miR-24-mediated downregulation of H2AX suppresses DNA repair in terminally differentiated blood cells

Circulating miRNAs associate with historical childhood asthma hospitalization in different serum vitamin D groups

BACKGROUND

Vitamin D may help to alleviate asthma exacerbation because of its anti-inflammation effect, but the evidence is inconsistent in childhood asthma. MiRNAs are important mediators in asthma pathogenesis and also excellent non-invasive biomarkers. We hypothesized that circulating miRNAs are associated with asthma exacerbation and modified by vitamin D levels.

METHODS

We sequenced baseline serum miRNAs from 461 participants in the Childhood Asthma Management Program (CAMP). Logistic regression was used to associate miRNA expression with asthma exacerbation through interaction analysis first and then stratified by vitamin D insufficient and sufficient groups. Microarray from lymphoblastoid B-cells (LCLs) treated by vitamin D or sham of 43 subjects in CAMP were used for validation in vitro. The function of miRNAs was associated with gene modules by weighted gene co-expression network analysis (WGCNA).

RESULTS

We identified eleven miRNAs associated with asthma exacerbation with vitamin D effect modification. Of which, five were significant in vitamin D insufficient group and nine were significant in vitamin D sufficient group. Six miRNAs, including hsa-miR-143-3p, hsa-miR-192-5p, hsa-miR-151a-5p, hsa-miR-24-3p, hsa-miR-22-3p and hsa-miR-451a were significantly associated with gene modules of immune-related functions, implying miRNAs may mediate vitamin D effect on asthma exacerbation through immune pathways. In addition, hsa-miR-143-3p and hsa-miR-451a are potential predictors of childhood asthma exacerbation at different vitamin D levels.

CONCLUSIONS

miRNAs are potential mediators of asthma exacerbation and their effects are directly impacted by vitamin D levels.

Analysis of glucocorticoid receptor and microRNAs expression in pathological renal tissues

Glucocorticoid receptor (GR) is expressed in normal renal podocytes; however, its expression differs among renal diseases. The expression of GR as well as its epigenetic regulators microRNA (miR)30a, miR24 and miR370 was studied in the renal tissues of patients with systemic lupus nephritis (LN), minimal changes disease (MCD) and pauci-immune glumeronephritis (PIN). A total of 51 patients undergoing renal biopsy and 22 nephrectomised controls with no history of parenchymal renal disease were recruited from the Clinic of Nephrology and Renal Transplantation of General Laikon hospital between November 2016 and March 2019. All patients were newly-diagnosed and they were naïve of any treatment. The mRNA and protein expression were analyzed through reverse transcription-quantitative PCR and immunohistochemistry respectively. Written consent was obtained from all participants. GR mRNA expression was significantly reduced in all pathological samples compared with the 'normal' renal tissues used as controls (P=0.023 for LN, P=0.05 for MCD and P=0.004 for PIN). Similarly, GR protein expression was lower in all pathological samples (>6 GR positive podocytes/glomerulus in 50% of patients with LN and MCD and 18% with PIN) compared with controls (>6 positive podocytes/glomerulus in all the controls). PIN samples presented significantly lower GR mRNA and protein expression compared with LN and MCD samples. No significant differences were observed in the miR30a expression when comparing pathological with 'normal' renal samples. miR24 and miR370 expression demonstrated statistically significant difference in all pathological compared with 'normal' tissues. Moreover, GR expression was not significantly associated with either LN disease activity score or the response to the treatment. GR and miR24 expression was significantly reduced whereas miR370 significantly increased in all pathological compared with 'normal' renal tissues implying their protentional role in nephritis pathogenesis and treatment. Analysis of larger samples are required for more robust statistical analysis.

Melatonin targeting non-coding RNAs in cancer: Focus on mechanisms and potential therapeutic targets

Despite, melatonin is mainly known as a regulatory factor for circadian rhythm, its notable role in other fundamental biological processes, such as redox homeostasis and programmed cell death, has been found. In this line, a growing body of evidence indicated that melatonin could apply an inhibitory effect on the tumorigenic processes. Hence, melatonin might be considered an efficient adjuvant agent for cancer treatment. Besides, the physiological and pathological functions of non-coding RNAs (ncRNAs) in various disease, particularly cancers, have been expanded over the past two decades. It is well-established that ncRNAs can modulate the gene expression at various levels, thereby, ncRNAs. can regulate the numerous biological processes, including cell proliferation, cell metabolism, apoptosis, and cell cycle. Recently, targeting the ncRNAs expression provides a novel insight in the therapeutic approaches for cancer treatment. Moreover, accumulating investigations have revealed that melatonin could impact the expression of different ncRNAs in a multiple disorders, including cancer. Therefore, in the precent study, we discuss the potential roles of melatonin in modulating the expression of ncRNAs and the related molecular pathways in different types of cancer. Also, we highlighted its importance in therapeutic application and translational medicine in cancer treatment.

Epigenetic regulation of radioresistance: insights from preclinical and clinical studies

INTRODUCTION

Oftentimes, radiation therapy (RT) is ineffective due to the development of radioresistance (RR). However, studies have shown that targeting epigenetic modifiers to enhance radiosensitivity represents a promising direction of clinical investigation.

AREAS COVERED

This review discusses the mechanisms by which epigenetic modifiers alter radiosensitivity through dysregulation of MAPK-ERK and AKT-mTOR signaling. Finally, we discuss the clinical directions for targeting epigenetic modifiers and current radiology techniques used in the clinic.

METHODOLOGY

We searched PubMed and ScienceDirect databases from April 4^th, 2022 to October 18^th, 2022. We examined 226 papers related to radioresistance, epigenetics, MAPK, and PI3K/AKT/mTOR signaling. 194 papers were selected for this review. Keywords used for this search include, 'radioresistance,' 'radiosensitivity,' 'radiation,' 'radiotherapy,' 'particle radiation,' 'photon radiation,' 'epigenetic modifiers,' 'MAPK,' 'AKT,' 'mTOR,' 'cancer,' and 'PI3K.' We examined 41 papers related to clinical trials on the aforementioned topics. Outcomes of interest were safety, overall survival (OS), dose-limiting toxicities (DLT), progression-free survival (PFS), and maximum tolerated dose (MTD).

EXPERT OPINION

Current studies focusing on epigenetic mechanisms of RR strongly support the use of targeting epigenetic modifiers as adjuvants to standard cancer therapies. To further the success of such treatments and their clinical benefit , both preclinical and clinical studies are needed to broaden the scope of known radioresistant mechanisms.

miR-aculous new avenues for cancer immunotherapy

The rising toll of cancer globally necessitates ingenuity in early detection and therapy. In the last decade, the utilization of immune signatures and immune-based therapies has made significant progress in the clinic; however, clinical standards leave many current and future patients without options. Non-coding RNAs, specifically microRNAs, have been explored in pre-clinical contexts with tremendous success. MicroRNAs play indispensable roles in programming the interactions between immune and cancer cells, many of which are current or potential immunotherapy targets. MicroRNAs mechanistically control a network of target genes that can alter immune and cancer cell biology. These insights provide us with opportunities and tools that may complement and improve immunotherapies. In this review, we discuss immune and cancer cell-derived miRNAs that regulate cancer immunity and examine miRNAs as an integral part of cancer diagnosis, classification, and therapy.

