Differential regulation of microRNAs by p53 revealed by massively parallel sequencing: miR-34a is a p53 target that induces apoptosis and G1-arrest

The RNA-binding protein SART3 promotes miR-34a biogenesis and G1 cell cycle arrest in lung cancer cells

MicroRNAs (miRNAs or miRs) are small, noncoding RNAs that are implicated in the regulation of most biological processes. Global miRNA biogenesis is altered in many cancers, and RNA-binding proteins play a role in miRNA biogenesis, presenting a promising avenue for targeting miRNA dysregulation in diseases. miR-34a exhibits tumor-suppressive activities by targeting cell cycle regulators CDK4/6 and anti-apoptotic factor BCL-2, among other regulatory pathways such as Wnt, TGF-β, and Notch signaling. Many cancers exhibit down-regulation or loss of miR-34a, and synthetic miR-34a supplementation has been shown to inhibit tumor growth in vivo However, the post-transcriptional mechanisms that cause miR-34a loss in cancer are not entirely understood. Here, using a proteomics-mediated approach in non-small-cell lung cancer (NSCLC) cells, we identified squamous cell carcinoma antigen recognized by T-cells 3 (SART3) as a putative pre-miR-34a-binding protein. SART3 is a spliceosome recycling factor and nuclear RNA-binding protein with no previously reported role in miRNA regulation. We found that SART3 binds pre-miR-34a with higher specificity than pre-let-7d (used as a negative control) and elucidated a new functional role for SART3 in NSCLC cells. SART3 overexpression increased miR-34a levels, down-regulated the miR-34a target genes CDK4/6, and caused a cell cycle arrest in the G1 phase. In vitro binding experiments revealed that the RNA-recognition motifs within the SART3 sequence are responsible for selective pre-miR-34a binding. Our results provide evidence for a significant role of SART3 in miR-34a biogenesis and cell cycle progression in NSCLC cells.

Genetic and epigenetic modifications induced by chemotherapeutic drugs: human amniotic fluid stem cells as an in-vitro model

BACKGROUND

Bleomycin, etoposide and cisplatin (BEP) are three chemotherapeutic agents widely used individually or in combination with each other or other chemotherapeutic agents in the treatment of various cancers. These chemotherapeutic agents are cytotoxic; hence, along with killing cancerous cells, they also damage stem cell pools in the body, which causes various negative effects on patients. The epigenetic changes due to the individual action of BEP on stem cells are largely unknown.

METHODS

Human amniotic fluid stem cells (hAFSCs) were treated with our in-vitro standardized dosages of BEP individually, for seven days. The cells were harvested after the treatment and extraction of DNA and RNA were performed. Real-time PCR and flow cytometry were conducted for cell markers analysis. The global DNA methylation was quantified using 5mC specific kit and promoter and CpG methylation % through bisulfite conversion and pyrosequencing. Micro- RNAs (miRNAs) were quantified with real-time qPCR.

RESULTS

The cytotoxic nature of BEP was observed even at low dosages throughout the experiment. We also investigated the change in the expression of various pluripotent and germline markers and found a significant change in the properties of the cells after the treatments. The methylation of DNA at global, promoter and individual CpG levels largely get fluctuated due to the BEP treatment. Several tested miRNAs showed differential expression. No positive correlation between mRNA and protein expression was observed for some markers.

CONCLUSION

Cytotoxic chemotherapeutic agents such as BEP were found to alter stem cell properties of hAFSCs. Different methylation profiles change dynamically, which may explain such changes in cellular properties. Data also suggests that the fate of hAFSCs after treatment may depend upon the interplay between the miRNAs. Finally, our results demonstrate that hAFSCs might prove to be a suitable in-vitro model of stem cells to predict genetic and epigenetic modification due to the action of various drugs.

Genome-Wide Small RNA Sequencing Identifies MicroRNAs Deregulated in Non-Small Cell Lung Carcinoma Harboring Gain-of-Function Mutant p53

Mutations in the TP53 gene are one of the most frequent events in cancers. Certain missense mutant p53 proteins gain oncogenic functions (gain-of-functions) and drive tumorigenesis. Apart from the coding genes, a few non-coding microRNAs (miRNAs) are implicated in mediating mutant p53-driven cancer phenotypes. Here, we identified miRNAs in mutant p53^R273H bearing non-small cell lung carcinoma (NSCLC) cells while using small RNA deep sequencing. Differentially regulated miRNAs were validated in the TCGA lung adenocarcinoma patients with p53 mutations and, subsequently, we identified specific miRNA signatures that are associated with lymph node metastasis and poor survival of the patients. Pathway analyses with integrated miRNA-mRNA expressions further revealed potential regulatory molecular networks in mutant p53 cancer cells. A possible contribution of putative mutant p53-regulated miRNAs in epithelial-to-mesenchymal transition (EMT) is also predicted. Most importantly, we identified a novel miRNA from the unmapped sequencing reads through a systematic computational approach. The newly identified miRNA promotes proliferation, colony-forming ability, and migration of NSCLC cells. Overall, the present study provides an altered miRNA expression profile that might be useful in biomarker discovery for non-small cell lung cancers with TP53 mutations and discovers a hitherto unknown miRNA with oncogenic potential.

Small extracellular vesicles convey the stress-induced adaptive responses of melanoma cells

Exosomes are small extracellular vesicles (sEVs), playing a crucial role in the intercellular communication in physiological as well as pathological processes. Here, we aimed to study whether the melanoma-derived sEV-mediated communication could adapt to microenvironmental stresses. We compared B16F1 cell-derived sEVs released under normal and stress conditions, including cytostatic, heat and oxidative stress. The miRNome and proteome showed substantial differences across the sEV groups and bioinformatics analysis of the obtained data by the Ingenuity Pathway Analysis also revealed significant functional differences. The in silico predicted functional alterations of sEVs were validated by in vitro assays. For instance, melanoma-derived sEVs elicited by oxidative stress increased Ki-67 expression of mesenchymal stem cells (MSCs); cytostatic stress-resulted sEVs facilitated melanoma cell migration; all sEV groups supported microtissue generation of MSC-B16F1 co-cultures in a 3D tumour matrix model. Based on this study, we concluded that (i) molecular patterns of tumour-derived sEVs, dictated by the microenvironmental conditions, resulted in specific response patterns in the recipient cells; (ii) in silico analyses could be useful tools to predict different stress responses; (iii) alteration of the sEV-mediated communication of tumour cells might be a therapy-induced host response, with a potential influence on treatment efficacy.

A novel CXCL8 analog is effective in inhibiting the growth via cell cycle arrest and attenuating invasion of Lewis lung carcinoma

Purpose

Lung cancer and other solid tumors contain not only tumor cells but various types of stromal cells, such as fibroblasts and endothelial cells. In addition, tumors are infiltrated by inflammatory cells (neutrophils, macrophages, and lymphocytes). Tumor cells, stromal cells, and the tumor-associated leukocytes are responsible for the production of chemokines inside the tumor and the maintenance of systemic circulating chemokine levels. CXCL8 and its receptors, CXCR1 and CXCR2, were found to play important roles in tumor proliferation, migration, survival, and growth. We have developed a novel ELR-CXC chemokine antagonist CXCL8-IP10 based on the structure of CXCL8 and IP10.

Patients and methods

We assessed the anticancer efficacies of the blockade of CXCL8-CXCR1/2 axis in the Lewis lung carcinoma (LL/2) model using CXCL8-IP10.

