The Potential for microRNA Therapeutics and Clinical Research

Regulation of cell growth and migration by miR-96 and miR-183 in a breast cancer model of epithelial-mesenchymal transition

Breast cancer is the most commonly diagnosed malignancy in women, and has the second highest mortality rate. Over 90% of all cancer-related deaths are due to metastasis, which is the spread of malignant cells from the primary tumor to a secondary site in the body. It is hypothesized that one cause of metastasis involves epithelial-mesenchymal transition (EMT). When epithelial cells undergo EMT and transition into mesenchymal cells, they display increased levels of cell proliferation and invasion, resulting in a more aggressive phenotype. While many factors regulate EMT, microRNAs have been implicated in driving this process. MicroRNAs are short noncoding RNAs that suppress protein production, therefore loss of microRNAs may promote the overexpression of specific target proteins important for EMT. The goal of this study was to investigate the role of miR-96 and miR-183 in EMT in breast cancer. Both miR-96 and miR-183 were found to be downregulated in post-EMT breast cancer cells. When microRNA mimics were transfected into these cells, there was a significant decrease in cell viability and migration, and a shift from a mesenchymal to an epithelial morphology (mesenchymal-epithelial transition or MET). These MET-related changes may be facilitated in part by the regulation of ZEB1 and vimentin, as both of these proteins were downregulated when miR-96 and miR-183 were overexpressed in post-EMT cells. These findings indicate that the loss of miR-96 and miR-183 may help facilitate EMT and contribute to the maintenance of a mesenchymal phenotype. Understanding the role of microRNAs in regulating EMT is significant in order to not only further elucidate the pathways that facilitate metastasis, but also identify potential therapeutic options for preventing or reversing this process.

MicroRNA-155-3p promotes glioma progression and temozolomide resistance by targeting Six1

The prognosis of glioma is generally poor and is the cause of primary malignancy in the brain. The role of microRNAs has been implicated in tumour inhibition or activation. In several cancers, the Six1 signalling pathway has been found to be aberrant and also relates to the formation of tumours. We analysed the database for expression profiles and clinical specimens of various grades of glioma to assess microRNA-155-3p (miR-155-3p) expression. The role of miR-155-3p in glioblastoma, cell cycle, proliferation, apoptosis and resistance to temozolomide was assessed in vitro through flow cytometry and cell proliferation assays. Bioinformatics analyses, and assays using luciferase reporter, and immunoblotting revealed that miR-155-3p targets Six1 and that the relationship between glioma and healthy brain tissues was significantly inverse. In rescue experiments, overexpressed Six1 revoked the changes in cell cycle distribution, proliferation and resistance to temozolomide estimated by apoptosis induced by overexpressed miR-155-3p. MiR-155-3p inhibition reduced glioma cell growth and proliferation in the brain of a mouse model and increased the survival of mice with gliomas. Thus, miR-155-3p modulates Six1 expression and facilitates the progression of glioblastoma and resistance to temozolomide and may act as a novel diagnostic biomarker and a target for glioma treatment.

MicroRNA Networks in Pancreatic Islet Cells: Normal Function and Type 2 Diabetes

Impaired insulin secretion from the pancreatic β-cells is central in the pathogenesis of type 2 diabetes (T2D), and microRNAs (miRNAs) are fundamental regulatory factors in this process. Differential expression of miRNAs contributes to β-cell adaptation to compensate for increased insulin resistance, but deregulation of miRNA expression can also directly cause β-cell impairment during the development of T2D. miRNAs are small noncoding RNAs that posttranscriptionally reduce gene expression through translational inhibition or mRNA destabilization. The nature of miRNA targeting implies the presence of complex and large miRNA-mRNA regulatory networks in every cell, including the insulin-secreting β-cell. Here we exemplify one such network using our own data on differential miRNA expression in the islets of T2D Goto-Kakizaki rat model. Several biological processes are influenced by multiple miRNAs in the β-cell, but so far most studies have focused on dissecting the mechanism of action of individual miRNAs. In this Perspective we present key islet miRNA families involved in T2D pathogenesis including miR-200, miR-7, miR-184, miR-212/miR-132, and miR-130a/b/miR-152. Finally, we highlight four challenges and opportunities within islet miRNA research, ending with a discussion on how miRNAs can be utilized as therapeutic targets contributing to personalized T2D treatment strategies.

From animal models to patients: the role of placental microRNAs, miR-210, miR-126, and miR-148a/152 in preeclampsia

Placental microRNAs (miRNAs) regulate the placental transcriptome and play a pathological role in preeclampsia (PE), a hypertensive disorder of pregnancy. Three PE rodent model studies explored the role of placental miRNAs, miR-210, miR-126, and miR-148/152 respectively, by examining expression of the miRNAs, their inducers, and potential gene targets. This review evaluates the role of miR-210, miR-126, and miR-148/152 in PE by comparing findings from the three rodent model studies with in vitro studies, other animal models, and preeclamptic patients to provide comprehensive insight into genetic components and pathological processes in the placenta contributing to PE. The majority of studies demonstrate miR-210 is upregulated in PE in part driven by HIF-1α and NF-κBp50, stimulated by hypoxia and/or immune-mediated processes. Elevated miR-210 may contribute to PE via inhibiting anti-inflammatory Th2-cytokines. Studies report an up- and downregulation of miR-126, arguably reflecting differences in expression between cell types and its multifunctional capacity. MiR-126 may play a pro-angiogenic role by mediating the PI3K-Akt pathway. Most studies report miR-148/152 family members are upregulated in PE. Evidence suggests they may inhibit DNA methylation of genes involved in metabolic and inflammatory pathways. Given the genetic heterogeneity of PE, it is unlikely that a single placental miRNA is a suitable therapeutic target for all patients. Investigating miRNAs in PE subtypes in patients and animal models may represent a more appropriate approach going forward. Developing methods for targeting placental miRNAs and specific placental cell types remains crucial for research seeking to target placental miRNAs as a novel treatment for PE.

Epigenetic regulation in human cancer: the potential role of epi-drug in cancer therapy

Epigenetics is dynamic and heritable modifications to the genome that occur independently of DNA sequence. It requires interactions cohesively with various enzymes and other molecular components. Aberrant epigenetic alterations can lead to inappropriate onset of genetic expressions and promote tumorigenesis. As the epigenetic modifiers are susceptible to extrinsic factors and reversible, they are becoming promising targets in multiple cancer therapies. Recently, various epi-drugs have been developed and implicated in clinical use. The use of epi-drugs alone, or in combination with chemotherapy or immunotherapy, has shown compelling outcomes, including augmentation of anti-tumoral effects, overcoming drug resistance, and activation of host immune response.