Loss of miR-24-3p promotes epithelial cell apoptosis and impairs the recovery from intestinal inflammation

While apoptosis plays a significant role in intestinal homeostasis, it can also be pathogenic if overactive during recovery from inflammation. We recently reported that microRNA-24-3p (miR-24-3p) is elevated in the colonic epithelium of ulcerative colitis patients during active inflammation, and that it reduced apoptosis in vitro. However, its function during intestinal restitution following inflammation had not been examined. In this study, we tested the influence of miR-24-3p on mucosal repair by studying recovery from colitis in both novel miR-24-3p knockout and miR-24-3p-inhibited mice. We observed that knockout mice and mice treated with a miR-24-3p inhibitor had significantly worsened recovery based on weight loss, colon length, and double-blinded histological scoring. In vivo and in vitro analysis of miR-24-3p inhibition in colonic epithelial cells revealed that inhibition promotes apoptosis and increases levels of the pro-apoptotic protein BIM. Further experiments determined that silencing of BIM reversed the pro-apoptotic effects of miR-24-3p inhibition. Taken together, these data suggest that miR-24-3p restrains intestinal epithelial cell apoptosis by targeting BIM, and its loss of function is detrimental to epithelial restitution following intestinal inflammation.

miR-24 and its target gene Prdx6 regulate viability and senescence of myogenic progenitors during aging

Satellite cell-dependent skeletal muscle regeneration declines during aging. Disruptions within the satellite cells and their niche, together with alterations in the myofibrillar environment, contribute to age-related dysfunction and defective muscle regeneration. In this study, we demonstrated an age-related decline in satellite cell viability and myogenic potential and an increase in ROS and cellular senescence. We detected a transient upregulation of miR-24 in regenerating muscle from adult mice and downregulation of miR-24 during muscle regeneration in old mice. FACS-sorted satellite cells were characterized by decreased levels of miR-24 and a concomitant increase in expression of its target: Prdx6. Using GFP reporter constructs, we demonstrated that miR-24 directly binds to its predicted site within Prdx6 mRNA. Subtle changes in Prdx6 levels following changes in miR-24 expression indicate miR-24 plays a role in fine-tuning Prdx6 expression. Changes in miR-24 and Prdx6 levels were associated with altered mitochondrial ROS generation, increase in the DNA damage marker: phosphorylated-H2Ax and changes in viability, senescence, and myogenic potential of myogenic progenitors from mice and humans. The effects of miR-24 were more pronounced in myogenic progenitors from old mice, suggesting a context-dependent role of miR-24 in these cells, with miR-24 downregulation likely a part of a compensatory response to declining satellite cell function during aging. We propose that downregulation of miR-24 and subsequent upregulation of Prdx6 in muscle of old mice following injury are an adaptive response to aging, to maintain satellite cell viability and myogenic potential through regulation of mitochondrial ROS and DNA damage pathways.

Home and Away: The Role of Non-Coding RNA in Intracellular and Intercellular DNA Damage Response

Non-coding RNA (ncRNA) has recently emerged as a vital component of the DNA damage response (DDR), which was previously believed to be solely regulated by proteins. Many species of ncRNA can directly or indirectly influence DDR and enhance DNA repair, particularly in response to double-strand DNA breaks, which may hold therapeutic potential in the context of cancer. These include long non-coding RNA (lncRNA), microRNA, damage-induced lncRNA, DNA damage response small RNA, and DNA:RNA hybrid structures, which can be categorised as cis or trans based on the location of their synthesis relative to DNA damage sites. Mechanisms of RNA-dependent DDR include the recruitment or scaffolding of repair factors at DNA break sites, the regulation of repair factor expression, and the stabilisation of repair intermediates. DDR can also be communicated intercellularly via exosomes, leading to bystander responses in healthy neighbour cells to generate a population-wide response to damage. Many microRNA species have been directly implicated in the propagation of bystander DNA damage, autophagy, and radioresistance, which may prove significant for enhancing cancer treatment via radiotherapy. Here, we review recent developments centred around ncRNA and their contributions to intracellular and intercellular DDR mechanisms.

Proteins from the DNA Damage Response: Regulation, Dysfunction, and Anticancer Strategies

Cells respond to genotoxic stress through a series of complex protein pathways called DNA damage response (DDR). These monitoring mechanisms ensure the maintenance and the transfer of a correct genome to daughter cells through a selection of DNA repair, cell cycle regulation, and programmed cell death processes. Canonical or non-canonical DDRs are highly organized and controlled to play crucial roles in genome stability and diversity. When altered or mutated, the proteins in these complex networks lead to many diseases that share common features, and to tumor formation. In recent years, technological advances have made it possible to benefit from the principles and mechanisms of DDR to target and eliminate cancer cells. These new types of treatments are adapted to the different types of tumor sensitivity and could benefit from a combination of therapies to ensure maximal efficiency.

Radio-Susceptibility of Nasopharyngeal Carcinoma: Focus on Epstein- Barr Virus, MicroRNAs, Long Non-Coding RNAs and Circular RNAs

Nasopharyngeal carcinoma (NPC) is a type of head and neck cancer. As a neoplastic disorder, NPC is a highly malignant squamous cell carcinoma that is derived from the nasopharyngeal epithelium. NPC is radiosensitive; radiotherapy or radiotherapy combining with chemotherapy are the main treatment strategies. However, both modalities are usually accompanied by complications and acquired resistance to radiotherapy is a significant impediment to effective NPC therapy. Therefore, there is an urgent need to discover effective radio-sensitization and radio-resistance biomarkers for NPC. Recent studies have shown that Epstein-Barr virus (EBV)-encoded products, microRNAs (miRNAs), long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs), which share several common signaling pathways, can function in radio-related NPC cells or tissues. Understanding these interconnected regulatory networks will reveal the details of NPC radiation sensitivity and resistance. In this review, we discuss and summarize the specific molecular mechanisms of NPC radio-sensitization and radio-resistance, focusing on EBV-encoded products, miRNAs, lncRNAs and circRNAs. This will provide a foundation for the discovery of more accurate, effective and specific markers related to NPC radiotherapy. EBVencoded products, miRNAs, lncRNAs and circRNAs have emerged as crucial molecules mediating the radio-susceptibility of NPC. This understanding will improve the clinical application of markers and inform the development of novel therapeutics for NPC.

Enhancing the sensitivity of ovarian cancer cells to olaparib via microRNA-20b-mediated cyclin D1 targeting

We previously reported that cyclin D1 silencing interferes with RAD51 accumulation and increases the sensitivity of BRCA1 wild-type ovarian cancer cells to olaparib. However, the mechanisms associated with cyclin D1 overexpression in ovarian cancer are not fully understood. TargetScan predicted the potential binding sites for microRNA-20b (miR-20b) and the 3'-untranslated region of cyclin D1 mRNA; thus, we used luciferase reporter assay to verify those binding sites. The Kaplan-Meier method and log-rank test were used to examine the relationship between miR-20b and progression-free survival of ovarian cancer patients in The Cancer Genome Atlas (n = 367) dataset. In vitro experiments were performed to evaluate the effects of miR-20b on cyclin D1 expression, cell cycle and response to olaparib. A peritoneal cavity metastasis model of ovarian cancer was established to determine the effect of miR-20b on the sensitivity of olaparib. Immunohistochemistry was performed to evaluate molecular mechanisms. In this work, we demonstrated that miR-20b down-regulates cyclin D1, increases the sensitivity of ovarian cancer cells to olaparib, reduces the expression of RAD51, and induces cell cycle arrest in G0/G1 phase. Ovarian cancer patients with higher expression of miR-20b had significantly longer progression-free survival. These results indicate that miR-20b may be a potential clinical indicator for the sensitivity of ovarian cancer to olaparib and the survival of ovarian cancer patients. Our findings suggest that miR-20b may have therapeutic value in combination with olaparib treatment for ovarian cancer.

