Gene array analysis reveals a common Runx transcriptional programme controlling cell adhesion and survival

Kartogenin-loaded polyvinyl alcohol/nano-hydroxyapatite composite hydrogel promotes tendon-bone healing in rabbits after anterior cruciate ligament reconstruction

Accumulating evidence supports the role of cartilage tissue engineering in cartilage defect repair, but the biological function has yet to be fully explained. In this work, kartogenin (KGN), an emerging chondroinductive nonprotein small molecule, was incorporated into a composite hydrogel of polyvinyl alcohol/nano-hydroxyapatite (PVA/n-HA) to fabricate an appropriate microenvironment for tendon-bone healing after anterior cruciate ligament (ACL) reconstruction. KGN/PVA/n-HA composite hydrogel scaffolds were prepared by in situ synthesis and physical adsorption, followed by characterization under a scanning electron microscope. The scaffolds were transplanted into healthy New Zealand White (NZW) rabbits. It was confirmed that KGN/PVA/n-HA scaffolds were successfully prepared and exhibited good supporting properties and excellent biocompatibility. Unilateral ACL reconstruction was constructed with tendon autograft in NZW rabbits, and the morphology and diameter of collagen fiber were analyzed. The scaffolds were shown to promote ACL growth and collagen fiber formation. Furthermore, microcomputerized tomography analysis and bone formation histology were performed to detect new bone formation. KGN/PVA/n-HA scaffolds effectively alleviated cartilage damage and prevented the occurrence of osteoarthritis. Meanwhile, ligament-bone healing and bone formation were observed in the presence of KGN/PVA/n-HA scaffolds. In conclusion, these results suggest that the KGN/PVA/n-HA scaffolds can facilitate tendon-bone healing after ACL reconstruction and might be considered novel hydrogel biomaterials in cartilage tissue engineering.

Combination of RUNX1 inhibitor and gemcitabine mitigates chemo-resistance in pancreatic ductal adenocarcinoma by modulating BiP/PERK/eIF2α-axis-mediated endoplasmic reticulum stress

BACKGROUND

Gemcitabine (GEM)-based chemotherapy is the first-line option for pancreatic ductal adenocarcinoma (PDAC). However, the development of drug resistance limits its efficacy, and the specific mechanisms remain largely unknown. RUNX1, a key transcription factor in hematopoiesis, also involved in the malignant progression of PDAC, but was unclear in the chemoresistance of PDAC.

METHODS

Comparative analysis was performed to screen GEM-resistance related genes using our single-cell RNA sequencing(scRNA-seq) data and two public RNA-sequencing datasets (GSE223463, GSE183795) for PDAC. The expression of RUNX1 in PDAC tissues was detected by qRT-PCR, immunohistochemistry (IHC) and western blot. The clinical significance of RUNX1 in PDAC was determined by single-or multivariate analysis and survival analysis. We constructed the stably expressing cell lines with shRUNX1 and RUNX1, and successfully established GEM-resistant cell line. The role of RUNX1 in GEM resistance was determined by CCK8 assay, plate colony formation assay and apoptosis analysis in vitro and in vivo. To explore the mechanism, we performed bioinformatic analysis using the scRNA-seq data to screen for the endoplasm reticulum (ER) stress signaling that was indispensable for RUNX1 in GEM resistance. We observed the cell morphology in ER stress by transmission electron microscopy and validated RUNX1 in gemcitabine resistance depended on the BiP/PERK/eIF2α pathway by in vitro and in vivo oncogenic experiments, using ER stress inhibitor(4-PBA) and PERK inhibitor (GSK2606414). The correlation between RUNX1 and BiP expression was assessed using the scRNA-seq data and TCGA dataset, and validated by RT-PCR, immunostaining and western blot. The mechanism of RUNX1 regulation of BiP was confirmed by ChIP-PCR and dual luciferase assay. Finally, the effect of RUNX1 inhibitor on PDAC was conducted in vivo mouse models, including subcutaneous xenograft and patient-derived xenograft (PDX) mouse models.

RESULTS

RUNX1 was aberrant high expressed in PDAC and closely associated with GEM resistance. Silencing of RUNX1 could attenuate resistance in GEM-resistant cell line, and its inhibitor Ro5-3335 displayed an enhanced effect in inhibiting tumor growth, combined with GEM treatment, in PDX mouse models and GEM-resistant xenografts. In detail, forced expression of RUNX1 in PDAC cells suppressed apoptosis induced by GEM exposure, which was reversed by the ER stress inhibitor 4-PBA and PERK phosphorylation inhibitor GSK2606414. RUNX1 modulation of ER stress signaling mediated GEM resistance was supported by the analysis of scRNA-seq data. Consistently, silencing of RUNX1 strongly inhibited the GEM-induced activation of BiP and PERK/eIF2α signaling, one of the major pathways involved in ER stress. It was identified that RUNX1 directly bound to the promoter region of BiP, a primary ER stress sensor, and stimulated BiP expression to enhance the reserve capacity for cell adaptation, which in turn facilitated GEM resistance in PDAC cells.

CONCLUSIONS

This study identifies RUNX1 as a predictive biomarker for response to GEM-based chemotherapy. RUNX1 inhibition may represent an effective strategy for overcoming GEM resistance in PDAC cells.

Genetics and Molecular Basis of Congenital Heart Defects in Down Syndrome: Role of Extracellular Matrix Regulation

Down syndrome (DS), a complex disorder that is caused by the trisomy of chromosome 21 (Hsa21), is a major cause of congenital heart defects (CHD). Interestingly, only about 50% of individuals with Hsa21 trisomy manifest CHD. Here we review the genetic basis of CHD in DS, focusing on genes that regulate extracellular matrix (ECM) organization. The overexpression of Hsa21 genes likely underlies the molecular mechanisms that contribute to CHD, even though the genes responsible for CHD could only be located in a critical region of Hsa21. A role in causing CHD has been attributed not only to protein-coding Hsa21 genes, but also to genes on other chromosomes, as well as miRNAs and lncRNAs. It is likely that the contribution of more than one gene is required, and that the overexpression of Hsa21 genes acts in combination with other genetic events, such as specific mutations or polymorphisms, amplifying their effect. Moreover, a key function in determining alterations in cardiac morphogenesis might be played by ECM. A large number of genes encoding ECM proteins are overexpressed in trisomic human fetal hearts, and many of them appear to be under the control of a Hsa21 gene, the RUNX1 transcription factor.

Overexpression of the Hsa21 Transcription Factor RUNX1 Modulates the Extracellular Matrix in Trisomy 21 Cells

Down syndrome is a neurodevelopmental disorder frequently characterized by other developmental defects, such as congenital heart disease. Analysis of gene expression profiles of hearts from trisomic fetuses have shown upregulation of extracellular matrix (ECM) genes. The aim of this work was to identify genes on chromosome 21 potentially responsible for the upregulation of ECM genes and to pinpoint any functional consequences of this upregulation. By gene set enrichment analysis of public data sets, we identified the transcription factor RUNX1, which maps to chromosome 21, as a possible candidate for regulation of ECM genes. We assessed that approximately 80% of ECM genes overexpressed in trisomic hearts have consensus sequences for RUNX1 in their promoters. We found that in human fetal fibroblasts with chromosome 21 trisomy there is increased expression of both RUNX1 and several ECM genes, whether located on chromosome 21 or not. SiRNA silencing of RUNX1 reduced the expression of 11 of the 14 ECM genes analyzed. In addition, collagen IV, an ECM protein secreted in high concentrations in the culture media of trisomic fibroblasts, was modulated by RUNX1 silencing. Attenuated expression of RUNX1 increased the migratory capacity of trisomic fibroblasts, which are characterized by a reduced migratory capacity compared to euploid controls.

