Id1 and Id3 are required for neurogenesis, angiogenesis and vascularization of tumour xenografts

Roles of old players in the suppression of a new player: networks for the transcriptional control of angiogenesis

During the formation of blood vessels, Id1, a member of the helix-loop-helix (HLH) family, and TAL1/SCL, a basic HLH (bHLH) transcription factor, play important roles in the activation of endothelial cells. Recent reports revealed that E2-2, another bHLH transcription factor, inhibits angiogenesis in vitro and in vivo by suppressing the expression of vascular endothelial growth factor receptor 2 (VEGFR2). Id1 and TAL1/SCL dimerize with E2-2 and relieve the E2-2-mediated down-regulation of VEGFR2 expression, leading to the activation of endothelial cells. These findings reveal a novel interplay between HLH transcription factors that regulate angiogenesis.

Essential regulation of CNS angiogenesis by the orphan G protein-coupled receptor GPR124

The orphan G protein-coupled receptor (GPCR) GPR124/tumor endothelial marker 5 is highly expressed in central nervous system (CNS) endothelium. Here, we show that complete null or endothelial-specific GPR124 deletion resulted in embryonic lethality from CNS-specific angiogenesis arrest in forebrain and neural tube. Conversely, GPR124 overexpression throughout all adult vascular beds produced CNS-specific hyperproliferative vascular malformations. In vivo, GPR124 functioned cell-autonomously in endothelium to regulate sprouting, migration, and developmental expression of the blood-brain barrier marker Glut1, whereas in vitro, GPR124 mediated Cdc42-dependent directional migration to forebrain-derived, vascular endothelial growth factor-independent cues. Our results demonstrate CNS-specific angiogenesis regulation by an endothelial receptor and illuminate functions of the poorly understood adhesion GPCR subfamily. Further, the functional tropism of GPR124 marks this receptor as a therapeutic target for CNS-related vascular pathologies.

Variability in training-induced skeletal muscle adaptation

When human skeletal muscle is exposed to exercise training, the outcomes, in terms of physiological adaptation, are unpredictable. The significance of this fact has long been underappreciated, and only recently has progress been made in identifying some of the molecular bases for the heterogeneous response to exercise training. It is not only of great medical importance that some individuals do not substantially physiologically adapt to exercise training, but the study of the heterogeneity itself provides a powerful opportunity to dissect out the genetic and environmental factors that limit adaptation, directly in humans. In the following review I will discuss new developments linking genetic and transcript abundance variability to an individual's potential to improve their aerobic capacity or endurance performance or induce muscle hypertrophy. I will also comment on the idea that certain gene networks may be associated with muscle “adaptability” regardless the stimulus provided.

The role of inhibitor of DNA-binding (Id1) in hyperproliferation of keratinocytes: the pathological basis for middle ear cholesteatoma from chronic otitis media

OBJECTIVES

A hallmark of cholesteatoma is hyperproliferation of keratinocytes with abundant production of keratins in the middle ear under chronic inflammatory conditions. However, little is known about the driving force of cellular proliferation and keratin production of cholesteatomal matrix. The purpose of this study was to investigate the cellular proliferation and keratin production of keratinocytes under the influence of Id1, a candidate transcription factor to cell proliferation.

MATERIALS AND METHODS

Keratinocytes were transfected with Id1 and the responses of keratinocytes to Id1 were studied by using cellular and molecular biologic methods.

RESULTS

Id1 positively contributed to the cell cycle progression and negatively to the p16(Ink4a) downregulation via the nuclear factor-kappa B (NF-κB)/cyclin D1 pathway. Id1 significantly increased the promoter activity of NF-κB which, in turn, up-regulated the expression of cyclin D1 and keratin 10 in keratinocytes. Specific NF-κB inhibitors (pyrrolidine dithiocarbamate, PDTC), or dominant-negative inhibitor (I kappa B alpha mutant, IκBαM) abrogated the Id1-induced cell proliferation and keratin 10 production whereas p65, a subunit of the NF-κB heterodimer and an enhancer of the NF-κB activity, strengthened the Id1-induced cell proliferation and keratin 10 production.

CONCLUSIONS

Id1 contributed to hyperproliferation of keratinocytes via enhancement of cell cycle progression, removal of cell cycle inhibition, and simultaneously increased keratin production.

Developmental ablation of Id1 and Id3 genes in the vasculature leads to postnatal cardiac phenotypes

The Id1 and Id3 genes play major roles during cardiac development, despite their expression being confined to non-myocardial layers (endocardium-endothelium-epicardium). We previously described that Id1Id3 double knockout (dKO) mouse embryos die at mid-gestation from multiple cardiac defects, but early lethality precluded the studies of the roles of Id in the postnatal heart. To elucidate postnatal roles of Id genes, we ablated the Id3 gene and conditionally ablated the Id1 gene in the endothelium to generate conditional KO (cKO) embryos. We observed cardiac phenotypes at birth and at 6 months of age. Half of the Id cKO mice died at birth. Postnatal demise was associated with cardiac enlargement and defects in the ventricular septum, trabeculation and vasculature. Surviving Id cKO mice exhibited fibrotic vasculature, cardiac enlargement and decreased cardiac function. An abnormal vascular response was also observed in the healing of excisional skin wounds of Id cKO mice. Expression patterns of vascular, fibrotic and hypertrophic markers were altered in the Id cKO hearts, but addition of Insulin-Like Growth Factor binding protein-3 (IGFbp3) reversed gene expression profiles of vascular and fibrotic, but not hypertrophic markers. Thus, ablation of Id genes in the vasculature leads to distinct postnatal cardiac phenotypes. These findings provide important insights into the role/s of the endocardial network of the endothelial lineage in the development of cardiac disease, and highlight IGFbp3 as a potential link between Id and its vascular effectors.

Id2a influences neuron and glia formation in the zebrafish retina by modulating retinoblast cell cycle kinetics

Inhibitor of differentiation (Id) family helix-loop-helix proteins regulate the proliferation, survival and differentiation of numerous cell types during development; however, their functions during retinal development have not been analyzed. Using loss-of-function and overexpression assays in zebrafish, we demonstrate that Id2a levels modulate retinoblast cell cycle kinetics and thereby influence neuron and glia formation in the retina. Id2a-deficient retinas possess increased numbers of cells occupying S phase, at the expense of mitotic cells, and kinetic analyses demonstrate that Id2a is required for S-phase progression and/or the transition from S to M phase. Id2a-dependent defects in retinoblast proliferation lead to microphthalmia and to an absence of nearly all differentiated inner and outer nuclear layer cell types. Overexpression of id2a has the opposite effect on retinoblast cell cycle kinetics: id2a-overexpressing retinoblasts progress from S to M phase more rapidly and they undergo mitosis more frequently, which results in macrophthalmia. Mosaic analyses reveal that Id2a function in facilitating both cell cycle progression and neuronal differentiation in the retina is non-cell-autonomous, suggesting that Id2a functions upstream of the extrinsic pathways that regulate retinogenesis.

ID family protein expression and regulation in hypoxic pulmonary hypertension

Bone morphogenetic protein (BMP) signaling has been linked to the development of pulmonary hypertension (PH). Inhibitors of differentiation (ID) proteins (ID1-4) are a family of basic helix-loop-helix transcription factors that are downstream targets of the BMP signaling pathway, but the role that ID proteins play in the development of PH is unknown. To address this, we evaluated pulmonary expression of ID proteins in a mouse model of hypoxia-induced PH. There is selective induction of ID1 and ID3 expression in hypoxic pulmonary vascular smooth muscle cells (VSMCs) in vivo, and ID1 and ID3 expression are increased by hypoxia in cultured pulmonary VSMCs in a BMP-dependent fashion. ID4 protein is barely detectable in the mouse lung, and while ID2 is induced in hypoxic peripheral VSMCs in vivo, it is not increased by hypoxia or BMP signaling in cultured pulmonary VSMCs. In addition, the PH response to chronic hypoxia is indistinguishable between wild type and Id1 null mice. This is associated with a compensatory increase in ID3 but not ID2 expression in pulmonary VSMCs of Id1 null mice. These findings indicate that ID1 is dispensable for mounting a normal pulmonary vascular response to hypoxia, but suggest that ID3 may compensate for loss of ID1 expression in pulmonary VSMCs. Taken together, these findings indicate that ID1 and ID3 expression are regulated in a BMP-dependent fashion in hypoxic pulmonary VSMCs, and that ID1 and ID3 may play a cooperative role in regulating BMP-dependent VSMC responses to chronic hypoxia.

