Anti-oncogenic microRNA-203 induces senescence by targeting E2F3 protein in human melanoma cells

Extracellular Vesicles Derived from Acidified Metastatic Melanoma Cells Stimulate Growth, Migration, and Stemness of Normal Keratinocytes

Metastatic melanoma is a highly malignant tumor. Melanoma cells release extracellular vesicles (EVs), which contribute to the growth, metastasis, and malignancy of neighboring cells by transfer of tumor-promoting miRNAs, mRNA, and proteins. Melanoma microenvironment acidification promotes tumor progression and determines EVs’ properties. We studied the influence of EVs derived from metastatic melanoma cells cultivated at acidic (6.5) and normal (7.4) pH on the morphology and homeostasis of normal keratinocytes. Acidification of metastatic melanoma environment made EVs more prooncogenic with increased expression of prooncogenic mi221 RNA, stemless factor CD133, and pro-migration factor SNAI1, as well as with downregulated antitumor mir7 RNA. Incubation with EVs stimulated growth and migration both of metastatic melanoma cells and keratinocytes and changed the morphology of keratinocytes to stem-like phenotype, which was confirmed by increased expression of the stemness factors KLF and CD133. Activation of the AKT/mTOR and ERK signaling pathways and increased expression of epidermal growth factor receptor EGFR and SNAI1 were detected in keratinocytes upon incubation with EVs. Moreover, EVs reduced the production of different cytokines (IL6, IL10, and IL12) and adhesion factors (sICAM-1, sICAM-3, sPecam-1, and sCD40L) usually secreted by keratinocytes to control melanoma progression. Bioinformatic analysis revealed the correlation between decreased expression of these secreted factors and worse survival prognosis for patients with metastatic melanoma. Altogether, our data mean that metastatic melanoma EVs are important players in the transformation of normal keratinocytes.

Comprehensive miRNA and DNA Microarray Analyses Reveal the Response of Hepatic miR-203 and Its Target Gene to Protein Malnutrition in Rats

Adequate protein nutrition is essential for good health. Effects of protein malnutrition in animals have been widely studied at the mRNA level with the development of DNA microarray technology. Although microRNAs (miRNAs) have attracted attention for their function in regulating gene expression and have been studied in several disciplines, fewer studies have clarified the effects of protein malnutrition on miRNA alterations. The present study aimed to elucidate the relationship between protein malnutrition and miRNAs. Six-week old Wistar male rats were fed a control diet (20% casein) or a low-protein diet (5% casein) for two weeks, and their livers were subjected to both DNA microarray and miRNA array analysis. miR-203 was downregulated and its putative target Hadhb (hydroxyacyl-CoA dehydrogenase β subunit), known to regulate β-oxidation of fatty acids, was upregulated by the low-protein diet. In an in vitro experiment, miR-203 or its inhibitor were transfected in HepG2 cells, and the pattern of Hadhb expression was opposite to that of miR-203 expression. In addition, to clarifying the hepatic miRNA profile in response to protein malnutrition, these results showed that a low-protein diet increased Hadhb expression through downregulation of miR-203 and induced β-oxidation of fatty acids.

Predicting the possible effect of miR-203a-3p and miR-29a-3p on DNMT3B and GAS7 genes expression

Aberrant expression of genes involved in methylation, including DNA methyltransferase 3 Beta (DNMT3B), can cause hypermethylation of various tumor suppressor genes. In this regard, various molecular factors such as microRNAs can play a critical role in regulating these methyltransferase enzymes and eventually downstream genes such as growth arrest specific 7 (GAS7). Accordingly, in the present study we aimed to predict regulatory effect of miRNAs on DNMT3B and GAS7 genes expression in melanoma cell line. hsa-miR-203a-3p and hsa-miR-29a-3p were predicted and selected using bioinformatics software. The Real-time PCR technique was performed to investigate the regulatory effect of these molecules on the DNMT3B and GAS7 genes expression. Expression analysis of DNMT3B gene in A375 cell line showed that there was a significant increase compared to control (p value = 0.0015). Analysis of hsa-miR-203a-3p and hsa-miR-29a-3p indicated the insignificant decreased expression in melanoma cell line compared to control (p value < 0.05). Compared to control, the expression of GAS7 gene in melanoma cells showed a significant decrease (p value = 0.0323). Finally, our findings showed that the decreased expression of hsa-miR-203a-3p and hsa-miR-29a-3p can hypothesize that their aberrant expression caused DNMT3B dysfunction, possible methylation of the GAS7 gene, and ultimately decreased its expression. However, complementary studies are necessary to definite comment.

A Comparative View on Molecular Alterations and Potential Therapeutic Strategies for Canine Oral Melanoma

Canine oral melanoma (COM) is a highly aggressive tumour associated with poor prognosis due to metastasis and resistance to conventional anti-cancer therapies. As with human mucosal melanoma, the mutational landscape is predominated by copy number aberrations and chromosomal structural variants, but differences in study cohorts and/or tumour heterogeneity can lead to discordant results regarding the nature of specific genes affected. This review discusses somatic molecular alterations in COM that result from single nucleotide variations, copy number changes, chromosomal rearrangements, and/or dysregulation of small non-coding RNAs. A cross-species comparison highlights notable recurrent aberrations, and functionally grouping dysregulated proteins reveals unifying biological pathways that may be critical for oncogenesis and metastasis. Finally, potential therapeutic strategies are considered to target these pathways in canine patients, and the benefits of collaboration between science, medical, and veterinary communities are emphasised.

MicroRNA Isoforms Contribution to Melanoma Pathogenesis

Cutaneous melanoma (CM) is the most lethal tumor among skin cancers, and its incidence is constantly increasing. A deeper understanding of the molecular processes guiding melanoma pathogenesis could improve diagnosis, treatment and prognosis. MicroRNAs play a key role in melanoma biology. Recently, next generation sequencing (NGS) experiments, designed to assess small-RNA expression, revealed the existence of microRNA variants with different length and sequence. These microRNA isoforms are known as isomiRs and provide an additional layer to the complex non-coding RNA world. Here, we collected data from NGS experiments to provide a comprehensive characterization of miRNA and isomiR dysregulation in benign nevi (BN) and early-stage melanomas. We observed that melanoma and BN express different and specific isomiRs and have a different isomiR abundance distribution. Moreover, isomiRs from the same microRNA can have opposite expression trends between groups. Using The Cancer Genome Atlas (TCGA) dataset of skin cancers, we analyzed isomiR expression in primary melanoma and melanoma metastasis and tested their association with NF1, BRAF and NRAS mutations. IsomiRs differentially expressed were identified and catalogued with reference to the canonical form. The reported non-random dysregulation of specific isomiRs contributes to the understanding of the complex melanoma pathogenesis and serves as the basis for further functional studies.