Cre/LoxP Genetic Recombination Sustains Cartilage Anabolic Factor Expression in Hyaluronan Encapsulated MSCs Alleviates Intervertebral Disc Degeneration

(1) Background: Inexplicable low back and neck pain frequently results from spinal disc degeneration with an imbalanced intervertebral disc (IVD) cell homeostasis. We hypothesize that introducing MSC expressing a sustained cartilage-anabolic factor in the IVD may stimulate the mucoid materials secreted from the IVD cells, promote the MSC’s chondrogenesis and maintain the hydration content providing mechanical strength to decelerate the disc degeneration progression; (2) Methods: This study expressed a cartilage-anabolic factor runx1 by a baculoviral vector (BV) transduced MSCs through a Cre/LoxP gene editing and recombination system for sustained recombinant runx1 transcription factor production. The Cre/LoxP BV modified MSCs were encapsulated by hyaluronan hydrogel, due to its’ vital composition in ECM of a healthy disc and transplanted to a punctured coccygeal disc in rats through micro-injection, followed by X-ray radiography and histological analysis at the 4- and 12-weeks post-transplantation; (3) Results: Data reveals the Cre/LoxP BV system-mediated long-termed runx1 gene expression, possessing good biosafety characteristics in the in vitro cell transduction and in vivo MSCs transplantation, and maintained superior hydration content in the disc than that of mock transduced MSCs; (4) Conclusions: This proof-of-concept study fulfills the need of implanting therapeutic cells accompanied with microinjection in the disc, such as a discography and paves a road to manufacture composite hyaluronan, such as peptide modified hyaluronan as an MSC carrier for IVD regeneration in the future study.

Runx1 Messenger RNA Delivered by Polyplex Nanomicelles Alleviate Spinal Disc Hydration Loss in a Rat Disc Degeneration Model

Vertebral disc degenerative disease (DDD) affects millions of people worldwide and is a critical factor leading to low back and neck pain and consequent disability. Currently, no strategy has addressed curing DDD from fundamental aspects, because the pathological mechanism leading to DDD is still controversial. One possible mechanism points to the homeostatic status of extracellular matrix (ECM) anabolism, and catabolism in the disc may play a vital role in the disease’s progression. If the damaged disc receives an abundant amount of cartilage, anabolic factors may stimulate the residual cells in the damaged disc to secrete the ECM and mitigate the degeneration process. To examine this hypothesis, a cartilage anabolic factor, Runx1, was expressed by mRNA through a sophisticated polyamine-based PEG-polyplex nanomicelle delivery system in the damaged disc in a rat model. The mRNA medicine and polyamine carrier have favorable safety characteristics and biocompatibility for regenerative medicine. The endocytosis of mRNA-loaded polyplex nanomicelles in vitro, mRNA delivery efficacy, hydration content, disc shrinkage, and ECM in the disc in vivo were also examined. The data revealed that the mRNA-loaded polyplex nanomicelle was promptly engulfed by cellular late endosome, then spread into the cytosol homogeneously at a rate of less than 20 min post-administration of the mRNA medicine. The mRNA expression persisted for at least 6-days post-injection in vivo. Furthermore, the Runx1 mRNA delivered by polyplex nanomicelles increased hydration content by ≈43% in the punctured disc at 4-weeks post-injection (wpi) compared with naked Runx1 mRNA administration. Meanwhile, the disc space and ECM production were also significantly ameliorated in the polyplex nanomicelle group. This study demonstrated that anabolic factor administration by polyplex nanomicelle-protected mRNA medicine, such as Runx1, plays a key role in alleviating the progress of DDD, which is an imbalance scenario of disc metabolism. This platform could be further developed as a promising strategy applied to regenerative medicine.

Chitosan/polycaprolactone multilayer hydrogel: A sustained Kartogenin delivery model for cartilage regeneration

Cartilage regeneration using biomaterial-guided delivery systems presents improved therapeutic efficacy of the biomolecules while minimizing side effects. Here, our hypothesis was to design a multilayer scaffold of chitosan (CS) hydrogel and polycaprolactone (PCL) mat to enhance the mechanical properties, integrity and stability of CS, especially for subsequent in vivo transplantation. After conjugation of the Kartogenin (KGN) into this structure, its gradual release can promote chondrogenesis of mesenchymal stem cells (MSCs). Initially, a thin electrospun PCL layer was sandwiched between two CS hydrogels. Subsequently, KGN was superficially immobilized onto the CS matrix. The successful conjugation was confirmed by scanning electron microscopy (SEM) and infrared spectroscopy. These novel KGN-conjugated scaffolds possessed lower swelling and higher compressive modulus and showed gradual release of KGN in longer retention times. Immunofluorescent and histological staining represented more cells located in lacunae as well as more Coll2 and Sox9 positive cells on KGN-conjugated scaffolds. Gene expression analysis also revealed that SOX9, COLL2 and ACAN expression levels were higher in the presence of KGN, while COLLX expression was down-regulated, indicating a hypertrophy phenomenon with synergistic effect of TGF-β. This multilayer structure not only facilitates the effective treatment, but also provides a proper mechanical structure for cartilage engineering.

Oncogenic gene RGC-32 is a direct target of miR-26b and facilitates tongue squamous cell carcinoma aggressiveness through EMT and PI3K/AKT signalling

Growing data have recognized the significance of Response Gene to Complement (RGC)-32 in numerous tumour developments. Notwithstanding, the functional role and underlying mechanism of it in tongue squamous cell carcinoma (TSCC) remain enigmatic. Here, to identify the impact of RGC-32 in TSCC, its expression in multiple TSCC cells was measured and loss-of-function experiments in cell lines were performed to illuminate the function of it induced TSCC progression, via si-RNA knockdown, CCK-8, colony formation, wound-healing, transwell, flow cytometry and western blot assays. To clarify potential mechanism, expressions of hallmarks in epithelial-mesenchymal transition (EMT) process and PI3K/AKT signalling were assessed, and the upstream miR regulator of RGC-32 was predicted and verified by applying bioinformatic approaches and dual-luciferase reporter assay, respectively. Finally, the rescue experiments were applied to better elucidate the effect of miR-26b/RGC-32 axis in TSCC behaviours. As a result, RGC-32 was upregulated in TSCC cells and knocking down of it abrogated cell proliferation, trans-migration and invasion, whilst promoted apoptosis in TSCC, which was regulated through repressing EMT and inactivation of PI3K/AKT signalling. Subsequently, miR-26b was predicted and identified as an upstream regulator of RGC-32, and the pro-tumorigenic effect of RGC-32 was reversed by miR-26b overexpression. Collectively, our results demonstrated that RGC-32 facilitated TSCC progression, which was modulated by activations of PI3K/AKT pathway and EMT process, and reduction of its negative regulator of miR-26b. These findings highlight a novel role of miR-26b/RGC-32 axis in TSCC and underlying mechanism, encouraging a potent usage in TSCC treatment. SIGNIFICANCE OF THE STUDY: We first uncovered that Response Gene to Complement-32 played a significantly pro-tumorigenic role in tongue squamous cell carcinoma (TSCC), which was closely regulated by downregulation of miR-26b and activations of epithelial-mesenchymal transition process and PI3K/AKT signalling. These findings contribute to better understand the molecular mechanism in carcinogenesis of TSCC, and shed some light on promising strategy for TSCC therapeutics.

Collaboration of MYC and RUNX2 in lymphoma simulates T-cell receptor signaling and attenuates p53 pathway activity

MYC and RUNX oncogenes each trigger p53‐mediated failsafe responses when overexpressed in vitro and collaborate with p53 deficiency in vivo. However, together they drive rapid onset lymphoma without mutational loss of p53. This phenomenon was investigated further by transcriptomic analysis of premalignant thymus from RUNX2/MYC transgenic mice. The distinctive contributions of MYC and RUNX to transcriptional control were illustrated by differential enrichment of canonical binding sites and gene ontology analyses. Pathway analysis revealed signatures of MYC, CD3, and CD28 regulation indicative of activation and proliferation, but also strong inhibition of cell death pathways. In silico analysis of discordantly expressed genes revealed Tnfsrf8/CD30, Cish, and Il13 among relevant targets for sustained proliferation and survival. Although TP53 mRNA and protein levels were upregulated, its downstream targets in growth suppression and apoptosis were largely unperturbed. Analysis of genes encoding p53 posttranslational modifiers showed significant upregulation of three genes, Smyd2, Set, and Prmt5. Overexpression of SMYD2 was validated in vivo but the functional analysis was constrained by in vitro loss of p53 in RUNX2/MYC lymphoma cell lines. However, an early role is suggested by the ability of SMYD2 to block senescence‐like growth arrest induced by RUNX overexpression in primary fibroblasts.

