MicroRNAs in Melanoma Biology

From oncogenes to tumor suppressors: The dual role of ncRNAs in fibrosarcoma

Fibrosarcoma is a challenging cancer originating from fibrous tissues, marked by aggressive growth and limited treatment options. The discovery of non-coding RNAs (ncRNAs), including long non-coding RNAs (lncRNAs), microRNAs (miRNAs), and small interfering RNAs (siRNAs), has opened new pathways for understanding and treating this malignancy. These ncRNAs play crucial roles in gene regulation, cellular processes, and the tumor microenvironment. This review aims to explore the impact of ncRNAs on fibrosarcoma's pathogenesis, progression, and resistance to treatment, focusing on their mechanistic roles and therapeutic potential. A comprehensive review of literature from databases like PubMed and Google Scholar was conducted, focusing on the dysregulation of ncRNAs in fibrosarcoma, their contribution to tumor growth, metastasis, drug resistance, and their cellular pathway interactions. NcRNAs significantly influence fibrosarcoma, affecting cell proliferation, apoptosis, invasion, and angiogenesis. Their function as oncogenes or tumor suppressors makes them promising biomarkers and therapeutic targets. Understanding their interaction with the tumor microenvironment is essential for developing more effective treatments for fibrosarcoma. Targeting ncRNAs emerges as a promising strategy for fibrosarcoma therapy, offering hope to overcome the shortcomings of existing treatments. Further investigation is needed to clarify specific ncRNAs' roles in fibrosarcoma and to develop ncRNA-based therapies, highlighting the significance of ncRNAs in improving patient outcomes in this challenging cancer.

Loss of miR-101-3p in melanoma stabilizes genomic integrity, leading to cell death prevention

Malignant melanoma remains the most lethal form of skin cancer, exhibiting poor prognosis after forming distant metastasis. Owing to their potential tumor-suppressive properties by regulating oncogenes and tumor suppressor genes, microRNAs are important player in melanoma development and progression. We defined the loss of miR-101-3p expression in melanoma cells compared with melanocytes and melanoblast-related cells as an early event in tumor development and aimed to understand the tumor suppressive role of miR-101-3p and its regulation of important cellular processes. Reexpression of miR-101-3p resulted in inhibition of proliferation, increase in DNA damage, and induction of apoptosis. We further determined the nuclear structure protein Lamin B1, which influences nuclear processes and heterochromatin structure, ATRX, CASP3, and PARP as an important direct target of miR-101-3p. RNA sequencing and differential gene expression analysis after miR-101-3p reexpression supported our findings and the importance of loss of mir-101-3p for melanoma progression. The validated functional effects are related to genomic instability, as recent studies suggest miRNAs plays a key role in mediating this cellular process. Therefore, we concluded that miR-101-3p reexpression increases the genomic instability, leading to irreversible DNA damage, which leads to apoptosis induction. Our findings suggest that the loss of miR-101-3p in melanoma serves as an early event in melanoma progression by influencing the genomic integrity to maintain the increased bioenergetic demand.

Therapeutic applications of local injection of hsa-miR-634 into canine spontaneous malignant melanoma tumors

Malignant melanoma (MM) is one of the most common tumors in both dogs and humans. As canine MM (CMM) and human MM (HMM) have similar clinical characteristics, CMM appears to be a good clinical model for HMM. We previously demonstrated that the introduction of a synthetic double-strand-microRNA-634 (miR-634) mimic triggered apoptotic cell death by directly targeting the genes associated with cytoprotective processes in various human cancer cell lines, including those of HMM. This study aimed to investigate the antitumor effects of the local administration of miR-634 on spontaneous CMMs to provide a basis for future applications of miR-634 formulations in HMM treatment. We found that miR-634 administration induced apoptosis in CMM cell lines in vitro via downregulation of Asct2, Nrf2, and survivin expression, similar to the mechanisms in HMM cell lines. Furthermore, intratumoral miR-634 administration induced antitumor effects in four of seven spontaneous CMM cases, with no adverse effects. Local administration of miR-634 to lung metastasis under ultrasound guidance induced tumor shrinkage. These results confirm the antitumor effect of the local administration of miR-634 in spontaneous CMM, a model for spontaneous HMM, thereby providing a novel treatment strategy for HMM.

MicroRNA-155 and Disease-Related Immunohistochemical Parameters in Cutaneous Melanoma

Cutaneous melanoma is a severe and life-threatening form of skin cancer with growing incidences. While novel interventions have improved prognoses for these patients, early diagnosis of targeted treatment remains the most effective approach. MicroRNAs have grown to good use as potential biomarkers for early detection and as targets for treatment. miR-155 is well-studied for its role in tumor cell survival and proliferation in various tissues, although its role in melanoma remains controversial. In silico data analysis was performed in the dbDEMC v.3 to identify differentially expressed miRNA. We validated gene targets in melanoma using TarBase v8.0 and miRPath v3.0 and determined protein-protein interactions of the target genes. One hundred forty patients (age range 21-90 years) with cutaneous melanoma who underwent resection were included. Molecular assessment using Real-Time RT-qPCR, clinicopathological associations, and a literature review for the different roles of miR-155 in melanoma were performed. Analysis of the dbDEMC reveals controversial findings. While there is evidence of upregulation of miR-155 in primary and metastatic melanoma samples, others suggest decreased expression in later-stage melanoma and cases with brain metastasis. miR-155 has been overexpressed in prior cases of melanoma and precancerous lesions, and it was found to be dysregulated when compared to benign nevi. While miR-155 expression was associated with favorable outcomes in some studies, others showed an association with metastasis. Patients with high levels of miR-155 also noted reduction after receiving anti-PD-1 treatment, correlated with more prolonged overall survival. In our patient's cohort, 22.9% relapsed during treatment, and 45% developed recurrence, associated with factors such as lymph node infiltration, high mitotic index, and positive staining for CD117. Although overall analysis revealed miR-155 downregulation in melanoma specimens compared to non-cancer tissues, increased expression of miR-155 was associated with cases of superficial spreading melanoma subtype (p = 0.005) and any melanoma with a high mitotic rate (p = 0.010). The analysis did not identify optimum cutoff values to predict relapse, recurrence, or mortality. In conclusion, miR-155 could have, in part, a potential prognostic utility in cutaneous melanoma. Further mechanistic studies are required to unravel the multifunctional role of miR-155 in melanoma.

Non-coding RNA dysregulation in skin cancers

Skin cancers are the most common cancers worldwide. They can be classified in melanoma and non-melanoma skin cancer (NMSC), the latter includes squamous cell carcinoma (SCC), basal cell carcinoma (BCC) and merkel cell carcinoma (MCC). In recent years, the crucial role of non-coding RNAs (ncRNAs) in skin cancer pathogenesis has become increasingly evident. NcRNAs are functional RNA molecules that lack any protein-coding activity. These ncRNAs are classified based on their length: small, medium-size, and long ncRNAs. Among the most studied ncRNAs there are microRNAs (miRNAs), long non-coding RNAs (lncRNAs), and circular RNA (circRNAs). ncRNAs have the ability to regulate gene expression at transcriptional and post-transcriptional levels and are involved in skin cancer cell proliferation, angiogenesis, invasion, and metastasis. Many ncRNAs exhibit tissue- or cell-specific expression while others have been correlated to tumor staging, drug resistance, and prognosis. For these reasons, ncRNAs have both a diagnostic and prognostic significance in skin cancers. Our review summarizes the functional role of ncRNAs in skin cancers and their potential clinical application as biomarkers.

Inhibition of the cell migration, invasion and chemoresistance of colorectal cancer cells through targeting KLF3 by miR-365a-3p

Background: Metastasis and chemoresistance limit treatment efficacy of colorectal cancer (CRC) patients. MicroRNAs (miRNAs) have been believed to be candidate biomarkers for tumor cell proliferation, metastasis and chemoresistance, but the related molecular mechanisms are not clear for prognosis prediction.

Aims: We aimed to investigate the role of miR-365a-3p in metastasis and chemoresistance of CRC.

Methods: The expression levels of miR-365a-3p in clinical CRC tissues were analyzed. The effects of miR-365a-3p expression levels on tumor chemoresistance, invasion and migration were also determined. A dual luciferase reporter gene assay was used to determine the effect of miR-365a-3p on its target gene, Kruppel-like factor 3 (KLF3), and the effect of the miR-365a-3p/KLF3 axis on CRC cell chemoresistance, migration and invasion was further investigated.

Results: In patients with CRC with lymph node or distant organ metastasis or in CRC cell lines, the expression levels of miR-365a-3p were significantly downregulated. In addition, the findings of Transwell assays demonstrated that miR-365a-3p significantly suppressed CRC cell migration and invasion. The dual luciferase reporter gene assay results suggested that miR-365a-3p may play an important role in the regulation of migration, invasion and chemoresistance in CRC cells.

Conclusions: The findings of present study provided evidence to suggest that miR-365a-3p may be a potential tumor suppressor gene in CRC and may inhibit the migration, invasion and chemoresistance of CRC cells. These results suggested that targeting miR-365a-3p/KLF3 axis may represent a potential therapeutic intervention for metastatic disease in patients with CRC.