Current Implications of microRNAs in Genome Stability and Stress Responses of Ovarian Cancer

Genomic alterations and aberrant DNA damage signaling are hallmarks of ovarian cancer (OC), the leading cause of mortality among gynecological cancers worldwide. Owing to the lack of specific symptoms and late-stage diagnosis, survival chances of patients are significantly reduced. Poly (ADP-ribose) polymerase (PARP) inhibitors and replication stress response inhibitors present attractive therapeutic strategies for OC. Recent research has focused on ovarian cancer-associated microRNAs (miRNAs) that play significant regulatory roles in various cellular processes. While miRNAs have been shown to participate in regulation of tumorigenesis and drug responses through modulating the DNA damage response (DDR), little is known about their potential influence on sensitivity to chemotherapy. The main objective of this review is to summarize recent findings on the utility of miRNAs as cancer biomarkers, in particular, ovarian cancer, and their regulation of DDR or modified replication stress response proteins. We further discuss the suppressive and promotional effects of various miRNAs on ovarian cancer and their participation in cell cycle disturbance, response to DNA damage, and therapeutic functions in multiple cancer types, with particular focus on ovarian cancer. Improved understanding of the mechanisms by which miRNAs regulate drug resistance should facilitate the development of effective combination therapies for ovarian cancer.

The Role of RNA in DNA Breaks, Repair and Chromosomal Rearrangements

Incorrect reparation of DNA double-strand breaks (DSB) leading to chromosomal rearrangements is one of oncogenesis's primary causes. Recently published data elucidate the key role of various types of RNA in DSB formation, recognition and repair. With growing interest in RNA biology, increasing RNAs are classified as crucial at the different stages of the main pathways of DSB repair in eukaryotic cells: nonhomologous end joining (NHEJ) and homology-directed repair (HDR). Gene mutations or variation in expression levels of such RNAs can lead to local DNA repair defects, increasing the chromosome aberration frequency. Moreover, it was demonstrated that some RNAs could stimulate long-range chromosomal rearrangements. In this review, we discuss recent evidence demonstrating the role of various RNAs in DSB formation and repair. We also consider how RNA may mediate certain chromosomal rearrangements in a sequence-specific manner.

Mitigation of X-ray induced DNA damages and expression of DNA-repair genes by antioxidative Potentilla fulgens root extract and its ethyl-acetate fraction in mammalian cells

Potentilla fulgens is a medicinal plant in North-East India whose root is reported to have anti-diabetic, anticarcinogenic and antioxidant properties. The potential of hydro-alcoholic extract of P. fulgens root (PRE) for providing protection to mammalian cells exposed to ionising radiation was investigated in this study. The methanolic extract of PRE shows an enhanced radical scavenging ability in a concentration dependent manner. PRE-pre-treatment to stimulated human blood lymphocytes (HBLs) reduced the frequency of deletion and exchange aberrations induced by X-irradiation. Similar protection of chromosome aberrations was also observed in mouse bone marrow cells (BMCs) where mice were given PRE extract (1 mg extract/day/mice) ad libitum in the drinking water for 45 days before whole-body X-irradiation. Of the various extracts prepared by partitioning of the methanol extract, the ethyl-acetate (EA) fraction was found to possess better antioxidant, radical scavenging and DNA-damage reduction activities. PRE-pre-treatment also reduced the radiation-induced cell-cycle delay effectively in HBL. In HEK-293 cells, PRE reduced radiation-induced G2-block in cell kinetics. Interestingly, PRE-treatment alone increased the concentration of endogenous glutathione (GSH) in mouse BMC and in stimulated HBL along with the elevated expression of γ-glutamyl-cysteine synthetase heavy/catalytic subunit, a key determinant of GSH synthesis. Studies on expression of two DNA-repair genes revealed that there was a marked increase in the expression of GADD45 and H2AX genes after X-irradiation in stimulated HBL, and such expression was reduced significantly if PRE-treatment was given prior to radiation. The present findings show the ability of PRE to reduce radiation-induced DNA damages probably by free radical scavenging whereas modulation of expression of DNA-repair genes' and endogenous GSH-increment emerge as effective strategies. The present study is the first report on the selected medicinal plant species that suggests it to be a potential natural radioprotector when used as root extract or its EA fraction for mitigating radiation toxicity.

Analyzing the impact of 900 MHz EMF short-term exposure to the expression of 667 miRNAs in human peripheral blood cells

More than ever before, people around the world are frequently exposed to different sections of the electromagnetic spectrum, mainly emitted from wireless modern communication technologies. Especially, the level of knowledge on non-thermal biological EMF effects remains controversial. New technologies allow for a more detailed detection of non-coding RNAs which affect the post-transcriptional control. Such method shall be applied in this work to investigate the response of human blood cells to electromagnetic irradiation. In this ex vivo in vitro study, we exposed peripheral blood cells from 5 male donors to a continuous wave of 900 MHz EMF for 0, 30, 60 and 90 min. Significant micro RNA (miRNA) expression changes (p ≤ 0.05) above or below the SHAM exposed samples were evaluated using a quantitative real time PCR platform for simultaneous detection of 667 miRNAs called low density array. Only significant miRNA expression changes which were detectable in at least 60% of the samples per exposure group were analyzed. The results were compared with data from room temperature + 2 °C (RT + 2 °C) samples (here referred to as hyperthermia) to exclude miRNA expression altered by hyperthermia. The validation study by using the same donors and study design was performed after an interval of 2 years. When analyzing a total of 667 miRNAs during the screening study, 2 promising candidate miRNAs were identified, which were down regulated almost twice and showed a complete separation from the unexposed control group (miR-194 at 30 min and miR-939 at 60 min). The p-values even survived the Bonferroni correction for multiple comparisons (p = 0.0007 and p = 0.004, respectively). None of these miRNAs were expressed at a second time point after EMF exposure. Following an alternative analysis approach, we examined for miRNAs revealing an expected significant association of differential miRNA expression with the dose-time EMF exposure product, separately for each donor. Donors 2 and 3 revealed 11 and 10 miRNA species being significantly associated with EMF exposure which differed significantly from the other donors showing a minor number of differentially expressed miRNAs and could identify donors 2 and 3 as particularly EMF-responsive. The measurements were repeated after 2 years. The number of expressed/non-expressed miRNAs was almost similar (97.4%), but neither the number nor the previously differentially expressed miRNAs could be reproduced. Our data neither support evidence of early changes at miRNA expression level in human whole blood cells after 900 MHz EMF exposure nor the identification of EMF-responsive individuals.

Role of epigenetic mechanisms in propagating off-targeted effects following radiation based therapies - A review

Despite being an important diagnostic and treatment modality, ionizing radiation (IR) is also known to cause genotoxicity and multiple side effects leading to secondary carcinogenesis. While modern cancer radiation therapy has improved patient recovery and enhanced survival rates, the risk of radiation-related adverse effects has become a growing challenge. It is now well-accepted that IR-induced side effects are not exclusively restricted to exposed cells but also spread to distant 'bystander' cells and even to the unexposed progeny of the irradiated cells. These 'off-targeted' effects involve a plethora of molecular events depending on the type of radiation and tumor tissue background. While the mechanisms by which off-targeted effects arise remain obscure, emerging evidence based on the non-mendelian inheritance of various manifestations of them as well as their persistence for longer periods supports a contribution of epigenetic factors. This review focuses on the major epigenetic phenomena including DNA methylation, histone modifications, and small RNA mediated silencing and their versatile role in the manifestation of IR induced off-targeted effects. As short- and long-range communication vehicles respectively, the role of gap junctions and exosomes in spreading these epigenetic-alteration driven off-targeted effects is also discussed. Furthermore, this review emphasizes the possible therapeutic potentials of these epigenetic mechanisms and how beneficial outcomes could potentially be achieved by targeting various signaling molecules involved in these mechanisms.