RUNX family: Oncogenes or tumor suppressors (Review)

Runt-related transcription factor (RUNX) proteins belong to a transcription factors family known as master regulators of important embryonic developmental programs. In the last decade, the whole family has been implicated in the regulation of different oncogenic processes and signaling pathways associated with cancer. Furthermore, a suppressor tumor function has been also reported, suggesting the RUNX family serves key role in all different types of cancer. In this review, the known biological characteristics, specific regulatory abilities and experimental evidence of RUNX proteins will be analyzed to demonstrate their oncogenic potential and tumor suppressor abilities during oncogenic processes, suggesting their importance as biomarkers of cancer. Additionally, the importance of continuing with the molecular studies of RUNX proteins' and its dual functions in cancer will be underlined in order to apply it in the future development of specific diagnostic methods and therapies against different types of cancer.

Treatment of Intervertebral Disk Disease by the Administration of mRNA Encoding a Cartilage-Anabolic Transcription Factor

Intervertebral disk (IVD) degeneration is often associated with severity of lower back pain. IVD core is an avascular, highly hydrated tissue composed of type II collagen, glycosaminoglycans, and proteoglycans. The disk degeneration is not only a destruction of IVD structure but also is related to a disorder of the turnover of the disk matrix, leading the jelly-like IVD core to be replaced by fibrous components. Here we present a disease-modifying strategy for IVD degenerative diseases by direct regulation of the cells in the IVD using mRNA medicine, to alter the misbalanced homeostasis during disk degeneration. When mRNA encoding a cartilage-anabolic transcription factor, runt-related transcription factor-1, was administered to a rat model of coccygeal disk degeneration using a polyplex nanomicelle composed of polyethylene glycol-polyamino acid block copolymers and mRNA, the disk height was maintained to a significantly higher extent (≈81%) compared to saline control (69%), with prevention of fibrosis in the disk tissue. In addition, the use of nanomicelles effectively prevented inflammation, which was observed by injection of naked mRNA into the disk. This proof-of-concept study revealed that mRNA medicine has a potential for treating IVD degenerative diseases by introducing a cartilage-anabolic factor into the host cells, proposing a new therapeutic strategy using mRNA medicine.

Addiction to Runx1 is partially attenuated by loss of p53 in the Eµ-Myc lymphoma model

The Runx genes function as dominant oncogenes that collaborate potently with Myc or loss of p53 to induce lymphoma when over-expressed. Here we examined the requirement for basal Runx1 activity for tumor maintenance in the Eμ-Myc model of Burkitt's lymphoma. While normal Runx1^fl/fl lymphoid cells permit mono-allelic deletion, primary Eμ-Myc lymphomas showed selection for retention of both alleles and attempts to enforce deletion in vivo led to compensatory expansion of p53^null blasts retaining Runx1. Surprisingly, Runx1 could be excised completely from established Eμ-Myc lymphoma cell lines in vitro without obvious effects on cell phenotype. Established lines lacked functional p53, and were sensitive to death induced by introduction of a temperature-sensitive p53 (Val135) allele. Transcriptome analysis of Runx1-deleted cells revealed a gene signature associated with lymphoid proliferation, survival and differentiation, and included strong de-repression of recombination-activating (Rag) genes, an observation that was mirrored in a panel of human acute leukemias where RUNX1 and RAG1,2 mRNA expression were negatively correlated. Notably, despite their continued growth and tumorigenic potential, Runx1^null lymphoma cells displayed impaired proliferation and markedly increased sensitivity to DNA damage and dexamethasone-induced apoptosis, validating Runx1 function as a potential therapeutic target in Myc-driven lymphomas regardless of their p53 status.

Runx3 inhibits melanoma cell migration through regulation of cell shape change

The transcription factor Runx3 is a known tumor suppressor gene, and its expression is frequently lost in melanoma. However, the potential contribution of the loss of Runx3 expression to melanoma development and progression remains unclear. In this in vitro study, we demonstrated that ectopic Runx3 re-expression in B16-F10 melanoma cells changed the cell shape from elongated and branched to spread and unbranched, which enhanced stress fiber formation, increased the number of mature and fibrillar focal adhesions, and up-regulated fibronectin expression. In association with the cell shape change, the Runx3 re-expression in B16-F10 melanoma cells inhibited cell migration. Moreover, the phenotype of the Runx3 induced cell shape change was partially resembled when the melanoma cells were cultured on a fibronectin-coated coverslip, suggesting that fibronectin may mediate the Runx3 induced cell shape change of the melanoma cells. Taken together, our findings suggest that Runx3 may regulate cell shape to inhibit melanoma cell migration partly through enhancing stress fiber formation and ECM protein production. Our present study provides further evidence for the idea that cell shape change is potentially correlated with melanoma development and progression.

Runx1 Orchestrates Sphingolipid Metabolism and Glucocorticoid Resistance in Lymphomagenesis

The three‐membered RUNX gene family includes RUNX1, a major mutational target in human leukemias, and displays hallmarks of both tumor suppressors and oncogenes. In mouse models, the Runx genes appear to act as conditional oncogenes, as ectopic expression is growth suppressive in normal cells but drives lymphoma development potently when combined with over‐expressed Myc or loss of p53. Clues to underlying mechanisms emerged previously from murine fibroblasts where ectopic expression of any of the Runx genes promotes survival through direct and indirect regulation of key enzymes in sphingolipid metabolism associated with a shift in the “sphingolipid rheostat” from ceramide to sphingosine‐1‐phosphate (S1P). Testing of this relationship in lymphoma cells was therefore a high priority. We find that ectopic expression of Runx1 in lymphoma cells consistently perturbs the sphingolipid rheostat, whereas an essential physiological role for Runx1 is revealed by reduced S1P levels in normal spleen after partial Cre‐mediated excision. Furthermore, we show that ectopic Runx1 expression confers increased resistance of lymphoma cells to glucocorticoid‐mediated apoptosis, and elucidate the mechanism of cross‐talk between glucocorticoid and sphingolipid metabolism through Sgpp1. Dexamethasone potently induces expression of Sgpp1 in T‐lymphoma cells and drives cell death which is reduced by partial knockdown of Sgpp1 with shRNA or direct transcriptional repression of Sgpp1 by ectopic Runx1. Together these data show that Runx1 plays a role in regulating the sphingolipid rheostat in normal development and that perturbation of this cell fate regulator contributes to Runx‐driven lymphomagenesis. J. Cell. Biochem. 118: 1432–1441, 2017. © 2016 The Authors. Journal of Cellular Biochemistry Published by Wiley Periodicals, Inc.

The RUNX Genes as Conditional Oncogenes: Insights from Retroviral Targeting and Mouse Models

The observation that the Runx genes act as targets for transcriptional activation by retroviral insertion identified a new family of dominant oncogenes. However, it is now clear that Runx genes are 'conditional' oncogenes whose over-expression is growth inhibitory unless accompanied by another event such as concomitant over-expression of MYC or loss of p53 function. Remarkably, while the oncogenic activities of either MYC or RUNX over-expression are suppressed while p53 is intact, the combination of both neutralises p53 tumour suppression in vivo by as yet unknown mechanisms. Moreover, there is emerging evidence that endogenous, basal RUNX activity is important to maintain the viability and proliferation of MYC-driven lymphoma cells. There is also growing evidence that the human RUNX genes play a similar conditional oncogenic role and are selected for over-expression in end-stage cancers of multiple types. Paradoxically, reduced RUNX activity can also predispose to cell immortalisation and transformation, particularly by mutant Ras. These apparently conflicting observations may be reconciled in a stage-specific model of RUNX involvement in cancer. A question that has yet to be fully addressed is the extent to which the three Runx genes are functionally redundant in cancer promotion and suppression.

AML1/ETO accelerates cell migration and impairs cell-to-cell adhesion and homing of hematopoietic stem/progenitor cells

The AML1/ETO fusion protein found in acute myeloid leukemias functions as a transcriptional regulator by recruiting co-repressor complexes to its DNA binding site. In order to extend the understanding of its role in preleukemia, we expressed AML1/ETO in a murine immortalized pluripotent hematopoietic stem/progenitor cell line, EML C1, and found that genes involved in functions such as cell-to-cell adhesion and cell motility were among the most significantly regulated as determined by RNA sequencing. In functional assays, AML1/ETO-expressing cells showed a decrease in adhesion to stromal cells, an increase of cell migration rate in vitro, and displayed an impairment in homing and engraftment in vivo upon transplantation into recipient mice. Our results suggest that AML1/ETO expression determines a more mobile and less adherent phenotype in preleukemic cells, therefore altering the interaction with the hematopoietic niche, potentially leading to the migration across the bone marrow barrier and to disease progression.