The Paradoxical Role of Cellular Senescence in Cancer

Cellular senescence occurs in proliferating cells as a consequence of various triggers including telomere shortening, DNA damage, and inappropriate expression of oncogenes. The senescent state is accompanied by failure to reenter the cell cycle under mitotic stimulation, resistance to cell death and enhanced secretory phenotype. A growing number of studies have convincingly demonstrated a paradoxical role for spontaneous senescence and therapy-induced senescence (TIS), that senescence may involve both cancer prevention and cancer aggressiveness. Cellular senescence was initially described as a physiological suppressor mechanism of tumor cells, because cancer development requires cell proliferation. However, there is growing evidence that senescent cells may contribute to oncogenesis, partly in a senescence-associated secretory phenotype (SASP)-dependent manner. On the one hand, SASP prevents cell division and promotes immune clearance of damaged cells, thereby avoiding tumor development. On the other hand, SASP contributes to tumor progression and relapse through creating an immunosuppressive environment. In this review, we performed a review to summarize both bright and dark sides of senescence in cancer, and the strategies to handle senescence in cancer therapy were also discussed.

MicroRNA Signature in Melanoma: Biomarkers and Therapeutic Targets

Melanoma is the utmost fatal kind of skin neoplasms. Molecular changes occurring during the pathogenic processes of initiation and progression of melanoma are diverse and include activating mutations in BRAF and NRAS genes, hyper-activation of PI3K/AKT pathway, inactivation of p53 and alterations in CDK4/CDKN2A axis. Moreover, several miRNAs have been identified to be implicated in the biology of melanoma through modulation of expression of genes being involved in these pathways. In the current review, we provide a summary of the bulk of information about the role of miRNAs in the pathobiology of melanoma, their possible application as biomarkers and their emerging role as therapeutic targets for this kind of skin cancer.

miRNA and mRNA expression profiling reveals potential biomarkers for metastatic cutaneous melanoma

Purpose: This study aims to uncover potential biomarkers associated with cutaneous melanoma (CM) metastasis.Methods: The mRNA and microRNA (miRNA) expression data from the metastatic CM and non-metastatic CM population were obtained from The Cancer Genome Atlas database. Functional analysis, protein-protein interaction (PPI), and survival analysis were performed for differentially expressed mRNAs (DEmRNAs) and miRNAs (DEmiRNAs). The interaction between DEmRNAs and DEmiRNAs was analyzed. The expression of several key DEmRNAs and DEmiRNAs was validated by Gene Expression Omnibus datasets.Results: Overall, 1172 DEmRNAs and 26 DEmiRNAs were identified from metastatic and non-metastatic CM. Cytokine-cytokine receptor interaction and chemokine signaling pathway were key pathways. CXCR1, CXCR2, CXCR4, CCR1, CCR2, and CCR5 were hub genes in the PPI network. Among these, miR-29 c-3p, miR-100-5p, miR-150-5p, and miR-150-3p were not only diagnostic biomarkers but also related to survival time. miR-203a-3p interacted with CCR5 and LIFR, while miR-224-5p was strongly associated with CXCR4. LIFR, CXCR1, CXCR2, CXCR4, CCR1, CCR2, and CCR5 were enriched in the cytokine-cytokine receptor interaction pathway. The levels of seven DEmRNAs (CXCR1, CXCR2, CXCR4, CCR1, CCR2, CCR5, and LIFR) and two DEmiRNAs (miR-203a-3p and miR-224-5p) were validated using the GSE65568 and GSE109244 datasets, respectively.Conclusion: Our findings may provide novel biomarkers for CM metastasis.[Formula: see text].

Reciprocal Changes in miRNA Expression with Pigmentation and Decreased Proliferation Induced in Mouse B16F1 Melanoma Cells by L-Tyrosine and 5-Bromo-2'-Deoxyuridine

Background: Many microRNAs have been identified as critical mediators in the progression of melanoma through its regulation of genes involved in different cellular processes such as melanogenesis, cell cycle control, and senescence. However, microRNAs’ concurrent participation in syngeneic mouse B16F1 melanoma cells simultaneously induced decreased proliferation and differential pigmentation by exposure to 5-Brd-2′-dU (5’Bromo-2-deoxyuridine) and L-Tyr (L-Tyrosine) respectively, is poorly understood. Aim: To evaluate changes in the expression of microRNAs and identify which miRNAs in-network may contribute to the functional bases of phenotypes of differential pigmentation and reduction of proliferation in B16F1 melanoma cells exposed to 5-Brd-2′-dU and L-Tyr. Methods: Small RNAseq evaluation of the expression profiles of miRNAs in B16F1 melanoma cells exposed to 5-Brd-2′-dU (2.5 μg/mL) and L-Tyr (5 mM), as well as the expression by qRT-PCR of some molecular targets related to melanogenesis, cell cycle, and senescence. By bioinformatic analysis, we constructed network models of regulation and co-expression of microRNAs. Results: We confirmed that stimulation or repression of melanogenesis with L-Tyr or 5-Brd-2′-dU, respectively, generated changes in melanin concentration, reduction in proliferation, and changes in expression of microRNAs 470-3p, 470-5p, 30d-5p, 129-5p, 148b-3p, 27b-3p, and 211-5p, which presented patterns of coordinated and reciprocal co-expression, related to changes in melanogenesis through their putative targets Mitf, Tyr and Tyrp1, and control of cell cycle and senescence: Cyclin D1, Cdk2, Cdk4, p21, and p27. Conclusions: These findings provide insights into the molecular biology of melanoma of the way miRNAs are coordinated and reciprocal expression that may operate in a network as molecular bases for understanding changes in pigmentation and decreased proliferation induced in B16F1 melanoma cells exposed to L-Tyr and 5-Brd-2′-dU.

MicroRNAs are critical regulators of senescence and aging in mesenchymal stem cells

MicroRNAs (miRNAs) have recently come under scrutiny for their role in various age-related diseases. Similarly, cellular senescence has been linked to disease and aging. MicroRNAs and senescence likely play an intertwined role in driving these pathologic states. In this review, we present the connection between these two drivers of age-related disease concerning mesenchymal stem cells (MSCs). First, we summarize key miRNAs that are differentially expressed in MSCs and other musculoskeletal lineage cells during senescence and aging. Additionally, we also reviewed miRNAs that are regulated via traditional senescence-associated secretory phenotype (SASP) cytokines in MSC. Lastly, we summarize miRNAs that have been found to target components of the cell cycle arrest pathways inherently activated in senescence. This review attempts to highlight potential miRNA targets for regenerative medicine applications in age-related musculoskeletal disease.

Epigenetic Mechanisms in Canine Cancer

A plethora of data has highlighted the role of epigenetics in the development of cancer. Initiation and progression of different cancer types are associated with a variety of changes of epigenetic mechanisms, including aberrant DNA methylation, histone modifications, and miRNA expression. At the same time, advances in the available epigenetic tools allow to investigate and reverse these epigenetic changes and form the basis for the development of anticancer drugs in human oncology. Although human and canine cancer shares several common features, only recently that studies emerged investigating the epigenetic landscape in canine cancer and applying epigenetic modulators to canine cancer. This review focuses on the existing studies involving epigenetic changes in different types of canine cancer and the use of small-molecule inhibitors in canine cancer cells.