MicroRNA miR-24-3p reduces DNA damage responses, apoptosis, and susceptibility to chronic obstructive pulmonary disease

The pathogenesis of chronic obstructive pulmonary disease (COPD) involves aberrant responses to cellular stress caused by chronic cigarette smoke (CS) exposure. However, not all smokers develop COPD and the critical mechanisms that regulate cellular stress responses to increase COPD susceptibility are not understood. Because microRNAs are well-known regulators of cellular stress responses, we evaluated microRNA expression arrays performed on distal parenchymal lung tissue samples from 172 subjects with and without COPD. We identified miR-24-3p as the microRNA that best correlated with radiographic emphysema and validated this finding in multiple cohorts. In a CS exposure mouse model, inhibition of miR-24-3p increased susceptibility to apoptosis, including alveolar type II epithelial cell apoptosis, and emphysema severity. In lung epithelial cells, miR-24-3p suppressed apoptosis through the BH3-only protein BIM and suppressed homology-directed DNA repair and the DNA repair protein BRCA1. Finally, we found BIM and BRCA1 were increased in COPD lung tissue, and BIM and BRCA1 expression inversely correlated with miR-24-3p. We concluded that miR-24-3p, a regulator of the cellular response to DNA damage, is decreased in COPD, and decreased miR-24-3p increases susceptibility to emphysema through increased BIM and apoptosis.

Non-coding RNAs as Regulators of Cellular Senescence in Idiopathic Pulmonary Fibrosis and Chronic Obstructive Pulmonary Disease

Cellular senescence is a cell fate implicated in the pathogenesis of idiopathic pulmonary fibrosis (IPF) and chronic obstructive pulmonary disease (COPD). Cellular senescence occurs in response to cellular stressors such as oxidative stress, DNA damage, telomere shortening, and mitochondrial dysfunction. Whether these stresses induce cellular senescence or an alternative cell fate depends on the type and magnitude of cellular stress, but also on intrinsic factors regulating the cellular stress response. Non-coding RNAs, including both microRNAs and long non-coding RNAs, are key regulators of cellular stress responses and susceptibility to cellular senescence. In this review, we will discuss cellular mechanisms that contribute to senescence in IPF and COPD and highlight recent advances in our understanding of how these processes are influenced by non-coding RNAs. We will also discuss the potential therapeutic role for targeting non-coding RNAs to treat these chronic lung diseases.

The Emerging Role of miRNAs for the Radiation Treatment of Pancreatic Cancer

Simple Summary

Pancreatic cancer is an aggressive disease with a high mortality rate. Radiotherapy is one treatment option within a multimodal therapy approach for patients with locally advanced, non-resectable pancreatic tumors. However, radiotherapy is only effective in about one-third of the patients. Therefore, biomarkers that can predict the response to radiotherapy are of utmost importance. Recently, microRNAs, small non-coding RNAs regulating gene expression, have come into focus as there is growing evidence that microRNAs could serve as diagnostic, predictive and prognostic biomarkers in various cancer entities, including pancreatic cancer. Moreover, their high stability in body fluids such as serum and plasma render them attractive candidates for non-invasive biomarkers. This article describes the role of microRNAs as suitable blood biomarkers and outlines an overview of radiation-induced microRNAs changes and the association with radioresistance in pancreatic cancer.

Abstract

Today, pancreatic cancer is the seventh leading cause of cancer-related deaths worldwide with a five-year overall survival rate of less than 7%. Only 15–20% of patients are eligible for curative intent surgery at the time of diagnosis. Therefore, neoadjuvant treatment regimens have been introduced in order to downsize the tumor by chemotherapy and radiotherapy. To further increase the efficacy of radiotherapy, novel molecular biomarkers are urgently needed to define the subgroup of pancreatic cancer patients who would benefit most from radiotherapy. MicroRNAs (miRNAs) could have the potential to serve as novel predictive and prognostic biomarkers in patients with pancreatic cancer. In the present article, the role of miRNAs as blood biomarkers, which are associated with either radioresistance or radiation-induced changes of miRNAs in pancreatic cancer, is discussed. Furthermore, the manuscript provides own data of miRNAs identified in a pancreatic cancer mouse model as well as radiation-induced miRNA changes in the plasma of tumor-bearing mice.

Glucocorticoid receptors and their upstream epigenetic regulators in adults with steroid-resistant nephrotic syndrome

Steroid-resistant nephrotic syndrome (SRNS) is a clinical challenge with variable clinical outcomes. In patients with SRNS, unsuccessful anti-inflammatory and anti-proteinuric effects of steroids lead to end-stage renal disease (ESRD). Our objective was to define the expression pattern of the glucocorticoid receptors (GR) α and β and their epigenetic regulators (miR-24, miR-30a, and miR-370) in a group of adults with SRNS. In this regard, sixty primary NS patients with focal segmental glomerulosclerosis (FSGS, N = 30) and membranous glomerulonephritis (MGN, N = 30) and also healthy volunteers (N = 24) were enrolled. Real-time PCR was performed to evaluate the expression levels of the aforementioned genes in peripheral blood mononuclear cell (PBMC) samples. Furthermore, an in-silico analysis was performed to understand the signaling pathways and biological procedures that may be targeted by these microRNAs in NS. The decreased and increased levels of GRα and GRβ were not significant, respectively. Statistically significant reduced miR-24 levels were observed between control/MGN (p = .022) and MGN/FSGS (p = .032) groups. Additionally, a decrease was detected in miR-30a between MGN and FSGS (p = .049) groups. There was a significant increase in miR-370 expression level between control and NS groups (p = .029), as well as control/MGN (p = .008), and MGN/FSGS (p = .046). Bioinformatics analysis predicted the possible targets of the studied genes including genes involved in TGF-β, Notch1, and p53 signaling pathways, regulation of gene expression, intracellular signal transduction, negative regulation of response to the stimulus, cell-cell signaling, and cell activation in the pathogenesis of SRNS. Taken all together, dysregulated levels of GRα, GRβ were not attributed to SRNS in our patients. It seems that pharmacokinetics and the genetic variations in podocyte-related genes may be associated with the steroid-resistance in our adult patients with NS rather than GR expression.

Jack of all trades? The versatility of RNA in DNA double-strand break repair

The mechanisms by which RNA acts in the DNA damage response (DDR), specifically in the repair of DNA double-strand breaks (DSBs), are emerging as multifaceted and complex. Different RNA species, including but not limited to; microRNA (miRNA), long non-coding RNA (lncRNA), RNA:DNA hybrid structures, the recently identified damage-induced lncRNA (dilncRNA), damage-responsive transcripts (DARTs), and DNA damage-dependent small RNAs (DDRNAs), have been shown to play integral roles in the DSB response. The diverse properties of these RNAs, such as sequence, structure, and binding partners, enable them to fulfil a variety of functions in different cellular contexts. Additionally, RNA can be modified post-transcriptionally, a process which is regulated in response to cellular stressors such as DNA damage. Many of these mechanisms are not yet understood and the literature contradictory, reflecting the complexity and expansive nature of the roles of RNA in the DDR. However, it is clear that RNA is pivotal in ensuring the maintenance of genome integrity. In this review, we will discuss and summarise recent evidence which highlights the roles of these various RNAs in preserving genomic integrity, with a particular focus on the emerging role of RNA in the DSB repair response.

