A role for Hox A5 in regulating angiogenesis and vascular patterning

MicroRNAs in Hepatocellular Carcinoma Pathogenesis: Insights into Mechanisms and Therapeutic Opportunities

Hepatocellular carcinoma (HCC) presents a significant global health burden, with alarming statistics revealing its rising incidence and high mortality rates. Despite advances in medical care, HCC treatment remains challenging due to late-stage diagnosis, limited effective therapeutic options, tumor heterogeneity, and drug resistance. MicroRNAs (miRNAs) have attracted substantial attention as key regulators of HCC pathogenesis. These small non-coding RNA molecules play pivotal roles in modulating gene expression, implicated in various cellular processes relevant to cancer development. Understanding the intricate network of miRNA-mediated molecular pathways in HCC is essential for unraveling the complex mechanisms underlying hepatocarcinogenesis and developing novel therapeutic approaches. This manuscript aims to provide a comprehensive review of recent experimental and clinical discoveries regarding the complex role of miRNAs in influencing the key hallmarks of HCC, as well as their promising clinical utility as potential therapeutic targets.

Role of HOX genes in cancer progression and their therapeutical aspects

HOX genes constitute a family of evolutionarily conserved transcription factors that play pivotal roles in embryonic development, tissue patterning, and cell differentiation. These genes are essential for the precise spatial and temporal control of body axis formation in vertebrates. In addition to their developmental functions, HOX genes have garnered significant attention for their involvement in various diseases, including cancer. Deregulation of HOX gene expression has been observed in numerous malignancies, where they can influence tumorigenesis, progression, and therapeutic responses. This review provides an overview of the diverse roles of HOX genes in development, disease, and potential therapeutic targets, highlighting their significance in understanding biological processes and their potential clinical implications.

Deciphering the emerging landscape of HOX genes in cardiovascular biology, atherosclerosis and beyond (Review)

Atherosclerosis, a dominant driving force underlying multiple cardiovascular events, is an intertwined and chronic inflammatory disease characterized by lipid deposition in the arterial wall, which leads to diverse cardiovascular problems. Despite unprecedented advances in understanding the pathogenesis of atherosclerosis and the substantial decline in cardiovascular mortality, atherosclerotic cardiovascular disease remains a global public health issue. Understanding the molecular landscape of atherosclerosis is imperative in the field of molecular cardiology. Recently, compelling evidence has shown that an important family of homeobox (HOX) genes endows causality in orchestrating the interplay between various cardiovascular biological processes and atherosclerosis. Despite seemingly scratching the surface, such insight into the realization of biology promises to yield extraordinary breakthroughs in ameliorating atherosclerosis. Primarily recapitulated herein are the contributions of HOX in atherosclerosis, including diverse cardiovascular biology, knowledge gaps, remaining challenges and future directions. A snapshot of other cardiovascular biological processes was also provided, including cardiac/vascular development, cardiomyocyte pyroptosis/apoptosis, cardiac fibroblast proliferation and cardiac hypertrophy, which are responsible for cardiovascular disorders. Further in‑depth investigation of HOX promises to provide a potential yet challenging landscape, albeit largely undetermined to date, for partially pinpointing the molecular mechanisms of atherosclerosis. A plethora of new targeted therapies may ultimately emerge against atherosclerosis, which is rapidly underway. However, translational undertakings are crucially important but increasingly challenging and remain an ongoing and monumental conundrum in the field.

Locational memory of macrovessel vascular cells is transcriptionally imprinted

Vascular pathologies show locational predisposition throughout the body; further insights into the transcriptomics basis of this vascular heterogeneity are needed. We analyzed transcriptomes from cultured endothelial cells and vascular smooth muscle cells from nine adult canine macrovessels: the aorta, coronary artery, vena cava, portal vein, femoral artery, femoral vein, saphenous vein, pulmonary vein, and pulmonary artery. We observed that organ-specific expression patterns persist in vitro, indicating that these genes are not regulated by blood flow or surrounding cell types but are likely fixed in the epigenetic memory. We further demonstrated the preserved location-specific expression of GATA4 protein in cultured cells and in the primary adult vessel. On a functional level, arterial and venous endothelial cells differed in vascular network morphology as the arterial networks maintained a higher complexity. Our findings prompt the rethinking of the extrapolation of results from single-origin endothelial cell systems.

Identification and validation of a novel HOX-related classifier signature for predicting prognosis and immune microenvironment in pediatric gliomas

Background: Pediatric gliomas (PGs) are highly aggressive and predominantly occur in young children. In pediatric gliomas, abnormal expression of Homeobox (HOX) family genes (HFGs) has been observed and is associated with the development and progression of the disease. Studies have found that overexpression or underexpression of certain HOX genes is linked to the occurrence and prognosis of gliomas. This aberrant expression may contribute to the dysregulation of important pathological processes such as cell proliferation, differentiation, and metastasis. This study aimed to propose a novel HOX-related signature to predict patients' prognosis and immune infiltrate characteristics in PGs. Methods: The data of PGs obtained from publicly available databases were utilized to reveal the relationship among abnormal expression of HOX family genes (HFGs), prognosis, tumor immune infiltration, clinical features, and genomic features in PGs. The HFGs were utilized to identify heterogeneous subtypes using consensus clustering. Then random forest-supervised classification algorithm and nearest shrunken centroid algorithm were performed to develop a prognostic signature in the training set. Finally, the signature was validated in an internal testing set and an external independent cohort. Results: Firstly, we identified HFGs significantly differentially expressed in PGs compared to normal tissues. The individuals with PGs were then divided into two heterogeneous subtypes (HOX-SI and HOX-SII) based on HFGs expression profiles. HOX-SII showed higher total mutation counts, lower immune infiltration, and worse prognosis than HOX-SI. Then, we constructed a HOX-related gene signature (including HOXA6, HOXC4, HOXC5, HOXC6, and HOXA-AS3) based on the cluster for subtype prediction utilizing random forest supervised classification and nearest shrunken centroid algorithm. The signature was revealed to be an independent prognostic factor for patients with PGs by multivariable Cox regression analysis. Conclusion: Our study provides a novel method for the prognosis classification of PGs. The findings also suggest that the HOX-related signature is a new biomarker for the diagnosis and prognosis of patients with PGs, allowing for more accurate survival prediction.

Hox genes are crucial regulators of periosteal stem cell identity

Periosteal stem and progenitor cells (PSPCs) are major contributors to bone maintenance and repair. Deciphering the molecular mechanisms that regulate their function is crucial for the successful generation and application of future therapeutics. Here, we pinpoint Hox transcription factors as necessary and sufficient for periosteal stem cell function. Hox genes are transcriptionally enriched in periosteal stem cells and their overexpression in more committed progenitors drives reprogramming to a naïve, self-renewing stem cell-like state. Crucially, individual Hox family members are expressed in a location-specific manner and their stem cell-promoting activity is only observed when the Hox gene is matched to the anatomical origin of the PSPC, demonstrating a role for the embryonic Hox code in adult stem cells. Finally, we demonstrate that Hoxa10 overexpression partially restores the age-related decline in fracture repair. Together, our data highlight the importance of Hox genes as key regulators of PSPC identity in skeletal homeostasis and repair.

