of a marker for endothelial cells [acetylated LDL (acLDL) uptake] or a marker for pericytes and smooth muscle cells, production of alpha smooth muscle actin (alphaSMA), was evaluated under those conditions. The canine retinal cell lines that were established had the following characteristics when maintained on serum and a retinal extract. Angioblasts had low expression of vWf and VEGF-R2 (two markers for canine endothelial cells), and very low uptake of acLDL but high expression of alphaGPDH and adenosine A2a receptors (A2aR) (two markers for canine angioblasts in vivo). ADREC had high expression of endothelial cell markers (vWf, VEGF-R2, and acLDL uptake) but minimal expression of alphaGPDH and A2aR. Both angioblasts and endothelial cells expressed CXCR4, a marker for hemangioblasts. Angioblasts grown on any of the substrata in the presence of FGF-2 had high uptake of acLDL and low expression of alphaSMA, while those grown in the presence of PDGF-BB had high expression of alphaSMA and low uptake of acLDL. In conclusion, angioblasts cultured from peripheral vascular retina have low expression of endothelial cell markers and high alphaGPDH and A2aR, markers for canine angioblasts in vivo. Angioblasts will internalize acLDL when maintained on FGF-2 and express alphaSMA when maintained on PDGF-BB, suggesting that they have the potential to become endothelial cells or pericytes, i.e. are multipotent.

The expression of fibroblast growth factors and their receptors in Hodgkin's lymphoma

The expression of fibroblast growth factors (FGF1 and FGF2) and their receptors has been reported in a variety of human neoplasms, including haematological neoplasia. Fibroblast growth factors can promote tumour growth directly, or indirectly through promoting the growth of vessels. In the present study, we evaluated the expression of FGF1 and FGF2 as well as FGF receptors 1-4 (FGFR1-FGFR4) in 39 cases of Hodgkin's lymphoma, including all subtypes, as well as Hodgkin's lymphoma cell lines. FGF1 and FGF2 and their receptors FGFR2-FGFR4, but not FGFR1, were found to be expressed by the malignant cells in the majority of cases. Interestingly, only FGFR3, but none of the FGFs or the other FGFRs, was expressed by the Hodgkin's lymphoma cell lines. This indicates that only FGFR3 is constitutively expressed by Hodgkin's lymphoma cells, whereas FGFs and the other FGFRs are induced in vivo. Culture of the Hodgkin's cell lines under conditions of hypoxic stress could induce vascular endothelial growth factor (VEGF) but not FGF expression. FGFs, in contrast to VEGF, might be expressed in response to paracrine stimuli. In situ hybridization did not reveal FGFR3 gene amplification or translocation as the cause of constitutive FGFR3 expression, as has been shown in a subset of multiple myeloma. FGFR3 might be expressed as part of the Hodgkin's cell phenotype. The demonstration of widespread expression of FGFs and some of their receptors in Hodgkin's lymphoma suggests that FGFs are important for sustaining growth of the lymphoma and suggests that anti-FGF antibodies could be used as an adjuvant treatment.

Gene expression profiling and analysis of signaling pathways involved in priming and differentiation of human neural stem cells

Human neural stem cells have the ability to differentiate into all three major cell types in the CNS including neurons, astrocytes and oligodendrocytes. The multipotency of human neural stem cells shed a light on the possibility of using stem cells as a therapeutic tool for various neurological disorders including neurodegenerative diseases and neurotrauma that involve a loss of functional neurons. We have discovered previously a priming procedure to direct primarily cultured human neural stem cells to differentiate into almost pure neurons when grafted into adult CNS. However, the molecular mechanism underlying this phenomenon is still unknown. To unravel transcriptional changes of human neural stem cells upon priming, cDNA microarray was used to study temporal changes in human neural stem cell gene expression profile during priming and differentiation. As a result, transcriptional levels of 520 annotated genes were detected changed in at least at two time points during the priming process. In addition, transcription levels of more than 3000 hypothetical protein encoding genes and EST genes were modulated during the priming and differentiation processes of human neural stem cells. We further analyzed the named genes and grouped them into 14 functional categories. Of particular interest, key cell signal transduction pathways, including the G-protein-mediated signaling pathways (heterotrimeric and small monomeric GTPase pathways), the Wnt signaling pathway and the TGF-beta pathway, are modulated by the neural stem cell priming, suggesting important roles of these key signaling pathways in priming and differentiation of human neural stem cells.

