Hypoxia-inducible Factor Family Research Articles

РОЛЬ ИММУННОГО ОТВЕТА В РАЗВИТИИ ГИПОКСИЧЕСКИХ ОСЛОЖНЕНИЙ РЕСПИРАТОРНЫХ ИНФЕКЦИЙ НИЖНИХ ДЫХАТЕЛЬНЫХ ПУТЕЙ У ДЕТЕЙ

Pneumonia is one of the most common severe infectious diseases in pediatric practice. Hypoxia is common in children with pneumonia and is one of the main predictors of poor outcome. The role of the central link in the cellular response to hypoxia is played by the family of hypoxia-inducible factors (HIF). HIF-1α is the key regulator of both T- and B-lymphocyte functions. The processes of their maturation are accompanied by the formation of circular DNA fragments, TREC (T-cell Receptor Excision Circle) and KREC (Kappa-deleting Recombination Excision Circle). TREC and KREC are unable to replicate and serve as markers for naive lymphocyte production. In its turn, HIF-1α can be used as a marker for cellular hypoxia. The use of TREC and KREC in assessing the immune system in patients with various immunological and infectious pathologies has already been described. At the same time, HIF-1α has so far been little studied as yet. The purpose of this research was to analyze the scientific bibliographical data on the HIF-1α assessment as a marker for hypoxia as well as the quantitative level of TREC and KREC as markers for the adaptive immune response; to study the bibliographical sources on the effect of hypoxia on the immune response, including as part of lower respiratory tract infections. Methods used: bibliographical research in Scopus, PubMed and Google Scholar with keywords “TREC,” “KREC,” “HIF,” “hypoxia,” “pneumonia,” “immune response,” that was then followed by the search results’ systematization, analysis and synthesis. Results: the analysis of bibliographical sources had allowed the Authors to conclude that there is a possible close connection between acute hypoxia and the formation of an adequate immune response in infectious pathologies. Research in this area is still extremely scarce. At the same time, the prospects for this area determine the need for further fundamental and clinical research. Conclusion: it is of a great scientific and clinical interest to be able to non-invasively assess the degree of acute hypoxia during an ongoing infectious disease by examining urinary HIF-1α levels. Particularly promising is the assessment of the HIF-1α level not only as a regulator of tissue adaptation to acute hypoxia, but also as a modulator of the immune response. Taking into consideration the analyzed data, both TREC and KREC appear to be the optimal markers characterizing the functional state of the adaptive immune system.

Diverse responses of hypoxia-inducible factor alpha mRNA abundance in fish exposed to low oxygen: the importance of reporting methods.

Low dissolved oxygen (hypoxia) poses significant challenges to aquatic ecosystems, affecting the behavior, reproduction, and survival of aquatic organisms. Some fishes respond to hypoxia by changes in gene expression, which may be regulated by the hypoxia inducible factor (HIF) family of transcription factors. HIF abundance and activity depends upon the post-translational modification of the alpha protein subunit, although several studies indicate that HIFA mRNA abundance increases in tissues of fishes exposed to hypoxia. This study reviewed reports of laboratory exposures of adult ray-finned fishes to hypoxia and used generalized linear mixed effects models to examine the influence of HIFA gene, tissue sampled, and exposure conditions in explaining the diversity of responses seen in HIFA mRNA abundance. The frequency of hypoxia-induced increases in HIFA mRNA was poorly explained by gene, tissue, or the severity of the hypoxic exposure. Rather, the frequency of reported increases was strongly related to the extent to which studies adhered to guidelines for documenting quantitative real-time PCR methods: the frequency of hypoxia-induced increases in HIFA mRNA decreased sharply in studies with more thorough description of experimental design. Future research should (a) adhere to stringent reporting of experimental design, (b) address the relative paucity of data on HIF2A and HIF3A, and (c) determine levels of HIF alpha protein subunits. By following these recommendations, it is hoped that a more complete understanding will be gained of the role of the HIF family of transcription factors in the response of fish to hypoxia.