HOXA Amplification Defines a Genetically Distinct Subset of Angiosarcomas

Angiosarcoma is a rare, devastating malignancy with few curative options for disseminated disease. We analyzed a recently published genomic data set of 48 angiosarcomas and noticed recurrent amplifications of HOXA-cluster genes in 33% of patients. HOXA genes are master regulators of embryonic vascular development and adult neovascularization, which provides a molecular rationale to suspect that amplified HOXA genes act as oncogenes in angiosarcoma. HOXA amplifications typically affected multiple pro-angiogenic HOXA genes and co-occurred with amplifications of CD36 and KDR, whereas the overall mutation rate in these tumors was relatively low. HOXA amplifications were found most commonly in angiosarcomas located in the breast and were rare in angiosarcomas arising in sun-exposed areas on the head, neck, face and scalp. Our data suggest that HOXA-amplified angiosarcoma is a distinct molecular subgroup. Efforts to develop therapies targeting oncogenic HOX gene expression in AML and other sarcomas may have relevance for HOXA-amplified angiosarcoma.

HOXA1, a breast cancer oncogene

More than 25 years ago, the first literature records mentioned HOXA1 expression in human breast cancer. A few years later, HOXA1 was confirmed as a proper oncogene in mammary tissue. In the following two decades, molecular data about the mode of action of the HOXA1 protein, the factors contributing to activate and maintain HOXA1 gene expression and the identity of its target genes have accumulated and provide a wider view on the association of this transcription factor to breast oncogenesis. Large-scale transcriptomic data gathered from wide cohorts of patients further allowed refining the relationship between breast cancer type and HOXA1 expression. Several recent reports have reviewed the connection between cancer hallmarks and the biology of HOX genes in general. Here we take HOXA1 as a paradigm and propose an extensive overview of the molecular data centered on this oncoprotein, from what its expression modulators, to the interactors contributing to its oncogenic activities, and to the pathways and genes it controls. The data converge to an intricate picture that answers questions on the multi-modality of its oncogene activities, point towards better understanding of breast cancer aetiology and thereby provides an appraisal for treatment opportunities.

Research progress on RNA‑binding proteins in breast cancer (Review)

Breast cancer is the most common malignancy among women, and the abnormal regulation of gene expression serves an important role in its occurrence and development. However, the molecular mechanisms underlying gene expression are highly complex and heterogeneous, and RNA-binding proteins (RBPs) are among the key regulatory factors. RBPs bind targets in an environment-dependent or environment-independent manner to influence mRNA stability and the translation of genes involved in the formation, progression, metastasis and treatment of breast cancer. Due to the growing interest in these regulators, the present review summarizes the most influential studies concerning RBPs associated with breast cancer to elucidate the role of RBPs in breast cancer and to assess how they interact with other key pathways to provide new molecular targets for the diagnosis and treatment of breast cancer.

The protective effect of HOXA5 on carotid atherosclerosis occurs by modulating the vascular smooth muscle cell phenotype

The phenotypic change of vascular smooth muscle cells (VSMCs) from a contractile to a synthetic form is a key player in atherogenic processes. Homeobox A5 (HOXA5), a transcription factor of the homeobox gene family, has been shown to regulate cell differentiation and morphogenesis. The present study was designed to clarify the involvement of HOXA5 in VSMC phenotypic transition in carotid atherosclerosis (CAS). Activated VSMCs in vitro and ApoE^-/- mice in vivo were employed to determine HOXA5's function. Results showed that both the mRNA and protein expression levels of HOXA5 were decreased in platelet-derived growth factor-BB (PDGF-BB)-induced VSMCs. Overexpression of HOXA5 suppressed VSMC conversion from a contractile to a synthetic type in the presence of PDGF-BB, as evidenced by increased contractile markers (calponin, α-SMA and SM22α) along with decreased synthetic markers (vimentin, PCNA and thrombospondin). PDGF-BB-induced proliferation and migration of VSMCs were recovered by HOXA5. Knockdown of HOXA5 had the opposite effect on VSMCs. In vivo, a CAS model was established using ApoE^-/- mice fed with a Western-type diet and placing a perivascular carotid collar. We observed a significant reduction in HOXA5 in the carotid arteries of CAS mice. Similar to the in vitro results, HOXA5 overexpression reduced neointimal hyperplasia and plaque formation and inhibited VSMC dedifferentiation and migration. Furthermore, PPARγ was also downregulated in vitro and in vivo, and its antagonist GW9662 reversed HOXA5-mediated inhibition of VSMC dedifferentiation and migration. In summary, we suggest that HOXA5 protects against CAS progression by inhibiting VSMC dedifferentiation through activation of PPARγ.

HOXA5 induces M2 macrophage polarization to attenuate carotid atherosclerosis by activating MED1

Macrophage polarization is of great importance in the formation of atherosclerotic plaque. Homeobox A5 (HOXA5), one of the homeobox transcription factors, has been revealed to be closely associated with macrophage phenotype switching. This study aims to investigate the role of HOXA5 in carotid atherosclerosis (CAS). Herein, the role of HOXA5 was explored in polarized RAW264.7 macrophages in vitro and ApoE^-/- mice in vivo. Interestingly, compared with that in M0 macrophages, both the mRNA and protein expression levels of HOXA5 were decreased in lipopolysaccharide (LPS)/interferon (IFN)-γ-induced M1 macrophages, while increased in IL-4-induced M2 macrophages. In addition, in the presence of IL-4, HOXA5-overexpressing RAW264.7 cells preferred to polarizing toward M2 phenotypes. Furthermore, we found that HOXA5 bound to the promoter region and activated the expression of mediator subunit 1 (MED1), a gene known to regulate macrophage differentiation. Knocking MED1 down inhibited HOXA5-enhanced M2 macrophage polarization. In vivo, the CAS model was induced in ApoE^-/- mouse fed with a Western-type diet and placed a perivascular carotid collar. Decreased mRNA and protein expressions of HOXA5 were observed in carotid arteries of CAS mice. Forced overexpression of HOXA5 reduced intimal hyperplasia and lipid accumulation in carotid vessels, and it also promoted the polarization of macrophages to M2 subtypes. The expression of MED1 was decreased in atherosclerotic carotid vessels, while HOXA5 overexpression restored its change. Collectively, HOXA5 in carotid arteries is involved in the macrophage M1/M2 switching in atherosclerotic plaque, which may be associated with its transcriptional regulation of MED1.

Hoxa10 mediates positional memory to govern stem cell function in adult skeletal muscle

Muscle stem cells (satellite cells) are distributed throughout the body and have heterogeneous properties among muscles. However, functional topographical genes in satellite cells of adult muscle remain unidentified. Here, we show that expression of Homeobox-A (Hox-A) cluster genes accompanied with DNA hypermethylation of the Hox-A locus was robustly maintained in both somite-derived muscles and their associated satellite cells in adult mice, which recapitulates their embryonic origin. Somite-derived satellite cells were clearly separated from cells derived from cranial mesoderm in Hoxa10 expression. Hoxa10 inactivation led to genomic instability and mitotic catastrophe in somite-derived satellite cells in mice and human. Satellite cell-specific Hoxa10 ablation in mice resulted in a decline in the regenerative ability of somite-derived muscles, which were unobserved in cranial mesoderm-derived muscles. Thus, our results show that Hox gene expression profiles instill the embryonic history in satellite cells as positional memory, potentially modulating region-specific pathophysiology in adult muscles.

New insights in the clinical implication of HOXA5 as prognostic biomarker in patients with colorectal cancer

BACKGROUND

Homeobox A5 (HOXA5) is a member of the HOX protein family which is involved in several carcinogenesis pathways, and is dysregulated in many cancer types. However, its expression and function in human colorectal cancer (CRC) is still largely unknown.

OBJECTIVE

This study aimed to evaluate HOXA5 expression in Tunisian patients with CRC in order to define new potential biomarker.