Results

We found that CXCL8-IP10 markedly reduced LL/2 cell anchorage-independent growth and invasion. Moreover, we demonstrated that CXCL8-IP10 could significantly suppress tumor growth and improve survival rate as well as lifespan of C57BL/6 mice inoculated with LL/2 cells.

Conclusion

Our results suggest that ELR-CXC chemokine antagonism would potentially be a useful therapeutic approach in patients with lung cancer.

Cross-talk between Myc and p53 in B-cell lymphomas

Myc and p53 proteins are closely associated with many physiological cellular functions, including immune response and lymphocyte survival, and are expressed in the lymphoid organs, which are sites for the development and activation of B-cell malignancies. Genetic alterations and other mechanisms resulting in constitutive activation, rearrangement, or mutation of MYC and TP53 contribute to the development of lymphomas, progression and therapy resistance by gene dysregulation, activation of downstream anti-apoptotic pathways, and unfavorable microenvironment interactions. The cross-talk between the Myc and p53 proteins contributes to the inferior prognosis in many types of B-cell lymphomas. In this review, we present the physiological roles of Myc and p53 proteins, and recent advances in understanding the pathological roles of Myc, p53, and their cross-talk in lymphoid neoplasms. In addition, we highlight clinical trials of novel agents that directly or indirectly inhibit Myc and/or p53 protein functions and their signaling pathways. Although, to date, these trials have failed to overcome drug resistance, the new results have highlighted the clinical efficiency of targeting diverse mechanisms of action with the goal of optimizing novel therapeutic opportunities to eradicate lymphoma cells.

Identification and validation of microRNAs that synergize with miR-34a - a basis for combinatorial microRNA therapeutics

Efforts to search for better treatment options for cancer have been a priority, and due to these efforts, new alternative therapies have emerged. For instance, clinically relevant tumor-suppressive microRNAs that target key oncogenic drivers have been identified as potential anti-cancer therapeutics. MicroRNAs are small non-coding RNAs that negatively regulate gene expression at the posttranscriptional level. Aberrant microRNA expression, through misexpression of microRNA target genes, can have profound cellular effects leading to a variety of diseases, including cancer. While altered microRNA expression contributes to a cancerous state, restoration of microRNA expression has therapeutic benefits. For example, ectopic expression of microRNA-34a (miR-34a), a tumor suppressor gene that is a direct transcriptional target of p53 and thus is reduced in p53 mutant tumors, has clear effects on cell proliferation and survival in murine models of cancer. MicroRNA replacement therapies have recently been tested in combination with other agents, including other microRNAs, to simultaneously target multiple pathways to improve the therapeutic response. Thus, we reasoned that other microRNA combinations could collaborate to further improve treatment. To test this hypothesis miR-34a was used in an unbiased cell-based approach to identify combinatorial microRNA pairs with enhanced efficacy over miR-34a alone. This approach identified a subset of microRNAs that was able to enhance the miR-34a antiproliferative activity. These microRNA combinatorial therapeutics could offer superior tumor-suppressive abilities to suppress oncogenic properties compared to a monotherapeutic approach. Collectively these studies aim to address an unmet need of identifying, characterizing, and therapeutically targeting microRNAs for the treatment of cancer.

Oxibendazole induces apoptotic cell death in proliferating porcine trophectoderm and uterine luminal epithelial cells via mitochondria-mediated calcium disruption and breakdown of mitochondrial membrane potential

The well-known and effective anthelmintic oxibendazole was recently shown to have a broad spectrum of biological abilities, such as anti-cancer and anti-inflammation activities. In contrast, the mechanism of oxibendazole's anti-proliferative effect via cell signaling pathways and its role in pre-implantation has not been studied. Therefore, in this study we demonstrated the effects of oxibendazole on the proliferation of porcine trophectoderm (pTr) cells and porcine luminal epithelial (pLE) cells, a well-known in vitro model system of the fetal-maternal interface. Cell proliferation decreased in both pTr and pLE cells in response to oxibendazole, and we determined that this was modulated through intracellular cell signal transduction. Phosphorylation of ERK1/2, P90RSK, and S6 were downregulated by exposure to a 200 nM dose of oxibendazole in both types of cells, while the expression of phosphorylated JNK, AKT, and P70S6K was upregulated. Pre-treatment with a PI3K/AKT inhibitor (Wortmannin), ERK1/2 inhibitor (U0126), and JNK inhibitor (SP600125) induced the signaling interactions of these molecules, and oxibendazole co-treatment with each inhibitor resulted in even greater decreases in cell proliferation. Furthermore, intracellular and mitochondrial calcium ion accumulation was observed, which would mean that calcium ion homeostasis was disrupted, causing damage to the mitochondrial membrane potential. These deteriorated conditions ultimately led to apoptotic cell death. Taken together, the results of the present study identified that the apoptotic effect of oxibendazole on pTr and pLE cells is regulated by cell signaling pathways, and thus oxibendazole could influence the connection between the conceptus and the maternal uterus.

Assessment of microRNA expression in leukemic cells as predictors of sensitivity to purine nucleoside analogs, fludarabine and cladribine, in chronic lymphocytic leukemia patients

Background: Great progress has been achieved lately in the therapy for chronic lymphocytic leukemia (CLL), one of the most frequently diagnosed adult leukemias. New classes of drugs, such as kinase inhibitors and BCL-2 protein antagonists, have been approved for treatment of CLL patients. Despite the abovementioned therapies the disease can still be effectively treated with purine nucleoside analogs (PNA). However, some patients, for example, those with TP53 gene abnormalities, become resistant, and the other factors involved in the therapy resistance are still being investigated. This study was aimed at analyzing the possible role of microRNAs as markers predicting the outcome of chemotherapy based on PNA – fludarabine and cladribine in CLL patients.

Methods: The expression of miR-21, miR-34a, miR-181a and miR-221 in previously separated leukemic cells was assessed with the use of qRQ-PCR technique at the moment of diagnosis in 40 CLL patients. In turn, apoptosis induced by fludarabine and cladribine in 24-hour cell culture was evaluated by determining the increase in the percentage of apoptotic cells of CD5+/CD19+/Cas3+ phenotype, using a flow cytometry method. Nine of the 40 studied subjects were treated with fludarabine-based regimens and were analyzed with regards to in vivo response to PNA.

Results: We detected a significantly higher PNA-induced apoptosis rate in patients with high miR-34a expression in comparison to low expression ones. Interestingly, such differences were detected particularly in standard cytogenetic patients.

Conclusions: These results may prove an important role of miR-34a expression as a predictor of apoptosis, even in cases when other risk factors like cytogenetic abnormalities are absent. An assessment of microRNAs expression seems to be useful as an indicator of sensitivity to PNA and may help to predict PNA-based therapy outcome.

Total flavonoids from the Carya cathayensis Sarg. leaves inhibit HUVEC senescence through the miR-34a/SIRT1 pathway

Aging shows a significant relationship with changed vascular structure and function, and advancing age is a major nonmodifiable risk factor in the occurrence of cardiovascular diseases. The senescence of endothelial cells is one of the hallmarks of vascular aging and can induce vascular dysfunction. This study aimed to investigate the effect of total flavonoids (TFs) on human umbilical vein endothelial cells (HUVEC) senescence and identify the potential mechanisms involved. A HUVEC senescence model was induced by angiotensin II. The senescence markers, including senescence-associated β-galactosidase (SA-β-gal), p53, p21, and stagnate G0/G1, were measured. The effects of TFs on miR-34/ SIRT1 were examined by quantitative polymerase chain reaction analysis and Western blot analysis. TFs decreased the percentage of SA-β-gal-positive cells and resulted in G0/G1 cell cycle arrest, while the percentage of cells in the S phase increased. Furthermore, TFs reduced miR-34a expression and increased the expression of SIRT1. After treatment with TFs and a miR-34a inhibitor, the percentage of SA-β-gal-positive cells and the expression of miR-34a decreased, and the expression of SIRT1 increased. The TFs inhibited HUVEC senescence, and the mechanism was related to the miR-34a/Sirtuin1 pathway.

