miRNA Expression Profiling in Melanocytes and Melanoma Cell Lines Reveals miRNAs Associated with Formation and Progression of Malignant Melanoma

Metastatic melanoma: An integrated analysis to identify critical regulators associated with prognosis, pathogenesis and targeted therapies

Metastatic melanoma causes a high rate of mortality. We conducted an integrated analysis to identify critical regulators associated with the prognosis, pathogenesis, and targeted therapies of metastatic-melanoma. A microarray dataset, GSE15605, including 12 metastatic-melanoma and sixteen normal skin (NS) samples, were obtained from the GEO database. After exploration of DEGs of NS and metastatic-melanoma, identification of relevant transcription factors (TFs) and kinases, the Gene Ontology (GO), and pathways analyses of DEGs were performed. Protein-protein interaction (PPI) networks were evaluated by the STRING and Cytoscape. Subsequently, the hub genes were selected using GEPIA. Survival analysis was performed using the TCGA. To identify microRNA and lncRNA DEGs of the melanoma-associated genes miRwalk and FANTOM6 were employed. In metastatic-melanoma samples 285 and 1173 genes were up and down-regulated, respectively. The upregulated genes were mostly involved in granulocyte chemotaxis, positive regulation of calcium ion transmembrane transport, and melanin biosynthetic process. Five hub genes including CXCL11, ICAM1, LEF1, MITF, and STAT1 were identified, SUZ12, SOX2, TCF3, NANOG, and SMAD4 were determined as the most significant TFs in metastatic-melanoma. Furthermore, CDK2, GSK3B, CSNK2A1, and CDK1 target the highest amounts of genes associated with disease. The DGIdb analysis results show the match drugs for five hub genes. MiRNAs analysis revealed hsa-miR-181c-5p, hsa-miR-30b-3p, hsa-miR-3680-3P, hsa-miR-4659a-3p, hsa-miR-4687-3P, and hsa-miR-6808-3P could regulate the hub genes, whereas RP11-553K8.5 and SRP14-AS1 were identified as the top significant lncRNA. The items recognized in the current study can be used as potential biomarkers for diagnostic, predictive, and might helpful to develop targeted combined therapies.

Non-coding RNAs in BRAF-mutant melanoma: targets, indicators, and therapeutic potential

Melanoma, a highly aggressive skin cancer, is often driven by BRAF mutations, such as the V600E mutation, which promotes cancer growth through the MAPK pathway and contributes to treatment resistance. Understanding the role of non-coding RNAs (ncRNAs) in these processes is crucial for developing new therapeutic strategies. This review aims to elucidate the relationship between ncRNAs and BRAF mutations in melanoma, focusing on their regulatory roles and impact on treatment resistance. We comprehensively reviewed current literature to synthesize evidence on ncRNA-mediated regulation of BRAF-mutant melanoma and their influence on therapeutic responses. Key ncRNAs, including microRNAs and long ncRNAs, were identified as significant regulators of melanoma development and therapy resistance. MicroRNAs such as miR-15/16 and miR-200 families modulate critical pathways like Wnt signaling and melanogenesis. Long ncRNAs like ANRIL and SAMMSON play roles in cell growth, invasion, and drug susceptibility. Specific ncRNAs, such as BANCR and RMEL3, intersect with the MAPK pathway, highlighting their potential as therapeutic targets or biomarkers in BRAF-mutant melanoma. Additionally, ncRNAs involved in drug resistance, such as miR-579-3p and miR-1246, target processes like autophagy and immune checkpoint regulation. This review highlights the pivotal roles of ncRNAs in regulating BRAF-mutant melanoma and their contribution to drug resistance. These findings underscore the potential of ncRNAs as biomarkers and therapeutic targets, paving the way for innovative treatments to improve outcomes for melanoma patients.

Integrative analysis of miRNA expression data reveals a minimal signature for tumour cells classification

MicroRNAs (miRNAs) are pivotal biomarkers for cancer screening. Identifying distinctive expression patterns of miRNAs in specific cancer types can serve as an effective strategy for classification and characterization. However, the development of a minimal signature of miRNAs for accurate cancer classification remains challenging, hindered by the lack of integrated approaches that systematically analyse miRNA expression levels of miRNAs alongside their associated biological pathways. In this study, we present a comprehensive integrative approach that utilizes transcriptomic data from lung, breast, and melanoma cancer cell lines to identify specific expression patterns. By combining bioinformatics, dimensionality reduction techniques, machine learning, and experimental validation, we pinpoint miRNAs linked to critical biological pathways. Our results demonstrate a highly significant differentiation of cancer types, achieving 100 % classification accuracy with minimal training time using a streamlined miRNA signature. Validation of the miRNA profile confirms that each of the three identified miRNAs regulates distinct biological pathways with minimal overlap. This specificity highlights their unique roles in tumour biology and set the stage for further exploration of miRNAs interactions and their contributions to tumourigenesis across diverse cancer types. Our work paves the way for multi-cancer classification, emphasizing the transformative potential of miRNA research in oncology. Beyond advancing the understanding of tumour biology, our step-by-step guide offers a robust tool for a wide range of users to investigate precise diagnostics and promising therapeutic strategies.

Knowledge graph and frontier trends in melanoma-associated ncRNAs: a bibliometric analysis from 2006 to 2023

Objectives

Malignant melanoma (MM) is a highly malignant skin tumor. Although research on non-coding RNAs (ncRNAs) of MM has advanced swiftly in recent years, no specific bibliometric analyses have been conducted on this topic. The present study aims to summarize the knowledge graphs and frontier trends and to provide new perspectives and direction of collaboration for researchers.

Method

Research data on melanoma and ncRNA published from January 1, 2006 to October 9, 2023 were retrieved and extracted from Web of Science. R Studio (Version 4.3.1), Scimago Graphica (Version 1.0.36), VOSviewer version (1.6.19), and Citespace (6.2.4R) were used to analyze the publications, countries, journals, institutions, authors, keywords, references, and other relevant data and to build collaboration network graphs and co-occurrence network graphs accordingly.

Results

A total of 1,222 articles were retrieved, involving 4,894 authors, 385 journals, 43,220 references, 2413 keywords, and 1,651 institutions in 47 countries. The average annual growth rate in the number of articles was 25.02% from 2006 to 2023; among all the journals, Plos One had the highest number of publications and citations, which are 42 publications and 2,228 citations, respectively. Chinese researchers were the most prolific publishers in this field, having published a total of 657 articles, among which 42 were published by Shanghai Jiao Tong University, which was the most productive institution. In recent years, the most explored keywords included long non-coding RNAs, immunotherapy, and exosm. According to the timeline chart of reference co-citation, "functional role" has been the most explored hotspot since 2015, and human cancer is a newly emerged hotspot after 2021.

Conclusion

Through a bibliometric analysis, this study included all publications on ncRNAs and melanoma that were published in English from 2006 to 2023 in Web of Science to analyze the trends in the number of publications, international research focuses, and the direction of collaboration. The results of this study may provide information on knowledge graph, frontier trends and identify research topics in melanoma. More current research proved that ncRNA plays a crucial role in the biological behavior of melanoma including proliferation, invasion, metastasis, drug resistance, etc. With the development of research on ncRNA and melanoma, ncRNA may great potential in development of early diagnosis, targeted therapy and efficacy evaluation in the future. The results of this study also provide new perspectives and research partners for researchers in this field.