Id proteins facilitate self-renewal and proliferation of neural stem cells

Members of helix-loop-helix (HLH) protein family of Id (inhibitor of differentiation) dimerize with bHLH transcription factors and function as negative regulators of differentiation during development. Most of inhibitory roles of Id proteins have been demonstrated in non-neural tissues, and their roles in the developing nervous system are not clearly demonstrated. In this study, we show that Id1, Id2, and Id3 increase self-renewing and proliferation potential of cortical neural stem cells (NSCs) while inhibiting neuronal differentiation. In electrophoretic mobility gel shift and luciferase assays, Id proteins interfered with binding of NeuroD/E47 complexes to the E-box sequences and inhibited E-box-mediated gene expression. Overexpression of Id proteins in NSCs increased both the number and the size of neurospheres in colony-forming assays. Expression of Hes1 and Hes5 was not increased by overexpression of Id proteins under the condition in which Nestin expression was increased. In utero electroporation of Id yielded higher numbers of Ki67-positive and Sox2-positive cells in the mouse embryonic brain. The study suggests Id proteins play independent roles in the maintenance of neural stem properties.

Inhibition of Id proteins by a peptide aptamer induces cell-cycle arrest and apoptosis in ovarian cancer cells

Background:

Inhibitors of DNA-binding proteins (Id1-4), lacking the basic DNA-binding domain, function as dominant inhibitors of cell-cycle regulators. Overexpression of Id proteins promotes cancer cell proliferation and resistance against apoptosis. Level of Id protein expression, especially of Id1, correlates with poor differentiation, enhanced malignant potential and more aggressive clinical behaviour of ovarian tumours. Although overexpression of Ids has been found and shown to correlate with poor clinical outcome, their inhibition at protein level has never been studied.

Methods:

A peptide aptamer, Id1/3-PA7, targeting Id1 and Id3, was isolated from a randomised combinatorial expression library using yeast and mammalian two-hybrid systems. Id1/3-PA7 was fused, expressed and purified with a cell-penetrating protein transduction domain.

Results:

Intracellular-delivered Id1/3-PA7 colocalised to Id1 and Id3. It induced cell-cycle arrest and apoptosis in ovarian cancer cells ES-2 and PA-1. It activated the E-box promoter and increased the expression level of cyclin-dependent kinase inhibitor (CDKN2A) in a dose-dependent manner that is paralleled by the cleavage of poly-ADP ribose polymerase. These effects were counteracted by ectopically overexpressed Id1 and Id3.

Conclusion:

Id1/3-PA7 could represent an exogenous anti-tumour agent that can significantly trigger cell-cycle arrest and apoptosis in ovarian cancer.

CCN1 promotes the differentiation of endothelial progenitor cells and reendothelialization in the early phase after vascular injury

Endothelial progenitor cells (EPCs) contribute to the process of reendothelialization and prevent neointimal formation after vascular injury. The present study was designed to investigate whether the cysteine-rich 61 (CYR61, CCN1), an important matricellular component of local vascular microenvironment, has effect on EPCs differentiation and reendothelialization in response to vascular injury in rat. Following balloon injury, CCN1 was rapidly induced and dynamically changed at vascular lesions. Overexpression of CCN1 by adenovirus (Ad-CCN1) accelerated reendothelialization and inhibited neointimal formation in the early phase (day 14) after vascular injury (p < 0.05), while no effect was shown on day 21. Ad-CCN1 treatment increased the adhering EPCs on the surface of injured vessels on day 7, and the ratio of GFP- and vWF-positive area to the total luminal length on day 14 was 2.3-fold higher in the Ad-CCN1-EPC-transplanted group than in controls. Consistent with these findings, CCN1-stimulated EPC differentiation in vitro and 20 genes were found differentially expressed during CCN1-induced EPC differentiation, including Id1, Vegf-b, Vegf-c, Kdr, Igf-1, Ereg, Tgf, Mdk, Ptn, Timp2, etc. Among them, negative transcriptional regulator Id1 was associated with CCN1 effect on EPC differentiation. Our data suggest that CCN1, from the microenvironment of injured vessels, enhances reendothelialization via a direct action on EPC differentiation, revealing a possible new mechanism underlying the process of vascular repair.

Corepressor for element-1-silencing transcription factor preferentially mediates gene networks underlying neural stem cell fate decisions

The repressor element-1 (RE1) silencing transcription factor/neuron-restrictive silencer factor (REST/NRSF) silences neuronal genes in neural stem cells (NSCs) and nonneuronal cells through its role as a dynamic modular platform for recruitment of transcriptional and epigenetic regulatory cofactors to RE1-containing promoters. In embryonic stem cells, the REST regulatory network is highly integrated with the transcriptional circuitry governing self-renewal and pluripotency, although its exact functional role is unclear. The C-terminal cofactor for REST, CoREST, also acts as a modular scaffold, but its cell type-specific roles have not been elucidated. We used chromatin immunoprecipitation-on-chip to examine CoREST and REST binding sites in NSCs and their proximate progenitor species. In NSCs, we identified a larger number of CoREST (1,820) compared with REST (322) target genes. The majority of these CoREST targets do not contain known RE1 motifs. Notably, these CoREST target genes do play important roles in pluripotency networks, in modulating NSC identity and fate decisions and in epigenetic processes previously associated with both REST and CoREST. Moreover, we found that NSC-mediated developmental transitions were associated primarily with liberation of CoREST from promoters with transcriptional repression favored in less lineage-restricted radial glia and transcriptional activation favored in more lineage-restricted neuronal-oligodendrocyte precursors. Clonal NSC REST and CoREST gene manipulation paradigms further revealed that CoREST has largely independent and previously uncharacterized roles in promoting NSC multilineage potential and modulating early neural fate decisions.

Intersegmental vessel formation in zebrafish: requirement for VEGF but not BMP signalling revealed by selective and non-selective BMP antagonists

BACKGROUND AND PURPOSE

Bone morphogenetic proteins (BMPs) were first identified through their role in inducing bone and cartilage formation, but many other important functions have since been ascribed to BMPs, including dorsoventral patterning, angiogenesis and tissue homeostasis. Using dorsomorphin and LDN193189, selective small molecule inhibitors of BMP signalling, we investigated the role of BMP signalling in early vascular patterning in zebrafish.

EXPERIMENTAL APPROACH

The effects of dorsomorphin and LDN193189 on vascular endothelial growth factor-a (VEGF) and BMP signalling in developing zebrafish and in human pulmonary artery endothelial cells were determined using confocal microscopy, Western blotting and quantitative PCR.

KEY RESULTS

We showed that dorsomorphin, similar to the VEGF inhibitor SU5416, strongly inhibits intersegmental vessel formation in zebrafish and that this is due to inhibition of VEGF activation of VEGF receptor 2 (VEGFR2), leading to reduced VEGF-induced phospho-ERK (extracellular regulated kinase) 1/2 and VEGF target gene transcription. These effects occurred at concentrations of dorsomorphin that block BMP signalling. We also showed that LDN193189, an analogue of dorsomorphin, more potently blocks BMP signalling but has no effect on VEGF signalling in zebrafish and does not disrupt early vascular patterning.

CONCLUSIONS AND IMPLICATIONS

Dorsomorphin inhibits both BMP and VEGF signalling, whereas LDN193189 is a more selective BMP antagonist. Results obtained in cardiovascular studies using dorsomorphin need to be interpreted with caution, and use of LDN193189 would be preferable due to its selectivity. Our data also suggest that BMP signalling is dispensable for early patterning of intersegmental vessels in zebrafish.

