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

Elucidation of how the Mir-23-27-24 cluster regulates development and aging

MicroRNAs (miRNAs) are pivotal regulators of gene expression and are involved in biological processes spanning from early developmental stages to the intricate process of aging. Extensive research has underscored the fundamental role of miRNAs in orchestrating eukaryotic development, with disruptions in miRNA biogenesis resulting in early lethality. Moreover, perturbations in miRNA function have been implicated in the aging process, particularly in model organisms such as nematodes and flies. miRNAs tend to be clustered in vertebrate genomes, finely modulating an array of biological pathways through clustering within a single transcript. Although extensive research of their developmental roles has been conducted, the potential implications of miRNA clusters in regulating aging remain largely unclear. In this review, we use the Mir-23-27-24 cluster as a paradigm, shedding light on the nuanced physiological functions of miRNA clusters during embryonic development and exploring their potential involvement in the aging process. Moreover, we advocate further research into the intricate interplay among miRNA clusters, particularly the Mir-23-27-24 cluster, in shaping the regulatory landscape of aging.

Melatonin and Its Role in the Epithelial-to-Mesenchymal Transition (EMT) in Cancer

The epithelial-to-mesenchymal transition (EMT) is a cell-biological program that occurs during the progression of several physiological processes and that can also take place during pathological situations such as carcinogenesis. The EMT program consists of the sequential activation of a number of intracellular signaling pathways aimed at driving epithelial cells toward the acquisition of a series of intermediate phenotypic states arrayed along the epithelial-mesenchymal axis. These phenotypic features include changes in the motility, conformation, polarity and functionality of cancer cells, ultimately leading cells to stemness, increased invasiveness, chemo- and radioresistance and the formation of cancer metastasis. Amongst the different existing types of the EMT, type 3 is directly involved in carcinogenesis. A type 3 EMT occurs in neoplastic cells that have previously acquired genetic and epigenetic alterations, specifically affecting genes involved in promoting clonal outgrowth and invasion. Markers such as E-cadherin; N-cadherin; vimentin; and transcription factors (TFs) like Twist, Snail and ZEB are considered key molecules in the transition. The EMT process is also regulated by microRNA expression. Many miRNAs have been reported to repress EMT-TFs. Thus, Snail 1 is repressed by miR-29, miR-30a and miR-34a; miR-200b downregulates Slug; and ZEB1 and ZEB2 are repressed by miR-200 and miR-205, respectively. Occasionally, some microRNA target genes act downstream of the EMT master TFs; thus, Twist1 upregulates the levels of miR-10b. Melatonin is an endogenously produced hormone released mainly by the pineal gland. It is widely accepted that melatonin exerts oncostatic actions in a large variety of tumors, inhibiting the initiation, progression and invasion phases of tumorigenesis. The molecular mechanisms underlying these inhibitory actions are complex and involve a great number of processes. In this review, we will focus our attention on the ability of melatonin to regulate some key EMT-related markers, transcription factors and micro-RNAs, summarizing the multiple ways by which this hormone can regulate the EMT. Since melatonin has no known toxic side effects and is also known to help overcome drug resistance, it is a good candidate to be considered as an adjuvant drug to conventional cancer therapies.

Tumor microenvironment remodeling in oral cancer: Application of plant derived-natural products and nanomaterials

Oral cancers consist of squamous cell carcinoma (SCC) and other malignancies in the mouth with varying degrees of invasion and differentiation. For many years, different modalities such as surgery, radiation therapy, and classical chemotherapy drugs have been used to control the growth of oral tumors. Nowadays, studies have confirmed the remarkable effects of the tumor microenvironment (TME) on the development, invasion, and therapeutic resistance of tumors like oral cancers. Therefore, several studies have been conducted to modulate the TME in various types of tumors in favor of cancer suppression. Natural products are intriguing agents for targeting cancers and TME. Flavonoids, non-flavonoid herbal-derived molecules, and other natural products have shown promising effects on cancers and TME. These agents, such as curcumin, resveratrol, melatonin, quercetin and naringinin have demonstrated potency in suppressing oral cancers. In this paper, we will review and discuss about the potential efficacy of natural adjuvants on oral cancer cells. Furthermore, we will review the possible therapeutic effects of these agents on the TME and oral cancer cells. Moreover, the potential of nanoparticles-loaded natural products for targeting oral cancers and TME will be reviewed. The potentials, gaps, and future perspectives for targeting TME by nanoparticles-loaded natural products will also be discussed.

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.

A comprehensive understanding of hnRNP A1 role in cancer: new perspectives on binding with noncoding RNA

The heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1) is the most abundant and ubiquitously expressed member of the heterogeneous nuclear ribonucleoproteins family (hnRNPs). hnRNP A1 is an RNA-binding protein associated with complexes active in diverse biological processes such as RNA splicing, transactivation of gene expression, and modulation of protein translation. It is overexpressed in several cancers, where it actively promotes the expression and translation of several key proteins and regulators associated with tumorigenesis and cancer progression. Interesting recent studies have focused on the RNA-binding property of hnRNP A1 and revealed previously under-explored functions of hnRNP A1 in the processing of miRNAs, and loading non-coding RNAs into exosomes. Here, we will report the recent advancements in our knowledge of the role of hnRNP A1 in the biological processes underlying cancer proliferation and growth, with a particular focus on metabolic reprogramming.

Interactions of melatonin with various signaling pathways: implications for cancer therapy

Melatonin is a neuro-hormone with conserved roles in evolution. Initially synthetized as an antioxidant molecule, it has gained prominence as a key molecule in the regulation of the circadian rhythm. Melatonin exerts its effect by binding to cytoplasmic and intra-nuclear receptors, and is able to regulate the expression of key mediators of different signaling pathways. This ability has led scholars to investigate the role of melatonin in reversing the process of carcinogenesis, a process in which many signaling pathways are involved, and regulating these pathways may be of clinical significance. In this review, the role of melatonin in regulating multiple signaling pathways with important roles in cancer progression is discussed, and evidence regarding the beneficence of targeting malignancies with this approach is presented.

The therapeutic effect and mechanism of melatonin on osteoarthritis: From the perspective of non-coding RNAs

Osteoarthritis (OA) is a slowly progressing and irreversible joint disease. The existing non-surgical treatment can only delay its progress, making the early treatment of OA a research hotspot in recent years. Melatonin, a neurohormone mainly secreted by the pineal gland, has a variety of regulatory functions in different organs, and numerous studies have confirmed its therapeutic effect on OA. Non-coding RNAs (ncRNAs) constitute the majority of the human transcribed genome. Various ncRNAs show significant differentially expressed between healthy people and OA patients. ncRNAs play diverse roles in many cellular processes and have been implicated in many pathological conditions, especially OA. Interestingly, the latest research found a close interaction between ncRNAs and melatonin in regulating the pathogenesis of OA. This review discusses the current understanding of the melatonin-mediated modulation of ncRNAs in the early stage of OA. We also delineate the potential link between rhythm genes and ncRNAs in chondrocytes. This review will serve as a solid foundation to formulate ideas for future mechanistic studies on the therapeutic potential of melatonin and ncRNAs in OA and better explore the emerging functions of the ncRNAs.