Neonatal ventral hippocampus lesion changes nuclear restricted protein/brain (NRP/B) expression in hippocampus, cortex and striatum in developmental periods of rats

Schizophrenia is conceptualized as a neurodevelopmental disorder in which developmental alterations in immature brain systems are not clear. Rats with neonatal ventral hippocampal lesions (NVHL) can exhibit schizophrenia-like behaviors, and these rats have been widely used to study the developmental mechanisms of schizophrenia. The nuclear restricted protein/brain (NRP/B) is a nuclear matrix protein that is critical for the normal development of the neuronal system. This study assessed the effect of NVHL induced by the administration of ibotenic acid on the protein expression of NRP/B in the hippocampus, cortex and striatum in pre- and post-pubertal rats. The expressions of NeuN in various developmental periods were assessed accordingly. Sprague-Dawley rat pups were administered ibotenic acid at postnatal day (PD) 7. Western blotting and an immunofluorescence staining analysis showed that the expression of NRP/B was significantly decreased in the hippocampus, cortex and striatum of the NVHL rats at PD14, 28 and 42. The expressions of NeuN were decreased accordingly. In vitro experiment showed the NRP/B knockdown can decrease the Tuj1 expression in cultured cortical neurons. The data suggest that NVHL induces a change in NRP/B expression that affects neurons in the developmental period.

Photo-Cross-Linked Scaffold with Kartogenin-Encapsulated Nanoparticles for Cartilage Regeneration

The regeneration of cartilage, an aneural and avascular tissue, is often compromised by its lack of innate abilities to mount a sufficient healing response. Kartogenin (KGN), a small molecular compound, can induce bone marrow-derived mesenchymal stem cells (BMSCs) into chondrocytes. The previous in vitro study showed that kartogenin also had a chondrogenesis effect on synovium derived mesenchymal stem cells (SMSCs). Herein, we present the effect of an ultraviolet-reactive, rapidly cross-linkable scaffold integrated with kartogenin-loaded nanoparticles using an innovational one-step technology. In vivo studies showed its potential role for cell homing, especially for recruiting the host's endogenous cells, including BMSCs and SMSCs, without cell transplantation. Of note, the regenerated tissues were close to the natural hyaline cartilage based on the histological tests, specific markers analysis, and biomechanical tests. This innovative KGN release system makes the chondrogenesis efficient and persistent.

The emerging role of RUNX3 in cancer metastasis (Review)

Metastasis remains the major driver of mortality in patients with cancer. The multistep metastatic process starts with the dissemination of tumor cells from a primary site and leading to secondary tumor development in an anatomically distant location. Although significant progress has been made in understanding the molecular characteristics of metastasis, many questions remain regarding the intracellular mechanisms governing transition through the various metastatic stages. The runt-related transcription factor 3 (RUNX3) is a downstream effector of the transforming growth factor-β (TGF-β) signaling pathway, and has critical roles in the regulation of cell death by apoptosis, and in angiogenesis, epithelial-to-mesenchymal transition (EMT), cell migration and invasion. RUNX3 functions as a bona fide initiator of carcinogenesis by linking the Wnt oncogenic and TGF-β tumor suppressive pathways. RUNX3 is frequently inactivated in human cancer cell lines and cancer samples by hemizygous deletion of the Runx3 gene, hypermethylation of the Runx3 promoter, or cytoplasmic sequestration of RUNX3 protein. Inactivation of RUNX3 makes it a putative tumor suppressor in human neoplasia. In the present review, we summarize the proposed roles of RUNX3 in metastasis and, when applicable, highlight the mechanism by which they function.

Histone Deacetylase Inhibitors Repress Tumoral Expression of the Proinvasive Factor RUNX2

Aberrant reactivation of embryonic pathways occurs commonly in cancer. The transcription factor RUNX2 plays a fundamental role during embryogenesis and is aberrantly reactivated during progression and metastasization of different types of human tumors. In this study, we attempted to dissect the molecular mechanisms governing RUNX2 expression and its aberrant reactivation. We identified a new regulatory enhancer element, located within the RUNX2 gene, which is responsible for the activation of the RUNX2 promoter and for the regulation of its expression in cancer cells. Furthermore, we have shown that treatment with the anticancer compounds histone deacetylase inhibitor (HDACi) results in a profound inhibition of RUNX2 expression, which is determined by the disruption of the transcription-activating complex on the identified enhancer. These data envisage a possible targeting strategy to counteract the oncongenic function of RUNX2 in cancer cells and provide evidence that the cytotoxic activity of HDACi in cancer is not only dependent on the reactivation of silenced oncosuppressors but also on the repression of oncogenic factors that are necessary for survival and progression.

RGC-32 is a novel regulator of the T-lymphocyte cell cycle

We have previously shown that RGC-32 is involved in cell cycle regulation in vitro. To define the in vivo role of RGC-32, we generated RGC-32 knockout mice. These mice developed normally and did not spontaneously develop overt tumors. To assess the effect of RGC-32 deficiency on cell cycle activation in T cells, we determined the proliferative rates of CD4(+) and CD8(+) T cells from the spleens of RGC-32(-/-) mice, as compared to wild-type (WT, RGC-32(+/+)) control mice. After stimulation with anti-CD3/anti-CD28, CD4(+) T cells from RGC-32(-/-) mice displayed a significant increase in [(3)H]-thymidine incorporation when compared to WT mice. In addition, both CD4(+) and CD8(+) T cells from RGC-32(-/-) mice displayed a significant increase in the proportion of proliferating Ki67(+) cells, indicating that in T cells, RGC-32 has an inhibitory effect on cell cycle activation induced by T-cell receptor/CD28 engagement. Furthermore, Akt and FOXO1 phosphorylation induced in stimulated CD4(+) T-cells from RGC-32(-/-) mice were significantly higher, indicating that RGC-32 inhibits cell cycle activation by suppressing FOXO1 activation. We also found that IL-2 mRNA and protein expression were significantly increased in RGC-32(-/-) CD4(+) T cells when compared to RGC-32(+/+) CD4(+) T cells. In addition, the effect of RGC-32 on the cell cycle and IL-2 expression was inhibited by pretreatment of the samples with LY294002, indicating a role for phosphatidylinositol 3-kinase (PI3K). Thus, RGC-32 is involved in controlling the cell cycle of T cells in vivo, and this effect is mediated by IL-2 in a PI3K-dependent fashion.

Mesenchymal stromal cells and rheumatic diseases: new tools from pathogenesis to regenerative therapies

In recent years, mesenchymal stromal cells (MSCs) have been largely investigated and tested as a new therapeutic tool for several clinical applications, including the treatment of different rheumatic diseases. MSCs are responsible for the normal turnover and maintenance of adult mesenchymal tissues as the result of their multipotent differentiation abilities and their secretion of a variety of cytokines and growth factors. Although initially derived from bone marrow, MSCs are present in many different tissues such as many peri-articular tissues. MSCs may exert immune-modulatory properties, modulating different immune cells in both in vitro and in vivo models, and they are considered immune-privileged cells. At present, these capacities are considered the most intriguing aspect of their biology, introducing the possibility that these cells may be used as effective therapy in autoimmune diseases. Therefore, stem cell therapies may represent an innovative approach for the treatment of rheumatic diseases, especially for the forms that are not responsive to standard treatments or alternatively still lacking a definite therapy. At present, although the data from scientific literature appear to suggest that such treatments might be more effective whether administered as soon as possible, the use of MSCs in clinical practice is likely to be restricted to patients with a long history of a severe refractory disease. Further results from larger clinical trials are needed to corroborate preclinical findings and human non-controlled studies, and advancement in the knowledge of MSCs might provide information about the therapeutic role of these cells in the treatment of many rheumatic diseases.

The Nuclear Matrix Protein, NRP/B, Acts as a Transcriptional Repressor of E2F-mediated Transcriptional Activity

Background:

NRP/B, a family member of the BTB/Kelch repeat proteins, is implicated in neuronal and cancer development, as well as the regulation of oxidative stress responses in breast and brain cancer. Our previous studies indicate that the NRP/B-BTB/POZ domain is involved in the dimerization of NRP/B and in a complex formation with the tumor suppressor, retinoblastoma protein. Although much evidence supports the potential role of NRP/B as a tumor suppressor, the molecular mechanisms of NRP/B action on E2F transcription factors have not been elucidated.

