miRNAs, Melanoma and Microenvironment: An Intricate Network

Pathology and Molecular Biology of Melanoma

Almost every death in young patients with an advanced skin tumor is caused by melanoma. Today, with the help of modern treatments, these patients survive longer or can even achieve a cure. Advanced stage melanoma is frequently related with poor prognosis and physicians still find this disease difficult to manage due to the absence of a lasting response to initial treatment regimens and the lack of randomized clinical trials in post immunotherapy/targeted molecular therapy settings. New therapeutic targets are emerging from preclinical data on the genetic profile of melanocytes and from the identification of molecular factors involved in the pathogenesis of malignant transformation. In the current paper, we present the diagnostic challenges, molecular biology and genetics of malignant melanoma, as well as the current therapeutic options for patients with this diagnosis.

Ubiquitination-related biomarkers in metastatic melanoma patients and their roles in tumor microenvironment

Background

Skin cutaneous melanoma (SKCM) is the deadliest type of cutaneous malignancy. Ubiquitination is a process of protein sorting and degradation that exhibits multiple functions in the progression of various tumors. This study aimed to characterize a set of genes for ubiquitination in SKCM.

Methods

The expression patterns of ubiquitin-associated genes (URGs) and the corresponding clinical information in SKCM tissues were comprehensively analyzed based on The Cancer Genome Atlas (TCGA) database. We performed univariate and multivariate Cox proportional regression models to characterize the risk scores and identify four critical genes related to prognostic ubiquitination (HCLS1, CORO1A, NCF1 and CCRL2), which were used to construct the prognostic signatures. We also studied the effects of HCLS1, CORO1A and CCRL2 on tumor metastasis-related indicators at the cellular level through in vitro experiments.

Results

SKCM patients in the low-risk group showing a longer survival than those in the high-risk group. Characteristic risk scores correlated with several clinicopathological variables and reflected the infiltration of multiple immune cells. In addition, the knockdown of CLS1, CORO1A and CCRL2 affected cellular malignant biological behavior through the EMT signaling pathway.

Conclusion

This study provides a novel and prospective strategy to improve the clinical survival of SKCM patients.

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.

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.

A combined aging and immune prognostic signature predict prognosis and responsiveness to immunotherapy in melanoma

Background: Melanoma is the most lethal, and one of the most aggressive forms of cutaneous malignancies, which poor response to treatment has always puzzled clinicians. As is known to all, aging and immune microenvironment are two crucial factors impacting melanoma biological progress through the tumor microenvironment (TME). However, reliable biomarkers for predicting melanoma prognosis based on aging and immune microenvironment and therapeutic efficacy of immune checkpoints remain to be determined.

Methods: The aging-related genes (ARGs) were obtained from the Human Ageing Genomic Resources and immune-related genes (IRGs) were downloaded from the Immunology database as well as Analysis Portal (ImmPort) database. Next, we initially performed LASSO regression and multivariate Cox regression to identify prognostic ARGs and IRGs in the TCGA and GSE65904 datasets, and firstly constructed a novel comprehensive index of aging and immune (CIAI) signature. Finally, in vitro molecular biology experiments were performed to assess the regulatory role of CNTFR in melanoma cell lines proliferation and migration, macrophage recruitment, and M2 polarization.

Results: This novel CIAI signature consisted of 7 genes, including FOXM1, TP63, ARNTL, KIR2DL4, CCL8, SEMA6A, and CNTFR, in which melanoma patients in the high-CIAI group had shorter OS, DSS, and PFI, indicating CIAI model served as an independent prognostic index. Moreover, we found the CIAI score was potentially correlated with immune scores, estimate score, immune cell infiltration level, tumor microenvironment, immunotherapy effect, and drug sensitivity. Finally, CNTFR might function as oncogenes in melanoma cell lines and the silencing of CNTFR reduced macrophage recruitment and M2 polarization.

Conclusion: In this study, we have first presented a novel prognostic CIAI model applied to assess immune checkpoint therapy and the efficacy of conventional chemotherapy agents in melanoma patients. Thus providing a new insight for combating melanoma.