Versatile role of miR-24/24-1*/24-2* expression in cancer and other human diseases

MiRNAs (miRs) have been proven to be well-validated therapeutic targets. Emerging evidence has demonstrated that intricate, intrinsic and paradoxical functions of miRs are context-dependent because of their multiple upstream regulators, broad spectrum of downstream molecular targets and distinct expression in various tissues, organs and disease states. Targeted therapy has become an emerging field of research. One key for the development of successful miR-based/targeted therapy is to acquire integrated knowledge of its regulatory network and its association with disease phenotypes to identify critical nodes of the underlying pathogenesis. Herein, we systematically summarized the comprehensive role of miR-24-3p (miR-24), along with its passenger strands miR-24-1-5p* (miR-24-1) and miR-24-2-5p* (miR-24-2), emphasizing their microenvironment, intracellular targets, and associated gene networks and regulatory phenotypes in 18 different cancer types and 13 types of other disorders. MiR-24 targets and regulates numerous genes in various cancer types and enhances the expression of several oncogenes (e.g., cMyc, BCL2 and HIF1), which are challenging in terms of druggability. In contrast, several tumor suppressor proteins (p21 and p53) have been reported to be downregulated by miR-24. MiR-24 also regulates the cell cycle and is associated with numerous cancer hallmarks such as apoptosis, proliferation, metastasis, invasion, angiogenesis, autophagy, drug resistance and other diseases pathogenesis. Overall, miR-24 plays an emerging role in the diagnosis, prognosis and pathobiology of various diseases. MiR-24 is a potential target for targeted therapy in the era of precision medicine, which expands the landscape of targetable macromolecules, including undruggable proteins.

Antitumor and Protective Effects of Melatonin: The Potential Roles of MicroRNAs

MicroRNAs (miRNAs) are endogenous short noncoding RNAs with approximately 22 nucleotides. The primary function of miRNAs is the negative regulation of target gene expression via mRNA degradation or translation inhibition. During recent years, much attention has been made toward miRNAs' role in different disorders; particularly cancer and compounds with modulatory effects on miRNAs are of interest. Melatonin is one of these compounds which is secreted by the pineal gland. Also, melatonin is present in the leaves, fruits, and seeds of plants. Melatonin has several valuable biological activities such as antioxidant, anti-inflammation, antitumor, and antiaging activities. This important agent is extensively used to treat different disorders such as cancer and neurodegenerative and cardiovascular diseases. This review aims to describe the modulatory effect of melatonin on miRNAs as novel targets.

Melatonin as a promising modulator of aging related neurodegenerative disorders: Role of microRNAs

One of the host risk factors involved in aging-related diseases is coupled with the reduction of endogenous melatonin (MLT) synthesis in the pineal gland. MLT is considered a well-known pleiotropic regulatory hormone to modulate a multitude of biological processes such as the regulation of circadian rhythm attended by potent anti-oxidant, anti-inflammatory, and anti-cancer properties. It has also been established that the microRNAs family, as non-coding mRNAs regulating post-transcriptional processes, also serve a crucial role to promote MLT-related advantageous effects in both experimental and clinical settings. Moreover, the anti-aging impact of MLT and miRNAs participation jointly are of particular interest, recently. In this review, we aimed to scrutinize recent advances concerning the therapeutic implications of MLT, particularly in the brain tissue in the face of aging. We also assessed the possible interplay between microRNAs and MLT, which could be considered a therapeutic strategy to slow down the aging process in the nervous system.

Potential Therapeutic Effects of Melatonin Mediate via miRNAs in Cancer

miRNAs are evolutionarily conserved non-coding ribonucleic acids with a length of between 19 and 25 nucleotides. Because of their ability to regulate gene expression, miRNAs have an important function in the controlling of various biological processes, such as cell cycle, differentiation, proliferation, and apoptosis. Owing to the long-standing regulative potential of miRNAs in tumor-suppressive pathways, scholars have recently paid closer attention to the expression profile of miRNAs in various types of cancer. Melatonin, an indolic compound secreted from pineal gland and some peripheral tissues, has been considered as an effective anti-tumor hormone in a wide spectrum of cancers. Furthermore, it induces apoptosis, inhibits tumor metastasis and invasion, and also angiogenesis. A growing body of evidence indicates the effects of melatonin on miRNAs expression in broad spectrum of diseases, including cancer. Due to the long-term effects of the regulation of miRNAs expression, melatonin could be a promising therapeutic factor in the treatment of cancers via the regulation of miRNAs. Therefore, in this review, we will discuss the effects of melatonin on miRNAs expression in various types of cancers.

Melatonin and its mechanism of action in the female reproductive system and related malignancies

Melatonin (N-acetyl-5-methoxytryptamine), the main product of pineal gland in vertebrates, is well known for its multifunctional role which has great influences on the reproductive system. Recent studies documented that melatonin is a powerful free radical scavenger that affects the reproductive system function and female infertility by MT1 and MT2 receptors. Furthermore, cancer researches indicate the influence of melatonin on the modulation of tumor cell signaling pathways resulting in growth inhibitor of the both in vivo/in vitro models. Cancer adjuvant therapy can also benefit from melatonin through therapeutic impact and decreasing the side effects of radiation and chemotherapy. This article reviews the scientific evidence about the influence of melatonin and its mechanism of action on the fertility potential, physiological alteration, and anticancer efficacy, during experimental and clinical studies.

MiR-24-3p as a prognostic indicator for multiple cancers: from a meta-analysis view

A growing number of researches suggest that microRNAs (miRNAs) as oncogene or tumor suppressor genes play a fundamental role in various kinds of cancers. Among them, miR-24-3p, as a star molecule, is widely studied. However, the prognostic value of miR-24-3p is unclear and controversial. We conducted this meta-analysis to evaluate the prognostic value of miR-24-3p in a variety of cancers by integrated existing articles from four databases. PubMed, Embase, Web of Science, and Cochrane Library (last update in March 2020) were searched for approach literature. Hazard ratios (HRs) and odds ratios (ORs) were used to evaluate the association between miR-24-3p expression levels and prognostic value or clinicopathological characteristics, respectively. A total of 15 studies from 14 literature were finally qualified and concluded in the present meta-analysis. A significantly worse overall survival was observed in higher expression of miR-24-3p cancer group for OS (overall survival) of log-rank tests and Cox multivariate regression by fixed effects model. Also, we found a significant correlation between elevated miR-24-3p levels to RFS (recurrence-free survival) and DFS (disease-free survival). In addition, the pooled odds ratios (ORs) showed that evaluated miR-24-3p was also associated with the larger tumor size (≥5 cm) and advanced TNM stage (III and IV). Built on the above findings, elevated expression levels of miR-24-3p may serve as a promising biomarker used to predict the worse prognosis of cancer patients.