MiR-24 Promotes Cell Growth in Human Glioma by CDX1/PI3K/Akt Signaling Pathway

MicroRNA-24 (miR-24) has been identified to be related to the development of glioma. However, the exact molecular mechanism of miR-24 in glioma progression remains vague. The aim of the present study was to investigate the role of miR-24 in sepsis and to reveal the associated mechanisms. Quantitative real-time polymerase chain reaction was used to compare the levels of miR-24 in glioma and normal tissue. The miR-24 inhibitor or miR-24 mimic was transfected into glioma cells, and then the effects of miR-24 on cell proliferation and apoptosis were detected using CCK-8 (Cell Counting Kit-8) assay and flow cytometry, respectively. Western blot was used to examine the levels of CDX1 (caudal-type homeobox 1), PI3K, p-PI3K, Akt, p-Akt, Cyclin D1, p27, proliferating cell nuclear antigen, Bcl-2, Bax, and Cleaved-casp3. Luciferase assay was used to identify the target gene of miR-24. An animal model was established in mice to detect the role of miR-24 in vivo. These results suggested that miR-24 was elevated in glioma, and miR-24 could promote glioma progression by facilitating cell proliferation and inducing cell apoptosis through CDX1/PI3K/Akt signaling pathway, indicating a novel pathway underlying progression in glioma cells and providing a potential target for glioma treatment.

H2A Histone Family Member X (H2AX) Is Upregulated in Ovarian Cancer and Demonstrates Utility as a Prognostic Biomarker in Terms of Overall Survival

Background: H2AX can be of prognostic value in breast cancer, since in advanced stage patients with high levels, there was an association with worse overall survival (OS). However, the clinical relevance of H2AX in ovarian cancer (OC) remains to be elucidated. Methods: OC H2AX expression studied using the TCGA/GTEX datasets. Subsequently, patients were classified as either high or low in terms of H2AX expression to compare OS and perform gene set enrichment. qRT-PCR validated in-silico H2AX findings followed by immunohistochemistry on a tissue microarray. The association between single nucleotide polymorphisms in the area of H2AX; prevalence and five-year OC survival was tested in samples from the UK Biobank. Results: H2AX was significantly overexpressed in OCs compared to normal tissues, with higher expression associated with better OS (p = 0.010). Gene Set Enrichment Analysis demonstrated gene sets involved in G2/M checkpoint, DNA repair mTORC1 signalling were enriched in the H2AX highly expressing OCs. Polymorphisms in the area around the gene were associated with both OC prevalence (rs72997349-C, p = 0.005) and worse OS (rs10790282-G, p = 0.011). Finally, we demonstrated that H2AX gene expression correlated with γ-H2AX staining in vitro. Conclusions: Our findings suggest that H2AX can be a novel prognostic biomarker for OC.

Regulation of DNA Damage Response and Homologous Recombination Repair by microRNA in Human Cells Exposed to Ionizing Radiation

Ionizing radiation may be of both artificial and natural origin and causes cellular damage in living organisms. Radioactive isotopes have been used significantly in cancer therapy for many years. The formation of DNA double-strand breaks (DSBs) is the most dangerous effect of ionizing radiation on the cellular level. After irradiation, cells activate a DNA damage response, the molecular path that determines the fate of the cell. As an important element of this, homologous recombination repair is a crucial pathway for the error-free repair of DNA lesions. All components of DNA damage response are regulated by specific microRNAs. MicroRNAs are single-stranded short noncoding RNAs of 20–25 nt in length. They are directly involved in the regulation of gene expression by repressing translation or by cleaving target mRNA. In the present review, we analyze the biological mechanisms by which miRNAs regulate cell response to ionizing radiation-induced double-stranded breaks with an emphasis on DNA repair by homologous recombination, and its main component, the RAD51 recombinase. On the other hand, we discuss the ability of DNA damage response proteins to launch particular miRNA expression and modulate the course of this process. A full understanding of cell response processes to radiation-induced DNA damage will allow us to develop new and more effective methods of ionizing radiation therapy for cancers, and may help to develop methods for preventing the harmful effects of ionizing radiation on healthy organisms.

Non-Coding RNAs in Cancer Radiosensitivity: MicroRNAs and lncRNAs as Regulators of Radiation-Induced Signaling Pathways

Radiotherapy is a cancer treatment that applies high doses of ionizing radiation to induce cell death, mainly by triggering DNA double-strand breaks. The outcome of radiotherapy greatly depends on radiosensitivity of cancer cells, which is determined by multiple proteins and cellular processes. In this review, we summarize current knowledge on the role of microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), in determining the response to radiation. Non-coding RNAs modulate ionizing radiation response by targeting key signaling pathways, including DNA damage repair, apoptosis, glycolysis, cell cycle arrest, and autophagy. Additionally, we indicate miRNAs and lncRNAs that upon overexpression or inhibition alter cellular radiosensitivity. Current data indicate the potential of using specific non-coding RNAs as modulators of cellular radiosensitivity to improve outcome of radiotherapy.

microRNAs targeting cellular cholesterol: implications for combating anticancer drug resistance

Over sixty percent of all mammalian protein-coding genes are estimated to be regulated by microRNAs (miRNAs), and unsurprisingly miRNA dysregulation has been linked with cancer. Aberrant miRNA expression in cancer cells has been linked with tumourigenesis and drug resistance. In the past decade, increasing number of studies have demonstrated that cholesterol accumulation fuels tumour growth and contributes to drug resistance, therefore, miRNAs controlling cholesterol metabolism and homeostasis are obvious hypothetical targets for investigating their role in cholesterol-mediated drug resistance in cancer. In this review, we have collated published evidences to consolidate this hypothesis and have scrutinized it by utilizing computational tools to explore the role of miRNAs in cholesterol-mediated drug resistance in breast cancer cells. We found that hsa-miR-128 and hsa-miR-223 regulate genes mediating lipid signalling and cholesterol metabolism, cancer drug resistance and breast cancer genes. The analysis demonstrates that targeting these miRNAs in cancer cells presents an opportunity for developing new strategies to combat anticancer drug resistance.

Connections between 3' end processing and DNA damage response: Ten years later

Ten years ago we reviewed how the cellular DNA damage response (DDR) is controlled by changes in the functional and structural properties of nuclear proteins, resulting in a timely coordinated control of gene expression that allows DNA repair. Expression of genes that play a role in DDR is regulated not only at transcriptional level during mRNA biosynthesis but also by changing steady-state levels due to turnover of the transcripts. The 3' end processing machinery, which is important in the regulation of mRNA stability, is involved in these gene-specific responses to DNA damage. Here, we review the latest mechanistic connections described between 3' end processing and DDR, with a special emphasis on alternative polyadenylation, microRNA and RNA binding proteins-mediated deadenylation, and discuss the implications of deregulation of these steps in DDR and human disease. This article is categorized under: RNA Processing > 3' End Processing RNA-Based Catalysis > Miscellaneous RNA-Catalyzed Reactions RNA in Disease and Development > RNA in Disease.

Role of the DNA repair genes H2AX and HMGB1 in human fat distribution and lipid profiles

INTRODUCTION

Regional fat distribution strongly relates to metabolic comorbidities. We identified the DNA repair genes H2AX and HMGB1 to be differentially expressed between human subcutaneous (SAT) and omental visceral adipose tissue (OVAT) depots. As increased DNA damage is linked to metabolic disease, we here sought to analyze whether depot-specific H2AX and HMGB1 expression is related to anthropometric and metabolic profiles of obesity. We further tested for different H2AX mRNA regulatory mechanisms by analyzing promoter DNA methylation and genotyped rs7350 in the H2AX locus.

RESEARCH DESIGN AND METHODS

Gene expression (OVAT n=48; SAT n=55) and DNA promoter methylation data (OVAT and SAT n=77) were extracted from an existing dataset as described elsewhere. Genotype data for the 3'untranslated region (3'UTR) H2AX variant rs7350 were generated by using the TaqMan genotyping system in 243 subjects of the same cohort. Statistical analyses were done using SPSS statistics software 24 and GraphPad Prism 6.