Circulating miR-1246 and miR-485-3p as Promising Biomarkers of Clinical Response and Outcome in Melanoma Patients Treated with Targeted Therapy

Despite the significant improvements in advanced melanoma therapy, there is still a pressing need for biomarkers that can predict patient response and prognosis, and therefore support rational treatment decisions. Here, we investigated whether circulating miRNAs could be biomarkers of clinical outcomes in patients treated with targeted therapy. Using next-generation sequencing, we profiled plasma miRNAs at baseline and at progression in patients treated with BRAF inhibitors (BRAFi) or BRAFi + MEKi. Selected miRNAs associated with response to therapy were subjected to validation by real-time quantitative RT-PCR . Receiver Operating Characteristics (ROC), Kaplan–Meier and univariate and multivariate Cox regression analyses were performed on the validated miR-1246 and miR-485-3p baseline levels. The median baseline levels of miR-1246 and miR-485-3p were significantly higher and lower, respectively, in the group of patients not responding to therapy (NRs) as compared with the group of responding patients (Rs). In Rs, a trend toward an increase in miR-1246 and a decrease in miR-485-3p was observed at progression. Baseline miR-1246 level and the miR-1246/miR-485-3p ratio showed a good ability to discriminate between Rs and NRs. Poorer PFS and OS were observed in patients with unfavorable levels of at least one miRNA. In multivariate analysis, a low level of miR-485-3p and a high miR-1246/miR-485-3p ratio remained independent negative prognostic factors for PFS, while a high miR-1246/miR-485-3p ratio was associated with an increased risk of mortality, although statistical significance was not reached. Evaluation of miR-1246 and miR-485-3p baseline plasma levels might help clinicians to identify melanoma patients most likely to be unresponsive to targeted therapy or at higher risk for short-term PFS and mortality, thus improving their management.

miRNAs and the Hippo pathway in cancer: Exploring the therapeutic potential (Review)

Cancer is recognized as the leading cause of death worldwide. The hippo signaling pathway regulates organ size by balancing cell proliferation and cell death; hence dysregulation of the hippo pathway promotes cancer‑like conditions. miRNAs are a type of non‑coding RNA that have been shown to regulate gene expression. miRNA levels are altered in various classes of cancer. Researchers have also uncovered a crosslinking between miRNAs and the hippo pathway, which has been linked to cancer. The components of the hippo pathway regulate miRNA synthesis, and various miRNAs regulate the components of the hippo pathway both positively and negatively, which can lead to cancer‑like conditions. In the present review article, the mechanism behind the hippo signaling pathway and miRNAs biogenesis and crosslinks between miRNAs and the hippo pathway, which result in cancer, shall be discussed. Furthermore, the article will cover miRNA‑related therapeutics and provide an overview of the development of resistance to anticancer drugs. Understanding the underlying processes would improve the chances of developing effective cancer treatment therapies.

Inhibiting Histone and DNA Methylation Improves Cancer Vaccination in an Experimental Model of Melanoma

Immunotherapy has improved the treatment of malignant skin cancer of the melanoma type, yet overall clinical response rates remain low. Combination therapies could be key to meet this cogent medical need. Because epigenetic hallmarks represent promising combination therapy targets, we studied the immunogenic potential of a dual inhibitor of histone methyltransferase G9a and DNA methyltransferases (DNMTs) in the preclinical B16-OVA melanoma model. Making use of tumor transcriptomic and functional analyses, methylation-targeted epigenetic reprogramming was shown to induce tumor cell cycle arrest and apoptosis in vitro coinciding with transient tumor growth delay and an IFN-I response in immune-competent mice. In consideration of a potential impact on immune cells, the drug was shown not to interfere with dendritic cell maturation or T-cell activation in vitro. Notably, the drug promoted dendritic cell and, to a lesser extent, T-cell infiltration in vivo, yet failed to sensitize tumor cells to programmed cell death-1 inhibition. Instead, it increased therapeutic efficacy of TCR-redirected T cell and dendritic cell vaccination, jointly increasing overall survival of B16-OVA tumor-bearing mice. The reported data confirm the prospect of methylation-targeted epigenetic reprogramming in melanoma and sustain dual G9a and DNMT inhibition as a strategy to tip the cancer-immune set-point towards responsiveness to active and adoptive vaccination against melanoma.