Melatonin and regulation of miRNAs: novel targeted therapy for cancerous and noncancerous disease

miRNAs, small noncoding RNAs with crucial diagnostic and prognostic capabilities, play essential therapeutic roles in different human diseases. These biomarkers are involved in several biological mechanisms and are responsible for the regulation of multiple genes expressions in cells. miRNA-based therapy has shown a very bright future in the case of clinical interventions. Melatonin, the main product of the pineal gland, is a multifunctional neurohormone with numerous therapeutic potentials in human diseases. Melatonin is able to regulate miRNAs in different pathologies such as malignant and nonmalignant diseases, which can be considered as a novel kind of targeted therapy. Herein, this review discusses possible therapeutic utility of melatonin for the regulation of miRNAs in various pathological conditions.

miRNAs and radiotherapy response in prostate cancer

BACKGROUND

Gaining insight into microRNAs (miRNAs) and genes that regulate the therapeutic response of cancer diseases in general and prostate cancer (PCa) in particular is an important issue in current molecular biomedicine and allows the discovery of predictive miRNA targets.

OBJECTIVES

The aim of this study was to analyze the available data on the influence of radiotherapy (RT) on miRNA expression and on miRNA involved in radiotherapy response in PCa.

MATERIALS AND METHODS

The data used in this review were extracted from research papers and the DIANA, STRING, and other databases with a special focus on the mechanisms of radiotherapy PCa response and the miRNA involved and associated genes.

RESULTS AND DISCUSSION

A search for miRNA prognostic and therapeutic effectiveness markers should rely on both the data of recent experimental studies on the influence of RT on miRNA expression and miRNAs involved in regulation of radiosensitivity in PCa and on bioinformatics resources. miRNA panels and genes targeted by them and involved in radioresponse regulation highlighted by meta-analysis and cross-analysis of the data in the present review have.

CONCLUSION

Selected miRNA and gene panel has good potential as prognostic and radiotherapy effectiveness markers for PCa and, moreover, as radiotherapy effectiveness markers in other types of cancer, as the proposed model is not specific to PCa, which opens up opportunities for the development of a universal diagnostic system (or several intersecting systems) for oncology radiotherapy in general.

A meta-analysis of microRNA networks regulated by melatonin in cancer: Portrait of potential candidates for breast cancer treatment

Melatonin is a ubiquitous molecule with a broad spectrum of functions including widespread anti-cancer activities. Identifying how melatonin intervenes in complex molecular signaling at the gene level is essential to guide proper therapies. Using meta-analysis approach, herein we examined the role of melatonin in regulating the expression of 46 microRNAs (miRNAs) and their target genes in breast, oral, gastric, colorectal, and prostate cancers, and glioblastoma. The deregulated miRNA-associated target genes revealed their involvement in the regulation of cellular proliferation, differentiation, apoptosis, senescence, and autophagy. Melatonin changes the expression of miRNA-associated genes in breast, gastric, and oral cancers. These genes are associated with cellular senescence, the hedgehog signaling pathway, cell proliferation, p53 signaling, and the hippo signaling pathway. Conversely, colorectal and prostate cancers as well as glioblastoma and oral carcinoma present a clear pattern of less pronounced changes in the expression of miRNA-associated genes. Most notably, colorectal cancer displayed a unique molecular change in response to melatonin. Considering breast cancer network complexity, we compared the genes found during the meta-analysis with RNA-Seq data from breast cancer-bearing mice treated with melatonin. Mechanistically, melatonin upregulated genes associated with immune responses and apoptotic processes, whereas it downregulated genes involved in cellular aggressiveness/metastasis (eg, mitosis, telomerase activity, and angiogenesis). We further characterized the expression profile of our gene subsets with human breast cancer and found eight upregulated genes and 16 downregulated genes that were appositively correlated with melatonin. Our results pose a multi-dimension network of tumor-associated genes regulated by miRNAs potentially targeted by melatonin.

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.

Inhibition of endogenous hydrogen sulfide biosynthesis enhances the anti-cancer effect of 3,3'-diindolylmethane in human gastric cancer cells

AIMS

3,3'-Diindolylmethane (DIM) has limited anti-cancer effects in gastric cancer. Hydrogen sulfide (H₂S) plays an important role in the tumor development and therapy, cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE), two key endogenous H₂S biosynthesis enzymes, can affect endogenous H₂S levels and alter cancer treatment. Our main objective was to investigate whether the aminooxyacetic acid (AOAA) and DL-Propargylglycine (PAG), two specific inhibitors of CBS and CSE, could assist DIM to exert a stronger anti-cancer effects in gastric cancer BGC-823 and SGC-7901 cells.

MATERIALS AND METHODS

Cell proliferation was assayed by MTT and cell colony-forming assay. Apoptosis and migration were detected by Hoechst staining and scratch test respectively. Western blot was used to evaluate the expression of proteins related to proliferation, apoptosis and migration.

KEY FINDINGS

Combination of AOAA or PAG with DIM synergistically inhibited proliferation and migration, increased apoptosis in gastric cancer cells. The p38-p53 axis was also further activated by the combination of AOAA or PAG with DIM. Exogenous H₂S from sodium hydrosulfide, attenuated the efficacy of DIM in cancer cells by reducing the activation level of p38-p53 axis. Taken together, AOAA or PAG inhibited the expression of endogenous H₂S biosynthesis enzymes and effectively enhanced susceptibility of gastric cancer to DIM through activating p38-p53 axis.

SIGNIFICANCE

The current study highlight more precise requirements for the clinical application of sulfur-containing anti-cancer drugs, and open a new way to enhance the sensitivity of DIM in chemotherapy of gastric cancer.

Therapeutic Potential of Melatonin in the Regulation of MiR-148a-3p and Angiogenic Factors in Breast Cancer

BACKGROUND

The high mortality rate of breast cancer is related to the occurrence of metastasis, a process that is promoted by tumor angiogenesis. MicroRNAs are small molecules of noncoding mRNA that play a key role in gene regulation and are directly involved in the progression and angiogenesis of various tumor types, including breast cancer. Several miRNAs have been described as promoters or suppressors angiogenesis and may be associated with tumor growth and metastasis. Melatonin is an oncostatic agent with a capacity of modifying the expression of innumerable genes and miRNAs related to cancer.

OBJECTIVE

The aim of this study was to evaluate the role of melatonin and the tumor suppressor miR- 148a-3p on angiogenesis of breast cancer.

METHOD

MDA-MB-231 cells were treated with melatonin and modified with the overexpression of miR-148a-3p. The relative quantification in real-time of miR-148a-3p, IGF-IR and VEGF was performed by real-time PCR. The protein expression of these targets was performed by immunocytochemistry and immunohistochemistry. Survival, migration and invasion rates of tumor cells were evaluated. Finally, the xenograft model of breast cancer was performed to confirm the role of melatonin in the tumor.

RESULTS

The melatonin was able to increase the gene level of miR-148a-3p and decreased the gene and protein expression of IGF-1R and VEGF, both in vitro and in vivo. In addition, it also had an inhibitory effect on the survival, migration and invasion of breast tumor cells.

CONCLUSION

Our results confirm the role of melatonin in the regulation of miR-148a-3p and decrease of angiogenic factors.