MicroRNAs-Based Nano-Strategies as New Therapeutic Approach in Multiple Myeloma to Overcome Disease Progression and Drug Resistance

MicroRNAs (miRNAs, or miRs) are single-strand short non-coding RNAs with a pivotal role in the regulation of physiological- or disease-associated cellular processes. They bind to target miRs modulating gene expression at post-transcriptional levels. Here, we present an overview of miRs deregulation in the pathogenesis of multiple myeloma (MM), and discuss the potential use of miRs/nanocarriers association in clinic. Since miRs can act as oncogenes or tumor suppressors, strategies based on their inhibition and/or replacement represent the new opportunities in cancer therapy. The miRs delivery systems include liposomes, polymers, and exosomes that increase their physical stability and prevent nuclease degradation. Phase I/II clinical trials support the importance of miRs as an innovative therapeutic approach in nanomedicine to prevent cancer progression and drug resistance. Results in clinical practice are promising.

Non-coding RNAs as Putative Biomarkers of Cancer-Associated Cachexia

Cachexia is a complex metabolic syndrome that determines a severe body weight loss characterized by a marked reduction in muscle mass. About 80% of patients with advanced cancer develop cachexia due to both the tumor itself and cancer treatment (radiotherapy and/or chemotherapy), which is associated to a worse prognosis. Despite its clinical relevance, this syndrome is still under-diagnosed and it lacks effective treatments. Radio-chemotherapy treatment is essential in patients with advanced head and neck cancers (HNSCC). Although this treatment has improved patients' life expectancy, it has also dramatically increased their need for assistance and support. The management of adverse symptoms, including cachexia, is of great importance in order to avoid delays in therapy, reduction of dosages and hospitalizations. MicroRNAs (miRNAs) are small non-coding RNA molecules, which have emerged as powerful biomarkers in stratifying human cancers. Due to their high stability in body fluids, miRNAs might be excellent non-invasive biomarkers for the early detection and follow-up of cancer patients. Here, we will summarize the current knowledge and debate the strong need to identify circulating biomarkers for the early diagnosis of cachexia. We will propose circulating non-coding RNAs as biomarkers for detecting early cachexia and implementing specific treatment. We will also discuss the potential use of circulating miRNAs as biomarkers of cachexia in HNSCC patients' blood samples collected before and after radio-chemotherapy treatment. Our intent is to pave the way to the identification of specific circulating miRNAs associated to cachexia occurrence and to the design of specific interventions aimed at improving the quality of life of cancer patients.

Transcription and Translation Inhibitors in Cancer Treatment

Transcription and translation are fundamental cellular processes that govern the protein production of cells. These processes are generally up regulated in cancer cells, to maintain the enhanced metabolism and proliferative state of these cells. As such cancerous cells can be susceptible to transcription and translation inhibitors. There are numerous druggable proteins involved in transcription and translation which make lucrative targets for cancer drug development. In addition to proteins, recent years have shown that the "undruggable" transcription factors and RNA molecules can also be targeted to hamper the transcription or translation in cancer. In this review, we summarize the properties and function of the transcription and translation inhibitors that have been tested and developed, focusing on the advances of the last 5 years. To complement this, we also discuss some of the recent advances in targeting oncogenes tightly controlling transcription including transcription factors and KRAS. In addition to natural and synthetic compounds, we review DNA and RNA based approaches to develop cancer drugs. Finally, we conclude with the outlook to the future of the development of transcription and translation inhibitors.

CREB1 is affected by the microRNAs miR-22-3p, miR-26a-5p, miR-27a-3p, and miR-221-3p and correlates with adverse clinicopathological features in renal cell carcinoma

The transcription factor cAMP response element-binding protein (CREB1) has been shown to be involved in diverse biological pathways including the regulation of cell proliferation, apoptosis, cell cycle progression, and metastasis. In this context, aberrant expression of CREB1 and the functional consequences are well investigated in a number of hematopoietic and solid tumors. However, CREB1 expression and underlying control mechanisms are only poorly analyzed in renal cell carcinoma (RCC). The present study confirmed a deregulation of CREB1 protein in the clear cell type of RCC (ccRCC) and analysis of in-house ccRCC cell lines suggested a post-transcriptional control. The combination of miRNA enrichment assay, in silico analysis and molecular biological approaches revealed four novel CREB1-regulating miRNAs, namely miR-22-3p, miR-26a-5p, miR-27a-3p, and miR-221-3p. Categorizing RCC samples as CREB1 negative or positive, respectively, the expression of these miRNAs was found to be inversely correlated with CREB1 protein levels. Analyzing 453 consecutive RCC tumors by immunohistochemistry, weakly negative, but significant correlations of CREB1 with tumor stage and grade, vascular invasion (V1) and lymphovascular invasion (L1) were found. In this respect, ccRCC might differ from other solid tumors like esophageal squamous-cell carcinoma or glioma.

Inhibition of miR-18a-3p reduces proliferation of mesothelioma cells and sensitizes them to cisplatin

Malignant pleural mesothelioma is a notorious human malignancy. Despite combination chemotherapy with cisplatin and pemetrexed, the majority of patients with advanced malignant pleural mesothelioma have a poor prognosis. MicroRNAs (miRNAs/miRs) are short non-coding RNAs that regulate various biological processes by binding to the 3'-untranslated region of target gene mRNAs and suppressing their expression. Since abnormal expression patterns of miRNAs are a common feature in human malignancies, a number of them have been researched as potential therapeutic targets. Our previous study demonstrated that microRNA-18a (miR-18a) is upregulated in mesothelioma cell lines compared with in non-neoplastic mesothelial tissues, but its function remains unclear. In the present study, miRNA inhibitor was transfected into mesothelioma cell lines and then analyzed various cellular functions. Mesothelioma cells transfected with the miR-18a inhibitor exhibited lower proliferation and migration rates compared with cells transfected with a negative control inhibitor in proliferation and wound scratch assays, respectively. Additionally, the present study revealed that downregulation of miR-18a increased mesothelioma cell apoptosis. In a chemosensitivity assay, transfection of the miR-18a inhibitor significantly increased the sensitivity of mesothelioma cells to cisplatin but not to pemetrexed. Therefore, miR-18a may be a potential therapeutic target for mesothelioma resistant to cisplatin.