Preadipocytes potentiate melanoma progression and M2 macrophage polarization in the tumor microenvironment

Melanoma, the deadliest skin cancer, originates from epidermal melanocytes. The influence of preadipocytes on melanoma is less understood. We co-cultured mouse melanoma B16 cells with 3T3L1 preadipocytes to form mixed spheroids and observed increased melanoma proliferation and growth compared to B16-only spheroids. Metastasis-related proteins YAP, TAZ, and PD-L1 levels were also higher in mixed spheroids. Treatment with exosome inhibitor GW4869 halted melanoma growth and reduced expression of these proteins, suggesting exosomal crosstalk between B16 and 3T3L1 cells. MiR-155 expression was significantly higher in mixed spheroids, and GW4869 reduced its levels. Additionally, co-culturing with Raw264.7 macrophage cells increased M2 markers IL-4 and CD206 in Raw264.7 cells, effects that were diminished by GW4869. These results indicate that preadipocytes may enhance melanoma progression and metastasis via exosomal interactions.

Molecular Susceptibility and Treatment Challenges in Melanoma

Melanoma is the most aggressive subtype of cancer, with a higher propensity to spread compared to most solid tumors. The application of OMICS approaches has revolutionized the field of melanoma research by providing comprehensive insights into the molecular alterations and biological processes underlying melanoma development and progression. This review aims to offer an overview of melanoma biology, covering its transition from primary to malignant melanoma, as well as the key genes and pathways involved in the initiation and progression of this disease. Utilizing online databases, we extensively explored the general expression profile of genes, identified the most frequently altered genes and gene mutations, and examined genetic alterations responsible for drug resistance. Additionally, we studied the mechanisms responsible for immune checkpoint inhibitor resistance in melanoma.

Construction and optimization of multi-platform precision pathways for precision medicine

In the enduring challenge against disease, advancements in medical technology have empowered clinicians with novel diagnostic platforms. Whilst in some cases, a single test may provide a confident diagnosis, often additional tests are required. However, to strike a balance between diagnostic accuracy and cost-effectiveness, one must rigorously construct the clinical pathways. Here, we developed a framework to build multi-platform precision pathways in an automated, unbiased way, recommending the key steps a clinician would take to reach a diagnosis. We achieve this by developing a confidence score, used to simulate a clinical scenario, where at each stage, either a confident diagnosis is made, or another test is performed. Our framework provides a range of tools to interpret, visualize and compare the pathways, improving communication and enabling their evaluation on accuracy and cost, specific to different contexts. This framework will guide the development of novel diagnostic pathways for different diseases, accelerating the implementation of precision medicine into clinical practice.

Emerging role of microRNAs as regulators of protein kinase C substrate MARCKS and MARCKSL1 in cancer

MicroRNAs (miRNAs) have emerged as pivotal regulators of gene expression, playing essential roles in diverse cellular processes, including the development and progression of cancer. Among the numerous proteins influenced by miRNAs, the MARCKS/MARCKSL1 protein, a key regulator of cellular cytoskeletal dynamics and membrane-cytosol communication, has garnered significant attention due to its multifaceted involvement in various cancer-related processes, including cell migration, invasion, metastasis, and drug resistance. Motivated by the encouraging early clinical success of peptides targeting MARCKS in several pathological conditions, this review article delves into the intricate interplay between miRNAs and the MARCKS protein in cancer. Herein, we have highlighted the latest findings on specific miRNAs that modulate MARCKS/MARCKSL1 expression, providing a comprehensive overview of their roles in different cancer types. We have underscored the need for in-depth investigations into the therapeutic feasibility of targeting the miRNA-MARCKS axis in cancer, taking cues from the successes witnessed in related fields. Unlocking the full potential of miRNA-mediated MARCKS regulation could pave the way for innovative and effective therapeutic interventions against various cancer types.

Validation of a microRNA liquid biopsy assay for diagnosis and risk stratification of invasive cutaneous melanoma

BACKGROUND

Noninvasive molecular biomarkers are needed to improve the early, accurate and precise diagnosis of invasive cutaneous melanoma.

OBJECTIVES

To independently validate a previously identified circulating microRNA signature of melanoma (MEL38), and, secondly, to develop a complementary microRNA signature, optimized for prognostication.

PATIENTS AND METHODS

MicroRNA expression profiling was performed on plasma samples from a multicentre observational case-control study, involving patients with primary or metastatic melanoma, melanoma in situ, nonmelanoma skin cancer, or benign naevi. MicroRNA profiles from patients with length of survival, treatment and sentinel lymph node biopsy (SLNB) data were used to develop the prognostic signature. The primary outcome of interest for MEL38 was its association with melanoma status, including area under the curve, binary diagnostic sensitivity and specificity, and incidence-adjusted positive and negative predictive values. The prognostic signature was assessed using rates of survival per risk group and relationship to conventional predictors of outcome.

RESULTS

Circulating microRNA profiles of 372 patients with invasive melanoma and 210 control individuals were generated. The average age of all participants was 59 years; 49% were male. A MEL38 score > 5.5 indicated the presence of invasive melanoma. Overall, 551/582 (95%) of patients were correctly diagnosed, with 93% sensitivity and 98% specificity. MEL38 score ranged from 0 to 10 with an area under the curve of 0.98 (95% confidence interval 0.97-0.99, P < 0.001). A novel prognostic 12-microRNA signature (MEL12) developed from 232 patients identified low-, standard- or high-risk groups, with 94%, 78% and 58% rates of 10-year melanoma-specific survival, respectively (log-rank P < 0.001). MEL12 prognostic risk groups were significantly associated with clinical staging (χ2, P < 0.001) and SLNB status (P = 0.027). Patients who were classified as high risk by MEL12 were approximately three times more likely to have melanoma detected in their sentinel lymph nodes compared to low-risk patients.

CONCLUSIONS

The circulating MEL38 signature may assist in diagnosing patients with invasive melanoma vs. other conditions associated with a lower - or negligible - risk of mortality. A complementary and prognostic MEL12 signature is predictive of SLNB status, clinical stage and probability of survival. Plasma microRNA profiling may help to optimize existing diagnostic pathways as well as enable personalized, risk-informed melanoma treatment decisions.

Noncoding RNA circuitry in melanoma onset, plasticity, and therapeutic response

Melanoma, the cancer of the melanocyte, is the deadliest form of skin cancer with an aggressive nature, propensity to metastasize and tendency to resist therapeutic intervention. Studies have identified that the re-emergence of developmental pathways in melanoma contributes to melanoma onset, plasticity, and therapeutic response. Notably, it is well known that noncoding RNAs play a critical role in the development and stress response of tissues. In this review, we focus on the noncoding RNAs, including microRNAs, long non-coding RNAs, circular RNAs, and other small RNAs, for their functions in developmental mechanisms and plasticity, which drive onset, progression, therapeutic response and resistance in melanoma. Going forward, elucidation of noncoding RNA-mediated mechanisms may provide insights that accelerate development of novel melanoma therapies.

A Tumor and Immune-Related Micro-RNA Signature Predicts Relapse-Free Survival of Melanoma Patients Treated with Ipilimumab

Despite the unprecedented advances in the treatment of melanoma with immunotherapy, there continues to be a major need for biomarkers of clinical benefits and immune resistance associated with immune checkpoint inhibitors; microRNA could play a vital role in these efforts. This study planned to identify differentially expressed miRNA molecules that may have prognostic value for clinical benefits. Patients with surgically operable regionally advanced melanoma were treated with neoadjuvant ipilimumab (10 mg/kg intravenously every 3 weeks × two doses) bracketing surgery. Tumor biospecimens were obtained at baseline and surgery, and microRNA (miRNA) expression profiling was performed on the tumor biopsies. We found that an expression profile consisting of a 4-miRNA signature was significantly associated with improved relapse-free survival (RFS). The signature consisted of biologically relevant molecules previously reported to have prognostic value in melanoma and other malignancies, including miR-34c, miR-711, miR-641, and miR-22. Functional annotation analysis of target genes for the 4-miRNA signature was significantly enriched for various cancer-related pathways, including cell proliferation regulation, apoptosis, the MAPK signaling pathway, and the positive regulation of T cell activation. Our results presented miRNAs as potential biomarkers that can guide the treatment of melanoma with immune checkpoint inhibitors. These findings warrant further investigation in relation to CTLA4 blockade and other immune checkpoint inhibitors. ClinicalTrials.gov NCT00972933.