Protoflavones in melanoma therapy: Prooxidant and pro-senescence effect of protoapigenone and its synthetic alkyl derivative in A375 cells

AIMS

In our study, the anticancer effects of a semisynthetic p-quinol, protoapigenone 1'-O-butyl ether (PABut), were tested in human melanoma A375 cells also in comparison with natural congener, protoapigenone (PA).

MAIN METHODS

The cytotoxic effect of PABut and PA was determined using MTT assay. Flow cytometry analysis was used to evaluate the influence of the compounds tested on ROS generation and cell cycle distribution in A375 cells. Moreover, apoptosis was evaluated by AO/EB dual staining as well as by flow cytometry. Markers of senescence were quantified by spectrofluorimetry and by Western blot analysis.

KEY FINDINGS

Both PABut and PA showed significant cytotoxicity against melanoma A375 cells at sub-micromolar concentrations. Both protoflavones induced comparable cell cycle arrest in G2/M phase. However, a more profound upregulation of intracellular ROS levels was found following PABut treatment. An increased apoptosis in the cells following 48 h treatment with both protoflavones tested was also confirmed. Both compounds tested remarkably upregulated p21 protein levels in A375 cells. Unlike PA, PABut significantly decreased protein levels of NAD⁺-dependent deacetylase SirT1 and β-actin accompanied by mild significant upregulation of mitochondrial SOD2 and senescence markers, p16 protein and SA-β-Gal activity. However, a significant upregulation of p53 only following PA treatment was found.

SIGNIFICANCE

These results suggest that PABut and PA confer high chemotherapeutic potential in melanoma cells and are suitable for further testing. Furthermore, modification of protoapigenone with 1'-O-butyl ether moiety can be associated with improved senescence-inducing effect and, thus, enhanced chemotherapeutic potency of PABut compared to the unmodified natural protoflavone.

A novel LncRNA transcript, RBAT1, accelerates tumorigenesis through interacting with HNRNPL and cis-activating E2F3

BACKGROUND

Long non-coding RNAs (lncRNAs) have been identified as important epigenetic regulators that play critical roles in human cancers. However, the regulatory functions of lncRNAs in tumorigenesis remains to be elucidated. Here, we aimed to investigate the molecular mechanisms and potential clinical application of a novel lncRNA, retinoblastoma associated transcript-1 (RBAT1), in tumorigenesis.

METHODS

RBAT1 expression was determined by real-time PCR in both retinoblastoma (Rb) and bladder cancer (BCa) cell lines and clinical tissues. Chromatin isolation using RNA purification (ChIRP) assays were performed to identify RBAT1-interacting proteins. Patient-derived xenograft (PDX) retinoblastoma models were established to test the therapeutic potential of RBAT1-targeting GapmeRs.

RESULTS

Here, we found that RBAT1 expression was significantly higher in Rb and BCa tissues than that in adjacent tissues. Functional assays revealed that RBAT1 accelerated tumorigenesis both in vitro and in vivo. Mechanistically, RBAT1 recruited HNRNPL protein to E2F3 promoter, thereby activating E2F3 transcription. Therapeutically, GapmeR-mediated RBAT1 silencing significantly inhibited tumorigenesis in orthotopic xenograft retinoblastoma models derived from Rb cell lines and Rb primary cells.

CONCLUSIONS

RBAT1 overexpression upregulates a known oncogene, E2F3, via directly recruiting HNPNPL to its promoter and cis-activating its expression. Our finding provides a novel mechanism of lncRNA biology and provides potential targets for diagnosis and treatment of Rb and BCa.

Expression of miR-34a in cataract rats and its related mechanism

Expression of miR-34a in cataract rats and its related mechanism were investigated. A total of 30 SD rats were selected and divided into three groups: group A: 2-month-old lucent lens, group B: 18-month-old lucent lens, and group C: 18-month-old naturally occurring cataract lens. The lens was taken and measured by LOC III to determine the degree of lens opacity of the three groups of rats. qPCR was used to detect expression of miR-34a and mRNA of SIRT1 and P53. Western blotting was used to detect the protein expression of SIRT1 and P53. Cell apoptosis was detected by flow cytometry. The lens of rats in group C was more turbid than that of groups A and B (P<0.05). The expression levels of miR-34a and P53 mRNA in the rats lens of group C were significantly higher than those in groups A and B, and the expression of SIRT1 mRNA was significantly lower than that of groups A and group B (P<0.05). Expression of miR-34a in group A was significantly higher than that in group B, the mRNA expression of SIRT1 was significantly lower than that in the lucent lens of 18-month-old rats (P<0.05). The expression of SIRT1 protein in group C was significantly lower than that in groups A and group B, while the expression level of P53 protein in group C was significantly higher than that of groups A and B. The expression of SIRT1 protein in group B was significantly higher than that in group A (P<0.05). The apoptosis rate of group C was higher than that of groups A and group B (P<0.05). In conclusion, the upregulation of expression level of miR-34a is related to cataract occurrence in rats, which may be caused by regulation of SIRT1 protein.

The Role of Non-Coding RNAs Involved in Nickel-Induced Lung Carcinogenic Mechanisms

Nickel is a naturally occurring element found in the Earth’s crust and an International Agency for Research on Cancer (IARC)-classified human carcinogen. While low levels found in the natural environment pose a minor concern, the extensive use of nickel in industrial settings such as in the production of stainless steel and various alloys complicate human exposure and health effects. Notably, interactions with nickel macromolecules, primarily through inhalation, have been demonstrated to promote lung cancer. Mechanisms of nickel-carcinogenesis range from oxidative stress, DNA damage, and hypoxia-inducible pathways to epigenetic mechanisms. Recently, non-coding RNAs have drawn increased attention in cancer mechanistic studies. Specifically, nickel has been found to disrupt expression and functions of micro-RNAs and long-non-coding RNAs, resulting in subsequent changes in target gene expression levels, some of which include key cancer genes such as p53, MDM2, c-myc, and AP-1. Non-coding RNAs are also involved in well-studied mechanisms of nickel-induced lung carcinogenesis, such as the hypoxia-inducible factor (HIF) pathway, oxidative stress, DNA damage and repair, DNA hypermethylation, and alterations in tumor suppressors and oncogenes. This review provides a summary of the currently known epigenetic mechanisms involved in nickel-induced lung carcinogenesis, with a particular focus on non-coding RNAs.

miR-197-5p inhibits sarcomagenesis and induces cellular senescence via repression of KIAA0101

The abnormal expressions of microRNAs (miRNAs) are known to be associated with various pathophysiological processes that lead to the development of a plethora of diseases including cancer. Among several miRNAs studied so far, miR-197 has been reported to play a vital role either as an oncogene or tumor suppressor in different cancers. However, its role in carcinogenesis of fibrosarcoma has not yet been elucidated. Therefore, the current study investigated the role of miR-197-5p, which is significantly downregulated in HT1080 fibrosarcoma cells compared to IMR90-tert fibroblast cells. The transient overexpression of miR-197-5p causes a significant decrease in viability and proliferation of fibrosarcoma cells in both concentration- and time-dependent manners. Interestingly, we did not observe any significant changes in cell cycle pattern or apoptotic cell populations, but rather noticed cellular senescence of fibrosarcoma cells upon overexpression of miR-197-5p. Further, this miRNA suppresses the metastatic properties, such as migration, invasion, and anchorage-independent growth of fibrosarcoma possibly through targeting KIAA0101, which is a proliferating cell nuclear antigen-associated factor and overexpressed in the malignancy. In nutshell, our result revealed that miR-197-5p acts as an oncosuppressor miRNA in fibrosarcoma through target regulation of KIAA0101, which can be exploited for developing RNA-based therapeutic strategies for the cure of this malignancy.