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

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

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

PURPOSE

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

EXPERIMENTAL DESIGN

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

RESULTS

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

CONCLUSIONS

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

Altered hematopoiesis in glypican-3-deficient mice results in decreased osteoclast differentiation and a delay in endochondral ossification

Loss of function mutations in the gene encoding the heparan sulfate proteoglycan Glypican-3 (GPC3) causes an X-linked disorder in humans known as Simpson-Golabi-Behmel Syndrome (SGBS). This disorder includes both pre- and postnatal overgrowth, a predisposition to certain childhood cancers, and a complex assortment of congenital defects including skeletal abnormalities. In this study, we have identified a previously unrecognized delay in endochondral ossification associated with the loss of Gpc3 function. Gpc3 knockout animals show a marked reduction in calcified trabecular bone, and an abnormal persistence of hypertrophic chondrocytes at embryonic day 16.5 (E16.5). These hypertrophic chondrocytes down-regulate Type X collagen mRNA expression and undergo apoptosis, suggesting a normal progression of hypertrophic chondrocyte cell fate. However, replacement of these cells by mineralized bone is delayed in association with a marked delay in the appearance of osteoclasts in the bone in vivo. This delay in vivo correlates with a significant reduction in the capacity to form osteoclasts from bone marrow macrophage precursors in vitro in response to M-CSF and RANKL, and with a reduction in the numbers of bone-marrow-derived cells expressing the markers CD11b and Gr-1. Together, these results indicate selective impairment in the development of the common hematopoietic lineage from which monocyte/macrophages and PMNs are derived. This is the first report of a requirement for heparan sulfate, and specifically Gpc3, in the lineage-specific differentiation of these cell types in vivo.

Structural basis for fibroblast growth factor receptor activation

FGF signaling plays a ubiquitous role in human biology as a regulator of embryonic development, homeostasis and regenerative processes. In addition, aberrant FGF signaling leads to diverse human pathologies including skeletal, olfactory, and metabolic disorders as well as cancer. FGFs execute their pleiotropic biological actions by binding, dimerizing and activating cell surface FGF receptors (FGFRs). Proper regulation of FGF-FGFR binding specificity is essential for the regulation of FGF signaling and is achieved through primary sequence variations among the 18 FGFs and seven FGFRs. The severity of human skeletal syndromes arising from mutations that violate FGF-FGFR specificity is a testament to the importance of maintaining precision in FGF-FGFR specificity. The discovery that heparin/heparan sulfate (HS) proteoglycans are required for FGF signaling led to numerous models for FGFR dimerization and heralded one of the most controversial issues in FGF signaling. Recent crystallographic analyses have led to two fundamentally different models for FGFR dimerization. These models differ in both the stoichiometry and minimal length of heparin required for dimerization, the quaternary arrangement of FGF, FGFR and heparin in the dimer, and in the mechanism of 1:1 FGF-FGFR recognition and specificity. In this review, we provide an overview of recent structural and biochemical studies used to differentiate between the two crystallographic models. Interestingly, the structural and biophysical analyses of naturally occurring pathogenic FGFR mutations have provided the most compelling and unbiased evidences for the correct mechanisms for FGF-FGFR dimerization and binding specificity. The structural analyses of different FGF-FGFR complexes have also shed light on the intricate mechanisms determining FGF-FGFR binding specificity and promiscuity and also provide a plausible explanation for the molecular basis of a large number craniosynostosis mutations.