The Promise and Challenges of Developing miRNA-Based Therapeutics for Parkinson's Disease

MicroRNAs (miRNAs) are small double-stranded RNAs that exert a fine-tuning sequence-specific regulation of cell transcriptome. While one unique miRNA regulates hundreds of mRNAs, each mRNA molecule is commonly regulated by various miRNAs that bind to complementary sequences at 3’-untranslated regions for triggering the mechanism of RNA interference. Unfortunately, dysregulated miRNAs play critical roles in many disorders, including Parkinson’s disease (PD), the second most prevalent neurodegenerative disease in the world. Treatment of this slowly, progressive, and yet incurable pathology challenges neurologists. In addition to L-DOPA that restores dopaminergic transmission and ameliorate motor signs (i.e., bradykinesia, rigidity, tremors), patients commonly receive medication for mood disorders and autonomic dysfunctions. However, the effectiveness of L-DOPA declines over time, and the L-DOPA-induced dyskinesias commonly appear and become highly disabling. The discovery of more effective therapies capable of slowing disease progression –a neuroprotective agent–remains a critical need in PD. The present review focus on miRNAs as promising drug targets for PD, examining their role in underlying mechanisms of the disease, the strategies for controlling aberrant expressions, and, finally, the current technologies for translating these small molecules from bench to clinics.

MicroRNA-146a regulates immune-related adverse events caused by immune checkpoint inhibitors

Immune checkpoint inhibitor (ICI) therapy has shown a significant benefit in the treatment of a variety of cancer entities. However, immune-related adverse events (irAEs) occur frequently and can lead to ICI treatment termination. MicroRNA-146a (miR-146a) has regulatory functions in immune cells. We observed that mice lacking miR-146a developed markedly more severe irAEs compared with WT mice in several irAE target organs in 2 different murine models. miR-146a-/- mice exhibited increased T cell activation and effector function upon ICI treatment. Moreover, neutrophil numbers in the spleen and the inflamed intestine were highly increased in ICI-treated miR-146a-/- mice. Therapeutic administration of a miR-146a mimic reduced irAE severity. To validate our preclinical findings in patients, we analyzed the effect of a SNP in the MIR146A gene on irAE severity in 167 patients treated with ICIs. We found that the SNP rs2910164 leading to reduced miR-146a expression was associated with an increased risk of developing severe irAEs, reduced progression-free survival, and increased neutrophil counts both at baseline and during ICI therapy. In conclusion, we characterized miR-146a as a molecular target for preventing ICI-mediated autoimmune dysregulation. Furthermore, we identified the MIR146A SNP rs2910164 as a biomarker to predict severe irAE development in ICI-treated patients.

In Vitro Biophysical and Biological Characterization of Lipid Nanoparticles Co-Encapsulating Oncosuppressors miR-199b-5p and miR-204-5p as Potentiators of Target Therapy in Metastatic Melanoma

Uncontrolled MAPK signaling is the main oncogenic driver in metastatic melanomas bearing mutations in BRAF kinase. These tumors are currently treated with the combination of BRAF/MEK inhibitors (MAPKi), but this therapy is plagued by drug resistance. In this context we recently discovered that several microRNAs are involved in the development of drug resistance. In particular miR-204-5p and miR-199b-5p were found to function as antagonists of resistance because their enforced overexpression is able to inhibit melanoma cell growth in vitro either alone or in combination with MAPKi. However, the use of miRNAs in therapy is hampered by their rapid degradation in serum and biological fluids, as well as by the poor intracellular uptake. Here, we developed lipid nanoparticles (LNPs) encapsulating miR-204-5p, miR-199b-5p individually or in combination. We obtained LNPs with mean diameters < 200 nm and high miRNA encapsulation efficiency. These formulations were tested in vitro on several melanoma cell lines sensitive to MAPKi or rendered drug resistant. Our results show that LNPs encapsulating combinations of the two oncosuppressor miRNAs are highly efficient in impairing melanoma cell proliferation and viability, affect key signaling pathways involved in melanoma cell survival, and potentiate the efficacy of drugs inhibiting BRAF and MEK. These results warrant further assessment of the anti-tumor efficacy of oncosuppressor miRNAs encapsulating LNPs in in vivo tumor models.

miR-1254 inhibits progression of glioma in vivo and in vitro by targeting CSF-1

The role of miRNAs (microRNAs) has been implicated in glioma initiation and progression, although the inherent biochemical mechanisms still remain to be unravelled. This study strived to evaluate the association between CSF-1 and miR-1254 and their effect on advancement of glioma cells. The levels of miR-1254 in glioma cells and tissues were determined by real-time RT-PCR. Proliferation, apoptosis and cell cycle arrest, invasion and migration, were assessed by CCK-8 assay, colony formation assay, flow cytometry, transwell assay and wound-healing assay, respectively. The targeted relationship between miR-1254 and CSF-1 was confirmed by dual-luciferase reporter assay. The effects of CSF-1 on cellular functions were also assessed. The in vivo effect of miR-1254 on the formation of a tumour was explored by using the mouse xenograft model. We found in both glioma tissues and glioma cells, the down-regulated expressions of miR-1254 while that of CSF-1 was abnormally higher than normal level. The target relationship between CSF-1 and miR-1254 was validated by dual-luciferase reporter assay. The CSF-1 down-regulation or miR-1254 overexpression impeded the invasion, proliferation and migratory ability of U251 and U87 glioma cells, concurrently occluded the cell cycle and induced cell apoptosis. Moreover, in vivo tumour development was repressed due to miR-1254 overexpression. Thus, CSF-1 is targeted directly by miR-1254, and the miR-1254/CSF-1 axis may be a potential diagnostic target for malignant glioma.