Characterization of Aging-Related Genes to Predict Prognosis and Evaluate the Tumor Immune Microenvironment in Malignant Melanoma

Objective. Malignant melanoma (MM) is one of the most malignant types of skin cancer and its incidence and mortality rates are increasing worldwide. Aging is well recognized as a significant risk factor for cancer. However, few studies have analyzed in depth the association between aging-related genes (AGs) and malignant melanoma prognosis with tumor immune microenvironment. Methods. Here, we downloaded 471 MM patients from The Cancer Genome Atlas (TCGA) with RNA sequence and clinicopathological data. 58 AGs from the TCGA dataset were examined using Cox regression and the LASSO assay. As a result, a gene signature for aging-related genes was created. The time-dependent ROC curve and Kaplan–Meier analysis were calculated to determine its predictive capability. Moreover, we created a nomogram for the clinicopathologic variables and the AGs gene signature to determine overall survival (OS). We also explored the association between three immune checkpoints, immune cell infiltration, and the aging-related gene signature. Results. We established an aging risk model to identify and predict the immune microenvironment in malignant melanoma. Then we developed and validated a prognosis risk model using three AGs (CSNK1E, C1QA, and SOD-2) in the GSE65904 dataset. The aging signature was positively associated with clinical and molecular characteristics and can be used as a prognostic factor for malignant melanoma. The low aging risk score was associated with a poor prognosis and indicated an immunosuppressive microenvironment. Conclusions. To summarize, we established and validated a model of aging risk based on three aging-related genes that acted as an independent prognostic predictor of overall survival. Besides, it also characterized the immune response in the malignant melanoma microenvironment and could provide a potential indicator of individualized immunotherapy in malignant melanoma.

Analyzing Prognostic Hub Genes in the Microenvironment of Cutaneous Melanoma by Computer Integrated Bioinformatics

Cutaneous melanoma (CM) is attracting increasing attention due to high mortality. In response to this, we synthetically analyze the CM dataset from the TCGA database and explore microenvironment-related genes that effectively predict patient prognosis. Immune/stromal scores of cases are calculated using the ESTIMATE algorithm and are significantly associated with overall patient survival. Then, differentially expressed genes are identified by comparing the immune score and stromal score, also prognostic genes are subsequently screened. Functional analysis shows that these genes are enriched in different activities of immune system. Moreover, 19 prognosis-related hub genes are extracted from the protein-protein interaction network, of which four unreported genes (IL7R, FLT3, C1QC, and HLA-DRB5) are chosen for validation. A significant negative relationship is found between the expression levels of the 4 genes and pathological stages, notably T grade. Furthermore, the K-M plots and TIMER results show that these genes have favorable value for CM prognosis. In conclusion, these results give a novel insight into CM and identify IL7R, FLT3, C1QC, and HLA-DRB5 as crucial roles for the diagnosis and treatment of CM.

Identification of a novel tumour microenvironment-based prognostic biomarker in skin cutaneous melanoma

Skin cutaneous melanoma (SKCM) is one of the most destructive skin malignancies and has attracted worldwide attention. However, there is a lack of prognostic biomarkers, especially tumour microenvironment (TME)-based prognostic biomarkers. Therefore, there is an urgent need to investigate the TME in SKCM, as well as to identify efficient biomarkers for the diagnosis and treatment of SKCM patients. A comprehensive analysis was performed using SKCM samples from The Cancer Genome Atlas and normal samples from Genotype-Tissue Expression. TME scores were calculated using the ESTIMATE algorithm, and differential TME scores and differentially expressed prognostic genes were successively identified. We further identified more reliable prognostic genes via least absolute shrinkage and selection operator regression analysis and constructed a prognostic prediction model to predict overall survival. Receiver operating characteristic analysis was used to evaluate the diagnostic efficacy, and Cox regression analysis was applied to explore the relationship with clinicopathological characteristics. Finally, we identified a novel prognostic biomarker and conducted a functional enrichment analysis. After considering ESTIMATEScore and tumour purity as differential TME scores, we identified 34 differentially expressed prognostic genes. Using least absolute shrinkage and selection operator regression, we identified seven potential prognostic biomarkers (SLC13A5, RBM24, IGHV3OR16-15, PRSS35, SLC7A10, IGHV1-69D and IGHV2-26). Combined with receiver operating characteristic and regression analyses, we determined PRSS35 as a novel TME-based prognostic biomarker in SKCM, and functional analysis enriched immune-related cells, functions and signalling pathways. Our study indicated that PRSS35 could act as a potential prognostic biomarker in SKCM by investigating the TME, so as to provide new ideas and insights for the clinical diagnosis and treatment of SKCM.