METHODS

An immunohistochemical labeling using an HOXA5 antibody was performed on 85 formalin fixed paraffin embedded specimens from patients with CRC. Six normal colon mucosa cases were used as controls.

RESULTS

HOXA5 expression showed a cytoplasmic staining in both tumor and stromal/endothelial cells. Loss or low HOXA5 expression was seen in tumor cells in 74/85 cases (87.06%) and in stromal/endothelial cells, in 77/85 (90.59%). In control group of normal colon mucosa HOXA5 was moderately expressed in all the cases. The abnormal expression, was significantly associated to lymph nodes metastasis in tumor cells (p= 0.043) and in stromal/endothelial cells (p= 0.024).

CONCLUSION

HOXA5 immunostaining results suggest the valuable role of this protein in colorectal carcinogenesis. Moreover, the association of lymph node metastasis to HOXA5 abnormal expression underlies its crucial role in colorectal cancer dissemination and prognosis.

An aging and p53 related marker: HOXA5 promoter methylation negatively correlates with mRNA and protein expression in old age

The process of aging has been associated with differential patterns of DNA methylation which relate to changes in gene expression. Hence, we aimed to identify genes with significant age-related methylation differences and to study their mRNA and protein expression profile. Genome-wide DNA methylation analysis was performed with the Illumina Infinium Methylation EPIC BeadChip Microarray on bisulfite-converted DNA prepared from monocytes derived from young (average age: 23.8 yrs) and old (average age: 81.5 yrs) volunteers that are separated by at least 50 years of age difference, n=4, respectively. Differentially methylated CpG sites were assigned to the associated genes and validated by deep sequencing analysis (n=20). Demonstrating an age-associated significant increase of methylation in the promoter region (p=1x10^-8), Homeobox A5 (HOXA5), also known to activate p53, emerged as an interesting candidate for further expression analyses by Realtime PCR, ELISA and Western Blot Analysis (n=30, respectively). Consistent with its hypermethylation we observed significant HOXA5 mRNA downregulation (p=0.0053) correlating with significant p53 downregulation (p=0.0431) in the old cohort. Moreover, we observed a significant change in HOXA5 protein expression (p=3x10^-5) negatively correlating with age and promoter methylation thus qualifying HOXA5 for an eligible p53-related aging marker.

HOX Genes Family and Cancer: A Novel Role for Homeobox B9 in the Resistance to Anti-Angiogenic Therapies

Simple Summary

The inhibition of angiogenesis, relying on the use of drugs targeting the VEGF signaling pathway, has become one of the main strategies for cancer treatment. However, the intrinsic and acquired resistance to this type of therapy limit its efficacy. Thus, the identification of novel therapeutic targets is urgently needed. The resistance to anti-angiogenic treatment often occurs through the activation of alternative VEGF independent signaling pathways and recruitment of bone marrow-derived pro-angiogenic cells in the tumor microenvironment. HOX genes are key regulators of embryonic development, also involved in angiogenesis and in cancer progression. HOXB9 upregulation occurs in many types of cancer and it has been identified as a critical transcription factor involved in tumour resistance to anti-angiogenic drugs. Indeed, HOXB9 modulates the expression of alternative pro-angiogenic secreted factors in the tumour microenvironment leading tumor escape from the anti-angiogenic treatments. Hence, HOXB9 could serves as a novel therapeutic target to overcome the resistance to anti-angiogenic therapies.

Abstract

Angiogenesis is one of the hallmarks of cancer, and the inhibition of pro-angiogenic factors and or their receptors has become a primary strategy for cancer therapy. However, despite promising results in preclinical studies, the majority of patients either do not respond to these treatments or, after an initial period of response, they develop resistance to anti-angiogenic agents. Thus, the identification of a novel therapeutic target is urgently needed. Multiple mechanisms of resistance to anti-angiogenic therapy have been identified, including the upregulation of alternative angiogenic pathways and the recruitment of pro-angiogenic myeloid cells in the tumor microenvironment. Homeobox containing (HOX) genes are master regulators of embryonic development playing a pivotal role during both embryonic vasculogenesis and pathological angiogenesis in adults. The importance of HOX genes during cancer progression has been reported in many studies. In this review we will give a brief description of the HOX genes and their involvement in angiogenesis and cancer, with particular emphasis on HOXB9 as a possible novel target for anti-angiogenic therapy. HOXB9 upregulation has been reported in many types of cancers and it has been identified as a critical transcription factor involved in resistance to anti-angiogenic drugs.

Context-dependent HOX transcription factor function in health and disease

During animal development, HOX transcription factors determine the fate of developing tissues to generate diverse organs and appendages. The power of these proteins is striking: mis-expressing a HOX protein causes homeotic transformation of one body part into another. During development, HOX proteins interpret their cellular context through protein interactions, alternative splicing, and post-translational modifications to regulate cell proliferation, cell death, cell migration, cell differentiation, and angiogenesis. Although mutation and/or mis-expression of HOX proteins during development can be lethal, changes in HOX proteins that do not pattern vital organs can result in survivable malformations. In adults, mutation and/or mis-expression of HOX proteins disrupts their gene regulatory networks, deregulating cell behaviors and leading to arthritis and cancer. On the molecular level, HOX proteins are composed of DNA binding homeodomain, and large regions of unstructured, or intrinsically disordered, protein sequence. The primary roles of HOX proteins in arthritis and cancer suggest that mutations associated with these diseases in both the structured and disordered regions of HOX proteins can have substantial functional effects. These insights lead to new questions critical for understanding and manipulating HOX function in physiological and pathological conditions.

miR-129-5p and miR-130a-3p Regulate VEGFR-2 Expression in Sensory and Motor Neurons during Development

The wide-ranging influence of vascular endothelial growth factor (VEGF) within the central (CNS) and peripheral nervous system (PNS), for example through effects on axonal growth or neuronal cell survival, is mainly mediated by VEGF receptor 2 (VEGFR-2). However, the regulation of VEGFR-2 expression during development is not yet well understood. As microRNAs are considered to be key players during neuronal maturation and regenerative processes, we identified the two microRNAs (miRNAs)-miR-129-5p and miR-130a-3p-that may have an impact on VEGFR-2 expression in young and mature sensory and lower motor neurons. The expression level of VEGFR-2 was analyzed by using in situ hybridization, RT-qPCR, Western blot, and immunohistochemistry in developing rats. microRNAs were validated within the spinal cord and dorsal root ganglia. To unveil the molecular impact of our candidate microRNAs, dissociated cell cultures of sensory and lower motor neurons were transfected with mimics and inhibitors. We depicted age-dependent VEGFR-2 expression in sensory and lower motor neurons. In detail, in lower motor neurons, VEGFR-2 expression was significantly reduced during maturation, in conjunction with an increased level of miR-129-5p. In sensory dorsal root ganglia, VEGFR-2 expression increased during maturation and was accompanied by an overexpression of miR-130a-3p. In a second step, the functional significance of these microRNAs with respect to VEGFR-2 expression was proven. Whereas miR-129-5p seems to decrease VEGFR-2 expression in a direct manner in the CNS, miR-130a-3p might indirectly control VEGFR-2 expression in the PNS. A detailed understanding of genetic VEGFR-2 expression control might promote new strategies for the treatment of severe neurological diseases like ischemia or peripheral nerve injury.