RESULTS

We identified H2AX being higher (p=0.002) and HMGB1 being less expressed (p=0.0001) in OVAT compared with SAT. Further, we observed positive interdepot correlations of OVAT and SAT for both HMGB1 (p=1×10^-6) and H2AX mRNA levels (p=0.024). Depot-specific associations were observed for both genes' methylation levels with either high density lipoprotein cholesterol, low density lipoprotein cholesterol, triglycerides and/or with OVAT/SAT-ratio (all p<0.05). A significantly lower level of total cholesterol in minor A-Allele carriers of rs7350 compared with AG and GG carriers (p=0.001) was observed. Additionally, subjects carrying the A-allele showed lower SAT HMGB1 expression level (p=0.030).

CONCLUSION

Our results suggest a fat depot-specific regulation of H2AX and HMGB1 potentially mediated by both DNA methylation and genetic variation. Rs7350, DNA methylation and/or mRNA levels of H2AX and HMGB1 are related to lipid parameters. Further studies are warranted to evaluate the functional role of the DNA repair genes H2AX and HMGB1 in obesity and fat distribution.

MiR-502 is the first reported miRNA simultaneously targeting two components of the classical non-homologous end joining (C-NHEJ) in pancreatic cell lines

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers. Acquired inherited and/or somatic mutations drive its development. In order to prevent the formation of these mutations, precise and immediate repair of any DNA damage is indispensable. Non-homologous end-joining (NHEJ) is the key mechanism of DNA double-strand break repair. Here, we report that miR-502 targets two components in pancreatic cell lines, Ku70 and XLF of the C-NHEJ. Interestingly, we also observed an attenuated cell cycle response to gamma ionizing radiation (γ-IR) via diminished phosphorylation of checkpoint kinase 1 (Chk1) on serine 345 in these cell lines. Altogether, pancreatic cells showed increased susceptibility to γ-IR via direct inhibition of DNA double-strand break repair and attenuation of the cell cycle response.

The role of endothelial miRNAs in myocardial biology and disease

The myocardium is a highly structured pluricellular tissue which is governed by an intricate network of intercellular communication. Endothelial cells are the most abundant cell type in the myocardium and exert crucial roles in both healthy myocardium and during myocardial disease. In the last decade, microRNAs have emerged as new actors in the regulation of cellular function in almost every cell type. Here, we review recent evidence on the regulatory function of different microRNAs expressed in endothelial cells, also called endothelial microRNAs, in healthy and diseased myocardium. Endothelial microRNA emerged as modulators of angiogenesis in the myocardium, they are implicated in the paracrine role of endothelial cells in regulating cardiac contractility and homeostasis, and interfere in the crosstalk between endothelial cells and cardiomyocytes.

Let-7e Suppresses DNA Damage Repair and Sensitizes Ovarian Cancer to Cisplatin through Targeting PARP1

Increased DNA damage repair is one of the mechanisms implicated in cisplatin resistance. Our previous study indicated that the deregulation of let-7e promoted cisplatin resistance and that let-7e could suppress DNA double-strand break repair in ovarian cancer. In this study, we further characterized the role of let-7e in DNA damage repair and cisplatin resistance in ovarian cancer, and investigated the underlying mechanisms. The alkaline and neutral comet assay indicated that let-7e impeded both DNA single- and double-strand break repairs through downregulating its target gene PARP1. In vitro and in vivo experiments provided evidence that the let-7e-PARP1-DNA repair axis was involved in the modulation of cisplatin sensitivity in ovarian cancer. Contrary to let-7e, PARP1 was overexpressed in cisplatin-resistant ovarian cancer tissues, and patients with high PARP1 expression exhibited poor progression-free survival (PFS) and overall survival (OS). Multivariate logistic and Cox regression analyses showed that let-7e and FIGO stage were independent prognostic factors for PFS and OS, whereas let-7e and PARP1 were able to independently predict chemotherapy response. Taken together, our results indicated that low expression of let-7e promoted DNA single- and double-strand break repairs and subsequently contributed to cisplatin resistance by relieving the suppression on PARP1 in ovarian cancer. IMPLICATIONS: Targeting the let-7e-PARP1-DNA repair axis might be an effective strategy for the treatment of chemoresistant ovarian cancer.

miR-222 enhances radiosensitivity of cancer cells by inhibiting the expression of CD47

Radiotherapy is one of the most common and effective treatments for localized cancer. However, radiotherapy kills tumor cells while causing damage to surrounding normal cells. Enhancing the radiation sensitivity of tumor cells and reducing the radiation damage to normal cells is a difficult problem. Here, we find that the expression of a human microRNA (miRNA), hsa-miR-222, is upregulated in response to ionizing radiation. TargetScan analysis shows that the 3' UTR of CD47 is potentially targeted by miR-222. This prediction was validated by luciferase reporter and mutation assays. It was demonstrated that miR-222 negatively regulates CD47 expression at mRNA and protein levels, and overexpression of the miR-222 enhances cancer cell radiosensitivity by the CD47-pERK pathway in cancer cells. Our findings enrich the complex relationship between miRNA and CD47 in irradiation stress and shed light on the potential of miRNAs both for direct cancer therapeutics and as tools to sensitize tumor cells to radiotherapy.

The miR-205-5p/BRCA1/RAD17 Axis Promotes Genomic Instability in Head and Neck Squamous Cell Carcinomas

Defective DNA damage response (DDR) is frequently associated with tumorigenesis. Abrogation of DDR leads to genomic instability, which is one of the most common characteristics of human cancers. TP53 mutations with gain-of-function activity are associated with tumors under high replicative stress, high genomic instability, and reduced patient survival. The BRCA1 and RAD17 genes encode two pivotal DNA repair proteins required for proper cell-cycle regulation and maintenance of genomic stability. We initially evaluated whether miR-205-5p, a microRNA (miRNA) highly expressed in head and neck squamous cell carcinoma (HNSCC), targeted BRCA1 and RAD17 expression. We found that, in vitro and in vivo, BRCA1 and RAD17 are targets of miR-205-5p in HNSCC, leading to inefficient DNA repair and increased chromosomal instability. Conversely, miR-205-5p downregulation increased BRCA1 and RAD17 messenger RNA (mRNA) levels, leading to a reduction in in vivo tumor growth. Interestingly, miR-205-5p expression was significantly anti-correlated with BRCA1 and RAD17 targets. Furthermore, we documented that miR-205-5p expression was higher in tumoral and peritumoral HNSCC tissues than non-tumoral tissues in patients exhibiting reduced local recurrence-free survival. Collectively, these findings unveil miR-205-5p's notable role in determining genomic instability in HNSCC through its selective targeting of BRCA1 and RAD17 gene expression. High miR-205-5p levels in the peritumoral tissues might be relevant for the early detection of minimal residual disease and pre-cancer molecular alterations involved in tumor development.

Upregulation of the APE1 and H2AX genes and miRNAs involved in DNA damage response and repair in gastric cancer

Gastric cancer remains one of the leading causes of cancer-related death worldwide, and most of the cases are associated with Helicobacter pylori infection. This bacterium promotes the production of reactive oxygen species (ROS), which cause DNA damage in gastric epithelial cells. In this study, we evaluated the expression of important genes involved in the recognition of DNA damage (ATM, ATR, and H2AX) and ROS-induced damage repair (APE1) and the expression of some miRNAs (miR-15a, miR-21, miR-24, miR-421 and miR-605) that target genes involved in the DNA damage response (DDR) in 31 fresh tissues of gastric cancer. Cytoscape v3.1.1 was used to construct the postulated miRNA:mRNA interaction network. Analysis performed by real-time quantitative PCR exhibited significantly increased levels of the APE1 (RQ = 2.55, p < 0.0001) and H2AX (RQ = 2.88, p = 0.0002) genes beyond the miR-421 and miR-605 in the gastric cancer samples. In addition, significantly elevated levels of miR-21, miR-24 and miR-421 were observed in diffuse-type gastric cancer. Correlation analysis reinforced some of the gene:gene (ATM/ATR/H2AX) and miRNA:mRNA relationships obtained also with the interaction network. Thus, our findings show that tumor cells from gastric cancer presents deregulation of genes and miRNAs that participate in the recognition and repair of DNA damage, which could confer an advantage to cell survival and proliferation in the tumor microenvironment.