Up-regulation of KISS1 as a novel target of Let-7i in melanoma serves as a potential suppressor of migration and proliferation in vitro

Melanoma is a kind of skin cancer that is begun by the alteration of melanocytes. miRNAs are small non-coding RNA molecules that regulate a variety of biological processes. KISS1, the metastasis-suppressor gene, encodes kisspeptins which inhibits migration and proliferation of cancers. This study was aimed to determine the role of Let-7i and KISS1 in melanoma cell migration and proliferation. At first, the expression of Let-7i and KISS1 was determined in patients with melanoma. In the in vitro part of the study, Let-7i mimics were transfected and the impact of its restoration on target gene expression, proliferation, migration and apoptosis of SK-MEL-3 melanoma cell line was assessed by real-time PCR and Western blotting, MTT assay, wound-healing assay and flow cytometry, respectively. Besides, KISS1 inhibitor siRNA alone and along with Let-7i was transfected to determine their probable correlation. The results revealed that either Let-7i or KISS1 were down-regulated in patients with melanoma. The results obtained from the in vitro part of the study revealed that restoration of Let-7i reduced the expression of metastasis- and proliferation-related target genes. Moreover, it was revealed that up-regulation of Let-7i attenuated migration and proliferation capability of SK-MEL-3 cells. Besides, it was demonstrated that Let-7i restoration induced apoptosis in melanoma cells. More importantly, the KISS1 inhibitor caused a prominent cell migration and proliferation, attenuated by Let-7i re-expression. To sum up, the present study revealed the impressive role of Let-7i restoration along with its correlation with KISS1 on melanoma carcinogenicity which may be applicable in future in vivo studies.

MicroRNA-27b inhibits the development of melanoma by targeting MYC

Cutaneous malignant melanoma is a malignancy with one of the fastest increasing incidence rates worldwide; however, the mechanism underlying the occurrence and development of melanoma remains unclear. The aim of the present study was to identify novel biomarkers for the occurrence and development of melanoma. The results of the present study demonstrated that the expression levels of microRNA (miR)-27b were decreased in melanoma tissue samples compared with those in adjacent noncancerous tissue samples and cells according to online and experimental data. By contrast, MYC expression levels were upregulated in melanoma compared with those in adjacent noncancerous tissue samples. miR-27b overexpression significantly inhibited A375 and A2085 melanoma cell DNA synthesis, viability and invasive ability. Dual-luciferase reporter assay results demonstrated that miR-27b inhibited MYC expression through binding to the 3′-untranslated region of MYC mRNA. MYC knockdown in melanoma cells exerted similar effects to those of miR-27b overexpression on DNA synthesis, cell viability and invasive ability; the effects of miR-27b inhibition were significantly reversed by MYC knockdown. In conclusion, the miR-27b/MYC axis may modulate malignant melanoma cell biological behaviors and may be a potential target for melanoma treatment.

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.

Role of microRNAs in Pressure Ulcer Immune Response, Pathogenesis, and Treatment

Pressure ulcers are preventable, yet highly prevalent, chronic wounds that have significant patient morbidity and high healthcare costs. Like other chronic wounds, they are characterized by impaired wound healing due to dysregulated immune processes. This review will highlight key biochemical pathways in the pathogenesis of pressure injury and how this signaling leads to impaired wound healing. This review is the first to comprehensively describe the current literature on microRNA (miRNA, miR) regulation of pressure ulcer pathophysiology.

Nanoparticle-complexed antimiRs for inhibiting tumor growth and metastasis in prostate carcinoma and melanoma

Background

MiRNAs act as negative regulators of gene expression through target mRNA degradation or inhibition of its translation. In cancer, several miRNAs are upregulated and play crucial roles in tumorigenesis, making the inhibition of these oncomiRs an interesting therapeutic approach. This can be achieved by directly complementary single-stranded anti-miRNA oligonucleotides (antimiRs). A major bottleneck in antimiR therapy, however, is their efficient delivery. The nanoparticle formation with polyethylenimine (PEI) may be particularly promising, based on the PEI’s ability to electrostatically interact with oligonucleotides. This leads to their protection and supports delivery. In the present study, we explore for the first time PEI for antimiR formulation and delivery. We use the branched low molecular weight PEI F25-LMW for the complexation of different antimiRs, and analyse tumor- and metastasis-inhibitory effects of PEI/antimiR complexes in different tumor models.

Results

In prostate carcinoma, transfection of antimiRs against miR-375 and miR-141 leads to tumor cell inhibition in 2D- and 3D-models. More importantly, an in vivo tumor therapy study in prostate carcinoma xenografts reveals anti-tumor effects of the PEI/antimiR complexes. In advanced melanoma and metastasis, we identify by a microRNA screen miR-150 as a particularly relevant oncomiR candidate, and validate this result in vitro and in vivo. Again, the systemic application of PEI/antimiR complexes inhibiting this miRNA, or the previously described antimiR-638, leads to profound tumor growth inhibition. These effects are associated with the upregulation of direct miRNA target genes. In a melanoma metastasis mouse model, anti-metastatic effects of PEI/antimiR treatment are observed as well.

Conclusions

We thus describe PEI-based complexes as efficient platform for antimiR therapy, as determined in two different tumor entities using in vivo models of tumor growth or metastasis. Our study also highlights the therapeutic relevance of miR-375, miR-141, miR-150 and miR-638 as target miRNAs for antimiR-mediated inhibition.

Conjunctival Melanoma: Update on Genetics, Epigenetics and Targeted Molecular and Immune-Based Therapies

Purpose

To present the molecular mechanisms involved in the pathogenesis of conjunctival melanoma (CM) and review the existing literature on targeted molecular inhibitors as well as immune checkpoint inhibitors for the management of locally advanced and metastatic disease.

Methods

A comprehensive review of the literature was performed using the keywords "conjunctival melanoma", "immune checkpoint inhibitors", "BRAF inhibitors", "MEK inhibitors", "CTLA4 inhibitors", "PD1 inhibitors", "c-KIT mutations", "BRAF mutations", "NRAS mutations", "dabrafenib", "trametinib", "vemurafenib", "ipilimumab", "pembrolizumab", and "nivolumab". A total of 250 articles were reviewed and 120 were included in this report.

Results

Mutations of mediators in the MAP kinase pathway, such as RAS, BRAF, MEK and ERK, and mutations of the PI3K/AKT/mTOR pathway play a major role in the pathogenesis of conjunctival melanoma. In addition, alterations of c-KIT, NF1, TERT, chemokine receptors as well as chromosomal copy number alterations and micro RNAs are thought to have a causative association with CM development. Targeted molecular inhibitors, such as BRAF and MEK inhibitors, are currently being implemented in the therapy of BRAF-mutated CM. Furthermore, immune checkpoint PD-1 and CTLA4 inhibitors with favorable clinical outcomes in the treatment of cutaneous melanoma have increased recurrence-free survival and reduced metastatic spread in CM cases.

Conclusion

The complex molecular mechanisms that contribute to the development of CM can be targeted both by molecular inhibitors of oncogenic pathways as well as immune checkpoint inhibitors in order to halt progression of the disease and increase survival.

LncRNA LINC00313 Knockdown Inhibits Tumorigenesis and Metastasis in Human Osteosarcoma by Upregulating FOSL2 through Sponging miR-342-3p

PURPOSE

Osteosarcoma (OS) is the most common primary bone tumor, with high morbidity in infants and adolescents. Long noncoding RNA LINC00313 has been found to modulate papillary thyroid cancer tumorigenesis and to be dysregulate in lung cancer. However, the role of LINC00313 in OS has not yet been addressed.

MATERIALS AND METHODS

We evaluated mRNA and protein expression using real-time quantitative PCR and Western blotting. Cell proliferation was evaluated using MTT; apoptosis and autophagy were assessed with flow cytometry, Western blotting, and/or GFP-LC3 assay. Transwell assay was conducted to measure cell migration and invasion. Potential target sites for LINC00313 and miR-342-3p were predicted with starBase v.2.0 and TargetScan Human, and verified using luciferase reporter assay, RNA immunoprecipitation, and RNA pull-down assay. In vivo, xenogeneic tumors were induced with U2OS and MG-63 cells, separately.

RESULTS

LINC00313 was upregulated and miR-342-3p was downregulated in OS tissues and cells. High expression of LINC00313 was associated with shorter overall survival. FOSL2 downregulation and miR-342-3p overexpression suppressed cell proliferation and migratory and invasive abilities while promoting apoptosis and autophagy, all of which were consistent with the effects of LINC00313 knockdown. miR-342-3p, sponged by LINC00313, inversely modulated FOSL2 by targeting MG-63 cells, and FOSL2 expression was positively controlled by LINC00313. LINC00313 knockdown suppressed tumor growth in vivo.

CONCLUSION

LINC00313 is upregulated in OS, and LINC00313 knockdown plays a vital anti-tumor role in OS cell progression through a miR-342-3p/FOSL2 axis. Our study suggests that LINC00313 may be a novel, promising biomarker for diagnosis and prognosis of OS.