Molecular characterization of the cyclin-dependent protein kinase 6 in whitefish (Coregonus lavaretus) and its potential interplay with miR-34a

Cyclin-dependent protein kinase 6 (CDK6) plays a pivotal role in the regulation of the cell cycle and cell proliferation in mammals, and disruption of its expression by various microRNAs has been implicated in the pathogenesis of multiple human cancers. In mammals, miR-34a acts as a downstream effector of p53, and thus indirectly targets Cdk6, abrogating its effects. However, no studies have been done so far to examine the mechanistic involvement of miR-34a in the silencing of cdk6 in fish. In the present study, we found that the cDNA sequence of whitefish cdk6 has a 3'UTR region that contains a binding site for miR-34a. Using a luciferase reporter assay, we demonstrated that whitefish cdk6 is a direct target of miR-34a in vitro. In order to confirm this relationship in vivo, we measured the miR-34a and cdk6 mRNA expression patterns in the liver of whitefish after short-term (8, 24, and 48 h) and long-term (14 and 28 days) exposure to microcystin-LR (MC-LR), a known hepatotoxin and tumor promoter. In contrast to the in vitro findings, we noticed an up-regulation of miR-34a and cdk6 expression after long-term MC-LR treatment. While these results indicate that both, miR-34a and cdk6 are responsive to MC-LR treatment, they do not support the presence of a miR-34a:cdk6 mRNA regulatory pair in the MC-LR-challanged whitefish liver in vivo. On the other hand, our findings suggests that cell regulatory elements, partnering with either miR-34a or cdk6, are worthy of further screening to better understand the molecular mechanisms that underlie the physiological response of fish challenged with hepatotoxic environmental pollutants like microcystins.

Association between TP53 genetic polymorphisms and the methylation and expression of miR-34a, 34b/c in colorectal cancer tissues

Colorectal cancer (CRC) is one of the most common types of cancers, as evidenced by the >1.2 million patient diagnoses and 600,000 mortalities globally each year. Recently, the microRNA (miR/miRNA)-34 miRNA precursor family was revealed to participate in the tumor protein (TP)-53 pathway, which is frequently involved in CRC. Furthermore, the expression of miR-34 is reportedly regulated by DNA methylation. Accordingly, the present study investigated the correlation between the methylation status of miR-34 miRNAs and miR-34 expression in paired CRC tumor and normal tissues. The methylation status of miR-34a and miR-34b/c was determined using the MethyLight assay, and the expression of miR-34a and miR-34b/c in the same paired tissues was analyzed by reverse transcription-quantitative polymerase chain reaction. The results revealed significantly elevated miR-34a (P=0.012) and miR-34b/c (P<0.0001) methylation levels in tumor tissues when compared with normal tissues, whereas only the expression of miR-34b/c differed (P=0.005) between the paired tissues. In addition, an association between TP53 haplotypes and miR-34 family expression levels was observed. The miR-34a methylation levels in the TP53 PIN A1A1 (48.56±36.49) and TP53 MSP GG (49.00±36.44) genotypes were increased in the tumor tissues when compared with normal tissues. In conclusion, it was determined that miR-34 promoter methylation and TP53 polymorphisms may be associated with CRC pathogenesis.

Down-regulation of microRNA-34a-5p promotes trophoblast cell migration and invasion via targetting Smad4

Trophoblastic dysfunction, such as insufficient migration and invasion, is well-known to be correlated with preeclampsia (PE). Recently, microRNAs (miRNAs) have been implicated in diverse biological processes and human diseases, including PE. However, the expression and functions of miRNAs in the progression of PE, especially in the regulation of trophoblast cell migration and invasion remain largely unclear. Here, we compared the miRNAs expression profiles of PE patients with healthy controls using microarray assay and chose a significant increased miRNA-miR-34a-5p for further investigation. Overexpression of miR-34a-5p dramatically reduced migration and invasion in trophoblast HTR-8/SVneo cells, whereas enhanced by its inhibitor. Luciferase activity assay showed that miR-34a-5p directly target Smad family member 4 (Smad4), which is associated with cancer cell invasiveness and metastasis. We also found that Smad4 was down-regulated in PE patients, and an inverse relationship between Smad4 and miR-34a-5p expression levels was observed in placental tissues from PE patients. Further study showed that knockdown of Smad4 effectively attenuated the promoting effects of miR-34a-5p inhibition on the migration and invasion of HTR-8/SVneo cells. Taken together, these findings suggest that inhibition of miR-34a-5p improves invasion and migration of trophoblast cells by directly targetting Smad4, which indicated the potential of miR-34a-5p as a therapeutic target against PE.

Exploiting epigenetically mediated changes: Acute myeloid leukemia, leukemia stem cells and the bone marrow microenvironment

Acute myeloid leukemia (AML) derives from the clonal expansion of immature myeloid cells in the bone marrow, and results in the disruption of normal hematopoiesis and subsequent bone marrow failure. The bone marrow microenvironment (BME) and its immune and other supporting cells are regarded to facilitate the survival, differentiation and proliferation of leukemia stem cells (LSCs), which enables AML cells to persist and expand despite treatment. Recent studies have identified epigenetic modifications among AML cells and BME constituents in AML, and have shown that epigenetic therapy can potentially reprogram these alterations. In this review, we summarize the interactions between the BME and LSCs, and discuss changes in how the BME and immune cells interact with AML cells. After describing the epigenetic modifications seen across chromatin, DNA, the BME, and the immune microenvironment, we explore how demethylating agents may reprogram these pathological interactions, and potentially re-sensitize AML cells to treatment.

NFAT5 is Regulated by p53/miR-27a Signal Axis and Promotes Mouse Ovarian Granulosa Cells Proliferation

MicroRNAs (miRNAs) play key roles in mammalian folliculogenesis (a complex process in which primordial follicles develop into mature oocytes) by inhibiting mRNA translation or by inducing its degradation, while the role of miRNA in folliculogenesis and regulation mechanism remain unclear. In this study, we explored the role of the p53/miR-27a/nuclear factor of activated T-cells 5 (NFAT5) signaling axis in mouse ovarian granulosa cell proliferation. Luciferase reporter assay, overexpression, site-directed mutagenesis, and chromatin immunoprecipitation (ChIP) assay results showed that the transcription factor p53 significantly decreased the expression level of miR-27a by binding to sites 4 (-646 to -637 bp) and 10 (-50 to -41 bp) of the miR-27a promoter. Moreover, miR-27a directly targeted the 3′-untranslated region of the target gene, NFAT5, to regulate its expression levels. p53 also upregulated the expression of NFAT5. Meanwhile, overexpression of NFAT5 strongly upregulated the mRNA and protein levels of the Wnt signaling genes, β-catenin and B-Cell CLL/Lymphoma 2 (Bcl-2). In addition, NFAT5 promoted mouse granulosa cell proliferation; this was confirmed by EdU/Hoechst immunostaining. Taken together, our findings define a novel pathway p53/miR-27a/NFAT5, and NFAT5 regulates mouse granulosa cell functions via activating Wnt signaling pathway.