MicroRNA as a prognostic biomarker for survival in childhood acute lymphoblastic leukemia: a systematic review

Recent studies suggest abnormal microRNA (miRNA) expression may have potential prognostic value in childhood acute lymphoblastic leukemia (ALL). In this systematic review, we searched different databases (PubMed, ASH, ASCO, and SIOP) for studies published from 2008 to 2018 that evaluated the prognostic impact of miRNAs in childhood ALL. We also used DIANA-miRPath v3.0 to further characterize the functional role of the significant prognostic miRNAs identified in our systematic review. Here we evaluate 15 studies with a total of 38 different miRNAs and 1545 children with B-cell ALL (B-ALL) or T-cell ALL (T-ALL) recruited over approximately 3 decades (1984-2016) with different treatment protocols and ethnicities. Out of the 15 studies examined, 14 reported 32 dysregulated miRNAs with significant prognostic impact in pediatric ALL patients. Only one Brazilian study reported no significant prognostic effect of 7 miRNAs, while the seventh miRNA (miR-100) showed prognostic significance in a Chinese study. Using DIANA-TarBase v7.0 of DIANA-miRPath v3.0, pathway enrichment analysis revealed 25 miRNAs modulated 24 molecular pathways involved in cancer development. To remove the effect of salvage therapy, 9 studies carried out multivariate cox regression analysis for both relapse-free survival and disease-free survival to develop a panel of 23 miRNAs acting as independent prognostic biomarkers. To enhance the clinical application, utility, and validity of the miRNAs discussed here, their potential prognostic value should be confirmed in larger cohort studies within different ethnicities and different ALL protocols adjusted for other contemporary validated prognostic factors in childhood ALL.

snoRNAs Offer Novel Insight and Promising Perspectives for Lung Cancer Understanding and Management

Small nucleolar RNAs (snoRNAs) are non-coding RNAs localized in the nucleolus, where they participate in the cleavage and chemical modification of ribosomal RNAs. Their biogenesis and molecular functions have been extensively studied since their identification in the 1960s. However, their role in cancer has only recently started to emerge. In lung cancer, efforts to profile snoRNA expression have enabled the definition of snoRNA-related signatures, not only in tissues but also in biological fluids, exposing these small RNAs as potential non-invasive biomarkers. Moreover, snoRNAs appear to be essential actors of lung cancer onset and dissemination. They affect diverse cellular functions, from regulation of the cell proliferation/death balance to promotion of cancer cell plasticity. snoRNAs display both oncogenic and tumor suppressive activities that are pivotal in lung cancer tumorigenesis and progression. Altogether, we review how further insight into snoRNAs may improve our understanding of basic lung cancer biology and the development of innovative diagnostic tools and therapies.

Unveiling ncRNA regulatory axes in atherosclerosis progression

Completion of the human genome sequencing project highlighted the richness of the cellular RNA world, and opened the door to the discovery of a plethora of short and long non-coding RNAs (the dark transcriptome) with regulatory or structural potential, which shifted the balance of pathological gene alterations from coding to non-coding RNAs. Thus, disease risk assessment currently has to also evaluate the expression of new RNAs such as small micro RNAs (miRNAs), long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), competing endogenous RNAs (ceRNAs), retrogressed elements, 3'UTRs of mRNAs, etc. We are interested in the pathogenic mechanisms of atherosclerosis (ATH) progression in patients suffering Chronic Kidney Disease, and in this review, we will focus in the role of the dark transcriptome (non-coding RNAs) in ATH progression. We will focus in miRNAs and in the formation of regulatory axes or networks with their mRNA targets and with the lncRNAs that function as miRNA sponges or competitive inhibitors of miRNA activity. In this sense, we will pay special attention to retrogressed genomic elements, such as processed pseudogenes and Alu repeated elements, that have been recently seen to also function as miRNA sponges, as well as to the use or miRNA derivatives in gene silencing, anti-ATH therapies. Along the review, we will discuss technical developments associated to research in lncRNAs, from sequencing technologies to databases, repositories and algorithms to predict miRNA targets, as well as new approaches to miRNA function, such as integrative or enrichment analysis and their potential to unveil RNA regulatory networks.

Modulation of polycystic kidney disease by non-coding RNAs

PURPOSE OF REVIEW

microRNAs (miRNAs) are a class of small, evolutionarily conserved, non-coding RNAs (ncRNAs) that function as inhibitors of post-transcriptional mRNA expression. They are implicated in the pathogenesis of numerous diseases, including many common kidney conditions. In this review, we focus on how miRNAs impact autosomal dominant polycystic kidney disease (ADPKD) progression. We also discuss the feasibility of the emerging novel antisense oligonucleotides (ASOs) drug class, which includes anti-miRNA drugs, for the treatment of ADPKD.

RECENT FINDINGS

Aberrant miRNA expression is observed in multiple PKD murine models and human ADPKD samples. Gain and loss-of-function studies have directly linked dysregulated miRNA activity to kidney cyst growth. The most comprehensively studied miRNA in PKD is the miR-17 family, which promotes PKD progression through the rewiring of cyst metabolism and by directly inhibiting PKD1 and PKD2 expression. This discovery has led to the development of an anti-miR-17 drug for ADPKD treatment. Other miRNAs such as miR-21, miR-193, and miR-214 are also known to regulate cyst growth by modulating cyst epithelial apoptosis, proliferation, and interstitial inflammation.

SUMMARY

miRNAs have emerged as novel pathogenic regulators of ADPKD progression. Anti-miR-based drugs represent a new therapeutic modality to treat ADPKD patients.

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 CYP450 Drug Metabolism in Precision Cardio-Oncology

As many novel cancer therapies continue to emerge, the field of Cardio-Oncology (or onco-cardiology) has become crucial to prevent, monitor and treat cancer therapy-related cardiovascular toxicity. Furthermore, given the narrow therapeutic window of most cancer therapies, drug-drug interactions are prevalent in the cancer population. Consequently, there is an increased risk of affecting drug efficacy or predisposing individual patients to adverse side effects. Here we review the role of cytochrome P450 (CYP450) enzymes in the field of Cardio-Oncology. We highlight the importance of cardiac medications in preventive Cardio-Oncology for high-risk patients or in the management of cardiotoxicities during or following cancer treatment. Common interactions between Oncology and Cardiology drugs are catalogued, emphasizing the impact of differential metabolism of each substrate drug on unpredictable drug bioavailability and consequent inter-individual variability in treatment response or development of cardiovascular toxicity. This inter-individual variability in bioavailability and subsequent response can be further enhanced by genomic variants in CYP450, or by modifications of CYP450 gene, RNA or protein expression or function in various 'omics' related to precision medicine. Thus, we advocate for an individualized approach to each patient by a multidisciplinary team with clinical pharmacists evaluating a treatment plan tailored to a practice of precision Cardio-Oncology. This review may increase awareness of these key concepts in the rapidly evolving field of Cardio-Oncology.

miRNAs as Influencers of Cell-Cell Communication in Tumor Microenvironment

microRNAs (miRNAs) are small noncoding RNAs that regulate gene expression at the posttranscriptional level, inducing the degradation of the target mRNA or translational repression. MiRNAs are involved in the control of a multiplicity of biological processes, and their absence or altered expression has been associated with a variety of human diseases, including cancer. Recently, extracellular miRNAs (ECmiRNAs) have been described as mediators of intercellular communication in multiple contexts, including tumor microenvironment. Cancer cells cooperate with stromal cells and elements of the extracellular matrix (ECM) to establish a comfortable niche to grow, to evade the immune system, and to expand. Within the tumor microenvironment, cells release ECmiRNAs and other factors in order to influence and hijack the physiological processes of surrounding cells, fostering tumor progression. Here, we discuss the role of miRNAs in the pathogenesis of multicomplex diseases, such as Alzheimer’s disease, obesity, and cancer, focusing on the contribution of both intracellular miRNAs, and of released ECmiRNAs in the establishment and development of cancer niche. We also review growing evidence suggesting the use of miRNAs as novel targets or potential tools for therapeutic applications.

