SRF in angiogenesis: branching the vascular system

Screening of functional genes for hypoxia adaptation in Tibetan pigs by combined genome resequencing and transcriptome analysis

The high-altitude, low-oxygen environment of the Qinghai-Tibet Plateau poses significant challenges for the introduction of superior livestock breeds. However, local plateau species have adapted to thrive and reproduce under these harsh conditions. Understanding the molecular mechanisms behind plateau animals' adaptation to low-oxygen environments is essential for breeding livestock suited to high-altitude regions. Tibetan pigs, which have undergone long-term natural selection and artificial breeding, have developed the ability to survive and reproduce in hypoxic environments. In this study, we conducted whole-genome resequencing of 30 Tibetan pigs from high-altitude regions and 30 Diannan small-ear pigs from low-altitude areas, to identify candidate genes that support Tibetan pigs' adaptation to hypoxic conditions through selection signal analysis. Additionally, we performed transcriptome sequencing on five tissues (heart, liver, spleen, lung, and bone marrow) from both Tibetan pigs and Diannan small-ear pigs to identify genes with significant differential expression between the two breeds. We then integrated the genomic and transcriptomic data by examining the expression of candidate genes identified in selection signal analysis across different tissues. The selection signal analysis identified 10 genes-HES4, ANGPT1, HIF3A, SPHK2, PCK2, RCN3, HIGD2A, DNM2, IRF9, and SRF-that were under positive selection in the Tibetan pig population and are associated with hypoxia adaptation. When combined with transcriptome data, we found that five of these genes-HIF3A, RCN3, HIGD2A, PCK2, and IRF9-exhibited differential expression. Through an integrated approach of selection signal and transcriptome analysis, we identified five key functional genes that contribute to the adaptation of Tibetan pigs to hypoxic environments. These findings offer new insights into the adaptability of plateau animals.

Roles of LncRNAs in the Pathogenesis of Pulmonary Hypertension

Pulmonary hypertension (PH) is a persistently progressive, incurable, multifactorial associated fatal pulmonary vascular disease characterized by pulmonary vascular remodeling. Long noncoding RNAs (lncRNAs) are involved in regulating pathological processes such as pulmonary vasoconstriction, thickening, remodeling, and inflammatory cell infiltration in PH by acting on different cell types. Because of their differential expression in PH patients, as demonstrated by the observation that some lncRNAs are significantly upregulated while others are significantly downregulated in PH patients, lncRNAs are potentially useful biomarkers for assessing disease progression and diagnosis or prognosis in PH patients. This article provides an overview of the different mechanisms by which lncRNAs are involved in the pathogenesis of PH.

Hypoxia exposure blunts angiogenic signaling and upregulates the antioxidant system in endothelial cells derived from elephant seals

BACKGROUND

Elephant seals exhibit extreme hypoxemic tolerance derived from repetitive hypoxia/reoxygenation episodes they experience during diving bouts. Real-time assessment of the molecular changes underlying protection against hypoxic injury in seals remains restricted by their at-sea inaccessibility. Hence, we developed a proliferative arterial endothelial cell culture model from elephant seals and used RNA-seq, functional assays, and confocal microscopy to assess the molecular response to prolonged hypoxia.

RESULTS

Seal and human endothelial cells exposed to 1% O2 for up to 6 h respond differently to acute and prolonged hypoxia. Seal cells decouple stabilization of the hypoxia-sensitive transcriptional regulator HIF-1α from angiogenic signaling. Rapid upregulation of genes involved in glutathione (GSH) metabolism supports the maintenance of GSH pools, and intracellular succinate increases in seal but not human cells. High maximal and spare respiratory capacity in seal cells after hypoxia exposure occurs in concert with increasing mitochondrial branch length and independent from major changes in extracellular acidification rate, suggesting that seal cells recover oxidative metabolism without significant glycolytic dependency after hypoxia exposure.

CONCLUSIONS

We found that the glutathione antioxidant system is upregulated in seal endothelial cells during hypoxia, while this system remains static in comparable human cells. Furthermore, we found that in contrast to human cells, hypoxia exposure rapidly activates HIF-1 in seal cells, but this response is decoupled from the canonical angiogenesis pathway. These results highlight the unique mechanisms that confer extraordinary tolerance to limited oxygen availability in a champion diving mammal.