Evaluation of pre-mir-34a rs72631823 single nucleotide polymorphism in triple negative breast cancer: A case-control study

AIM

The purpose of this study is to evaluate the role of pre-miR34a rs72631823 as potential risk factor and/or prognostic marker in patients with triple negative breast cancer.

METHODS

114 samples of DNA from paraffin embedded breast normal tissues of patients with triple negative breast cancer and 124 samples of healthy controls were collected and analyzed for pre-miR34a rs72631823 polymorphism.

RESULTS

Pre-miR34a rs72631823 A allele was associated with increased TNBC risk both in univariate and multivariate analysis. The number of pre-miR34a rs72631823 AA subjects was very small and the association did not reach significance (p = 0.176, Fisher's exact test). The examined polymorphism was not associated with overall survival at the univariate or multivariate Cox regression analysis (adjusted HR = 1.60, 95%CI: 0.64-3.96 for miR34 rs72631823 GA/AA vs. GG).

CONCLUSION

Our case-control study suggests that pre-miR34a rs72631823 A allele is associated with increased triple negative breast cancer risk.

Expression levels of miR-34-family microRNAs are associated with TP53 mutation status in head and neck squamous cell carcinoma

PURPOSE

The majority of head and neck squamous cell carcinoma (HNSCC) cases in developing countries are associated with cigarette smoking and TP53 mutations. p53 is a transcription factor that activates downstream genes, including the hsa-miR-34a and hsa-miR-34b/c loci, to achieve cell-cycle arrest, senescence, and/or apoptosis. This study examined the differences in expression levels of miR-34 in HNSCC with or without TP53 mutations.

METHODS

We examined surgically resected tumor samples and normal adjacent tissues from HNSCC in oral cavity, larynx, and hypopharynx for TP53 mutations (exons 5-8) and miR-34 expression levels.

RESULTS

miR-34a, miR-34b, miR-34b*, and miR-34c are significantly up-regulated in tumors with wild-type TP53 genes (n = 23); while such up-regulation is not observed in tumors with mutant TP53 (n = 19). Although expression levels of miR-34-family miRNAs do not correlate with gender, age, or tumor staging, interestingly they are correlated with smoking status and tumor sites. miR-34b/b*/c are up-regulated in tumors from those who ever smoked or recently smoked (quit smoking less than 15 years ago); but such up-regulation was not seen in those who never smoked or quit smoking for at least 15 years. HNSCC of the oral cavity also up-regulated miR-34b/b*/c while no such overexpression was observed in HNSCC of the larynx and hypopharynx.

CONCLUSIONS

Surgically resected HNSCC samples with no TP53 mutations have elevated levels of miR-34a and miR-34b/b*/c, while those with TP53 mutations show no such up-regulation. miR-34b/b*/c expression is also correlated with smoking status and tumor sites.

Integration of "Omics" Strategies for Biomarkers Discovery and for the Elucidation of Molecular Mechanisms Underlying Brugada Syndrome

PURPOSE

The Brugada syndrome (BrS) is a severe inherited cardiac disorder. Given the high genetic and phenotypic heterogeneity of this disease, three different "omics" approaches are integrated in a synergic way to elucidate the molecular mechanisms underlying the pathophysiology of BrS as well as for identifying reliable diagnostic/prognostic markers.

EXPERIMENTAL DESIGN

The profiling of plasma Proteome and MiRNome is perfomed in a cohort of Brugada patients that were preliminary subjected to genomic analysis to assess a peculiar gene mutation profile.

RESULTS

The integrated analysis of "omics" data unveiled a cooperative activity of mutated genes, deregulated miRNAs and proteins in orchestrating transcriptional and post-translational events that are critical determining factors for the development of the Brugada pattern.

CONCLUSIONS AND CLINICAL RELEVANCE

This study provides the basis to shed light on the specific molecular fingerprints underlying BrS development and to gain further insights on the pathogenesis of this life-threatening cardiac disease.

Clustered miRNAs and their role in biological functions and diseases

MicroRNAs (miRNAs) are endogenous, small non-coding RNAs known to regulate expression of protein-coding genes. A large proportion of miRNAs are highly conserved, localized as clusters in the genome, transcribed together from physically adjacent miRNAs and show similar expression profiles. Since a single miRNA can target multiple genes and miRNA clusters contain multiple miRNAs, it is important to understand their regulation, effects and various biological functions. Like protein-coding genes, miRNA clusters are also regulated by genetic and epigenetic events. These clusters can potentially regulate every aspect of cellular function including growth, proliferation, differentiation, development, metabolism, infection, immunity, cell death, organellar biogenesis, messenger signalling, DNA repair and self-renewal, among others. Dysregulation of miRNA clusters leading to altered biological functions is key to the pathogenesis of many diseases including carcinogenesis. Here, we review recent advances in miRNA cluster research and discuss their regulation and biological functions in pathological conditions.

miR‑34a regulates the chemosensitivity of retinoblastoma cells via modulation of MAGE‑A/p53 signaling

The present study aimed to explore the combined role of microRNA (miR)-34a, melanoma antigen-A (MAGE‑A) and p53 in altering the chemosensitivity of retinoblastoma (RB) cells. Human RB and adjacent tumor tissues, as well as human RB cell lines (HXO‑Rb44, SO‑Rb50, Y79 and WERI‑Rb-1) were used. In addition, four chemotherapeutic drugs, including carboplatin, etoposide, Adriamycin and vincristine, were used to treat the cell lines, in order to evaluate the sensitivity of RB cells. Furthermore, miR‑34a expression was detected by reverse transcription-quantitative polymerase chain reaction, and western blotting was implemented to quantify expression levels of MAGE‑A and p53. A luciferase reporter gene assay was used to validate the targeted association between miR‑34a and MAGE‑A. The results indicated that SO‑Rb50 cells exhibited the highest resistance to carboplatin, Adriamycin and vincristine (P<0.05), whereas HXO‑Rb44 cells revealed the highest inhibition rate in response to etoposide (P<0.05) out of the four cell lines. Furthermore, reduced miR‑34a expression and increased MAGE‑A expression significantly elevated the survival rate and viability of SO‑Rb50 cells following drug treatment (all P<0.05). miR‑34a was also demonstrated to directly target MAGE‑A, thereby significantly promoting the viability of RB cells and depressing apoptosis (P<0.05). p53, which was subjected to modulation by miR‑34a and MAGE‑A, also significantly reduced the proliferation rate of RB cells (P<0.05). In conclusion, the miR‑34a/MAGE‑A/p53 axis may be conducive to enhancing the efficacies of chemotherapeutic treatments for RB.

The clinical impact of miRNA34a and P53 gene expression in colon cancer

Objective

To study the potential role of miRNA34a gene expression and its relationship with P53 gene expression, fate, stage, metastasis and overall survival of colorectal cancer.

Patients and methods

This study was carried out 30 patients with colon adenocarcinoma, 30 patients with benign colon polyp and 30 apparently healthy persons served as controls. All participants were subjected to full history taking, general clinical examination. Complete blood count, liver and kidney function, determination of serum tumor markers were done. Estimation of microRNA 34a and P53 Gene expression by real-time PCR were done.