MicroRNA as a Diagnostic Tool, Therapeutic Target and Potential Biomarker in Cutaneous Malignant Melanoma Detection—Narrative Review

Melanoma is the most serious type of skin cancer, causing a large majority of deaths but accounting for only ~1% of all skin cancer cases. The worldwide incidence of malignant melanoma is increasing, causing a serious socio-economic problem. Melanoma is diagnosed mainly in young and middle-aged people, which distinguishes it from other solid tumors detected mainly in mature people. The early detection of cutaneous malignant melanoma (CMM) remains a priority and it is a key factor limiting mortality. Doctors and scientists around the world want to improve the quality of diagnosis and treatment, and are constantly looking for new, promising opportunities, including the use of microRNAs (miRNAs), to fight melanoma cancer. This article reviews miRNA as a potential biomarker and diagnostics tool as a therapeutic drugs in CMM treatment. We also present a review of the current clinical trials being carried out worldwide, in which miRNAs are a target for melanoma treatment.

Role of miR‑200 family in brain metastases: A systematic review

Brain metastasis (BM) represents the single most severe neurological complication of systemic cancer. The prognosis of patients with BM is poor, irrespective of the implemented treatment. The present study performed a systematic review of the literature using three online databases (PubMed, Scopus and Web of Science). Recently, a number of small RNA molecules, the microRNAs (miRNAs/miRs), have attracted increasing scientific attention. Members of the miR-200 family, which includes five miRNAs (miR-141, miR-200a, miR-200b, miR-200c and miR-429) appear to play pivotal roles in cancer initiation and metastasis. Indeed, a systematic review of the pertinent literature revealed that miR-200 family members regulate the brain metastatic cascade, particularly by modulating epithelial-to-mesenchymal transition. That holds true for the major representatives of BM, including lung and breast cancer, as well as for other less frequent secondary lesions originating from melanoma and the gastrointestinal tract. Therefore, the miRNAs may serve as potential diagnostic and/or prognostic markers, and under specific circumstances, as invaluable therapeutic targets. However, the available clinical evidence is relatively limited. A number of studies have suggested that the miR-200 family members are accurate prognostic markers of survival and resistance to chemotherapy in patients with breast cancer. Similarly, they may prove helpful in differentiating a metastatic lesion from a malignant glioma, or a hemangioblastoma from a renal cell carcinoma in patients with von Hippel Lindau syndrome, based on a cerebrospinal fluid sample. However, currently, there is no known therapeutic role for miR-200 family members in the setting of BM.

Role of miRNA in Melanoma Development and Progression

Melanoma is one of the most aggressive and progressive skin cancers. It develops from normal pigment-producing cells known as melanocytes, so it is important to know the mechanism behind such transformations. The study of metastasis mechanisms is crucial for a better understanding the biology of neoplastic cells. Metastasis of melanoma, or any type of cancer, is a multi-stage process in which the neoplastic cells leave the primary tumour, travel through the blood and/or lymphatic vessels, settle in distant organs and create secondary tumours. MicroRNA (miRNA) can participate in several steps of the metastatic process. This review presents the role of miRNA molecules in the development and progression as well as the immune response to melanoma.

MicroRNAs: Emerging players in the pathogenesis of vitiligo

Vitiligo is an autoimmune skin disease characterized by presence of pale patchy areas of depigmentation. MicroRNAs (miRNAs) are important regulators of gene expression and play significant roles in diverse biological and pathological processes. Accumulating evidence has shown that miRNAs were differentially expressed in skin lesions and peripheral blood mononuclear cells of patients with vitiligo. In particular, miRNAs are significantly correlated with the development and progression of vitiligo. The abundance of some miRNAs in serum was also correlated with the vitiligo lesion severity, indicating that miRNAs might serve as prognostic biomarkers. Importantly, the direct involvement of miRNAs in the pathogenesis of vitiligo has been demonstrated. For example, increased expression of miR-25 contributes to vitiligo through promoting the dysfunction and oxidative stress-induced destruction of melanocytes. However, there are limited studies on the function and mechanism of deregulated miRNAs in vitiligo. Further studies are required to establish clinical applications of miRNAs for vitiligo. More in-depth investigations of miRNAs are needed for the understanding of the pathogenesis of vitiligo and the development of novel therapeutic targets. This present review summarizes the current literature on the deregulation and pathogenic roles of miRNAs in vitiligo. We also highlight the potential clinical applications of miRNAs in patients with vitiligo.

Identification and characterization of novel CD274 (PD-L1) regulating microRNAs and their functional relevance in melanoma

BACKGROUND

Immune checkpoint inhibitors directed against programmed cell death 1 (PDCD1/PD1) receptor and programmed cell death-ligand 1 (CD274/PD-L1) have been recently successfully implemented for the treatment of many cancers, but the response rate of tumour patients is still limited due to intrinsic and acquired resistances. However, the underlying molecular mechanisms of this limited response have still to be defined in detail. The aim of this study is to uncover processes inhibiting PDCD1/CD274 expression thereby enhancing anti-tumour immune responses. The identification and characterization of microRNAs (miRNAs) targeting the 3'-untranslated region (3'-UTR) as well as the coding sequence (CDS) of CD274 will provide the basis for a new drug development.

METHODS

Human melanoma cell lines and tissue samples were subjected to mRNA and/or protein expression analysis using qPCR, Western blot, flow cytometry, and/or immunohistochemistry. The data were correlated to clinical parameters. MiRNA trapping by RNA in vitro affinity purification (miTRAP) technology in combination with small RNA sequencing and different bioinformatics tools were employed to identify CD274-regulating miRNAs.

RESULTS

Screening based on miTRAP in combination with RNAseq identified a large number of novel CD274-regulating candidate miRNAs, from which eight selected miRNAs were functionally validated. Five out of eight miRNAs were able to significantly reduce CD274 surface expression indicating that these miRNAs directly bind to the 3'-UTR or CDS of the CD274 gene. The miRNA-mediated inhibition of CD274 expression was accompanied by an increased T cell recognition. Furthermore, an inverse expression of three CD274-regulating miRNAs and CD274 was demonstrated in melanoma lesions. A CD274 miRNA score was generated, which was associated with disease progression and reduced survival of melanoma patients.

CONCLUSIONS

These data revealed a novel mechanism that miRNAs targeting the CDS of immune checkpoint genes are functional, have prognostic relevance, and also the potential for the development of novel miRNA-based therapies.

The Role, Significance, and Association of MicroRNA-10a/b in Physiology of Cancer

MicroRNAs (miRNAs) are small non-coding RNAs that regulate the translation of mRNA and protein, mainly at the posttranscriptional level. Global expression profiling of miRNAs has demonstrated a broad spectrum of aberrations that correlated with several diseases, and miRNA- 10a and miRNA-10b were the first examined miRNAs to be involved in abnormal activities upon dysregulation, including many types of cancers and progressive diseases. It is expected that the same miRNAs behave inconsistently within different types of cancer. This review aims to provide a set of information about our updated understanding of miRNA-10a and miRNA-10b and their clinical significance, molecular targets, current research gaps, and possible future applications of such potent regulators.