Genome-Protecting Compounds as Potential Geroprotectors

Throughout life, organisms are exposed to various exogenous and endogenous factors that cause DNA damages and somatic mutations provoking genomic instability. At a young age, compensatory mechanisms of genome protection are activated to prevent phenotypic and functional changes. However, the increasing stress and age-related deterioration in the functioning of these mechanisms result in damage accumulation, overcoming the functional threshold. This leads to aging and the development of age-related diseases. There are several ways to counteract these changes: 1) prevention of DNA damage through stimulation of antioxidant and detoxification systems, as well as transition metal chelation; 2) regulation of DNA methylation, chromatin structure, non-coding RNA activity and prevention of nuclear architecture alterations; 3) improving DNA damage response and repair; 4) selective removal of damaged non-functional and senescent cells. In the article, we have reviewed data about the effects of various trace elements, vitamins, polyphenols, terpenes, and other phytochemicals, as well as a number of synthetic pharmacological substances in these ways. Most of the compounds demonstrate the geroprotective potential and increase the lifespan in model organisms. However, their genome-protecting effects are non-selective and often are conditioned by hormesis. Consequently, the development of selective drugs targeting genome protection is an advanced direction.

Melatonin attenuates doxorubicin-induced cardiotoxicity through preservation of YAP expression

There are increasing concerns related to the cardiotoxicity of doxorubicin in the clinical setting. Recently, melatonin has been shown to exert a cardioprotective effect in various cardiovascular diseases, including cardiotoxic conditions. In this study, we examined the possible protective effects of melatonin on doxorubicin‐induced cardiotoxicity and explored the underlying mechanisms related to this process. We found that in vitro doxorubicin treatment significantly decreased H9c2 cell viability and induced apoptosis as manifested by increased TUNEL‐positive cells, down‐regulation of anti‐apoptotic protein Bcl‐2, as well as up‐regulation of pro‐apoptotic protein Bax. This was associated with increased reactive oxygen species (ROS) levels and decreased mitochondrial membrane potentials (MMP). In vivo, five weeks of doxorubicin treatment significantly decreased cardiac function, as evaluated by echocardiography. TUNEL staining results confirmed the increased apoptosis caused by doxorubicin. On the other hand, combinational treatment of doxorubicin with melatonin decreased cardiomyocyte ROS and apoptosis levels, along with increasing MMP. Such doxorubicin‐melatonin co‐treatment alleviated in vivo doxorubicin‐induced cardiac injury. Western Blots, along with in vitro immunofluorescence and in vivo immunohistochemical staining confirmed that doxorubicin treatment significantly down‐regulated Yes‐associated protein (YAP) expression, while YAP levels were maintained under co‐treatment of doxorubicin and melatonin. YAP inhibition by siRNA abolished the protective effects of melatonin on doxorubicin‐treated cardiomyocytes, with reversed ROS level and apoptosis. Our findings suggested that melatonin treatment attenuated doxorubicin‐induced cardiotoxicity through preserving YAP levels, which in turn decreases oxidative stress and apoptosis.

The role of melatonin on miRNAs modulation in triple-negative breast cancer cells

Melatonin, a hormone secreted by pineal gland, exerts antimetastatic effects by reducing tumor cell proliferation, migration and invasion. MicroRNAs (miRNAs) are small, non-coding RNAs that play a crucial role in regulation of gene expression and biological processes of the cells. Herein, we search for a link between the tumor/metastatic-suppressive actions of melatonin and miRNA expression in triple-negative breast cancer cells. We demonstrated that melatonin exerts its anti-tumor actions by reducing proliferation, migration and c-Myc expression of triple negative breast cancer cells. By using Taqman-based assays, we analyzed the expression levels of a set of miRNAs following melatonin treatment of triple negative breast cancer cells and we identified 17 differentially expressed miRNAs, 6 down-regulated and 11 up-regulated. We focused on the anti-metastatic miR-148b and the oncogenic miR-210 both up-regulated by melatonin treatment and studied the effect of their modulation on melatonin-mediated impairment of tumor progression. Surprisingly, when miR-148b or miR-210 were depleted in triple-negative breast cancer cells, using a specific miR-148b sponge or anti-miR-210, melatonin effects on migration inhibition and c-myc downregulation were still visible suggesting that the increase of miR-148b and miR-210 expression observed following melatonin treatment was not required for the efficacy of melatonin action. Nevertheless, ours results suggest that melatonin exhibit a compound for metastatic trait inhibition, especially in MDA-MB-231 breast cancer cells even if a direct link between modulation of expression of certain proteins or miRNAs and melatonin effects has still to be established.

Advances in Characterizing Recently-Identified Molecular Actions of Melatonin: Clinical Implications

Melatonin, N-acetyl-5-methoxy-tryptamine, was discovered to be a product of serotonin metabolism in the mammalian pineal gland where its synthesis is under control of the light:dark cycle. Besides its regulatory pathway involving ganglion cells in the retina, the neural connections between the eyes and the pineal gland include the master circadian clock, the suprachiasmatic nuclei, and the central and peripheral nervous systems. Since pineal melatonin is released into the blood and into the cerebrospinal fluid, it has access to every cell in an organism and it mediates system-wide effects. Subsequently, melatonin was found in several extrapineal organs and, more recently, perhaps in every cell of every organ. In contrast to the pinealocytes, non-pineal cells do not discharge melatonin into the blood; rather it is used locally in an intracrine, autocrine, or paracrine manner. Melatonin levels in non-pineal cells do not exhibit a circadian rhythm and do not depend on circulating melatonin concentrations although when animals are treated with exogenous melatonin it is taken up by presumably all cells. Mitochondria are the presumed site of melatonin synthesis in all cells; the enzymatic machinery for melatonin synthesis has been identified in mitochondria. The association of melatonin with mitochondria, because of its ability to inhibit oxidative stress, is very fortuitous since these organelles are a major site of damaging reactive oxygen species generation. In this review, some of the actions of non-pineal-derived melatonin are discussed in terms of cellular and subcellular physiology.

The effects of melatonin on signaling pathways and molecules involved in glioma

Glioblastoma is one of the most common brain tumors with high invasion and malignancy. Despite extensive research in this area and the use of new and advanced therapies, the survival rate in this disease is very low. In addition, resistance to treatment has also been observed in this disease. One of the reasons for rapid progression and failure in treatment for this disease is the presence of a class of cells with high proliferation and high differentiation, a class called glioblastoma stem-like cells shown as being the source of glioblastoma tumors. It has been reported that several oncogenes are expressed in this disease. One important issue in recognizing the pathogenesis of this disease, and which could improve the treatment process, is the identification of involved oncogenes as well as molecules that affect the reduction of the expression of these oncogenes. Melatonin regulates the biological rhythm and inhibits the proliferation of malignant glioma cells due to antioxidant and anti-apoptotic effects. Melatonin has been considered in biological processes and in signaling pathways involved in the development of glioma. The aim of this review is to investigate the effects of melatonin on signaling pathways and molecules involved in the progression of glioma.

Potential of Melatonin as Adjuvant Therapy of Oral Cancer in the Era of Epigenomics

The wide variety of epigenetic controls available is rapidly expanding the knowledge of molecular biology even overflowing it. At the same time, it can illuminate unsuspected ways of understanding the etiology of cancer. New emerging therapeutic horizons, then, promise to overcome the current antitumor strategies need. The translational utility of this complexity is particularly welcome in oral cancer (OC), in which natural history is alarmingly disappointing due to the invasive and mutilating surgery, the high relapsing rate, the poor quality of life and the reduced survival after diagnosis. Melatonin activates protective receptor-dependent and receptor-independent processes that prevent tissue cancerisation and inhibit progressive tumor malignancy and metastasis. Related evidence has shown that melatonin pleiotropy encompasses gene expression regulation through all the three best-characterized epigenetic mechanisms: DNA methylation, chromatin modification, and non-coding RNA. OC has received less attention than other cancers despite prognosis is usually negative and there are no significant therapy improvements recorded in the past decade. However, a large research effort is being carried out to elucidate how melatonin´s machinery can prevent epigenetic insults that lead to cancer. In the light of recent findings, a comprehensive examination of biochemistry through which melatonin may reverse epigenetic aberrations in OC is an extraordinary opportunity to take a step forward in the clinical management of patients.