Results

There was a significant negative relationship between serum tumor markers and micro RNA 34a gene expression in cancer patients. Also, there was a statistically significant positive relationship between miRNA34a gene expression and P53 gene expression in both patients groups. The diagnostic accuracy of miRNA34a gene expression was both sensitive and specific for colon cancer. MiRNA34a and P53 gene expression had statistically significant relation with tumor stage and presence of metastases.

Conclusion

It can be concluded that the level of miRNA34a can be used to differentiate between colon cancers and begin adenomas. MiRNA34a can be used as a prognostic marker in colon cancer.

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MiRNA34a has an important role in colon cancer.

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Presence of correlation between P53 and miRNA34a gene expression.

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MiRNA34a can be used as a prognostic marker in colon cancer.

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MiRNA34a can be used to differentiate between colon cancer and benign adenoma.

MicroRNA-34a inhibits metastasis in liver cancer cells

MicroRNAs (miRNA/miRs) have the ability to target specific mRNAs, resulting in degradation of mRNA or inhibition of translation. Notably, miR-34a is able to regulate cell cycle and tumorigenicity. The level of miR-34a expression is usually low in tumors, and previous studies have indicated miR-34a to be an important tumor suppressor. In order to elucidate the association between miR-34a and metastasis, stable cell lines were established and transfected with miR-34a. Cell invasion assay was subsequently performed. The present study demonstrated that cell invasion was inhibited in cells that were transfected with miR-34a compared with the control group (P<0.05). Therefore, miR-34a was able to inhibit metastasis in liver cancer cells.

miR-34 regulates reproduction by inhibiting the expression of MIH, CHH, EcR, and FAMeT genes in mud crab Scylla paramamosain

Mud crab Scylla paramamosain is a commercially important species widely cultured in China. It is well known that the eyestalk regulates reproductive activities in crustaceans. In our previous research, we found that the miR-34 expression level in male eyestalk was significantly higher than that in females. Thus, we assumed that it may play an important role in regulating reproduction. In this study, we used bioinformatic tools to identify the target genes of miR-34 in eyestalk. Six reproduction-related genes with an intact 3'-untranslated region (UTR), including molt-inhibiting hormone (MIH), crustacean hyperglycemic hormone (CHH), vitellogenesis-inhibiting hormone, red pigment concentrating hormone, ecdysone receptor (EcR), and farnesoic acid methyltransferase (FAMeT) were identified. When the 3'-UTR plasmid vectors of the six genes were cotransfected with miR-34 mimics into 293FT cells, respectively, the luciferase activities of four genes (MIH, CHH, EcR, and FAMeT) were significantly decreased compared with that in the control group; on the contrary, when the six plasmid vectors were cotransfected with the miR-34 inhibitor respectively, the luciferase activities of four genes (MIH, CHH, EcR, and FAMeT) were significantly higher than that in the control group. When agomiR-34 and antagomiR-34 were injected into the eyestalk respectively in vivo, the expression levels of the MIH, CHH, EcR, and FAMeT genes were detected by a quantitative real-time polymerase chain reaction. The results showed that agomiR-34 suppressed the expression of the four genes, whereas antagomiR-34 enhanced their expression. These experimental results confirmed our hypothesis that miR-34 may indirectly regulate reproduction via binding to the 3'-UTRs of MIH, CHH, EcR, and FAMeT genes and suppressing their expression.

MicroRNA-493 targets STMN-1 and promotes hypoxia-induced epithelial cell cycle arrest in G2/M and renal fibrosis

Hypoxia plays an important role in the development of renal fibrosis. G₂/M arrest in renal tubular cells is an important pathway in the development of chronic kidney disease. It is unknown whether hypoxia leads to renal fibrosis via the regulation of G₂/M arrest in renal tubular epithelial cells. For the first time, to our knowledge, we showed that hypoxia induces G₂/M arrest in renal tubular cells leading to renal fibrosis, and microRNAs are involved in this regulation. We compared microRNA expression between hypoxia and normoxia in HK2 cells and found microRNA (miR)-493 to be highly expressed at 24 and 48 h after hypoxia. The overexpression of miR-493 reduced the expression of the cell cycle regulator, Stathmin (STMN)-1, and increased the percentage of G₂/M phase cells and profibrotic factors in HK2 cells. Targeting STMN-1 with short hairpin RNA produced an effect similar to that of miR-493 overexpression. On contrast, the miR-493 inhibitor reversed these effects in vitro. Consistent with these results, miR-493 sponge adeno-associated virus reduced the expression of profibrotic factors and increased STMN-1 in vivo. In summary, these results suggest that the miR-493-STMN-1 pathway contributes to hypoxia-induced tubular epithelial cell G₂/M arrest and renal fibrosis. Abrogating G₂/M arrest and blocking the miR-493-STMN-1 pathway will provide further insight for the development of antifibrosis therapy.-Liu, T., Liu, L., Liu, M., Du, R., Dang, Y., Bai, M., Zhang, L., Ma, F., Yang, X., Ning, X., Sun, S. MicroRNA-493 targets STMN-1 and promotes hypoxia-induced epithelial cell cycle arrest In G₂/M and renal fibrosis.

The Effect of Newly Synthesized Heterosteroids on miRNA34a, 98, and 214 Expression Levels in MCF-7 Breast Cancer Cells

Hybrid anticancer drugs have emerged as great therapeutic options that can effectively overcome most obstacles facing conventional anticancer drugs. miRNAs are considered as class of non-coding RNAs that can negatively regulate protein coding gene expression. miRNA expression is commonly altered in cancer cells. The current work aimed to test the effect of new pro-apoptotic heterosteroids on some drug resistance related miRNAs expression levels (miRNA34a, 98, and 214) in MCF-7 breast cancer cells. After cell treatment with these compounds 4, 6, 7, 13, 18, 21, 22 and 24, miRNAs were extracted and subjected to reverse transcription and subsequent PCR amplification using Real Time-PCR technique. The expression levels of miR-34a, miR-98 and miR-214 were quantitatively determined. The study revealed that the expression levels of miR-34a, miR-98 and miR-214 were up-regulated upon treatment with tamoxifen, which was used as a positive control drug, as compared to control cells,. Strikingly, the levels of miR-34a, miR-98 and miR-214 expression were significantly down-regulated when treated with most of the new heterosteroids as compared to control cells. These results could indicate the promising effects of these new heterosteroids on reducing drug resistance as compared to tamoxifen drug. As well established, cells develop drug resistance to tamoxifen.

Neural stem cell differentiation into mature neurons: Mechanisms of regulation and biotechnological applications

The abilities of stem cells to self-renew and form different mature cells expand the possibilities of applications in cell-based therapies such as tissue recomposition in regenerative medicine, drug screening, and treatment of neurodegenerative diseases. In addition to stem cells found in the embryo, various adult organs and tissues have niches of stem cells in an undifferentiated state. In the central nervous system of adult mammals, neurogenesis occurs in two regions: the subventricular zone and the dentate gyrus in the hippocampus. The generation of the different neural lines originates in adult neural stem cells that can self-renew or differentiate into astrocytes, oligodendrocytes, or neurons in response to specific stimuli. The regulation of the fate of neural stem cells is a finely controlled process relying on a complex regulatory network that extends from the epigenetic to the translational level and involves extracellular matrix components. Thus, a better understanding of the mechanisms underlying how the process of neurogenesis is induced, regulated, and maintained will provide elues for development of novel for strategies for neurodegenerative therapies. In this review, we focus on describing the mechanisms underlying the regulation of the neuronal differentiation process by transcription factors, microRNAs, and extracellular matrix components.