In Vivo miRNA Decoy Screen Reveals miR-124a as a Suppressor of Melanoma Metastasis

Melanoma is a highly prevalent cancer with an increasing incidence worldwide and high metastatic potential. Brain metastasis is a major complication of the disease, as more than 50% of metastatic melanoma patients eventually develop intracranial disease. MicroRNAs (miRNAs) have been found to play an important role in the tumorigenicity of different cancers and have potential as markers of disease outcome. Identification of relevant miRNAs has generally stemmed from miRNA profiling studies of cells or tissues, but these approaches may have missed miRNAs with relevant functions that are expressed in subfractions of cancer cells. We performed an unbiased in vivo screen to identify miRNAs with potential functions as metastasis suppressors using a lentiviral library of miRNA decoys. Notably, we found that a significant fraction of melanomas that metastasized to the brain carried a decoy for miR-124a, a miRNA that is highly expressed in the brain/neurons. Additional loss- and gain-of-function in vivo validation studies confirmed miR-124a as a suppressor of melanoma metastasis and particularly of brain metastasis. miR-124a overexpression did not inhibit tumor growth in vivo, underscoring that miR-124a specifically controls processes required for melanoma metastatic growth, such as seeding and growth post-extravasation. Finally, we provide proof of principle of this miRNA as a promising therapeutic agent by showing its ability to impair metastatic growth of melanoma cells seeded in distal organs. Our efforts shed light on miR-124a as an antimetastatic agent, which could be leveraged therapeutically to impair metastatic growth and improve patient survival.

A Concise Review of MicroRNA-383: Exploring the Insights of Its Function in Tumorigenesis

MicroRNAs (miRNAs) are small noncoding RNAs that commonly have 18-22 nucleotides and play important roles in the regulation of gene expression via directly binding to the 3'-UTR of target mRNAs. Approximately 50% of human genes are regulated by miRNAs and they are involved in many human diseases, including various types of cancers. Recently, microRNA-383 (miR-383) has been identified as being aberrantly expressed in multiple cancers, such as malignant melanoma, colorectal cancer, hepatocellular cancer, and glioma. Increasing evidence suggests that miR-383 participates in tumorigenic events including proliferation, apoptosis, invasion, and metastasis as well as drug resistance. Although downstream targets including CCND1, LDHA, VEGF, and IGF are illustrated to be regulated by miR-383, its roles in carcinogenesis are still ambiguous and the underlying mechanisms are still unclear. Herein, we review the latest studies on miR-383 and summarize its functions in human cancers and other diseases. The goal of this review is to provide new strategies for targeted therapy and further investigations.

MicroRNA-214 in Health and Disease

MicroRNAs (miRNAs) are endogenously expressed, non-coding RNA molecules that mediate the post-transcriptional repression and degradation of mRNAs by targeting their 3′ untranslated region (3′-UTR). Thousands of miRNAs have been identified since their first discovery in 1993, and miR-214 was first reported to promote apoptosis in HeLa cells. Presently, miR-214 is implicated in an extensive range of conditions such as cardiovascular diseases, cancers, bone formation and cell differentiation. MiR-214 has shown pleiotropic roles in contributing to the progression of diseases such as gastric and lung cancers but may also confer cardioprotection against excessive fibrosis and oxidative damage. These contrasting functions are achieved through the diverse cast of miR-214 targets. Through silencing or overexpressing miR-214, the detrimental effects can be attenuated, and the beneficial effects promoted in order to improve health outcomes. Therefore, discovering novel miR-214 targets and understanding how miR-214 is dysregulated in human diseases may eventually lead to miRNA-based therapies. MiR-214 has also shown promise as a diagnostic biomarker in identifying breast cancer and coronary artery disease. This review provides an up-to-date discussion of miR-214 literature by describing relevant roles in health and disease, areas of disagreement, and the future direction of the field.

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.

TCF21 regulates miR-10a-5p/LIN28B signaling to block the proliferation and invasion of melanoma cells

Background and aim

Some research has suggested that miRNA-10a (miR-10a-5p) had an inhibitory function in proliferation and invasion of cancers. Whereas the role of miR-10a-5p in melanoma has not been fully explored. This study aims to confirm LIN28B as the targeted gene of miR-10a-5p which was explored in melanoma cells. In addition, upstream regulatory molecule of miR-10a-5p was also investigated in melanoma cells.

Methods

Real-time Quantitative polymerase chain reaction (RT-qPCR) was adopted to analyze miR-10a-5p expression level in melanoma and the normal human epidermal melanocyte cells. Several biological assays were performed to evaluate miR-10a-5p influences on cell proliferation, migration and invasion ability in A375 and B16-F10 cells. Gene prediction of miRNA targeting and a dual luciferase assay were applied to assess miR-10a-5p-targeted LIN28B. Western blot assessed the impacts of miR-10a-5p on the protein expression of LIN28B. Western blot analyzed the TCF21 effects on the expression of LIN28B and RT-qPCR assessed the influence of TCF21 on the expression level of miRNA-10a. In addition, Chromatin Immunoprecipitation (ChIP) Assay and JASPAR databases were employed to explore the regulatory relationship between TCF21 and miR-10a-5p.

Results

We discovered that miR-10a-5p expression was lower in melanoma cells and high expression of miR-10a-5p suppressed the proliferation, migration and invasion abilities of melanoma cells. We also discovered that miR-10a-5p targeted the LIN28B mRNA 3′UTR area and diminished LIN28B protein expression. We found that LIN28B expression was strongly decreased by TCF21 upregulation in the two melanoma cells. The qRT-PCR assay showed that miR-10a-5p expression level was obviously boosted by increased TCF21 expression. The results also demonstrated that TCF21 directly regulated miR-10a-5p at transcript levels.

Conclusion

TCF21 induced miRNA-10a targeting LIN28B could affect the progression and growth of melanoma.

Molecular Changes Induced in Melanoma by Cell Culturing in 3D Alginate Hydrogels

Simple Summary

The research field of 3D cell cultivation in hydrogels is continuously growing. To be able to analyze the reaction of melanoma cells to 3D cultivation in alginate hydrogel on a molecular level, whole transcriptome sequencing was performed. Intriguingly, we could not only unravel differences between the gene regulation in 2D and 3D cultures but could also correlate the culture switch to the physiological process of tumor plasticity based on the observed patterns. Thereby, the role of EGR1 in controlling tumor plasticity and progression in melanoma was revealed. We conclude that the combination of cell culture models using biomaterials and whole transcriptome analysis leads to a deeper molecular understanding of cancer cells, herewith defining new therapeutic targets.

Abstract

Alginate hydrogels have been used as a biomaterial for 3D culturing for several years. Here, gene expression patterns in melanoma cells cultivated in 3D alginate are compared to 2D cultures. It is well-known that 2D cell culture is not resembling the complex in vivo situation well. However, the use of very intricate 3D models does not allow performing high-throughput screening and analysis is highly complex. 3D cell culture strategies in hydrogels will better mimic the in vivo situation while they maintain feasibility for large-scale analysis. As alginate is an easy-to-use material and due to its favorable properties, it is commonly applied as a bioink component in the growing field of cell encapsulation and biofabrication. Yet, only a little information about the transcriptome in 3D cultures in hydrogels like alginate is available. In this study, changes in the transcriptome based on RNA-Seq data by cultivating melanoma cells in 3D alginate are analyzed and reveal marked changes compared to cells cultured on usual 2D tissue culture plastic. Deregulated genes represent valuable cues to signaling pathways and molecules affected by the culture method. Using this as a model system for tumor cell plasticity and heterogeneity, EGR1 is determined to play an important role in melanoma progression.

miR-138-5p induces aggressive traits by targeting Trp53 expression in murine melanoma cells, and correlates with poor prognosis of melanoma patients