Methods:

Three-dimensional modeling of NRP/B was used to generate point mutations in the BTB/Kelch domains. Tet-on inducible NRP/B expression was established. The NRP/B deficient breast cancer cell line, MDA-MB-231, was generated using lentiviral shNRP/B to evaluate the effect of NRP/B on cell proliferation, invasion and migration. Immunoprecipitation was performed to verify the interaction of NRP/B with E2F and histone deacetylase (HDAC-1), and the expression level of NRP/B protein was analyzed by Western blot analysis. Changes in cell cycle were determined by flow cytometry. Transcriptional activities of E2F transcription factors were measured by chloramphenicol acetyltransferase (CAT) activity.

Results:

Ectopic overexpression of NRP/B demonstrated that the NRP/B-BTB/POZ domain plays a critical role in E2F-mediated transcriptional activity. Point mutations within the BTB/POZ domain restored E2-promoter activity inhibited by NRP/B. Loss of NRP/B enhanced the proliferation and migration of breast cancer cells. Endogenous NRP/B interacted with E2F and HDAC1. Treatement with an HDAC inhibitor, trichostatin A (TSA), abolished the NRP/B-mediated suppression of E2-promoter activity. Gain or loss of NRP/B in HeLa cells confirmed the transcriptional repressive capability of NRP/B on the E2F target genes, Cyclin E and HsORC (Homo sapiens Origin Recognition Complex).

Conclusions:

The present study shows that NRP/B acts as a transcriptional repressor by interacting with the co-repressors, HDAC1, providing new insight into the molecular mechanisms of NRP/B on tumor suppression.

Predicting interactome network perturbations in human cancer: application to gene fusions in acute lymphoblastic leukemia

Genomic variations such as gene fusions are directly or indirectly associated with human diseases. A method is presented combining gene expression and interactome data analyses to identify specific targets in leukemia. The Myc network and the mRNA export machinery are perturbed in ETV6-RUNX1 and TCF3-PBX1 subtypes of leukemia.

Genomic variations such as point mutations and gene fusions are directly or indirectly associated with human diseases. They are recognized as diagnostic, prognostic markers and therapeutic targets. However, predicting the functional effect of these genetic alterations beyond affected genes and their products is challenging because diseased phenotypes are likely dependent of complex molecular interaction networks. Using as models three different chromosomal translocations—ETV6-RUNX1 (TEL-AML1), BCR-ABL1, and TCF3-PBX1 (E2A-PBX1)—frequently found in precursor-B-cell acute lymphoblastic leukemia (preB-ALL), we develop an approach to extract perturbed molecular interactions from gene expression changes. We show that the MYC and JunD transcriptional circuits are specifically deregulated after ETV6-RUNX1 and TCF3-PBX1 gene fusions, respectively. We also identified the bulk mRNA NXF1-dependent machinery as a direct target for the TCF3-PBX1 fusion protein. Through a novel approach combining gene expression and interactome data analysis, we provide new insight into TCF3-PBX1 and ETV6-RUNX1 acute lymphoblastic leukemia.

Cytoskeletal regulatory gene expression and migratory properties of B-cell progenitors are affected by the ETV6-RUNX1 rearrangement

Although the ETV6-RUNX1 fusion is a frequent initiating event in childhood leukemia, its role in leukemogenesis is only partly understood. The main impact of the fusion itself is to generate and sustain a clone of clinically silent preleukemic B-cell progenitors (BCP). Additional oncogenic hits, occurring even several years later, are required for overt disease. The understanding of the features and interactions of ETV6-RUNX1-positive cells during this "latency" period may explain how these silent cells can persist and whether they could be prone to additional genetic changes. In this study, two in vitro murine models were used to investigate whether ETV6-RUNX1 alters the cellular adhesion and migration properties of BCP. ETV6-RUNX1-expressing cells showed a significant defect in the chemotactic response to CXCL12, caused by a block in CXCR4 signaling, as demonstrated by inhibition of CXCL12-associated calcium flux and lack of ERK phosphorylation. Moreover, the induction of ETV6-RUNX1 caused changes in the expression of cell-surface adhesion molecules. The expression of genes regulating the cytoskeleton was also affected, resulting in a block of CDC42 signaling. The abnormalities described here could alter the interaction of ETV6-RUNX1 preleukemic BCP with the microenvironment and contribute to the pathogenesis of the disease.

IMPLICATIONS

Alterations in the expression of cytoskeletal regulatory genes and migration properties of BCP represent early events in the evolution of the disease, from the preleukemic phase to the clinical onset, and suggest new strategies for effective eradication of leukemia.

Blocking ETV6/RUNX1-induced MDM2 overexpression by Nutlin-3 reactivates p53 signaling in childhood leukemia

ETV6/RUNX1 (E/R) is the most common fusion gene in childhood acute lymphoblastic leukemia. It is responsible for the initiation of leukemia but also indispensable for disease maintenance and propagation, although its function in these latter processes is less clear. We therefore investigated the effects of the perceived p53 pathway alterations in model cell lines and primary leukemias and, in particular, how E/R upregulates MDM2, the predominant negative regulator of p53. We found that E/R transactivates MDM2 in both p53(+/+) and p53(-/-) HCT116 cells by binding to promoter-inherent RUNX1 motifs, which indicates that this activation occurs in a direct and p53-independent manner. Treatment of E/R-positive leukemic cell lines with Nutlin-3, a small molecule that inhibits the MDM2/p53 interaction, arrests their cell cycle and induces apoptosis. These phenomena concur with a p53-induced expression of p21, pro-apoptotic BAX and PUMA, as well as caspase 3 activation and poly ADP-ribose polymerase cleavage. The addition of DNA-damaging and p53-activating chemotherapeutic drugs intensifies apoptosis. Moreover, Nutlin-3 exposure leads to an analogous p53 accumulation and apoptotic surge in E/R-positive primary leukemic cells. Our findings clarify the role of p53 signaling in E/R-positive leukemias and outline the potential basis for its therapeutic exploitation in this setting.

The many faces of C/EBPδ and their relevance for inflammation and cancer

The CCAAT/enhancer binding protein delta (CEBPD, C/EBPδ) is a transcription factor that modulates many biological processes including cell differentiation, motility, growth arrest, proliferation, and cell death. The diversity of C/EBPδ's functions depends in part on the cell type and cellular context and can have opposing outcomes. For example, C/EBPδ promotes inflammatory signaling, but it can also inhibit pro-inflammatory pathways, and in a mouse model of mammary tumorigenesis, C/EBPδ reduces tumor incidence but promotes tumor metastasis. This review highlights the multifaceted nature of C/EBPδ's functions, with an emphasis on pathways that are relevant for cancer and inflammation, and illustrates how C/EBPδ emerged from the shadow of its family members as a fascinating “jack of all trades.” Our current knowledge on C/EBPδ indicates that, rather than being essential for a specific cellular process, C/EBPδ helps to interpret a variety of cues in a cell-type and context-dependent manner, to adjust cellular functions to specific situations. Therefore, insights into the roles and mechanisms of C/EBPδ signaling can lead to a better understanding of how the integration of different signaling pathways dictates normal and pathological cell functions and physiology.

Mesenchymal stem cells in joint disease and repair. Nat Rev Rheumatol. 2013;9:584-594. [PMID: 23881068 DOI: 10.1038/nrrheum.2013.109]

Osteoarthritis (OA), a prevalent chronic condition with a striking impact on quality of life, represents an enormous societal burden that increases greatly as populations age. Yet no approved pharmacological intervention, biologic therapy or procedure prevents the progressive destruction of the OA joint. Mesenchymal stem cells (MSCs)-multipotent precursors of connective tissue cells that can be isolated from many adult tissues, including those of the diarthrodial joint-have emerged as a potential therapy. Endogenous MSCs contribute to maintenance of healthy tissues by acting as reservoirs of repair cells or as immunomodulatory sentinels to reduce inflammation. The onset of degenerative changes in the joint is associated with aberrant activity or depletion of these cell reservoirs, leading to loss of chondrogenic potential and preponderance of a fibrogenic phenotype. Local delivery of ex vivo cultures of MSCs has produced promising outcomes in preclinical models of joint disease. Mechanistically, paracrine signalling by MSCs might be more important than differentiation in stimulating repair responses; thus, paracrine factors must be assessed as measures of MSC therapeutic potency, to replace traditional assays based on cell-surface markers and differentiation. Several early-stage clinical trials, initiated or underway in 2013, are testing the delivery of MSCs as an intra-articular injection into the knee, but optimal dose and vehicle are yet to be established.