CRISPR-Based Editing Reveals Edge-Specific Effects in Biological Networks

Unraveling the properties of biological networks is central to understanding both normal and disease cellular phenotypes. Networks consist of functional elements (nodes) that form a variety of diverse connections (edges), with each node being a hub for multiple edges. Herein, in contrast to node-centric network perturbation and analysis approaches, we present a high-throughput CRISPR-based methodology for delineating the role of network edges. Ablation of network edges using a library targeting 93 miRNA target sites in 71 genes reveals numerous edges that control, with variable importance, cellular growth and survival under stress. To compare the impact of removing nodes versus edges in a biological network, we dissect a specific p53-microRNA pathway. We show that removal of the miR-34a target site from the anti-apoptotic gene BCL2 desensitizes the cell to ectopic delivery of miR-34a in a p53-dependent manner. In summary, we demonstrate that network edges are critical to the function and stability of biological networks. Our results introduce a novel genetic screening opportunity via edge ablation and highlight a new dimension in biological network analysis.

Noncoding RNAs in disease

Noncoding RNAs are emerging as potent and multifunctional regulators in all biological processes. In parallel, a rapidly growing number of studies has unravelled associations between aberrant noncoding RNA expression and human diseases. These associations have been extensively reviewed, often with the focus on a particular microRNA (miRNA) (family) or a selected disease/pathology. In this Mini‐Review, we highlight a selection of studies in order to demonstrate the wide‐scale involvement of miRNAs and long noncoding RNAs in the pathophysiology of three types of diseases: cancer, cardiovascular and neurological disorders. This research is opening new avenues to novel therapeutic approaches.

Role of MicroRNAs in Pathophysiology of Non-alcoholic Fatty Liver Disease and Non-alcoholic Steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disorder worldwide. It includes wide range of diseases from different subtypes of simple steatosis to non-alcoholic steatohepatitis (NASH), which may be complicated by liver fibrosis, cirrhosis, or hepatocellular carcinoma. Of the epigenetic factors that play a key role in the progression of it, is microRNAs (miRNAs).

MiRNAs are short non-coding RNAs of 22-23 nucleotides in length, which regulate a large number of genes that have a critical role in regulation of lipid and cholesterol biosynthesis in hepatocytes. MiRNAs can be used as a very powerful biomarker to diagnosis and follow-up any disorder, such as NAFLD and NASH with a high specificity and sensitivity. The aim of this study was to review the role of different miRNAs in the pathophysiology of NASH and NAFLD

Endothelial Cell Aging: How miRNAs Contribute?

Endothelial cells (ECs) form monolayers and line the interior surfaces of blood vessels in the entire body. In most mammalian systems, the capacity of endothelial cells to divide is limited and endothelial cells are prone to be senescent. Aging of ECs and resultant endothelial dysfunction lead to a variety of vascular diseases such as atherosclerosis, diabetes mellites, hypertension, and ischemic injury. However, the mechanism by which ECs get old and become senescent and the impact of endothelial senescence on the vascular function are not fully understood. Recent research has unveiled the crucial roles of miRNAs, which are small non-coding RNAs, in regulating endothelial cellular functions, including nitric oxide production, vascular inflammation, and anti-thromboformation. In this review, how senescent-related miRNAs are involved in controlling the functions of ECs will be discussed.

An antisense RNA capable of modulating the expression of the tumor suppressor microRNA-34a

The microRNA-34a is a well-studied tumor suppressor microRNA (miRNA) and a direct downstream target of TP53 with roles in several pathways associated with oncogenesis, such as proliferation, cellular growth, and differentiation. Due to its broad tumor suppressive activity, it is not surprising that miR34a expression is altered in a wide variety of solid tumors and hematological malignancies. However, the mechanisms by which miR34a is regulated in these cancers is largely unknown. In this study, we find that a long noncoding RNA transcribed antisense to the miR34a host gene, is critical for miR34a expression and mediation of its cellular functions in multiple types of human cancer. We name this long noncoding RNA lncTAM34a, and characterize its ability to facilitate miR34a expression under different types of cellular stress in both TP53-deficient and wild-type settings.

miR-34a directly targets tRNAiMet precursors and affects cellular proliferation, cell cycle, and apoptosis

It remains unknown whether microRNA (miRNA/miR) can target transfer RNA (tRNA) molecules. Here we provide evidence that miR-34a physically interacts with and functionally targets tRNA_i^Met precursors in both in vitro pulldown and Argonaute 2 (AGO2) cleavage assays. We find that miR-34a suppresses breast carcinogenesis, at least in part by lowering the levels of tRNA_i^Met through AGO2-mediated repression, consequently inhibiting the proliferation of breast cancer cells and inducing cell cycle arrest and apoptosis. Moreover, miR-34a expression is negatively correlated with tRNA_i^Met levels in cancer cell lines. Furthermore, we find that tRNA_i^Met knockdown also reduces cell proliferation while inducing cell cycle arrest and apoptosis. Conversely, ectopic expression of tRNA_i^Met promotes cell proliferation, inhibits apoptosis, and accelerates the S/G2 transition. Moreover, the enforced expression of modified tRNA_i^Met completely restores the phenotypic changes induced by miR-34a. Our results demonstrate that miR-34a directly targets tRNA_i^Met precursors via AGO2-mediated cleavage, and that tRNA_i^Met functions as an oncogene, potentially representing a target molecule for therapeutic intervention.

Methylation profiles of miR34 gene family in Vietnamese patients suffering from breast and lung cancers

The three genes encoding small non‑coding microRNA (miR)34a, MIR34b and MIR34c act as tumor‑suppressor genes. Their aberrant expressions regulated by DNA methylation have been frequently found in various types of cancer. In the present study, the DNA promoter methylation profiles of the MIR34 gene family were analyzed using the methylation specific polymerase chain reaction in order to clarify their association with breast and lung cancer, non‑cancerous or normal adjacent tissues. The methylation frequency of MIR34a was significantly higher in breast cancer (49.37%) compared with normal adjacent tissues (30.38%). The methylation frequency of MIR34b/c was 59.49 and 62.03% in breast cancer and normal adjacent tissues, respectively. MIR34a methylation showed a significant concordance with that of MIR34b/c only in breast cancer tissue. MIR34a methylation was significantly associated with cancer and the invasive ductal carcinoma type of breast cancer (P=0.015 and P=0.02, respectively). Methylation frequency of MIR34a and MIR34b/c was 48.42 and 56.84% in lung cancer, and 47.22 and 51.39% in pulmonary diseases, respectively. No significant association was observed between the methylation status of MIR34a and MIR34b/c, and the clinicopathological features of lung cancer or with those of non‑cancerous pulmonary diseases. Promoter methylation of MIR34a and MIR34b/c occurs frequently and concomitantly in breast and lung cancer, as well as in pulmonary diseases tissues, but not in breast normal tissues adjacent to tumor. These results of the present study emphasize the involvement of MIR34 methylation in human diseases, including cancer. Furthermore, MIR34a methylation may be a promising marker for a subtype of breast cancer.

The p53-signaling pathway and colorectal cancer: Interactions between downstream p53 target genes and miRNAs

INTRODUCTION

We examined expression of genes in the p53-signaling pathway. We determine if genes that have significantly different expression in carcinoma tissue compared to normal mucosa also have significantly differentially expressed miRNAs. We utilize a sample of 217 CRC cases.