MiR-34s negatively regulate homologous recombination through targeting RAD51

Double-strand breaks (DSBs), the most serious lesions of DNA, often induce chromosomal aberrations and are intimately associated with oncogenesis. A normal DNA damage response (DDR) network contains two major repair pathways: homologous recombination (HR) and non-homologous end-joining (NHEJ). Studies of DSB repair-associated molecules have focused mainly on DNA repair proteins. However, non-coding RNAs also play important roles in the process of DSB repair. Over the past two decades, microRNAs (miRNAs) have been extensively investigated. Our previous work showed that miR-34c-5p overexpression results in suppression of RAD51 and upregulation of γH2AX. In accordance with this, we confirmed that miR-34s family overexpression increased endogenous DSB levels to different extents, an effect that was further confirmed to be associated with the decreased efficiency of HR repair. In addition, miR-34s overexpression also induced G1 arrest, inhibited proliferation and promoted apoptosis. As a central molecule in the process of HR pathway, RAD51 expression was strongly repressed in cells transfected with the miR-34a/b/c-5p mimic. Finally, we demonstrated that miR-34a/b/c-5p directly targets the RAD51 mRNA 3'-UTR or indirectly inhibits RAD51 expression via the p53 signaling pathway. Taken together, our results indicate that miR-34s overexpression depresses the efficiency of HR repair and induces DSBs by downregulating RAD51 expression. Our findings highlight a novel mechanism of HR pathway regulation via the miR-34s/p53/RAD51 axis.

Multiple metals exposure and chromosome damage: Exploring the mediation effects of microRNAs and their potentials in lung carcinogenesis

OBJECTIVE

This study aimed to investigate the associations of multiple metals with chromosome damage, and further explore the mediation roles of microRNAs (miRNAs) and their potentials in lung cancer.

METHODS

We determined the urinary levels of 23 metals, lymphocytic micronucleus (MN) frequency, and ten candidate miRNAs in plasma among 365 healthy workers. Poisson and linear regression models were conducted to analyze the associations of urinary metals with MN frequency and miRNAs, respectively. The mediation effects of miRNAs on the metal-MN frequency associations were assessed by causal mediation analysis. Additionally, the levels of effective metal and miRNAs were measured in 43 pair-wised tumor and normal lung tissues.

RESULTS

The urinary level of titanium was inversely associated with MN frequency after Bonferroni correction [frequency ratio (FR) and 95% confidence interval (95%CI) = 0.88 (0.82, 0.94), p = 5.0 × 10^-4]. A doubling in urinary titanium was associated with 14.72%-38.17% decrease in plasma miRNAs. After multiple comparison, miR-24-3p and miR-28-5p significantly mediated 24.8% (7.7%, 70.0%) and 20.4% (5.7%, 52.0%) of the association between titanium and MN frequency (p_mediation = 0.002 and 0.004, respectively). Besides, a doubling in titanium was associated with a separate 53.4% and 47.2% decreased miR-24-3p and miR-28-5p expression in normal lung tissues. Lower titanium but higher levels of miR-24-3p and miR-28-5p were shown in tumor than normal tissues of lung squamous cell carcinoma patients (all p < 0.05).

CONCLUSIONS

Our study proposed the negative associations of titanium with chromosome damage and lung cancer, and highlighted the mediating roles of miR-24-3p and miR-28-5p. Further investigations are warranted to validate these associations and uncover the underlying mechanisms.

Comparative Transcriptomics Unravels Prodigiosin's Potential Cancer-Specific Activity Between Human Small Airway Epithelial Cells and Lung Adenocarcinoma Cells

Objective: Non-Small Cell Lung Cancer (NSCLC) is extremely lethal upon metastasis and requires safe and effective systemic therapies to improve a patient's prognosis. Prodigiosin (PG) appears to selectively and effectively target cancer but not healthy cells. However, PG's cancer-specific activity has remained elusive until recently. Methods: PG's cancer-specific performance was compared to Docetaxel (DTX), Paclitaxel (PTX), and Doxorubicin (DOX) against human lung adenocarcinoma (A549) and human small airway epithelial cells (HSAEC). Combination of PG with DTX, PTX, or DOX in a 1:1 ED50 ratio was also evaluated. MTT assay was used to determine the post-treatment cell viability. RNA-sequencing was used for comparative transcriptomics analysis between A549 and HSAEC treated with 1.0 μM PG for 24 h. Results: PG reduced A549 cell viability by four-folds greater than HSAEC. In comparison to DTX, PTX and DOX, PG was ~1.7 times more toxic toward A549, and 2.5 times more protective toward HSAEC. Combination of PG in a 1:1 ED50 ratio with DTX, PTX, or DOX failed to exhibit synergistic toxicity toward A549 or protection toward HSAEC. In A549, genes associated in DNA replication were downregulated, while genes directly or indirectly associated in lipid and cholesterol biogenesis were upregulated. In HSAEC, co-upregulation of oncogenic and tumor-suppressive genes was observed. Conclusion: An overactive lipid and cholesterol biogenesis could have caused A549's autophagy, while a balancing-act between genes of oncogenic and tumor-suppressive nature could have conferred HSAEC heightened survival. Overall, PG appears to be a smart chemotherapeutic agent that may be both safe and effective for NSCLC patients.

Downregulation of miR-24-3p promotes osteogenic differentiation of human periodontal ligament stem cells by targeting SMAD family member 5

Osteogenic differentiation is a complicated process that depends on various regulatory factors and signal pathways. In our research, the osteogenic differentiation capacity was analyzed by alizarin red staining, alkaline phosphatase activity, and protein levels of osteogenic differentiation markers including runt-related transcription factor 2, bone morphogenetic protein 2, and osteocalcin (OCN). We observed a notable decrease of miR-24-3p level in osteogenic-differentiated human periodontal ligament stem cells (hPDLSCs) by microarray analysis. In our gain- and loss-of-function experiments, we discovered that miR-24-3p has a suppression effect on hPDLSCs osteogenic differentiation. Moreover, SMAD family member 5 (Smad5), the critical osteogenic differentiation transcription factors, was predicted to be targets of miR-24-3p. In addition, luciferase reporter assay further proved that miR-24-3p directly targeted the 3'-untranslated region of Smad5. Similarly, we found that the overexpression of miR-24-3p significantly decreased the Smad5 messenger RNA level in hPDLSCs, which was detected by real-time quantitative polymerase chain reaction. Then hPDLSCs were transfected with miR-24-3p mimics to inhibit Smad5 expression; meanwhile, Smad5 RNA interference could significantly reverse the osteogenic differentiation inhibition effect of miR-24-3p. In brief, a series of data showed that miR-24-3p is a regulator of Smad5, playing an important role in osteogenic differentiation.

Regulation of DNA Double-Strand Break Repair by Non-Coding RNAs

DNA double-strand breaks (DSBs) are deleterious lesions that are generated in response to ionizing radiation or replication fork collapse that can lead to genomic instability and cancer. Eukaryotes have evolved two major pathways, namely homologous recombination (HR) and non-homologous end joining (NHEJ) to repair DSBs. Whereas the roles of protein-DNA interactions in HR and NHEJ have been fairly well defined, the functions of small and long non-coding RNAs and RNA-DNA hybrids in the DNA damage response is just beginning to be elucidated. This review summarizes recent discoveries on the identification of non-coding RNAs and RNA-mediated regulation of DSB repair.