The RUNX family in breast cancer: relationships with estrogen signaling

The three RUNX family members are lineage specific master regulators, which also have important, context-dependent roles in carcinogenesis as either tumor suppressors or oncogenes. Here we review evidence for such roles in breast cancer (BCa). RUNX1, the predominant RUNX family member in breast epithelial cells, has a tumor suppressor role reflected by many somatic mutations found in primary tumor biopsies. The classical tumor suppressor gene RUNX3 does not consist of such a mutation hot spot, but it too seems to inhibit BCa; it is often inactivated in human BCa tumors and its haploinsufficiency in mice leads to spontaneous BCa development. The tumor suppressor activities of RUNX1 and RUNX3 are mediated in part by antagonism of estrogen signaling, a feature recently attributed to RUNX2 as well. Paradoxically, however RUNX2, a master osteoblast regulator, has been implicated in various aspects of metastasis in general and bone metastasis in particular. Reciprocating the anti-estrogenic tumor suppressor activity of RUNX proteins, inhibition of RUNX2 by estrogens may help explain their context-dependent anti-metastatic roles. Such roles are reserved to non-osseous metastasis, because ERα is associated with increased, not decreased skeletal dissemination of BCa cells. Finally, based on diverse expression patterns in BCa subtypes, the successful use of future RUNX-based therapies will most likely require careful patient selection.

PIM kinase isoform specific regulation of MIG6 expression and EGFR signaling in prostate cancer cells

The PIM family of oncogenic serine/threonine kinases regulates tumour cell proliferation. To identify proliferative signaling pathways that are regulated by PIM kinases we analyzed gene expression differences in DU-145 and PC3 prostate cancer derived cells induced by treatment with the recently developed highly selective PIM kinase inhibitor M-110. This identified 97 genes the expression of which is affected by M-110 in both cell lines. We then focused on the M-110 induced up regulation of the MIG6 gene that encodes a negative regulator of EGFR signaling. Here we show that M-110 and the structurally unrelated PIM kinase inhibitor SGI-1776 up regulate MIG6 in DU-145 and PC3 cells. Knockdown of PIM-1 but not of PIM-2 or PIM-3 also up regulates MIG6 expression, which identifies MIG6 as a PIM-1 regulated gene. In agreement with the role of MIG6 protein as a negative regulator of EGFR signaling we found that M-110 treatment inhibits EGF induced EGFR activation and the activation of the downstream ERK MAPkinase pathway. The biological significance of these findings are demonstrated by the fact that co-treatment of DU-145 or PC3 cells with the EGFR tyrosine kinase inhibitor Gefitinib and M-110 or SGI-1776 has synergistic inhibitory effects on cell proliferation. These experiments define a novel biological function of PIM-1 as a co-regulator of EGFR signaling and suggest that PIM inhibitors may be used in combination therapies to increase the efficacy of EGFR tyrosine kinase inhibitors.

Silencing of ETV6/RUNX1 abrogates PI3K/AKT/mTOR signaling and impairs reconstitution of leukemia in xenografts

The ETV6/RUNX1 (E/R) gene fusion is generated by the t(12;21) and found in approximately 25% of childhood B-cell precursor acute lymphoblastic leukemia. In contrast to the overwhelming evidence that E/R is critical for the initiation of leukemia, its relevance for the maintenance of overt disease is less clear. To investigate this issue, we suppressed the endogenous E/R fusion protein with lentivirally transduced short hairpin RNA in the leukemia cell lines REH and AT-2, and found a distinct reduction of proliferation and cell survival. In line with the observed concurrent inactivation of the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway, pharmacological inhibition diminished the phosphorylation of AKT and ribosomal protein S6, and significantly increased the apoptosis rate in E/R-positive leukemias. Moreover, PI3K/mTOR inhibitors sensitized glucocorticoid-resistant REH cells to prednisolone, an observation of potential relevance for improving treatment of drug-resistant relapses. Of note, knockdown of the E/R fusion gene also severely impaired the repopulation capacity of REH cells in non-obese deficient/severe combined immunodeficient mice. Collectively, these data demonstrate that the E/R fusion protein activates the PI3K/AKT/mTOR pathway and is indispensible for disease maintenance. Importantly, these results provide a first rationale and justification for targeting the fusion gene and the PI3K/AKT/mTOR pathway therapeutically.

A stem cell-based approach to cartilage repair

Osteoarthritis (OA) is a degenerative joint disease that involves the destruction of articular cartilage and eventually leads to disability. Molecules that promote the selective differentiation of multipotent mesenchymal stem cells (MSCs) into chondrocytes may stimulate the repair of damaged cartilage. Using an image-based high-throughput screen, we identified the small molecule kartogenin, which promotes chondrocyte differentiation (median effective concentration = 100 nM), shows chondroprotective effects in vitro, and is efficacious in two OA animal models. Kartogenin binds filamin A, disrupts its interaction with the transcription factor core-binding factor β subunit (CBFβ), and induces chondrogenesis by regulating the CBFβ-RUNX1 transcriptional program. This work provides new insights into the control of chondrogenesis that may ultimately lead to a stem cell-based therapy for osteoarthritis.

Upregulation of the cell-cycle regulator RGC-32 in Epstein-Barr virus-immortalized cells

Epstein-Barr virus (EBV) is implicated in the pathogenesis of multiple human tumours of lymphoid and epithelial origin. The virus infects and immortalizes B cells establishing a persistent latent infection characterized by varying patterns of EBV latent gene expression (latency 0, I, II and III). The CDK1 activator, Response Gene to Complement-32 (RGC-32, C13ORF15), is overexpressed in colon, breast and ovarian cancer tissues and we have detected selective high-level RGC-32 protein expression in EBV-immortalized latency III cells. Significantly, we show that overexpression of RGC-32 in B cells is sufficient to disrupt G2 cell-cycle arrest consistent with activation of CDK1, implicating RGC-32 in the EBV transformation process. Surprisingly, RGC-32 mRNA is expressed at high levels in latency I Burkitt's lymphoma (BL) cells and in some EBV-negative BL cell-lines, although RGC-32 protein expression is not detectable. We show that RGC-32 mRNA expression is elevated in latency I cells due to transcriptional activation by high levels of the differentially expressed RUNX1c transcription factor. We found that proteosomal degradation or blocked cytoplasmic export of the RGC-32 message were not responsible for the lack of RGC-32 protein expression in latency I cells. Significantly, analysis of the ribosomal association of the RGC-32 mRNA in latency I and latency III cells revealed that RGC-32 transcripts were associated with multiple ribosomes in both cell-types implicating post-initiation translational repression mechanisms in the block to RGC-32 protein production in latency I cells. In summary, our results are the first to demonstrate RGC-32 protein upregulation in cells transformed by a human tumour virus and to identify post-initiation translational mechanisms as an expression control point for this key cell-cycle regulator.

The leukemia-specific fusion gene ETV6/RUNX1 perturbs distinct key biological functions primarily by gene repression

BACKGROUND

ETV6/RUNX1 (E/R) (also known as TEL/AML1) is the most frequent gene fusion in childhood acute lymphoblastic leukemia (ALL) and also most likely the crucial factor for disease initiation; its role in leukemia propagation and maintenance, however, remains largely elusive. To address this issue we performed a shRNA-mediated knock-down (KD) of the E/R fusion gene and investigated the ensuing consequences on genome-wide gene expression patterns and deducible regulatory functions in two E/R-positive leukemic cell lines.

FINDINGS

Microarray analyses identified 777 genes whose expression was substantially altered. Although approximately equal proportions were either up- (KD-UP) or down-regulated (KD-DOWN), the effects on biological processes and pathways differed considerably. The E/R KD-UP set was significantly enriched for genes included in the "cell activation", "immune response", "apoptosis", "signal transduction" and "development and differentiation" categories, whereas in the E/R KD-DOWN set only the "PI3K/AKT/mTOR signaling" and "hematopoietic stem cells" categories became evident. Comparable expression signatures obtained from primary E/R-positive ALL samples underline the relevance of these pathways and molecular functions. We also validated six differentially expressed genes representing the categories "stem cell properties", "B-cell differentiation", "immune response", "cell adhesion" and "DNA damage" with RT-qPCR.