The role of microRNA in the regulation of cellular responses to hypoxia

The impact of hypoxia causes changes in the transcription of genes that contribute to the adaptation of cells to a lack of oxygen. The main mechanism regulating the cellular response to hypoxia is the activation of a group of transcription factors of the HIF (Hypoxia-Inducible Factor) family, which include several isoforms and control the expression of more than a thousand genes. HIF activity is regulated at various levels, including by small non-coding RNA molecules called microRNAs (miRNAs). miRNAs regulate the cellular response to hypoxia by influencing the activation of HIF, its degradation, and the translation of proteins dependent on it. At the same time, HIF also affects miRNA biogenesis. Data on the relationship of a particular HIF isoform with miRNA are contradictory, since studies are performed using different cell lines, different types of experimental animals and clinical material, as well as at different oxygen concentrations and different durations of hypoxic exposure. In addition, HIF expression may be affected by the initial resistance of organisms to lack of oxygen, which is not taken into account in studies. This review analyzes data on the effect of hypoxia on the biogenesis and functioning of miRNAs, as well as the effect of microRNAs on mRNAs of genes involved in adaptation to oxygen deficiency. Understanding the mechanisms of the relationship between HIF, hypoxia, and miRNA is necessary to develop new approaches to personalized therapy for diseases accompanied by oxygen deficiency.

Updated perspective of EPAS1 and the role in pulmonary hypertension.

Pulmonary hypertension (PH) is a group of syndromes characterized by irreversible vascular remodeling and persistent elevation of pulmonary vascular resistance and pressure, leading to ultimately right heart failure and even death. Current therapeutic strategies mainly focus on symptoms alleviation by stimulating pulmonary vessel dilation. Unfortunately, the mechanism and interventional management of vascular remodeling are still yet unrevealed. Hypoxia plays a central role in the pathogenesis of PH and numerous studies have shown the relationship between PH and hypoxia-inducible factors family. EPAS1, known as hypoxia-inducible factor-2 alpha (HIF-2α), functions as a transcription factor participating in various cellular pathways. However, the detailed mechanism of EPAS1 has not been fully and systematically described. This article exhibited a comprehensive summary of EPAS1 including the molecular structure, biological function and regulatory network in PH and other relevant cardiovascular diseases, and furthermore, provided theoretical reference for the potential novel target for future PH intervention.

Mechanisms governing target search and binding dynamics of hypoxia-inducible factors.

Transcription factors (TFs) are classically attributed a modular construction, containing well-structured sequence-specific DNA-binding domains (DBDs) paired with disordered activation domains (ADs) responsible for protein-protein interactions targeting co-factors or the core transcription initiation machinery. However, this simple division of labor model struggles to explain why TFs with identical DNA-binding sequence specificity determined in vitro exhibit distinct binding profiles in vivo. The family of hypoxia-inducible factors (HIFs) offer a stark example: aberrantly expressed in several cancer types, HIF-1α and HIF-2α subunit isoforms recognize the same DNA motif in vitro - the hypoxia response element (HRE) - but only share a subset of their target genes in vivo, while eliciting contrasting effects on cancer development and progression under certain circumstances. To probe the mechanisms mediating isoform-specific gene regulation, we used live-cell single particle tracking (SPT) to investigate HIF nuclear dynamics and how they change upon genetic perturbation or drug treatment. We found that HIF-α subunits and their dimerization partner HIF-1β exhibit distinct diffusion and binding characteristics that are exquisitely sensitive to concentration and subunit stoichiometry. Using domain-swap variants, mutations, and a HIF-2α specific inhibitor, we found that although the DBD and dimerization domains are important, another main determinant of chromatin binding and diffusion behavior is the AD-containing intrinsically disordered region (IDR). Using Cut&Run and RNA-seq as orthogonal genomic approaches, we also confirmed IDR-dependent binding and activation of a specific subset of HIF target genes. These findings reveal a previously unappreciated role of IDRs in regulating the TF search and binding process that contribute to functional target site selectivity on chromatin.

Effects of Ion-Transporting Proteins on the Digestive System Under Hypoxia.