Reduced expression of microRNA-130a promotes endothelial cell senescence and age-dependent impairment of neovascularization

Aging is associated with impaired neovascularization in response to ischemia. MicroRNAs are small noncoding RNAs emerging as key regulators of physiological and pathological processes. Here we investigated the potential role of microRNAs in endothelial cell senescence and age-dependent impairment of neovascularization. Next generation sequencing and qRT-PCR analyses identified miR-130a as a pro-angiogenic microRNA which expression is significantly reduced in old mouse aortic endothelial cells (ECs). Transfection of young ECs with a miR-130a inhibitor leads to accelerated senescence and reduced angiogenic functions. Conversely, forced expression of miR-130a in old ECs reduces senescence and improves angiogenesis. In a mouse model of hindlimb ischemia, intramuscular injection of miR-130a mimic in older mice restores blood flow recovery and vascular densities in ischemic muscles, improves mobility and reduces tissue damage. miR-130a directly targets antiangiogenic homeobox genes MEOX2 and HOXA5. MEOX2 and HOXA5 are significantly increased in the ischemic muscles of aging mice, but forced expression of miR-130a reduces the expression of these factors. miR-130a treatment after ischemia is also associated with increased number and improved functional activities of pro-angiogenic cells (PACs). Forced expression of miR-130a could constitute a novel strategy to improve blood flow recovery and reduce ischemia in older patients with ischemic vascular diseases.

Assessment of Expression of Homeobox A5 in Endometrial Cancer on the mRNA and Protein Level

BACKGROUND

Endometrial cancer is one of the most common gynecological cancer in the developed countries and occurs mainly in postmenopausal women. Angiogenesis is important for cancer formation as it provides nutrients for growing tumor mass. Most tumors do not show detectable Homeobox A5 (HOXA5 level), suggesting its potential role as a cancer suppressor. It was demonstrated that HOXA5 is involved in the progression of various types of cancer and the loss of its expression correlates with higher pathological grade and poorer outcome.

OBJECTIVE

The aim of the study was to evaluate HOXA5 expression at transcriptome and protein levels.

MATERIALS AND METHODS

The study enrolled 45 women diagnosed with endometrial cancer and 15 without neoplastic changes. The histopathological examination allowed us to divide cancer tissue samples according to the degree of histological differentiation: G1, 17; G2, 15; G3, 13. The expression of the HOXA5 protein was determined by immunohistochemistry. Microarray and RT-qPCR techniques were used to assess HOXA5 expression at the mRNA level.

RESULTS

The reaction to the HOXA5 protein was only visible in glandular cells in G1 endometrial cancer and was lower compared to the control. In grades 2 and 3, reactions were noted at the limit of the method's sensitivity. In addition, reduced HOXA5 expression was observed at the transcriptome level.

CONCLUSION

HOXA5 may become a potential complementary molecular marker, allowing early detection of neoplastic changes in the endometrium. It also seems that detection of HOXA5 at the mRNA and protein levels may be helpful in improving the accuracy of diagnosis and planning effective oncological therapy.

Methylglyoxal, a Highly Reactive Dicarbonyl Compound, in Diabetes, Its Vascular Complications, and Other Age-Related Diseases

The formation and accumulation of methylglyoxal (MGO), a highly reactive dicarbonyl compound, has been implicated in the pathogenesis of type 2 diabetes, vascular complications of diabetes, and several other age-related chronic inflammatory diseases such as cardiovascular disease, cancer, and disorders of the central nervous system. MGO is mainly formed as a byproduct of glycolysis and, under physiological circumstances, detoxified by the glyoxalase system. MGO is the major precursor of nonenzymatic glycation of proteins and DNA, subsequently leading to the formation of advanced glycation end products (AGEs). MGO and MGO-derived AGEs can impact on organs and tissues affecting their functions and structure. In this review we summarize the formation of MGO, the detoxification of MGO by the glyoxalase system, and the biochemical pathways through which MGO is linked to the development of diabetes, vascular complications of diabetes, and other age-related diseases. Although interventions to treat MGO-associated complications are not yet available in the clinical setting, several strategies to lower MGO have been developed over the years. We will summarize several new directions to target MGO stress including glyoxalase inducers and MGO scavengers. Targeting MGO burden may provide new therapeutic applications to mitigate diseases in which MGO plays a crucial role.

HOX genes as transcriptional and epigenetic regulators during tumorigenesis and their value as therapeutic targets

Several HOX genes are aberrantly expressed in a wide range of cancers interfering with their development and resistance to treatment. This seems to be often caused by alterations in the methylation profiles of their promoters. The role of HOX gene products in cancer is highly 'tissue specific', relying ultimately on their ability to regulate oncogenes or tumor-suppressor genes, directly as transcriptional regulators or indirectly interfering with the levels of epigenetic regulators. Nowadays, different strategies have been tested the use of HOX genes as therapeutic targets for cancer diagnosis and treatment. Here, we trace the history of the research concerning the involvement of HOX genes in cancer, their connection with epigenetic regulation and their potential use as therapeutic targets.

Therapeutic targets for endothelial dysfunction in vascular diseases

Vascular endothelial cells are located on the surface of the blood vessels. It has been recognized as an important barrier to the regulation of vascular homeostasis by regulating the blood flow of micro- or macrovascular vessels. Indeed, endothelial dysfunction is an initial stage of vascular diseases and is an important prognostic indicator of cardiovascular and metabolic diseases such as atherosclerosis, hypertension, heart failure, or diabetes. Therefore, in order to develop therapeutic targets for vascular diseases, it is important to understand the key factors involved in maintaining endothelial function and the signaling pathways affecting endothelial dysfunction. The purpose of this review is to describe the function and underlying signaling pathway of oxidative stress, inflammatory factors, shear stress, and epigenetic factors in endothelial dysfunction, and introduce recent therapeutic targets for the treatment of cardiovascular diseases.

Acetylated HOXB9 at lysine 27 is of differential diagnostic value in patients with pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the ninth most common human malignancy and the sixth leading cause of cancer-related death in China. AcK27-HOXB9 is a newly identified HOXB9 post-transcriptional modification that can predict the outcome in lung adenocarcinoma and colon cancer well. However, the role of AcK27-HOXB9 in PDAC is unclear. The present study aims to investigate the differential diagnostic role of patients with AcK27-HOXB9 PDAC. Tissue microarrays consisting of 162 pancreatic tumor tissue samples from patients with PDAC and paired normal subjects were used to examine HOXB9 and AcK27-HOXB9 levels and localizations by immunohistochemical analysis and Western blot assay, respectively. HOXB9 was upregulated (P < 0.0001), and AcK27-HOXB9 (P =0.0023) was downregulated in patients with PDAC. HOXB9 promoted (P = 0.0115), while AcK27-HOXB9 (P = 0.0279) inhibited PDAC progression. AcK27-HOXB9 predicted favorable outcome in patients with PDAC (P = 0.0412). AcK27-HOXB9 also suppressed PDAC cell migration in a cell migration assay. The results of this study showed that HOXB9 promoted and AcK27-HOXB9 suppressed PDAC progression. The determination of ratio between HOXB9 and AcK27-HOXB9 exhibited potential diagnostic value in patients with PDAC.

The Role of HOX Transcription Factors in Cancer Predisposition and Progression

Homeobox (HOX) transcription factors, encoded by a subset of homeodomain superfamily genes, play pivotal roles in many aspects of cellular physiology, embryonic development, and tissue homeostasis. Findings over the past decade have revealed that mutations in HOX genes can lead to increased cancer predisposition, and HOX genes might mediate the effect of many other cancer susceptibility factors by recognizing or executing altered genetic information. Remarkably, several lines of evidence highlight the interplays between HOX transcription factors and cancer risk loci discovered by genome-wide association studies, thereby gaining molecular and biological insight into cancer etiology. In addition, deregulated HOX gene expression impacts various aspects of cancer progression, including tumor angiogenesis, cell autophagy, proliferation, apoptosis, tumor cell migration, and metabolism. In this review, we will discuss the fundamental roles of HOX genes in cancer susceptibility and progression, highlighting multiple molecular mechanisms of HOX involved gene misregulation, as well as their potential implications in clinical practice.