Development of synthetic microRNA-214 showing enhanced cytotoxicity and RNase resistance for treatment of canine hemangiosarcoma

MicroRNA-214 (miR-214), a pivotal tumour-suppressive miRNA, is downregulated in canine hemangiosarcoma (HSA) cells. Although these tumour-suppressive miRNAs are potential therapeutic agents, their clinical efficacy may be limited because of their vulnerability to RNase-rich microenvironments and low in vivo transfection rates. We developed synthetic miR-214s with enhanced cytotoxicity, RNase resistance and quantity of miR-214 in/on cells. These synthetic miR-214s were synthesized by various chemical modifications (such as 4'-aminoethyl-2'-fluoro, 2'-fluoro, 2'-O-methyl, phosphorothioate and oligospermine modifications) of the wild-type mature miR-214 sequences. Transfection of HSA cells with synthetic miR-214 (miR-214 5AE) demonstrated significant growth suppressive effect and induced the strongest apoptotic response. Synthetic miR-214s (miR-214 5AE, miR-214 10AE and miR-214 OS) were much more stable than mature miR-214s in foetal bovine serum. Similar to mature miR-214, 5AE and OS suppressed the expression level of COP1 in HSA cells. The quantity of synthetic miR-214s in/on cells was higher than that of mature miR-214. In conclusion, we developed a clinically applicable, synthetic miR-214 5AE that regulates the COP1 protein expression similar to that mediated by mature miR-214. Additionally, miR-214 5AE confers better cytotoxicity, nuclease resistance and transfection rate than mature miR-214. Thus, miR-214 5AE could potentially be a novel miRNA-based chemotherapeutic agent that could improve the prognosis of HSA. Its in vivo effects on canine HSA need to be examined in future.

Molecular expression profiles of selected microRNAs in colorectal adenocarcinoma in patients from south-eastern part of Romania

MicroRNAs (miRNAs) are endogenous, non-coding class of RNAs with functions in the regulation of genes expressions. Dysregulated expressions of miRNAs play important roles in carcinogenesis and cancer progression by targeting various oncogenes and tumor-suppressor genes. miRNAs represent a new field for molecular diagnosis and prognosis of colorectal cancer (CRC) due to their high tissue specificity, their stability, and their dysregulated expression in tumor development.This study aimed to investigate using the qRT-PCR method the expression profile and prognostic value of 11 mature miRNAs in a cohort of 82 Romanian patients diagnosed with CRC. The relationship between the expression levels of selected miRNAs and clinicopathologic features were evaluated using ANOVA and Pearson test. In addition, the receiver operating characteristic (ROC) and area under the curve (AUC) were used to assess the diagnostic values of the miRNAs to discriminate cancerous from non-cancerous states of the samples.The expression levels of miR-30c, miR-144, miR-375, miR-214, and miR-195 in CRC tissue were significantly downregulated (all P < .05; Paired T-Test) than that in normal adjacent tissue sample (NATS), while the expression of miR-141, miR-182, miR-183, miR-21, and miR-370 in CRC tissue were significantly upregulated (all P < .001) than that in NATS. Moreover, the expression levels of miR-182, miR-183, miR-141, and miR-21 were demonstrated to be associated with a gradual increase in fold change expression with depth of tumor invasion (all P < .05), lymph node invasion (all P < .001), and maximal increase with distant metastasis (all P < .001). Moreover, the analysis of ROC curves revealed that AUC (95% CI) of miR-182, miR-183, miR-141, and miR-21 in diagnosis of CRC was 0.76 (0.66-0.87), 0.85 (0.78-0.94), 0.77 (0.62-0.92), 0.83 (0.73-0.90), respectively. The univariate and multivariate Cox-proportional hazard regression for all variables revealed that the nodal status, distant metastasis, miR-21, miR-141, miR-182, and miR-183 were independent prognostic markers of CRC.In conclusion, altered expressions of miR-21, miR-141, miR-182, and miR-183 in CRC varies at different stages of CRC development and may serve as potential diagnosis molecular biomarkers in Romanian patients with CRC. Further investigations are needed to confirm our findings.

Conjunctival Melanoma: Genetic and Epigenetic Insights of a Distinct Type of Melanoma

Conjunctival melanoma (CjM) is a rare, primary cancer of the ocular region. Genetic and epigenetic characteristics of conjunctival melanoma have not been completely elucidated yet. Conjunctival melanoma presents similarities with cutaneous melanoma, with substantial differences in the biological behavior. We reviewed the genetic and epigenetic insights of CjM involved in invasion and metastatic spread. CjM is commonly characterized by mutations of v-raf murine sarcoma viral oncogene homolog B1 (BRAF), neurofibromin 1 (NF1) and telomerase reverse transcriptase (TERT), high expression of mammalian target of rapamycin (mTOR) and heat shock protein 90 (HSP90), frequent phosphatase and tensin homolog (PTEN) loss and upregulation of specific miRNAs. These features should identify CjM as a distinct subset of melanoma with its own profile, which is more similar to cutaneous melanoma than mucosal melanoma and remarkably different from uveal melanoma.

microRNA-374 inhibits proliferation and promotes apoptosis of mouse melanoma cells by inactivating the Wnt signalling pathway through its effect on tyrosinase

Melanoma is one of the most malignant skin tumours with constantly increasing incidence worldwide. Previous studies have demonstrated that microRNA‐374 (miR‐374) is a novel biomarker for cancer therapy. Therefore, this study explores whether miR‐374 targeting tyrosinase (TYR) affects melanoma and its underlying mechanism. We constructed subcutaneous melanoma models to carry out the following experiments. The cells were transfected with a series of miR‐374 mimics, miR‐374 inhibitors or siRNA against TYR. Dual luciferase reporter gene assay was used for the verification of the targeting relationship between miR‐374 and TYR. Reverse transcription quantitative polymerase chain reaction and western blot analysis were conducted to determine the expression of miR‐374, TYR, β‐catenin, B‐cell leukaemia 2 (Bcl‐2), Bcl‐2 associated X protein (Bax), Low‐density lipoprotein receptor‐related protein 6 (LRP6), Leucine‐rich repeat G protein‐coupled receptor 5 (LGR5) and CyclinD1. Cell proliferation, migration, invasion, cell cycle distribution and apoptosis were evaluated using cell counting kit‐8 assay, scratch test, transwell assay and flow cytometry respectively. TYR was proved as a putative target of miR‐374 as the evidenced by the result. It was observed that up‐regulated miR‐374 or down‐regulated TYR increased expression of Bax and decreased expressions of TYR, β‐catenin, LRP6, Bcl‐2, CyclinD1 and LGR5, along with diminished cell proliferation, migration, invasion and enhanced apoptosis. Meanwhile, cells with miR‐374 inhibitors showed an opposite trend. These findings indicated that up‐regulated miR‐374 could inhibit the expression of TYR to suppress cell proliferation, migration, invasion and promote cell apoptosis in melanoma cells by inhibiting the Wnt signalling pathway.

MITF-the first 25 years

In this review, Goding and Arnheiter present the current understanding of MITF's role and regulation in development and disease and highlight key areas where our knowledge of MITF regulation and function is limited.

All transcription factors are equal, but some are more equal than others. In the 25 yr since the gene encoding the microphthalmia-associated transcription factor (MITF) was first isolated, MITF has emerged as a key coordinator of many aspects of melanocyte and melanoma biology. Like all transcription factors, MITF binds to specific DNA sequences and up-regulates or down-regulates its target genes. What marks MITF as being remarkable among its peers is the sheer range of biological processes that it appears to coordinate. These include cell survival, differentiation, proliferation, invasion, senescence, metabolism, and DNA damage repair. In this article we present our current understanding of MITF's role and regulation in development and disease, as well as those of the MITF-related factors TFEB and TFE3, and highlight key areas where our knowledge of MITF regulation and function is limited.

miR-let-7b and miR-let-7c suppress tumourigenesis of human mucosal melanoma and enhance the sensitivity to chemotherapy

Background

Mucosal melanoma with poor prognosis is a common histopathologic subtype of melanoma among Chinese and other Asian peoples. Regulated microRNAs (miRNAs) have been reported as oncogenes or tumour suppressors in melanoma. However, the roles of specific miRNAs in mucosal melanoma remain largely unknown. Here, we aimed to assess the biological functions, molecular mechanisms and clinical potential of miR-let-7b and miR-let-7c in mucosal melanoma.

Methods

The expression of miR-let-7b and miR-let-7c in mucosal melanoma was determined by quantitative polymerase chain reaction (qPCR). Cutoff scores for miR-let-7b and miR-let-7c expressions were calculated through receiver operating characteristic (ROC) curve analysis in 106 mucosal melanoma patients according to recurrence. Correlations of miR-let-7b and miR-let-7c expression with clinicopathological characteristics, disease-free survival (DFS) and clinical benefits after treatment were then statistically analysed. The biological functions and molecular mechanisms of miR-let-7b and miR-let-7c were studied in vitro and in vivo.