Hypoxia refers to a state of oxygen limitation, which mainly mediates pathological processes in the human body and participates in the regulation of normal physiological processes. In the hypoxic environment, the main regulator of human body homeostasis is the hypoxia-inducible factor family (HIF). HIF can regulate the expression of many hypoxia-induced genes and then participate in various physiological and pathological processes of the human body. Ion-transporting proteins are extremely important types of proteins. Ion-transporting proteins are distributed on cell membranes or organelles and strictly control the inflow or outflow of ions in cells or organelles. Changes in ions in cells are often closely related to extensive physiological and pathological processes in the human body. Numerous studies have confirmed that hypoxia and its regulatory factors can regulate the transcription and expression of ion-transporting protein-related genes. Under hypoxic stress, the regulation and interaction of ion-transporting proteins by hypoxia often leads to diseases of various human systems and even tumors. Using ion-transporting proteins and hypoxia as targets to explore the mechanism of digestive system diseases and targeted therapy is expected to become a new breakthrough point.

Pull the plug: Anti-angiogenesis potential of natural products in gastrointestinal cancer therapy.

Gastrointestinal cancer (GIC), including gastric cancer and colorectal cancer, is a common malignant tumor originating from the gastrointestinal epithelium. Although the pathogenesis of GIC has not been fully elucidated, angiogenesis is recognized as the key pathological basis for the growth, invasion and metastasis of cancer cells, and GIC angiogenesis is closely related to vascular endothelial growth factor family, hypoxia-inducible factor family, fibroblast growth factor family and matrix metalloproteinase family. Recently, many natural products have shown a wide range of pharmacological biological activities against GIC. In this review, the effects and mechanisms of natural compounds on the angiogenesis of gastric and colorectal cancer were summarized. The results show that some natural compounds, especially gallic catechin gallate, astragaloside and curcumin, can effectively inhibit angiogenesis; the HIF-1α/VEGF, COX-2/PGE2, HGF/c-Met and PI3K/Akt/mTOR are involved in these inhibition effects. This review examines the anti-angiogenesis potential of natural products in the GIC treatment and provides clues to the development of vascular targeted agents.

Abstract 119: Pan-cancer analysis of HIF pathways defines a robust molecular signature that reflects tissue and cellular hypoxia in bulk and single-cell RNA-seq analyses

Abstract Low levels of tissue oxygen, or intra-tumor hypoxia, is a common feature of many solid cancers in which dysregulated cell proliferation often outstrips the ability to develop new functional blood vessels. Furthermore, hypoxia pathways may also be activated in response to mutation in key tumor suppressor genes or oncogenes. Importantly, in many types of cancer, activation of hypoxia pathways is associated with a clinically aggressive phenotype as well as with resistance to therapy. Indeed, hypoxia drives many of the “hallmarks” of cancer, including cell proliferation, apoptosis, metabolism, immune responses, genomic instability, vascularization, invasion and metastasis. However, the full-range of genes activated by hypoxia varies greatly between cell-types and for many this remains uncharacterized. The key mediator of the cellular transcriptional response to hypoxia is the HIF (hypoxia-inducible factor) family of transcription factors. Here, we generate pan-genomic datasets encompassing HIF ChIP-seq and RNA-seq across cancer cell lines from diverse common tumor types. We then employ integrated analysis of our 72 transcriptome and whole-genome-binding datasets to define a core set of HIF-target genes that are conserved across multiple cell types. We show that these genes can be used to identify HIF activation and tumor hypoxia in bulk RNA-seq analysis of solid tumors, and that this can be applied to large tumor databases (TCGA). We then leverage this analysis to identify tumor-type-specific HIF-associated genes in 32 different cancer types, including those lacking cell-culture models. We further show that these conserved HIF-target genes can be applied to single cell RNA-seq datasets from solid tumors and used to examine intra-tumor heterogeneity in HIF-pathway activation within individual cancer samples. Importantly, using a panel of genes reduces the phenomenon of “drop-out” typically observed in gene-level expression in these datasets. Lastly, applying this gene signature to single cell data allows the hypoxia response to be deconvoluted across diverse cell-types in heterogenous tumor samples. This includes not only the identification of HIF-activity in cancer cells, but also in non-cancer cells within the tumor, thereby allowing the effects of intra-tumor hypoxia on stromal responses (such as tumor angiogenesis) to be studied in vivo in solid tumors. Citation Format: Olivia Lombardi, Ran Li, Silvia Halim, Peter J. Ratcliffe, David R. Mole. Pan-cancer analysis of HIF pathways defines a robust molecular signature that reflects tissue and cellular hypoxia in bulk and single-cell RNA-seq analyses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 119.