Embryonic reversions and lineage infidelities in tumour cells: genome-based models and role of genetic instability

Reversions to "embryonic precursor"-type cells and infidelities of tumour cell lineage (including metaplasias) have been recognized as aspects of various tumour types since the 19th century. Since then, evidence of these phenomena has been obtained from numerous clinical, biochemical, immunological and molecular biological studies. In particular, microarray studies have suggested that "aberrant" expressions of relevant genes are common. An unexplained aspect of the results of these studies is that, in many tumour types, the embryonic reversion or lineage infidelity only occurs in a proportion of cases. As a parallel development during the molecular biological investigation of tumours over the last several decades, genetic instability has been found much more marked, at least in some preparations of tumour cells, than that identified by means of previous karyotypic investigations of tumours. This study reviews examples of embryonic reversion and lineage infidelity phenomena, which have derived from the various lines of investigation of cancer over the last 150 or so years. Four categories of circumstances of the occurrence of embryonic reversions or lineage infidelities have been identified - (i) as part of the defining phenotype of the tumour, and hence being presumably integral to the tumour type, (ii) present ab initio in only some cases of the tumour type, and presumably being regularly associated with, but incidental to, the essential features of the tumour type, (iii) occurring later in the course of the disease and thus being possibly a manifestation of in vivo genetic instability and "tumour progression" and (iv) arising probably by genetic instability, during the processes, especially cell culture, associated with ex vivo investigations. Genomic models are described which might account for the origin of these phenomena in each of these circumstances.

Fibroblast growth factor signaling during early vertebrate development

Fibroblast growth factors (FGFs) have been implicated in diverse cellular processes including apoptosis, cell survival, chemotaxis, cell adhesion, migration, differentiation, and proliferation. This review presents our current understanding on the roles of FGF signaling, the pathways employed, and its regulation. We focus on FGF signaling during early embryonic processes in vertebrates, such as induction and patterning of the three germ layers as well as its function in the control of morphogenetic movements.

Coexpression and regulation of the FGF-2 and FGF antisense genes in leukemic cells

Fibroblast growth factor-2 (FGF-2) is a growth and survival factor whose expression is elevated in many hematopoietic malignancies. A natural antisense RNA (FGF-AS) has been implicated in the posttranscriptional regulation of FGF-2 mRNA expression. We demonstrate for the first time that FGF sense and antisense RNAs are coordinately expressed and translated in hematopoietic cells and tissues. Cytokine stimulation of growth-arrested K562 cells elicited a rapid transient increase in FGF-AS mRNA expression followed by a slower but sustained increase in FGF-2 mRNA. This was accompanied by a marked increase in the expression and nuclear translocation of FGF-2 and the FGF-AS encoded protein, GFG/NUDT6. These findings suggest a role for both FGF-2 and GFG proteins in the cell survival and proliferation of lymphoid and myeloid tumor cells.

Palifermin for oral mucositis after intensive therapy for hematologic cancers

BACKGROUND

Oral mucositis is a complication of intensive chemotherapy and radiotherapy with no effective treatment. We tested the ability of palifermin (recombinant human keratinocyte growth factor) to decrease oral mucosal injury induced by cytotoxic therapy.

METHODS

This double-blind study compared the effect of palifermin with that of a placebo on the development of oral mucositis in 212 patients with hematologic cancers; 106 patients received palifermin (60 microg per kilogram of body weight per day) and 106 received a placebo intravenously for three consecutive days immediately before the initiation of conditioning therapy (fractionated total-body irradiation plus high-dose chemotherapy) and after autologous hematopoietic stem-cell transplantation. Oral mucositis was evaluated daily for 28 days after transplantation.

RESULTS

The incidence of oral mucositis of World Health Organization (WHO) grade 3 or 4 was 63 percent in the palifermin group and 98 percent in the placebo group (P<0.001). Among patients with this degree of mucositis, the median duration of mucositis was 6 days (range, 1 to 22) in the palifermin group and 9 days (range, 1 to 27) in the placebo group. Among all patients, regardless of the occurrence of mucositis, the median duration of oral mucositis of WHO grade 3 or 4 was 3 days (range, 0 to 22) in the palifermin group and 9 days (range, 0 to 27) in the placebo group (P<0.001). As compared with placebo, palifermin was associated with significant reductions in the incidence of grade 4 oral mucositis (20 percent vs. 62 percent, P<0.001), patient-reported soreness of the mouth and throat (area-under-the-curve score, 29.0 [range, 0 to 98] vs. 46.8 [range, 0 to 110]; P<0.001), the use of opioid analgesics (median, 212 mg of morphine equivalents [range, 0 to 9418] vs. 535 mg of morphine equivalents [range, 0 to 9418], P<0.001), and the incidence of use of total parenteral nutrition (31 percent vs. 55 percent, P<0.001). Adverse events, mainly rash, pruritus, erythema, mouth and tongue disorders, and taste alteration, were mild to moderate in severity and were transient.