Results

The expression of miR-let-7b and miR-let-7c was decreased in 94 cases (88.7%) and 89 cases (84.0%) of 106 mucosal melanoma patients compared with mucosal nevi. A correlation was observed between the expression of miR-let-7b, miR-let-7c and DFS after surgery. In addition, overexpression of miR-let-7b or miR-let-7c inhibited mucosal melanoma cell growth, migration, invasion and metastasis and induced cell apoptosis and cell cycle arrest in vitro and in vivo. Mechanistically, miR-let-7b and miR-let-7c directly targeted metadherin (MTDH) and calumenin (CALU) and suppressed phospho-ERK in mucosal melanoma cells. MTDH and CALU reversed the partial function of miR-let-7b and miR-let-7c in vitro. Furthermore, progression-free survival (PFS) of mucosal melanoma patients upon temozolomide-based and paclitaxel-based chemotherapy was related to miR-let-7b and miR-let-7c expression. Overexpression of miR-let-7b or miR-let-7c in patient-derived xenograft (PDX) models and certain mucosal melanoma cells had better growth inhibition after temozolomide and paclitaxel treatment. MTDH reversed the sensitivity of miR-let-7b and miR-let-7c to paclitaxel in vitro.

Conclusions

Our results suggested that miR-let-7b and miR-let-7c inhibited the recurrence of mucosal melanoma through inhibiting cell growth, migration, invasion and metastasis, inducing cell apoptosis and cell cycle arrest by targeting MTDH and CALU. In addition, miR-let-7b and miR-let-7c increased sensitivity to chemotherapeutic agents by targeting MTDH.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1190-3) contains supplementary material, which is available to authorized users.

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.

The micro RNA hsa-miR-377-3p inhibits tumor growth in malignant melanoma

Background/Aims: Most recently, micro RNAs (miRNAs/miRs) have been suggested to play a key role in various physiological and pathological processes by regulating the expression of specific genes. The influence of miR-377-3p on multitudinous cancer cells has been investigated; however, its function in melanoma remains undiscovered. Armadillo repeat-containing protein 8 (ARMC8), a target of miR-377-3p, plays essential roles in proliferation, differentiation and apoptosis. Our research aimed to detect the specific roles of miR-377-3p in melanoma. Methods: The MiRNA and mRNA expressions were evaluated by a real-time quantitative polymerase chain reaction in the A375 and HEMa-LP cell lines. We predicted the possible interactions between microRNA and mRNAs by bioinformatics database and constructed them with the Cytoscape software. The proliferation and migration activities were investigated using a cell counting kit-8 (CCK8) and wound-healing assay. Validation of the correlation between miR-377-3p and ARMC8 was implemented by the luciferase reporter assay and PCR. Results: The expression of miR-377-3p was found to be lower in malignant melanoma cells. The upregulation of miR-377-3p inhibited the melanoma cell proliferation, migration, and ARMC8 expression. miR-377-3p was identified to bind to the 3′UTR region of ARMC8 directly; this indicated that miR-377-3p suppressed melanoma cell growth partly mediated via the ARMC8 expression. Conclusion: These findings show that miR-377-3p negatively regulates tumor growth in malignant melanoma, which may thus provide a potential biological target for melanoma treatment and subsequently lead to the development of potential treatments.

We have demonstrated that miR-377-3p inhibits melanoma cell growth by binding to the ARMC8 mRNA in the A375 cell line.

MicroRNA-23a inhibits melanoma cell proliferation, migration, and invasion in mice through a negative feedback regulation of sdcbp and the MAPK/ERK signaling pathway

Melanoma is the main cause of death associated with skin cancer. Surgical resection and adjuvant therapy are currently effective treatments, but the recurrence rate is very high. The understanding of microRNA (miR) dynamics after surgical resection of melanoma is essential to accurately explain the changes in the recurrence of melanoma. In this study, we hypothesized that microRNA-23a (miR-23a) affects the cell proliferation, migration, and invasion of melanoma with a mechanism related to SDCBP and the MAPK/ERK signaling pathway. To validate this, we performed a series of experiments in cells of melanoma modeled. Initially, positive expression of SDCBP and morphology of normal and melanoma tissues and cells were observed. Expression of miR-23a, SDCBP, and MAPK/ERK signaling pathway-related genes was identified in melanoma tissues. Melanoma cells transfected with mimic or inhibitor of miR-23a or si-SDCBP were detected to validate effect of miR-23a on SDCBP and the MAPK/ERK signaling pathway. MTT assay, scratch test, transwell assay, and flow cytometry were performed to evaluate cell viability, invasion, metastasis, and apoptosis in vitro, respectively. Tumorigenicity assay in nude mice was conducted to test the tumorigenesis of the transfected cells in vivo. High positive expression of SDCBP and abnormal morphology were observed in melanoma tissues and cells. Reduced expression of miR-23a and increased expression of SDCBP and MAPK/ERK signaling pathway-related genes were identified in the melanoma tissues of melanoma mice. Overexpressed miR-23a dampened SDCBP and the MAPK/ERK signaling pathway. The melanoma cells with overexpressed miR-23a presented ascended cell apoptosis and descended cell proliferation, migration, invasion as well as tumor size. Taken together, our study demonstrated that miR-23a could inhibit the development of melanoma in mice through a negative feedback regulation of SDCBP and the MAPK/ERK signaling pathway. © 2018 IUBMB Life, 71(5):587-600, 2019.

Downregulation of intratumoral expression of miR-205, miR-200c and miR-125b in primary human cutaneous melanomas predicts shorter survival

While only 15–25 percent of melanoma patients develop distant metastasis and die, this disease is still responsible for the majority of skin cancer-related deaths. The availability of adjuvant therapies makes the selection of high-risk patients essential. We evaluated the intratumoral expression of ten miRNAs in primary melanomas in relation to its ability to predict melanoma survival. To this end, we correlated miRNA expression in 132 cryopreserved primary and metastatic tumors with clinicopathological factors and clinical outcome. We found sequential downregulation of intratumoral expression of miR-125b, miR-182, miR-200c and miR-205 over the full spectrum of melanoma progression. Moreover, downregulation of these miRNAs occurred in primary melanomas that further disseminated to distant sites. Furthermore, miR-125b, miR-200c and miR-205 correlated as independent factors with shorter survival. Our in vitro findings demonstrate that loss of miR-205 potentiates the invasive ability of melanoma cells. We conclude that the downregulation of miR-205 in primary melanomas is an intrinsic property that might contribute to distant metastasis. In particular, the interaction of melanoma cells with the extracellular matrix is one of the key mechanisms by which miR-205 influences melanoma metastasis. In conclusion, miR-125b, miR-200c and miR-205 are useful prognostic biomarkers at the time of diagnosis to select high-risk patients.

Melanoma cell-secreted exosomal miR-155-5p induce proangiogenic switch of cancer-associated fibroblasts via SOCS1/JAK2/STAT3 signaling pathway

Background

Cancer-associated fibroblasts (CAFs) have been widely reported to promote tumor angiogenesis. However, the underlying mechanisms of the proangiogenic switch of CAFs remain poorly understood. This study aims to clarify the mechanisms underlying the proangiogenic switch of CAFs.

Methods

NIH/3T3 cells were treated with B16 and B16F10-derived exosomes. Then the CAFs markers and proangiogenic factors were detected by RT-PCR and Western blot. CCK-8 assay, transwell migration assay, tube formation assay, and in vivo Matrigel plug assay were conducted to determine the proangiogenic capability of CAFs. Western blot and AG490 were used to investigate the role of Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) signaling pathway in the proangiogenic switch of CAFs. Bioinformatics analysis, luciferase reporter assay, microRNA mimic and inhibitor, and xenograft models were used to investigate the role of mmu-miR-155-5p (miR-155) in the proangiogenic switch of CAFs.

Results

In this study, we show that melanoma cell-secreted exosomes can induce reprogramming of fibroblasts into CAFs and that exosomal miR-155 can trigger the proangiogenic switch of CAFs. Mechanistically exosomal miR-155 can be delivered into fibroblasts and promote the expression of proangiogenic factors, including vascular endothelial growth factor A (VEGFa), fibroblast growth factor 2 (FGF2), and matrix metalloproteinase 9 (MMP9), by directly targeting suppressor of cytokine signaling 1 (SOCS1). Downregulation of SOCS1 activates JAK2/STAT3 signaling pathway and elevates the expression levels of VEGFa, FGF2, and MMP9 in fibroblasts. Treatment with exosomes containing overexpressed miR-155 can promote angiogenesis, and the reduction of miR-155 in melanoma cell-secreted exosomes alleviates angiogenesis in vitro and in vivo.

Conclusions

These results demonstrate that by promoting the expression of proangiogenic factors in recipient fibroblasts via SOCS1/JAK2/STAT3 signaling pathway, melanoma cell-secreted exosomal miR-155 can induce the proangiogenic switch of CAFs. Although tumor angiogenesis is modulated by various factors, exosomal miR-155 may be a potential target for controlling melanoma angiogenesis and used to set up novel strategies to treat melanoma.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0911-3) contains supplementary material, which is available to authorized users.

Alterations in patient plasma microRNA expression profiles following resection of metastatic melanoma

BACKGROUND AND OBJECTIVES

MicroRNAs (miRs) are noncoding RNAs that regulate protein translation and melanoma progression. Changes in plasma miR expression following surgical resection of metastatic melanoma are under-investigated. We hypothesize differences in miR expression exist following complete surgical resection of metastatic melanoma.

METHODS

Blood collection pre- and post-surgical resection was performed in six individuals with solitary melanoma metastases. miR expression in extracted RNA was quantified using the NanoString nCounter Digital Analyzer.