Inhibition of aberrant Hif1\u03b1 activation delays intervertebral disc degeneration in adult mice

The intervertebral disc (IVD) is the largest avascular tissue. Hypoxia-inducible factors (HIFs) play essential roles in regulating cellular adaptation in the IVD under physiological conditions. Disc degeneration disease (DDD) is one of the leading causes of disability, and current therapies are ineffective. This study sought to explore the role of HIFs in DDD pathogenesis in mice. The findings of this study showed that among HIF family members, Hif1α was significantly upregulated in cartilaginous endplate (EP) and annulus fibrosus (AF) tissues from human DDD patients and two mouse models of DDD compared with controls. Conditional deletion of the E3 ubiquitin ligase Vhl in EP and AF tissues of adult mice resulted in upregulated Hif1α expression and age-dependent IVD degeneration. Aberrant Hif1α activation enhanced glycolytic metabolism and suppressed mitochondrial function. On the other hand, genetic ablation of the Hif1α gene delayed DDD pathogenesis in Vhl-deficient mice. Administration of 2-methoxyestradiol (2ME2), a selective Hif1α inhibitor, attenuated experimental IVD degeneration in mice. The findings of this study show that aberrant Hif1α activation in EP and AF tissues induces pathological changes in DDD, implying that inhibition of aberrant Hif1α activity is a potential therapeutic strategy for DDD.

Integrative Map of HIF1A Regulatory Elements and Variations.

Hypoxia-inducible factor (HIF) family of transcription factors (HIF1A, EPAS1, and HIF3A) are regulators of the cellular response to hypoxia. They have been shown to be involved in development of various diseases such as cancer, diabetes, and erythrocytosis. A complete map of connections between HIF family of genes with various omics types has not yet been developed. The main aim of the present analysis was to construct the integrative map of genomic elements associated with HIF1A gene and prioritize potentially deleterious variants. Various genomic databases and bioinformatics tools were used, including Ensembl, MirTarBase, STRING, Cytoscape, MethPrimer, CADD, SIFT, and UALCAN. Integrative HIF1A gene map was visualized and includes transcriptional and post-transcriptional regulators, downstream targets, and genetic variants. One CpG island overlaps transcription start site of the HIF1A gene. Out of over 450 missense variants, four have predicted deleterious effect on protein function by at least five bioinformatics tools. Currently there are 85 miRNAs reported to target HIF1A. HIF1A downstream targets include protein-coding genes, long noncoding RNAs, and microRNAs (hypoxamiRs). The study presents the first integration of heterogeneous molecular interactions associated with HIF1A gene enabling a holistic view of the gene and lays the groundwork for supplementing the data in the future.

Integrative Analysis Reveals the Landscape of Hypoxia-Inducible Factor (HIF) Family Genes in Pan-Cancer.

Inside the cancer microenvironment, reduced O2 concentration, termed as hypoxia, is a common phenotype and leads to cancer progression. However, little is known about how and when those HIF members are dysregulated in distinct cancers. Here, by integrating a full range of data of thousands of patients, we comprehensively analyzed the genetics, epigenetics, and transcriptomic level of HIF genes and further defined pathways triggered by disrupted hypoxia-inducible factors. We reveal the expression landscape of HIF family genes and further demonstrate that copy number variations underlie such dysregulation. Further analysis indicates that HIF genes associate with cancer hallmarks such as cell cycle and DNA damage response. Drug resistance analysis showed that HIF globally impacts drug effectiveness such as docetaxel. In summary, the overall analysis reveals the landscape of HIF genes in pan-cancer and may assist mechanism research about hypoxia.

