Hypoxic regulation of vascular endothelial growth factor mRNA stability requires the cooperation of multiple RNA elements

MicroRNA-299-3p inhibits cell proliferation, motility, invasion and angiogenesis via VEGFA in upper tract urothelial carcinoma

BACKGROUND

Upper tract urothelial carcinoma (UTUC) is a rare tumor with extraordinarily different features between Eastern and Western countries. Vascular endothelial growth factor-A (VEGFA) was originally identified as a secreted signaling protein and regulator of vascular development and cancer progression. In this study, we aimed to elucidate the molecular mechanisms underlying the regulation of VEGFA by microRNA in UTUC.

METHODS

VEGFA expression was evaluated by immunohistochemistry in 140 human UTUC tissue samples. Next, we assessed the regulatory relationship between VEGFA and miR-299-3p by real-time PCR, western blotting, ELISA and dual-luciferase reporter assays using two UTUC cell lines. The role of miR-299-3p/VEGFA in cell proliferation, motility, invasion, and tube formation was analyzed in vitro.

RESULTS

High VEGFA expression was significantly associated with tumor stage, grade, distant metastasis and cancer-related death and correlated with poor progression-free and cancer-specific survival. VEGFA knockdown repressed proliferation, migration, invasion and angiogenesis in UTUC cell lines. miR-299-3p significantly reduced VEGFA protein expression and miR-299-3p overexpression inhibited VEGFA mRNA and protein expression by directly targeting its 3'-UTR. Functional studies indicated that VEGFA overexpression reversed the miR-299-3p-mediated suppression of tumor cell proliferation, migration, invasion and angiogenesis. In addition, miR-299-3p/VEGFA suppressed cellular functions in UTUC by modulating the expression of P18 and cyclin E2.

CONCLUSIONS

Our findings suggest that miR-299-3p possibly suppresses UTUC cell proliferation, motility, invasion and angiogenesis via VEGFA. VEGFA may act as a prognostic predictor, and both VEGFA and miR-299-3p could be potential therapeutic targets for UTUC.

Analysis of RNA Interference Targeted Against Human Antigen R (HuR) to Reduce Vascular Endothelial Growth Factor (VEGF) Protein Expression in Human Retinal Pigment Epithelial Cells

VEGF-A or vascular endothelial growth factor-A is an important factor in enabling neovascularization and angiogenesis. VEGF-A is regulated transcriptionally as well as post transcriptionally. Human antigen R (HuR) belonging to the embryonic lethal abnormal vision (ELAV) family is a key regulator promoting stabilization of VEGF-A mRNA. In this research we investigate, whether HuR targeted RNA interference would enable the reduction of the VEGF-A protein in human retinal pigment epithelial cells (ARPE-19) in-vitro, in normoxic conditions. Three siRNA molecules with sequences complementary to three regions of the HuR mRNA were designed. The three designed siRNA molecules were individually transfected in ARPE-19 cells using Lipofectamine™2000 reagent. Post-transfection (24 h, 48 h, 72 h), downregulation of HuR mRNA was estimated by real-time polymerase reaction, while HuR protein and VEGF-A protein levels were semi-quantitatively determined by western blotting techniques. VEGF-A protein levels were additionally quantified using ELISA techniques. All experiments were done in triplicate. The designed siRNA could successfully downregulate HuR mRNA with concomitant decreases in HuR and VEGF-A protein. The study reveals that HuR downregulation can prominently downregulate VEGF-A, making the protein a target for therapy against pathological angiogenesis conditions such as diabetic retinopathy.

Non-coding RNA regulatory networks in post-transcriptional regulation of VEGFA in cancer

The switch from the normal quiescent vasculature to angiogenesis in tumors is induced by a variety of growth factors, released from cancer and stromal cells upon oxygen and nutrients deprivation. Vascular endothelial growth factor A (VEGF-A) is a potent-secreted mitogen and the only growth factor specific to endothelial cells that is observed almost ubiquitously at sites of angiogenesis. Expression of VEGF-A in cancer cells is controlled through transcriptional and post-transcriptional mechanisms. Post-transcriptional regulation of VEGF-A occurs at multiple levels, through the control of splicing, mRNA stability and translation rate, enabling a fine-tuned expression and release of VEGF-A. Mounting evidence is highlighting the important role played by microRNAs (miRNAs) in the control of VEGF-A mRNA stability and translation in cancer. Moreover, non-coding RNAs, as long non-coding RNAs and circular RNAs, are emerging as crucial modulators of VEGF-A-targeting miRNAs, with consequent ability to modulate VEGF-A expression. This review discusses the recent progress on the ncRNA-related networks controlling VEGF-A expression in cancer cells and provides insights into the complexity of VEGF-A post-transcriptional regulation.

Studying molecular signaling in major angiogenic diseases

The growth of blood vessels from already existing vasculature is angiogenesis and it is one of the fundamental processes in fetal development, tissue damage or repair, and the reproductive cycle. In a healthy person, angiogenesis is regulated by the balance between pro- and anti-angiogenic factors. However, when the balance is disturbed, it results in various diseases or disorders. The angiogenesis pathway is a sequential cascade and differs based on the stimuli. Therefore, targeting one of the factors involved in the process can help us find a therapeutic strategy to treat irregular angiogenesis. In the past three decades of cancer research, angiogenesis has been at its peak, where an anti-angiogenic agent inhibiting vascular endothelial growth factor acts as a promising substance to treat cancer. In addition, cancer can be assessed based on the expression of angiogenic factors and its response to therapies. Angiogenesis is important for all tissues, which might be normal or pathologically changed and occur through ages. In clinical therapeutics, target therapy focusing on discovery of novel anti-angiogenic agents like bevacizumab, cetuximab, sunitinib, imatinib, lenvatinib, thalidomide, everolimus etc., to block or inhibit the angiogenesis pathway is well explored in recent times. In this review, we will discuss about the molecular signaling pathways involved in major angiogenic diseases in detail.

Pathophysiological Role of Genetic Factors Associated With Gestational Diabetes Mellitus

Gestational Diabetes Mellitus (GDM) is a highly prevalent maternal pathology characterized by maternal glucose intolerance during pregnancy that is, associated with severe complications for both mother and offspring. Several risk factors have been related to GDM; one of the most important among them is genetic predisposition. Numerous single nucleotide polymorphisms (SNPs) in genes that act at different levels on various tissues, could cause changes in the expression levels and activity of proteins, which result in glucose and insulin metabolism dysfunction. In this review, we describe various SNPs; which according to literature, increase the risk of developing GDM. These SNPs include: (1) those associated with transcription factors that regulate insulin production and excretion, such as rs7903146 (TCF7L2) and rs5015480 (HHEX); (2) others that cause a decrease in protective hormones against insulin resistance such as rs2241766 (ADIPOQ) and rs6257 (SHBG); (3) SNPs that cause modifications in membrane proteins, generating dysfunction in insulin signaling or cell transport in the case of rs5443 (GNB3) and rs2237892 (KCNQ1); (4) those associated with enzymes such as rs225014 (DIO2) and rs9939609 (FTO) which cause an impaired metabolism, resulting in an insulin resistance state; and (5) other polymorphisms, those are associated with growth factors such as rs2146323 (VEGFA) and rs755622 (MIF) which could cause changes in the expression levels of these proteins, producing endothelial dysfunction and an increase of pro-inflammatory cytokines, characteristic on GDM. While the pathophysiological mechanism is unclear, this review describes various potential effects of these polymorphisms on the predisposition to develop GDM.