METHODS

We focused on fold change (FC) > 1.50 or <0.67 for genes and miRNAs, that were statistically significant after adjustment for multiple comparisons. We evaluated the linear association between the differential expression of miRNA and mRNA. miRNA:mRNA seed-region matches also were determined.

RESULTS

Eleven dysregulated genes were associated with 37 dysregulated miRNAs; all were down-stream from the TP53 gene. MiR-150-5p (HR = 0.82) and miR-196b-5p (HR 0.73) significantly reduced the likelihood of dying from CRC when miRNA expression increased in rectal tumors.

CONCLUSIONS

Our data suggest that activation of p53 from cellular stress, could target downstream genes that in turn could influence cell cycle arrest, apoptosis, and angiogenesis through mRNA:miRNA interactions.

DNA Damage-Response Pathway Heterogeneity of Human Lung Cancer A549 and H1299 Cells Determines Sensitivity to 8-Chloro-Adenosine

Human lung cancer H1299 (p53-null) cells often display enhanced susceptibility to chemotherapeutics comparing to A549 (p53-wt) cells. However, little is known regarding to the association of DNA damage-response (DDR) pathway heterogeneity with drug sensitivity in these two cells. We investigated the DDR pathway differences between A549 and H1299 cells exposed to 8-chloro-adenosine (8-Cl-Ado), a potential anticancer drug that can induce DNA double-strand breaks (DSBs), and found that the hypersensitivity of H1299 cells to 8-Cl-Ado is associated with its DSB overaccumulation. The major causes of excessive DSBs in H1299 cells are as follows: First, defect of p53-p21 signal and phosphorylation of SMC1 increase S phase cells, where replication of DNA containing single-strand DNA break (SSB) produces more DSBs in H1299 cells. Second, p53 defect and no available induction of DNA repair protein p53R2 impair DNA repair activity in H1299 cells more severely than A549 cells. Third, cleavage of PARP-1 inhibits topoisomerase I and/or topoisomerase I-like activity of PARP-1, aggravates DNA DSBs and DNA repair mechanism impairment in H1299 cells. Together, DDR pathway heterogeneity of cancer cells is linked to cancer susceptibility to DNA damage-based chemotherapeutics, which may provide aid in design of chemotherapy strategy to improve treatment outcomes.

Bioinformatics functional analysis of let-7a, miR-34a, and miR-199a/b reveals novel insights into immune system pathways and cancer hallmarks for hepatocellular carcinoma

Let-7a, miR-34a, and miR-199 a/b have gained a great attention as master regulators for cellular processes. In particular, these three micro-RNAs act as potential onco-suppressors for hepatocellular carcinoma. Bioinformatics can reveal the functionality of these micro-RNAs through target prediction and functional annotation analysis. In the current study, in silico analysis using innovative servers (miRror Suite, DAVID, miRGator V3.0, GeneTrail) has demonstrated the combinatorial and the individual target genes of these micro-RNAs and further explored their roles in hepatocellular carcinoma progression. There were 87 common target messenger RNAs (p ≤ 0.05) that were predicted to be regulated by the three micro-RNAs using miRror 2.0 target prediction tool. In addition, the functional enrichment analysis of these targets that was performed by DAVID functional annotation and REACTOME tools revealed two major immune-related pathways, eight hepatocellular carcinoma hallmarks-linked pathways, and two pathways that mediate interconnected processes between immune system and hepatocellular carcinoma hallmarks. Moreover, protein-protein interaction network for the predicted common targets was obtained by using STRING database. The individual analysis of target genes and pathways for the three micro-RNAs of interest using miRGator V3.0 and GeneTrail servers revealed some novel predicted target oncogenes such as SOX4, which we validated experimentally, in addition to some regulated pathways of immune system and hepatocarcinogenesis such as insulin signaling pathway and adipocytokine signaling pathway. In general, our results demonstrate that let-7a, miR-34a, and miR-199 a/b have novel interactions in different immune system pathways and major hepatocellular carcinoma hallmarks. Thus, our findings shed more light on the roles of these miRNAs as cancer silencers.

Regulatory role of resveratrol, a microRNA-controlling compound, in HNRNPA1 expression, which is associated with poor prognosis in breast cancer

Certain lifestyles, such as unhealthy eating habits, are associated with an increased risk for several diseases, including cancer. Recently, some naturally occurring compounds, such as resveratrol, have been shown to regulate microRNA (miRNA) expression in a positive manner; this regulatory activity is likely to be advantageous for cancer prevention and treatment. Resveratrol, a multi-functional polyphenolic phytoalexin, has been known to exert anti-tumorigenic and anti-inflammatory effects and to regulate miRNA expression. However, our understanding of the underlying molecular mechanisms whereby resveratrol controls cancer cell growth via the regulation of miRNA and oncogenic target gene expression to inhibit disease progression remains incomplete. Here we show that resveratrol controls breast cancer cell proliferation by inducing tumor-suppressive miRNAs (miR-34a, miR-424, and miR-503) via the p53 pathway and then by suppressing heterogeneous nuclear ribonucleoprotein A1 (HNRNPA1), which is associated with tumorigenesis and tumor progression. Notably, HNRNPA1 was directly regulated by miR-424 and miR-503, the expression of which were mediated by resveratrol. Moreover, we found that resveratrol exerts broad effects on the HNRNPA1-related pre-mRNA splicing pathway. Our data provide novel insights into the regulatory roles of resveratrol for preventing and treating of diseases.

Expression of miR-34a in T-Cells Infected by Human T-Lymphotropic Virus 1

Human T-lymphotropic virus 1 (HTLV-1) immortalizes T-cells and is the causative agent of adult T-cell leukemia/lymphoma (ATLL). HTLV-1 replication and transformation are governed by multiple interactions between viral regulatory proteins and host cell factors that remain to be fully elucidated. The present study investigated the impact of HTLV-1 infection on the expression of miR-34a, a microRNA whose expression is downregulated in many types of cancer. Results of RT-PCR assays showed that five out of six HTLV-1-positive cell lines expressed higher levels of miR-34a compared to normal PBMC or purified CD4+ T-cells. ATLL cell line ED, which did not express miR-34a, showed methylation of the miR-34a promoter. Newly infected PBMC and samples from 10 ATLL patients also showed a prominent increase in miR-34a expression compared to PBMC controls. The primary miR-34a transcript expressed in infected cell line C91PL contained binding motifs for NF-κB and p53. Pharmacological inhibition of NF-κB with Bay 11-7082 indicated that this pathway contributes to sustain miR-34a levels in infected cells. Treatment of infected cell lines with the p53 activator nutlin-3a resulted in a further increase in miR-34a levels, thus confirming it as a transcriptional target of p53. Nutlin-3a-treated cells showed downregulation of known miR-34a targets including the deacetylase SIRT1, which was accompanied by increased acetylation of p53, a substrate of SIRT1. Transfection of C91PL cells with a miR-34a mimic also led to downregulation of mRNA targets including SIRT1 as well as the pro-apoptotic factor BAX. Unlike nutlin-3a, the miR-34a mimic did not cause cell cycle arrest or reduce cell viability. On the other hand, sequestration of miR-34a with a sponge construct resulted in an increase in death of C91PL cells. These findings provide evidence for a functional role for miR-34a in fine-tuning the expression of target genes that influence the turnover of HTLV-1-infected cells.