Cell Type-Specific Oxidative Stress Genomic Signatures in the Globus Pallidus of Dopamine-Depleted Mice.

Neuron subtype dysfunction is a key contributor to neurologic disease circuits, but identifying associated gene regulatory pathways is complicated by the molecular complexity of the brain. For example, parvalbumin-expressing (PV+) neurons in the external globus pallidus (GPe) are critically involved in the motor deficits of dopamine-depleted mouse models of Parkinson's disease, where cell type-specific optogenetic stimulation of PV+ neurons over other neuron populations rescues locomotion. Despite the distinct roles these cell types play in the neural circuit, the molecular correlates remain unknown because of the difficulty of isolating rare neuron subtypes. To address this issue, we developed a new viral affinity purification strategy, Cre-Specific Nuclear Anchored Independent Labeling, to isolate Cre recombinase-expressing (Cre+) nuclei from the adult mouse brain. Applying this technology, we performed targeted assessments of the cell type-specific transcriptomic and epigenetic effects of dopamine depletion on PV+ and PV– cells within three brain regions of male and female mice: GPe, striatum, and cortex. We found GPe PV+ neuron-specific gene expression changes that suggested increased hypoxia-inducible factor 2α signaling. Consistent with transcriptomic data, regions of open chromatin affected by dopamine depletion within GPe PV+ neurons were enriched for hypoxia-inducible factor family binding motifs. The gene expression and epigenomic experiments performed on PV+ neurons isolated by Cre-Specific Nuclear Anchored Independent Labeling identified a transcriptional regulatory network mediated by the neuroprotective factor Hif2a as underlying neural circuit differences in response to dopamine depletion.SIGNIFICANCE STATEMENT Cre-Specific Nuclear Anchored Independent Labeling is an enhanced, virus-based approach to isolate nuclei of a specific cell type for transcriptome and epigenome interrogation that decreases dependency on transgenic animals. Applying this technology to GPe parvalbumin-expressing neurons in a mouse model of Parkinson's disease, we discovered evidence for an upregulation of the oxygen homeostasis maintaining pathway involving Hypoxia-inducible factor 2α. These results provide new insight into how neuron subtypes outside the substantia nigra pars compacta may be compensating at a molecular level for differences in the motor production neural circuit during the progression of Parkinson's disease. Furthermore, they emphasize the utility of cell type-specific technologies, such as Cre-Specific Nuclear Anchored Independent Labeling, for isolated assessment of specific neuron subtypes in complex systems.

Beyond glycolysis: Hypoxia signaling as a master regulator of alternative metabolic pathways and the implications in clear cell renal cell carcinoma.

The relationship between kidney cancer, specifically clear cell renal cell carcinoma (ccRCC), and the hypoxia signaling program has been extensively characterized. Its underlying role as the primary driver of the disease has led to the development of the most effective targeted therapies to date. Cellular responses to hypoxia or mutations affecting the von Hippel-Lindau (VHL) tumor suppressor gene stabilize the hypoxia inducible factor (HIF) transcription factors which then orchestrate elaborate downstream signaling events resulting in adaptations to key biological processes, such as reprogramming metabolism. The direct link of hypoxia signaling to glucose uptake and glycolysis has long been appreciated; however, the HIF family of proteins directly regulate many downstream targets, including other transcription factors with their own extensive networks. In this review, we will summarize our current understanding of how hypoxia signaling regulates other metabolic pathways and how this contributes to the development and progression of clear cell renal cell carcinomas.