CONCLUSION

Our analyses provide the first preliminary evidence that the continuous expression of the E/R fusion gene interferes with key regulatory functions that shape the biology of this leukemia subtype. E/R may thus indeed constitute the essential driving force for the propagation and maintenance of the leukemic process irrespective of potential consequences of associated secondary changes. Finally, these findings may also provide a valuable source of potentially attractive therapeutic targets.

Genome-wide screening in human growth plates during puberty in one patient suggests a role for RUNX2 in epiphyseal maturation

In late puberty, estrogen decelerates bone growth by stimulating growth plate maturation. In this study, we analyzed the mechanism of estrogen action using two pubertal growth plate specimens of one girl at Tanner stage B2 and Tanner stage B3. Histological analysis showed that progression of puberty coincided with characteristic morphological changes: a decrease in total growth plate height (P=0.002), height of the individual zones (P<0.001), and an increase in intercolumnar space (P<0.001). Microarray analysis of the specimens identified 394 genes (72% upregulated and 28% downregulated) that changed with the progression of puberty. Overall changes in gene expression were small (average 1.38-fold upregulated and 1.36-fold downregulated genes). The 394 genes mapped to 13 significantly changing pathways (P<0.05) associated with growth plate maturation (e.g. extracellular matrix, cell cycle, and cell death). We next scanned the upstream promoter regions of the 394 genes for the presence of evolutionarily conserved binding sites for transcription factors implicated in growth plate maturation such as estrogen receptor (ER), androgen receptor, ELK1, STAT5B, cyclic AMP response element (CREB), and RUNX2. High-quality motif sites for RUNX2 (87 genes), ELK1 (43 genes), and STAT5B (31 genes), but not ER, were evolutionarily conserved, indicating their functional relevance across primates. Moreover, we show that some of these sites are direct target genes of these transcription factors as shown by ChIP assays.

Hematopoietic stem cell emergence in the conceptus and the role of Runx1

Hematopoietic stem cells (HSCs) are functionally defined as cells that upon transplantation into irradiated or otherwise immunocompromised adult organisms provide long-term reconstitution of the entire hematopoietic system. They emerge in the vertebrate conceptus around midgestation. Genetic studies have identified a number of transcription factors and signaling molecules that act at the onset of hematopoiesis, and have begun to delineate the molecular mechanisms underlying the formation of HSCs. One molecule that has been a particularly useful marker of this developmental event in multiple species is Runx1 (also known as AML1, Pebp2alpha). Runx1 is a sequence-specific DNA-binding protein, that along with its homologues Runx2 and Runx3 and their shared non-DNA binding subunit CBFbeta, constitute a small family of transcription factors called core-binding factors (CBFs). Runx1 is famous for its role in HSC emergence, and notorious for its involvement in leukemia, as chromosomal rearrangements and inactivating mutations in the human RUNX1 gene are some of the most common events in de novo and therapy-related acute myelogenous leukemia, myelodysplastic syndrome and acute lymphocytic leukemia. Here we will review the role of Runx1 in HSC emergence in the mouse conceptus and describe some of the genetic pathways that operate upstream and downstream of this gene. Where relevant, we will include data obtained from other species and embryonic stem (ES) cell differentiation cultures.

Runx2 transcriptome of prostate cancer cells: insights into invasiveness and bone metastasis

Background

Prostate cancer (PCa) cells preferentially metastasize to bone at least in part by acquiring osteomimetic properties. Runx2, an osteoblast master transcription factor, is aberrantly expressed in PCa cells, and promotes their metastatic phenotype. The transcriptional programs regulated by Runx2 have been extensively studied during osteoblastogenesis, where it activates or represses target genes in a context-dependent manner. However, little is known about the gene regulatory networks influenced by Runx2 in PCa cells. We therefore investigated genome wide mRNA expression changes in PCa cells in response to Runx2.

Results

We engineered a C4-2B PCa sub-line called C4-2B/Rx2^dox, in which Doxycycline (Dox) treatment stimulates Runx2 expression from very low to levels observed in other PCa cells. Transcriptome profiling using whole genome expression array followed by in silico analysis indicated that Runx2 upregulated a multitude of genes with prominent cancer associated functions. They included secreted factors (CSF2, SDF-1), proteolytic enzymes (MMP9, CST7), cytoskeleton modulators (SDC2, Twinfilin, SH3PXD2A), intracellular signaling molecules (DUSP1, SPHK1, RASD1) and transcription factors (Sox9, SNAI2, SMAD3) functioning in epithelium to mesenchyme transition (EMT), tissue invasion, as well as homing and attachment to bone. Consistent with the gene expression data, induction of Runx2 in C4-2B cells enhanced their invasiveness. It also promoted cellular quiescence by blocking the G1/S phase transition during cell cycle progression. Furthermore, the cell cycle block was reversed as Runx2 levels declined after Dox withdrawal.

Conclusions

The effects of Runx2 in C4-2B/Rx2^dox cells, as well as similar observations made by employing LNCaP, 22RV1 and PC3 cells, highlight multiple mechanisms by which Runx2 promotes the metastatic phenotype of PCa cells, including tissue invasion, homing to bone and induction of high bone turnover. Runx2 is therefore an attractive target for the development of novel diagnostic, prognostic and therapeutic approaches to PCa management. Targeting Runx2 may prove more effective than focusing on its individual downstream genes and pathways.

Gene regulation by SMAR1: Role in cellular homeostasis and cancer

Changes in the composition of nuclear matrix associated proteins contribute to alterations in nuclear structure, one of the major phenotypes of malignant cancer cells. The malignancy-induced changes in this structure lead to alterations in chromatin folding, the fidelity of genome replication and gene expression programs. The nuclear matrix forms a scaffold upon which the chromatin is organized into periodic loop domains called matrix attachment regions (MAR) by binding to various MAR binding proteins (MARBPs). Aberrant expression of MARBPs modulates the chromatin organization and disrupt transcriptional network that leads to oncogenesis. Dysregulation of nuclear matrix associated MARBPs has been reported in different types of cancers. Some of these proteins have tumor specific expression and are therefore considered as promising diagnostic or prognostic markers in few cancers. SMAR1 (scaffold/matrix attachment region binding protein 1), is one such nuclear matrix associated protein whose expression is drastically reduced in higher grades of breast cancer. SMAR1 gene is located on human chromosome 16q24.3 locus, the loss of heterozygosity (LOH) of which has been reported in several types of cancers. This review elaborates on the multiple roles of nuclear matrix associated protein SMAR1 in regulating various cellular target genes involved in cell growth, apoptosis and tumorigenesis.

Runx regulation of sphingolipid metabolism and survival signaling

The Runx genes (Runx1, 2, and 3) regulate cell fate in development and can operate as either oncogenes or tumor suppressors in cancer. The oncogenic potential of ectopic Runx expression has been shown in transgenic mice that develop lymphoma in potent synergy with overexpressed Myc, and in established fibroblasts that display altered morphology and increased tumorigenicity. Candidate oncogenic functions of overexpressed Runx genes include resistance to apoptosis in response to intrinsic and extrinsic stresses. In a search for gene targets responsible for this aspect of Runx phenotype, we have identified three key enzymes in sphingolipid metabolism (Sgpp1, Ugcg, and St3gal5/Siat9) as direct targets for Runx transcriptional regulation in a manner consistent with survival and apoptosis resistance. Consistent with these changes in gene expression, mass spectrometric analysis showed that ectopic Runx reduces intracellular long-chain ceramides in NIH3T3 fibroblasts and elevated extracellular sphingosine 1 phosphate. Runx expression also opposed the activation of c-Jun-NH(2)-kinase and p38(MAPK), key mediators of ceramide-induced death, and suppressed the onset of apoptosis in response to exogenous tumor necrosis factor alpha. The survival advantage conferred by ectopic Runx could be partially recapitulated by exogenous sphingosine 1 phosphate and was accompanied by reduced phosphorylation of p38(MAPK). These results reveal a novel link between transcription factor oncogenes and lipid signaling pathways involved in cancer cell survival and chemoresistance.

Runx2 in normal tissues and cancer cells: A developing story

The Runx transcription factors are essential for mammalian development, most notably in the haematopoietic and osteogenic lineages. Runx1 and its binding partner, CBFbeta, are frequently targeted in acute leukaemia but evidence is accumulating that all three Runx genes may have a role to play in a wider range of cancers, either as tumour promoters or tumour suppressors. Whilst Runx2 is renowned for its role as a master regulator of bone development we discuss here its expression pattern and putative functions beyond this lineage. Furthermore, we review the evidence that RUNX2 promotes neoplastic development in haematopoietic lineages and in advanced mammary and prostate cancer.