RESULTS

Pre- and post-surgical plasma samples contained 216 miRs with expression above baseline. Comparison of postsurgical to preresection samples revealed differential expression of 25 miRs: miR-let-7a, miR-let7g, miR-15a, miR-16, miR-22, miR-30b, miR-126, miR-140, miR-145, miR-148a, miR-150-5p, miR-191, miR-378i, miR-449c, miR-494, miR-513b, miR-548aa, miR-571, miR-587, miR-891b, miR-1260a, miR 1268a, miR-1976, miR-4268, miR-4454 (P < 0.05). Utilizing P < 0.0046 as a cutoff to control for one false positive among the 216 miRs revealed that postsurgical melanoma plasma samples had upregulation of miR-1260a (P = 0.0007) and downregulation of miR-150-5p (P = 0.0026) relative to pre-surgical samples.

CONCLUSIONS

Differential expression of miR-150-5p and miR-1260a is present in plasma following surgical resection of metastatic melanoma in this small sample (n = 6) of melanoma patients. Therefore, further investigation of these plasma miRs as noninvasive biomarkers for melanoma is warranted.

Quantification of microRNA-21 and microRNA-125b in melanoma tissue

Although microRNAs (miRNAs) have emerged as potent mediators of melanoma development and progression, a precise understanding of their oncogenic role remains unclear. In this study, we analysed formalin-fixed and paraffin-embedded tissues from two separate melanoma cohorts and from a series of benign melanocytic nevi. Using three different quantification methods [array analysis, quantitative PCR (qPCR) and in-situ hybridization (ISH) quantified by digital image analysis], we found considerable miRNA dysregulation in tumours. Using array analysis, samples mainly clustered according to their biological group (benign vs. malignant) and 77 miRNAs differed significantly between nevi and melanoma samples. Increase of miR-21 and miR-142, and decrease of miR-125b, miR-211, miR-101 and miR-513c in the melanomas were verified in both cohorts using qPCR, whereas the decrease of miR-205 observed with array analysis could not be confirmed using qPCR. ISH with digital quantification showed expression of miR-21 and miR-125b in the melanocytic lesions. miR-21 ISH was increased in melanomas, whereas quantification of miR-125b showed uniform ISH expression across nevi and melanomas. Our results support the important involvement of different miRNAs in melanoma biology and may serve as solid basics for further miRNA investigations in melanoma formalin-fixed and paraffin-embedded tissue. In particular, there is increased expression of miR-21 in melanomas compared with benign nevi.

Identification of micro-RNA expression profile related to recurrence in women with ESMO low-risk endometrial cancer

Background

Actual European pathological classification of early-stage endometrial cancer (EC) may show insufficient accuracy to precisely stratify recurrence risk, leading to potential over or under treatment. Micro-RNAs are post-transcriptional regulators involved in carcinogenic mechanisms, with some micro-RNA patterns of expression associated with EC characteristics and prognosis. We previously demonstrated that downregulation of micro-RNA-184 was associated with lymph node involvement in low-risk EC (LREC). The aim of this study was to evaluate whether micro-RNA signature in tumor tissues from LREC women can be correlated with the occurrence of recurrences.

Methods

MicroRNA expression was assessed by chip analysis and qRT-PCR in 7 formalin-fixed paraffin-embedded (FFPE) LREC primary tumors from women whose follow up showed recurrences (R+) and in 14 FFPE LREC primary tumors from women whose follow up did not show any recurrence (R−), matched for grade and age. Various statistical analyses, including enrichment analysis and a minimum p-value approach, were performed.

Results

The expression levels of micro-RNAs-184, -497-5p, and -196b-3p were significantly lower in R+ compared to R− women. Women with a micro-RNA-184 fold change < 0.083 were more likely to show recurrence (n = 6; 66%) compared to those with a micro-RNA-184 fold change > 0.083 (n = 1; 8%), p = 0.016. Women with a micro-RNA-196 fold change < 0.56 were more likely to show recurrence (n = 5; 100%) compared to those with a micro-RNA-196 fold change > 0.56 (n = 2; 13%), p = 0.001.

Conclusions

These findings confirm the great interest of micro-RNA-184 as a prognostic tool to improve the management of LREC women.

MiR-497-5p, miR-195-5p and miR-455-3p function as tumor suppressors by targeting hTERT in melanoma A375 cells

Background

hTERT gene plays an important role in melanoma, although the specific mechanism involved is unclear. The aim of this study was to screen and identify the relative miRNAs with the regulation of hTERT in melanoma.

Materials and methods

Quantitative real-time polymerase chain reaction (q-PCR) and immunohistochemistry were performed to detect hTERT mRNA and protein expression in 36 formalin-fixed paraffin-embedded melanoma tissues and 36 age- and sex-matched pigmented nevi cases, respectively. Bioinformatics analysis and custom miRNA polymerase chain reaction array were determined for predicting, screening and verifying miRNAs with the regulation of the hTERT gene. To investigate the biological functions, miRNAs mimics or inhibitors were transfected into melanoma A375 cells. The relative expression of miR-497-5p, miR-195-5p, miR-455-3p and hTERT mRNA was determined by q-PCR. The protein expression of hTERT was detected by Western blot. 3-(4,5-Dimethylthiazolyl-2-yl)-2,5-biphenyl tetrazolium bromide and flow cytometry were employed to detect cell proliferation ability, cell apoptosis and cell cycle. Transwell and wound healing assays were used to observe cell invasion and migration abilities. A direct target gene of miRNAs was analyzed by a dual luciferase reporter activity assay.

Results

MiR-497-5p, miR-195-5p, miR-455-3p were significantly downregulated, while hTERT was upregulated in melanoma tissues. hTERT expression level was inversely correlated with miR-497-5p, miR-195-5p and miR-455-3p. Overexpression of miR-497-5p, miR-195-5p and miR-455-3p inhibited A375 cell proliferation, migration and invasion, arrested the cell cycle, induced cell apoptosis and decreased hTERT expression at both mRNA and protein levels. Suppression of miR-497-5p, miR-195-5p and miR-455-3p partially reversed the inhibitory effects. Finally, hTERT was identified as a direct target of miR-497-5p, miR-195-5p and miR-455-3p.

Conclusions

MiR-497-5p, miR-195-5p and miR-455-3p act as tumor suppressors by targeting hTERT in melanoma A375 cells. Therefore, miR-497-5p, miR-195-5p and miR-455-3p could be potential targeted therapeutic choice for melanoma.

Deregulation of miR-183 promotes melanoma development via lncRNA MALAT1 regulation and ITGB1 signal activation

Dysregulation of miR-183 has been recently elucidated in several carcinomas. However, the expression patterns and mechanisms of miR-183 involved in malignant melanoma remain unidentified. Here, we found down-regulation of miR-183 in melanoma tissues and cells. Decreased level of miR-183 was relevant to poor overall survival, while miR-183 up-regulation resulted in a marked suppression of cell growth in vitro and in vivo. We further found that the expression and function of miR-183 were suppressed by MALAT1. Integrin β1 (ITGB1) was then speculated and confirmed as a direct target of miR-183. We also illustrated that MALAT1 may function as a sponge competitive endogenous RNA (ceRNA) for miR-183, and thus regulate the molecular expression of ITGB1. Collectively, we found a new signaling pathway promoting melanoma development by MALAT1-miR-183-ITGB1 axis, which may be clinically valuable as new targets for malignant melanoma therapy.

MicroRNA-150 inhibitors enhance cell apoptosis of melanoma by targeting PDCD4

Malignant melanoma is a tumor with a high mortality rate. Previous studies have demonstrated that the oncogenesis of melanoma is associated with microRNA (miR)-150. However, the role of miR-150 in melanoma and its regulatory mechanisms are still unclear. In the present study, melanoma cancer tissues and adjacent normal tissues were obtained from 20 melanoma patients. The expression level of miR-150 in melanoma tissue and cell lines was detected by reverse transcription-quantitative polymerase chain reaction. miR-150 inhibitors/negative control were transfected into melanoma A375 cells in order to investigate the effects of miR-150 on cell proliferation, apoptosis, cell cycle migration and invasion using a Cell Counting Kit-8, colony formation, Hoechst 33528, flow cytometry, and Transwell assays. The association between miR-150 and programmed cell death protein-4 (PDCD4) was detected by a dual luciferase reporter assay. The functional role of PDCD4 in miR-150-affected melanoma cells was confirmed by small interfering (si)RNA knockdown. Results demonstrated that miR-150 was significantly upregulated and mRNA and protein expressions of PDCD4 were decreased in melanoma cancer tissues as compared with adjacent normal tissues. The level of PDCD4 was inversely associated with the level of miR-150. Transfection of miR-150 inhibitors suppressed cell proliferation, migration, and invasion, while the apoptosis of cells was promoted and G2/M cell arrest was induced. MiR-150 inhibitors enhanced the expression of caspase-8 and p21. The PDCD4 was identified as a direct target gene of miR-150. The effects of miR-150 inhibitors on apoptosis and apoptosis-associated proteins, including caspase-8 and p21, of A375 cells, were reversed following transfection of siRNA-PDCD4. Therefore, miR-150 inhibitors enhance cell apoptosis via upregulation of PDCD4-mediated activation of caspase-8 and p21. These findings demonstrate the potential for a promising therapeutic strategy in the management of melanoma.