Bufalin Induces Apoptosis and Improves the Sensitivity of Human Glioma Stem-Like Cells to Temozolamide

Glioma is the most common malignant tumor of the central nervous system, and it is characterized by high relapse and fatality rates and poor prognosis. Bufalin is one of the main ingredients of Chan-su, a traditional Chinese medicine (TCM) extracted from toad venom. Previous studies revealed that bufalin exerted inhibitory effects on a variety of tumor cells. To demonstrate the inhibitory effect of bufalin on glioma cells and glioma stem-like cells (GSCs) and discuss the underlying mechanism, the proliferation of glioma cells was detected by MTT and colony formation assays following treatment with bufalin. In addition, we investigated whether bufalin inhibits or kills GSCs using flow cytometry, Western blotting, and reverse transcription polymerase chain reaction analysis (RT-PCR). Finally, we investigated whether bufalin could improve the therapeutic effect of temozolomide (TMZ) and discussed the underlying mechanism. Taken together, our data demonstrated that bufalin inhibits glioma cell growth and proliferation, inhibits GSC proliferation, and kills GSCs. Bufalin was found to induce the apoptosis of GSCs by upregulating the expression of the apoptotic proteins cleaved caspase 3 and poly(ADP-ribose) polymerase (PARP) and by downregulating the expression of human telomerase reverse transcriptase, which is a marker of telomerase activity. Bufalin also improved the inhibitory effect of TMZ on GSCs by activating the mitochondrial apoptotic pathway. These results suggest that bufalin damages GSCs, induces apoptosis, and enhances the sensitivity of GSCs to TMZ.

MicroRNA controls of cellular senescence

Cellular senescence is a state of permanent cell-cycle arrest triggered by different internal and external stimuli. This phenomenon is considered to be both beneficial and detrimental depending on the cell types and biological contexts. During normal embryonic development and after tissue injury, cellular senescence is critical for tissue remodeling. In addition, this process is useful for arresting growth of tumor cells, particularly during early onset of tumorigenesis. However, accumulation of senescent cells decreases tissue regenerative capabilities and induces inflammation, which is responsible for cancer and organismal aging. Therefore cellular senescence has to be tightly regulated, and dysregulation might lead to the aging and human diseases. Among many regulators of cellular senescence, in this review, I will focus on microRNAs, small non-coding RNAs playing critical roles in diverse biological events including cellular senescence. [BMB Reports 2018; 51(10): 494-500].

Interplay between small and long non-coding RNAs in cutaneous melanoma: a complex jigsaw puzzle with missing pieces

The incidence of cutaneous melanoma (CM) has increased in the past few decades. The biology of melanoma is characterized by a complex interaction between genetic, environmental and phenotypic factors. A greater understanding of the molecular mechanisms that promote melanoma cell growth and dissemination is crucial to improve diagnosis, prognostication, and treatment of CM. Both small and long non-coding RNAs (lncRNAs) have been identified to play a role in melanoma biology; microRNA and lncRNA expression is altered in transformed melanocytes and this in turn has functional effects on cell proliferation, apoptosis, invasion, metastasis, and immune response. Moreover, specific dysregulated ncRNAs were shown to have a diagnostic or prognostic role in melanoma and to drive the establishment of drug resistance. Here, we review the current literature on small and lncRNAs with a role in melanoma, with the aim of putting into some order this complex jigsaw puzzle.

Melanoma: Where we are and where we go

Melanoma is known as an aggressive tumor which shows an increasing incidence and poor prognosis in the metastatic phase. Hence, it seems that diagnosis and effective management (including early diagnosis, choosing of the effective therapeutic platform, caring, and training of patients for early detection) are major aspects of melanoma therapy. Early detection of melanoma is a key point for melanoma therapy. There are various diagnosis options such as assessing of biopsy, imaging techniques, and biomarkers (i.e., several proteins, polymorphism, and liquid biopsy). Among the various biomarkers, assessing circulating tumor cells, cell-free DNAs, cell-free RNAs, and microRNAs (miRNAs) have emerged as powerful diagnosis tools for melanoma patients. Deregulations of these molecules are associated with melanoma pathogenesis. After detection of melanoma, choosing of effective therapeutic regimen is a key step for recovery of melanoma patients. Several studies indicated that various therapeutic approaches including surgery, immunotherapy, systematic therapy, radiation therapy and antibodies therapy could be used as potential therapeutic candidates for melanoma therapy. Caring for melanoma patients is one of the important components of melanoma therapy. Caring and training for melanoma patients could contribute to better monitoring of patients in response to various therapeutic options. Here, we summarized various diagnosis approaches such as assessing biopsy, imaging techniques, and utilization of various biomarkers (i.e., proteins, CTCs, cfDNAs, and miRNAs) as a diagnostic biomarker for detection and monitoring patients with melanoma. Moreover, we highlighted various therapeutic options and caring aspects in patients with melanoma.

MicroRNA-148a inhibits cell proliferation and cell cycle progression in lung adenocarcinoma via directly targeting transcription factor E2F3

MicroRNAs (miRs) serve important roles in various human cancers, including lung adenocarcinoma. Exploring the function and regulatory mechanism of miRs underlying lung adenocarcinoma progression may contribute to identifying novel therapeutic targets and candidates. The present study aimed to examine miR-148a expression and investigate the molecular mechanisms of miR-148a in lung adenocarcinomas. The data from the current study indicated that miR-148a was significantly downregulated in lung adenocarcinoma tissues and cell lines, and low miR-148a expression was significantly associated with advanced Tumor, Node, Metastasis stages and lymph node metastasis, as well as the shorter survival time of patients. Increased miR-148a expression markedly decreased the cell proliferation, colony formation and cell cycle progression of H23 and H1975 cells. Transcription factor E2F3 (E2F3) was identified as a target of miR-148a in H23 and H1975 cells. The expression of E2F3 was negatively mediated by miR-148a in H23 and H1975 cells. In addition, E2F3 was significantly upregulated in lung adenocarcinoma tissues and cell lines, and the expression of miR-148a was inversely correlated with E2F3 expression in lung adenocarcinoma tissues. Additional experiments demonstrated that increased E2F3 expression counteracted the inhibitory effects on lung adenocarcinoma cells caused by miR-148a overexpression. In summary, the findings of the current study suggest that miR-148a may have suppressive effects on the proliferation of lung adenocarcinoma cells at least in part through directly targeting E2F3. Therefore, miR-148a may be used as a potential candidate for the treatment of lung adenocarcinoma.