Deregulation of miRNAs contributes to the development of distinct cancer types, including melanoma, an aggressive form of skin cancer characterized by high metastatic potential and poor prognosis. The expression of a set of 580 miRNAs was investigated in a model of murine melanoma progression, comprising non-metastatic (4C11-) and metastatic melanoma (4C11+) cells. A significant increase in miR-138-5p expression was found in the metastatic 4C11+ melanoma cells compared to 4C11-, which prompted us to investigate its role in melanoma aggressiveness. Functional assays, including anoikis resistance, colony formation, collective migration, serum-deprived growth capacity, as well as in vivo tumor growth and experimental metastasis were performed in 4C11- cells stably overexpressing miR-138-5p. miR-138-5p induced an aggressive phenotype in mouse melanoma cell lines leading to increased proliferation, migration and cell viability under stress conditions. Moreover, by overexpressing miR-138-5p, low-growing and non-metastatic 4C11- cells became highly proliferative and metastatic in vivo, similar to the metastatic 4C11+ cells. Luciferase reporter analysis identified the tumor suppressor Trp53 as a direct target of miR-138-5p. Using data sets from independent melanoma cohorts, miR-138-5p and P53 expression were also found deregulated in human melanoma samples, with their levels negatively and positively correlated with prognosis, respectively. Our data shows that the overexpression of miR-138-5p contributes to melanoma metastasis through the direct suppression of Trp53.

Learning from Embryogenesis-A Comparative Expression Analysis in Melanoblast Differentiation and Tumorigenesis Reveals miRNAs Driving Melanoma Development

Malignant melanoma is one of the most dangerous tumor types due to its high metastasis rates and a steadily increasing incidence. During tumorigenesis, the molecular processes of embryonic development, exemplified by epithelial-mesenchymal transition (EMT), are often reactivated. For melanoma development, the exact molecular differences between melanoblasts, melanocytes, and melanoma cells are not completely understood. In this study, we aimed to identify microRNAs (miRNAs) that promote melanoma tumorigenesis and progression, based on an in vitro model of normal human epidermal melanocyte (NHEM) de-differentiation into melanoblast-like cells (MBrCs). Using miRNA-sequencing and differential expression analysis, we demonstrated in this study that a majority of miRNAs have an almost equal expression level in NHEMs and MBrCs but are significantly differentially regulated in primary tumor- and metastasis-derived melanoma cell lines. Further, a target gene analysis of strongly regulated but functionally unknown miRNAs yielded the implication of those miRNAs in many important cellular pathways driving malignancy. We hypothesize that many of the miRNAs discovered in our study are key drivers of melanoma development as they account for the tumorigenic potential that differentiates melanoma cells from proliferating or migrating embryonic cells.

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.

miR-548b Suppresses Melanoma Cell Growth, Migration, and Invasion by Negatively Regulating Its Target Gene HMGB1

Background: Melanoma is one of the most aggressive malignancies. Exploration of metastasis-related genes will improve the clinical outcomes of patients with melanoma. Recently, microRNAs (miRNAs) have been implicated in regulating the aggressiveness of melanoma. In the current study, the author demonstrated the expression of miR-548b and its functions in melanoma. Materials and Methods: The expression levels of miR-548b and high mobility group protein 1 (HMGB1) in melanoma specimens and adjacent normal tissues were examined using the quantitative real-time PCR method. The Cell Counting Kit-8 (CCK-8), wound healing test, and Transwell assays were conducted to examine the impact of miR-548b on aggressive phenotypes of melanoma cells. The protein expression of HMGB1 was detected by Western blot. The tumor growth of melanoma cells in vivo was analyzed using the transplanted tumor model. The expression of HMGB1 in vivo was assessed using immunohistochemistry assay. Results: miR-548b was significantly downregulated in the melanoma sample when compared with adjacent normal tissues. In addition, low levels of miR-548b were related to poor overall survival in patients with melanoma. As predicted, overexpression of miR-548b suppressed the growth and metastasis-associated traits of melanoma cells. Furthermore, the luciferase reporter gene assay and Western blotting revealed that HMGB1 was a target of miR-548b and its expression level was negatively modulated by miR-548b. Several rescue experiments indicated that reintroduction of HMGB1 abolished the inhibiting effects of miR-548b on melanoma cells. Finally, the author demonstrated that upregulation of miR-548b repressed melanoma cell growth in vivo. Conclusions: All these findings demonstrate that miR-548b serves as a cancer-suppressive miRNA in human melanoma by inhibiting HMGB1.

Integrated Genomics Identifies miR-181/TFAM Pathway as a Critical Driver of Drug Resistance in Melanoma

MicroRNAs (miRNAs) are attractive therapeutic targets and promising candidates as molecular biomarkers for various therapy-resistant tumors. However, the association between miRNAs and drug resistance in melanoma remains to be elucidated. We used an integrative genomic analysis to comprehensively study the miRNA expression profiles of drug-resistant melanoma patients and cell lines. MicroRNA-181a and -181b (miR181a/b) were identified as the most significantly down-regulated miRNAs in resistant melanoma patients and cell lines. Re-establishment of miR-181a/b expression reverses the resistance of melanoma cells to the BRAF inhibitor dabrafenib. Introduction of miR-181 mimics markedly decreases the expression of TFAM in A375 melanoma cells resistant to BRAF inhibitors. Furthermore, melanoma growth was inhibited in A375 and M14 resistant melanoma cells transfected with miR-181a/b mimics, while miR-181a/b depletion enhanced resistance in sensitive cell lines. Collectively, our study demonstrated that miR-181a/b could reverse the resistance to BRAF inhibitors in dabrafenib resistant melanoma cell lines. In addition, miR-181a and -181b are strongly down-regulated in tumor samples from patients before and after the development of resistance to targeted therapies. Finally, melanoma tissues with high miR-181a and -181b expression presented favorable outcomes in terms of Progression Free Survival, suggesting that miR-181 is a clinically relevant candidate for therapeutic development or biomarker-based therapy selection.

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.

The Non-Coding Landscape of Cutaneous Malignant Melanoma: A Possible Route to Efficient Targeted Therapy

Considered to be highly lethal if not diagnosed in early stages, cutaneous malignant melanoma is among the most aggressive and treatment-resistant human cancers, and its incidence continues to rise, largely due to ultraviolet radiation exposure, which is the main carcinogenic factor. Over the years, researchers have started to unveil the molecular mechanisms by which malignant melanoma can be triggered and sustained, in order to establish specific, reliable biomarkers that could aid the prognosis and diagnosis of this fatal disease, and serve as targets for development of novel efficient therapies. The high mutational burden and heterogeneous nature of melanoma shifted the main focus from the genetic landscape to epigenetic and epitranscriptomic modifications, aiming at elucidating the role of non-coding RNA molecules in the fine tuning of melanoma progression. Here we review the contribution of microRNAs and lncRNAs to melanoma invasion, metastasis and acquired drug resistance, highlighting their potential for clinical applications as biomarkers and therapeutic targets.

Hydrogel-Based Technologies for the Diagnosis of Skin Pathology

Hydrogels, swellable hydrophilic polymer networks fabricated through chemical cross-linking or physical entanglement are increasingly utilized in various biomedical applications over the past few decades. Hydrogel-based microparticles, dressings and microneedle patches have been explored to achieve safe, sustained and on-demand therapeutic purposes toward numerous skin pathologies, through incorporation of stimuli-responsive moieties and therapeutic agents. More recently, these platforms are expanded to fulfill the diagnostic and monitoring role. Herein, the development of hydrogel technology to achieve diagnosis and monitoring of pathological skin conditions are highlighted, with proteins, nucleic acids, metabolites, and reactive species employed as target biomarkers, among others. The scope of this review includes the characteristics of hydrogel materials, its fabrication procedures, examples of diagnostic studies, as well as discussion pertaining clinical translation of hydrogel systems.