Proof-of-concept study: profile of circulating microRNAs in Bovine serum harvested during acute and persistent FMDV infection

Background

Changes in the levels of circulating microRNAs (miRNAs) in the serum of humans and animals have been detected as a result of infection with a variety of viruses. However, to date, such a miRNA profiling study has not been conducted for foot-and-mouth disease virus (FMDV) infection.

Methods

The relative abundance of 169 miRNAs was measured in bovine serum collected at three different phases of FMDV infection in a proof-of-concept study using miRNA PCR array plates.

Results

Alterations in specific miRNA levels were detected in serum during acute, persistent, and convalescent phases of FMDV infection. Subclinical FMDV persistence produced a circulating miRNA profile distinct from cattle that had cleared infection. bta-miR-17-5p was highest expressed during acute infection, whereas bta-miR-31 was the highest during FMDV persistence. Interestingly, miR-1281was significantly down-regulated during both acute and persistent infection. Cattle that cleared infection resembled the baseline profile, adding support to applying serum miRNA profiling for identification of sub-clinically infected FMDV carriers. Significantly regulated miRNAs during acute or persistent infection were associated with cellular proliferation, apoptosis, modulation of the immune response, and lipid metabolism.

Conclusions

These findings suggest a role for non-coding regulatory RNAs in FMDV infection of cattle. Future studies will delineate the individual contributions of the reported miRNAs to FMDV replication, determine if this miRNA signature is applicable across all FMDV serotypes, and may facilitate development of novel diagnostic applications.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-017-0743-3) contains supplementary material, which is available to authorized users.

MicroRNAs-mediated epithelial-mesenchymal transition in fibrotic diseases

MicroRNAs (miRNAs), a large family of small and highly conserved non-coding RNAs, regulate gene expression through translational repression or mRNA degradation. Aberrant expression of miRNAs underlies a spectrum of diseases including organ fibrosis. Recent evidence suggests that miRNAs contribute to organ fibrosis through mediating epithelial-mesenchymal transition (EMT). Alleviation of EMT has been proposed as a promising strategy against fibrotic diseases given the key role of EMT in fibrosis. miRNAs impact the expression of specific ligands, receptors, and signaling pathways, thus modulating EMT and consequently influencing fibrosis. This review summarizes the current knowledge concerning how miRNAs regulate EMT and highlights the specific roles that miRNAs-regulated EMT plays in fibrotic diseases as diverse as pulmonary fibrosis, hepatic fibrosis, renal fibrosis and cardiac fibrosis. It is desirable that a more comprehensive understanding of the functions of miRNAs-regulated EMT will facilitate the development of novel diagnostic and therapeutic strategies for various debilitating organ fibrosis.

Effect of miR-23a on anoxia-induced phenotypic transformation of smooth muscle cells of rat pulmonary arteries and regulatory mechanism

We investigated the possible implication of miR-23a in anoxia-induced phenotypic transformation of the pulmonary arterial smooth muscle and studied the mechanism of upregulation of miR-23a expression in anoxia. The collagenase digestion method was used for preparing rat primary pulmonary artery smooth muscle cell (PASMC) culture. SM-MHC, SM-α-actin, calponin-1 and SM22α protein expression levels were evaluated using western blot analysis after the ASMCs were subjected to anoxia treatment (3% O₂). Transfection with miR-23a mimics were conducted when PASMCs were under normoxia and anoxia conditions. EdU staining was used to detect the proliferative activity of PASMCs. Cells were transfected with HIF-1α specific siRNA under anoxia condition. RT-qPCR was used to detect miR-23a expression in PASMCs. Chromatin immunoprecipitation method was employed to verify the binding sites of HIF-1α. The dual-luciferase reporter gene was used to study the role of HIF-1 and its binding sites. Rat hypoxic pulmonary hypertension models were established to study the expression of miR-23a using RT-qPCR method and to verify the expression of miR-23a in the arteriole of the rat pulmonary. Our results showed that compared with normoxia condition, under anoxia condition (3% O₂), the expression levels of the contractile phenotype marker proteins decreased significantly after 24 and 48 h. The positive rate of the EdU staining increased significantly and the expression of miR-23a increased. Transfection with miR-23a-mimic downregulated the expression of contractile marker proteins and improved the positive rate of the EdU staining under normoxia. Anoxia and transfection with HIF-1α enhanced the activity of the wild-type Luc-miR-23a-1 (WT) reporter gene. We concluded that miR-23a participated in the anoxia-induced phenotypic transformation of PASMCs. Increased expression of miR-23a under anoxia may primarily be due to miR-23a-1 and miR-23a-3 upregulation. The anoxia-induced upregulation of miR-23a was regulated by HIF-1.

MicroRNAs role as potential biomarkers and key regulators in melanoma

Malignant melanoma (MM) is a highly aggressive skin cancer with high incidence worldwide. It originates from melanocytes and is characterized by invasion, early metastasis and despite the use of new drugs it is still characterized by high mortality. Since an early diagnosis determines a better prognosis, it is important to explore novel prognostic markers in the management of patients with MM. microRNAs (miRNAs) are small (∼22 nucleotides) single-stranded non-coding RNAs that negatively regulate the expression of more than 60% of human genes.miRNAs alterations are involved in several cancers, including MM, where a differential expression for some of them has been reported between healthy controls and MM patients. Moreover, since miRNAs are stable and easily detectable in body fluids, they might be considered as robust candidate biomarkers useful to identify risk of MM, to diagnose an early lesion and/or an early metastatic disease. This review highlights the importance of miRNAs as risk factors, prognostic factors and their role as molecular regulator in the development and progression of MM. © 2016 Wiley Periodicals, Inc.

Argonaute Family Protein Expression in Normal Tissue and Cancer Entities

The members of the Argonaute (AGO) protein family are key players in miRNA-guided gene silencing. They enable the interaction between small RNAs and their respective target mRNA(s) and support the catalytic destruction of the gene transcript or recruit additional proteins for downstream gene silencing. The human AGO family consists of four AGO proteins (AGO1-AGO4), but only AGO2 harbors nuclease activity. In this study, we characterized the expression of the four AGO proteins in cancer cell lines and normal tissues with a new mass spectrometry approach called AGO-APP (AGO Affinity Purification by Peptides). In all analyzed normal tissues, AGO1 and AGO2 were most prominent, but marked tissue-specific differences were identified. Furthermore, considerable changes during development were observed by comparing fetal and adult tissues. We also identified decreased overall AGO expression in melanoma derived cell lines compared to other tumor cell lines and normal tissues, with the largest differences in AGO2 expression. The experiments described in this study suggest that reduced amounts of AGO proteins, as key players in miRNA processing, have impact on several cellular processes. Deregulated miRNA expression has been attributed to chromosomal aberrations, promoter regulation and it is known to have a major impact on tumor development and progression. Our findings will further increase our basic understanding of the molecular basis of miRNA processing and its relevance for disease.

MicroRNA-130b promotes lung cancer progression via PPARγ/VEGF-A/BCL-2-mediated suppression of apoptosis

Background

The prognosis of non-small-cell lung cancer (NSCLC) is poor yet mechanistic understanding and therapeutic options remain limited. We investigated the biological and clinical significance of microRNA-130b and its relationship with apoptosis in NSCLC.

Methods

The level of microRNA-130b in relationship with the expression of PPARγ, VEGF-A, BCL-2 and apoptosis were analyzed in 91 lung cancer patient samples using immunohistochemistry and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay on tissue microarrays. Gain and loss-of-function studies were performed to investigate the effects of microRNA-130b, peroxisome proliferator-activated receptor γ (PPARγ) or vascular endothelial growth factor-A (VEGF-A) on biological functions of lung cancer cells using in vitro and in vivo approaches.

Results

MicroRNA-130b up-regulation conferred unfavorable prognosis of lung cancer patients. Notably, microRNA-130b targeted PPARγ and inhibiting microRNA-130b markedly repressed proliferation, invasion and metastasis of lung cancer cells, leading to increased apoptosis. MicroRNA-130b-dependent biologic effects were due to suppression of PPARγ that in turn activated BCL-2, the key mediator of anti-apoptosis. Administration of microRNA-130b mimic to mouse xenografts promoted tumor growth. In vitro and in vivo, miR-130b enrichment associated with down-regulation of PPARγ, up-regulation of VEGF-A and BCL-2, and decreased apoptosis.

Conclusions

The present study demonstrates that microRNA-130b promotes lung cancer progression via PPARγ/VEGF-A/BCL-2-mediated suppression of apoptosis. Targeting microRNA-130b might have remarkable therapeutic potential for lung cancer therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-016-0382-3) contains supplementary material, which is available to authorized users.