Heterogeneity of Melanoma Cell Responses to Sleep Apnea-Derived Plasma Exosomes and to Intermittent Hypoxia

Obstructive sleep apnea (OSA) is associated with increased cutaneous melanoma incidence and adverse outcomes. Exosomes are secreted by most cells, and play a role in OSA-associated tumor progression and metastasis. We aimed to study the effects of plasma exosomes from OSA patients before and after adherent treatment with continuous positive airway pressure (CPAP) on melanoma cells lines, and also to identify exosomal miRNAs from melanoma cells exposed to intermittent hypoxia (IH) or normoxia. Plasma-derived exosomes were isolated from moderate-to-severe OSA patients before (V1) and after (V2) adherent CPAP treatment for one year. Exosomes were co-incubated with three3 different melanoma cell lines (CRL 1424; CRL 1619; CRL 1675) that are characterized by genotypes involving different mutations in BRAF, STK11, CDKN2A, and PTEN genes to assess the effect of exosomes on cell proliferation and migration, as well as on pAMK activity in the presence or absence of a chemical activator. Subsequently, CRL-1424 and CRL-1675 cells were exposed to intermittent hypoxia (IH) and normoxia, and exosomal miRNAs were identified followed by GO and KEG pathways and gene networks. The exosomes from these IH-exposed melanoma cells were also administered to THP1 macrophages to examine changes in M1 and M2 polarity markers. Plasma exosomes from V1 increased CRL-1424 melanoma cell proliferation and migration compared to V2, but not the other two cell lines. Exposure to CRL-1424 exosomes reduced pAMPK/tAMPK in V1 compared to V2, and treatment with AMPK activator reversed the effects. Unique exosomal miRNAs profiles were identified for CRL-1424 and CRL-1675 in IH compared to normoxia, with six miRNAs being regulated and several KEGG pathways were identified. Two M1 markers (CXCL10 and IL6) were significantly increased in monocytes when treated with exosomes from IH-exposed CRL-1424 and CRL-1625 cells. Our findings suggest that exosomes from untreated OSA patients increase CRL-1424 melanoma malignant properties, an effect that is not observed in two other melanoma cell lines. Exosomal cargo from CRL-1424 cells showed a unique miRNA signature compared to CRL-1675 cells after IH exposures, suggesting that melanoma cells are differentially susceptible to IH, even if they retain similar effects on immune cell polarity. It is postulated that mutations in STK-11 gene encoding for the serine/threonine kinase family that acts as a tumor suppressor may underlie susceptibility to IH-induced metabolic dysfunction, as illustrated by CRL-1424 cells.

Malignant melanoma: Underlying epigenetic mechanisms

Although malignant melanoma is not the most common type of skin cancer, it is the most aggressive and fatal type as it can spread out and metastasize progressively. Early diagnosis and interventions lead to improved patient survival. The incidence rate of melanoma is dramatically increasing, with a few newer therapeutic options available. Therefore, establishing a reliable genetic or epigenetic-based diagnostic and prognostic tool is really important. In this review, we highlight the underlying epigenetic mechanisms involved in melanoma. Furthermore, the epigenetic-based therapeutic options will be also discussed. One of the key areas of discussion will be microRNA which is a small, single-stranded RNA molecule that serves as a regulatory element and found to regulate nearly a third of human genes. MicroRNAs play a role in a wide range of diseases including cancer. In malignant cells, it regulates cell proliferation, invasion, and metastasis.