The novel RUNX3/p33 isoform is induced upon monocyte-derived dendritic cell maturation and downregulates IL-8 expression

RUNX proteins are heterodimeric factors that play crucial roles during development and differentiation of cells of the immune system. The RUNX3 transcription factor controls lineage decisions during thymopoiesis and T-cell differentiation, and modulates myeloid cell effector functions. We now report the characterization of the human RUNX3/p33 isoform, generated by splicing out a Runt DNA-binding domain-encoding exon, and whose transcriptional activities differ from those of the prototypic RUNX3/p44 molecule. Unlike RUNX3/p44, RUNX3/p33 is induced upon maturation of monocyte-derived dendritic cells (MDDC), and is unable to transactivate the regulatory regions of the CD11a, CD11c and CD49e integrin genes. Overexpression of RUNX3/p33 in myeloid cell lines led to diminished expression of genes involved in inflammatory responses. Moreover, overexpression of RUNX3/p33 down-modulated the basal level of IL-8 production from immature monocyte-derived dendritic cells (MDDC). Besides, siRNA-mediated knock-down of RUNX3 led to diminished levels of IL-8 RNA in immature MDDC, and modulated the neutrophil-recruiting capacity of myeloid cell line supernatants. Since IL-8 promotes neutrophil chemotaxis and degranulation during inflammatory responses, and exerts mitogenic and angiogenic actions within tumor microenvironment, our results imply that myeloid RUNX3 expression regulates the recruitment of leukocytes towards inflammatory foci and might also contribute to human cancer progression.

RUNX2 transcription factor regulates gene expression in luteinizing granulosa cells of rat ovaries

The LH surge promotes terminal differentiation of follicular cells to become luteal cells. RUNX2 has been shown to play an important role in cell differentiation, but the regulation of Runx2 expression and its function in the ovary remain to be determined. The present study examined 1) the expression profile of Runx2 and its partner CBFbeta during the periovulatory period, 2) regulatory mechanisms of Runx2 expression, and 3) its potential function in the ovary. Runx2 expression was induced in periovulatory granulosa cells of human and rodent ovaries. RUNX2 and core binding factor-beta (CBFbeta) proteins in nuclear extracts and RUNX2 binding to a consensus binding sequence increased after human chorionic gonadotropin (hCG) administration. This in vivo up-regulation of Runx2 expression was recapitulated in vitro in preovulatory granulosa cells by stimulation with hCG. The hCG-induced Runx2 expression was reduced by antiprogestin (RU486) and EGF-receptor tyrosine kinase inhibitor (AG1478), indicating the involvement of EGF-signaling and progesterone-mediated pathways. We also found that in the C/EBPbeta knockout mouse ovary, Runx2 expression was reduced, indicating C/EBPbeta-mediated expression. Next, the function of RUNX2 was investigated by suppressing Runx2 expression by small interfering RNA in vitro. Runx2 knockdown resulted in reduced levels of mRNA for Rgc32, Ptgds, Fabp6, Mmp13, and Abcb1a genes. Chromatin immunoprecipitation analysis demonstrated the binding of RUNX2 in the promoter region of these genes, suggesting that these genes are direct downstream targets of RUNX2. Collectively, the present data indicate that the LH surge-induced RUNX2 is involved in various aspects of luteal function by directly regulating the expression of diverse luteal genes.

ETV6/RUNX1 abrogates mitotic checkpoint function and targets its key player MAD2L1

Approximately 25% of childhood B-cell precursor acute lymphoblastic leukemia have an ETV6/RUNX1 (E/R) gene fusion that results from a t(12;21). This genetic subgroup of leukemia is associated with near-triploidy, near-tetraploidy, and trisomy 21 as rather specific types of secondary changes. Here, we show that, unlike various controls, E/R-expressing Ba/F3 clones acquire a tetraploid karyotype on prolonged culture, corroborating the assumption that E/R may attenuate the mitotic checkpoint (MC). Consistent with this notion, E/R-expressing diploid murine and human cell lines have decreased proportions of cells with 4N DNA content and a lower mitotic index when treated with spindle toxins. Moreover, both RUNX1 and E/R regulate mitotic arrest-deficient 2 L1 (MAD2L1), an essential MC component, by binding to promoter-inherent RUNX1 sites, which results in down-regulation of MAD2L1 mRNA and protein in E/R-expressing cells. Forced expression of E/R also abolishes RUNX1-induced reporter activation, whereas E/R with a mutant DNA-binding site leads to only minor effects. Our data link for the first time E/R, MC, and MAD2L1 and provide new insights into the function of the E/R fusion gene product. Although tetraploidy is an almost exclusive feature of E/R-positive leukemias, its rarity within this particular subgroup implies that further yet unknown factors are required for its manifestation.

The role of nuclear organization in cancer

The functional significance of changes in nuclear structure and organization in transformed cells remains one of the most enigmatic questions in cancer biology. In this review, we discuss relationships between nuclear organization and transcription in terms of the three-dimensional arrangement of genes in the interphase cancer nucleus and the regulatory functions of nuclear matrix proteins. We also analyse the role of nuclear topology in the generation of gene fusions. We speculate that this type of multi-layered analysis will one day provide a framework for a more comprehensive understanding of the genetic origins of cancer and the identification of new therapeutic targets.

Epigenetic modifications induced by RGC-32 in colon cancer

First described as a cell cycle activator, RGC-32 is both an activator and a substrate for CDC2. Deregulation of RGC-32 expression has been detected in a wide variety of human cancers. We have now shown that RGC-32 is expressed in precancerous states, and its expression is significantly higher in adenomas than in normal colon tissue. The expression of RGC-32 was higher in advanced stages of colon cancer than in precancerous states or the initial stages of colon cancer. In order to identify the genes that are regulated by RGC-32, we used gene array analysis to investigate the effect of RGC-32 knockdown on gene expression in the SW480 colon cancer cell line. Of the 230 genes that were differentially regulated after RGC-32 knockdown, a group of genes involved in chromatin assembly were the most significantly regulated in these cells: RGC-32 knockdown induced an increase in acetylation of histones H2B lysine 5 (H2BK5), H2BK15, H3K9, H3K18, and H4K8. RGC-32 silencing was also associated with decreased expression of SIRT1 and decreased trimethylation of histone H3K27 (H3K27me3). In addition, RGC-32 knockdown caused a significantly higher percentage of SW480 cells to enter S phase and subsequently G2/M. These data suggest that RGC-32 may contribute to the development of colon cancer by regulating chromatin assembly.

Runt-related transcription factor 1 regulates luteinized hormone-induced prostaglandin-endoperoxide synthase 2 expression in rat periovulatory granulosa cells

Runt-related transcription factor 1 (RUNX1), a transcription factor, is transiently induced by the LH surge and regulates gene expression in periovulatory granulosa cells. Potential binding sites for RUNX are present in the 5'-flanking region of the Ptgs2 (prostaglandin-endoperoxide synthase 2) gene. Periovulatory Ptgs2 expression is essential for ovulation. In the present study, we investigated the role of RUNX1 in mediating the LH-induced expression of Ptgs2 in periovulatory granulosa cells. We first determined whether the suppression of Runx1 expression or activity affects Ptgs2 expression using cultured preovulatory granulosa cells isolated from immature rat ovaries primed with pregnant mare serum gonadotropin for 48 h. Knockdown of human chorionic gonadotropin-induced Runx1 expression by small interfering RNA or inhibition of endogenous RUNX activities by dominant-negative RUNX decreased human chorionic gonadotropin or agonist-stimulated Ptgs2 expression and transcriptional activity of Ptgs2 promoter reporter constructs. Results from chromatin immunoprecipitation assays revealed in vivo binding of endogenous RUNX1 to the Ptgs2 promoter region in rat periovulatory granulosa cells. Direct binding of RUNX1 to two RUNX-binding motifs in the Ptgs2 promoter region was confirmed by EMSA. The mutation of these two binding motifs resulted in decreased transcriptional activity of Ptgs2 promoter reporter constructs in preovulatory granulosa cells. Taken together, these findings provide experimental evidence that the LH-dependent induction of Ptgs2 expression results, in part, from RUNX1-mediated transactivation of the Ptgs2 promoter. The results of the present study assign potential significance for LH-induced RUNX1 in the ovulatory process via regulating Ptgs2 gene expression.