Regulation of Aquaporin 1 Expression by Hypoxia‐Inducible Factors (HIFs) in Pulmonary Arterial Smooth Muscle Cells (PASMCs)

Prolonged exposure to hypoxia is a common cause of pulmonary hypertension (PH), the pathophysiology of which is characterized by sustained active vasoconstriction and pulmonary vascular remodeling. Studies have shown that HIFs, hypoxia responsive transcription factors, contribute to the development of PH. Three HIF family members have been identified, HIF‐1, HIF‐2, and HIF‐3, of which HIF‐1 and HIF‐2 are the best studied. We have shown that the water channel, aquaporin 1 (AQP1), is expressed in PASMCs and that AQP1 levels are elevated during hypoxia and mediate hypoxia‐induced cell proliferation and migration. The AQP1 promoter contains a HIF binding site, and links between HIF‐1 and AQP1 have been reported in cancer cells, suggesting AQP1 might be a direct HIF target. Thus, we wanted to determine whether either HIF‐1 or HIF‐2 regulates AQP1 in PASMCs. DMOG, which inhibits HIF protein degradation, was used to mimic hypoxia. PASMCs acutely incubated with DMOG exhibited a time‐dependent increase in the levels of AQP1 protein, but not mRNA, whereas both the protein and mRNA levels of a canonical HIF target, GLUT1, were increased. Since we previously reported a link between HIFs and intracellular calcium concentration ([Ca2+]i), as well as a link between [Ca2+]iand AQP1 protein levels, we next determined whether the effects of DMOG on AQP1 were mediated by an increase in [Ca2+]i. Incubation with DMOG caused an increase in [Ca2+]iin PASMCs that was partially prevented by selectively inhibiting either HIF‐1 or HIF‐2. Both inhibitors also partially blocked the DMOG‐induced upregulation of AQP1 protein. When applied together, inhibitors of both HIFs completely blocked the effects of DMOG on [Ca2+]iand AQP1 expression. Thus, our results demonstrate that, in PASMCs, AQP1 protein can be upregulated by both HIF‐1 and HIF‐2, not as a direct target for HIF transcriptional regulation, but rather by a mechanism involving protein accumulation secondary to HIF‐dependent increases in [Ca2+]i.Support or Funding InformationHL12651418POST34030262This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Hypoxia-Inducible Factors and the Regulation of Lipid Metabolism.

Oxygen deprivation or hypoxia characterizes a number of serious pathological conditions and elicits a number of adaptive changes that are mainly mediated at the transcriptional level by the family of hypoxia-inducible factors (HIFs). The HIF target gene repertoire includes genes responsible for the regulation of metabolism, oxygen delivery and cell survival. Although the involvement of HIFs in the regulation of carbohydrate metabolism and the switch to anaerobic glycolysis under hypoxia is well established, their role in the control of lipid anabolism and catabolism remains still relatively obscure. Recent evidence indicates that many aspects of lipid metabolism are modified during hypoxia or in tumor cells in a HIF-dependent manner, contributing significantly to the pathogenesis and/or progression of cancer and metabolic disorders. However, direct transcriptional regulation by HIFs has been only demonstrated in relatively few cases, leaving open the exact and isoform-specific mechanisms that underlie HIF-dependency. This review summarizes the evidence for both direct and indirect roles of HIFs in the regulation of genes involved in lipid metabolism as well as the involvement of HIFs in various diseases as demonstrated by studies with transgenic animal models.

Roxadustat: First Global Approval.

Roxadustat (Ai Rui Zhuo® in China) is an orally administered, small molecule hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitor that is being developed by FibroGen, in collaboration with Astellas and AstraZeneca, for the treatment of anaemia in patients with dialysis-dependent chronic kidney disease (CKD), non-dialysis-dependent CKD and in patients with myelodysplastic syndromes. The drug reversibly binds to and inhibits HIF-prolyl hydroxylase enzymes that are responsible for the degradation of transcription factors in the HIF family under normal oxygen conditions. Inhibition of these enzymes reduces HIF breakdown and promotes HIF activity, leading to an increase in endogenous erythropoietin production, thereby enhancing erythropoiesis. It also reduces the expression of the peptide hormone hepcidin, improves iron availability and increases haemoglobin levels. HIF regulates the expression of genes in response to reduced oxygen levels, including genes required for erythropoiesis and iron metabolism. Roxadustat is approved in China and is under regulatory review in Japan for the treatment of anaemia in patients with dialysis-dependent CKD. Studies are underway to investigate long-term cardiovascular outcomes with roxadustat versus placebo (for non-dialysis-dependent CKD) or standard of care (for dialysis-dependent CKD). This article summarizes the milestones in the development of roxadustat leading to this first approval.