Cutaneous Melanoma Classification: The Importance of High-Throughput Genomic Technologies

Cutaneous melanoma is an aggressive tumor responsible for 90% of mortality related to skin cancer. In the recent years, the discovery of driving mutations in melanoma has led to better treatment approaches. The last decade has seen a genomic revolution in the field of cancer. Such genomic revolution has led to the production of an unprecedented mole of data. High-throughput genomic technologies have facilitated the genomic, transcriptomic and epigenomic profiling of several cancers, including melanoma. Nevertheless, there are a number of newer genomic technologies that have not yet been employed in large studies. In this article we describe the current classification of cutaneous melanoma, we review the current knowledge of the main genetic alterations of cutaneous melanoma and their related impact on targeted therapies, and we describe the most recent high-throughput genomic technologies, highlighting their advantages and disadvantages. We hope that the current review will also help scientists to identify the most suitable technology to address melanoma-related relevant questions. The translation of this knowledge and all actual advancements into the clinical practice will be helpful in better defining the different molecular subsets of melanoma patients and provide new tools to address relevant questions on disease management. Genomic technologies might indeed allow to better predict the biological - and, subsequently, clinical - behavior for each subset of melanoma patients as well as to even identify all molecular changes in tumor cell populations during disease evolution toward a real achievement of a personalized medicine.

Hypoxia and Extracellular Acidification as Drivers of Melanoma Progression and Drug Resistance

Hypoxia and elevated extracellular acidification are prevalent features of solid tumors and they are often shown to facilitate cancer progression and drug resistance. In this review, we have compiled recent and most relevant research pertaining to the role of hypoxia and acidification in melanoma growth, invasiveness, and response to therapy. Melanoma represents a highly aggressive and heterogeneous type of skin cancer. Currently employed treatments, including BRAF V600E inhibitors and immune therapy, often are not effective due to a rapidly developing drug resistance. A variety of intracellular mechanisms impeding the treatment were discovered. However, the tumor microenvironment encompassing stromal and immune cells, extracellular matrix, and physicochemical conditions such as oxygen level or acidity, may also influence the therapy effectiveness. Hypoxia and acidification are able to reprogram the metabolism of melanoma cells, enhance their survival and invasiveness, as well as promote the immunosuppressive environment. For this reason, these physicochemical features of the melanoma niche and signaling pathways related to them emerge as potential therapeutic targets.

A MAPK/miR-29 Axis Suppresses Melanoma by Targeting MAFG and MYBL2

The miR-29 family of microRNAs is encoded by two clusters, miR-29b1~a and miR-29b2~c, and is regulated by several oncogenic and tumor suppressive stimuli. While in vitro evidence suggests a tumor suppressor role for miR-29 in melanoma, the mechanisms underlying its deregulation and contribution to melanomagenesis have remained elusive. Using various in vitro systems, we show that oncogenic MAPK signaling paradoxically stimulates transcription of pri-miR-29b1~a and pri-miR-29b2~c, the latter in a p53-dependent manner. Expression analyses in melanocytes, melanoma cells, nevi, and primary melanoma revealed that pri-miR-29b2~c levels decrease during melanoma progression. Inactivation of miR-29 in vivo with a miRNA sponge in a rapid melanoma mouse model resulted in accelerated tumor development and decreased overall survival, verifying tumor suppressive potential of miR-29 in melanoma. Through integrated RNA sequencing, target prediction, and functional assays, we identified the transcription factors MAFG and MYBL2 as bona fide miR-29 targets in melanoma. Our findings suggest that attenuation of miR-29b2~c expression promotes melanoma development, at least in part, by derepressing MAFG and MYBL2.

Decoding Immune Heterogeneity of Melanoma and identifying immune-prognostic hub genes

Melanoma is an aggressive skin cancer that has gained attention worldwide. Growing evidence has highlighted that the tumor microenvironment (TME) is an important feature of carcinogenesis and contributes to therapeutic efficacy in melanoma. However, additional advances in melanoma immuno-oncology are necessary to achieve a comprehensive knowledge of the immune infiltrate population and to identify accurate and readily measurable biomarkers. In this study, we analyzed gene expression of 468 melanoma cases from the TCGA database, which led to the identification of three melanoma clusters (representedby low, median and high infiltration) that display unique immune features. We found that the microenvironment clusters had substantial prognostic efficacy. The median cluster was characterized by an inability to draw immune cells, highlighting possible immune escape mechanisms, and lower CXCL9 and CXCL10 expression, which was correlated to poor prognosis. Deep molecular characterization of immune cells, cytolytic-activity and tumor-inflammatory status revealed diversity of the local immune infiltration landscape in the melanoma clusters. Differentially expressed genes related to TME were extracted from each infiltration cluster. Functional annotations revealed that these genes were mainly related to immune system activation and the processes of immunoreaction. The top ten hub genes in immune infiltration-related protein-protein interaction (PPI) networks were selected for further prognostic investigation. Further validation showed that five of ten hub genes were good prognostic biomarkers for melanoma in two independent groups from the Gene Expression Omnibus database. In brief, these data highlight that systemic characterization of melanoma could uncover tumor infiltrate characteristics, which can help select the most adequate treatment and identify consistent and important indicators of the local immune tumor microenvironment in melanoma patients.