Small RNAs in eucaryotes: new clues for amplifying microRNA benefits

miRNAs, the smallest nucleotide molecules able to regulate gene expression at post transcriptional level, are found in both animals and plants being involved in fundamental processes for growth and development of living organisms. The number of miRNAs has been hypothesized to increase when some organisms specialized the process of mastication and grinding of food. Further to the vertical transmission, miRNAs can undergo horizontal transmission among different species, in particular between plants and animals. In the last years, an increasing number of studies reported that miRNA passage occurs through feeding, and that in animals, plant miRNAs can survive the gastro intestinal digestion and transferred by blood into host cells, where they can exert their functions modulating gene expression. The present review reports studies on miRNAs during evolution, with particular focus on biogenesis and mechanisms regulating their stability in plants and animals. The different biogenesis and post biogenesis modifications allow to discriminate miRNAs of plant origin from those of animal origin, and make it possible to better clarify the controversial question on whether a possible cross-kingdom miRNA transfer through food does exist. The majority of human medicines and supplements derive from plants and a regular consumption of plant food is suggested for their beneficial effects in the prevention of metabolic diseases, cancers, and dietary related disorders. So far, these beneficial effects have been generally attributed to the content of secondary metabolites, whereas mechanisms regarding other components remain unclear. Therefore, in light of the above reported studies miRNAs could result another component for the medical properties of plants. miRNAs have been mainly studied in mammals characterizing their sequences and molecular targets as available in public databases. The herein presented studies provide evidences that miRNA situation is much more complex than the static situation reported in databases. Indeed, miRNAs may have redundant activities, variable sequences, different methods of biogenesis, and may be differently influenced by external and environmental factors. In-depth knowledge of mechanisms of synthesis, regulation and transfer of plant miRNAs to other species can open new frontiers in the therapy of many human diseases, including cancer.

Non-coding RNA and lung cancer progression

Lung cancer (LC) is a major killer disease globally. This situation is further supported by yearly increase in new LC cases and its poor 5-year survival which is less than 15%. Although a large percentage of LC cases have been attributed to smoking, a considerable amount of nonsmokers also develops this disease, thereby suggesting a genetic and/or epigenetic undertone to LC development. Several growth-related genes such as epidermal growth factor receptor (EGFR) and vascular endothelial growth factor (VEGF) as well as tumor suppressor genes such as p53 have been implicated in LC pathogenesis and progression. Likewise, the genome only contains approximately 1% of coding regions. Hence, noncoding portion of the genome such as noncoding RNAs (ncRNAs) has been studied and discovered to play a cogent role in LC pathogenesis. More precisely, microRNAs (miRNAs) and long ncRNAs (lncRNAs) have been studied for decades. Posttranscriptional gene modulation function of miRNAs is well established and characterized. Likewise, the antagonizing interaction between lncRNAs and miRNAs had also been proven to further control gene expression during healthy and disease conditions like LC. More recently, renewed attention toward circular RNAs [circular RNAs (circRNAs)] study showed that circRNAs can also sponge miRNAs to modulate gene expressions too. Hence, miRNAs, lncRNAs, and circRNAs seem to function within a circuit to optimally determine which gene is needed to be upregulated or downregulated in biological system. Therefore, this review will discuss important ncRNAs, namely miRNA, lncRNA, and circRNA in LC progression. Paracrine effect of exosomal ncRNA will be also reviewed. In addition, the prospect of these ncRNAs in enhancing better LC treatment will be highlighted as well.

Advances in the discovery of microRNA-based anticancer therapeutics: latest tools and developments

Introduction: MicroRNAs (miRNAs) are small endogenous non-coding RNAs that repress the expression of their target genes by reducing mRNA stability and/or inhibiting translation. miRNAs are known to be aberrantly regulated in cancers. Modulators of miRNA (mimics and antagonists) have emerged as novel therapeutic tools for cancer treatment.Areas covered: This review summarizes the various strategies that have been applied to correct the dysregulated miRNA in cancer cells. The authors also discuss the recent advances in the technical development and preclinical/clinical evaluation of miRNA-based therapeutic agents.Expert opinion: Application of miRNA-based therapeutics for cancer treatment is appealing because they are able to modulate multiple dysregulated genes and/or signaling pathways in cancer cells. Major obstacles hindering their clinical development include drug delivery, off-target effects, efficacious dose determination, and safety. Tumor site-specific delivery of novel miRNA therapeutics may help to minimize off-target effects and toxicity. Combination of miRNA therapeutics with other anticancer treatment modalities could provide a synergistic effect, thus allowing the use of lower dose, minimizing off-target effects, and improving the overall safety profile in cancer patients. It is critical to identify individual miRNAs with cancer type-specific and context-specific regulation of oncogenes and tumor-suppressor genes in order to facilitate the precise use of miRNA anticancer therapeutics.

MicroRNAs as disease progression biomarkers and therapeutic targets in experimental autoimmune encephalomyelitis model of multiple sclerosis

Multiple sclerosis is an autoimmune neurodegenerative disease of the central nervous system characterized by pronounced inflammatory infiltrates entering the brain, spinal cord and optic nerve leading to demyelination. Focal demyelination is associated with relapsing-remitting multiple sclerosis, while progressive forms of the disease show axonal degeneration and neuronal loss. The tests currently used in the clinical diagnosis and management of multiple sclerosis have limitations due to specificity and sensitivity. MicroRNAs (miRNAs) are dysregulated in many diseases and disorders including demyelinating and neuroinflammatory diseases. A review of recent studies with the experimental autoimmune encephalomyelitis animal model (mostly female mice 6–12 weeks of age) has confirmed miRNAs as biomarkers of experimental autoimmune encephalomyelitis disease and importantly at the pre-onset (asymptomatic) stage when assessed in blood plasma and urine exosomes, and spinal cord tissue. The expression of certain miRNAs was also dysregulated at the onset and peak of disease in blood plasma and urine exosomes, brain and spinal cord tissue, and at the post-peak (chronic) stage of experimental autoimmune encephalomyelitis disease in spinal cord tissue. Therapies using miRNA mimics or inhibitors were found to delay the induction and alleviate the severity of experimental autoimmune encephalomyelitis disease. Interestingly, experimental autoimmune encephalomyelitis disease severity was reduced by overexpression of miR-146a, miR-23b, miR-497, miR-26a, and miR-20b, or by suppression of miR-182, miR-181c, miR-223, miR-155, and miR-873. Further studies are warranted on determining more fully miRNA profiles in blood plasma and urine exosomes of experimental autoimmune encephalomyelitis animals since they could serve as biomarkers of asymptomatic multiple sclerosis and disease course. Additionally, studies should be performed with male mice of a similar age, and with aged male and female mice.