Using the transcription factor inhibitor of DNA binding 1 to selectively target endothelial progenitor cells offers novel strategies to inhibit tumor angiogenesis and growth

Tumor angiogenesis is essential for malignant growth and metastasis. Bone marrow (BM)-derived endothelial progenitor cells (EPC) contribute to angiogenesis-mediated tumor growth. EPC ablation can reduce tumor growth; however, the lack of a marker that can track EPCs from the BM to tumor neovasculature has impeded progress in understanding the molecular mechanisms underlying EPC biology. Here, we report the use of transgenic mouse and lentiviral models to monitor the BM-derived compartment of the tumor stroma; this approach exploits the selectivity of the transcription factor inhibitor of DNA binding 1 (Id1) for EPCs to track EPCs in the BM, blood, and tumor stroma, as well as mature EPCs. Acute ablation of BM-derived EPCs using Id1-directed delivery of a suicide gene reduced circulating EPCs and yielded significant defects in angiogenesis-mediated tumor growth. Additionally, use of the Id1 proximal promoter to express microRNA-30-based short hairpin RNA inhibited the expression of critical EPC-intrinsic factors, confirming that signaling through vascular endothelial growth factor receptor 2 is required for EPC-mediated tumor biology. By exploiting the selectivity of Id1 gene expression in EPCs, our results establish a strategy to track and target EPCs in vivo, clarifying the significant role that EPCs play in BM-mediated tumor angiogenesis.

Age-related properties of the tumour vasculature in renal cell carcinoma

OBJECTIVE

To assess whether ageing processes influence angiogenesis in renal cell carcinoma (RCC) we carried out a pilot study of vascular properties in a series of archival primary kidney tumours in patients of different ages.

PATIENTS AND METHODS

A cohort of patients with RCC was identified restrospectively, with an age range of 35-84 years. Paraffin-embedded, formalin-fixed sections of surgical tumour specimens were stained for endothelial (CD31, von Willebrand factor [vWF]), pericyte (alpha smooth muscle actin [SMA]) and leucocytic (CD45) markers, as well as for proliferative (Ki67) and angiogenic activity (tumour endothelial markers [TEMs], delta-like 4 [Dll4], Dll1, endothelial nitric oxide synthase [eNOS]). Vascular properties were compared between patients above and below 65 years of age.

RESULTS

Microvascular density (MVD) within capillary hot spots was generally higher in patients with non-metastatic clear-cell RCC (ccRCC; n = 21) than in those with metastatic RCC (mRCC; n= 9). Patients with ccRCC who were more than 65 years old showed significantly higher MVD than their younger (< 65 years) counterparts. There were dividing (Ki67-positive) endothelial and mural cells in both small (< 20 µm) capillary and large (> 20 µm), pre-capillary vessels, suggesting the involvement of both angiogenic and remodelling/arteriogenic processes. Tumour endothelial markers (TEM1, TEM7, TEM8), Notch ligands (Dll1, Dll4), and other molecular characteristics (eNOS) were analysed. Age-related differences were observed in the frequency of pre-capillary vessels expressing Dll1, which was significantly higher in tumours of younger patients (< 65 years), while eNOS was more prevalent among capillaries associated with ccRCC in older patients (>6 5 years).

CONCLUSIONS

The results of the present study suggest that age influences the structural and molecular properties of the tumour vasculature in ccRCC. We postulate that vascular ageing could also be relevant in the context of anti-angiogenic therapy.

The PI3K/Akt pathway upregulates Id1 and integrin α4 to enhance recruitment of human ovarian cancer endothelial progenitor cells

Background

Endothelial progenitor cells (EPCs) contribute to tumor angiogenesis and growth. We aimed to determine whether inhibitors of differentiation 1 (Id1) were expressed in circulating EPCs of patients with ovarian cancer, whether Id1 could mediate EPCs mobilization and recruitment, and, if so, what underlying signaling pathway it used.

Methods

Circulating EPCs cultures were from 25 patients with ovarian cancer and 20 healthy control subjects. Id1 and integrin α4 expression were analyzed by real-time reverse transcription-polymerase chain reaction and western blot. EPCs proliferation, migration, and adhesion were detected by MTT, transwell chamber, and EPCs-matrigel adhesion assays. Double-stranded DNA containing the interference sequences were synthesized according to the structure of a pGCSIL-GFP viral vector and then inserted into a linearized vector. Positive clones were identified as lentiviral vectors that expressed human Id1 short hairpin RNA (shRNA).

Results

Id1 and integrin α4 expression were increased in EPCs freshly isolated from ovarian cancer patients compared to those obtained from healthy subjects. siRNA-mediated Id1 downregulation substantially reduced EPCs function and integrin α4 expression. Importantly, Inhibition of PI3K/Akt inhibited Id1 and integrin α4 expression, resulting in the decreasing biological function of EPCs.

Conclusions

Id1 induced EPCs mobilization and recruitment is mediated chiefly by the PI3K/Akt signaling pathway and is associated with activation of integrin α4.

WSS25 inhibits growth of xenografted hepatocellular cancer cells in nude mice by disrupting angiogenesis via blocking bone morphogenetic protein (BMP)/Smad/Id1 signaling

The highly expressed Id1 (inhibitor of DNA binding/differentiation) protein promotes angiogenesis in HCC and is a well established target for anti-angiogenesis therapeutic strategies. Heparan sulfate (HS) mimetics such as PI-88 can abrogate HS-protein interactions to inhibit angiogenesis. Id1 is the direct downstream effector of bone morphogenetic proteins (BMPs), which are angiogenic and HS-binding proteins. Thus, targeting BMPs by HS mimetics may inhibit angiogenesis via attenuating Id1 expression. We report here that a HS mimetic WSS25 potently inhibited the tube formation of HMEC-1 cells on Matrigel and their migration. Meanwhile, WSS25 (25 μg/ml) nearly completely blocked Id1 expression in the HMEC-1 cells as demonstrated by oligo-angiogenesis microarray analysis and further confirmed by RT-PCR and Western blotting. BMP/Smad/Id1 signaling also was blocked by WSS25 treatment in HMEC-1 cells. Importantly, Id1 knockdown in HMEC-1 cells caused the disruption of their tube formation on Matrigel. By employing quartz crystal microbalance analysis, we found that WSS25 strongly bound to BMP2. Moreover, WSS25 impaired BMP2-induced tube formation of HMEC-1 cells on Matrigel and angiogenesis in Matrigel transplanted into C57BL6 mice. Furthermore, WSS25 (100 mg/kg) abrogated the growth of HCC cells xenografted in male nude mice. Immunohistochemical analysis showed that both the expression of Id1 and the endothelial cell marker CD31 were lower in the WSS25-treated tumor tissue than in the control. Therefore, WSS25 is a potential drug candidate for HCC therapy as a tumor angiogenesis inhibitor.

Affinity of synthetic peptide fragments of MyoD for Id1 protein and their biological effects in several cancer cells

MyoD is a DNA-binding protein capable of specific interactions that involve the helix-loop-helix (HLH) domain. The HLH motif of MyoD can form oligomers with the HLH motif of Id1 (the inhibitor of DNA-binding proteins) that folds into a highly stable helical conformation stabilized by the self-association. The Id family consists of four related proteins that contain a highly conserved dimerization motif known as the HLH domain. In signaling pathways, Id proteins act as dominant negative antagonists of the basic helix-loop-helix (bHLH) family of transcription factors which play important roles in cellular development, proliferation, and differentiation. The mechanism of Id proteins is to antagonize bHLH proteins by binding as dominant negative HLH proteins to form high-affinity heterodimers with other bHLH proteins, thereby preventing them from binding to DNA and inhibiting transcription of differentiation-associated genes. The goal of this study is to design and synthesize peptide fragments of MyoD with high affinity for Id1 to interrupt the interactions among Id1, MyoD, and other bHLH DNA-binding proteins and to inhibit the proliferation of cancer cells. Affinity of each peptide for Id1 was determined by surface plasmon resonance (SPR) technology. The secondary structure of each peptide was studied by circular dichroism (CD) spectroscopy. Biological effects of each peptide in several cancer cells such as breast and colon cancer cells were analyzed. Results demonstrated that the peptide 3C (H-Tyr-Ile-Glu-Gly-Leu-Gln-Ala-Leu-Leu-Arg-Asp-Gln-NH(2)) not only showed high affinity for Id1 but also exhibited antiproliferative effects in HT-29 and MCF-7 cancer cells; the IC(50) value of 3C was determined as 25 microM in both cells. The percentage of sub-G1 in the cell cycle of the cancer cells treated with 5 microM of 3C was increased, indicating the induced apoptosis of cancer cells by 3C. Taken together, the peptide 3C is a promising lead compound for the development of antiproliferative agents.