MicroRNA-155 targets cyb561d2 in zebrafish in response to fipronil exposure

MicroRNAs (miRNAs), which are a class of small noncoding RNAs, can modulate the expression of many protein-coding genes when an organism is exposed to an environmental chemical. We previously demonstrated that miR-155 was significantly downregulated in adult zebrafish (Danio rerio) in response to fipronil (5-amino-1-[2,6-dichloro-4-(trifluoromethyl) phenyl]-4-[(trifluoromethyl) sulphinyl]-1H-pyrazole-3-carbonitrile) exposure. However, the regulation of this miRNA's predicted target gene cyb561d2, which is a member of the cytochrome b561 (cyt b561) family involved in electron transfer, cell defence, and chemical stress, has not been experimentally validated to date. In this study, we evaluated the effects of fipronil on miR-155 and cyb561d2 in zebrafish. The expression of miR-155 was downregulated, whereas cyb561d2 was upregulated in both mRNA and protein level in a dose-dependent manner upon stimulation of fipronil. The dual luciferase report assay demonstrated that miR-155 interacted with cyb561d2 3'-untranslated regions (3'-UTR). The expression of cyb561d2 was reduced in both mRNA and protein levels when ZF4 cells were transfected with an miR-155 mimic, whereas its expression levels of both mRNA and protein were increased when endogenous miR-155 was inhibited by transfection with an miR-155 inhibitor. The results improved our understanding of molecular mechanism of toxicity upon fipronil exposure, and presents miR-155 as a potential novel toxicological biomarker for chemical exposure. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 877-886, 2016.

MicroRNA dysregulation in melanoma

Melanoma is the deadliest form of skin cancer. Current challenges facing the management of melanoma include accurate prediction of individuals who will respond to adjuvant therapies as well as early detection of recurrences. These and other challenges have prompted investigation into biomarkers that could be used as diagnostic, prognostic and therapeutic aids. MicroRNAs (miRs) are small 19-22 nucleotide RNA inhibitors of protein translation. Over 800 different miRs are present within cells and importantly miR expression profiles may vary across different cells types and stages of malignancy. Unique expression profiles have been described for malignant melanoma; however, this work has yet to be translated into routine clinical practice. We highlight pertinent studies involving common miRs implicated in the oncogenesis of melanoma including miR-21, miR-125b, miR-150, miR-155, miR-205, and miR-211. In particular, emphasis is placed upon differential expression across different stages of melanoma progression, prognostic implications and potential mechanistic involvement. Focused efforts on inhibition of these miRs could be the most efficient method of translating preclinical endeavors into clinically meaningful applications.

Conjunctival malignant melanoma in Denmark: epidemiology, treatment and prognosis with special emphasis on tumorigenesis and genetic profile

Conjunctival malignant melanoma is a rare disease associated with considerable mortality. Most published data have been based on case reports or series of referred patients. In addition, very little is known about the genetic and epigenetic profile of conjunctival melanoma and the resemblance to uveal, cutaneous and mucosal melanoma. The aim was to determine the incidence rate of conjunctival melanoma, and to relate clinicopathological features and treatment to prognosis. A further aim was to determine the prevalence of BRAF mutations in conjunctival melanoma, to determine whether BRAF mutations are early events in pathogenesis, and relate clinicopathological features and prognosis to BRAF-mutation status. Finally, we wanted to identify tumour-specific and prognostic microRNAs in conjunctival melanoma, and to compare these with the microRNA expression of other melanoma subtypes. In order to investigate these rare tumours, we studied all the conjunctival melanomas that had been surgically removed in Denmark over a period of 52 years (1960-2012). Tissue samples, clinical files, pathology reports and follow-up data were collected and re-evaluated. Using droplet digital polymerase chain reaction and immunohistochemistry, we investigated BRAF mutations; and using microRNA expression profiling, we investigated differentially expressed microRNAs. The overall incidence of conjunctival melanoma was 0.5/1 000 000/year, and it increased in Denmark over 52 years. The increase was mainly caused by an increase in older patients (>65 years) and bulbar lesions. Clinicopathological features significantly associated with a poor prognosis were extrabulbar location, involvement of adjacent tissue structures, tumour thickness exceeding 2 mm and local tumour recurrence. Patients undergoing incisional biopsy and/or treatment involving excision without adjuvant therapy fared worse than patients treated with excision and any type of adjuvant treatment. We found that 35% (39/110) of conjunctival melanomas were BRAF-mutated, and the incidence of BRAF mutations was constant over time. BRAF-mutation status corresponded in conjunctival melanoma and paired premalignant lesions. BRAF mutations were more frequent in males, in young patients, and in tumours with a sun-exposed tumour location (bulbar conjunctiva or caruncle), with a mixed or non-pigmented colour, with absence of primary acquired melanosis, and with origin in a nevus. Immunohistochemistry was able to accurately detect BRAF V600E mutations. In univariate analysis, distant metastatic disease was associated with BRAF mutations. No prognostic associations with BRAF mutations were identified in multivariate analyses. MicroRNA expression analysis revealed 25 tumour-specific microRNAs in conjunctival melanoma. Five possibly oncogenic miRNAs (miR-20b-5p, miR-146b-5p, miR-146a-5p, miR-506-3p and miR-509-3p) were up-regulated. Seven microRNAs (miR-30d-5p, miR-138-5p, miR-146a-5p, miR-500a-5p, miR-501-3p, miR-501-5p and miR-502-3p) were significantly and simultaneously up-regulated in both stage T1 and stage T2 tumours, and were associated with increased tumour thickness. The expression of the 25 tumour-specific microRNAs did not differ significantly between conjunctival melanoma and oral or nasal mucosal melanoma. In conclusion, the incidence of conjunctival melanoma increased in the Danish population from 1960 to 2012. From our findings of a distinct pattern of BRAF mutations and differentially expressed microRNAs, it is evident that conjunctival melanoma is closely related to cutaneous and other mucosal melanomas and bears less resemblance to uveal melanomas. This means that conjunctival melanoma patients may benefit from therapies that are effective for cutaneous and mucosal melanoma. Additionally, the identification of several up-regulated microRNAs may prove to be useful as prognostic or therapeutic targets in conjunctival melanoma.

Microphthalmia-associated transcription factor expression levels in melanoma cells contribute to cell invasion and proliferation

Microphthalmia-associated transcription factor (MITF) is a nodal point in melanoma transcriptional network that regulates dozens of genes with critical functions in cell differentiation, proliferation and survival. Highly variable MITF expression levels exist in tumor cell subpopulations conferring marked heterogeneity and plasticity in the tumor tissue. A model has been postulated whereby lower MITF levels favour cell invasion and suppress proliferation, whereas high levels stimulate differentiation and proliferation. Additionally, MITF is considered to be a prosurvival gene and a lineage addiction oncogene in melanoma. Herein, we review how MITF expression may affect the melanoma phenotype with consequences on the survival, invasion and metastasis of melanoma cells, and we discuss the research challenges.

MicroRNA-130b improves renal tubulointerstitial fibrosis via repression of Snail-induced epithelial-mesenchymal transition in diabetic nephropathy

MicroRNA-130b (miR-130b) downregulation has been identified in diabetes, but the role and mechanisms for miR-130b in mediating renal tubulointerstitial fibrosis in diabetic nephropathy (DN) remain unknown. We demonstrated that plasma miR-130b downregulation exhibited clinical and biological relevance as it was linked to increased serum creatinine, β2-microglobulin and proteinuria, increased Snail expression and tubulointerstitial fibrosis in renal biopsies of DN patients. MiR-130b inhibitor caused Snail upregulation and enhanced molecular features of epithelial-to-mesenchymal transition (EMT) in high glucose (30 mM) cultured NRK-52E cells. In contrast, miR-130b mimic downregulated Snail expression and increased epithelial hallmarks. Notably, Snail was identified as an miR-130b direct target and inversely correlated with E-CADHERIN expression. Furthermore, the miR-130b-dependent effects were due to Snail suppression that in turn deregulated E-CADHERIN, VIMENTIN, COLLAGEN IV and α-smooth muscle actin (α-SMA), key mediators of EMT. These effects were reproduced in streptozotocin-induced diabetic rats. Thus, we propose a novel role of the miR-130b-SNAIL axis in fostering EMT and progression toward increased tubulointerstitial fibrosis in DN. Detection of plasma miR-130b and its association with SNAIL can be extrapolated to quantifying the severity of renal tubulointerstitial fibrosis. Targeting miR-130b could be evaluated as a potential therapeutic approach for DN.

MiR-21: an environmental driver of malignant melanoma?

Since the mid-1950’s, melanoma incidence has been rising steadily in industrialized Caucasian populations, thereby pointing to the pivotal involvement of environmental factors in melanomagenesis. Recent evidence underlines the crucial role of microRNA (miR) signaling in cancer initiation and progression. Increased miR-21 expression has been observed during the transition from a benign melanocytic lesion to malignant melanoma, exhibiting highest expression of miR-21. Notably, common BRAF and NRAS mutations in cutaneous melanoma are associated with increased miR-21 expression. MiR-21 is an oncomiR that affects critical target genes of malignant melanoma, resulting in sustained proliferation (PTEN, PI3K, Sprouty, PDCD4, FOXO1, TIPE2, p53, cyclin D1), evasion from apoptosis (FOXO1, FBXO11, APAF1, TIMP3, TIPE2), genetic instability (MSH2, FBXO11, hTERT), increased oxidative stress (FOXO1), angiogenesis (PTEN, HIF1α, TIMP3), invasion and metastasis (APAF1, PTEN, PDCD4, TIMP3). The purpose of this review is to provide translational evidence for major environmental and individual factors that increase the risk of melanoma, such as UV irradiation, chemical noxes, air pollution, smoking, chronic inflammation, Western nutrition, obesity, sedentary lifestyle and higher age, which are associated with increased miR-21 signaling. Exosomal miR-21 induced by extrinsic and intrinsic stimuli may be superimposed on mutation-induced miR-21 pathways of melanoma cells. Thus, oncogenic miR-21 signaling may be the converging point of intrinsic and extrinsic stimuli driving melanomagenesis. Future strategies of melanoma treatment and prevention should thus aim at reducing the burden of miR-21 signal transduction.