CONCLUSIONS

Palifermin reduced the duration and severity of oral mucositis after intensive chemotherapy and radiotherapy for hematologic cancers.

Imatinib Therapy in Clonal Eosinophilic Disorders, Including Systemic Mastocytosis

Primary (nonreactive) eosinophilia is operationally classified as either a "clonal" or an "idiopathic" process. Clonal eosinophilia stipulates the presence of cytogenetic, molecular, or bone marrow histologic evidence of acute leukemia or a chronic myeloid disorder. Idiopathic eosinophilia is a diagnosis of exclusion that is made after ruling out both "secondary" (reactive) and clonal eosinophilia. Hypereosinophilic syndrome is a subclass of idiopathic eosinophilia that requires the documentation of both sustained eosinophilia (> or = 1500/microL for at least 6 months) and target-organ damage. A series of novel observations in the last 5 years have warranted a refined approach to the diagnosis as well as the treatment of clonal eosinophilic disorders, including systemic mastocytosis. At the center of these new developments are mutations involving the platelet-derived growth factor receptor genes (PDGFRA and PDGFRB), which have been pathogenetically linked to clonal eosinophilia, and their presence predicts complete as well as durable treatment responses to imatinib mesylate. The bone marrow histologic phenotype of these imatinib-sensitive eosinophilic disorders includes systemic mastocytosis, chronic eosinophilic leukemia, chronic myelomonocytic leukemia, and atypical chronic myeloproliferative disorder.

Plasma angiopoietin-1, angiopoietin-2 and Tie-2 in breast and prostate cancer: a comparison with VEGF and Flt-1

BACKGROUND

Angiogenesis is essential for tumour growth and metastasis, and is coordinated by several classes of growth factors mediating their effect through receptors linked, in turn, to tyrosine kinase. These growth factors include angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2) and vascular endothelial growth factor (VEGF), which act through receptors Flt-1 and Tie-2.

MATERIALS AND METHODS

In order to further determine abnormalities in levels of Ang-1, Ang-2, Tie-2, sFlt-1 and VEGF in human cancer (and their interrelationships), these molecules were measured in plasma from 30 patients with breast cancer, 30 patients with prostate cancer and 12 healthy controls per cancer group.

RESULTS

In breast cancer, levels of Ang-1 (P=0.0005), Ang-2 (P=0.0173), Tie-2 (P=0.0001), and VEGF (P=0.0001) were all significantly raised, and plasma levels of sFlt-1 (P=0.045) were significantly reduced compared with controls. However, in prostate cancer, only levels of VEGF and Tie-2 were significantly higher (both P=0.001). There were no significant differences between levels of any molecule between the two groups of cancer. The only difference between the healthy control groups was lower Ang-1 in the women compared with men. Significant correlations were found between levels of Ang-1 and Tie-2 both in breast (r=0.498, P=0.005) and prostate cancer (r=0.643, P=<0.001). Angiopoietin-1 was also positively correlated with Ang-2 in both breast (r=0.422, P=0.02) and prostate cancer (r=0.543, P=0.002).

CONCLUSIONS

Abnormal levels of Ang-1, Ang-2 and their receptor, Tie-2, are present in breast and prostate cancer, and their interrelationships may be important in the pathophysiology of these conditions.

Erythropoietin as an angiogenic factor

Erythropoietin (Epo) is produced by the fetal liver and adult kidney and is an essential stimulator of erythropoiesis. It has, however, been shown to modulate host cellular signal transduction pathway to perform many other functions. New sites of Epo production have been found, such as the female reproductive organs and central nervous system. This review summarizes the involvement of Epo in the regulation of angiogenesis in both normal and pathological conditions.