MicroRNAs as Key Players in Melanoma Cell Resistance to MAPK and Immune Checkpoint Inhibitors

Advances in the use of targeted and immune therapies have revolutionized the clinical management of melanoma patients, prolonging significantly their overall and progression-free survival. However, both targeted and immune therapies suffer limitations due to genetic mutations and epigenetic modifications, which determine a great heterogeneity and phenotypic plasticity of melanoma cells. Acquired resistance of melanoma patients to inhibitors of BRAF (BRAFi) and MEK (MEKi), which block the mitogen-activated protein kinase (MAPK) pathway, limits their prolonged use. On the other hand, immune checkpoint inhibitors improve the outcomes of patients in only a subset of them and the molecular mechanisms underlying lack of responses are under investigation. There is growing evidence that altered expression levels of microRNAs (miRNA)s induce drug-resistance in tumor cells and that restoring normal expression of dysregulated miRNAs may re-establish drug sensitivity. However, the relationship between specific miRNA signatures and acquired resistance of melanoma to MAPK and immune checkpoint inhibitors is still limited and not fully elucidated. In this review, we provide an updated overview of how miRNAs induce resistance or restore melanoma cell sensitivity to mitogen-activated protein kinase inhibitors (MAPKi) as well as on the relationship existing between miRNAs and immune evasion by melanoma cell resistant to MAPKi.

Apolipoprotein A-I anti-tumor activity targets cancer cell metabolism

Previously, we reported apolipoprotein A-I (apoA-I), the major protein component of high-density lipoprotein (HDL), has potent anti-melanoma activity. We used DNA microarray and bioinformatics to interrogate gene expression profiles of tumors from apoA-I expressing (A-I Tg+/-) versus apoA-I-null (A-I KO) animals to gain insights into mechanisms of apoA-I tumor protection. Differential expression analyses of 11 distinct tumors per group with > 1.2-fold cut-off and a false discovery rate adjusted p < 0.05, identified 176 significant transcripts (71 upregulated and 105 downregulated in A-I Tg+/- versus A-I KO group). Bioinformatic analyses identified the mevalonate and de novo serine/glycine synthesis pathways as potential targets for apoA-I anti-tumor activity. Relative to A-I KO, day 7 B16F10L melanoma tumor homografts from A-I Tg+/- exhibited reduced expression of mevalonate-5-pyrophosphate decarboxylase (Mvd), a key enzyme targeted in cancer therapy, along with a number of key genes in the sterol synthesis arm of the mevalonate pathway. Phosphoglycerate dehydrogenase (Phgdh), the first enzyme branching off glycolysis into the de novo serine synthesis pathway, was the most repressed transcript in tumors from A-I Tg+/-. We validated our mouse tumor studies by comparing the significant transcripts with adverse tumor markers previously identified in human melanoma and found 45% concordance. Our findings suggest apoA-I targets the mevalonate and serine synthesis pathways in melanoma cells in vivo, thus providing anti-tumor metabolic effects by inhibiting the flux of biomolecular building blocks for macromolecule synthesis that drive rapid tumor growth.

MicroRNA-379 mediates pigmentation, migration and proliferation of melanocytes by targeting the insulin-like growth factor 1 receptor

Melanogenesis, migration and proliferation of melanocytes are important factors that determine the hair colours of mammals. MicroRNAs (miRNAs) have been shown to be closely related to these processes. In melanocytes of alpacas, insulin-like growth factor 1 (IGF1) has been shown to improve melanogenesis through the cyclic AMP (cAMP) pathway. miR-379 was predicted to target insulin-like growth factor (IGF) receptor 1 (IGF1R), which binds to IGF1. Therefore, we hypothesized that miR-379 could mediate melanogenesis, migration and proliferation of melanocytes. Here, we report that miR-379 was highly expressed in alpaca melanocytes. Subsequent overexpression of miR-379 in alpaca melanocytes led to the generation of the phenotype of melanogenesis, proliferation and migration. In addition, the expression of genes related to these phenotypes in melanocytes was detected. Our results showed that miR-379 targets IGF1R in melanocytes. The overexpression of miR-379 stimulated dendrite extension or elongation and limited the perinuclear distribution of melanin, but inhibited melanogenesis via cAMP response element (CRE)-binding protein (CREB)/microphthalmia-associated transcription factor (MITF) pathway. miR-379 attenuated melanocyte migration by downregulating the focal adhesion kinase (FAK) and enhanced melanocyte proliferation by upregulating protein kinase B (AKT). These observations suggest the involvement of miR-379 in the physiological regulation of melanocytes, mediated by targeting IGF1R on insulin receptor (IR) compensation and subsequent crosstalk.

Defining the Prognostic Role of MicroRNAs in Cutaneous Melanoma

Breslow thickness (BT) is the most important histopathologic factor for primary melanoma staging. BT determines the margins for wide local excision whether sentinel lymph node biopsy should be performed and subsequent melanoma staging, and patient management. The correct determination of a 0.8-mm cutoff in melanoma is important for pathologists because discrepancies leading to a change in stage can have significant clinical implications, including incorrect and/or inappropriate prognostic information, investigation, management, and follow-up. Difficulties in BT determination are mostly represented by the presence of regression or melanoma associated with a pre-existing nevus. This study aimed at investigating a molecular parameter, namely microRNA (miRNA) expression, in reference to BT assessment. Melanoma cell proliferation is influenced by miRNA dysregulation. Indeed, some miRNAs sustain and induce proliferative signals or repress growth-suppressive pathways, thereby promoting melanoma carcinogenesis. To identify the miRNAs correlating with BT, we analyzed our global miRNA expression data of 20 thin melanomas and identified two potential candidates, miR-21-5p and miR-146a-5p. We assessed the expression of these two specific miRNAs in 90 archive formalin-fixed and paraffin-embedded samples of superficially spreading melanomas (SSMs) and 25 nodular melanomas from two independent cohorts and correlated the individual and combined miRNA expression with BT and other tumor characteristics. The individually normalized expression of miR-21-5p and miR-146a-5p showed a highly significant and linear correlation with BT in SSM, and their combined expression value was more strongly correlated (Pearson's r = 0.799, 95% CI = 0.71-0.86) than their individual expressions. This correlation was not significant in nodular melanoma. In SSM, we observed that the combined miRNA expression above or below 1.5 was significantly associated with overall survival and successfully identified all patients with relapsing SSM. We concluded that the combined assessment of miR-21-5p and miR-146a-5p expression in superficially spreading melanoma, in association with BT measurement, could aid pathologists in SSM staging.

Axl-148b chimeric aptamers inhibit breast cancer and melanoma progression

microRNAs (miRNAs) are small non-coding RNAs acting as negative regulators of gene expression and involved in tumor progression. We recently showed that inhibition of the pro-metastatic miR-214 and simultaneous overexpression of its downstream player, the anti-metastatic miR-148b, strongly reduced metastasis formation. To explore the therapeutic potential of miR-148b, we generated a conjugated molecule aimed to target miR-148b expression selectively to tumor cells. Precisely, we linked miR-148b to GL21.T, an aptamer able to specifically bind to AXL, an oncogenic tyrosine kinase receptor highly expressed on cancer cells. Axl-148b conjugate was able to inhibit migration and invasion of AXL-positive, but not AXL-negative, cancer cells, demonstrating high efficacy and selectivity in vitro. In parallel, expression of ALCAM and ITGA5, two miR-148b direct targets, was reduced. More importantly, axl-148b chimeric aptamers were able to inhibit formation and growth of 3D-mammospheres, to induce necrosis and apoptosis of treated xenotransplants, as well as to block breast cancer and melanoma dissemination and metastatization in mice. Relevantly, axl aptamer acted as specific delivery tool for miR-148b, but it also actively contributed to inhibit metastasis formation, together with miR-148b. In conclusion, our data show that axl-148b conjugate is able to inhibit tumor progression in an axl- and miR-148b-dependent manner, suggesting its potential development as therapeutic molecule.