Bone morphogenetic protein 2 acts via inhibitor of DNA binding proteins to synergistically regulate follicle-stimulating hormone beta transcription with activin A

We recently reported that bone morphogenetic proteins (BMPs) 2 and 4 can stimulate FSHbeta-subunit (Fshb) transcription alone and in synergy with activins. We further showed that BMP2 signals via the BMP type IA receptor (or activin receptor-like kinase 3) to mediate its effects. However, the intracellular mechanisms through which BMP2 regulates Fshb are unknown. In the current study, we used cDNA microarray analyses (and validation by real-time quantitative RT-PCR) to identify BMP2 target genes in the murine gonadotrope cell line, LbetaT2. Short-interfering RNA-mediated knockdown, overexpression, and coimmunoprecipitation experiments were used to examine the potential functional roles of selected gene products. Quantitative RT-PCR analysis largely confirmed the results of the array analyses, and inhibitors of DNA binding 1, 2, and 3 (Id1, Id2, and Id3) were selected for functional analyses. Knockdown of endogenous Id2 or Id3, but not Id1, diminished the synergistic effects of BMP2 and activin A on Fshb transcription. Overexpression of Id1, Id2, or Id3 alone had no effect, but all three potentiated activin A or mothers against decapentaplegic homolog (SMAD)3 induction of Fshb transcription. Though the precise mechanism through which Ids produce their effects are not yet known, we observed physical interactions between Id1, Id2, or Id3 and SMAD3. Collectively, the data suggest that BMP2 synergistically regulates Fshb transcription with activins, at least in part, through the combined actions of Ids 2 or 3 and SMAD3.

Inhibitor of DNA binding-4 promotes angiogenesis and growth of glioblastoma multiforme by elevating matrix GLA levels

Inhibitor of differentiation-4 is highly expressed in glioblastoma multiforme (GBM). We report a novel pro-angiogenic function for inhibitor of differentiation-4 in the growth of glioblastoma xenografts. Tumor-derived cell cultures expressing elevated levels of ID4 produced enlarged xenografts in immunosuppressed mice that were better vascularized than corresponding control tumors and expressed elevated matrix GLA protein (MGP) that mediated enhanced tumor angiogenesis. Inhibition of MGP resulted in smaller and less vascularized xenografts. Our finding shows a novel function for ID4 in tumor angiogenesis, and identifies ID4 and MGP as possible therapeutic targets for GBM.

Osteosarcoma is characterised by reduced expression of markers of osteoclastogenesis and antigen presentation compared with normal bone

Background:

Osteosarcoma (OS) is the most common primary bone tumour in children and adolescents. Patients who respond poorly to chemotherapy have a higher risk of metastatic disease and 5-year survival rates of only 10–20%. Therefore, identifying molecular targets that are specific for OS, or more specifically, metastatic OS, will be critical to the development of new treatment strategies to improve patient outcomes.

Methods:

We performed a transcriptomic analysis of chemo-naive OS biopsies and non-malignant bone biopsies to identify differentially expressed genes specific to OS, which could provide insight into OS biology and chemoresistance.

Results:

Statistical analysis of the OS transcriptomes found differential expression of several metallothionein family members, as well as deregulation of genes involved in antigen presentation. Tumours also exhibited significantly increased expression of ID1 and profound down-regulation of S100A8, highlighting their potential as therapeutic targets for OS. Finally, we found a significant correlation between OS and impaired osteoclastogenesis and antigen-presenting activity. The reduced osteoclastogenesis and antigen-presenting activity were more profound in the chemoresistant OS samples.

Conclusion:

Our results indicate that OS displays gene signatures consistent with decreased antigen-presenting activity, enhanced chemoresistance, and impaired osteoclastogenesis. Moreover, these alterations are more pronounced in chemoresistant OS tumour samples.

Saving energy to fuel exercise: swimming suppresses oocyte development and downregulates ovarian transcriptomic response of rainbow trout Oncorhynchus mykiss

Metabolic processes and sexual maturation closely interact during the long-distance reproductive migration of many fish species to their spawning grounds. In the present study, we have used exercise experimentally to investigate the effects on sexual maturation in rainbow trout. Pubertal autumn-spawning seawater-raised female rainbow trout Oncorhynchus mykiss (n = 26; 50 cm, 1.5 kg) were rested or swum at a near optimal speed of 0.75 body lengths per second in a 6,000-liter swim flume under natural reproductive conditions (16 degrees C fresh-water, starvation, 8:16-h light-dark photoperiod). Fish were sampled after arrival and subsequently after 10 days (resting or swimming 307 km) and 20 days (resting or swimming 636 km). Ovarian development was significantly reduced in the swimmers. Analysis of the expression of key factors in the reproductive axis included pituitary kiss1-receptor, lh, and fsh and ovarian lh-receptor, fsh-receptor, aromatase, and vitellogenin-receptor (vtgr). Swimmers had lower pituitary lh and ovarian vtgr expression than resters. Furthermore, the number of late vitellogenic oocytes was lower in swimmers than in resters, probably resulting from the lower vtgr expression, and vitellogenin plasma levels were higher. Therefore, swimming exercise suppresses oocyte development possibly by inhibiting vitellogenin uptake. Transcriptomic changes that occurred in the ovary of exercised fish were investigated using a salmonid cDNA microarray platform. Protein biosynthesis and energy provision were among the 16 functional categories that were all downregulated in the ovary. Downregulation of the transcriptomic response in the ovary illustrates the priority of energy reallocation and will save energy to fuel exercise. A swimming-induced ovarian developmental suppression at the start of vitellogenesis during long-term reproductive migration may be a strategy to avoid precocious muscle atrophy.

BMP-induced REST regulates the establishment and maintenance of astrocytic identity

Astrocyte differentiation and maintenance is promoted by BMP signaling, which induces REST/NRSF to repress neuronal genes.

Once they have differentiated, cells retain their individual character and repress genes that are specifically expressed in other cell lineages, but how alternative fate choice is restricted during and/or after differentiation remains unclear. In the mammalian central nervous system, neurons, astrocytes, and oligodendrocytes are generated throughout life from common tripotent neural progenitor cells (NPCs). Bone morphogenetic proteins (BMPs) are well-known astrocyte-inducing cytokines. We show here that the expression of a transcriptional repressor, RE1 silencer of transcription (REST)/neuron-restrictive silencer factor (NRSF), is up-regulated and sustained by BMP signal activation in the course of astrocytic differentiation of NPCs, and restricts neuronal differentiation. We further show that, in differentiated astrocytes, endogenous REST/NRSF associates with various neuronal genes and that disruption of its function resulted in their derepression, thereby explaining how ectopic neuronal gene expression is prevented in cells with astrocytic traits. Collectively, our results suggest that REST/NRSF functions as a molecular regulator of the nonneuronal phenotype in astrocytes.

Inhibition of endothelial cell activation by bHLH protein E2-2 and its impairment of angiogenesis

E2-2 belongs to the basic helix-loop-helix (bHLH) family of transcription factors. E2-2 associates with inhibitor of DNA binding (Id) 1, which is involved in angiogenesis. In this paper, we demonstrate that E2-2 interacts with Id1 and provide evidence that this interaction potentiates angiogenesis. Mutational analysis revealed that the HLH domain of E2-2 is required for the interaction with Id1 and vice versa. In addition, Id1 interfered with E2-2-mediated effects on luciferase reporter activities. Interestingly, injection of E2-2-expressing adenoviruses into Matrigel plugs implanted under the skin blocked in vivo angiogenesis. In contrast, the injection of Id1-expressing adenoviruses rescued E2-2-mediated inhibition of in vivo angiogenic reaction. Consistent with the results of the Matrigel plug assay, E2-2 could inhibit endothelial cell (EC) migration, network formation, and proliferation. On the other hand, knockdown of E2-2 in ECs increased EC migration. The blockade of EC migration by E2-2 was relieved by exogenous expression of Id1. We also demonstrated that E2-2 can perturb VEGFR2 expression via inhibition of VEGFR2 promoter activity. This study suggests that E2-2 can maintain EC quiescence and that Id1 can counter this effect.