Hypoxia blunts angiogenic signaling and upregulates the antioxidant system in elephant seal endothelial cells

Elephant seals experience extreme hypoxemia during diving bouts. Similar depletions in oxygen availability characterize pathologies including myocardial infarction and ischemic stroke in humans, but seals manage these repeated episodes without injury. However, the real-time assessment of the molecular changes underlying protection against hypoxic injury in seals remains restricted by their at-sea inaccessibility. Hence, we developed a proliferative arterial endothelial cell culture system to assess the molecular response to prolonged hypoxia. Seal and human cells exposed to 1% O 2 for up to 6 h demonstrated differential responses to both acute and prolonged hypoxia. Seal cells decouple stabilization of the hypoxia-sensitive transcriptional regulator HIF-1α from angiogenic signaling at both the transcriptional and cellular level. Rapid upregulation of genes involved in the glutathione (GSH) metabolism pathway supported maintenance of GSH pools and increases in intracellular succinate in seal but not human cells during hypoxia exposure. High maximal and spare respiratory capacity in seal cells after hypoxia exposure occurred in concert with increasing mitochondrial branch length and independent from major changes in extracellular acidification rate, suggesting seal cells recover oxidative metabolism without significant glycolytic dependency after hypoxia exposure. In sum, our studies show that in contrast to human cells, seal cells adapt to hypoxia exposure by dampening angiogenic signaling, increasing antioxidant protection, and maintaining mitochondrial morphological integrity and function.

Interplay between LncRNAs and microRNAs in Breast Cancer

(1) Although long noncoding RNAs (lncRNAs) are known to be precursors of microRNAs (miRNAs), they frequently act as competing endogoneous RNAs (ceRNAs), yet still their interplay with miRNA is not well known. However, their interaction with miRNAs may result in the modulation of miRNA action. (2) To determine the contribution of these RNA molecules in tumor resistance to chemotherapeutic drugs, it is essential to consider not only the oncogenic and tumor suppressive function of miRNAs but also the impact of lncRNAs on miRNAs. Therefore, we performed an extensive search in different databases including PubMed. (3) The present study concerns the interplay between lncRNAs and miRNAs in the regulatory post-transcriptional network and their impact on drugs used in the treatment of breast cancer. (4) Consideration of this interplay may improve the search for new drugs to circumvent chemoresistance.

SRSF3 Promotes Angiogenesis in Colorectal Cancer by Splicing SRF

SRSF3, an important member of the serine/arginine-rich protein (SRp) family, is highly expressed in various tumors and plays an important role in tumor cell proliferation, migration and invasion. However, it is still unclear whether SRSF3 is involved in tumor angiogenesis. In this study, we first revealed that SRSF3 regulated the expression of numerous genes related to angiogenesis, including proangiogenic SRF. Then, we confirmed that SRSF3 was highly expressed in colorectal cancer (CRC) and was positively correlated with SRF. Mechanistic studies revealed that SRSF3 directly bound to the “CAUC” motif in exon 6 of SRF and induced the exclusion of introns. Knockdown of SRSF3 significantly reduced the secretion of VEGF from CRC cells. Conditioned medium from SRSF3-knockdown CRC cells significantly inhibited the migration, invasion and tube formation of human umbilical vein endothelial cells (HUVECs). In addition, SRF silencing inhibited angiogenesis, while SRF overexpression reversed the antiangiogenic effects of SRSF3 knockdown on tube formation. These findings indicate that SRSF3 is involved in the splicing of SRF and thereby regulates the angiogenesis of CRC, which offers novel insight into antiangiogenic therapy in CRC.

Cumulus cells of euploid versus whole chromosome 21 aneuploid embryos reveal differentially expressed genes

RESEARCH QUESTION

Can cumulus cells be used as a non-invasive target for the study of determinants of preimplantation embryo quality?

DESIGN

Cumulus cells were collected from monosomy 21, trisomy 21 and euploid embryos and subjected to RNA sequencing analysis and real-time polymerase chain reaction assays. The differential gene expression was analysed for different comparisons.