Dissimilar Appearances Are Deceptive-Common microRNAs and Therapeutic Strategies in Liver Cancer and Melanoma

: In this review, we summarize the current knowledge on miRNAs as therapeutic targets in two cancer types that were frequently described to be driven by miRNAs-melanoma and hepatocellular carcinoma (HCC). By focusing on common microRNAs and associated pathways in these-at first sight-dissimilar cancer types, we aim at revealing similar molecular mechanisms that are evolved in microRNA-biology to drive cancer progression. Thereby, we also want to outlay potential novel therapeutic strategies. After providing a brief introduction to general miRNA biology and basic information about HCC and melanoma, this review depicts prominent examples of potent oncomiRs and tumor-suppressor miRNAs, which have been proven to drive diverse cancer types including melanoma and HCC. To develop and apply miRNA-based therapeutics for cancer treatment in the future, it is essential to understand how miRNA dysregulation evolves during malignant transformation. Therefore, we highlight important aspects such as genetic alterations, miRNA editing and transcriptional regulation based on concrete examples. Furthermore, we expand our illustration by focusing on miRNA-associated proteins as well as other regulators of miRNAs which could also provide therapeutic targets. Finally, design and delivery strategies of miRNA-associated therapeutic agents as well as potential drawbacks are discussed to address the question of how miRNAs might contribute to cancer therapy in the future.

Circulating microRNAs as biomarkers for early diagnosis of cutaneous melanoma

Introduction: Cutaneous melanoma is the deadliest form of skin cancer, with a dramatic increase in the incidence rate worldwide over the past decade. Early detection has been shown to improve the outcome of melanoma patients. The identification of noninvasive biomarkers able to identify melanoma at an early stage remains an unmet clinical need. Circulating miRNAs (c-miRNAs), small non-coding RNAs, appear as potential ideal candidate biomarkers due to their stability in biological fluids and easy detectability. Moreover, c-miRNAs are reported to be heavily deregulated in cancer patients.Areas covered: This review examines evidence of the specific c-miRNAs or panels of c-miRNAs reported to be useful in discriminating melanoma from benign cutaneous lesions.Expert opinion: Although the interesting reported by published studies, the non-homogeneity of detection and normalization methods prevents the individuation of single c-miRNA or panel of c-miRNAs that are specific for early detection of cutaneous melanoma. In the future, prospective wide and well-designed clinical trials will be needed to validate the diagnostic potential of some of the c-miRNA candidates in clinical practice.

Novel MicroRNA Biomarkers, miR-142-5p, miR-550a, miR-1826, and miR-1201, Were Identified for Primary Melanoma

This study was aimed to identify novel miRNA biomarkers and explore the cooperative function of multi-RNAs in the progress of primary melanoma. The miRNA expression profile GSE62370 generated from 9 congenital nevi and 92 primary melanoma samples was downloaded from the Gene Expression Omnibus database. Differentially expressed miRNAs between primary melanoma and congenital nevi were compared and the target genes of them were selected. Pathway enrichment analysis and protein/protein interaction (PPI) network of miRNA target genes were performed. In addition, the differential expression of miRNAs to identify the tumor stage-dependent differences in miRNA expression was analyzed. Differentially expressed miRNAs, including 6 upregulated and 23 downregulated, were found in primary melanoma. Besides, the miRNA-associated gene regulatory network revealed 274 nodes, including miR-142-5p and miR-125b, and 307 miRNA-target pairs. miRNA-related Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway, such as melanoma, was found. Target genes in the PPI module were mainly enriched in cancer-related pathways. Finally, the melanoma stage-related overexpressed miR-142-5p and the downregulated miR-550, miR-1826, miR-1201, miR-205, and miR-125b were identified. Some validated miRNAs, including miR-125a/b, let-7a/b, and miR-205, were found and illustrated the reliability of our study. Four novel miRNAs, including miR-142-5p, miR-550a, miR-1826, and miR-1201, were considered to have potential prognostic values for primary melanoma.

Comparison of miRNA-101a-3p and miRNA-144a-3p regulation with the key genes of alpaca melanocyte pigmentation

Background

Many miRNA functions have been revealed to date. Single miRNAs can participate in life processes by regulating more than one target gene, and more than one miRNA can also simultaneously act on one target mRNA. Thus, a complex regulatory network involved in many processes can be formed. Herein, the pigmentation regulation mechanism of miR-101a-3p and miR-144a-3p was studied at the cellular level by the overexpression and equal overexpression of miR-101a-3p and miR-144a-3p.

Results

Results revealed that miR-101a-3p and miR-144a-3p directly regulated the expression of microphthalmia-associated transcription factor, thereby affecting melanin synthesis.

Conclusions

The two miRNAs with the same binding site in the same gene independently excreted each other’s function. However, the inhibitory effect of miR-144a-3p was stronger than that of miR-101-3p in alpaca melanocytes, although both decreased melanin production.

A plasma microRNA biomarker of melanoma as a personalised assessment of treatment response

New tools for monitoring response to primary melanoma treatment are needed to reduce recurrence rates and patient anxiety. A previously developed plasma-based microRNA signature (MEL38) was measured in four melanoma patient samples obtained before and 12-14 days after treatment (i.e. surgical excision), as well as in two nonmelanoma controls. The value of the MEL38 score and selected individual genes were compared between the time points. The MEL38 scores of the four patients with melanoma became more 'normal like' after tumour excision, with a statistically significant 15% mean reduction. MicroRNAs involved in tumour suppression were upregulated in the postexcision samples and those involved in facilitating treatment resistance and tumour invasion were downregulated. Based on these limited preliminary data, the MEL38 signature may have clinical utility in assessing an individual patient's response to the most common form of melanoma treatment. Additional studies are needed on larger, clinically diverse patient cohorts, sampled over longer periods of time.

MicroRNA-330 inhibits growth and migration of melanoma A375 cells: In vitro study

Melanoma skin cancer is one of the main causes of male cancer-related deaths worldwide. It has been suggested that miR-330-5p can act as a tumor suppressor in various types of cancers. So, in this study, we replaced miR-330 in melanoma cancer cells by vector-based miR-330 to evaluate the effects of this microRNA on the growth and migration inhibition of melanoma cancer cells, and to determine the molecular mechanisms underlying its action. By using the MTT assay, the IC₅₀ of Geneticin antibiotic was obtained as 460 µg/mL. The results of the qRT-PCR showed the increased expression level of miR-330 and decreased expression levels of MMP-9, CXCR4, Vimentin, melanoma cell adhesion molecule, AKT1, and E2F1 messenger RNA in A375 transfected cells. The cytotoxicity assay results demonstrated the inhibition of cancer cells proliferation. Furthermore, the wound healing test results showed a migration reduction of transfected cells with miR-330 compared with nontransfected ones. In addition, 4',6-diamidino-2-phenylindoleLB: Luria-Bertani (DAPI) staining revealed the significant nucleus fragmentation in miR-330 replaced cells, which correspond to apoptosis induction in replaced cells. The results showed that increase in miR-330 expression level could significantly inhibit the tumor cell growth and the migration of melanoma cancer cells.