The correlation between NEDD4L and HIF-1α levels as a gastric cancer prognostic marker.

NEDD4L (neural precursor cell expressed developmentally down-regulated 4-like) protein is a member of ubiquitin ligases Nedd4 family. Although studies have shown that Nedd4L may act as a tumor suppressor in various cancers, including gastric cancer (GC), its clinical significance and the diagnostic value in GC is not well defined. HIF-1α (hypoxia inducible factor family of transcription factors) is actively involved in the metabolism of many tumors, although the relationship between its expression levels and clinical significance in GC still need to be established. In this study, the level of HIF-1α and NEDD4L mRNA and protein in 25 freshly frozen GC- and matched normal-tissues were determined by western blot and quantitative PCR (qPCR). Additionally, immunohistochemistry assay was performed to measure the protein level of NEDD4L and HIF-1α in 124 GC and 25 normal control tissues. We observed that the NEDD4L mRNA and protein levels decreased significantly (P < 0.001) in GC tissues, while that of HIF-1α increased (P < 0.001), and they both were associated with a poor prognosis, as was the case in patients with lower NEDD4L and higher HIF-1α expression (P < 0.001). On correlation analysis, a significantly negative relationship (r = 0.288, P < 0.01) was revealed between NEDD4L and HIF-1α expressions. Multivariate analysis revealed that co-expression of NEDD4L (P < 0.05) and HIF-1α (P < 0.001) were independent predictors of GC prognosis. Thus, the correlation of NEDD4L and HIF-1α levels may act as a prognostic marker of GC.

Systems biology analysis of mitogen activated protein kinase inhibitor resistance in malignant melanoma

BackgroundKinase inhibition in the mitogen activated protein kinase (MAPK) pathway is a standard therapy for cancer patients with activating BRAF mutations. However, the anti-tumorigenic effect and clinical benefit are only transient, and tumors are prone to treatment resistance and relapse. To elucidate mechanistic insights into drug resistance, we have established an in vitro cellular model of MAPK inhibitor resistance in malignant melanoma.MethodsThe cellular model evolved in response to clinical dosage of the BRAF inhibitor, vemurafenib, PLX4032. We conducted transcriptomic expression profiling using RNA-Seq and RT-qPCR arrays. Pathways of melanogenesis, MAPK signaling, cell cycle, and metabolism were significantly enriched among the set of differentially expressed genes of vemurafenib-resistant cells vs control. The underlying mechanism of treatment resistance and pathway rewiring was uncovered to be based on non-genomic adaptation and validated in two distinct melanoma models, SK-MEL-28 and A375. Both cell lines have activating BRAF mutations and display metastatic potential.ResultsDownregulation of dual specific phosphatases, tumor suppressors, and negative MAPK regulators reengages mitogenic signaling. Upregulation of growth factors, cytokines, and cognate receptors triggers signaling pathways circumventing BRAF blockage. Further, changes in amino acid and one-carbon metabolism support cellular proliferation despite MAPK inhibitor treatment. In addition, treatment-resistant cells upregulate pigmentation and melanogenesis, pathways which partially overlap with MAPK signaling. Upstream regulator analysis discovered significant perturbation in oncogenic forkhead box and hypoxia inducible factor family transcription factors.ConclusionsThe established cellular models offer mechanistic insight into cellular changes and therapeutic targets under inhibitor resistance in malignant melanoma. At a systems biology level, the MAPK pathway undergoes major rewiring while acquiring inhibitor resistance. The outcome of this transcriptional plasticity is selection for a set of transcriptional master regulators, which circumvent upstream targeted kinases and provide alternative routes of mitogenic activation. A fine-woven network of redundant signals maintains similar effector genes allowing for tumor cell survival and malignant progression in therapy-resistant cancer.