A Case of Identity: HOX Genes in Normal and Cancer Stem Cells

Stem cells are undifferentiated cells that have the unique ability to self-renew and differentiate into many different cell types. Their function is controlled by core gene networks whose misregulation can result in aberrant stem cell function and defects of regeneration or neoplasia. HOX genes are master regulators of cell identity and cell fate during embryonic development. They play a crucial role in embryonic stem cell differentiation into specific lineages and their expression is maintained in adult stem cells along differentiation hierarchies. Aberrant HOX gene expression is found in several cancers where they can function as either oncogenes by sustaining cell proliferation or tumor-suppressor genes by controlling cell differentiation. Emerging evidence shows that abnormal expression of HOX genes is involved in the transformation of adult stem cells into cancer stem cells. Cancer stem cells have been identified in most malignancies and proved to be responsible for cancer initiation, recurrence, and metastasis. In this review, we consider the role of HOX genes in normal and cancer stem cells and discuss how the modulation of HOX gene function could lead to the development of novel therapeutic strategies that target cancer stem cells to halt tumor initiation, progression, and resistance to treatment.

The Enigmatic HOX Genes: Can We Crack Their Code?

Homeobox genes (HOX) are a large family of transcription factors that direct the formation of many body structures during early embryonic development. There are 39 genes in the subgroup of homeobox genes that constitute the human HOX gene family. Correct embryonic development of flies and vertebrates is, in part, mediated by the unique and highly regulated expression pattern of the HOX genes. Disruptions in these fine-tuned regulatory mechanisms can lead to developmental problems and to human diseases such as cancer. Unfortunately, the molecular mechanisms of action of the HOX family of transcription factors are severely under-studied, likely due to idiosyncratic details of their structure, expression, and function. We suggest that a concerted and collaborative effort to identify interacting protein partners, produce genome-wide binding profiles, and develop HOX network inhibitors in a variety of human cell types will lead to a deeper understanding of human development and disease. Within, we review the technological challenges and possible approaches needed to achieve this goal.

MicroRNA-130a regulates cerebral ischemia-induced blood-brain barrier permeability by targeting Homeobox A5

Blood-brain barrier (BBB) disruption plays a critical role in brain injury induced by cerebral ischemia, and preserving BBB integrity during ischemia could alleviate cerebral injury. We examined the role of miR-130a in ischemic BBB disruption by using models of rat middle cerebral artery occlusion and cell oxygen-glucose deprivation. We found that ischemia significantly increased microRNA-130a (miR-130a) level and that miR-130a was predominantly from brain microvascular endothelial cells. Antagomir-130a, an antagonist of miR-130a, could attenuate brain edema, lower BBB permeability, reduce infarct volume, and improve neurologic function. MiR-130a overexpression induced by miR-130a mimic increased monolayer permeability, and intercellular inhibition of miR-130a by a miR-130a inhibitor suppressed oxygen-glucose deprivation-induced increase in monolayer permeability. Moreover, dual luciferase reporter system showed that Homeobox A5 was the direct target of miR-130a. MiR-130a, by inhibiting Homeobox A5 expression, could down-regulate occludin, thereby increasing BBB permeability. Our results suggested that miR-130a might be implicated in ischemia-induced BBB dysfunction and serve as a target for the treatment of ischemic stroke.-Wang, Y., Wang, M.-D., Xia, Y.-P., Gao, Y., Zhu, Y.-Y., Chen, S.-C., Mao, L., He, Q.-W., Yue, Z.-Y., Hu, B. MicroRNA-130a regulates cerebral ischemia-induced blood-brain barrier permeability by targeting Homeobox A5.

miR-339-5p inhibits metastasis of non-small cell lung cancer by regulating the epithelial-to-mesenchymal transition

Metastasis is a common event in cancer pathology, and represents the primary cause of cancer-associated mortality. Metastasis, which is the process in which cancer cells at the primary tumor site spread to a different location in the body and form a new tumor, is regulated by multiple factors and includes a number of steps and stages. In our previous study, it was demonstrated miR-339-5p inhibits cell migration and invasion in vitro and is associated with the tumor-node-metastasis stage and the lymph node metastasis status of non-small cell lung cancer. In the present study, expression of miR-339-5p was first determined in the tissues and peripheral blood of patients with non-small cell lung cancer (NSCLC) and in NSCLC cell lines. It was then demonstrated that miR-339-5p inhibits A549 and H1299 cell invasion. The underlying molecular events of miR-339-5p action in NSCLC were also explored. By luciferase assay and western blot analysis, B-cell CLL/lymphoma 6 (BCL6) was verified as the direct target gene of miR-339-5p. miR-339-5p may inhibit lung cancer cell invasion and migration by regulating the epithelial-to-mesenchymal transition via BCL6 in vitro. It was also demonstrated that the relative expression of miR-339-5p in the peripheral blood is associated with cancer metastasis in patients with non-small cell lung cancer.

Differentially expressed genes and canonical pathways in the ascending thoracic aortic aneurysm - The Tampere Vascular Study

Ascending thoracic aortic aneurysm (ATAA) is a multifactorial disease with a strong inflammatory component. Surgery is often required to prevent aortic rupture and dissection. We performed gene expression analysis (Illumina HumanHT-12 version 3 Expression BeadChip) for 32 samples from ATAA (26 without/6 with dissection), and 28 left internal thoracic arteries (controls) collected in Tampere Vascular study. We compared expression profiles and conducted pathway analysis using Ingenuity Pathway Analysis (IPA) to reveal differences between ATAA and a healthy artery wall. Almost 5000 genes were differentially expressed in ATAA samples compared to controls. The most downregulated gene was homeobox (HOX) A5 (fold change, FC = -25.3) and upregulated cadherin-2 (FC = 12.6). Several other HOX genes were also found downregulated (FCs between -25.3 and -1.5, FDR < 0.05). 43, mostly inflammatory, canonical pathways in ATAA were found to be significantly (p < 0.05, FDR < 0.05) differentially expressed. The results remained essentially the same when the 6 dissected ATAA samples were excluded from the analysis. We show for the first time on genome level that ATAA is an inflammatory process, revealing a more detailed molecular pathway level pathogenesis. We propose HOX genes as potentially important players in maintaining aortic integrity, altered expression of which might be important in the pathobiology of ATAA.

Analysis of Transcriptional Variability in a Large Human iPSC Library Reveals Genetic and Non-genetic Determinants of Heterogeneity

Variability in induced pluripotent stem cell (iPSC) lines remains a concern for disease modeling and regenerative medicine. We have used RNA-sequencing analysis and linear mixed models to examine the sources of gene expression variability in 317 human iPSC lines from 101 individuals. We found that ∼50% of genome-wide expression variability is explained by variation across individuals and identified a set of expression quantitative trait loci that contribute to this variation. These analyses coupled with allele-specific expression show that iPSCs retain a donor-specific gene expression pattern. Network, pathway, and key driver analyses showed that Polycomb targets contribute significantly to the non-genetic variability seen within and across individuals, highlighting this chromatin regulator as a likely source of reprogramming-based variability. Our findings therefore shed light on variation between iPSC lines and illustrate the potential for our dataset and other similar large-scale analyses to identify underlying drivers relevant to iPSC applications.