RESULTS

A total of 3122 genes in monosomy 21 cumulus cells and 19 genes in trisomy 21 cumulus cells were differentially expressed compared with euploid cumulus cells. Thirteen of these genes were differentially expressed in both monosomy and trisomy 21, compared with euploid, including disheveled segment polarity protein 2 (DVL2), cellular communication network factor 1 (CCN1/CYR61) and serum response factor (SRF), which have been previously implicated in embryo developmental competence. In addition, ingenuity pathway analysis revealed cell-cell contact function to be affected in both monosomy and trisomy 21 cumulus cells.

CONCLUSIONS

These findings support the use of cumulus cell gene expression analysis for the development of biomarkers evaluating oocyte quality for patients undergoing fertility preservation of oocytes.

Promoter-specific changes in initiation, elongation, and homeostasis of histone H3 acetylation during CBP/p300 inhibition

Regulation of RNA polymerase II (Pol2) elongation in the promoter-proximal region is an important and ubiquitous control point for gene expression in metazoans. We report that transcription of the adenovirus 5 E4 region is regulated during the release of paused Pol2 into productive elongation by recruitment of the super-elongation complex, dependent on promoter H3K18/27 acetylation by CBP/p300. We also establish that this is a general transcriptional regulatory mechanism that applies to ~7% of expressed protein-coding genes in primary human airway epithelial cells. We observed that a homeostatic mechanism maintains promoter, but not enhancer, H3K18/27ac in response to extensive inhibition of CBP/p300 acetyl transferase activity by the highly specific small molecule inhibitor A-485. Further, our results suggest a function for BRD4 association at enhancers in regulating paused Pol2 release at nearby promoters. Taken together, our results uncover the processes regulating transcriptional elongation by promoter region histone H3 acetylation and homeostatic maintenance of promoter, but not enhancer, H3K18/27ac in response to inhibition of CBP/p300 acetyl transferase activity.

The Effect of 3'-Hydroxy-3,4,5,4'-Tetramethoxy -stilbene, the Metabolite of the Resveratrol Analogue DMU-212, on the Motility and Proliferation of Ovarian Cancer Cells

Targeting tumor cell motility and proliferation is an extremely important challenge in the prevention of metastasis and improving the effectiveness of cancer treatment. We recently published data revealing that DMU-214, the metabolite of firmly cytotoxic resveratrol analogue DMU-212, exerted significantly higher biological activity than the parent compound in ovarian cancer cells. The aim of the present study was to assess the molecular mechanism of the potential anti-migration and anti-proliferative effect of DMU-214 in ovarian cancer cell line SKOV-3. We showed that DMU-214 reduced the migratory capacity of SKOV-3 cells. The microarray analysis indicated ontology groups of genes involved in processes of negative regulation of cell motility and proliferation. Furthermore, we found DMU-214 triggered changes in expression of several migration- and proliferation-related genes (SMAD7, THBS1, IGFBP3, KLF4, Il6, ILA, SOX4, IL15, SRF, RGCC, GPR56) and proteins (GPR56, RGCC, SRF, SMAD7, THBS1), which have been shown to interact to each other to reduce cell proliferation and motility. Our study showed for the first time that DMU-214 displayed anti-migratory and anti-proliferative activity in SKOV-3 ovarian cancer cells. On the basis of whole transcriptome analysis of these cells, we provide new insight into the role of DMU-214 in inhibition of processes related to metastasis.

Enhanced TGF-β Signaling Contributes to the Insulin-Induced Angiogenic Responses of Endothelial Cells

Angiogenesis, the development of new blood vessels, is a key process in disease. We reported that insulin promotes translocation of transforming growth factor β (TGF-β) receptors to the plasma membrane of epithelial and fibroblast cells, thus enhancing TGF-β responsiveness. Since insulin promotes angiogenesis, we addressed whether increased autocrine TGF-β signaling participates in endothelial cell responses to insulin. We show that insulin enhances TGF-β responsiveness and autocrine TGF-β signaling in primary human endothelial cells, by inducing a rapid increase in cell surface TGF-β receptor levels. Autocrine TGF-β/Smad signaling contributed substantially to insulin-induced gene expression associated with angiogenesis, including TGF-β target genes encoding angiogenic mediators; was essential for endothelial cell migration; and participated in endothelial cell invasion and network formation. Blocking TGF-β signaling impaired insulin-induced microvessel outgrowth from neonatal aortic rings and modified insulin-stimulated blood vessel formation in zebrafish. We conclude that enhanced autocrine TGF-β signaling is integral to endothelial cell and angiogenic responses to insulin.