The Influence of Tumor Microenvironment on Immune Escape of Melanoma

The low efficiency of currently-used anti-cancer therapies poses a serious challenge, especially in the case of malignant melanoma, a cancer characterized by elevated invasiveness and relatively high mortality rate. The role of the tumor microenvironment in the progression of melanoma and its acquisition of resistance to treatment seems to be the main focus of recent studies. One of the factors that, in normal conditions, aids the organism in its fight against the cancer and, following the malignant transformation, adapts to facilitate the development of the tumor is the immune system. A variety of cell types, i.e., T and B lymphocytes, macrophages, and dendritic and natural killer cells, as well as neutrophils, support the growth and invasiveness of melanoma cells, utilizing a plethora of mechanisms, including secretion of pro-inflammatory molecules, induction of inhibitory receptors expression, or depletion of essential nutrients. This review provides a comprehensive summary of the processes regulated by tumor-associated cells that promote the immune escape of melanoma cells. The described mechanisms offer potential new targets for anti-cancer treatment and should be further studied to improve currently-employed therapies.

Immune Microenvironment Related Competitive Endogenous RNA Network as Powerful Predictors for Melanoma Prognosis Based on WGCNA Analysis

Cutaneous melanoma is the most life-threatening skin malignant tumor due to its increasing metastasis and mortality rate. The abnormal competitive endogenous RNA network promotes the development of tumors and becomes biomarkers for the prognosis of various tumors. At the same time, the tumor immune microenvironment (TIME) is of great significance for tumor outcome and prognosis. From the perspective of TIME and ceRNA network, this study aims to explain the prognostic factors of cutaneous melanoma systematically and find novel and powerful biomarkers for target therapies. We obtained the transcriptome data of cutaneous melanoma from The Cancer Genome Atlas (TCGA) database, 3 survival-related mRNAs co-expression modules and 2 survival-related lncRNAs co-expression modules were identified through weighted gene co-expression network analysis (WCGNA), and 144 prognostic miRNAs were screened out by univariate Cox proportional hazard regression. Cox regression model and Kaplan-Meier survival analysis were employed to identify 4 hub prognostic mRNAs, and the prognostic ceRNA network consisting of 7 lncRNAs, 1 miRNA and 4 mRNAs was established. After analyzing the composition and proportion of total immune cells in cutaneous melanoma microenvironment through CIBERSORT algorithm, it is found through correlation analysis that lncRNA-TUG1 in the ceRNA network was closely related to the TIME. In this study, we first established cutaneous melanoma’s TIME-related ceRNA network by WGCNA. Cutaneous melanoma prognostic markers have been identified from multiple levels, which has important guiding significance for clinical diagnosis, treatment, and further scientific research on cutaneous melanoma.

Hypoxic Melanoma Cells Deliver microRNAs to Dendritic Cells and Cytotoxic T Lymphocytes through Connexin-43 Channels