Elucidating the microRNA-203 specific biological processes in glioblastoma cells from comprehensive RNA-sequencing transcriptome profiling

Glioblastoma (GBM) is the most common primary malignant intracranial adult brain tumor. Allelic deletion on chromosome 14q plays an essential role in GBM pathogenesis, and this chromosome 14q site was thought to harbor multiple tumor suppressor genes associated with GBM, a region that also encodes microRNA-203 (miR-203). This study was conducted to identify whole transcriptome profile changes associated with miR-203 expression by high-throughput RNA sequencing. Enrichment analyses for gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that miR-203 expression had a strong, negative effect on a number of fundamental and interconnected biological processes involved in cell growth and proliferation. The biological processes mostly influenced were p53 signaling pathway, FoxO signaling pathway, DNA replication, cell cycle, MAPK signaling pathway, and apoptosis. In total, 847 upregulated and 345 downregulated differentially expressed genes were identified in control versus miR-203 expressing glioma cells. After GO enrichment, the downregulated differentially expressed genes such as BCL2, SPARC were found to be mainly enriched in cell cycle regulation and apoptosis processes, whereas the upregulated differentially expressed genes such as CCND1, E2F1 were involved in the DNA replication and cell cycle regulation. We also performed miR-203 target analysis and found BCL2, AKT, SPARC, ROBO1, c-JUN, PDGFA, and CREB were predicted target of miR-203 and miR-203 expression suppressed the protein and mRNA levels of these target genes by western blotting and qRT-PCR analysis. Moreover, co-transfection experiments using a luciferase-based reporter assay demonstrated that miR-203 directly regulated BCL-2 expression and BCL-2 overexpression suppressed miR-203 mediated glioma cell apoptosis. These results indicate that overexpression of miR-203 coordinately regulates several oncogenic pathways in GBM.

Effect of young exosomes injected in aged mice

INTRODUCTION

Exosomes, nanosized extracellular vesicles, are known to circulate through the blood stream to transfer molecular signals from tissue to tissue.

METHODS

To determine whether exosomes affect aging in animals, we primarily identified the changes in exosomal miRNA contents during the aging process. In exosomes from 12-month-old mice, mmu-miR-126-5p and mmu-miR-466c-5p levels were decreased and mmu-miR-184-3p and mmu-miR-200b-5p levels were increased significantly compared with those of 3-month-old mice. Their levels in exosomes were partially correlated with those in tissues: levels of only mmu-miR-126-5p and mmu-miR-466c-5p in lungs and/or liver were decreased, but those of mmu-miR-184-3p and mmu-miR-200b-5p in tissues did not coincide with those of exosomes.

RESULTS AND DISCUSSION

In the aged tissues injected with young exosomes isolated from serum, mmu-miR-126b-5p levels were reversed in the lungs and liver. Expression changes in aging-associated molecules in young exosome-injected mice were obvious: p16Ink4A, MTOR, and IGF1R were significantly downregulated in the lungs and/or liver of old mice. In addition, telomerase-related genes such as Men1, Mre11a, Tep1, Terf2, Tert, and Tnks were significantly upregulated in the liver of old mice after injection of young exosomes.

CONCLUSION

These results indicate that exosomes from young mice could reverse the expression pattern of aging-associated molecules in aged mice. Eventually, exosomes may be used as a novel approach for the treatment and diagnosis of aging animals.

RAB22A overexpression promotes the tumor growth of melanoma

Malignant melanoma is the most aggressive type of skin cancer. RAB22A, a member of RAS oncogene family, has been found to be significantly upregulated in multiple human cancers. In the present study, we found that RAB22A mRNA expression was significantly upregulated in melanoma tissues (including 60 primary melanomas and 84 metastatic melanomas) compared to benign nevi (n = 20), which were significantly higher in metastatic melanoma tissues than primary tissues. Immunohistochemistry data further showed that the positive immunoreactivity of RAB22A was detected in 66% (95/144) melanoma tissues, but not in benign nevi. Moreover, high expression of RAB22A was significantly associated with advanced clinical stage in melanoma. Furthermore, patients with high RAB22A expression had shorter overall survival compared those with low expression of RAB22A. In-vitro study showed that RAB22A was also upregulated in melanoma cell lines WM35, A375, WM451, and SK-MEL-1, when compared with the normal melanocyte HM cells. Knockdown of RAB22A significantly reduced the proliferation, migration and invasion of melanoma A375 cells, while overexpression of RAB22A significantly promoted these malignant phenotypes. In addition, RAB22A was found to be a target of miR-203, a tumor suppressive miRNA in melanoma. Besides, miR-203 was downregulated in melanoma tissues and cell lines, when compared with benign nevi and HM cells, respectively. Taken these findings together, our study could validate an oncogenic role of RAB22A in melanoma, suggesting that RAB22A may be a potential therapeutic target for melanoma.

Overexpression of KLF4 promotes cell senescence through microRNA-203-survivin-p21 pathway

Krüppel-like factor 4 (KLF4) is a transcription factor and functions as a tumor suppressor or tumor promoter in different cancer types. KLF4 regulates many gene expression, thus affects the process of cell proliferation, differentiation, and apoptosis. Recently, KLF4 was reported to induce senescence during the generation of induced pluripotent stem (iPS) cells, but the exact mechanism is still unclear. In this study, we constructed two doxycycline-inducing KLF4 cell models, and demonstrated overexpression of KLF4 could promote cell senescence, detected by senescence-associated β-galactosidase activity assay. Then we confirmed that p21, a key effector of senescence, was directly induced by KLF4. KLF4 could also inhibit survivin, which could indirectly induce p21. By miRNA microarray, we found a series of miRNAs regulated by KLF4 and involved in senescence. We demonstrated that KLF4 could upregulate miR-203, and miR-203 contributed to senescence through miR-203-survivin-p21 pathway. Our results suggest that KLF4 could promote cell senescence through a complex network: miR-203, survivin, and p21, which were all regulated by overexpression of KLF4 and contributed to cell senescence.