Overexpression of serum response factor is correlated with poor prognosis in patients with gastric cancer

Serum response factor (SRF) is highly expressed in many tumors, including gastric cancer. However, the exact prognostic utility of SRF in patients with gastric cancer remains unclear. Therefore, in this study, we investigated the expression and prognostic value of SRF in patients with gastric cancer. SRF expression was detected by immunohistochemistry in 149 gastric cancer samples. The relationship between SRF expression and clinicopathological characteristics along with the prognostic significance of SRF in disease-free survival and overall survival of patients was analyzed. We found that the expression of SRF was significantly increased in gastric cancer tissues compared with adjacent noncancerous tissues. Overexpression of SRF was significantly correlated with histologic differentiation, invasion depth, lymph node metastasis, and TNM stage. Furthermore, disease-free survival rate and overall survival rate were both significantly lower for patients with high SRF expression. Multivariate Cox regression analysis identified high SRF expression as an independent prognostic factor for disease-free survival but not for overall survival. Our findings indicate that overexpression of SRF may play an important role in human gastric cancer recurrence and prognosis. SRF may serve as a predictive marker for prognosis of gastric cancer.

Genome‑wide DNA methylation profiling in a rat model with vascular dementia

Vascular dementia (VaD), the second most prevalent type of dementia, is caused by reduced blood supply to the brain that results in cognitive impairment. Despite the efforts of numerous studies, the pathological mechanisms behind VaD remain unclear. The aim of the present study was to identify candidate genes that undergo changes in hippocampal DNA methylation owing to VaD. A genome‑wide DNA methylation analysis was performed, using methylated DNA‑binding domain sequencing. VaD model rats with cognitive impairment induced by bilateral common carotid artery occlusion were confirmed using the radial arm maze test. A total of 1,180 differentially methylated genes (DMGs) were identified, and functional annotation analysis revealed the DMGs to be enriched in 10 Gene Ontology biological processes. Network analysis using the STRING database indicated that seven genes were closely connected. Rats in the VaD model group demonstrated relative hypomethylation in the promoter region and increased mRNA expression of the hippocampal genes vascular endothelial growth factor (VEGFA) and kinase insert domain receptor, but only differences in VEGFA mRNA expression levels were determined to be statistically significant. In conclusion, these preliminary data from the functional annotation of hippocampal DMGs in the promoter region highlighted candidate genes for VaD that may contribute to the elucidation of its pathophysiology.

Altered DNA methylation indicates an oscillatory flow mediated epithelial-to-mesenchymal transition signature in ascending aorta of patients with bicuspid aortic valve

Disturbed flow has been suggested to contribute to aneurysm susceptibility in bicuspid aortic valve (BAV) patients. Lately, flow has emerged as an important modulator of DNA methylation. Hear we combined global methylation analysis with in vitro studies of flow-sensitive methylation to identify biological processes associated with BAV-aortopathy and the potential contribution of flow. Biopsies from non-dilated and dilated ascending aortas were collected from BAV (n = 21) and tricuspid aortic valve (TAV) patients (n = 23). DNA methylation and gene expression was measured in aortic intima-media tissue samples, and in EA.hy926 and primary aortic endothelial cells (ECs) isolated from BAV and TAV exposed to oscillatory (±12 dynes/cm²) or laminar (12 dynes/cm²) flow. We show methylation changes related to epithelial-mesenchymal-transition (EMT) in the non-dilated BAV aorta, associated with oscillatory flow related to endocytosis. The results indicate that the flow-response in BAV ECs involves hypomethylation and increased expression of WNT/β-catenin genes, as opposed to an angiogenic profile in TAV ECs. The EMT-signature was exasperated in dilated BAV aortas. Aberrant EMT in BAV aortic walls could contribute to increased aneurysm susceptibility, and may be due to disturbed flow-exposure. Perturbations during the spatiotemporally related embryonic development of ascending aorta and semilunar valves can however not be excluded.