Epigenetic Contribution of High-Mobility Group A Proteins to Stem Cell Properties

High-mobility group A (HMGA) proteins have been examined to understand their participation as structural epigenetic chromatin factors that confer stem-like properties to embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs), and cancer stem cells (CSCs). The function of HMGA was evaluated in conjunction with that of other epigenetic factors such as histones and microRNAs (miRs), taking into consideration the posttranscriptional modifications (PTMs) of histones (acetylation and methylation) and DNA methylation. HMGA proteins were coordinated or associated with histone and DNA modification and the expression of the factors related to pluripotency. CSCs showed remarkable differences compared with ESCs and iPSCs.

Micro-Economics of Apoptosis in Cancer: ncRNAs Modulation of BCL-2 Family Members

In the last few years, non-coding RNAs (ncRNAs) have been a hot topic in cancer research. Many ncRNAs were found to regulate the apoptotic process and to play a role in tumor cell resistance to treatment. The apoptotic program is on the frontline as self-defense from cancer onset, and evasion of apoptosis has been classified as one of the hallmarks of cancer responsible for therapy failure. The B-cell lymphoma 2 (BCL-2) family members are key players in the regulation of apoptosis and mediate the activation of the mitochondrial death machinery in response to radiation, chemotherapeutic agents and many targeted therapeutics. The balance between the pro-survival and the pro-apoptotic BCL-2 proteins is strictly controlled by ncRNAs. Here, we highlight the most common mechanisms exerted by microRNAs, long non-coding RNAs and circular RNAs on the main mediators of the intrinsic apoptotic cascade with particular focus on their significance in cancer biology.

miR-34 modulates apoptotic gene expression in Ingenol mebutate treated keloid fibroblasts

Keloids are benign skin tumors that develop in individuals who have a positive family history of keloid disorders. Keloids are characterized by a deregulated wound-healing process, atypical fibroblasts with extreme deposition of extracellular matrix components, particularly collagen, increased cell proliferation and associated failure of apoptosis. Recently ingenol-mebutate has been used as a novel agent with anti-proliferative activity on human keloids as an alternative treatment option in patients, once conventional therapies have failed. We hypothesized that microRNAs (miR/miRNA) may be involved in the balance between lesion formation and repair. A comprehensive understanding of the molecular mechanism underlying the Ingenol-mebutate response in keloid fibroblast following Ingenol-mebutate exposure has been established previously. Therefore, the present study analyzed changes in miRNAs and apoptotic gene regulation in Ingenol-mebutate treated keloid fibroblast, by reverse transcription-quantitative polymerase chain reaction and a DNA fragmentation assay. The range of upregulated miRNAs and downregulated genes encoding cell death appeared to be associated with the degree of the morphological alterations in Ingenol-mebutate treated keloids. In particular, the upregulation of miR-34a was detected in keloid fibroblasts during and following Ingenol-mebutate exposure. Keloid fibroblasts that overexpressed miR-34a showed differential expression of genes involved in the apoptotic signaling pathway such as p53. In conclusion, the Ingenol-mebutate treatment used here was effective in reducing keloid fibroblast growth in cell culture experiments and the expression of particular miRNAs modulated the pro-apoptotic gene expression following Ingenol-mebutate treatment.

Regulation of type I collagen expression by microRNA-29 following ionizing radiation

Radiation-induced fibrosis (RIF) is thought to involve the excessive accumulation of collagen and other extracellular matrix components; previously, we reported that ionizing radiation increased the type I collagen expression and that transforming growth factor (TGF)-β was involved in this increase through activating its downstream mediator, Smad3. A recent study found that microRNAs (miRNAs)-small, noncoding sequences approximately 20 nucleotides long-negatively regulate the gene expression posttranscriptionally, and it has been suggested that miRNAs play essential roles in cellular processes, including fibrosis. However, their role in the development of RIF remains unexplored. In the present study, we examined the effects of miRNA on the expression of type I collagen induced by ionizing radiation and the mechanisms underlying the miRNA expression observed following ionizing radiation. We analyzed the regulation of miRNA following ionizing radiation by an miRNA real-time PCR, and found that miR-29 family members were downregulated in irradiated mouse fibroblasts and directly targeted type I collagen genes by specifically binding to the 3' untranslated region. We also found that the overexpression of miR-29 inhibited the ionizing radiation-induced expression of type I collagen, whereas the knockdown of miR-29 enhanced it. In addition, TGF-β/Smad-signaling significantly decreased the transcription of miR-29, whereas the inhibition of this signaling pathway cancelled this decrease. In conclusion, miR-29 was involved in the regulation of type I collagen expression through the TGF-β/Smad-signaling pathway in irradiated cells, suggesting that miR-29 may be an important regulator of RIF.

DNA methylation regulated microRNAs in human cervical cancer

Regulation of miRNA gene expression by DNA promoter methylation may represent a key mechanism to drive cervical cancer progression. In order to understand the impact of DNA promoter methylation on miRNAs at various stages of cervical carcinogenesis, we performed DNA methylation microarray on Normal Cervical Epithelium (NCE), Cervical Intraepithelial Neoplasia (CIN I-III) and Squamous Cell Carcinoma (SCC) tissues to identify differentially methylated miRNAs followed by validation by bisulfite sequencing. Further, expression of miRNAs was analyzed by qRT-PCR in clinical tissues and cervical cancer cell lines. Transcriptional activity was determined by luciferase assay. We identified a total of 69 hypermethylated and hypomethylated miRNA promoters encompassing 78 CpG islands in all except Y chromosome, among the three groups. The candidate DNA promoters of miR-424 were significantly hypermethylated and miR-200b and miR-34c were significantly hypomethylated in SCC compared to NCE (P < 0.05). Expression of miR-424, miR-200b, and miR-34c were inversely correlated with promoter DNA methylation in tissue samples. Treatment of cell lines with 5-aza-2'-deoxycytidine showed differential expression in all three miRNAs. We observed a decrease in miRNA promoter activity following in vitro SssI methylase treatment of miR-424, miR-200b, and miR-34c. Luciferase assay demonstrated that miR-200b and miR-424 functionally interacts with 3'-UTR of HIPK3 and RBBP6 respectively and decreased their activity in presence of miR-200b and miR-424 mimics transfected in SiHa cells. Taken together, we have identified deregulation of miRNAs by aberrant DNA promoter methylation, leading to its transcriptional silencing during cervical carcinogenesis, which can be potential targets for diagnosis and therapy.

MicroRNA, epigenetic machinery and lung cancer

Lung cancer is the leading cause of cancer deaths worldwide and over 80% of lung cancer patients are classified as having non-small cell lung cancer. Although there have been technological advancements in the early detection and standard treatment of lung cancer, it is often diagnosed at an advanced stage and is chemoresistant to most available drugs. A number of studies have demonstrated that microRNA is able to modulate various tumorigenic processes, including progression and metastasis, in various mechanisms. In this review we examine the most recent achievements in microRNA and lung cancer treatment and summarize the research progress on the reciprocal regulation between microRNA and epigenetic modifications, as both have been intensively studied in lung cancer. Epigenetic modifications on the human genome regulate gene and microRNA expression at the transcriptional level; inversely, microRNA can also transcriptionally cleave and/or translationally repress the expression of several key enzymes involved in epigenetic processes such as DNA methylation and histone modification. Better understanding of reciprocal regulation between microRNA and epigenetic modifications will underlie the development of novel microRNA orientated diagnostic and therapeutic strategies relating to lung cancer in the near future.