Lin28B promotes melanoma growth by mediating a microRNA regulatory circuit

It has been increasingly recognized that microRNAs (miRNAs) are often dysregulated in various human malignancies and can function as oncogenes or tumor-suppressors. However, the potential roles of miRNAs and components of the miRNA biogenesis pathway remain poorly defined in melanoma. Here, we systematically profiled miRNA expression in human melanocytes and melanoma cells, and identified a prominent function of miR-125a-5p in suppressing melanoma growth. Mechanistically, we discovered that Lin28B, a well-characterized inhibitor of let-7 miRNA biogenesis, was a direct target of miR-125a-5p in melanoma. We showed that the Lin28B was aberrantly expressed in a large proportion of melanoma patients and was functionally required for melanoma progression. We further demonstrated the involvement of let-7-dependent mechanism downstream of Lin28B, resulting in the activation of transforming growth factor-β signaling cascade. Collectively, our data implicate Lin28B as a novel oncogene in melanomagenesis by mediating a miRNA regulatory circuit.

Prognostic Value of MicroRNA-182 in Cancers: A Meta-Analysis

OBJECTIVE

MicroRNA-182 (miR-182) exhibits altered expression in various cancers. The aim of this study was to investigate the predictive value of miR-182 expression for cancer patient survival.

METHODS

Eligible studies were identified through multiple search strategies, and the hazard ratios (HRs) for patient outcomes were extracted and estimated. A meta-analysis was performed to evaluate the prognostic value of miR-182.

RESULTS

In total, 14 studies were included. A high miR-182 expression level predicted a worse outcome with a pooled HR of 2.18 (95% CI: 1.53-3.11) in ten studies related to overall survival (OS), especially in Chinese populations. The results of seven studies evaluating disease-free survival/relapse-free survival/recurrence-free interval/disease-specific survival (DFS/RFS/RFI/DSS) produced a pooled HR of 1.77 (95% CI: 0.91-3.43), which was not statistically significant; however, the trend was positive. When disregarding the DSS from one study, the expression of miR-182 was significantly correlated with DFS/RFS/RFI (pooled HR = 2.52, 95% CI: 1.67-3.79).

CONCLUSIONS

High miR-182 expression is associated with poor OS and DFS/RFS/RFI in some types of cancers, and miR-182 may be a useful prognostic biomarker for predicting cancer prognosis. However, given the current insufficient relevant data, further clinical studies are needed.

MicroRNA profiling in intraocular medulloepitheliomas

Purpose

To study the differential expression of microRNA (miRNA) profiles between intraocular medulloepithelioma (ME) and normal control tissue (CT).

Material and Methods

Total RNA was extracted from formalin fixed paraffin embedded (FFPE) intraocular ME (n=7) and from age matched ciliary body controls (n=8). The clinical history and phenotype was recorded. MiRNA profiles were determined using the Affymetrix GeneChip miRNA Arrays analyzed using expression console 1.3 software. Validation of significantly dysregulated miRNA was confimed by quantitaive real-time PCR. The web-based DNA Intelligent Analysis (DIANA)-miRPath v2.0 was used to perform enrichment analysis of differentially expressed (DE) miRNA gene targets in Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway.

Results

The pathologic evaluation revealed one benign (benign non-teratoid, n=1) and six malignant tumors (malignant teratoid, n=2; malignant non-teratoid, n = 4). A total of 88 miRNAs were upregulated and 43 miRNAs were downregulated significantly (P<0.05) in the tumor specimens. Many of these significantly dysregulated miRNAs were known to play various roles in carcinogenesis and tumor behavior. RT-PCR validated three significantly upregulated miRNAs and three significantly downregulated miRNAs namely miR-217, miR-216a, miR-216b, miR-146a, miR-509-3p and miR-211. Many DE miRNAs that were significant in ME tumors showed dysregulation in retinoblastoma, glioblastoma, and precursor, normal and reactive human cartilage. Enriched pathway analysis suggested a significant association of upregulated miRNAs with 15 pathways involved in prion disease and several types of cancer. The pathways involving significantly downregulated miRNAs included the toll-like receptor (TLR) (p<4.36E-16) and Nuclear Factor kappa B (NF-κB) signaling pathways (p<9.00E-06).

Conclusions

We report significantly dysregulated miRNAs in intraocular ME tumors, which exhibited abnormal profiles in other cancers as well such as retinoblastoma and glioblastoma. Pathway analysis of all dysregulated miRNAs shared commonalities with other cancer pathways.

OncomiR miR-96 and miR-182 promote cell proliferation and invasion through targeting ephrinA5 in hepatocellular carcinoma

EphrinA5, a member of the ephrinA subclass, is downregulated in hepatocellular carcinoma (HCC) and acts as a tumor suppressor. However, the upstream regulation mechanism of ephrinA5 remains unclear. In this study, we tried to identify and characterize the roles of miR-96 and miR-182 in the regulation of ephrinA5 expression in HCC. The expression levels of miR-96 and miR-182 were examined in 47 paired HCC and para-tumoral liver tissues using quantitative real-time RT-PCR. The luciferase reporter assay and western blotting were employed to dissect the association between miR-96/182 and ephrinA5 expression. Moreover, cells were treated with synthetic miR-96/182 precursors and inhibitors to assess their effects on HCC cell growth and migration. It was found that both miR-96 and miR-182 were upregulated in HCC compared to para-tumoral normal tissues. The expression of miR-96 and miR-182 was inversely associated with ephrinA5 protein levels. Furthermore, both miR-96 and miR-182 directly targeted the 3'UTR of the ephrinA5 mRNA and suppressed protein translation. The suppression of miR-96 and miR-182 led to reduced HCC cell proliferation and migration by negatively regulating ephrinA5 expression. In conclusion, miR-96 and miR-182 may act as oncomiRs in HCC by suppressing the expression of ephrinA5 and may play important roles in hepatocarcinogenesis. © 2015 Wiley Periodicals, Inc.

MiR-124 governs glioma growth and angiogenesis and enhances chemosensitivity by targeting R-Ras and N-Ras

BACKGROUND

Glioma is one of the most aggressive and lethal human brain tumors. Accumulating evidence shows that microRNAs play important roles in cancers, including glioma. Previous studies reported that miR-124 levels were downregulated in glioma specimens. Here, we further investigate the potential role of miR-124 in glioma.

METHODS

The expression levels of miR-124 were detected in glioma specimens by quantitative reverse transcriptase PCR. The direct targets of miR-124 were identified by bioinformatics analysis and were further validated by immunoblotting and luciferase reporter assay. The effects of miR-124 on glioma cell proliferation and chemosensitivity to temozolomide were analyzed by Cell-Counting Kit 8 assay. Apoptosis was evaluated by fluorescence activated cell sorting analysis. A xenograft model was used to study the effect of miR-124 on tumor growth and angiogenesis.

RESULTS

Expression levels of miR-124 were greatly downregulated in glioma specimens. related Ras viral oncogene homolog (R-Ras) and neuroblastoma Ras viral oncogene homolog (N-Ras) were identified as direct targets of miR-124. MiR-124 inhibited glioma cell growth, invasion, angiogenesis, and tumor growth and increased chemosensitivity to temozolomide treatment by negatively regulating the Ras family and its downstream signaling pathways: phosphatidylinositol-3 kinase/Akt and Raf/extracellular signal-regulated kinase 1/2. Furthermore, overexpression of R-Ras rescued the inhibitory effects of miR-124. Meanwhile, overexpression of R-Ras and N-Ras restored miR-124-inhibited vascular endothelial growth factor (VEGF) transcription activation. In clinical glioma specimens, protein levels of R-Ras and N-Ras were upregulated and inversely correlated with miR-124 expression levels.

CONCLUSIONS

Taken together, these results revealed that miR-124 levels in tumor tissues are associated with glioma occurrence, angiogenesis, and chemoresistance and that miR-124 may be used as a new diagnostic marker and therapeutic target for glioma in the future.

The role of microRNAs in melanoma

Melanoma is the most dangerous form of skin cancer, being largely resistant to conventional therapies at advanced stages. Understanding the molecular mechanisms behind this disease might be the key for the development of novel therapeutic strategies. MicroRNAs (miRNAs) are small non-coding RNAs that post-transcriptionally control gene expression, thereby regulating various cellular signaling pathways involved in the initiation and progression of different cancer types, including melanoma. In this review, we summarize approaches for the identification of candidate miRNAs and their target genes and review the functions of miRNAs in melanoma. Finally, we highlight the recent progress in pre-clinical use of miRNAs as prognostic markers and therapeutic targets.