Pharmacological intervention of MKL/SRF signaling by CCG-1423 impedes endothelial cell migration and angiogenesis

De novo synthesis of cytoskeleton-regulatory proteins triggered by the megakaryoblastic leukemia (MKL)/serum response factor (SRF) transcriptional system in response to pro-angiogenic growth factors lies at the heart of endothelial cell (EC) migration (a critical element of angiogenesis) and neovascularization. This study explores whether pharmacological intervention of MKL/SRF signaling axis by CCG-1423 is able to suppress angiogenesis. Our studies show that CCG-1423 inhibits migration and cord morphogenesis of EC in vitro and sprouting angiogenesis ex vivo and in vivo, suggesting CCG-1423 could be a novel anti-angiogenic agent. Kymography analyses of membrane dynamics of EC revealed that CCG-1423 treatment causes a major defect in membrane protrusion. CCG-1423 treatment led to attenuated expression of several actin-binding proteins that are important for driving membrane protrusion including ArpC2, VASP, and profilin1 (Pfn1) with the most drastic effect seen on the expression of Pfn1. Finally, depletion of Pfn1 alone is also sufficient for a dramatic decrease in sprouting angiogenesis of EC in vitro and ex vivo, further suggesting that Pfn1 depletion may be one of the mechanisms of the anti-angiogenic action of CCG-1423.

Serum Response Factor in Muscle Tissues: From Development to Ageing

Skeletal, cardiac and smooth muscle cells share various common characteristic features. During development the embryonic mesodermal layer contribute at different proportions to the formation of these tissues. At the functional level, contractility as well as its decline during ageing, are also common features. Cytoskeletal components of these tissues are characterized by various actin isoforms that govern through their status (polymerised versus monomeric) and their interaction with the myosins the contractile properties of these muscles. Finally, at the molecular level, a set of different transcription factors with the notable exception of Serum Response Factor SRF- which is commonly enriched in the 3 types of muscle- drive and maintain the differentiation of these cells (Myf5, MyoD, Myogenin for skeletal muscle; Nkx2.5, GATA4 for cardiomyocytes). In this review, we will focus on the transcription factor SRF and its role in the homeostasis of cardiac, smooth and skeletal muscle tissues as well as its behaviour during the age related remodelling process of these tissues with a specific emphasis on animal models and human data when available.

Cardioprotection by Thymosin Beta 4

Treatment with thymosin beta 4 (Tβ4) reduces infarct volume and preserves cardiac function in preclinical models of cardiac ischemic injury. These effects stem in part from decreased infarct size, but additional benefits are likely due to specific antifibrotic and proangiogenic activities. Injected or transgenic Tβ4 increase blood vessel growth in large and small animal models, consistent with Tβ4 converting hibernating myocardium to an actively contractile state following ischemia. Tβ4 and its degradation products have antifibrotic effects in in vitro assays and in animal models of fibrosis not related to cardiac injury. This large number of pleiotropic effects results from Tβ4's many interactions with cellular signaling pathways, particularly indirect regulation of cellular motility and movement via the SRF-MRTF-G-actin transcriptional pathway. Variation in effects and effect sizes in animal models may potentially be due to variable distribution of Tβ4. Preclinical studies of PK/PD relationships and a reliable pharmacodynamic biomarker would facilitate clinical development of Tβ4.

Upregulation of miR-483-3p contributes to endothelial progenitor cells dysfunction in deep vein thrombosis patients via SRF

Background

Endothelial progenitor cells (EPCs) contribute to recanalization of deep vein thrombosis (DVT). This study aimed to detect miRNA expression profiles in EPCs from patients with DVT and characterize the role of miRNA in EPCs dysfunction.