Role of inhibitor of DNA binding-1 protein is related to angiogenesis in the tumor advancement of uterine endometrial cancers

The inhibitor of DNA binding (ID)-1 protein, an inhibitor of basic helix-loop-helix transcription factors, has been found to be involved in multiple cellular functions. In the present study, ID-1 histoscores and mRNA levels were both significantly (p<0.05) increased in uterine endometrial cancers according to clinical stage, histological grade and depth of myometrial invasion. Furthermore, the 60-month survival rate of the 25 patients with high ID-1 was poor (52%), while that of the other 25 patients with low ID-1 was significantly higher (80%) (p<0.05). ID-1 histoscores and mRNA levels significantly (p<0.0001) correlated with microvessel counts in uterine endometrial cancers. Therefore, ID-1 acts on tumor advancement via angiogenic activity and can be considered a candidate prognostic indicator in uterine endometrial cancers.

Targeting Id1 and Id3 by a specific peptide aptamer induces E-box promoter activity, cell cycle arrest, and apoptosis in breast cancer cells

Inhibitors of differentiation or DNA binding (Id) proteins have been shown to be involved in tumor growth, invasiveness, metastasis, and angiogenesis. Overexpression of Id proteins, especially Id1, correlates with unfavorable clinical prognosis. Thus, they are attractive molecular targets for anticancer therapy. Overexpression of Id proteins mediates breast cancer metastasis to lung. Targeting Id1 and Id3 expression in breast cancer cells reduces breast cancer metastasis in animal models. Different breast tumors failed to grow and/or metastasize in Id1 (+/-) Id3 (-/-) mice. Id1 and Id3 preferentially dimerize with the key regulatory E-proteins which inhibit the expression of different tumor suppressor genes. Nevertheless, the inhibition of tumorigenic activities of Id1 and Id3 at protein level has never been studied. Here, we isolated a novel peptide aptamer, Id1/3-PA7, specifically interacting with Id1 and Id3 from randomized combinatorial expression library using yeast and mammalian two-hybrid systems. Intracellular delivered Id1/3-PA7 co-localized to Id1 and Id3 and interfered with their functions. It repressed E47 protein sequestration by Id1 and Id3, activated the E-box promoter and increased the expression level of cyclin-dependent kinase inhibitors (CDKN1A and CDKN1B) in a dose-dependent fashion, paralleled by the cleavage of poly ADP ribose polymerase (PARP). These effects were counteracted by ectopically overexpressed Id1 and Id3. Peptide aptamer Id1/3-PA7 induced cell cycle arrest and apoptosis in breast cancer cells MCF7 and MDA-MB-231. In conclusion, Id1/3-PA7 could represent a nontoxic exogenous agent that can significantly provoke antiproliferative and apoptotic effects in breast cancer cells, which are associated with deregulated expression of Id1 and Id3.

Inefficient skeletal muscle repair in inhibitor of differentiation knockout mice suggests a crucial role for BMP signaling during adult muscle regeneration

The bone morphogenetic protein (BMP) pathway is known to be involved in limb myogenesis during development, but whether it is involved in postnatal muscle regeneration is unclear. We have found that adult inhibitor of differentiation (Id)-mutant (Id1(+/-)Id3(-/-)) mice display delayed and reduced skeletal muscle regeneration after injury compared with either wild-type littermates or Id3-null mice. Immunoblotting of wild-type muscle lysates revealed that, not only were Id1 and Id3 highly upregulated within 24 h after injury, but other upstream components of the BMP pathway were as well, including the BMP receptor type II and phosphorylated Smad1/5/8 (pSmad1/5/8). Inhibition of BMP signaling in injured skeletal muscle by Noggin injection reduced pSmad1/5/8, Id1, and Id3 protein levels. The mouse myoblast-derived cell line C2C12 also expressed Id1, Id3, BMP receptor type II, and pSmad1/5/8 during proliferation, but all were reduced upon differentiation into myotubes. In addition, these cells secreted mature BMP-4, and BMP signaling could be inhibited with exogenous Noggin, causing a reduction in pSmad1/5/8, Id1, and Id3 levels. Confocal immunofluorescence microscopy revealed that activated Pax7(+) myoblasts coexpressed nuclear pSmad1/5/8, Id1, and Id3 in injured mouse skeletal muscle sections. Although we did not observe differences in the numbers of quiescent Pax7(+) satellite cells in adult uninjured hindlimb muscles, we did observe a significant reduction in the number of proliferating Pax7(+) cells in the Id-mutant mice after muscle injury compared with either wild-type or Id3-null mice. These data suggest a model in which BMP signaling regulates Id1 and Id3 in muscle satellite cells, which directs their proper proliferation before terminal myogenic differentiation after skeletal muscle injury in postnatal animals.

Inhibition of vasculogenesis, but not angiogenesis, prevents the recurrence of glioblastoma after irradiation in mice

Despite the high doses of radiation delivered in the treatment of patients with glioblastoma multiforme (GBM), the tumors invariably recur within the irradiation field, resulting in a low cure rate. Understanding the mechanism of such recurrence is therefore important. Here we have shown in an intracranial GBM xenograft model that irradiation induces recruitment of bone marrow-derived cells (BMDCs) into the tumors, restoring the radiation-damaged vasculature by vasculogenesis and thereby allowing the growth of surviving tumor cells. BMDC influx was initiated by induction of HIF-1 in the irradiated tumors, and blocking this influx prevented tumor recurrence. Previous studies have indicated that BMDCs are recruited to tumors in part through the interaction between the HIF-1-dependent stromal cell-derived factor-1 (SDF-1) and its receptor, CXCR4. Pharmacologic inhibition of HIF-1 or of the SDF-1/CXCR4 interaction prevented the influx of BMDCs, primarily CD11b+ myelomonocytes, and the postirradiation development of functional tumor vasculature, resulting in abrogation of tumor regrowth. Similar results were found using neutralizing antibodies against CXCR4. Our data therefore suggest a novel approach for the treatment of GBM: in addition to radiotherapy, the vasculogenesis pathway needs to be blocked, and this can be accomplished using the clinically approved drug AMD3100, a small molecule inhibitor of SDF-1/CXCR4 interactions.

Using molecular classification to predict gains in maximal aerobic capacity following endurance exercise training in humans

A low maximal oxygen consumption (VO2max) is a strong risk factor for premature mortality. Supervised endurance exercise training increases VO2max with a very wide range of effectiveness in humans. Discovering the DNA variants that contribute to this heterogeneity typically requires substantial sample sizes. In the present study, we first use RNA expression profiling to produce a molecular classifier that predicts VO2max training response. We then hypothesized that the classifier genes would harbor DNA variants that contributed to the heterogeneous VO2max response. Two independent preintervention RNA expression data sets were generated (n=41 gene chips) from subjects that underwent supervised endurance training: one identified and the second blindly validated an RNA expression signature that predicted change in VO2max ("predictor" genes). The HERITAGE Family Study (n=473) was used for genotyping. We discovered a 29-RNA signature that predicted VO2max training response on a continuous scale; these genes contained approximately 6 new single-nucleotide polymorphisms associated with gains in VO2max in the HERITAGE Family Study. Three of four novel candidate genes from the HERITAGE Family Study were confirmed as RNA predictor genes (i.e., "reciprocal" RNA validation of a quantitative trait locus genotype), enhancing the performance of the 29-RNA-based predictor. Notably, RNA abundance for the predictor genes was unchanged by exercise training, supporting the idea that expression was preset by genetic variation. Regression analysis yielded a model where 11 single-nucleotide polymorphisms explained 23% of the variance in gains in VO2max, corresponding to approximately 50% of the estimated genetic variance for VO2max. In conclusion, combining RNA profiling with single-gene DNA marker association analysis yields a strongly validated molecular predictor with meaningful explanatory power. VO2max responses to endurance training can be predicted by measuring a approximately 30-gene RNA expression signature in muscle prior to training. The general approach taken could accelerate the discovery of genetic biomarkers, sufficiently discrete for diagnostic purposes, for a range of physiological and pharmacological phenotypes in humans.

Elevated endogenous expression of the dominant negative basic helix-loop-helix protein ID1 correlates with significant centrosome abnormalities in human tumor cells

Background

ID proteins are dominant negative inhibitors of basic helix-loop-helix transcription factors that have multiple functions during development and cellular differentiation. Ectopic (over-)expression of ID1 extends the lifespan of primary human epithelial cells. High expression levels of ID1 have been detected in multiple human malignancies, and in some have been correlated with unfavorable clinical prognosis. ID1 protein is localized at the centrosomes and forced (over-)expression of ID1 results in errors during centrosome duplication.