Melatonin: An important anticancer agent in colorectal cancer

Colorectal cancer is one of the most common cancers among the elderly, which is also seen in the forms of hereditary syndromes occurring in younger individuals. Numerous studies have been conducted to understand the molecular and cellular pathobiology underlying colorectal cancer. These studies have found that cellular signaling pathways are at the core of colorectal cancer pathology. Because of this, new agents have been proposed as possible candidates to accompany routine therapy regimens. One of these agents is melatonin, a neuro-hormone known best for its essential role in upholding the circadian rhythm and orchestrating the many physiologic changes it accompanies. Melatonin is shown to be able to modulate many signaling pathways involved in many essential cell functions, which if deregulated cause an accelerated pace towards cancer. More so, melatonin is involved in the regulation of immune function, tumor microenvironment, and acts as an antioxidant agent. Many studies have focused on the beneficial effects of melatonin in colorectal cancers, such as induction of apoptosis, increased sensitivity to chemotherapy agents and radiotherapy, limiting cellular proliferation, migration, and invasion. The present review aims to illustrate the known significance of melatonin in colorectal cancer and to address possible clinical use.

Aging, Melatonin, and the Pro- and Anti-Inflammatory Networks

Aging and various age-related diseases are associated with reductions in melatonin secretion, proinflammatory changes in the immune system, a deteriorating circadian system, and reductions in sirtuin-1 (SIRT1) activity. In non-tumor cells, several effects of melatonin are abolished by inhibiting SIRT1, indicating mediation by SIRT1. Melatonin is, in addition to its circadian and antioxidant roles, an immune stimulatory agent. However, it can act as either a pro- or anti-inflammatory regulator in a context-dependent way. Melatonin can stimulate the release of proinflammatory cytokines and other mediators, but also, under different conditions, it can suppress inflammation-promoting processes such as NO release, activation of cyclooxygenase-2, inflammasome NLRP3, gasdermin D, toll-like receptor-4 and mTOR signaling, and cytokine release by SASP (senescence-associated secretory phenotype), and amyloid-β toxicity. It also activates processes in an anti-inflammatory network, in which SIRT1 activation, upregulation of Nrf2 and downregulation of NF-κB, and release of the anti-inflammatory cytokines IL-4 and IL-10 are involved. A perhaps crucial action may be the promotion of macrophage or microglia polarization in favor of the anti-inflammatory phenotype M2. In addition, many factors of the pro- and anti-inflammatory networks are subject to regulation by microRNAs that either target mRNAs of the respective factors or upregulate them by targeting mRNAs of their inhibitor proteins.

Melatonin treatment affects changes in adrenal gene expression of catecholamine biosynthesizing enzymes and norepinephrine transporter in the rat model of chronic-stress-induced depression

This study investigated the effects of melatonin treatment on adrenal catecholamine content, synthesis, uptake, and vesicular transport induced by the chronic unpredictable mild stress (CUMS) model of depression in rats. This entailed quantifying the norepinephrine, epinephrine, mRNA, and protein levels of tyrosine hydroxylase (TH), dopamine-β-hydroxylase (DBH), phenylethanolamine N-methyltransferase (PNMT), norepinephrine transporter (NET), and vesicular monoamine transporter 2 (VMAT2) in the adrenal medulla. CUMS caused a significant depletion of norepinephrine stores and protein levels of TH, DBH, and NET, whereas the gene expression of PNMT was increased. It was observed that melatonin treatment in the CUMS rats prevented the stress-induced decrease in norepinephrine content and the protein expression of TH, DBH, and NET in the adrenal medulla of chronically stressed rats. The present study demonstrates the stimulatory effect of melatonin on adrenomedullary synthesis, the uptake and content of catecholamine in the rat model of chronic stress-induced depression.

Overexpression of microRNA‑101 causes anti‑tumor effects by targeting CREB1 in colon cancer

Accumulating evidence has demonstrated that aberrantly expressed microRNAs (miRNAs) are involved in the initiation and progression of numerous types of human cancer. Although a number of miRNAs have been demonstrated to be associated with the diagnosis, progression and prognosis of colon cancer, the function of miRNA‑101 (miR‑101) in colon cancer remains unclear, and the molecular mechanisms underlying the effects of miR‑101 in colon cancer require further investigation. The present study investigated the role of miR‑101 in colon cancer, and the results suggested that miR‑101 expression levels were significantly decreased in colorectal carcinoma tissues and in three types of colorectal cancer cell lines. Furthermore, overexpression of miR‑101 inhibited cell proliferation and migration in HT29 cells. The transcription factor cAMP responsive element binding protein 1 (CREB1) was identified to be a direct target of miR‑101 using a luciferase reporter assay, reverse transcription‑quantitative polymerase chain reaction analysis and western blot assay. miR‑101 overexpression in tumor xenografts in vivo decreased the expression levels of proliferating cell nuclear antigen and CREB1, and suppressed tumor growth. The present results suggested that miR‑101 may serve a role in colon cancer by directly targeting CREB1. Collectively, the present study may contribute to the development of improved diagnosis and prognostics for colon cancer.

RNA-Seq transcriptome analysis shows anti-tumor actions of melatonin in a breast cancer xenograft model

Melatonin is a pleiotropic anti-cancer molecule that controls cancer growth by multiple mechanisms. RNA-Seq can potentially evaluate therapeutic response and its use in xenograft tumor models can differentiate the changes that occur specifically in tumor cells or in the tumor microenvironment (TME). Melatonin actions were evaluated in a xenograft model of triple-negative breast cancer. Balb/c nude mice bearing MDA-MB-231 tumors were treated with melatonin or vehicle. RNA-Seq was performed on the Illumina HiSeq. 2500 and data were mapped against human and mouse genomes separately to differentiate species-specific expression. Differentially expressed (DE) genes were identified and Weighted Gene Co-expression Network Analysis (WGCNA) was used to detect clusters of highly co-expressed genes. Melatonin treatment reduced tumor growth (p < 0.01). 57 DE genes were identified in murine cells, which represented the TME, and were mainly involved in immune response. The WGCNA detected co-expressed genes in tumor cells and TME, which were related to the immune system among other biological processes. The upregulation of two genes (Tnfaip8l2 and Il1f6) by melatonin was validated in the TME, these genes play important roles in the immune system. Taken together, the transcriptomic data suggests that melatonin anti-tumor actions occur through modulation of TME in this xenograft tumor model.