Lung microRNA deregulation associated with impaired alveolarization in rats after intrauterine growth restriction

Intrauterine growth restriction (IUGR) was recently described as an independent risk factor of bronchopulmonary dysplasia, the main respiratory sequelae of preterm birth. We previously showed impaired alveolarization in rat pups born with IUGR induced by a low-protein diet (LPD) during gestation. We conducted a genome-wide analysis of gene expression and found the involvement of several pathways such as cell adhesion. Here, we describe our unbiased microRNA (miRNA) profiling by microarray assay and validation by qPCR at postnatal days 10 and 21 (P10 and P21) in lungs of rat pups with LPD-induced lung-alveolarization disorder after IUGR. We identified 13 miRNAs with more than two-fold differential expression between control lungs and LPD-induced IUGR lungs. Validated and predicted target genes of these miRNAs were related to “tissue repair” at P10 and “cellular communication regulation” at P21. We predicted the deregulation of several genes associated with these pathways. Especially, E2F3, a transcription factor involved in cell cycle control, was expressed in developing alveoli, and its mRNA and protein levels were significantly increased at P21 after IUGR. Hence, IUGR affects the expression of selected miRNAs during lung alveolarization. These results provide a basis for deciphering the mechanistic contributions of IUGR to impaired alveolarization.

MicroRNA-34a promotes mitochondrial dysfunction-induced apoptosis in human lens epithelial cells by targeting Notch2

Purpose

Human lens epithelial cell (HLEC) apoptosis is a common pathogenic mechanism in age-related cataracts (ARC). While the function of microRNAs (miRNAs) in the eye is beginning to be explored using miRNA expression array, the role of miR-34a in regulating HLEC apoptosis remains unknown and requires further investigation.

Methods

Quantitative reverse-transcript polymerase chain reaction (RT-PCR) was used to determine the expression level of miR-34a in cataractous and control samples. MiR-34a mimics and small interfering RNAs were transfected into SRA01/04. Cell apoptosis and oxidative stress were assessed by flow cytometry. The Dual-Luciferase Reporter Assay System was used to confirm whether miR-34a bound to the 3'-UTR of the target gene and blocked its activity. The potential roles of the identified target genes in apoptosis and mitochondria dysfunction were also evaluated.

Results

The expression of miR-34a increased in lens epithelial samples of ARC compared with the transparent group (cataract 2.41±0.81 vs. control 1.20±0.44, P=0.005). In cultured SRA01/04, miR-34a increased reactive oxygen species production and induced apoptosis (early apoptosis: 45.55%±5.96% vs. 15.85%±4.93%, P<0.01; late apoptosis: 6.10%±2.67% vs. 0.95%±0.42%, P<0.01). Overexpression of miR-34a promoted mitochondria-mediated apoptosis through activation of caspase-9, disruption of the mitochondrial membrane potential, blocking of mitochondrial energy metabolism and enhancement of cytochrome C release. Furthermore, Notch1 and Notch2 were confirmed as putative targets of miR-34a, but only Notch2 was verified as the effector that triggered mitochondria-mediated apoptosis.

Conclusion

MicroRNA-34a is increased in the cataractous lens and triggers mitochondria-mediated apoptosis and oxidative stress by suppressing Notch2.

Expression Profiling of MicroRNAs in the Inner Ear of Elderly People by Real-Time PCR Quantification

The molecular mechanisms underlying age-related hearing loss are unknown, and currently, there is no treatment for this condition. Recent studies have shown that microRNAs (miRNAs) and age-related diseases are intimately linked, suggesting that some miRNAs may present attractive therapeutic targets. In this study, we obtained 8 human temporal bones from 8 elderly subjects at brain autopsy in order to investigate the expression profile of miRNAs in the inner ear with miRNA arrays. A mean of 478 different miRNAs were expressed in the samples, of which 348 were commonly expressed in all 8 samples. Of these, levels of 16 miRNAs significantly differed between young elderly and old elderly subjects. miRNAs, which play important roles in inner ear development, were detected in all samples, i.e., in both young and old elderly subjects, whether with or without hearing loss. Our results suggest that these miRNAs play important roles not only in development, but also in the maintenance of inner ear homeostasis.

The expression level of miR-203 in patients with gastric cancer and its clinical significance

BACKGROUND

The clinical significance of miR-203 and its prognostic value have not been investigated in gastric cancer.

METHODS

We assessed miR-203 expression in 141 gastric cancer samples and 141 paired non-cancerous samples by real-time PCR and calculated using the 2^-ΔΔCt method. Differences between groups were examined for statistical significance by Student's t-test. Survival curves were computed by the Kaplan-Meier method, and differences between survival curves were compared by the log rank test.

RESULTS

The expression of miR-203 was significantly lower in gastric cancer samples compared to non-cancerous samples (P<0.0001). Low miR-203 expression was found to be closely correlated with advanced stage (p=0.005), and lymph node involvement (p=0.009). Kaplan-Meier analysis with the log-rank test indicated that low miR-203 expression had a significant impact on overall survival (39.4% vs. 62.5%; P=0.043) and progression-free survival (32.5% vs. 58.6%; P=0.023). Furthermore, multivariate analysis revealed that miR-203 expression level was independent prognostic factors for overall survival (HR=2.73, 95% CI: 1.69-8.91; P=0.01), as well as progression-free survival (HR=4.19, 95% CI: 2.91-10.12; P=0.005).

CONCLUSION

Our data validate an important clinical significance of miR-203 in gastric cancer, and reveal that it might be a potential prognostic factor for gastric cancer. Large- scale and long-term follow-up studies are needed to confirm the significance of miR-203 in gastric cancer.

miRNA-34b is directly involved in the aging of macrophages

BACKGROUND

MicroRNAs (miRNAs) are a class of short noncoding RNA that play important regulatory roles in living organisms. These RNA molecules are implicated in the development and progression of malignant diseases such as cancer and are closely associated with cell aging. Findings demonstrating that microRNA is associated with aging in macrophages have nevertheless rarely been reported.

AIMS

This study's objective was to investigate if miRNA-34 is linked to aging process of macrophages.

METHODS

We built a cell aging model in mouse RAW264.7 macrophages using D-galactose and determined the expression levels of miRNA-34a, miRNA-34b, and miRNA-34c in aging and normal macrophages by fluorescence quantitative polymerase chain reaction (q-PCR). We predicted a target gene of miRNA-34 using biological information techniques and constructed the recombinant plasmid pGL3-E2f3 for the putative target gene E2f3.

RESULTS

The expression level of miRNA-34b was 5.23 times higher in aging macrophages than in normal macrophages. The luciferase activity decreased by nearly 50 % in cells transfected with miRNA-34b mimics, while no significant decrease in luciferase activity was noted in cells transfected with the miRNA-34b inhibitor or unrelated sequences.

DISCUSSION

Our findings provide the groundwork for further research into the molecular mechanisms whereby miRNA-34b regulates the aging of macrophages.

CONCLUSIONS

miRNA-34b is associated with the aging of RAW264.7 macrophages, and E2f3 is a target gene of miRNA-34b.

Senescence-Associated MicroRNAs

Senescent cells arise as a consequence of cellular damage and can have either a detrimental or advantageous impact on tissues and organs depending on the specific cell type and metabolic state. As senescent cells accumulate in tissues with advancing age, they have been implicated in many age-related declines and diseases. The major facets of senescence include two pathways responsible for establishing and maintaining a senescence program, p53/CDKN1A(p21) and CDKN2A(p16)/RB, as well as the senescence-associated secretory phenotype. Numerous MicroRNAs influence senescence by modulating the abundance of key senescence regulatory proteins, generally by lowering the stability and/or translation of mRNAs that encode such factors. Accordingly, understanding the molecular mechanisms by which MicroRNAs influence senescence will enable diagnostic and therapeutic opportunities directed at senescent cells. Here, we review senescence-associated (SA)-MicroRNAs and discuss their implications in senescence-relevant pathologies.