Results

Here we analyzed the steady state expression levels of the four ID-proteins in 18 tumor cell lines and assessed the number of centrosome abnormalities. While expression of ID1, ID2, and ID3 was detected, we failed to detect protein expression of ID4. Expression of ID1 correlated with increased supernumerary centrosomes in most cell lines analyzed.

Conclusions

This is the first report that shows that not only ectopic expression in tissue culture but endogenous levels of ID1 modulate centrosome numbers. Thus, our findings support the hypothesis that ID1 interferes with centrosome homeostasis, most likely contributing to genomic instability and associated tumor aggressiveness.

Genetic and pharmacological targeting of activin receptor-like kinase 1 impairs tumor growth and angiogenesis

Members of the transforming growth factor β (TGF-β) family have been genetically linked to vascular formation during embryogenesis. However, contradictory studies about the role of TGF-β and other family members with reported vascular functions, such as bone morphogenetic protein (BMP) 9, in physiological and pathological angiogenesis make the need for mechanistic studies apparent. We demonstrate, by genetic and pharmacological means, that the TGF-β and BMP9 receptor activin receptor-like kinase (ALK) 1 represents a new therapeutic target for tumor angiogenesis. Diminution of ALK1 gene dosage or systemic treatment with the ALK1-F_c fusion protein RAP-041 retarded tumor growth and progression by inhibition of angiogenesis in a transgenic mouse model of multistep tumorigenesis. Furthermore, RAP-041 significantly impaired the in vitro and in vivo angiogenic response toward vascular endothelial growth factor A and basic fibroblast growth factor. In seeking the mechanism for the observed effects, we uncovered an unexpected signaling synergy between TGF-β and BMP9, through which the combined action of the two factors augmented the endothelial cell response to angiogenic stimuli. We delineate a decisive role for signaling by TGF-β family members in tumor angiogenesis and offer mechanistic insight for the forthcoming clinical development of drugs blocking ALK1 in oncology.

Differential expression of Shh and BMP signaling in the potential conversion of human adipose tissue stem cells into neuron-like cells in vitro

The nervous system (NS) has a limited self-repair capability and adult neurogenesis is limited to certain regions of the brain. This generates a great interest in using stem cells to repair the NS. Previous reports have shown the differentiation of adipose tissue-derived mesenchymal stem cells (ASCs) in neuron-like cells when cultures are enriched with growth factors participating in embryonic and adult neurogenesis. Therefore, it could be thought that there exists a functional parallelism between neurogenesis and neuronal differentiation of ASCs. For this reason, the goal of this work was to study the differential gene expression of Shh and BMP genetic pathways involved in cell fate determination and proliferation. In this study we demonstrated that hASCs are endowed with active Hedgehog and BMP signaling pathways through the expression of genes of both cascades and that their expressions are downregulated after neuronal induction. This idea is in accordance with the facts that Shh and BMP signaling is involved in the maintenance of cells with stem cells properties and that proliferation decreases during the process of differentiation. Furthermore, Noggin expression was detected in induced hASCs whereas there was no expression in noninduced cells, which indicates that these cells are probably adopting a neuronal fate because noggin diverts neural stem cells from glial to neuronal fate. We also detected FM1-43 and synaptophisin staining, which is evidence of the presence of putative functional presynaptic terminals, a neuron-specific property. These results could partially contribute to the elucidation of the molecular mechanisms involved in neuronal differentiation of adult human nonneural tissues.

Role of endothelial progenitor cells in breast cancer angiogenesis: from fundamental research to clinical ramifications

Blood vessel formation (neovascularization) in tumors can occur through two mechanisms: angiogenesis and vasculogenesis. Angiogenesis results from proliferation and sprouting of existing blood vessels close to the tumor, while vasculogenesis is believed to arise from recruitment of circulating cells, largely derived from the bone marrow, and de novo clonal formation of blood vessels from these cells. Increasing evidence in animal models indicate that bone marrow-derived endothelial precursor cells (EPC) can contribute to tumor angiogenesis. This review aims to collate existing literature and provide an overview on the current knowledge of EPC involvement in breast cancer angiogenesis. We also discuss recent attempts to use EPC as biomarker and therapeutic target in clinical trials.

Impaired terminal differentiation of hippocampal granule neurons and defective contextual memory in PC3/Tis21 knockout mice

Neurogenesis in the dentate gyrus of the adult hippocampus has been implicated in neural plasticity and memory, but the molecular mechanisms controlling the proliferation and differentiation of newborn neurons and their integration into the synaptic circuitry are still largely unknown. To investigate this issue, we have analyzed the adult hippocampal neurogenesis in a PC3/Tis21-null mouse model. PC3/Tis21 is a transcriptional co-factor endowed with antiproliferative and prodifferentiative properties; indeed, its upregulation in neural progenitors has been shown to induce exit from cell cycle and differentiation. We demonstrate here that the deletion of PC3/Tis21 causes an increased proliferation of progenitor cells in the adult dentate gyrus and an arrest of their terminal differentiation. In fact, in the PC3/Tis21-null hippocampus postmitotic undifferentiated neurons accumulated, while the number of terminally differentiated neurons decreased of 40%. As a result, PC3/Tis21-null mice displayed a deficit of contextual memory. Notably, we observed that PC3/Tis21 can associate to the promoter of Id3, an inhibitor of proneural gene activity, and negatively regulates its expression, indicating that PC3/Tis21 acts upstream of Id3. Our results identify PC3/Tis21 as a gene required in the control of proliferation and terminal differentiation of newborn neurons during adult hippocampal neurogenesis and suggest its involvement in the formation of contextual memories.

DeltaEF1 promotes breast cancer cell proliferation through down-regulating p21 expression

Although the zinc finger-homeodomain transcription factor deltaEF1 is implied as a regulatory factor at the crossroad between proliferation and differentiation in carcinogenesis, its potential effect in the regulation of cell cycle progression has not been well elucidated. In our present study, we provide novel finding that, in breast cancer, the ectopic expression of deltaEF1 in MDA-MB-231 cells significantly promoted cell proliferation by increasing the cell number in S phase of the cell cycle. In contrast, deltaEF1 knockdown by RNA interference exhibited an opposite effect, highlighting a potent role of deltaEF1 to promote G1-S transition of breast cancer cells. Moreover, we demonstrated that deltaEF1 down-regulated p21 and concurrently up-regulated the expressions of CDK2 and CDK4 during this process. Further, deltaEF1 inhibited p21 transcription by recruiting to the E(2) box element on the p21 promoter. Depletion of endogenous deltaEF1 in MDA-MB-231 cells was sufficient to allow an inherent release of p21 expression, thus resulting in the cell cycle arrest. In addition, the stimulatory effect of deltaEF1 on cell proliferation through p21 regulation was supported by an inverse correlation of deltaEF1 and p21 expressions observed in both breast cancer cell lines and clinical tumor specimens. Taken together, these observations suggest a dual effect of deltaEF1 in promoting breast cancer cell proliferation, by differentially regulating the cell cycle regulatory proteins.

Prostate cancer cells modulate osteoblast mineralisation and osteoclast differentiation through Id-1

Background:

Id-1 is overexpressed in and correlated with metastatic potential of prostate cancer. The role of Id-1 in this metastatic process was further analysed.

Methods:

Conditioned media from prostate cancer cells, expressing various levels of Id-1, were used to stimulate pre-osteoclast differentiation and osteoblast mineralisation. Downstream effectors of Id-1 were identified. Expressions of Id-1 and its downstream effectors in prostate cancers were studied using immunohistochemistry in a prostate cancer patient cohort (N=110).

Results:

We found that conditioned media from LNCaP prostate cancer cells overexpressing Id-1 had a higher ability to drive osteoclast differentiation and a lower ability to stimulate osteoblast mineralisation than control, whereas conditioned media from PC3 prostate cancer cells with Id-1 knockdown were less able to stimulate osteoclast differentiation. Id-1 was found to negatively regulate TNF-β and this correlation was confirmed in human prostate cancer specimens (P=0.03). Furthermore, addition of recombinant TNF-β to LNCaP Id-1 cell-derived media blocked the effect of Id-1 overexpression on osteoblast mineralisation.