VEGFR1 signaling in retinal angiogenesis and microinflammation

Five vascular endothelial growth factor receptor (VEGFR) ligands (VEGF-A, -B, -C, -D, and placental growth factor [PlGF]) constitute the VEGF family. VEGF-A binds VEGF receptors 1 and 2 (VEGFR1/2), whereas VEGF-B and PlGF only bind VEGFR1. Although much research has been conducted on VEGFR2 to elucidate its key role in retinal diseases, recent efforts have shown the importance and involvement of VEGFR1 and its family of ligands in angiogenesis, vascular permeability, and microinflammatory cascades within the retina. Expression of VEGFR1 depends on the microenvironment, is differentially regulated under hypoxic and inflammatory conditions, and it has been detected in retinal and choroidal endothelial cells, pericytes, retinal and choroidal mononuclear phagocytes (including microglia), Müller cells, photoreceptor cells, and the retinal pigment epithelium. Whilst the VEGF-A decoy function of VEGFR1 is well established, consequences of its direct signaling are less clear. VEGFR1 activation can affect vascular permeability and induce macrophage and microglia production of proinflammatory and proangiogenic mediators. However the ability of the VEGFR1 ligands (VEGF-A, PlGF, and VEGF-B) to compete against each other for receptor binding and to heterodimerize complicates our understanding of the relative contribution of VEGFR1 signaling alone toward the pathologic processes seen in diabetic retinopathy, retinal vascular occlusions, retinopathy of prematurity, and age-related macular degeneration. Clinically, anti-VEGF drugs have proven transformational in these pathologies and their impact on modulation of VEGFR1 signaling is still an opportunity-rich field for further research.

CELF1 promotes vascular endothelial growth factor degradation resulting in impaired microvasculature in heart failure

Vascular rarefaction due to impaired angiogenesis is associated with contractile dysfunction and the transition from compensation to decompensation and heart failure. The regulatory mechanism controlling vascular rarefaction during the transition remains elusive. Increased expression of a nuclear RNA-binding protein CUGBP Elav-like family member 1 (CELF1) in the adult heart is associated with the transition from compensated hypertrophy to decompensated heart failure. Elevated CELF1 level resulted in degradation of the major cardiac gap junction protein, connexin 43, in dilated cardiomyopathy (DCM), the most common cause of heart failure. In the present study, we investigated the role of increased CELF1 expression in causing vascular rarefaction in DCM. CELF1 overexpression (CELF1-OE) in cardiomyocytes resulted in reduced capillary density. CELF1-OE mice administered hypoxyprobe showed immunoreactivity and increased mRNA levels of HIF1α, Glut-1, and Pdk-1, which suggested the association of a reduced capillary density-induced hypoxic condition with CELF1 overexpression. Vegfa mRNA level was downregulated in mouse hearts exhibiting DCM, including CELF1-OE and infarcted hearts. Vegfa mRNA level was also downregulated to a similar extent in cardiomyocytes isolated from infarcted hearts by Langendorff preparation, which suggested cardiomyocyte-derived Vegfa expression mediated by CELF1. Cardiomyocyte-specific depletion of CELF1 preserved the capillary density and Vegfa mRNA level in infarcted mouse hearts. Also, CELF1 bound to Vegfa mRNA and regulated Vegfa mRNA stability via the 3' untranslated region. These results suggest that elevated CELF1 level has dual effects on impairing the functions of cardiomyocytes and microvasculature in DCM.

Ovarian tissue damage after grafting: systematic review of strategies to improve follicle outcomes

Frozen-thawed human ovarian tissue endures large-scale follicle loss in the early post-grafting period, characterized by hypoxia lasting around 7 days. Tissue revascularization occurs progressively through new vessel invasion from the host and neoangiogenesis from the graft. Such reoxygenation kinetics lead to further potential damage caused by oxidative stress. The aim of the present manuscript is to provide a systematic review of proangiogenic growth factors, hormones and various antioxidants administered in the event of ovarian tissue transplantation to protect the follicle pool from depletion by boosting revascularization or decreasing oxidative stress. Although almost all investigated studies revealed an advantage in terms of revascularization and reduction in oxidative stress, far fewer demonstrated a positive impact on follicle survival. As the cascade of events driven by ischaemia after transplantation is a complex process involving numerous players, it appears that acting on specific molecular mechanisms, such as concentrations of proangiogenic growth factors, is not enough to significantly mitigate tissue damage. Strategies exploiting the activated tissue response to ischaemia for tissue healing and remodelling purposes, such as the use of antiapoptotic drugs and adult stem cells, are also discussed in the present review, since they yielded promising results in terms of follicle pool protection.

Interplay within tumor microenvironment orchestrates neoplastic RNA metabolism and transcriptome diversity

The heterogeneous population of cancer cells within a tumor mass interacts intricately with the multifaceted aspects of the surrounding microenvironment. The reciprocal crosstalk between cancer cells and the tumor microenvironment (TME) shapes the cancer pathophysiome in a way that renders it uniquely suited for immune tolerance, angiogenesis, metastasis, and therapy resistance. This dynamic interaction involves a dramatic reconstruction of the transcriptomic landscape of tumors by altering the synthesis, modifications, stability, and processing of gene readouts. In this review, we categorically evaluate the influence of TME components, encompassing a myriad of resident and infiltrating cells, signaling molecules, extracellular vesicles, extracellular matrix, and blood vessels, in orchestrating the cancer-specific metabolism and diversity of both mRNA and noncoding RNA, including micro RNA, long noncoding RNA, circular RNA among others. We also highlight the transcriptomic adaptations in response to the physicochemical idiosyncrasies of TME, which include tumor hypoxia, extracellular acidosis, and osmotic stress. Finally, we provide a nuanced analysis of existing and prospective therapeutics targeting TME to ameliorate cancer-associated RNA metabolism, consequently thwarting the cancer progression. This article is categorized under: RNA Processing > Splicing Regulation/Alternative Splicing RNA Turnover and Surveillance > Regulation of RNA Stability RNA in Disease and Development > RNA in Disease.

Discrepancies on the Role of Oxygen Gradient and Culture Condition on Mesenchymal Stem Cell Fate

Over the past few years, mesenchymal stem (or stromal) cells (MSCs) have garnered enormous interest due to their therapeutic value especially for their multilineage differentiation potential leading to regenerative medicine applications. MSCs undergo physiological changes upon in vitro expansion resulting in expression of different receptors, thereby inducing high variabilities in therapeutic efficacy. Therefore, understanding the biochemical cues that influence the native local signals on differentiation or proliferation of these cells is very important. There have been several reports that in vitro culture of MSCs in low oxygen gradient (or hypoxic conditions) upregulates the stemness markers and promotes cell proliferation in an undifferentiated state, as hypoxia mimics the conditions the progenitor cells experience within the tissue. However, different studies report different oxygen gradients and culture conditions causing ambiguity in their interpretation of the results. In this progress report, it is aimed to summarize recent studies in the field with specific focus on conflicting results reported during the application of hypoxic conditions for improving the proliferation or differentiation of MSCs. Further, it is tried to decipher the factors that can affect characteristics of MSC under hypoxia and suggest a few techniques that could be combined with hypoxic cell culture to better recapitulate the MSC tissue niche.

Human antigen R protein modulates vascular endothelial growth factor expression in human corneal epithelial cells under hypoxia

PURPOSE

Corneal avascularity is critical for corneal transparency; therefore, a tailored process has been presumed to minimize corneal neovascularization (NV). In most cell types, the transcription of vascular endothelial growth factor (VEGF) is up-regulated, and the stability of VEGF mRNA is sustained by human antigen R (HuR) during hypoxia; however, whether such response applies to corneal epithelial cells is unclear.

METHODS

Human corneal epithelial cells (HCECs) and MCF-7 cells that serves as the control were incubated under 0.5% oxygen, and the levels of VEGF and HuR were examined time-dependently. The alteration of HuR was also examined in vivo using the closed-eye contact lens-induced corneal neovascularization rabbit model and immunohistochemistry. Additionally, the expression of HuR was modulated by transfection of plasmids encoding HuR or siRNA targeting HuR to validate the role of HuR in VEGF expression.