Inhibition of miR-24 suppresses malignancy of human non-small cell lung cancer cells by targeting WWOX in vitro and in vivo

Background

We investigated the effect of micro‐RNA 24 (miR‐24) and WWOX on non‐small cell lung cancer (NSCLC) cell proliferation and migration in vitro and in vivo.

Methods

We performed bioinformatics analysis and 3′ untranslated region luciferase assay to investigate the direct target of miR‐24. Proliferation, apoptosis, and transwell invasion assays were employed to evaluate the effect of WWOX overexpression with pcDNA3‐WWOX and knocking down miR‐24 with miR‐24 small interfering RNA. Quantitative real‐time PCR, Western blot, and immunohistochemistry were also used to investigate miR‐24 and c‐Kit expression, and apoptosis and invasion‐related proteins. Finally, we constructed a tumor xenograft model in nude mice to confirm the effect of miR‐24 on NSCLC cell proliferation in vivo.

Results

According to our experimental data, miR‐24 inhibition could induce apoptosis by activating caspase 3 and suppress the viability and proliferation of NSCLC cells in vitro and in vivo. MiR‐24 downregulation could reduce the invasive ability of NSCLC cells by downregulating MMP9. WWOX was identified as a functional target of miR‐24. WWOX overexpression generated the same effect with antagonizing miR‐24, while blocking WWOX counteracted the tumor suppressive effect caused by miR‐24 inhibition. MiR‐24 may function as an oncogene and play an important role in the cell growth and migration of NSCLC.

Conclusions

Our findings enhance understanding of the miR‐24 regulatory network and the molecular mechanism that underlies the oncogenesis and development of NSCLC. Suppressing the effect of miR‐24 on cancer cells using a miR‐24 inhibitor may be an attractive therapeutic strategy against NSCLC.

Uncovering key small RNAs associated with gametocidal action in wheat

Gametocidal (Gc) chromosomes can kill gametes that lack them by causing chromosomal breakage to ensure their preferential transmission, and they have been exploited in genetic breeding. The present study investigated the possible roles of small RNAs (sRNAs) in Gc action. By sequencing two small RNA libraries from the anthers of Triticum aestivum cv. Chinese Spring (CS) and the Chinese Spring-Gc 3C chromosome monosomic addition line (CS-3C), we identified 239 conserved and 72 putative novel miRNAs, including 135 differentially expressed miRNAs. These miRNAs were predicted to target multiple genes with various molecular functions relevant to the features of Gc action, including sterility and genome instability. The transgenic overexpression of miRNA, which was up-regulated in CS-3C, reduced rice fertility. The CS-3C line exhibited a genome-wide reduction in 24 nt siRNAs compared with that of the CS line, particularly in transposable element (TE) and repetitive DNA sequences. Corresponding to this reduction, the bisulfite sequencing analysis of four retro-TE sequences showed a decrease in CHH methylation, typical of RNA-directed DNA methylation (RdDM). These results demonstrate that both miRNA-directed regulation of gene expression and siRNA-directed DNA methylation of target TE loci could play a role in Gc action.

Transcriptional activation of miR-320a by ATF2, ELK1 and YY1 induces cancer cell apoptosis under ionizing radiation conditions

MicroRNAs (miRNAs or miRs) play important roles in numerous cellular processes, including development, proliferation, tumorigenesis and apoptosis. It has been reported that miRNA expression is induced by ionizing radiation (IR) in cancer cells. However, the underlying molecular mechanisms are not yet fully understood. In this study, endogenous miR‑320a and its primary precursor (pri‑miR‑320a) were assayed by reverse transcription‑quantitative PCR (RT‑qPCR). Luciferase activities were measured using a dual‑luciferase reporter assay system. Western blot analysis was used to determine the protein expressions of upstream and downstream genes of miR‑320a. Cell apoptosis was evaluated by Annexin V apoptosis assay and cell proliferation was measured using the trypan blue exclusion method. The results revealed that miR‑320a expression increased linearly with the IR dose and treatment duration. Three transcription factors, activating transcription factor 2 (ATF2), ETS transcription factor (ELK1) and YY1 transcription factor (YY1), were activated by p38 mitogen‑activated protein kinase (MAPK) and mitogen‑activated protein kinase 8 (JNK) and by upregulated miR‑320a expression under IR conditions. In addition, it was identified that X‑linked inhibitor of apoptosis (XIAP) was an miR‑320a target gene during the IR response. By targeting XIAP, miR‑320a induced apoptosis and inhibited the proliferation of the cancer cells. On the whole, the results of this study demonstrated that miRNA‑320a, regulated by the p38 MAPK/JNK pathway, enhanced the radiosensitivity of cancer cells by inhibiting XIAP and this may thus prove to be a potential therapeutic approach with which to overcome radioresistance in cancer treatment.

c-Fos-dependent miR-22 targets MDC1 and regulates DNA repair in terminally differentiated cells

Terminally differentiated cells have a reduced capacity to repair double-stranded breaks (DSB) in DNA, however, the underlying molecular mechanism remains unclear. Here, we show that miR-22 is upregulated during postmitotic differentiation of human breast MCF-7 cells, hematopoietic HL60 and K562 cells. Increased expression of miR-22 in differentiated cells was associated with decreased expression of MDC1, a protein that plays a key role in the response to DSBs. This downregulation of MDC1 was accompanied by reduced DSB repair, impaired recruitment of the protein to the site of DNA damage following IR. Conversely, inhibiting miR-22 enhanced MDC1 protein levels, recovered MDC1 foci, fully rescued DSB repair in terminally differentiated cells. Moreover, MDC1 levels, IR-induced MDC1 foci, and the efficiency of DSB repair were fully rescued by siRNA-mediated knockdown of c-Fos in differentiated cells. These findings indicate that the c-Fos/miR-22/MDC1 axis plays a relevant role in DNA repair in terminally differentiated cells, which may facilitate our understanding of molecular mechanism underlying the downregulating DNA repair in differentiated cells.

MicroRNAs, Long Noncoding RNAs, and Their Functions in Human Disease

Majority of the human genome is transcribed into RNAs with absent or limited protein-coding potential. microRNAs (miRNAs) and long noncoding RNAs (lncRNAs) are two major families of the non-protein-coding transcripts. miRNAs and lncRNAs can regulate fundamental cellular processes via diverse mechanisms. The expression and function of miRNAs and lncRNAs are tightly regulated in development and physiological homeostasis. Dysregulation of miRNAs and lncRNAs is critical to pathogenesis of human disease. Moreover, recent evidence indicates a cross talk between miRNAs and lncRNAs. Herein we review recent advances in the biology of miRNAs and lncRNAs with respect to the above aspects. We focus on their roles in cancer, respiratory disease, and neurodegenerative disease. The complexity, flexibility, and versatility of the structures and functions of miRNAs and lncRNAs demand integration of experimental and bioinformatics tools to acquire sufficient knowledge for applications of these noncoding RNAs in clinical care.

Multitargeting activity of miR-24 inhibits long-term melatonin anticancer effects

We have previously shown that melatonin exerts tumor suppressor activities by inducing the p38-p53 axis. This occurred within a few hours while no data are available on how melatonin pathway can be sustained on the long term. Here we show that miR-24, which has been demonstrated to target genes involved in the DNA repair process, targets p38, p53, PML and H2AX simultaneously. We show that long-term treatment with melatonin can decrease miR-24 levels post-transcriptionally, which pairs with a long-wave regulation of genes involved in cell proliferation, DNA damage, RNA metabolism and cell shape and transformation. Moreover, we show that melatonin can inhibit cell proliferation and migration, at least in part, by downregulating miR-24. Furthermore, we propose the involvement of hnRNP A1, which is downregulated by melatonin and involved in miRNA processing, in the regulation of miR-24 levels by melatonin. We conclude showing that miR-24 is upregulated in colon, breast and head and neck datasets and its levels negatively correlate with overall survival.