Role of miRNAs in Melanoma Metastasis

Tumour metastasis is a multistep process. Melanoma is a highly aggressive cancer and metastasis accounts for the majority of patient deaths. microRNAs (miRNAs) are non-coding RNAs that affect the expression of their target genes. When aberrantly expressed they contribute to the development of melanoma. While miRNAs can act locally in the cell where they are synthesized, they can also influence the phenotype of neighboring melanoma cells or execute their function in the direct tumour microenvironment by modulating ECM (extracellular matrix) and the activity of fibroblasts, endothelial cells, and immune cells. miRNAs are involved in all stages of melanoma metastasis, including intravasation into the lumina of vessels, survival during circulation in cardiovascular or lymphatic systems, extravasation, and formation of the pre-metastatic niche in distant organs. miRNAs contribute to metabolic alterations that provide a selective advantage during melanoma progression. They play an important role in the development of drug resistance, including resistance to targeted therapies and immunotherapies. Distinct profiles of miRNA expression are detected at each step of melanoma development. Since miRNAs can be detected in liquid biopsies, they are considered biomarkers of early disease stages or response to treatment. This review summarizes recent findings regarding the role of miRNAs in melanoma metastasis.

Systematic Review and Meta-analysis of the Prognostic Significance of miRNAs in Melanoma Patients

BACKGROUND

Melanoma is the most aggressive and deadly form of skin cancer. The molecular variability involving microRNA (miRNA) expression plays a significant role in melanogenesis, which leads to poor prognostic effects in melanoma. Since there is a scarcity of comprehensive data on the prognostic role of miRNAs in melanoma patients, this study focuses on filling this knowledge gap through a systematic review and meta-analysis.

METHODS

The included studies were extracted from several bibliographic databases between 2012 and 2018 using multiple keywords according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. The hazard ratios (HRs) and 95% confidence intervals (CIs) for different survival endpoints were compared to the high and low expression levels of miRNAs. The mean effect size of HR values was estimated using a random-effects model of meta-analysis. Inverted funnel plot symmetry was used to assess publication bias. Subgroup analysis was carried out individually for multiple miRNAs across different studies.

RESULTS

A total of 24 studies across eight countries were included, of which 16 studies were eligible for meta-analysis. Twenty-five miRNA expression levels were studied from 2669 melanoma patients to estimate the association between the prognostic role of miRNAs and survival outcome in these 16 studies. The overall pooled effect size (HR) for up- and downregulated miRNAs was 1.043 (95% CI 0.921-1.181; p = 0.506), indicating that the miRNA expression increased the likelihood of death in melanoma patients by 4.3%. Subgroup analysis for miRNA10b, miRNA16 and miRNA21 showed a poor prognosis. The quality assessment revealed that 16 studies were good quality and eight studies were of fair quality.

CONCLUSION

This is one of the first pooled meta-analysis studies on the role of miRNAs in the prognosis of melanoma. Our findings are inconclusive but suggest that miRNA expression could predict poor survival in melanoma patients. Therefore, miRNA expression could act as promising prognostic marker for melanoma.

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 potential of BRAF-associated non-coding RNA as a therapeutic target in melanoma

INTRODUCTION

The advent of targeted therapies and immune checkpoints inhibitors has enhanced the treatment of metastatic melanomas. Despite striking improvements of patients' survival, drug resistance continues to limit the efficacy of such treatments. Genetic and nongenetic/adaptive mechanisms of resistance could be involved; in the latter mechanism, noncoding RNAs (ncRNAs) are emerging as key players. Areas covered: This article outlines the current knowledge of ncRNA involvement in BRAF-mutant melanomas and the development of resistance to targeted/immunotherapies. We also discuss how ncRNAs can be exploited for the development of therapeutic and diagnostic approaches. Expert opinion: ncRNAs can be envisaged as powerful diagnostics and therapeutics. Despite progress in our knowledge about their deregulation in cancer, it is still difficult to derive universal and robust ncRNAs unique signatures of malignancy for diagnostic purposes, which need validation in large cohort of patients. Also, ncRNA specific targeting to melanoma cells in vivo requires the development of improved systemic delivery tools. In this regard, the development of stable nanodelivery particles seems to offer renewed hope for success in the clinic.

miR-30a Inhibits Melanoma Tumor Metastasis by Targeting the E-cadherin and Zinc Finger E-box Binding Homeobox 2

Background:

Epithelial–mesenchymal transition (EMT) is actively involved in tumor invasion. The main hallmark of EMT is downregulation of the adherens junction protein E-cadherin due to transcriptional repression. Candidate E-cadherin transcription repressors are members of ZEB family, ZEB2 belong to the ZEB family transcription factor that is pivotal for embryonic development and tumor progression. ZEB2 (zinc finger E-box binding homeobox 2) is most widely known as an inducer of EMT. Growing evidence have shown the involvement of microRNAs in cancer progression. In this study, we demonstrate that miR-30a is a potent suppressor of melanoma metastasis to the lung.

Materials and Methods:

In this study, miR-30a has been transfected into B16-F10 melanoma cells, and then cells were injected intravenously into C57BL/6 mice. Then, the mice were sacrificed and nodules in the lungs were enumerated.

Results:

Ectopic expression of miR-30a in melanoma cell line resulted in the suppression of pulmonary metastasis. We also found that transfected miR-30a into melanoma cells could increase E-cadherin and decrease ZEB2 expression.

Conclusions:

Our findings showed that increased expression of miR-30a in melanoma inhibited metastasis in vivo by targeting ZEB2 and E-cadherin.

Identification of dysregulated microRNAs in canine malignant melanoma

Inhibiting aberrantly upregulated microRNAs (miR/miRNAs) has emerged as a novel focus for therapeutic intervention in human melanoma. Thus, identifying upregulated miRNAs is essential for identifying additional melanoma-associated therapeutic targets. In the present study, microarray-based miRNA profiling of canine malignant melanoma (CMM) tissue obtained from the oral cavity was performed and differential expression was confirmed by a reverse transcription-quantitative polymerase chain reaction (RT-qPCR). An analysis of the microarray data revealed 17 dysregulated miRNAs; 5 were upregulated and 12 were downregulated. RT-qPCR analysis was performed for 2 upregulated (miR-204 and miR-383), 3 downregulated (miR-122, miR-143 and miR-205) and 6 additional oncogenic miRNAs (oncomiRs; miR-16, miR-21, miR-29b, miR-92a, miR-125b and miR-222). The expression levels of seven of the miRNAs, miR-16, miR-21, miR-29b, miR-122, miR-125b, miR-204 and miR-383 were significantly upregulated; however, the expression of miR-205 was downregulated in CMM tissues compared with normal oral tissues. The microarray and RT-qPCR analyses validated the upregulation of two potential oncomiRs miR-204 and miR-383. The present study additionally constructed a protein interaction network and a miRNA-target regulatory interaction network using STRING and Cytoscape. In the proposed network, cyclin dependent kinase 2 was a target for miR-383, sirtuin 1 and tumor protein p53 were targets for miR-204 and ATR serine/threonine kinase was a target for both. It was concluded that miR-383 and miR-204 were potential oncomiRs that may be involved in regulating melanoma development by evading DNA repair and apoptosis.

MicroRNA-sequencing data analyzing melanoma development and progression

MicroRNAs (miRNAs) deregulated in melanoma are of growing importance in cancer research. We aimed to define the miRNAome of melanoma cell lines and primary melanocytes by RNA-Seq using identical cell lines as in a published miRNA expression study based on cDNA arrays. We identified 79 miRNAs, which are significantly deregulated during melanoma development. In addition, we could also determine 29 miRNAs being involved in melanoma progression. Interestingly, not all characterized miRNAs derived from cDNA array analyses of our and other groups could be found to be differentially expressed using RNA-Seq analyses, however, new miRNAs, formerly not associated with melanoma, were found to be strongly regulated.