RESULTS

We found that, unlike in control cells, the level of VEGF was not up-regulated, and the HuR expression was declined in HCECs following hypoxia. The HuR immunostaining intensities were decreased in corneal epithelial cells of rabbits wearing contact lenses. In addition, HuR overexpression restored the ability of HCECs to up-regulate VEGF under hypoxia; however, knockdown of HuR suppressed hypoxia-induced VEGF in control cells but did not further decrease VEGF in HCECs. These findings suggest that HCECs may modulate HuR to suppress hypoxia-mediated up-regulation of VEGF.

CONCLUSION

Our study revealed a distinct regulation of VEGF via HuR in HCECs following hypoxia, which likely contributes to minimizing corneal NV and/or maintenance of corneal avascularity.

Hypoxic stabilization of mRNA is HIF-independent but requires mtROS

Background

Tissue ischemia can arise in response to numerous physiologic and pathologic conditions. The cellular response to decreased perfusion, most notably a decrease in glucose and oxygen, is important for cellular survival. In response to oxygen deprivation or hypoxia, one of the key response elements is hypoxia inducible factor (HIF) and a key protein induced by hypoxia is vascular endothelial growth factor (VEGF). Under hypoxia, we and others have reported an increase in the half-life of VEGF and other hypoxia related mRNAs including MYC and CYR61; however, the mediator of this response has yet to be identified. For this study, we sought to determine if HIF-mediated transcriptional activity is involved in the mRNA stabilization induced by hypoxia.

Methods

HEK293T or C6 cells were cultured in either normoxic or hypoxic (1% oxygen) conditions in the presence of 1 g/L glucose for all experiments. Pharmacological treatments were used to mimic hypoxia (desferroxamine, dimethyloxaloglutamate, CoCl₂), inhibit mitochondrial respiration (rotenone, myxothiazol), scavenge reactive oxygen species (ROS; ebselen), or generate mitochondrial ROS (antimycin A). siRNAs were used to knock down components of the HIF transcriptional apparatus. mRNA half-life was determined via actinomycin D decay and real time PCR and western blotting was used to determine mRNA and protein levels respectively.

Results

Treatment of HEK293T or C6 cells with hypoxic mimetics, desferroxamine, dimethyloxaloglutamate, or CoCl₂ showed similar induction of HIF compared to hypoxia treatment, however, in contrast to hypoxia, the mimetics caused no significant increase in VEGF, MYC or CYR61 mRNA half-life. Knockdown of HIF-alpha or ARNT via siRNA also had no effect on hypoxic mRNA stabilization. Interestingly, treatment of HEK293T cells with the mitochondrial inhibitors rotenone and myxothiazol, or the glutathione peroxidase mimetic ebselen did prevent the hypoxic stabilization of VEGF, MYC, and CYR61, suggesting a role for mtROS in the process. Additionally, treatment with antimycin A, which has been shown to generate mtROS, was able to drive the normoxic stabilization of these mRNAs.

Conclusion

Overall these data suggest that hypoxic mRNA stabilization is independent of HIF transcriptional activity but requires mtROS.

The role of miR-106p-5p in cervical cancer: from expression to molecular mechanism

This study aims to investigate the role of miR-106b-5p in cervical cancer by performing a comprehensive analysis on its expression and identifying its putative molecular targets and pathways based on The Cancer Genome Atlas (TCGA) dataset, Gene Expression Omnibus (GEO) dataset, and literature review. Significant upregulation of miR-106b-5p in cervical cancer is confirmed by meta-analysis with the data from TCGA, GEO, and literature. Moreover, the expression of miR-106b-5p is significantly correlated with the number of metastatic lymph nodes. Our bioinformatics analyses show that miR-106b could promote cervical cancer progression by modulating the expression of GSK3B, VEGFA, and PTK2 genes. Importantly, these three genes play a crucial role in PI3K-Akt signaling, focal adhesion, and cancer. Both the expression of miR-106b-5p and key genes are upregulated in cervical cancer. Several explanations could be implemented for this upregulation. However, the specific mechanism needs to be investigated further.

Angiogenic factors: role in esophageal cancer, a brief review

Esophageal cancer has an aggressive behavior with rapid tumor mass growth and frequently poor prognosis; it is known as one of the most fatal types of cancer worldwide. The identification of potential molecular markers that can predict the response to treatment and the prognosis of this cancer has been subject of a vast investigation in the recent years. Among several molecules, various angiogenic factors that are linked to the tumor development, growth, and invasion, such as VEGF, HGF, angiopoietin-2, IL-6, and TGF-B1, were investigated. In this paper, the authors sought to review the role of these angiogenic factors in prognosis and hypothesize how they can be used as a treatment target.

Nuclear factor 90 promotes angiogenesis by regulating HIF-1α/VEGF-A expression through the PI3K/Akt signaling pathway in human cervical cancer

Vascular endothelial growth factor A (VEGF-A), a fundamental component of angiogenesis, provides nutrients and oxygen to solid tumors, and enhances tumor cell survival, invasion, and migration. Nuclear factor 90 (NF90), a double-stranded RNA-binding protein, is strongly expressed in several human cancers, promotes tumor growth by reducing apoptosis, and increasing cell cycle process. The mechanisms by which cervical cancer cells inducing VEGF-A expression and angiogenesis upon NF90 upregulation remain to be fully established. We demonstrated that NF90 is upregulated in human cervical cancer specimens and the expression of NF90 is paralleled with that of VEGF-A under hypoxia. The expressions of hypoxia inducible factor-1α (HIF-1α) and VEGF-A are downregulated upon NF90 knockdown, which can be rescued by ectopic expression of NF90. Suppression of NF90 decreases the tube formation and cell migration of HUVECs. Moreover, the PI3K/Akt signaling pathway participates in the regulation. Knockdown of NF90 also reduces the tumor growth and angiogenesis of cervical cancer cell line in the mouse xenograft model. Taken together, suppression of NF90 in cervical cancer cell lines can decrease VEGF-A expression, inhibit angiogenesis, and reduce tumorigenic capacity in vivo.

A gapmer aptamer nanobiosensor for real-time monitoring of transcription and translation in single cells

Transcription and translation are under tight spatiotemporal regulation among cells to coordinate multicellular organization. Methods that allow massively parallel detection of gene expression dynamics at the single cell level are required for elucidating the complex regulatory mechanisms. Here we present a multiplex nanobiosensor for real-time monitoring of protein and mRNA expression dynamics in live cells based on gapmer aptamers and complementary locked nucleic acid probes. Using the multiplex nanobiosensor, we quantified spatiotemporal dynamics of vascular endothelial growth factor A mRNA and protein expressions in single human endothelial cells during microvascular self-organization. Our results revealed distinct gene regulatory processes in the heterogeneous cell subpopulations.

Characterization of neural stem cells modified with hypoxia/neuron-specific VEGF expression system for spinal cord injury

Spinal cord injury (SCI) is an incurable disease causing an ischemic environment and functional defect, thus a new therapeutic approach is needed for SCI treatment. Vascular endothelial growth factor (VEGF) is a potent therapeutic gene to treat SCI via angiogenesis and neuroprotection, and both tissue-specific gene expression and high gene delivery efficiency are important for successful gene therapy. Here we design the hypoxia/neuron dual-specific gene expression system (pEpo-NSE) and efficient gene delivery platform can be achieved by the combination ex vivo gene therapy with erythropoietin (Epo) enhancer, neuron-specific enolase (NSE) promoter and neural stem cells (NSCs). An in vitro model, NSCs transfected with pEpo-NSE were consistently and selectively overexpressing therapeutic genes in response to neural differentiation and hypoxic conditions. Also, in SCI model, ex vivo gene therapy using pEpo-NSE system with NSCs significantly enhanced gene delivery efficiency compared with pEpo-NSE system gene therapy alone. However, microarray analysis reveals that introducing exogenous pEpo-NSE and VEGF triggers biological pathways in NSCs such as glycolysis and signaling pathways such as Ras and mitogen-activated protein kinase, leading to cell proliferation, differentiation and apoptosis. Collectively, it indicates that the pEpo-NSE gene expression system works stably in NSCs and ex vivo gene therapy using pEpo-NSE system with NSCs improves gene expression efficiency. However, exogenously introduced pEpo-NSE system has an influence on gene expression profiles in NSCs. Therefore, when we consider ex vivo gene therapy for SCI, the effects of changes in gene expression profiles in NSCs on safety should be investigated.