Methods

EPCs was isolated from DVT patients and control subjects, and miRNA expression profiles were compared to screen differential miRNAs. The candidate miRNAs were confirmed by RT-PCR analysis. The targets of miRNA were identified by bioinformatics analyses, luciferase reporter assay and gene expression analyses. The apoptosis, migration and tube formation of EPCs were examined by flow cytometry, transwell assay and matrigel tube formation assay. A rat model of venous thrombosis was established as in vivo model.

Results

We identified miR-483-3p as a candidate miRNA upregulated in EPCs from DVT patients. By using miR-483-3p agomir and antagomir, we demonstrated that miR-483-3p decreased the migration and tube formation while increased the apoptosis of EPCs. Moreover, we identified serum response factor (SRF) as the target of miR-483-3p, and showed that SRF knockdown decreased the migration and tube formation while increased the apoptosis of EPCs. In addition, miR-483-3p inhibition led to enhanced ability of homing and thrombus resolution of EPCs in rat model of venous thrombosis.

Conclusions

miR-483-3p is upregulated in EPCs from DVT patients, and it targets SRF to decrease EPCs migration and tube formation and increase apoptosis in vitro, while decrease EPCs homing and thrombus resolution in vivo. MiR-483-3p is a potential therapeutic target in DVT treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-016-0775-2) contains supplementary material, which is available to authorized users.

SMYD1, an SRF-Interacting Partner, Is Involved in Angiogenesis

Previous studies have demonstrated that Smyd1 plays a critical role in cardiomyocyte differentiation, cardiac morphogenesis and myofibril organization. In this study, we uncovered a novel function of Smyd1 in the regulation of endothelial cells (ECs). Our data showed that Smyd1 is expressed in vascular endothelial cells, and knockdown of SMYD1 in endothelial cells impairs EC migration and tube formation. Furthermore, Co-IP and GST pull-down assays demonstrated that SMYD1 is associated with the Serum Response Factor (SRF). EMSA assays further showed that SMYD1 forms a complex with SRF and enhances SRF DNA binding activity. Our studies indicate that SMYD1 serves as an SRF-interacting protein, enhances SRF DNA binding activity, and is required for EC migration and tube formation to regulate angiogenesis.

Alpha-Catulin Co-Localizes With Vimentin Intermediate Filaments and Functions in Pulmonary Vascular Endothelial Cell Migration via ROCK

The ubiquitous α-catulin acts as a scaffold for distinct signalosomes including RhoA/ROCK; however, its function is not well understood. While α-catulin has homology to the cytoskeletal linkers α-catenin and vinculin, it appears to be functionally divergent. Here we further investigated α-catulin function in pulmonary vascular endothelial cells (VEC) on the premise that α-catulin has a unique cytoskeletal role. Examination of endogenous α-catulin intracellular localization by immunofluorescence revealed a highly organized cytosolic filamentous network suggestive of a cytoskeletal system in a variety of cultured VEC. Double-immunofluorescence analyses of VEC showed endogenous α-catulin co-localization with vimentin intermediate filaments. Similar to vimentin, α-catulin was found to distribute into detergent-soluble and -insoluble fractions. Treatment of VEC with withaferinA, an agent that targets vimentin filaments, disrupted the α-catulin network distribution and altered α-catulin solubility. Vimentin participates in cell migration, and withaferinA was found to inhibit VEC migration in vitro; similarly, α-catulin knock-down reduced VEC migration. Based on previous reports showing that ROCK modulates vimentin, we found that ROCK depletion attenuated VEC migration; furthermore, α-catulin depletion was shown to reduce ROCK-induced signaling. These findings indicate that α-catulin has a unique function in co-localization with vimentin filaments that contributes to VEC migration via a pathway that may involve ROCK signaling. J. Cell. Physiol. 231: 934-943, 2016. © 2015 Wiley Periodicals, Inc.