Alterations in microRNA (miRNA) profiles, induced by tumor microenvironment stressors, like hypoxia, allow cancer cells to acquire immune-resistance phenotypes. Indeed, hypoxia-induced miRNAs have been implicated in cancer progression through numerous cancer cell non-autonomous mechanisms, including the direct transfer of hypoxia-responsive miRNA from cancer to immune cells via extracellular vesicles. Connexin-43 (Cx43)-constituted gap junctions (GJs) have also been involved in miRNA intercellular mobilization, in other biological processes. In this report, we aimed to evaluate the involvement of Cx43-GJs in the shift of miRNAs induced by hypoxia, from hypoxic melanoma cells to dendritic cells and melanoma-specific cytotoxic T lymphocytes (CTLs). Using qRT-PCR arrays, we identified that miR-192-5p was strongly induced in hypoxic melanoma cells. Immune cells acquired this miRNA after co-culture with hypoxic melanoma cells. The transfer of miR-192-5p was inhibited when hypoxic melanoma cells expressed a dominant negative Cx43 mutant or when Cx43 expression was silenced using specific short-hairpin RNAs. Interestingly, miR-192-5p levels on CTLs after co-culture with hypoxic melanoma cells were inversely correlated with the cytotoxic activity of T cells and with ZEB2 mRNA expression, a validated immune-related target of miR-192-5p, which is also observed in vivo. Altogether, our data suggest that hypoxic melanoma cells may suppress CTLs cytotoxic activity by transferring hypoxia-induced miR-192-5p through a Cx43-GJs driven mechanism, constituting a resistance strategy for immunological tumor escape.

Cancer stem cells, epigenetics, tumor microenvironment and future therapeutics in cutaneous malignant melanoma: a review

This review provides an overview of the current understanding of the ontogeny and biology of melanoma stem cells in cutaneous malignant melanoma. This article also summarizes and evaluates the current knowledge of the underlying epigenetic mechanisms, the regulation of melanoma progress by the tumor microenvironment as well as the therapeutic implications and applications of these novel insights, in the setting of personalized medicine. Unraveling the complex ecosystem of cutaneous malignant melanoma and the interplay between its components, aims to provide novel insights into the establishment of efficient therapeutic strategies.

Hsa_circ_0008945 promoted breast cancer progression by targeting miR-338-3p

PURPOSE

To detect the expression and function of circ_0008945 in breast cancer (BC) and to explore its potential molecular mechanisms in BC tumorigenesis.

MATERIALS AND METHODS

We measured expression levels of circ_0008945, miR-338-3p and homeobox A3 (HOXA3) in BC tissue specimens and cells using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). We examined the effects of all three genes on BC cell proliferation using Cell Counting Kit-8 (CCK-8) and colony formation assays. We also performed a Transwell assay to assess the migratory and invasive ability of treated BC cells. BC cell apoptosis was assessed using flow cytometric (FCM) analysis; interaction between miR-338-3p and circ_0008945 or HOXA3 was verified by dual-luciferase reporter assay as well as by ribonucleic-acid (RNA) pulldown. Finally, we used an in vivo tumor growth assay to assess the role of circ_0008945 overexpression in BC tumor growth.

RESULTS

We found that circ_0008945 expression was significantly increased in both BC tissue specimens and cells. This increase was correlated with poor prognosis in BC patients. Knockdown of circ_0008945 inhibited BC cell proliferation, migration and invasion while promoting BC cell apoptosis in vitro. Overexpression of circ_0008945 remarkably promoted BC tumor growth in vivo. Mechanistically, circ_0008945 acted as a miRNA sponge for miR-338-3p and inhibited its expression in BC cells. Moreover, miR-338-3p targeted and inhibited HOXA3.

CONCLUSION

We found that circ_0008945 acted as a BC oncogene by physically binding miR-338-3p, which further targeted and regulated HOXA3.

Unraveling the crosstalk between melanoma and immune cells in the tumor microenvironment

Cutaneous melanoma is the most common skin cancer with an incidence that has been rapidly increasing in the past decades. Melanomas are among the most immunogenic tumors and, as such, have the greatest potential to respond favorably to immunotherapy. However, like many cancers, melanomas acquire various suppressive mechanisms, which generally act in concert, to escape innate and adaptive immune detection and destruction. Intense research into the cellular and molecular events associated with melanomagenesis, which ultimately lead to immune suppression, has resulted in the discovery of new therapeutic targets and synergistic combinations of immunotherapy, targeted therapy and chemotherapy. Tremendous effort to determine efficacy of single and combination therapies in pre-clinical and clinical phase I-III trials has led to FDA-approval of several immunotherapeutic agents that could potentially be beneficial for aggressive, highly refractory, advanced and metastatic melanomas. The increasing availability of approved combination therapies for melanoma and more rapid assessment of patient tumors has increased the feasibility of personalized treatment to overcome patient and tumor heterogeneity and to achieve greater clinical benefit. Here, we review the evolution of the immune system during melanomagenesis, mechanisms exploited by melanoma to suppress anti-tumor immunity and methods that have been developed to restore immunity. We emphasize that an effective therapeutic strategy will require coordinate activation of tumor-specific immunity as well as increased recognition and accessibility of melanoma cells in primary tumors and distal metastases. This review integrates available knowledge on melanoma-specific immunity, molecular signaling pathways and molecular targeting strategies that could be utilized to envision therapeutics with broader application and greater efficacy for early stage and advanced metastatic melanoma.