MiRNAs and E2F3: a complex network of reciprocal regulations in human cancers

E2F transcription factor 3 (E2F3) is oncogenic in tumorigenesis. Alterations in E2F3 functions correspond with poor prognosis in various cancers, underscoring their status for the clinical cancer phenotype. Latest reports discovered intricate networks between microRNAs (miRNAs) and E2F3 in regulating the balance of these events, including proliferation, apoptosis, metastasis, as well as drug resistance. miRNAs are non-coding small RNAs which negatively regulate gene expressions post-transcriptionally mainly through 3′-UTR binding of target mRNAs. Increasing evidence shows that E2F3 can be activated/inhibited by numerous miRNAs whose dysregulation has been implicated in malignancy. In turn, miRNAs themselves can be transcriptionally regulated by E2F3, thus forming a negative feedback loop. These findings add a new challenging layer of complexity to E2F3 network. Current understanding of the reciprocal link between E2F3 and miRNAs in human cancers were summarized, which could help to develop potential therapeutic strategies.

MicroRNAs miR-203-3p, miR-664-3p and miR-708-5p are associated with median strain lifespan in mice

MicroRNAs (miRNAs) are small non-coding RNA species that have been shown to have roles in multiple processes that occur in higher eukaryotes. They act by binding to specific sequences in the 3’ untranslated region of their target genes and causing the transcripts to be degraded by the RNA-induced silencing complex (RISC). MicroRNAs have previously been reported to demonstrate altered expression in several aging phenotypes such as cellular senescence and age itself. Here, we have measured the expression levels of 521 small regulatory microRNAs (miRNAs) in spleen tissue from young and old animals of 6 mouse strains with different median strain lifespans by quantitative real-time PCR. Expression levels of 3 microRNAs were robustly associated with strain lifespan, after correction for multiple statistical testing (miR-203-3p [β-coefficient = −0.6447, p = 4.8 × 10⁻¹¹], miR-664-3p [β-coefficient = 0.5552, p = 5.1 × 10⁻⁸] and miR-708-5p [β-coefficient = 0.4986, p = 1.6 × 10⁻⁶]). Pathway analysis of binding sites for these three microRNAs revealed enrichment of target genes involved in key aging and longevity pathways including mTOR, FOXO and MAPK, most of which also demonstrated associations with longevity. Our results suggests that miR-203-3p, miR-664-3p and miR-708-5p may be implicated in pathways determining lifespan in mammals.

Host microRNA-203a Is antagonistic to the progression of foot-and-mouth disease virus infection

Sam68 was previously shown to be a critical host factor for foot-and-mouth disease virus (FMDV) replication. MicroRNA (miR) miR-203a is reportedly a negative regulator of Sam68 expression both in vitro and in vivo. Here, transfection of miR-203a-3p and miR-203a-5p mimics separately and in combination in a porcine cell line followed by FMDV infection resulted in diminished viral protein synthesis and a 4 and 6log reduction in virus titers relative to negative controls, respectively. Unexpectedly, Sam68 expression was increased by miR-203a-5p transfection, but not miR-203a-3p. miR-203a-5p also down-regulated Survivin expression, which was predicted to play a role in FMDV infection. Moreover, miR-203a-5p but not miR-203a-3p affected a reduction in FMDV viral RNA. These effects were not replicated with a related Picornavirus, suggesting FMDV specificity. Importantly, miR-203a-3p and miR-203a-5p impaired FMDV infection across multiple FMDV serotypes. We concluded that miR-203a-3p and miR-203a-5p represent attractive potential naturally occurring bio-therapeutics against FMDV.

Senescence-Like Phenotypes in Human Nevi

Cellular senescence is an irreversible arrest of cell proliferation at the G1 stage of the cell cycle in which cells become refractory to growth stimuli. Senescence is a critical and potent defense mechanism that mammalian cells use to suppress tumors. While there are many ways to induce a senescence response, oncogene-induced senescence (OIS) remains the key to inhibiting progression of cells that have acquired oncogenic mutations. In primary cells in culture, OIS induces a set of measurable phenotypic and behavioral changes, in addition to cell cycle exit. Senescence-associated β-Galactosidase (SA-β-Gal) activity is a main hallmark of senescent cells, along with morphological changes that may depend on the oncogene that is activated, or on the primary cell type. Characteristic cellular changes of senescence include increased size, flattening, multinucleation, and extensive vacuolation. At the molecular level, tumor suppressor genes such as p53 and p16 ^INK4A may play a role in initiation or maintenance of OIS. Activation of a DNA damage response and a senescence-associated secretory phenotype could delineate the onset of senescence. Despite advances in our understanding of how OIS suppresses some tumor types, the in vivo role of OIS in melanocytic nevi and melanoma remains poorly understood and not validated. In an effort to stimulate research in this field, we review in this chapter the known markers of senescence and provide experimental protocols for their identification by immunofluorescent staining in melanocytic nevi and malignant melanoma.

miR-203a is involved in HBx-induced inflammation by targeting Rap1a

Hepatitis B virus (HBV) causes acute and chronic hepatitis, and is one of the major causes of cirrhosis and hepatocellular carcinoma. Accumulating evidence suggests that inflammation is the key factor for liver cirrhosis and hepatocellular carcinoma. MicroRNAs play important roles in many biological processes. Here, we aim to explore the function of microRNAs in the HBX-induced inflammation. First, microarray experiment showed that HBV⁺ liver samples expressed higher level of miR-203a compared to HBV^- liver samples. To verify these alterations, HBx-coding plasmid was transfected into HepG2 cells to overexpress HBx protein. The real-time PCR results suggested that over-expression of HBx could induce up-regulation of miR-203a. To define how up-regulation of miR-203a can induce liver cells inflammation, we over-expressed miR-203a in HepG2 cells. Annexin V staining and BrdU staining suggested that overexpression of miR-203a significantly increased the cell apoptosis and proliferation, meanwhile, over-expression of miR-203a could lead to a decrease in G0/G1 phase cells and an increase in G2/M phase cells. Some cytokines production including IL-6 and IL-8 were significantly increased, but TGFβ and IFNγ were decreased in miR-203a over-expressed HepG2 cells. Luciferase reporter assay experiments, protein mass-spectrum assay and real-time PCR all together demonstrated that Rap1a was the target gene of miR-203a. Further experiments showed that these alterations were modulated through PI3K/ERK/p38/NFκB pathways. These data suggested that HBV-infection could up-regulate the expression of miR-203a, thus down regulated the expression of Rap1a and affected the PI3K/ERK/p38/NFκB pathways, finally induced the hepatitis inflammation.