Genome-wide association analysis for chronic venous disease identifies EFEMP1 and KCNH8 as susceptibility loci

Chronic venous disease (CVD) is a multifactorial condition representing one of the most common disorders among populations of Western countries. The heritability of about 17% suggests genetic risk factors in CVD etiology. However, so far the genetic causes are unknown. We undertook the hitherto first genome-wide association study (GWAS) for CVD, analyzing more than 1.93 M SNPs in 4,942 German individuals, followed by replication in two independent German data sets. The combined analysis of discovery and replication stages (2,269 cases and 7,765 controls) yielded robust associations within the two genes EFEMP1 and KCNH8 (rs17278665, rs727139 with P < 5 × 10⁻⁸), and suggestive association within gene SKAP2 (rs2030136 with P < 5 × 10⁻⁷). Association signals of rs17278665 and rs727139 reside in regions of low linkage disequilibrium containing no other genes. Data from the ENCODE and Roadmap Epigenomics projects show that tissue specific marks overlap with the variants. SNPs rs17278665 and rs2030136 are known eQTLs. Our study demonstrates that GWAS are a valuable tool to study the genetic component of CVD. With our approach, we identified two novel genome-wide significant susceptibility loci for this common disease. Particularly, the extracellular matrix glycoprotein EFEMP1 is promising for future functional studies due to its antagonistic role in vessel development and angiogenesis.

Large-scale gene network analysis reveals the significance of extracellular matrix pathway and homeobox genes in acute myeloid leukemia: an introduction to the Pigengene package and its applications

BACKGROUND

The distinct types of hematological malignancies have different biological mechanisms and prognoses. For instance, myelodysplastic syndrome (MDS) is generally indolent and low risk; however, it may transform into acute myeloid leukemia (AML), which is much more aggressive.

METHODS

We develop a novel network analysis approach that uses expression of eigengenes to delineate the biological differences between these two diseases.

RESULTS

We find that specific genes in the extracellular matrix pathway are underexpressed in AML. We validate this finding in three ways: (a) We train our model on a microarray dataset of 364 cases and test it on an RNA Seq dataset of 74 cases. Our model showed 95% sensitivity and 86% specificity in the training dataset and showed 98% sensitivity and 91% specificity in the test dataset. This confirms that the identified biological signatures are independent from the expression profiling technology and independent from the training dataset. (b) Immunocytochemistry confirms that MMP9, an exemplar protein in the extracellular matrix, is underexpressed in AML. (c) MMP9 is hypermethylated in the majority of AML cases (n=194, Welch's t-test p-value <10^-138), which complies with its low expression in AML. Our novel network analysis approach is generalizable and useful in studying other complex diseases (e.g., breast cancer prognosis). We implement our methodology in the Pigengene software package, which is publicly available through Bioconductor.

CONCLUSIONS

Eigengenes define informative biological signatures that are robust with respect to expression profiling technology. These signatures provide valuable information about the underlying biology of diseases, and they are useful in predicting diagnosis and prognosis.

Circulating Exosomes in Cardiovascular Diseases

Circulating exosomes could arrive in distant tissues via blood circulation, thus directly communicating with target cells and rapidly regulating intracellular signalings. Circulating exosomes and exosomal cargos are critically involved in cardiovascular pathophysiology, such as cardiomyocyte hypertrophy, apoptosis, and angiogenesis. Circulating exosomes enriched with various types of biological molecules can be changed not only in the number but also in the composite cargos upon cardiac injury, such as myocardial infarction, myocardial ischemia reperfusion injury, atherosclerosis, hypertension, and sepsis cardiomyopathy, which may further influence cardiomyocyte function and contribute to the pathogenesis of cardiovascular diseases. Thus, exosome-based therapeutic strategy may be used to attenuate myocardial injury and promote cardiac regeneration and repair. Also, more preclinical and clinical studies would be needed to investigate the potential of circulating exosomes as biomarkers for the diagnosis, risk stratification, and prognosis of cardiovascular diseases.

HOXA5 localization in postnatal and adult mouse brain is suggestive of regulatory roles in postmitotic neurons

Hoxa5 is a member of the Hox gene family, which plays critical roles in successive steps of the central nervous system formation during embryonic and fetal development. Hoxa5 expression in the adult mouse brain has been reported, suggesting that this gene may be functionally required in the brain after birth. To provide further insight into the Hoxa5 expression pattern and potential functions in the brain, we have characterized its neuroanatomical profile from embryonic stages to adulthood. While most Hox mapping studies have been based solely on transcript analysis, we extended our analysis to HOXA5 protein localization in adulthood using specific antibodies. Our results show that Hoxa5 expression appears in the most caudal part of the hindbrain at fetal stages, where it is maintained until adulthood. In the medulla oblongata and pons, we detected Hoxa5 expression in many precerebellar neurons and in several nuclei implicated in the control of autonomic functions. In these territories, the HOXA5 protein is present solely in neurons, specifically in γ-aminobutyric acid (GABA)ergic, glutamatergic, and catecholaminergic neurons. Finally, we also detected Hoxa5 transcripts, but not the HOXA5 protein, in the thalamus and the cortex, from postnatal stages to adult stages, and in the cerebellum at adulthood. We provide evidence that some larger variants of Hoxa5 transcripts are present in these territories. Our mapping analysis allowed us to build hypotheses regarding HOXA5 functions in the nervous system after birth, such as a potential role in the establishment and refinement/plasticity of precerebellar circuits during postnatal and adult life. J. Comp. Neurol. 525:1155-1175, 2017. © 2016 Wiley Periodicals, Inc.

Current Evidence and Future Perspectives on HuR and Breast Cancer Development, Prognosis, and Treatment

Hu-antigen R (HuR) is an RNA-binding posttranscriptional regulator that belongs to the Hu/ELAV family. HuR expression levels are modulated by a variety of proteins, microRNAs, chemical compounds, or the microenvironment, and in turn, HuR affects mRNA stability and translation of various genes implicated in breast cancer formation, progression, metastasis, and treatment. The aim of the present review is to critically summarize the role of HuR in breast cancer development and its potential as a prognosticator and a therapeutic target. In this aspect, all the existing English literature concerning HuR expression and function in breast cancer cell lines, in vivo animal models, and clinical studies is critically presented and summarized. HuR modulates many genes implicated in biological processes crucial for breast cancer formation, growth, and metastasis, whereas the link between HuR and these processes has been demonstrated directly in vitro and in vivo. Additionally, clinical studies reveal that HuR is associated with more aggressive forms of breast cancer and is a putative prognosticator for patients' survival. All the above indicate HuR as a promising drug target for cancer therapy; nevertheless, additional studies are required to fully understand its potential and determine against which types of breast cancer and at which stage of the disease a therapeutic agent targeting HuR would be more effective.