The Impact of miRNA in Colorectal Cancer Progression and Its Liver Metastases

Colorectal cancer (CRC) is one of the most commonly diagnosed malignancies with a high incidence and mortality rate. An essential challenge in colorectal cancer management is to identify new prognostic factors that could better estimate the evolution and treatment responses of this disease. Considering their role in cancer development, progression and metastasis, miRNAs have become an important class of molecules suitable for cancer biomarkers discovery. We performed a systematic search of studies investigating the role of miRNAs in colorectal progression and liver metastasis published until October 2018. In this review, we present up-to-date information regarding the specific microRNAs involved in CRC development, considering their roles in alteration of Wnt/βcatenin, EGFR, TGFβ and TP53 signaling pathways. We also emphasize the role of miRNAs in controlling the epithelial⁻mesenchymal transition of CRC cells, a process responsible for liver metastasis in a circulating tumor cell-dependent manner. Furthermore, we discuss the role of miRNAs transported by CRC-derived exosomes in mediating liver metastases, by preparing the secondary pre-metastatic niche and in inducing liver carcinogenesis in a Dicer-dependent manner.

Melatonin receptors: molecular pharmacology and signalling in the context of system bias

Melatonin, N-acetyl-5-methoxytryptamine, an evolutionally old molecule, is produced by the pineal gland in vertebrates, and it binds with high affinity to melatonin receptors, which are members of the GPCR family. Among the multiple effects attributed to melatonin, we will focus here on those that are dependent on the activation of the two mammalian MT1 and MT2 melatonin receptors. We briefly summarize the latest developments on synthetic melatonin receptor ligands, including multi-target-directed ligands, and the characterization of signalling-biased ligands. We discuss signalling pathways activated by melatonin receptors that appear to be highly cell- and tissue-dependent, emphasizing the impact of system bias on the functional outcome. Different proteins have been demonstrated to interact with melatonin receptors, and thus, we postulate that part of this system bias has its molecular basis in differences of the expression of receptor-associated proteins including heterodimerization partners. Finally, bias at the level of the receptor, by the expression of genetic receptor variants, will be discussed to show how a modified receptor function can have an effect on the risk for common diseases like type 2 diabetes in humans. LINKED ARTICLES: This article is part of a themed section on Recent Developments in Research of Melatonin and its Potential Therapeutic Applications. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.16/issuetoc.

Mechanisms Underlying Tumor Suppressive Properties of Melatonin

There is considerable evidence that melatonin may be of use in the prevention and treatment of cancer. This manuscript will review some of the human, animal and cellular studies that provide evidence that melatonin has oncostatic properties. Confirmation that melatonin mitigates pathogenesis of cancer will be described from both direct study of its effects on carcinogenesis, and from indirect findings implicating disruption of the circadian cycle. A distinction is made between the role of melatonin in preventing the initiation of the tumorigenic pathway and the ability of melatonin to retard the progression of cancer. Melatonin appears to slow down the rate of advancement of established tumors and there is evidence that it constitutes a valuable complement to standard pharmacological and radiation treatment modalities. There are instances of the beneficial outcomes in cancer treatment which utilize a range of hormones and vitamins, melatonin being among the constituents of the mix. While these complex blends are empirically promising, they are only briefly mentioned here in view of the confounding influence of a multiplicity of agents studied simultaneously. The last section of this review examines the molecular mechanisms that potentially underlie the oncostatic effects of melatonin. Alterations in gene expression following activation of various transcription factors, are likely to be an important mediating event. These changes in gene activity not only relate to cancer but also to the aging process which underlies the onset of most tumors. In addition, epigenetic events such as modulation of histone acetylation and DNA methylation patterns throughout the lifespan of organisms need to be considered. The antioxidant and immunoregulatory roles of melatonin may also contribute to its cancer modulatory properties. Naturally, these mechanisms overlap and interact extensively. Nevertheless, in the interest of clarity and ease of reading, each is discussed as a separate topic section. The report ends with some general conclusions concerning the clinical value of melatonin which has been rather overlooked and understudied.

Melatonin restrains angiogenic factors in triple-negative breast cancer by targeting miR-152-3p: In vivo and in vitro studies

AIMS

Breast cancer represents the second most prevalent tumor-related cause of death among women. Although studies have already been published regarding the association between breast tumors and miRNAs, this field remains unclear. MicroRNAs (miRNAs) are defined as non-coding RNA molecules, and are known to be involved in cell pathways through the regulation of gene expression. Melatonin can regulate miRNAs and genes related with angiogenesis. This hormone is produced naturally by the pineal gland and presents several antitumor effects. The aim of this study was to understand the action of melatonin in the regulation of miRNA-152-3p in vivo and in vitro.

MAIN METHODS

In order to standardize the melatonin treatment in the MDA-MB-468 cells, we carried out the cell viability assay at different concentrations. PCR Array plates were used to identify the differentiated expression of miRNAs after the treatment with melatonin. The relative quantification of the target gene expression (IGF-IR, HIF-1α and VEGF) was performed by real-time PCR. For the tumor development, MDA-MB-468 cells were implanted in female BALB/c mice, and treated or not treated with melatonin. Moreover, the quantification of the target genes protein expression was performed by immunocytochemistry and immunohistochemistry.

KEY FINDINGS

Relative quantification shows that the melatonin treatment increases the gene expression of miR-152-3p and the target genes, and decreased protein levels of the genes both in vitro and in vivo.

SIGNIFICANCE

Our results confirm the action of melatonin on the miR-152-3p regulation known to be involved in the progression of breast cancer.

Functional Interaction between Melatonin Signaling and Noncoding RNAs

Melatonin was discovered in the pineal gland and first came to be known as a biochemical synchronizer of circadian rhythm. The molecular mechanisms underlying the broad-spectrum actions of melatonin are not restricted to its interaction with proteins but it also has functional effects after influencing RNA species that have no protein-coding potential. In this review we discuss the current understanding of the melatonin-mediated modulation of noncoding RNA (ncRNA) pathways under different physiological and pathological conditions. We also delineate the impact of specific ncRNAs in controlling the synthesis of melatonin. The information compiled herein will serve as a solid foundation to formulate ideas for future mechanistic studies on melatonin and to better explore the emerging functions of the noncoding transcriptome.

Melatonin for the prevention and treatment of cancer

The epidemiological studies have indicated a possible oncostatic property of melatonin on different types of tumors. Besides, experimental studies have documented that melatonin could exert growth inhibition on some human tumor cells in vitro and in animal models. The underlying mechanisms include antioxidant activity, modulation of melatonin receptors MT1 and MT2, stimulation of apoptosis, regulation of pro-survival signaling and tumor metabolism, inhibition on angiogenesis, metastasis, and induction of epigenetic alteration. Melatonin could also be utilized as adjuvant of cancer therapies, through reinforcing the therapeutic effects and reducing the side effects of chemotherapies or radiation. Melatonin could be an excellent candidate for the prevention and treatment of several cancers, such as breast cancer, prostate cancer, gastric cancer and colorectal cancer. This review summarized the anticancer efficacy of melatonin, based on the results of epidemiological,experimental and clinical studies, and special attention was paid to the mechanisms of action.