Conclusion:

In prostate cancer cells, the ability of Id-1 to modulate bone cell differentiation favouring metastatic bone disease is partially mediated by TNF-β, and Id-1 could be a potential therapeutic target for prostate cancer to bone metastasis.

Overexpression of inhibitor of DNA-binding (ID)-1 protein related to angiogenesis in tumor advancement of ovarian cancers

Background

The inhibitor of DNA-binding (ID) has been involved in cell cycle regulation, apoptosis and angiogenesis. This prompted us to study ID functions in tumor advancement of ovarian cancers.

Methods

Sixty patients underwent surgery for ovarian cancers. In ovarian cancers, the levels of ID-1, ID-2 and ID-3 mRNAs were determined by real-time reverse transcription-polymerase chain reaction. The histoscore with the localization of ID-1 was determined by immunohistochemistry. Patient prognosis was analyzed with a 36-month survival rate. Microvessel counts were determined by immunohistochemistry for CD34 and factor VIII-related antigen.

Results

ID-1 histoscores and mRNA levels both significantly (p < 0.001) increased in ovarian cancers according to clinical stage, regardless of histopathological type. Furthermore, 30 patients with high ID-1 expression had a lower survival rate (53%) compared to patients with low ID-1 expression (80%). ID-1 histoscores and mRNA levels significantly (p < 0.0001) correlated with microvessel counts in ovarian cancers.

Conclusion

ID-1 increased in ovarian cancer cells during tumor progression. Moreover, ID-1 expression levels correlated with microvessel counts. Therefore, ID-1 might work on tumor advancement via angiogenesis and is considered to be a candidate for a prognostic indicator in ovarian cancers.

Effect of PTTG on endogenous gene expression in HEK 293 cells

Background

Pituitary tumor transforming gene (PTTG), also known as securin, is highly expressed in various tumors including pituitary, thyroid, colon, ovary, testis, lung, and breast. An overexpression of PTTG enhances cell proliferation, induces cellular transformation in vitro, and promotes tumor development in nude mice. PTTG also inhibits separation of sister chromatids leading to aneuploidy and genetic instability. A great amount of work has been undertaken to understand the biology of PTTG and its expression in various tumors. However, mechanisms by which PTTG mediates its tumorigenic function are not fully understood. To utilize this gene for cancer therapy, identification of the downstream signaling genes regulated by PTTG in mediation of its tumorigenic function is necessary. For this purpose, we expressed PTTG in human embryonic kidney (HEK293) cells that do not express PTTG and analyzed the downstream genes using microarray analysis.

Results

A total of 22,277 genes printed on an Affymetrix HG-U133A 2.0 GeneChip™ array were screened with labeled cRNA prepared from HEK293 cells infected with adenovirus vector expressing PTTG cDNA (AdPTTG cDNA) and compared with labeled cRNA prepared from HEK293 cells infected with control adenovirus (control Ad) or adenovirus vector expressing GFP (AdGFP). Out of 22,277 genes, 71 genes were down-regulated and 35 genes were up-regulated with an FDR corrected p-value of ≤ 0.05 and a fold change of ≥2. Most of the altered genes identified are involved in the cell cycle and cell apoptosis; a few are involved in mRNA processing and nitrogen metabolism. Most of the up-regulated genes belong to the histone protein family.

Conclusion

PTTG is a well-studied oncogene for its role in tumorigenesis. In addition to its importance in regulation of the cell cycle, this gene has also been recently shown to play a role in the induction of cell apoptosis. The microarray analysis in the present study demonstrated that PTTG may induce apoptosis by down-regulation of oncogenes such as v-Jun and v-maf and up-regulation of the histone family of genes.

Quantitative Transcription Factor Analysis of Undifferentiated Single Human Embryonic Stem Cells

Background: Human embryonic stem cells (hESCs) require expression of transcription factor genes POU5F1 (POU class 5 homeobox 1), NANOG (Nanog homeobox), and SOX2 [SRY (sex determining region Y)-box 2] to maintain their capacity for self-renewal and pluripotency. Because of the heterogeneous nature of cell populations, it is desirable to study the gene regulation in single cells. Large and potentially important fluctuations in a few cells cannot be detected at the population scale with microarrays or sequencing technologies. We used single-cell gene expression profiling to study cell heterogeneity in hESCs.

Methods: We collected 47 single hESCs from cell line SA121 manually by glass capillaries and 57 single hESCs from cell line HUES3 by flow cytometry. Single hESCs were lysed and reverse-transcribed. Reverse-transcription quantitative real-time PCR was then used to measure the expression POU5F1, NANOG, SOX2, and the inhibitor of DNA binding genes ID1, ID2, and ID3. A quantitative noise model was used to remove measurement noise when pairwise correlations were estimated.

Results: The numbers of transcripts per cell varied &gt;100-fold between cells and showed lognormal features. POU5F1 expression positively correlated with ID1 and ID3 expression (P &lt; 0.05) but not with NANOG or SOX2 expression. When we accounted for measurement noise, SOX2 expression was also correlated with ID1, ID2, and NANOG expression (P &lt; 0.05).

Conclusions: We demonstrate an accurate method for transcription profiling of individual hESCs. Cell-to-cell variability is large and is at least partly nonrandom because we observed correlations between core transcription factors. High fluctuations in gene expression may explain why individual cells in a seemingly undifferentiated cell population have different susceptibilities for inductive cues.

Id1 represses osteoclast-dependent transcription and affects bone formation and hematopoiesis

BACKGROUND

The bone-bone marrow interface is an area of the bone marrow microenvironment in which both bone remodeling cells, osteoblasts and osteoclasts, and hematopoietic cells are anatomically juxtaposed. The close proximity of these cells naturally suggests that they interact with one another, but these interactions are just beginning to be characterized.

METHODOLOGY/PRINCIPAL FINDINGS

An Id1(-/-) mouse model was used to assess the role of Id1 in the bone marrow microenvironment. Micro-computed tomography and fracture tests showed that Id1(-/-) mice have reduced bone mass and increased bone fragility, consistent with an osteoporotic phenotype. Osteoclastogenesis and pit formation assays revealed that loss of Id1 increased osteoclast differentiation and resorption activity, both in vivo and in vitro, suggesting a cell autonomous role for Id1 as a negative regulator of osteoclast differentiation. Examination by flow cytometry of the hematopoietic compartment of Id1(-/-) mice showed an increase in myeloid differentiation. Additionally, we found increased expression of osteoclast genes, TRAP, Oscar, and CTSK in the Id1(-/-) bone marrow microenvironment. Lastly, transplantation of wild-type bone marrow into Id1(-/-) mice repressed TRAP, Oscar, and CTSK expression and activity and rescued the hematopoietic and bone phenotype in these mice.

CONCLUSIONS/SIGNIFICANCE

In conclusion, we demonstrate an osteoporotic phenotype in Id1(-/-) mice and a mechanism for Id1 transcriptional control of osteoclast-associated genes. Our results identify Id1 as a principal player responsible for the dynamic cross-talk between bone and bone marrow hematopoietic cells.

The alteration of Id-1 and TSP-1 expression in mucoepidermoid carcinoma associated with its clinical features and prognosis

Expression of Id-1 (inhibitors of DNA binding/differentiation protein 1) and TSP-1 (thrombospondin-1) in mucoepidermoid carcinoma and their relationship to pathological features and prognosis was studied. Moderately and poorly differentiated groups had significantly higher Id-1 positive expression rate (p<0.05) than well differentiated carcinoma. Stages III-IV showed significant increase of Id-1 positive expression rate (p<0.05) compared with stages I and II. Id-1 positive expression was significantly higher in patients with cervical lymph node metastasis or relapse at 5 years (p<0.05). After that, patients with negative Id-1 expression had significantly higher tumor-free survival than patients with positive expression (p<0.05). Correlation between the expression of Id-1 and TSP-1 in mucoepidermoid carcinoma was negative (p<0.05). Poorly differentiated groups show significantly lower TSP-1 positive expression rate than well differentiated groups (p<0.05). No significant differences of TSP-1 positive expression were detected with clinical stage. TSP-1 positive expression was significantly lower in patients with cervical lymph node metastasis or relapse at 5 years (p<0.05). After 5 years, patients with positive TSP-1 expression had significantly higher tumor-free survival than patients with negative TSP-1. Positive Id-1 expression is associated with high malignancy/poor prognosis; positive TSP-1 expression is associated with low malignancy/good prognosis. Protein expression status may help assess tumor malignancy and patient prognosis.