N6-methyladenosine is required for the hypoxic stabilization of specific mRNAs

Post-transcriptional regulation of mRNA during oxygen deprivation, or hypoxia, can affect the survivability of cells. Hypoxia has been shown to increase stability of a subset of ischemia-related mRNAs, including VEGF. RNA binding proteins and miRNAs have been identified as important for post-transcriptional regulation of individual mRNAs, but corresponding mechanisms that regulate global stability are not well understood. Recently, mRNA modification by N⁶-methyladenosine (m⁶A) has been shown to be involved in post-transcriptional regulation processes including mRNA stability and promotion of translation, but the role of m⁶A in the hypoxia response is unknown. In this study, we investigate the effect of hypoxia on RNA modifications including m⁶A. Our results show hypoxia increases m⁶A content of poly(A)⁺ messenger RNA (mRNA), but not in total or ribosomal RNA in HEK293T cells. Using m⁶A mRNA immunoprecipitation, we identify specific hypoxia-modified mRNAs, including glucose transporter 1 (Glut1) and c-Myc, which show increased m⁶A levels under hypoxic conditions. Many of these mRNAs also exhibit increased stability, which was blocked by knockdown of m⁶A-specific methyltransferases METTL3/14. However, the increase in mRNA stability did not correlate with a change in translational efficiency or the steady-state amount of their proteins. Knockdown of METTL3/14 did reveal that m⁶A is involved in recovery of translational efficiency after hypoxic stress. Therefore, our results suggest that an increase in m⁶A mRNA during hypoxic exposure leads to post-transcriptional stabilization of specific mRNAs and contributes to the recovery of translational efficiency after hypoxic stress.

Hypoxia and Hypoglycemia synergistically regulate mRNA stability

Ischemic events, common in many diseases, result from decreased blood flow and impaired delivery of oxygen and glucose to tissues of the body. While much is known about the cellular transcriptional response to ischemia, much less is known about the posttranscriptional response to oxygen and glucose deprivation. The goal of this project was to investigate one such posttranscriptional response, the regulation of mRNA stability. To that end, we have identified several novel ischemia-related mRNAs that are synergistically stabilized by oxygen and glucose deprivation including VEGF, MYC, MDM2, and CYR61. This increase in mRNA half-life requires the synergistic effects of both low oxygen (1%) as well as low glucose (≤ 1 g/L) conditions. Oxygen or glucose deprivation alone fails to initiate the response, as exposure to either high glucose (4 g/L) or normoxic conditions inhibits the response. Furthermore, in response to hypoxia/hypoglycemia, the identified mRNAs are released from the RNA binding protein KHSRP which likely contributes to their stabilization.

Anti-cancer effect of R3V6 peptide-mediated delivery of an anti-microRNA-21 antisense-oligodeoxynucleotide in a glioblastoma animal model

MicroRNA-21 (miR-21) expression in glioblastoma inhibits the expression of pro-apoptotic genes, thereby promoting tumor growth. A previous study showed that the amphiphilic R3V6 peptide is an efficient carrier of the anti-miR-21 antisense oligodeoxynucleotide (antisense-ODN) into cells in vitro. In the current study, in vivo delivery of antisense-ODN using the R3V6 peptide was evaluated in a glioblastoma animal model. In vitro transfection showed that the R3V6 peptide delivered antisense-ODN more efficiently than polyethylenimine (25 kDa, PEI25k) in C6 glioblastoma cells. For in vivo evaluation, antisense-ODN/R3V6 complex was injected intratumorally into a C6 glioblastoma xenograft animal model. Tumor growth was suppressed by the injection of the antisense-ODN/R3V6 complex, compared with the antisense-ODN/PEI25k and scrambled-antisense-ODN (scr-antisense-ODN)/R3V6 complexes. Real-time RT-PCR showed that miR-21 levels were reduced most efficiently by the antisense-ODNR3V6 complex in tumors. Due to inhibition of miR-21, expression of the programed cell death 4 (PDCD4) gene was promoted in tumors, resulting in the induction of apoptosis of tumor cells. These results suggest that delivery of antisense-ODN using R3V6 peptides may be useful for the development of antisense-ODN therapy for glioblastoma.

Inverse Correlation between IL-10 and HIF-1α in Macrophages Infected with Histoplasma capsulatum

Hypoxia-inducible factor (HIF)-1α is a transcription factor that regulates metabolic and immune response genes in the setting of low oxygen tension and inflammation. We investigated the function of HIF-1α in the host response to Histoplasma capsulatum because granulomas induced by this pathogenic fungus develop hypoxic microenvironments during the early adaptive immune response. In this study, we demonstrated that myeloid HIF-1α-deficient mice exhibited elevated fungal burden during the innate immune response (prior to 7 d postinfection) as well as decreased survival in response to a sublethal inoculum of H. capsulatum The absence of myeloid HIF-1α did not alter immune cell recruitment to the lungs of infected animals but was associated with an elevation of the anti-inflammatory cytokine IL-10. Treatment with mAb to IL-10 restored protective immunity to the mutant mice. Macrophages (Mϕs) constituted most IL-10-producing cells. Deletion of HIF-1α in neutrophils or dendritic cells did not alter fungal burden, thus implicating Mϕs as the pivotal cell in host resistance. HIF-1α was stabilized in Mϕs following infection. Increased activity of the transcription factor CREB in HIF-1α-deficient Mϕs drove IL-10 production in response to H. capsulatum IL-10 inhibited Mϕ control of fungal growth in response to the activating cytokine IFN-γ. Thus, we identified a critical function for Mϕ HIF-1α in tempering IL-10 production following infection. We established that transcriptional regulation of IL-10 by HIF-1α and CREB is critical for activation of Mϕs by IFN-γ and effective handling of H. capsulatum.

The Small Molecule R-(-)-β-O-Methylsynephrine Binds to Nucleoporin 153 kDa and Inhibits Angiogenesis

R-(-)-β-O-methylsynephrine (OMe-Syn) is a naturally occurring small molecule that was identified in a previous screen as an inhibitor of angiogenesis. In this study, we conducted two animal model experiments to investigate the in vivo antiangiogenic activity of OMe-Syn. OMe-Syn significantly inhibited angiogenesis in a transgenic zebrafish model as well as in a mouse retinopathy model. To elucidate the underlying mechanisms responsible for the antiangiogenic activity of OMe-Syn, we used phage display cloning to isolate potential OMe-Syn binding proteins from human cDNA libraries and identified nucleoporin 153 kDa (NUP153) as a primary binding partner of OMe-Syn. OMe-Syn competitively inhibited mRNA binding to the RNA-binding domain of NUP153. Furthermore, depletion of NUP153 in human cells or zebrafish embryos led to an inhibition of angiogenesis, in a manner similar to that seen in response to OMe-Syn treatment. These data suggest that OMe-Syn is a promising candidate for the development of a novel antiangiogenic agent and that inhibition of NUP153 is possibly responsible for the antiangiogenic activity of OMe-Syn.