SRF selectively controls tip cell invasive behavior in angiogenesis

Efficient angiogenic sprouting is essential for embryonic, postnatal and tumor development. Serum response factor (SRF) is known to be important for embryonic vascular development. Here, we studied the effect of inducible endothelial-specific deletion of Srf in postnatal and adult mice. We find that endothelial SRF activity is vital for postnatal growth and survival, and is equally required for developmental and pathological angiogenesis, including during tumor growth. Our results demonstrate that SRF is selectively required for endothelial filopodia formation and cell contractility during sprouting angiogenesis, but seems dispensable for vascular remodeling. At the molecular level, we observe that vascular endothelial growth factor A induces nuclear accumulation of myocardin-related transcription factors (MRTFs) and regulates MRTF/SRF-dependent target genes including Myl9, which is important for endothelial cell migration in vitro. We conclude that SRF has a unique function in regulating migratory tip cell behavior during sprouting angiogenesis. We hypothesize that targeting the SRF pathway could provide an opportunity to selectively target tip cell filopodia-driven angiogenesis to restrict tumor growth.

A pathogenic relationship between a regulator of the actin cytoskeleton and serum response factor

Cell hyperproliferation, inflammation, and angiogenesis are biological processes central to the pathogenesis of corneal disease, as well as other conditions including tumorigenesis and chronic inflammatory disorders. Due to the number of disease conditions that arise as a result of these abnormalities, identifying the molecular mechanisms underlying these processes is critical. The avascular and transparent cornea serves as a good in vivo model to study the pathogenesis of cell hyperproliferation, inflammation, and angiogenesis. Corneal disease 1 (Dstn(corn1)) mice are homozygous for a spontaneous null allele of the destrin (Dstn) gene, which is also known as actin depolymerizing factor (ADF). These mice exhibit abnormalities in the cornea including epithelial cell hyperproliferation, stromal inflammation, and neovascularization. We previously identified that the transcription factor, serum response factor (SRF) and a number of its target genes are upregulated in the cornea of these mice. In this study, we show that conditional ablation of Srf in the corneal epithelium of a diseased Dstn(corn1) cornea results in the rescue of the epithelial cell hyperproliferation, inflammation, and neovascularization phenotypes, delineating an epithelial cell-specific role for SRF in the development of all of these abnormalities. Our study also demonstrates that Dstn is genetically upstream of Srf and defines a new functional role for SRF as the master regulator of a hyperproliferative, inflammatory phenotype accompanied by neovascularization.

MicroRNA-122 inhibits tumorigenic properties of hepatocellular carcinoma cells and sensitizes these cells to sorafenib

MicroRNAs are negative regulators of protein coding genes. The liver-specific microRNA-122 (miR-122) is frequently suppressed in primary hepatocellular carcinomas (HCCs). In situ hybridization demonstrated that miR-122 is abundantly expressed in hepatocytes but barely detectable in primary human HCCs. Ectopic expression of miR-122 in nonexpressing HepG2, Hep3B, and SK-Hep-1 cells reversed their tumorigenic properties such as growth, replication potential, clonogenic survival, anchorage-independent growth, migration, invasion, and tumor formation in nude mice. Further, miR-122-expressing HCC cells retained an epithelial phenotype that correlated with reduced Vimentin expression. ADAM10 (a distintegrin and metalloprotease family 10), serum response factor (SRF), and insulin-like growth factor 1 receptor (Igf1R) that promote tumorigenesis were validated as targets of miR-122 and were repressed by the microRNA. Conversely, depletion of the endogenous miR-122 in Huh-7 cells facilitated their tumorigenic properties with concomitant up-regulation of these targets. Expression of SRF or Igf1R partially reversed tumor suppressor function of miR-122. Further, miR-122 impeded angiogenic properties of endothelial cells in vitro. Notably, ADAM10, SRF, and Igf1R were up-regulated in primary human HCCs compared with the matching liver tissue. Co-labeling studies demonstrated exclusive localization of miR-122 in the benign livers, whereas SRF predominantly expressed in HCC. More importantly, growth and clonogenic survival of miR-122-expressing HCC cells were significantly reduced upon treatment with sorafenib, a multi-kinase inhibitor clinically effective against HCC. Collectively, these results suggest that the loss of multifunctional miR-122 contributes to the malignant phenotype of HCC cells, and miR-122 mimetic alone or in combination with anticancer drugs can be a promising therapeutic regimen against liver cancer.