scan_tcga tools for integrated epigenomic and transcriptomic analysis of tumor subgroups

Aim: The Cancer Genome Atlas contains multiple levels of genomic data (mutation, gene expression, DNA methylation, copy number variation) for 33 cancer types for almost 11,000 patients. However, a dearth of appropriate software tools makes it difficult for bench scientists to use these data effectively. Materials & methods: Here, we present a suite of flexible, fast and command line-based scripts that will allow retrieval and analysis of DNA methylation (tool: scan_tcga_methylation.awk), mRNA (tool: scan_tcga_mRNA.awk) and miRNA expression (tool: scan_tcga_miRNAs.awk) from cancer genome atlas network level 3 data. Results: We demonstrate the utility of these tools by analyzing DNA methylation and mRNA expression signatures of 60 frequently deregulated cancer genes and also of 30 miRNAs in primary (n = 102) and metastatic melanoma patients (n = 367). Conclusion: Our analysis illustrates the validity of the scan_tcga tools and reveals the epigenomic signatures and importance of identifying smaller patient subgroups with distinct molecular profiles.

DNA methylation contributes toward silencing of antioncogenic microRNA-203 in human and canine melanoma cells

Melanoma is a poor-prognosis cancer in both humans and dogs. We have elucidated the antitumor mechanisms of antioncogenic microRNA (miR)-203 which is downregulated in human melanoma, as well as in canine melanoma. The aim of this study was to clarify the mechanism of this downregulation. We focused on epigenetic aberration of miR-203 transcription. Treatment with 5-aza-2'-deoxycitidine (5-aza) markedly upregulated the expression level of miR-203 in almost all of the cell lines tested. Furthermore, bisulfite sequencing or methylation-specific PCR showed DNA methylation of CpG islands upstream of the miR-203 coding region (MIR203) in both human and canine melanoma cells, as well as in canine clinical specimens, but not in human normal melanocytes. The results of a luciferase activity assay showed obvious suppression of the transcription of miR-203 by DNA methylation. The use of the luciferase activity assay for CREB1 and an inhibition assay of miR-203 function performed with an miR-203 inhibitor confirmed the contribution of miR-203 upregulation toward the negative regulation of the target gene of miR-203. These results indicate that canine melanoma might be a preclinical model of human melanoma for epigenetic studies. In addition, this study suggests that agents that can demethylate MIR203 could be a common promising therapeutic agent for the treatment of human and canine melanomas.

Update on melanoma epigenetics

PURPOSE OF REVIEW

Over the last years, our understanding in molecular biology of melanoma has grown significantly and many genetic alterations have been identified affecting melanoma pathogenesis. This growing evidence has led to the development of targeted therapies which are showing promising clinical results. In addition to genetic alterations, an increasing number of studies have recently demonstrated the role of epigenetics in melanoma development and progression. Here, we summarize the current data on epigenetic research in melanoma.

RECENT FINDINGS

MicroRNA (miRNA) expression profiling studies have identified several miRNAs implicated in melanoma cell cycle and proliferation, cell migration and invasion, as well as miRNAs involved in apoptosis and immune response. Abnormal methylation profiling has been associated with melanoma progression and to date aberrant hypermethylation in more than 70 genes has been described. Recent works have highlighted the increasing evidence of the role of histone modification as a central regulatory event in melanoma pathogenesis.

SUMMARY

Many of these epigenetic biomarkers may have potential diagnostic, prognostic and therapeutic implications. Future approach might be using a combination of genetic and epigenetic biomarkers.

MicroRNAs as potential diagnostic and prognostic biomarkers in melanoma

Melanoma is a life-threatening malignancy with poor prognosis and a relatively high burden of mortality in advanced stages. The efficacy of current available therapeutic strategies is limited, with a survival rate of less than 10%. Despite rapid advances in biomarker-guided drug development in different tumour types, including melanoma, only a very small number of biomarkers have been identified. Recently, microRNAs (miRNAs) have emerged as a molecular regulator in the development and progression of melanoma. Aberrant activation of some known miRNAs, e.g. let-7a and b, miR-148, miR-155, miR-182, miR-200c, miR-211, miR-214, miR-221 and 222, has been recognised to be linked with melanoma-associated genes such as NRAS, microphthalmia-associated transcription factor, receptor tyrosine kinase c-KIT, AP-2 transcription factor, etc. There is accumulating evidence suggesting the potential impact of circulating miRNAs as diagnostic and therapeutic markers in diseases. In addition, miRNAs have turned out to play important roles in drug-resistance mechanisms; suggesting their modulation as a potential approach to overcome chemoresistance. This review highlights recent preclinical and clinical studies on circulating miRNAs and their potential role as diagnosis, and therapeutic targets in melanoma.

Epigenetic markers in melanoma

Melanoma, one of the most virulent forms of human malignancy, is the primary cause of mortality from cancers arising from the skin. The prognosis of metastatic melanoma remains dismal despite targeted therapeutic regimens that exploit our growing understanding of cancer immunology and genetic mutations that drive oncogenic cell signaling pathways in cancer. Epigenetic mechanisms, including DNA methylation/demethylation, histone modifications and noncoding RNAs recently have been shown to play critical roles in melanoma pathogenesis. Current evidence indicates that imbalance of DNA methylation and demethylation, dysregulation of histone modification and chromatin remodeling, and altered translational control by noncoding RNAs contribute to melanoma tumorigenesis. Here, we summarize the most recent insights relating to epigenetic markers, focusing on diagnostic potential as well as novel therapeutic approaches for more effective treatment of advanced melanoma.

miRNAs in melanoma: a defined role in tumor progression and metastasis

The crosstalk of melanoma cells with components of the microenvironment promotes malignant cell proliferation and spread to distant tissues. Although the major pathogenetic events have already been elucidated, the mechanisms that drive the metastatic behavior of tumor cells are still undefined. MicroRNAs (miRNAs) are small non-coding RNAs that control post-transcriptional gene expression through interconnected kinases upstream of functional genes involved in tumor progression. Here, we review the biological relevance of melanoma-related miRNAs and focus on their potential role in propagating signals that may cause tumor microenvironment rearrangements, as well as disablement of the immune system and melanoma cell proliferation.

Epigenetic regulation in human melanoma: past and future

The development and progression of melanoma have been attributed to independent or combined genetic and epigenetic events. There has been remarkable progress in understanding melanoma pathogenesis in terms of genetic alterations. However, recent studies have revealed a complex involvement of epigenetic mechanisms in the regulation of gene expression, including methylation, chromatin modification and remodeling, and the diverse activities of non-coding RNAs. The roles of gene methylation and miRNAs have been relatively well studied in melanoma, but other studies have shown that changes in chromatin status and in the differential expression of long non-coding RNAs can lead to altered regulation of key genes. Taken together, they affect the functioning of signaling pathways that influence each other, intersect, and form networks in which local perturbations disturb the activity of the whole system. Here, we focus on how epigenetic events intertwine with these pathways and contribute to the molecular pathogenesis of melanoma.