Regulation of vascular endothelial growth factor in prostate cancer

Prostate cancer (PCa) is the most common malignancy affecting men in the western world. Although radical prostatectomy and radiation therapy can successfully treat PCa in the majority of patients, up to ~30% will experience local recurrence or metastatic disease. Prostate carcinogenesis and progression is typically an androgen-dependent process. For this reason, therapies for recurrent PCa target androgen biosynthesis and androgen receptor function. Such androgen deprivation therapies (ADT) are effective initially, but the duration of response is typically ≤24 months. Although ADT and taxane-based chemotherapy have delivered survival benefits, metastatic PCa remains incurable. Therefore, it is essential to establish the cellular and molecular mechanisms that enable localized PCas to invade and disseminate. It has long been accepted that metastases require angiogenesis. In the present review, we examine the essential role for angiogenesis in PCa metastases, and we focus in particular on the current understanding of the regulation of vascular endothelial growth factor (VEGF) in localized and metastatic PCa. We highlight recent advances in understanding the role of VEGF in regulating the interaction of cancer cells with tumor-associated immune cells during the metastatic process of PCa. We summarize the established mechanisms of transcriptional and post-transcriptional regulation of VEGF in PCa cells and outline the molecular insights obtained from preclinical animal models of PCa. Finally, we summarize the current state of anti-angiogenesis therapies for PCa and consider how existing therapies impact VEGF signaling.

Human bone marrow-derived mesenchymal stem cells display enhanced clonogenicity but impaired differentiation with hypoxic preconditioning

Stem cells are promising candidate cells for regenerative applications because they possess high proliferative capacity and the potential to differentiate into other cell types. Mesenchymal stem cells (MSCs) are easily sourced but do not retain their proliferative and multilineage differentiative capabilities after prolonged ex vivo propagation. We investigated the use of hypoxia as a preconditioning agent and in differentiating cultures to enhance MSC function. Culture in 5% ambient O(2) consistently enhanced clonogenic potential of primary MSCs from all donors tested. We determined that enhanced clonogenicity was attributable to increased proliferation, increased vascular endothelial growth factor secretion, and increased matrix turnover. Hypoxia did not impact the incidence of cell death. Application of hypoxia to osteogenic cultures resulted in enhanced total mineral deposition, although this effect was detected only in MSCs preconditioned in normoxic conditions. Osteogenesis-associated genes were upregulated in hypoxia, and alkaline phosphatase activity was enhanced. Adipogenic differentiation was inhibited by exposure to hypoxia during differentiation. Chondrogenesis in three-dimensional pellet cultures was inhibited by preconditioning with hypoxia. However, in cultures expanded under normoxia, hypoxia applied during subsequent pellet culture enhanced chondrogenesis. Whereas hypoxic preconditioning appears to be an excellent way to expand a highly clonogenic progenitor pool, our findings suggest that it may blunt the differentiation potential of MSCs, compromising their utility for regenerative tissue engineering. Exposure to hypoxia during differentiation (post-normoxic expansion), however, appears to result in a greater quantity of functional osteoblasts and chondrocytes and ultimately a larger quantity of high-quality differentiated tissue.

Nano-nutrition of chicken embryos. The effect of in ovo administration of diamond nanoparticles and L-glutamine on molecular responses in chicken embryo pectoral muscles

It has been demonstrated that the content of certain amino acids in eggs is not sufficient to fully support embryonic development. One possibility to supply the embryo with extra nutrients and energy is in ovo administration of nutrients. Nanoparticles of diamond are highly biocompatible non-toxic carbonic structures, and we hypothesized that bio-complexes of diamond nanoparticles with l-glutamine may affect molecular responses in breast muscle. The objective of the investigation was to evaluate the effect of diamond nanoparticle (ND) and l-glutamine (Gln) on expression of growth and differentiation factors of chicken embryo pectoral muscles. ND, Gln, and Gln/ND solutions (50 mg/L) were injected into fertilized broiler chicken eggs at the beginning of embryogenesis. Muscle tissue was dissected at day 20 of incubation and analysed for gene expression of FGF2, VEGF-A, and MyoD1. ND and especially Gln/ND up-regulated expression of genes related to muscle cell proliferation (FGF2) and differentiation (MyoD1). Furthermore, the ratio between FGF2 and MyoD1 was highest in the Gln/ND group. At the end of embryogenesis, Gln/ND enhanced both proliferation and differentiation of pectoral muscle cells and differentiation dominated over proliferation. These preliminary results suggest that the bio-complex of glutamine and diamond nanoparticles may accelerate growth and maturation of muscle cells.

Post-transcriptional regulatory networks in immunity

Post-transcriptional mechanisms that modulate global and/or transcript-specific mRNA stability and translation contribute to the rapid and flexible control of gene expression in immune effector cells. These mechanisms rely on RNA-binding proteins (RBPs) that direct regulatory complexes (e.g. exosomes, deadenylases, decapping complexes, RNA-induced silencing complexes) to the 3'-untranslated regions of specific immune transcripts. Here, we review the surprising variety of post-transcriptional control mechanisms that contribute to gene expression in the immune system and discuss how defects in these pathways can contribute to autoimmune disease.

VEGF-A mRNA processing, stability and translation: a paradigm for intricate regulation of gene expression at the post-transcriptional level

Vascular Endothelial Growth Factor A (VEGF-A) is a potent secreted mitogen crucial for physiological and pathological angiogenesis. Post-transcriptional regulation of VEGF-A occurs at multiple levels. Firstly, alternative splicing gives rise to different transcript variants encoding diverse isoforms that exhibit distinct biological properties with regard to receptor binding and extra-cellular localization. Secondly, VEGF-A mRNA stability is regulated by effectors such as hypoxia or growth factors through the binding of stabilizing and destabilizing proteins at AU-rich elements located in the 3′-untranslated region. Thirdly, translation of VEGF-A mRNA is a controlled process involving alternative initiation codons, internal ribosome entry sites (IRESs), an upstream open reading frame (uORF), miRNA targeting and a riboswitch in the 3′ untranslated region. These different levels of regulation cooperate for the crucial fine-tuning of the expression of VEGF-A variants. This review will be focused on our current knowledge of the complex post-transcriptional regulatory switches that modulate the cellular VEGF-A level, a paradigmatic model of post-transcriptional regulation.

Identification of DEAD-box RNA helicase 6 (DDX6) as a cellular modulator of vascular endothelial growth factor expression under hypoxia

Vascular endothelial growth factor A (VEGF) is a crucial proangiogenic factor, which regulates blood vessel supply under physiologic and pathologic conditions. The VEGF mRNA 5'-untranslated region (5'-UTR) bears internal ribosome entry sites (IRES), which confer sustained VEGF mRNA translation under hypoxia when 5'-cap-dependent mRNA translation is inhibited. VEGF IRES-mediated initiation of translation requires the modulated interaction of trans-acting factors. To identify trans-acting factors that control VEGF mRNA translation under hypoxic conditions we established an in vitro translation system based on human adenocarcinoma cells (MCF-7). Cytoplasmic extracts of MCF-7 cells grown under hypoxia (1% oxygen) recapitulate VEGF IRES-mediated reporter mRNA translation. Employing the VEGF mRNA 5'-UTR and 3'-UTR in an RNA affinity approach we isolated interacting proteins from translational active MCF-7 extract prepared from cells grown under normoxia or hypoxia. Interestingly, mass spectrometry analysis identified the DEAD-box RNA helicase 6 (DDX6) that interacts with the VEGF mRNA 5'-UTR. Recombinant DDX6 inhibits VEGF IRES-mediated translation in normoxic MCF-7 extract. Under hypoxia the level of DDX6 declines, and its interaction with VEGF mRNA is diminished in vivo. Depletion of DDX6 by RNAi further promotes VEGF expression in MCF-7 cells. Increased secretion of VEGF from DDX6 knockdown cells positively affects vascular tube formation of human umbilical vein endothelial cells (HUVEC) in vitro. Our results indicate that the decrease of DDX6 under hypoxia contributes to the activation of VEGF expression and promotes its proangiogenic function.