Melatonin Inhibits the Proliferation of Gastric Cancer Cells Through Regulating the miR-16-5p-Smad3 Pathway

The incidence and mortality of gastric cancer is steadily increasing annually around the world, which required further investigation about alternative therapy strategies. Melatonin, an indoleamine synthesized in the pineal gland, has shown dramatic anticancer effect in several cancers, however, the function of melatonin in gastric cancer needs to be characterized. In this study, we found that melatonin inhibited the growth and induced apoptosis of gastric cancer cells. microRNAs (miRNAs) have been attractive targets for many anticancer drugs. To explore the underlying molecular mechanism by which melatonin attenuated the growth of cancer cells, miRNA microarray analysis was performed to screen the miRNAs, which significantly altered after melatonin treatment. The result showed that melatonin administration enhanced the expression of miR-16-5p. Further molecular mechanism research revealed that miR-16-5p targeted Smad3 and consequently negatively regulated the abundance of Smad3. Consistently, melatonin exposure decreased the level of Smad3 and overexpression of Smad3 attenuated the inhibitory effect of melatonin in gastric cancer cells. These results uncovered the anticancer effect of melatonin and highlighted the critical roles of miR-16-5p-Smad3 pathway in melatonin-induced growth defects of gastric cancers.

Friend or Foe: MicroRNAs in the p53 network

The critical tumor suppressor gene TP53 is either lost or mutated in more than half of human cancers. As an important transcriptional regulator, p53 modulates the expression of many microRNAs. While wild-type p53 uses microRNAs to suppress cancer development, microRNAs that are activated by gain-of-function mutant p53 confer oncogenic properties. On the other hand, the expression of p53 is tightly controlled by a fine-tune machinery including microRNAs. MicroRNAs can target the TP53 gene directly or other factors in the p53 network so that expression and function of either the wild-type or the mutant forms of p53 is downregulated. Therefore, depending on the wild-type or mutant p53 context, microRNAs contribute substantially to suppress or exacerbate tumor development.

MicroRNA-23a/24-2/27a as a potential diagnostic biomarker for cancer: A systematic review and meta-analysis

An increasing number of studies have proven that microRNAs play an important role in the occurrence, development and prognosis of various types of cancer. As a vital gene cluster, the microRNA (miR)-23a/24-2/27a cluster may be an important marker for predicting cancer prognosis and tumor progression. A search was conducted through PubMed, Medline and the Cochrane Library to identify studies investigating the association between the miR-23a/24-2/27a cluster and cancer, and the identified related studies were included in the present meta-analysis. The strength of the association was assessed by hazard ratio (HR) and its 95% confidence interval (95% CI). A total of 21 studies were included in this meta-analysis. The results indicated that a high level of miR-23a exerted a significant effect on overall survival (OS) (HR=2.33, 95% CI: 1.18-4.58; P=0.014), but not on disease-free survival (DFS)/recurrence-free survival (RFS) (HR=1.13, 95% CI: 0.37-3.44; P=0.836). There was an obvious statistically significant association between OS and the expression of miR-24 (HR=2.49, 95% CI: 1.84-3.37; P=0.000), particularly in the digestive system (pooled HR=2.99, 95% CI: 2.17-4.13, P=0.000). In addition, the result suggested a statistically significant association between the expression of miR-27a and OS (pooled HR=1.89, 95% CI: 1.32-2.69; P=0.001), as well as DFS/RFS/progression-free survival (HR=2.19, 95% CI: 1.29-3.70; P=0.003), particularly in renal cell carcinoma (HR=2.30, 95% CI: 1.16-4.67; P=0.017). A subgroup analysis by ethnicity, cancer type and statistical methodology was performed. There was no obvious publication bias. In conclusion, the present study demonstrated that the miR-23a/24-2/27a cluster may be a useful marker for predicting cancer prognosis and tumor progression.

Melatonin as a promising agent to treat ovarian cancer: molecular mechanisms

Ovarian cancer (OC) has the highest mortality rate of all gynecological cancers, and most patients develop chemoresistance after first-line treatments. Despite recent advances, the 5-year relative survival is ~45% for all OC subtypes, and invasive epithelial OC has only a 17% survival rate when diagnosed at a late stage. Identification of new efficacious molecules or biomarkers represents important opportunities in the treatment of OC. The pharmacological and physiological properties of melatonin indicate this agent could be useful against OC progression and metastasis. In normal cells, melatonin has potent antioxidant and anti-apoptotic actions. Conversely, melatonin has pro-oxidant as well as anti-proliferative, anti-angiogenic and immunomodulatory properties in many cancer types including hormone-dependent cancers. Although melatonin receptors have been identified in OC cells, the exact mechanism by which melatonin induces anticancer activities remains incompletely understood. Clinical studies have reported negative correlation between aggressiveness of OC and serum levels of melatonin, reinforcing the idea that melatonin may be a critical factor determining OC development. In vitro and in vivo studies suggest melatonin differentially regulates multiple signaling pathways in OC cells. This focused review explores the potential mechanisms of action of melatonin on cultured OC cells and in experimental models of OC in an attempt to clarify how melatonin modulates the signaling pathways involved in cancer cell apoptosis, survival, inflammation, proliferation and metabolic processes. Based on the evidence presented, we feel that melatonin, as an agent that controls cellular signals associated with malignancy, may be beneficial in combination with other therapeutics for OC treatment.

Melatonin and Hippo Pathway: Is There Existing Cross-Talk?

Melatonin is an indolic hormone that regulates a plethora of functions ranging from the regulation of circadian rhythms and antioxidant properties to the induction and maintenance of tumor suppressor pathways. It binds to specific receptors as well as to some cytosolic proteins, leading to several cellular signaling cascades. Recently, the involvement of melatonin in cancer insurgence and progression has clearly been demonstrated. In this review, we will first describe the structure and functions of melatonin and its receptors, and then discuss both molecular and epidemiological evidence on melatonin anticancer effects. Finally, we will shed light on potential cross-talk between melatonin signaling and the Hippo signaling pathway, along with the possible implications for cancer therapy.

Melatonin as a potential inhibitory agent in head and neck cancer

Melatonin is a molecule secreted by the pineal gland; it is an important regulator of sleep and circadian rhythms. Through multiple interrelated mechanisms, melatonin exhibits various inhibitory properties at different stages of tumor progression. Many studies have explored the oncostatic effects of melatonin on hormone-dependent tumors. In this review, we highlight recent advances in understanding the effects of melatonin on the development of head and neck cancers, including molecular mechanisms identified through experimental and clinical observations. Because melatonin exerts a wide range of effects, melatonin may influence many mechanisms that influence the development of cancer. These include cell proliferation, apoptosis, angiogenesis, extracellular matrix remodeling through matrix metalloproteinases, and genetic polymorphism. Thus, the evidence discussed in this article will serve as a basis for basic and clinical research to promote the use of melatonin for understanding and controlling the development of head and neck cancers.