PHD-2 Suppression in Mesenchymal Stromal Cells Enhances Wound Healing.

Cell therapy with mesenchymal stromal cells is a promising strategy for tissue repair. Restoration of blood flow to ischemic tissues is a key step in wound repair, and mesenchymal stromal cells have been shown to be proangiogenic. Angiogenesis is critically regulated by the hypoxia-inducible factor (HIF) superfamily, consisting of transcription factors targeted for degradation by prolyl hydroxylase domain (PHD)-2. The aim of this study was to enhance the proangiogenic capability of mesenchymal stromal cells and to use these modified cells to promote wound healing. Mesenchymal stromal cells harvested from mouse bone marrow were transduced with short hairpin RNA (shRNA) against PHD-2; control cells were transduced with scrambled shRNA (shScramble) construct. Gene expression quantification, human umbilical vein endothelial cell tube formation assays, and wound healing assays were used to assess the effect of PHD knockdown mesenchymal stromal cells on wound healing dynamics. PHD-2 knockdown mesenchymal stromal cells overexpressed HIF-1α and multiple angiogenic factors compared to control (p < 0.05). Human umbilical vein endothelial cells treated with conditioned medium from PHD-2 knockdown mesenchymal stromal cells exhibited increased formation of capillary-like structures and enhanced migration compared with human umbilical vein endothelial cells treated with conditioned medium from shScramble-transduced mesenchymal stromal cells (p < 0.05). Wounds treated with PHD-2 knockdown mesenchymal stromal cells healed at a significantly accelerated rate compared with wounds treated with shScramble mesenchymal stromal cells (p < 0.05). Histologic studies revealed increased blood vessel density and increased cellularity in the wounds treated with PHD-2 knockdown mesenchymal stromal cells (p < 0.05). Silencing PHD-2 in mesenchymal stromal cells augments their proangiogenic potential in wound healing therapy. This effect appears to be mediated by overexpression of HIF family transcription factors and up-regulation of multiple downstream angiogenic factors.

Eye-Opening Potential for Tetraspanin Tspan12 as a Therapeutic Target for Diseases of the Retinal Vasculature

Article, see p 180 Age-related macular degeneration is the leading cause of blindness in industrialized nations, affecting >10 million Americans. The most severe form of macular degeneration, the “wet” form, is caused by growth of abnormal vessels that leak excessive fluid under the retina, damaging the macula and leading to loss of sharp, central, color vision. Vascular endothelial growth factor (VEGF) is a major factor that drives vasoproliferative diseases such as macular degeneration, and antibodies to VEGF are a mainstay of treatment. In this issue of Circulation ,1 Bucher and colleagues identify tetraspanin Tspan12 as a therapeutic target for retinal vascular proliferation, and they invent a Tspan12-targeting therapy. The retinal vasculature is uniquely adapted to supply oxygen and nutrients to photoreceptor cells without blocking incoming light. However, these specialized features also make the retinal vasculature susceptible to vasoproliferative retinopathy, which is the aberrant growth of new blood vessels and breakdown of their barrier function.2 Vasoproliferative retinopathies are driven by VEGF, a key regulator of physiological and pathological angiogenesis. VEGF production is driven primarily by the hypoxia-inducible factor family of transcription factors. VEGF stimulates angiogenesis by interacting with its receptors VEGFR1 and VEGFR2, which in turn activate intracellular signaling cascades such as the Ras-mitogen-activated protein kinase pathway, triggering endothelial migration and proliferation. VEGF-induced VEGFR2 signaling also increases vascular permeability by separating VE-cadherin complexes and intercellular adhesion junctions. The most effective treatment for vasoproliferative retinopathies is anti-VEGF therapy delivered by periodic intravitreal injections. However, the lack of response in some patients and relapses of neovascularization and edema between treatments indicate the clinical need for novel treatments.2 In the current issue of Circulation , Bucher and colleagues1 discovered that tetraspanin Tspan12 is a new therapeutic target for vasoproliferative retinopathies. The tetraspanins are a superfamily of 33 integral membrane with …