The expression levels of microRNA-361-5p and its target VEGFA are inversely correlated in human cutaneous squamous cell carcinoma

Vascular endothelial growth factor A (VEGFA) plays a key role in the angiogenesis of human skin. Elevated levels of VEGFA are associated with several pathological conditions, including chronic inflammatory skin diseases and several types of skin cancer. In particular, squamous cell carcinoma (SCC) of the skin, the second most common skin cancer in the general population, is characterized by invasive growth, pronounced angiogenesis and elevated levels of VEGFA. The processing, turnover and production of VEGFA are extensively regulated at the post-transcriptional level, both by RNA-binding proteins and microRNAs (miRNAs). In the present study, we identified a new miRNA recognition element in a downstream conserved region of the VEGFA 3'-UTR. We confirmed the repressive effect of miR-361-5p on this element in vitro, identifying the first target for this miRNA. Importantly, we found that miR-361-5p levels are inversely correlated with VEGFA expression in SCC and in healthy skin, indicating that miR-361-5p could play a role in cancers.

Post-transcriptional regulation of VEGF-A mRNA levels by mitogen-activated protein kinases (MAPKs) during metabolic stress associated with ischaemia/reperfusion

Angiogenesis is a well-characterised response to the metabolic stresses that occur during ischaemia/reperfusion, but the signalling pathways that regulate it are poorly understood. We tested whether activation of mitogen-activated protein kinases (MAPKs) was involved in regulating the expression of pro-angiogenic growth factors by the metabolic stresses associated with ischaemia/reperfusion in H9c2 rat cardiomyoblasts. Metabolic stress had no effect on vascular endothelial growth factor (VEGF) mRNA levels, but recovery after metabolic inhibition led to a strong induction of VEGF-A mRNA (3.8 ± 0.5-fold at 4 h), a modest rise in VEGF-C mRNA levels (1.7 ± 0.3-fold at 4 h), with no effect on VEGF-B or -D. A VEGF-A promoter reporter construct was unresponsive to metabolic inhibition/recovery and increases in VEGF-A mRNA were not blocked by the transcription inhibitor actinomycin D suggesting that increases in VEGF mRNA were due to enhanced VEGF-A mRNA stability. In addition, studies using reporter constructs demonstrated that regions within the 5' untranslated region (UTR) contributed to enhanced mRNA stability following recovery from metabolic stress. Increases in VEGF-A mRNA were abolished by inhibition of extracellular signal-regulated kinase or c-jun N-terminal kinase MAPKs, suggesting that these kinases may promote angiogenesis in response to metabolic stress during ischaemia/reperfusion by increasing VEGF-A message stability.

Networks controlling mRNA decay in the immune system

The active control of mRNA degradation has emerged as a key regulatory mechanism required for proper gene expression in the immune system. An adenosine/uridine (AU)-rich element (ARE) is at the heart of a first regulatory system that promotes the rapid degradation of a multitude of cytokine and chemokine mRNAs. AREs serve as binding sites for a number of regulatory proteins that either destabilize or stabilize the mRNA. Several kinase pathways regulate the activity of ARE-binding proteins and thereby coordinate the expression of their target mRNAs. Small regulatory micro (mi)-RNAs represent a second system that enhances the degradation of several mRNAs encoding important components of signal transduction cascades that are activated during adaptive and innate immune responses. Specific miRNAs are important for the differentiation of T helper cells, class switch recombination in B cells, and the maturation of dendritic cells. Excitement in this area of research is fueled by the discovery of novel RNA elements and regulatory proteins that exert control over specific mRNAs, as exemplified by an endonuclease that was found to directly cleave interleukin-6 mRNA. Together, these systems make up an extensive regulatory network that controls decay rates of individual mRNAs in a precise manner and thereby orchestrates the dynamic expression of many factors essential for adaptive and innate immune responses. In this review, we provide an overview of relevant factors regulated at the level of mRNA stability, summarize RNA-binding proteins and miRNAs that control their degradation rates, and discuss signaling pathways operating within this regulatory network.

hnRNP Q mediates a phase-dependent translation-coupled mRNA decay of mouse Period3

Daily mRNA oscillations of circadian clock genes largely depend on transcriptional regulation. However, several lines of evidence highlight the critical role of post-transcriptional regulation in the oscillations of circadian mRNA oscillations. Clearly, variations in the mRNA decay rate lead to changes in the cycling profiles. However, the mechanisms controlling the mRNA stability of clock genes are not fully understood. Here we demonstrate that the turnover rate of mouse Period3 (mPer3) mRNA is dramatically changed in a circadian phase-dependent manner. Furthermore, the circadian regulation of mPer3 mRNA stability requires the cooperative function of 5′- and 3′-untranslated regions (UTRs). Heterogeneous nuclear ribonucleoprotein Q (hnRNP Q) binds to both 5′- and 3′-UTR and triggers enhancement of translation and acceleration of mRNA decay. We propose the phase-dependent translation coupled mRNA decay mediated by hnRNP Q as a new regulatory mechanism of the rhythmically regulated decay of mPer3 mRNA.

NF90 binds the dengue virus RNA 3' terminus and is a positive regulator of dengue virus replication

Background

Viral RNA translation and replication are regulated by sequence and structural elements in the 5′ and 3′ untranslated regions (UTR) and by host cell and/or viral proteins that bind them. Dengue virus has a single-stranded RNA genome with positive polarity, a 5′ m7GpppG cap, and a conserved 3′-terminal stem loop (SL) that is linked to proposed functions in viral RNA transcription and translation. Mechanisms explaining the contributions of host proteins to viral RNA translation and replication are poorly defined, yet understanding host protein-viral RNA interactions may identify new targets for therapeutic intervention. This study was directed at identifying functionally significant host proteins that bind the conserved dengue virus RNA 3′ terminus.

Methodology/Principal Findings

Proteins eluted from a dengue 3′ SL RNA affinity column at increasing ionic strength included two with double-strand RNA binding motifs (NF90/DRBP76 and DEAH box polypeptide 9/RNA helicase A (RHA)), in addition to NF45, which forms a heterodimer with NF90. Although detectable NF90 and RHA proteins localized to the nucleus of uninfected cells, immunofluorescence revealed cytoplasmic NF90 in dengue virus-infected cells, leading us to hypothesize that NF90 has a functional role(s) in dengue infections. Cells depleted of NF90 were used to quantify viral RNA transcript levels and production of infectious dengue virus. NF90 depletion was accompanied by a 50%-70% decrease in dengue RNA levels and in production of infectious viral progeny.

Conclusions/Significance

The results indicate that NF90 interacts with the 3′ SL structure of the dengue RNA and is a positive regulator of dengue virus replication. NF90 depletion diminished the production of infectious dengue virus by more than 50%, which may have important significance for identifying therapeutic targets to limit a virus that threatens more than a billion people worldwide.

In vivo identification and specificity assessment of mRNA markers of hypoxia in human and mouse tumors

BACKGROUND

Tumor hypoxia is linked to poor prognosis, but identification and quantification of tissue hypoxia remains a challenge. The hypoxia-specificity of HIF-1α target genes in vivo has been questioned due to the confounding influence of other microenvironmental abnormalities known to affect gene expression (e.g., low pH). Here we describe a new technique that by exploiting intratumoral oxygenation heterogeneity allows us to identify and objectively rank the most robust mRNA hypoxia biomarkers.

METHODS

Mice carrying human (FaDudd) or murine (SCCVII) tumors were injected with the PET hypoxia tracer FAZA. Four hours post-injection tumors were removed, frozen, and crushed into milligram-sized fragments, which were transferred individually to pre-weighed tubes containing RNAlater and then weighed. For each fragment radioactivity per tissue mass and expression patterns of selected mRNA biomarkers were analyzed and compared.