A Review of the Scaffold Protein Menin and its Role in Hepatobiliary Pathology

Multiple endocrine neoplasia type 1 (MEN1) is a familial cancer syndrome with neuroendocrine tumorigenesis of the parathyroid glands, pituitary gland, and pancreatic islet cells. The MEN1 gene codes for the canonical tumor suppressor protein, menin. Its protein structure has recently been crystallized, and it has been investigated in a multitude of other tissues. In this review, we summarize recent advancements in understanding the structure of the menin protein and its function as a scaffold protein in histone modification and epigenetic gene regulation. Furthermore, we explore its role in hepatobiliary autoimmune diseases, cancers, and metabolic diseases. In particular, we discuss how menin expression and function are regulated by extracellular signaling factors and nuclear receptor activation in various hepatic cell types. How the many signaling pathways and tissue types affect menin's diverse functions is not fully understood. We show that small-molecule inhibitors affecting menin function can shed light on menin's broad role in pathophysiology and elucidate distinct menin-dependent processes. This review reveals menin's often dichotomous function through analysis of its role in multiple disease processes and could potentially lead to novel small-molecule therapies in the treatment of cholangiocarcinoma or biliary autoimmune diseases.

Upregulation of miR-101 enhances the cytotoxic effect of anticancer drugs through inhibition of colon cancer cell proliferation

This study investigated the effect of miR-101 on proliferation, migration, invasion, and chemotherapy sensitivity in colon cancer cell lines HT-29 and RKO. MicroRNAs are a class of small noncoding RNA molecules, which play important roles in diverse biological processes of human cancers, such as carcinogenesis, development, differentiation, and apoptosis. The expression of miR-101 in colon cancer and adjacent non-tumor tissues were examined by quantitative real-time polymerase chain reaction. The expression of miR-101 was upregulated by recombinant adenovirus Ad-miR-101. Cell proliferation was detected by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and cloning methods. Cell migration and invasion potential were examined using Transwell migration and Matrigel invasion chamber assays. Drug sensitivity to 5-fluorouracil (5-FU) and cisplatin (DDP) was explored using MTT assays and l acridine orange/ethidium bromide double staining. The expression of miR-101 decreased in colon cancer tissues compared with adjacent non-tumor tissues. The upregulated expression of miR-101 suppressed cell proliferation and inhibited cell migration and invasion in HT-29 and RKO colon cancer cell lines. The overexpression of miR-101 promoted the inhibitory effect of 5-FU and DDP on HT-29 cells. The expression of miR-101 was downregulated in colon cancer. The upregulated expression of miR-101 inhibited proliferation and migration, and increased the sensitivity of colon cancer cells to chemotherapy.

MicroRNAs as Key Effectors in the p53 Network

The guardian of the genome p53 is embedded in a fine-spun network of MicroRNAs. p53 is able to activate or repress directly the transcription of MicroRNAs that are participating in the tumor-suppressive mission of p53. On the other hand, the expression of p53 is under tight control of MicroRNAs that are either targeting directly p53 or factors that are modifying its protein level or activity. Although the most important function of p53 is suggested to be transcriptional regulation, there are several nontranscriptional functions described. One of those regards the modulation of MicroRNA biogenesis. Wild-type p53 is increasing the maturation of selected MicroRNAs from the primary transcript to the precursor MiRNA by interacting with the Microprocessor complex. Furthermore, p53 is modulating the mRNA accessibility for certain MicroRNAs by association with the RISC complex and transcriptional regulation of RNA-binding proteins. In this way p53 is able to remodel the MiRNA-mRNA interaction network. As wild-type p53 is employing MicroRNAs to suppress cancer development, gain-of-function mutant p53 proteins use MicroRNAs to confer oncogenic properties like chemoresistance and the ability to drive metastasis. Like its wild-type counterpart mutant p53 is able to regulate MicroRNAs transcriptionally and posttranscriptionally. Mutant p53 affects the MiRNA processing at two cleavage steps through interfering with the Microprocessor complex and by downregulating Dicer and KSRP, a modulator of MiRNA biogenesis. Thus, MicroRNAs are essential components in the p53 pathway, contributing substantially to combat or enhance tumor development depending on the wild-type or mutant p53 context.

miR-24 Inhibition Increases Menin Expression and Decreases Cholangiocarcinoma Proliferation

Menin (MEN1) is a tumor-suppressor protein in neuroendocrine tissue. Therefore, we tested the novel hypothesis that menin regulates cholangiocarcinoma proliferation. Menin and miR-24 expression levels were measured in the following intrahepatic and extrahepatic cholangiocarcinoma (CCA) cell lines, Mz-ChA-1, TFK-1, SG231, CCLP, HuCCT-1, and HuH-28, as well as the nonmalignant human intrahepatic biliary line, H69. miR-24 miRNA and menin protein levels were manipulated in vitro in Mz-ChA-1 cell lines. Markers of proliferation and angiogenesis (Ki-67, vascular endothelial growth factors A/C, vascular endothelial growth factor receptors 2/3, angiopoietin 1/2, and angiopoietin receptors 1/2) were evaluated. Mz-ChA-1 cells were injected into the flanks of nude mice and treated with miR-24 inhibitor or inhibitor scramble. Menin expression was decreased in advanced CCA specimens, whereas miR-24 expression was increased in CCA. Menin overexpression decreased proliferation, angiogenesis, migration, and invasion. Inhibition of miR-24 increased menin protein expression while decreasing proliferation, angiogenesis, migration, and invasion. miR-24 was shown to negatively regulate menin expression by luciferase assay. Tumor burden and expression of proliferative and angiogenic markers was decreased in the miR-24 inhibited tumor group compared to controls. Interestingly, treated tumors were more fibrotic than the control group. miR-24-dependent expression of menin may be important in the regulation of nonmalignant and CCA proliferation and may be an additional therapeutic tool for managing CCA progression.

Elevated expression of miR-24-3p is a potentially adverse prognostic factor in colorectal adenocarcinoma

OBJECTIVES

Several miRNAs are aberrantly expressed in cancer. miR-24-3p is involved in cancer-related cellular processes, including cell cycle control, cell growth, proliferation, and apoptosis. In this study, we examined the potential diagnostic and prognostic significance of miR-24-3p expression in colorectal adenocarcinoma.

DESIGN AND METHODS

Total RNA was isolated from 182 colorectal adenocarcinoma specimens and 86 paired non-cancerous colorectal mucosae. After polyadenylation of 2μg total RNA and reverse transcription into first-strand cDNA using an oligo-dT-adapter primer, miR-24-3p expression was quantified using an in-house-developed reverse-transcription real-time quantitative PCR method, based on the SYBR Green chemistry. SNORD43 (RNU43) was used as a reference gene.

RESULTS

miR-24-3p levels do not significantly differ between colorectal adenocarcinoma and non-cancerous colorectal mucosae. Thus, miR-24-3p expression cannot be used for diagnostic purposes. However, high miR-24-3p expression predicts poor disease-free survival (DFS) and overall survival (OS) of colorectal adenocarcinoma patients. Multivariate Cox regression analysis confirmed that miR-24-3p overexpression is a significant predictor of relapse in colorectal adenocarcinoma and that its prognostic significance is independent of other established prognostic factors and treatment of patients. Of note, miR-24-3p overexpression retains its rather unfavorable prognostic value in the subgroup of patients with advanced yet locally restricted colorectal adenocarcinoma (T3) and in those without distant metastasis (M0). Moreover, miR-24-3p overexpression is a potentially unfavorable prognosticator for patients who were not treated with radiotherapy.

CONCLUSIONS

Strong expression of miR-24-3p predicts poor DFS and OS of colorectal adenocarcinoma patients, independently of clinicopathological parameters that are currently used for prognosis in this human malignancy.