PCAF-mediated acetylation of transcriptional factor HOXB9 suppresses lung adenocarcinoma progression by targeting oncogenic protein JMJD6

HOXB9 is a homeobox domain-containing transcription factor, playing an important role in embryonic development and cancer progression. However, the precise post-translational modifications (PTMs) of HOXB9 and the corresponding roles are unclear. Here, we report that acetyltransferase p300/CBP-associated factor (PCAF) interacts with and acetylates HOXB9 both in vivo and in vitro Conversely, the acetylation of HOXB9 can be reversed by deacetylase SIRT1. Furthermore, we found that HOXB9 is acetylated at lysine 27 (AcK27). Functionally, in contrast to the wild type HOXB9, AcK27-HOXB9 decreased its capacity in promoting lung cancer cell migration and tumor growth in mice. Mechanistically, AcK27-HOXB9 suppresses the transcription of its target gene Jumonji domain-containing protein 6 (JMJD6) by direct occupying the promoter of JMJD6 gene. For clinical relevance, elevated HOXB9 acetylation at K27 predicts a better prognosis in lung adenocarcinoma patients. Taken together, we identified the first PTM of HOXB9 by demonstrating that HOXB9 can be acetylated and AcK27-HOXB9 counteracts the role of the wild-type HOXB9 in regulating lung adenocarcinoma progression.

Underexpression of HOXA11 Is Associated with Treatment Resistance and Poor Prognosis in Glioblastoma

Purpose

Homeobox (HOX) genes are essential developmental regulators that should normally be in the silenced state in an adult brain. The aberrant expression of HOX genes has been associated with the prognosis of many cancer types, including glioblastoma (GBM). This study examined the identity and role of HOX genes affecting GBM prognosis and treatment resistance.

Materials and Methods

The full series of HOX genes of five pairs of initial and recurrent human GBM samples were screened by microarray analysis to determine the most plausible candidate responsible for GBM prognosis. Another 20 newly diagnosed GBM samples were used for prognostic validation. In vitro experiments were performed to confirm the role of HOX in treatment resistance. Mediators involved in HOX gene regulation were searched using differentially expressed gene analysis, gene set enrichment tests, and network analysis.

Results

The underexpression of HOXA11 was identified as a consistent signature for a poor prognosis among the HOX genes. The overall survival of the GBM patients indicated a significantly favorable prognosis in patients with high HOXA11 expression (31±15.3 months) compared to the prognoses in thosewith low HOXA11 expression (18±7.3 months, p=0.03). When HOXA11 was suppressed in the GBM cell lines, the anticancer effect of radiotherapy and/or temozolomide declined. In addition, five candidate mediators (TGFBR2, CRIM1, TXNIP, DPYSL2, and CRMP1) that may confer an oncologic effect after HOXA11 suppression were identified.

Conclusion

The treatment resistance induced by the underexpression of HOXA11 can contribute to a poor prognosis in GBM. Further investigation will be needed to confirm the value of HOXA11 as a potential target for overcoming the treatment resistance by developing chemo- or radiosensitizers.

Improving stem cell therapy in cardiovascular diseases: the potential role of microRNA

The initial promising prospect of autologous bone marrow-derived stem cell therapy in the setting of cardiovascular diseases has been overshadowed by functional shortcomings of the stem cell product. As powerful epigenetic regulators of (stem) cell function, microRNAs are valuable targets for novel therapeutic strategies. Indeed, modulation of specific miRNA expression could contribute to improved therapeutic efficacy of stem cell therapy. First, this review elaborates on the functional relevance of miRNA dysregulation in bone marrow-derived progenitor cells in different cardiovascular diseases. Next, we provide a comprehensive overview of the current evidence on the effect of specific miRNA modulation in several types of progenitor cells on cardiac and/or vascular regeneration. By elaborating on the cardioprotective regulation of progenitor cells on cardiac miRNAs, more insight in the underlying mechanisms of stem cell therapy is provided. Finally, some considerations are made regarding the potential of circulating miRNAs as regulators of the miRNA signature of progenitor cells in cardiovascular diseases.

Urokinase-type Plasminogen Activator (uPA) Promotes Angiogenesis by Attenuating Proline-rich Homeodomain Protein (PRH) Transcription Factor Activity and De-repressing Vascular Endothelial Growth Factor (VEGF) Receptor Expression

Urokinase-type plasminogen activator (uPA) regulates angiogenesis and vascular permeability through proteolytic degradation of extracellular matrix and intracellular signaling initiated upon its binding to uPAR/CD87 and other cell surface receptors. Here, we describe an additional mechanism by which uPA regulates angiogenesis. Ex vivo VEGF-induced vascular sprouting from Matrigel-embedded aortic rings isolated from uPA knock-out (uPA(-/-)) mice was impaired compared with vessels emanating from wild-type mice. Endothelial cells isolated from uPA(-/-) mice show less proliferation and migration in response to VEGF than their wild type counterparts or uPA(-/-) endothelial cells in which expression of wild type uPA had been restored. We reported previously that uPA is transported from cell surface receptors to nuclei through a mechanism that requires its kringle domain. Intranuclear uPA modulates gene transcription by binding to a subset of transcription factors. Here we report that wild type single-chain uPA, but not uPA variants incapable of nuclear transport, increases the expression of cell surface VEGF receptor 1 (VEGFR1) and VEGF receptor 2 (VEGFR2) by translocating to the nuclei of ECs. Intranuclear single-chain uPA binds directly to and interferes with the function of the transcription factor hematopoietically expressed homeodomain protein or proline-rich homeodomain protein (HHEX/PRH), which thereby lose their physiologic capacity to repress the activity of vehgr1 and vegfr2 gene promoters. These studies identify uPA-dependent de-repression of vegfr1 and vegfr2 gene transcription through binding to HHEX/PRH as a novel mechanism by which uPA mediates the pro-angiogenic effects of VEGF and identifies a potential new target for control of pathologic angiogenesis.

Hoxa5: A Key Player in Development and Disease

A critical position in the developmental hierarchy is occupied by the Hox genes, which encode transcription factors. Hox genes are crucial in specifying regional identity along the embryonic axes and in regulating morphogenesis. In mouse, targeted mutations of Hox genes cause skeletal transformations and organ defects that can impair viability. Here, we present the current knowledge about the Hoxa5 gene, a paradigm for the function and the regulation of Hox genes. The phenotypic survey of Hoxa5-/- mice has unveiled its critical role in the regional specification of the skeleton and in organogenesis. Most Hoxa5-/- mice die at birth from respiratory distress due to tracheal and lung dysmorphogenesis and impaired diaphragm innervation. The severity of the phenotype establishes that Hoxa5 plays a predominant role in lung organogenesis versus other Hox genes. Hoxa5 also governs digestive tract morphogenesis, thyroid and mammary glands development, and ovary homeostasis. Deregulated Hoxa5 expression is reported in cancers, indicating Hoxa5 involvement in tumor predisposition and progression. The dynamic Hoxa5 expression profile is under the transcriptional control of multiple cis-acting sequences and trans-acting regulators. It is also modulated by epigenetic mechanisms, implicating chromatin modifications and microRNAs. Finally, lncRNAs originating from alternative splicing and distal promoters encompass the Hoxa5 locus.

Cellular and molecular insights into Hox protein action

Hox genes encode homeodomain transcription factors that control morphogenesis and have established functions in development and evolution. Hox proteins have remained enigmatic with regard to the molecular mechanisms that endow them with specific and diverse functions, and to the cellular functions that they control. Here, we review recent examples of Hox-controlled cellular functions that highlight their versatile and highly context-dependent activity. This provides the setting to discuss how Hox proteins control morphogenesis and organogenesis. We then summarise the molecular modalities underlying Hox protein function, in particular in light of current models of transcription factor function. Finally, we discuss how functional divergence between Hox proteins might be achieved to give rise to the many facets of their action.