Id-1 promotes tumorigenicity and metastasis of human esophageal cancer cells through activation of PI3K/AKT signaling pathway

Id-1 (inhibitor of differentiation or DNA binding) is a helix-loop-helix protein that is overexpressed in many types of cancer including esophageal squamous cell carcinoma (ESCC). We previously reported that ectopic Id-1 expression activates the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (AKT) signaling pathway in human esophageal cancer cells. In this study, we confirmed a positive correlation between Id-1 and phospho-AKT (Ser473) expressions in ESCC cell lines, as well as in ESCC on a tissue microarray. To investigate the significance of Id-1 in esophageal cancer progression, ESCC cells with stable ectopic Id-1 expression were inoculated subcutaneously into the flank of nude mice and were found to form larger tumors that showed elevated Ki-67 proliferation index and increased angiogenesis, as well as reduced apoptosis, compared with control cells expressing the empty vector.The Id-1-overexpressing cells also exhibited enhanced metastatic potential in the experimental metastasis assay. Treatment with the PI3K inhibitor LY294002 attenuated the tumor promotion effects of Id-1, indicating that the effects were mediated by the PI3K/AKT signaling pathway. In addition, our in vitro experiments showed that ectopic Id-1 expression altered the expression levels of markers associated with epithelial-mesenchymal transition and enhanced the migration ability of esophageal cancer cells. The Id-1-overexpressing ESCC cells also exhibited increased invasive potential, which was in part due to PI3K/AKT-dependent modulation of matrix metalloproteinase-9 expression. In conclusion, our results provide the first evidence that Id-1 promotes tumorigenicity and metastasis of human esophageal cancer in vivo and that the PI3K inhibitor LY294002 can attenuate these effects.

The angiotensin II type 2 receptor in the brain

Recent clinical studies indicate that blockade of the renin-angiotensin system is important to prevent stroke, and accumulating results of basic research also indicate the possible involvement of the central renin-angiotensin system in ischaemic brain damage and cognition. When the angiotensin II type 1 receptor is blocked by an angiotensin type 1 receptor blocker, unbound angiotensin II acts preferentially on the angiotensin II type 2 (AT(2)) receptor. These results suggest the pathophysiological importance of the AT(2) receptor in the clinical use of angiotensin type 1 receptor blockers, which are widely used in patients with hypertension with the expectation of a decrease in the onset of cardiovascular and cerebrovascular disease. We review here the possible roles of AT(2) receptor activation in the brain, focusing on ischaemic stroke, cognitive function and neurogenesis, and potential effects of specific AT(2) receptor agonists.

KLF17 is a negative regulator of epithelial-mesenchymal transition and metastasis in breast cancer

Metastasis is a complex multistep process, which requires the concerted action of many genes and is the primary cause of cancer death. Both pathways that regulate metastasis enhancement and those that regulate its suppression contribute to the tumour dissemination process. To identify new metastasis suppressors, we set up a forward genetic screen in a mouse model. We transduced a genome-wide RNA interference (RNAi) library into the non-metastatic 168FARN breast cancer cell line and orthotopically transplanted the cells into mouse mammary fat pads. We then selected cells that could metastasize to the lung and identified an RNAi for the KLF17 gene. Conversely, we demonstrate that ectopic expression of KLF17 in a highly metastatic 4T1 breast cancer cell line inhibits the ability of cells to metastasize from the mammary fat pad to the lung. We also show that suppression of KLF17 expression promotes breast cancer cell invasion and epithelial-mesenchymal transition (EMT), and that KLF17 protein functions by directly binding to the promoter region of Id1 (which encodes a key metastasis regulator in breast cancer) to inhibit its transcription. Finally, we demonstrate that KLF17 expression is significantly downregulated in primary human breast cancer samples and that the combined expression pattern of KLF17 and Id1 can serve as a potential biomarker for lymph node metastasis in breast cancer.

The execution of the transcriptional axis mutant p53, E2F1 and ID4 promotes tumor neo-angiogenesis

ID4 (inhibitor of DNA binding 4) is a member of a family of proteins that function as dominant-negative regulators of basic helix-loop-helix transcription factors. Growing evidence links ID proteins to cell proliferation, differentiation and tumorigenesis. Here we identify ID4 as a transcriptional target of gain-of-function p53 mutants R175H, R273H and R280K. Depletion of mutant p53 protein severely impairs ID4 expression in proliferating tumor cells. The protein complex mutant p53-E2F1 assembles on specific regions of the ID4 promoter and positively controls ID4 expression. The ID4 protein binds to and stabilizes mRNAs encoding pro-angiogenic factors IL8 and GRO-alpha. This results in the increase of the angiogenic potential of cancer cells expressing mutant p53. These findings highlight the transcriptional axis mutant p53, E2F1 and ID4 as a still undefined molecular mechanism contributing to tumor neo-angiogenesis.

A novel interplay between Epac/Rap1 and mitogen-activated protein kinase kinase 5/extracellular signal-regulated kinase 5 (MEK5/ERK5) regulates thrombospondin to control angiogenesis

Tumors depend upon angiogenesis for growth and metastasis. It is therefore critical to understand the inhibitory signaling mechanisms in endothelial cells that control angiogenesis. Epac is a cyclic adenosine 5'-monophosphate-activated guanine nucleotide exchange factor for Rap1. In this study, we show that activation of Epac or Rap1 leads to potent inhibition of angiogenesis in vivo. Epac/Rap1 activation down-regulates inhibitor of differentiation 1 (Id1), which negatively regulates thrombospondin-1 (TSP1), an inhibitor of angiogenesis. Consistent with this mechanism, activation of Epac/Rap 1 induces expression of TSP1; conversely, depletion of Epac reduces TSP1 levels in endothelial cells. Blockade of TSP1 binding to its receptor, CD36, rescues inhibition of chemotaxis or angiogenesis by activated Epac/Rap1. Mitogen-activated protein kinase kinase 5, a downstream mediator of vascular endothelial growth factor, antagonizes the effects of Epac/Rap1 by inducing Id1 and suppressing TSP1 expression. Finally, TSP1 is also secreted by fibroblasts in response to Epac/Rap1 activation. These results identify Epac and Rap1 as inhibitory regulators of the angiogenic process, implicate Id1 and TSP1 as downstream mediators of Epac/Rap1, and highlight a novel interplay between pro- and antiangiogenic signaling cascades involving multiple cell types within the angiogenic microenvironment.

Tumor angiogenesis in melanoma

A large number of clinical studies are being conducted to assess the effects of angiogenesis inhibitors in the treatment of patients who have metastatic melanoma. It has become increasingly clear that a therapeutic approach that combines angiogenesis inhibitors with cytotoxic agents or other treatment modalities is more likely to result in a clinical benefit for patients rather than antiangiogenesis treatments alone. However, a targeted treatment approach with antiangiogenic agents needs to be based on an in-depth understanding of the complex mechanisms involved in melanoma tumor angiogenesis.

Suppression of tumor angiogenesis by Galpha(13) haploinsufficiency

Heterotrimeric G proteins are critical transducers of cellular signaling. Of the four families of G proteins, the physiological function of Galpha(13) is less well understood. Galpha(13) gene-deleted mice die at embryonic day approximately 9.5. Here, we show that heterozygous Galpha(13)(+/-) mice display defects in adult angiogenesis. Female Galpha(13)(+/-) mice showed a higher number of immature follicles and a lower density of blood vessels in the mature corpus luteum compared with Galpha(13)(+/+) mice. Furthermore, implanted tumors grew slower in Galpha(13)(+/-) host mice. These tumor tissues had many fewer blood vessels compared with those from Galpha(13)(+/+) host mice. Moreover, bone marrow-derived progenitor cells from Galpha(13)(+/+) mice rescued the failed growth of allografted tumors when reconstituted into irradiated Galpha(13)(+/-) mice. Hence, Galpha(13) is haploinsufficient for adult angiogenesis in both the female reproductive system and tumor angiogenesis.