RESULTS

In both tumour models, fragmentation into pieces weighing 10 to 60 mg resulted in tissue fragments with highly variable relative content of hypoxic cells as evidenced by an up to 13-fold variation in FAZA radioactivity per mass of tissue. Linear regression analysis comparing FAZA retention with patterns of gene expression in individual tissue fragments revealed that CA9, GLUT1 and LOX mRNA levels were equally and strongly correlated to hypoxic extent in FaDudd. The same link between hypoxia and gene expression profile was observed for CA9 and GLUT1, but not LOX, in SCCVII tumors. Apparent in vivo hypoxia-specificity for other putative molecular markers of tissue hypoxia was considerably weaker.

CONCLUSIONS

The portrayed technique allows multiple pairwise measurements of mRNA transcript levels and extent of hypoxia in individual tumors at a smallest possible volumetric scale which (by limiting averaging effects inherent to whole-tumor analysis) strengthen the conclusiveness on true hypoxia-specificity of candidate genes while limiting the required number of tumors. Among tested genes, our study identified CA9, GLUT1 and possibly LOX as highly specific biomarkers of tumor hypoxia in vivo.

Coding region: the neglected post-transcriptional code

The control of mammalian mRNA turnover and translation has been linked almost exclusively to specific cis-elements within the 5'- and 3'-untranslated regions (UTRs) of the mature mRNA. However, instances of regulated turnover and translation via cis-elements within the coding region (CR) of mRNAs are accumulating. Here, we describe the regulation of post-transcriptional fate through trans-binding factors (RNA-binding proteins and microRNAs) that function via CR sequences. We discuss how the CR enriches the post-transcriptional control of gene expression, and predict that new high-throughput technologies will enable a more mainstream study of CR-governed gene regulation.

Altered VEGF mRNA stability following treatments with immunosuppressive agents: implications for cancer development

The high incidence of cancer and its aggressive progression is a common and major problem in patients receiving immunosuppressive therapy. The calcineurin inhibitors (CNIs) may have protumorigenic effects and can promote the overexpression of several molecules inducing tumor growth. We have recently demonstrated that CNIs can mediate the transcriptional activation of the angiogenic cytokine vascular endothelial growth factor (VEGF) and promote a rapid progression of human renal cancer. Here, we investigated whether the CNI cyclosporine (CsA) and the mTOR inhibitor rapamycin (RAPA) could alter the mRNA stability of VEGF in 786-0 and Caki-1 renal cancer cells. Following actinomycin D treatment, we observed that CsA increased, whereas RAPA decreased the VEGF mRNA stability as observed by real time PCR. It is established that the mRNA-binding protein HuR may play a critical role in VEGF mRNA stability. By using HuR-siRNA, we found that the knockdown of HuR significantly decreased the CNI-induced VEGF mRNA stability. By Western blot analysis, it has been observed that CNI treatment induced the translocation of HuR from the nucleus to the cytoplasm; CNIs also induced the association between HuR and PKC-delta and promoted the phosphorylation of HuR. Finally, we found that the inhibition of PKC-delta using a dominant negative plasmid significantly decreased the CsA-induced cytoplasmic translocation of HuR and VEGF mRNA stability. Together, targeting the pathways that promote CNI-induced transcription as well as the mRNA stability of VEGF might serve as novel therapeutics for the prevention and treatment of cancer in immunosuppressed patients.

Role of the oxygen-dependent degradation domain in a hypoxia-inducible gene expression system in vascular endothelial growth factor gene therapy

STUDY DESIGN.: An in vitro neural hypoxia model and rat spinal cord injury (SCI) model were used to assess the regulation effect of a reporter or therapeutic gene expression by an oxygen-dependent degradation (ODD) domain in a hypoxia-inducible gene expression system with or without the erythropoietin (EPO) enhancer. OBJECTIVE.: To increase vascular endothelial growth factor (VEGF) gene expression in SCI lesions but avoid unwanted overexpression of VEGF in normal sites, we developed a hypoxia-inducible gene expression system consisting of the EPO enhancer upstream of the SV promoter and an ODD domain C-terminally fused to VEGF. SUMMARY OF BACKGROUND DATA.: ODD domain plays a major role in the degradation of hypoxia-inducible factor 1alpha and has been used in a hypoxia-specific gene expression system as a post-translational regulatory factor. METHODS.: The hypoxia-inducible luciferase or VEGF plasmid was constructed using the EPO enhancer combined with or without the ODD domain. The constructed plasmid was transfected into mouse Neuro 2a (N2a) neuroblastoma cells by Lipofectamine 2000, followed by a 24-hour incubation in hypoxia or normoxia. For in vivo analysis, the naked plasmid DNA was directly injected into the injured rat spinal cord. The gene expression was evaluated by luciferase activity assay, enzyme-linked immunosorbent assay, reverse transcriptase-polymerase chain reaction, and immunofluorescence staining. RESULTS.: The EPO enhancer/ODD domain-combined hypoxia-inducible gene expression system clearly increased the expression of the reporter luciferase gene and therapeutic VEGF gene specifically under hypoxic conditions and SCI, and quickly downregulated protein expression to a very low level after reoxygenation. CONCLUSION.: These results strongly suggest the potential applicability of this EPO enhancer/ODD domain-based hypoxia-inducible gene expression system in the development of a safer and more effective VEGF gene therapy for SCI.

Stabilization of XIAP mRNA through the RNA binding protein HuR regulated by cellular polyamines

The X chromosome-linked inhibitor of apoptosis protein (XIAP) is the most potent intrinsic caspase inhibitor and plays an important role in the maintenance of intestinal epithelial integrity. The RNA binding protein, HuR, regulates the stability and translation of many target transcripts. Here, we report that HuR associated with both the 3'-untranslated region and coding sequence of the mRNA encoding XIAP, stabilized the XIAP transcript and elevated its expression in intestinal epithelial cells. Ectopic HuR overexpression or elevated cytoplasmic levels of endogenous HuR by decreasing cellular polyamines increased [HuR/XIAP mRNA] complexes, in turn promoting XIAP mRNA stability and increasing XIAP protein abundance. Conversely, HuR silencing in normal and polyamine-deficient cells rendered the XIAP mRNA unstable, thus reducing the steady state levels of XIAP. Inhibition of XIAP expression by XIAP silencing or by HuR silencing reversed the resistance of polyamine-deficient cells to apoptosis. Our findings demonstrate that HuR regulates XIAP expression by stabilizing its mRNA and implicates HuR-mediated XIAP in the control of intestinal epithelial apoptosis.

Effect of polymorphisms in the 3' untranslated region (3'-UTR) of vascular endothelial growth factor gene on gastric cancer and peptic ulcer diseases in Japan

A complex interaction of host genetic and environmental factors may be relevant in the development of Helicocobacter pylori-related gastric carcinogenesis. We investigated the effect of vascular endothelial growth factor (VEGF) gene polymorphisms on the risk of gastric cancer (GC) and peptic ulcer diseases in a Japanese population. The G1612A(rs10434) and C936T(rs3025039) polymorphisms in the 3' untranslated region (3'-UTR) of VEGF gene were genotyped in a total of 844 subjects including 385 GC, 143 ulcer including 98 gastric ulcer (GU), 45 duodenal ulcer (DU), and 316 nonulcer subjects. The 1612A carrier held a significantly higher risk of GC when compared to both noncancer and nonulcer (overall noncancer vs. GC; OR = 1.61, 95% CI = 1.17-2.21, P = 0.0038, nonulcer vs. GC; OR = 1.54, 95% CI = 1.07-2.22, P = 0.0197). The 1612A carrier was more closely associated with an increased risk of noncardiac cancer (OR = 1.64, 95% CI = 0.17-2.21, P = 0.0038), lower third cancer (OR = 1.97, 95% CI = 1.30-3.00, P = 0.002), and Lauren's diffuse-type cancer (OR = 1.75, 95% CI = 1.24-2.46, P = 0.001), while the same genotype was not associated with the progression of GC. The C936T genotype was not associated with a risk of GC and its progression. Both the G1612A and C936T genotypes were not associated with the risk of peptic ulcer diseases. Our data suggest that the G1612A, but not C936T polymorphisms in the 3'-UTR of VEGF gene is associated with the susceptibility to GC in the Japanese population.