MicroRNAs and Metastasis

Metastasis, the development of secondary malignant growths at a distance from the primary site of a cancer, is associated with almost 90% of all cancer deaths, and half of all cancer patients present with some form of metastasis at the time of diagnosis. Consequently, there is a clear clinical need for a better understanding of metastasis. The role of miRNAs in the metastatic process is beginning to be explored. However, much is still to be understood. In this review, we present the accumulating evidence for the importance of miRNAs in metastasis as key regulators of this hallmark of cancer.

Precision Medicine in Neurodegenerative Diseases: Some Promising Tips Coming from the microRNAs' World

: Novel insights in the development of a precision medicine approach for treating the neurodegenerative diseases (NDDs) are provided by emerging advances in the field of pharmacoepigenomics. In this context, microRNAs (miRNAs) have been extensively studied because of their implication in several disorders related to the central nervous system, as well as for their potential role as biomarkers of diagnosis, prognosis, and response to treatment. Recent studies in the field of neurodegeneration reported evidence that drug response and efficacy can be modulated by miRNA-mediated mechanisms. In fact, miRNAs seem to regulate the expression of pharmacology target genes, while approved (conventional and non-conventional) therapies can restore altered miRNAs observed in NDDs. The knowledge of miRNA pharmacoepigenomics may offers new clues to develop more effective treatments by providing novel insights into interindividual variability in drug disposition and response. Recently, the therapeutic potential of miRNAs is gaining increasing attention, and miRNA-based drugs (for cancer) have been under observation in clinical trials. However, the effective use of miRNAs as therapeutic target still needs to be investigated. Here, we report a brief review of representative studies in which miRNAs related to therapeutic effects have been investigated in NDDs, providing exciting potential prospects of miRNAs in pharmacoepigenomics and translational medicine.

An update review of deregulated tumor suppressive microRNAs and their contribution in various molecular subtypes of breast cancer

BACKGROUND

Breast cancer (BC) is histologically classified into hormone-receptor+ (ER+, PR + ), human epidermal growth factor receptor-2+ (Her2 + ), and triple-negative breast cancer (TNBC) types. The important contribution of tumor-suppressive (TS) microRNAs (miRs) in BC development and treatment have been well-acknowledged in the literature.

OBJECTIVE

The present review focused on the contribution of recently examined TS miRs in the progression and treatment of various histological subtypes of BC.

RESULTS

In summary, various miRs have tumor-suppressive roles in BC, so that their aberrant expression leads to the abnormality in the cellular processes such as enhanced cell growth, decreased apoptosis, cell migration and metastasis, and decreased sensitivity to chemotherapy through deregulated expression of oncogene targets of TS miRs.

CONCLUSION

TS miRs could be regarded as a proper molecular target for target therapy of BC. However, further in vitro and in vivo investigations are required to confirm the exact molecular functions of TS miRs in BC cells to offer more efficient targeted therapies.

An Emerging Role for isomiRs and the microRNA Epitranscriptome in Neovascularization

Therapeutic neovascularization can facilitate blood flow recovery in patients with ischemic cardiovascular disease, the leading cause of death worldwide. Neovascularization encompasses both angiogenesis, the sprouting of new capillaries from existing vessels, and arteriogenesis, the maturation of preexisting collateral arterioles into fully functional arteries. Both angiogenesis and arteriogenesis are highly multifactorial processes that require a multifactorial regulator to be stimulated simultaneously. MicroRNAs can regulate both angiogenesis and arteriogenesis due to their ability to modulate expression of many genes simultaneously. Recent studies have revealed that many microRNAs have variants with altered terminal sequences, known as isomiRs. Additionally, endogenous microRNAs have been identified that carry biochemically modified nucleotides, revealing a dynamic microRNA epitranscriptome. Both types of microRNA alterations were shown to be dynamically regulated in response to ischemia and are able to influence neovascularization by affecting the microRNA’s biogenesis, or even its silencing activity. Therefore, these novel regulatory layers influence microRNA functioning and could provide new opportunities to stimulate neovascularization. In this review we will highlight the formation and function of isomiRs and various forms of microRNA modifications, and discuss recent findings that demonstrate that both isomiRs and microRNA modifications directly affect neovascularization and vascular remodeling.

Systems and Synthetic microRNA Biology: From Biogenesis to Disease Pathogenesis

MicroRNAs (miRNAs) are approximately 22-nucleotide-long, small non-coding RNAs that post-transcriptionally regulate gene expression. The biogenesis of miRNAs involves multiple steps, including the transcription of primary miRNAs (pri-miRNAs), nuclear Drosha-mediated processing, cytoplasmic Dicer-mediated processing, and loading onto Argonaute (Ago) proteins. Further, miRNAs control diverse biological and pathological processes via the silencing of target mRNAs. This review summarizes recent findings regarding the quantitative aspects of miRNA homeostasis, including Drosha-mediated pri-miRNA processing, Ago-mediated asymmetric miRNA strand selection, and modifications of miRNA pathway components, as well as the roles of RNA modifications (epitranscriptomics), epigenetics, transcription factor circuits, and super-enhancers in miRNA regulation. These recent advances have facilitated a system-level understanding of miRNA networks, as well as the improvement of RNAi performance for both gene-specific targeting and genome-wide screening. The comprehensive understanding and modeling of miRNA biogenesis and function have been applied to the design of synthetic gene circuits. In addition, the relationships between miRNA genes and super-enhancers provide the molecular basis for the highly biased cell type-specific expression patterns of miRNAs and the evolution of miRNA-target connections, while highlighting the importance of alterations of super-enhancer-associated miRNAs in a variety of human diseases.