Attenuation of cardiac dysfunction and remodeling of myocardial infarction by microRNA-130a are mediated by suppression of PTEN and activation of PI3K dependent signaling

OBJECTIVE

Activation of PI3K/Akt signaling protects the myocardium from ischemia/reperfusion injury. MicroRNAs have been demonstrated to play an important role in the regulation of gene expression at the post-transcriptional level. In this study, we examined whether miR-130a will attenuate cardiac dysfunction and remodeling after myocardial infarction (MI) via PI3K/Akt dependent mechanism.

APPROACHES AND RESULTS

To determine the role of miR-130a in the proliferation and migration of endothelial cells, HUVECs were transfected with miR-130a mimics before the cells were subjected to scratch-induced wound injury. Transfection of miR-130a mimics stimulated the migration of endothelial cells into the wound area and increased phospho-Akt levels. To examine the effect of miR-130a on cardiac dysfunction and remodeling after MI, Lentivirus expressing miR-130a (LmiR-130a) was delivered into mouse hearts seven days before the mice were subjected to MI. Cardiac function was assessed by echocardiography before and for up to 21 days after MI. Ejection fraction (EF%) and fractional shortening (FS%) in the LmiR-130a transfected MI hearts were significantly greater than in LmiR-control and untransfected control MI groups. LmiR-130a transfection increased capillary number and VEGF expression, and decreased collagen deposition in the infarcted myocardium. Importantly, LmiR-130a transfection significantly suppressed PTEN expression and increased the levels of phosphorylated Akt in the myocardium. However, treatment of LmiR-130a-transfected mice with LY294002, a PI3K inhibitor, completely abolished miR-130a-induced attenuation of cardiac dysfunction after MI.

CONCLUSIONS

miR-130a plays a critical role in attenuation of cardiac dysfunction and remodeling after MI. The mechanisms involve activation of PI3K/Akt signaling via suppression of PTEN expression.

MicroRNAs; easy and potent targets in optimizing therapeutic methods in reparative angiogenesis

The age‐related senescence of adult tissues is associated with the decreased level of angiogenic capability and with the development of a degenerative disease such as atherosclerosis which thereafter result in the deteriorating function of multiple systems. Findings indicate that tissue senescence not only diminishes repair processes but also promotes atherogenesis, serving as a double‐edged sword in the development and prognosis of ischaemia‐associated diseases. Evidence evokes microRNAs (miRNAs) as molecular switchers that underlie cellular events in different tissues. Here, miRNAs would promote new potential targets for optimizing therapeutic methods in blood flow recovery to the ischaemic area. Effectively beginning an ischaemia therapy, a more characteristic of miRNA changes in adult tissues is prerequisite and in the forefront. It may also be a preliminary phase in treatment strategies by stem cell‐based therapy.

Topographic patterns of vascular disease: HOX proteins as determining factors?

Steadily increasing evidence supports the idea that genetic diversities in the vascular bed are, in addition to hemodynamic influences, a major contributing factor in determining region-specific cardiovascular disease susceptibility. Members of the phylogenetically highly conserved Hox gene family of developmental regulators have to be viewed as prime candidates for determining these regional genetic differences in the vasculature. During embryonic patterning, the regionally distinct and precisely choreographed expression patterns of HOX transcription factors are essential for the correct specification of positional identities. Apparently, these topographic patterns are to some degree retained in certain adult tissues, including the circulatory system. While an understanding of the functional significance of these localized Hox activities in adult blood vessels is only beginning to emerge, an argument can be made for a role of Hox genes in the maintenance of vessel wall homeostasis and functional integrity on the one hand, and in regulating the development and progression of regionally restricted vascular pathologies, on the other. Initial functional studies in animal models, as well as data from clinical studies provide some level of support for this view. The data suggest that putative genetic regulatory networks of Hox-dependent cardiovascular disease processes include genes of diverse functional categories (extracellular matrix remodeling, transmembrane signaling, cell cycle control, inflammatory response, transcriptional control, etc.), as potential targets in both vascular smooth muscle and endothelial cells, as well as cell populations residing in the adventitia.

Epigenetic Regulation of Angiogenesis by JARID1B-Induced Repression of HOXA5

OBJECTIVE

Altering endothelial biology through epigenetic modifiers is an attractive novel concept, which is, however, just in its beginnings. We therefore set out to identify chromatin modifiers important for endothelial gene expression and contributing to angiogenesis.

APPROACH AND RESULTS

To identify chromatin modifying enzymes in endothelial cells, histone demethylases were screened by microarray and polymerase chain reaction. The histone 3 lysine 4 demethylase JARID1B was identified as a highly expressed enzyme at the mRNA and protein levels. Knockdown of JARID1B by shRNA in human umbilical vein endothelial cells attenuated cell migration, angiogenic sprouting, and tube formation. Similarly, pharmacological inhibition and overexpression of a catalytic inactive JARID1B mutant reduced the angiogenic capacity of human umbilical vein endothelial cells. To identify the in vivo relevance of JARID1B in the vascular system, Jarid1b knockout mice were studied. As global knockout results in increased mortality and developmental defects, tamoxifen-inducible and endothelial-specific knockout mice were generated. Acute knockout of Jarid1b attenuated retinal angiogenesis and endothelial sprout outgrowth from aortic segments. To identify the underlying mechanism, a microarray experiment was performed, which led to the identification of the antiangiogenic transcription factor HOXA5 to be suppressed by JARID1B. Importantly, downregulation or inhibition of JARID1B, but not of JARID1A and JARID1C, induced HOXA5 expression in human umbilical vein endothelial cells. Consistently, chromatin immunoprecipitation revealed that JARID1B occupies and reduces the histone 3 lysine 4 methylation levels at the HOXA5 promoter, demonstrating a direct function of JARID1B in endothelial HOXA5 gene regulation.

CONCLUSIONS

JARID1B, by suppressing HOXA5, maintains the endothelial angiogenic capacity in a demethylase-dependent manner.

The role of epigenetics in the endothelial cell shear stress response and atherosclerosis

Currently in the field of vascular biology, the role of epigenetics in endothelial cell biology and vascular disease has attracted more in-depth study. Using both in vitro and in vivo models of blood flow, investigators have recently begun to reveal the underlying epigenetic regulation of endothelial gene expression. Recently, our group, along with two other independent groups, have demonstrated that blood flow controls endothelial gene expression by DNA methyltransferases (DNMT1 and 3A). Disturbed flow (d-flow), characterized by low and oscillating shear stress (OS), is pro-atherogenic and induces expression of DNMT1 both in vivo and in vitro. D-flow regulates genome-wide DNA methylation patterns in a DNMT-dependent manner. The DNMT inhibitor 5-Aza-2'deoxycytidine (5Aza) or DNMT1 siRNA reduces OS-induced endothelial inflammation. Moreover, 5Aza inhibits the development of atherosclerosis in ApoE(-/-) mice. Through a systems biological analysis of genome-wide DNA methylation patterns and gene expression data, we found 11 mechanosensitive genes which were suppressed by d-flow in vivo, experienced hypermethylation in their promoter region in response to d-flow, and were rescued by 5Aza treatment. Interestingly, among these mechanosensitive genes, the two transcription factors HoxA5 and Klf3 contain cAMP-response-elements (CRE), which may indicate that methylation of CRE sites could serve as a mechanosensitive master switch in gene expression. These findings provide new insight into the mechanism by which flow controls epigenetic DNA methylation patterns, which in turn alters endothelial gene expression, regulates vascular biology, and induces atherosclerosis. These novel findings have broad implications for understanding the biochemical mechanisms of atherogenesis and provide a basis for identifying potential therapeutic targets for atherosclerosis. This article is part of a Directed Issue entitled: Epigenetics dynamics in development and disease.