Hypoxia targeting gene expression for breast cancer gene therapy

Gene therapy is a promising strategy to treat various inherited and acquired diseases. However, targeting gene expression to specific tissue is required to minimize side effects of gene therapy. Hypoxia is present in the microenvironment of solid tumors such as breast tumors. A hypoxic tumor targeting gene expression system has been developed for cancer gene therapy. In hypoxic tissues, hypoxia inducible factor (HIF)-1alpha is accumulated and stimulates transcription of the genes that have hypoxia response elements (HREs) in their promoters. Therefore, transcriptional regulation with a hypoxia inducible promoter is the most widely used strategy for hypoxic tumors targeting gene therapy. In breast cancer gene therapy, breast tumor specific promoters in combination with HREs have been used to induce gene expression in hypoxic breast tumors. Post-transcriptional regulation using an untranslated region (UTR) is also a useful strategy to increase gene expression in hypoxic tumor tissue. In addition, post-translational regulation with the oxygen-dependent degradation (ODD) domain is effective to eliminate therapeutic gene products and reduce side effects in normal tissue. In combination with the breast tumor specific promoters, hypoxic tumor targeting strategies will be useful for the development of a safe breast cancer gene therapy.

Hypoxia-specific gene expression for ischemic disease gene therapy

Gene therapy for ischemic diseases has been developed with various growth factors and anti-apoptotic genes. However, non-specific expression of therapeutic genes may induce deleterious side effects such as tumor formation. Hypoxia-specific regulatory systems can be used to regulate transgene expression in hypoxic tissues, in which gene expression is induced in ischemic tissues, but reduced in normal tissues by transcriptional, translational or post-translational regulation. Since hypoxia-inducible factor 1 (HIF-1) activates transcription of genes in hypoxic tissues, it can play an important role in the prevention of myocardial and cerebral ischemia. Hypoxia-specific promoters including HIF-1 binding sites have been used for transcriptional regulation of therapeutic genes. Also, hypoxia-specific untranslated regions (UTRs) and oxygen dependent degradation (ODD) domains have been investigated for translational and post-translational regulations, respectively. Hypoxia-specific gene expression systems have been applied to various ischemic disease models, including ischemic myocardium, stroke, and injured spinal cord. This review examines the current status and future challenges of hypoxia-specific systems for safe and effective gene therapy of ischemic diseases.

AMPK regulates basal skeletal muscle capillarization and VEGF expression, but is not necessary for the angiogenic response to exercise

5'-AMP-activated protein kinase (AMPK) is a metabolic fuel sensor that monitors cellular energy charge, while the vasculature is important for maintaining cellular energy homeostasis. Mice with muscle-specific inactive AMPK (AMPK DN) were used to investigate if AMPK regulates skeletal muscle capillarization and the angiogenic responses to exercise. Two hours of the AMP analogue AICAR (1.0 g kg(-1)) or systemic hypoxia (6% O(2)) increased vascular endothelial growth factor (VEGF) mRNA in wild-type (WT), but not in AMPK DN mice. In contrast, the increase in VEGF mRNA with acute exercise (1 h at 20 m min(-1), 10% gradient) was greater in AMPK DN compared to WT mice. Nuclear run-on assay demonstrated that exercise increased VEGF transcription, while hypoxia decreased VEGF transcription. There was no difference in VEGF transcription between WT and AMPK DN. There was a strong correlation between VEGF transcription and VEGF mRNA at rest and with exercise. Resting capillarization was lower in AMPK DN compared to WT. Wheel running (28 days) increased capillarization and this response was AMPK independent. Significant correlations between VEGF protein and muscle capillarization are consistent with VEGF being an important determinant of skeletal muscle capillarization. These data are to our knowledge the first to demonstrate in skeletal muscle in vivo that: (1) AMPK is necessary for hypoxia-induced VEGF mRNA stabilization, (2) acute exercise increases VEGF transcription, (3) inhibition of AMPK augments the VEGF mRNA response to acute exercise, and (4) AMPK regulates basal VEGF expression and capillarization, but is not necessary for exercise-induced angiogenesis.

Unbiased screening for transcriptional targets of ZKSCAN3 identifies integrin beta 4 and vascular endothelial growth factor as downstream targets

We previously described the novel zinc finger protein ZKSCAN3 as a new "driver" of colon cancer progression. To investigate the underlying mechanism and because the predicted structural features (tandem zinc fingers) are often present in transcription factors, we hypothesized that ZKSCAN3 regulates the expression of a gene(s) favoring tumor progression. We employed unbiased screening to identify a DNA binding motif and candidate downstream genes. Cyclic amplification and selection of targets using a random oligonucleotide library and ZKSCAN3 protein identified KRDGGG as the DNA recognition motif. In expression profiling, 204 genes were induced 2-29-fold, and 76 genes reduced 2-5-fold by ZKSCAN3. To enrich for direct targets, we eliminated genes under-represented (<3) for the ZKSCAN3 binding motif (identified by CAST-ing) in 2 kilobases of regulatory sequence. Up-regulated putative downstream targets included genes contributing to growth (c-Met-related tyrosine kinase (MST1R), MEK2; the guanine nucleotide exchanger RasGRP2, insulin-like growth factor-2, integrin beta 4), cell migration (MST1R), angiogenesis (vascular endothelial growth factor), and proteolysis (MMP26; cathepsin D; PRSS3 (protease serine 3)). We pursued integrin beta 4 (induced up to 6-fold) as a candidate target because it promotes breast cancer tumorigenicity and stimulates phosphatidyl 3-kinase implicated in colorectal cancer progression. ZKSCAN3 overexpression/silencing modulated integrin beta 4 expression, confirming the array analysis. Moreover, ZKSCAN3 bound to the integrin beta 4 promoter in vitro and in vivo, and the integrin beta 4-derived ZKSCAN3 motif fused upstream of a tk-Luc reporter conferred ZKSCAN3 sensitivity. Integrin beta 4 knockdown by short hairpin RNA countered ZKSCAN3-augmented anchorage-independent colony formation. We also demonstrate vascular endothelial growth factor as a direct ZKSCAN3 target. Thus, ZKSCAN3 regulates the expression of several genes favoring tumor progression including integrin beta 4.

Polymeric gene delivery of ischemia-inducible VEGF significantly attenuates infarct size and apoptosis following myocardial infarct

The development of clinically beneficial myocardial gene therapy has been slowed by reliance on the use of viral carriers and non-physiologic, constitutive gene expression. To specifically address these issues, we have developed a non-viral gene carrier, water-soluble lipopolymer (WSLP), and an ischemia-inducible plasmid construct expressing vascular endothelial growth factor (VEGF), pRTP801-VEGF, to treat myocardial ischemia and infarction. Rabbits underwent ligation of the circumflex artery followed by injection of (a) an ischemia-inducible VEGF gene construct in a WSLP carrier; (b) a constitutively expressed, or unregulated, SV-VEGF gene construct in a WSLP carrier; (c) WSLP carrier alone; or (d) no injection therapy. Following 4 weeks treatment, ligation alone resulted in infarction of 48+/-7% of the left ventricle. With injection of WSLP carrier alone, 49+/-6% of the left ventricle was infarcted (P=NS). The constitutively expressed gene construct, SV-VEGF, reduced the infarct size to 32+/-7% of the left ventricle (P=0.007). The ischemia-inducible gene construct, RTP801-VEGF, further reduced the infarct size to 13+/-4% of the left ventricle (P<0.001). The use of a non-viral carrier to deliver an ischemia-inducible VEGF construct is effective in the treatment of acutely ischemic myocardium.