Metabolic Benefits of MicroRNA-22 Inhibition

Diabesity is a growing pandemic with substantial health and financial consequences. We are developing microRNA (miRNA)-based drug candidates that transform fat storing adipocytes into fat burning adipocytes (browning effect) to treat metabolic diseases characterized by lipotoxicity. Through phenotypic screening in primary cultures of human subcutaneous adipocytes, we discovered that inhibition of miRNA-22-3p by several complementary antagomirs resulted in increased lipid oxidation, mitochondrial activity, and energy expenditure (EE). These effects may be mediated through activation of target genes like KDM3A, KDM6B, PPARA, PPARGC1B, and SIRT1 involved in lipid catabolism, thermogenesis, and glucose homeostasis. In the model of Diet-Induced Obesity in mice of various ages, weekly subcutaneous injections of various miRNA-22-3p antagomirs produced a significant fat mass reduction, but no change of appetite or body temperature. Insulin sensitivity, as well as circulating glucose and cholesterol levels, was also improved. These original findings suggest that miRNA-22-3p inhibition could become a potent treatment of human obesity and type 2 diabetes mellitus, the so-called diabesity characterized by lipotoxicity and insulin resistance.

TGF-β and microRNA Interplay in Genitourinary Cancers

Genitourinary cancers (GCs) include a large group of different types of tumors localizing to the kidney, bladder, prostate, testis, and penis. Despite highly divergent molecular patterns, most GCs share commonly disturbed signaling pathways that involve the activity of TGF-β (transforming growth factor beta). TGF-β is a pleiotropic cytokine that regulates key cancer-related molecular and cellular processes, including proliferation, migration, invasion, apoptosis, and chemoresistance. The understanding of the mechanisms of TGF-β actions in cancer is hindered by the "TGF-β paradox" in which early stages of cancerogenic process are suppressed by TGF-β while advanced stages are stimulated by its activity. A growing body of evidence suggests that these paradoxical TGF-β actions could result from the interplay with microRNAs: Short, non-coding RNAs that regulate gene expression by binding to target transcripts and inducing mRNA degradation or inhibition of translation. Here, we discuss the current knowledge of TGF-β signaling in GCs. Importantly, TGF-β signaling and microRNA-mediated regulation of gene expression often act in complicated feedback circuits that involve other crucial regulators of cancer progression (e.g., androgen receptor). Furthermore, recently published in vitro and in vivo studies clearly indicate that the interplay between microRNAs and the TGF-β signaling pathway offers new potential treatment options for GC patients.

MicroRNAs in Tumor Cell Metabolism: Roles and Therapeutic Opportunities

Dysregulated metabolism is a common feature of cancer cells and is considered a hallmark of cancer. Altered tumor-metabolism confers an adaptive advantage to cancer cells to fulfill the high energetic requirements for the maintenance of high proliferation rates, similarly, reprogramming metabolism confers the ability to grow at low oxygen concentrations and to use alternative carbon sources. These phenomena result from the dysregulated expression of diverse genes, including those encoding microRNAs (miRNAs) which are involved in several metabolic and tumorigenic pathways through its post-transcriptional-regulatory activity. Further, the identification of key actionable altered miRNA has allowed to propose novel targeted therapies to modulated tumor-metabolism. In this review, we discussed the different roles of miRNAs in cancer cell metabolism and novel miRNA-based strategies designed to target the metabolic machinery in human cancer.

DNA methylation directs microRNA biogenesis in mammalian cells

MicroRNA (miRNA) biogenesis initiates co-transcriptionally, but how the Microprocessor machinery pinpoints the locations of short precursor miRNA sequences within long flanking regions of the transcript is not known. Here we show that miRNA biogenesis depends on DNA methylation. When the regions flanking the miRNA coding sequence are highly methylated, the miRNAs are more highly expressed, have greater sequence conservation, and are more likely to drive cancer-related phenotypes than miRNAs encoded by unmethylated loci. We show that the removal of DNA methylation from miRNA loci leads to their downregulation. Further, we found that MeCP2 binding to methylated miRNA loci halts RNA polymerase II elongation, leading to enhanced processing of the primary miRNA by Drosha. Taken together, our data reveal that DNA methylation directly affects miRNA biogenesis.

The pathogenesis of systemic lupus erythematosus: Harnessing big data to understand the molecular basis of lupus

Systemic lupus erythematosus (SLE) is a chronic, systemic autoimmune disease that causes damage to multiple organ systems. Despite decades of research and available murine models that capture some aspects of the human disease, new treatments for SLE lag behind other autoimmune diseases such as Rheumatoid Arthritis and Crohn's disease. Big data genomic assays have transformed our understanding of SLE by providing important insights into the molecular heterogeneity of this multigenic disease. Gene wide association studies have demonstrated more than 100 risk loci, supporting a model of multiple genetic hits increasing SLE risk in a non-linear fashion, and providing evidence of ancestral diversity in susceptibility loci. Epigenetic studies to determine the role of methylation, acetylation and non-coding RNAs have provided new understanding of the modulation of gene expression in SLE patients and identified new drug targets and biomarkers for SLE. Gene expression profiling has led to a greater understanding of the role of myeloid cells in the pathogenesis of SLE, confirmed roles for T and B cells in SLE, promoted clinical trials based on the prominent interferon signature found in SLE patients, and identified candidate biomarkers and cellular signatures to further drug development and drug repurposing. Gene expression studies are advancing our understanding of the underlying molecular heterogeneity in SLE and providing hope that patient stratification will expedite new therapies based on personal molecular signatures. Although big data analyses present unique interpretation challenges, both computationally and biologically, advances in machine learning applications may facilitate the ability to predict changes in SLE disease activity and optimize therapeutic strategies.

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.

miRNA-29b Inhibits Prostate Tumor Growth and Induces Apoptosis by Increasing Bim Expression

Prostate cancer is one of the most common cancers among men. Currently available therapies improve patient survival against local prostate cancer but have shown severe side effects. Advanced prostate cancer is still incurable. Studies have suggested the involvement of non-coding RNAs, especially micro-RNAs (miRNAs), in the regulation of multiple cellular events in cancer and thus several clinical trials are ongoing using miRNAs mimics or inhibitors. We previously demonstrated that miRNA-29b-3p (miR-29b) was downregulated in prostate cancer and that the overexpression of miR-29b limited prostate cancer metastasis. However, the therapeutic potential of the miR-29b against prostate cancer remains unknown. Here, we evaluated the therapeutic role of miR-29b in in vivo prostate tumors in a mouse model. Intratumoral injection of mimic miR-29b significantly inhibited prostate cancer xenograft tumor growth in nude mice. Subsequent study demonstrated that the overexpression of miR-29b reduced prostate cancer cell PC3 proliferation in a time dependent manner and induced cell death. Mechanistic study using a cancer pathway specific transcriptomic array revealed a significant overexpression of the pro-apoptotic gene BCL2L11 (Bim) in the miR-29b overexpressed PC3 cells, which was further verified in PC3 cells overexpressing miR-29b. We also observed a significant induction of Bim protein in miR-29b treated xenograft tumors. The induction of cytosolic accumulation of cytochrome C and PARP cleavage in miR-29b overexpressed PC3 cells was observed. Thus, our results suggest that miR-29b can be used as a potential molecule for prostate cancer therapy.

The Yin-Yang Regulation of Reactive Oxygen Species and MicroRNAs in Cancer

Reactive oxygen species (ROS) are highly reactive oxygen-containing chemical species formed as a by-product of normal aerobic respiration and also from a number of other cellular enzymatic reactions. ROS function as key mediators of cellular signaling pathways involved in proliferation, survival, apoptosis, and immune response. However, elevated and sustained ROS production promotes tumor initiation by inducing DNA damage or mutation and activates oncogenic signaling pathways to promote cancer progression. Recent studies have shown that ROS can facilitate carcinogenesis by controlling microRNA (miRNA) expression through regulating miRNA biogenesis, transcription, and epigenetic modifications. Likewise, miRNAs have been shown to control cellular ROS homeostasis by regulating the expression of proteins involved in ROS production and elimination. In this review, we summarized the significance of ROS in cancer initiation, progression, and the regulatory crosstalk between ROS and miRNAs in cancer.

The Multifunction Of miR-218-5p-Cx43 Axis In Breast Cancer

Background

Gemcitabine is proven to be the first-line standard treatment of breast cancers. Yet, little is known involving gemcitabine resistance and remains largely to be elucidated.

Materials and methods

We evaluated the expression of Cx43 in gemcitabine-resistant cells and parental cells by quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot analyses. Dual-luciferase reporter assay was applied to examine the epigenetic regulator of Cx43. The role of miR-218-5p-Cx43 axis on cell cytotoxicity, cell proliferation, colony formation, chemoresistance and migration was detected via mammalian expression vector and small short RNA (shRNA) transfection in vitro.

Results

In this study, we found that Cx43 expression levels were significantly lower in gemcitabine-resistant cells than in the parental cells. On deep investigation of the epigenetic regulation of Cx43, a few miRNA candidates targeting Cx43 were derived. Through dual-luciferase reporter assay, Cx43 was proved to be a direct target of miR-218-5p. Besides, qPCR, Western blot demonstrated an inverse correlation between miR-218-5p and Cx43 expression in breast cancer cells, thus forming the miR-218-5p-Cx43 axis. Notably, miR-218-5p-Cx43 axis was found to be involved in the process of gemcitabine chemoresistance, cell proliferation and migration in breast cancer cells.

Conclusion

Our findings suggested that miR-218-5p-Cx43 axis was versatile and indicated significant potency in breast cancer cells. More importantly, miR-218-5p-Cx43 axis might be valuable in translational medicine, with therapeutic and prognostic information.

MicroRNAs: potential targets and agents of endocrine disruption in female reproduction

MicroRNAs are short non-coding RNAs that have been widely recognized as key mediators in the epigenetic control of gene expression and which are present in virtually all cells and tissues studied. These regulatory molecules are generated in multiple steps in a process called microRNA biogenesis. Distinct microRNA expression patterns during the different stages of oocyte and embryo development suggest important regulatory roles for these small RNAs. Moreover, studies antagonizing specific microRNAs and enzymes in microRNA biogenesis pathways have demonstrated that interference with normal miRNA function leads to infertility and is associated with some reproductive abnormalities. Endocrine disrupting chemicals such as Bisphenol A (BPA) are synthetic hormone mimics that have been found to negatively impact reproductive health. In addition to their direct effects on gene expression, these chemicals are widely implicated in the disruption of epigenetic pathways, including the expression and activity of miRNAs, thereby altering gene expression. In this review, the roles of microRNAs during mammalian oocyte and embryo development are outlined and the different mechanisms by which endocrine disruptors such as BPA interfere with these epigenetic regulators to cause reproductive problems is explored.

MicroRNA Regulation of the Autotaxin-Lysophosphatidic Acid Signaling Axis

The revelation that microRNAs (miRNAs) exist within the human genome uncovered an underappreciated mechanism of gene expression. For cells to regulate expression of their genes, miRNA molecules and argonaute proteins bind to mRNAs and interfere with efficient translation of the RNA transcript. Although miRNAs have important roles in normal tissues, miRNAs may adopt aberrant functions in malignant cells depending on their classification as either a tumor suppressor or oncogenic miRNA. Within this review, the current status of miRNA regulation is described in the context of signaling through the lysophosphatidic acid receptors, including the lysophosphatidic acid-producing enzyme, autotaxin. Thus far, research has revealed miRNAs that increase in response to lysophosphatidic acid stimulation, such as miR-21, miR-30c-2-3p, and miR-122. Other miRNAs inhibit the translation of lysophosphatidic acid receptors, such as miR-15b, miR-23a, and miR200c, or proteins that are downstream of lysophosphatidic acid signaling, such as miR-146 and miR-21. With thousands of miRNAs still uncharacterized, it is anticipated that the complex regulation of lysophosphatidic acid signaling by miRNAs will continue to be elucidated. RNA-based therapeutics have entered the clinic with enormous potential in precision medicine. This exciting field is rapidly emerging and it will be fascinating to witness its expansion in scope.

MicroRNAs as modulators of longevity and the aging process

MicroRNAs (miRNAs) are short, non-coding RNAs that post-transcriptionally repress translation or induce mRNA degradation of target transcripts through sequence-specific binding. miRNAs target hundreds of transcripts to regulate diverse biological pathways and processes, including aging. Many microRNAs are differentially expressed during aging, generating interest in their use as aging biomarkers and roles as regulators of the aging process. In the invertebrates Caenorhabditis elegans and Drosophila, a number of miRNAs have been found to both positive and negatively modulate longevity through canonical aging pathways. Recent studies have also shown that miRNAs regulate age-associated processes and pathologies in a diverse array of mammalian tissues, including brain, heart, bone, and muscle. The review will present an overview of these studies, highlighting the role of individual miRNAs as biomarkers of aging and regulators of longevity and tissue-specific aging processes.