Comprehensive analysis of prognostic immune-related genes in the tumor microenvironment of cutaneous melanoma

Cutaneous malignant melanoma (hereafter called melanoma) is one of the most aggressive cancers with increasing incidence and mortality rates worldwide. In this study, we performed a systematic investigation of the tumor microenvironmental and genetic factors associated with melanoma to identify prognostic biomarkers for melanoma. We calculated the immune and stromal scores of melanoma patients from the Cancer Genome Atlas (TCGA) using the ESTIMATE algorithm and found that they were closely associated with patients' prognosis. Then the differentially expressed genes were obtained based on the immune and stromal scores, and prognostic immune-related genes further identified. Functional analysis and the protein-protein interaction network further revealed that these genes enriched in many immune-related biological processes. In addition, the abundance of six infiltrating immune cells was analyzed using prognostic immune-related genes by TIMER algorithm. The unsupervised clustering analysis using immune-cell proportions revealed eight clusters with distinct survival patterns, suggesting that dendritic cells were most abundant in the microenvironment and CD8⁺ T cells and neutrophils were significantly related to patients' prognosis. Finally, we validated these genes in three independent cohorts from the Gene Expression Omnibus database. In conclusion, this study comprehensively analyzed the tumor microenvironment and identified prognostic immune-related biomarkers for melanoma.

Interactive functions of microRNAs in the miR-23a-27a-24-2 cluster and the potential for targeted therapy in cancer

MicroRNAs (miRNAs) are small noncoding RNAs about 19-22 nucleotides in length. Growing evidence has reported the significant role of miRNAs in various cancer-associated biological processes, such as proliferation, differentiation, apoptosis, metabolism, invasion, metastasis, and drug resistance. However, most studies focus on the targets of some individual miRNAs; the interactive and global functions of diverse miRNAs are still unclear and the phenomenon of the gathering of miRNAs in clusters has always been ignored. On the other hand, the fact that a single miRNA may regulate many genes and that numerous mRNAs are regulated by the same miRNA also makes it imperative to further study the cooperating characteristics of miRNAs in cancer. MiR-23a-27a-24-2 is located in the human chromosome 9q22, forming three mature miRNAs: miR-23a, miR27a, and miR-24, which are expressed abnormally in many malignant tumors. This review aims to summarize the interactive functions of miRNAs in miR-23a-27a-24-2 clusters in cancer from the perspectives of the regulation network, tumor microenvironment, and targeted therapy.

TGF-β-Mediated Epithelial-Mesenchymal Transition and Cancer Metastasis

Transforming growth factor β (TGF-β) is a secreted cytokine that regulates cell proliferation, migration, and the differentiation of a plethora of different cell types. Consistent with these findings, TGF-β plays a key role in controlling embryogenic development, inflammation, and tissue repair, as well as in maintaining adult tissue homeostasis. TGF-β elicits a broad range of context-dependent cellular responses, and consequently, alterations in TGF-β signaling have been implicated in many diseases, including cancer. During the early stages of tumorigenesis, TGF-β acts as a tumor suppressor by inducing cytostasis and the apoptosis of normal and premalignant cells. However, at later stages, when cancer cells have acquired oncogenic mutations and/or have lost tumor suppressor gene function, cells are resistant to TGF-β-induced growth arrest, and TGF-β functions as a tumor promotor by stimulating tumor cells to undergo the so-called epithelial-mesenchymal transition (EMT). The latter leads to metastasis and chemotherapy resistance. TGF-β further supports cancer growth and progression by activating tumor angiogenesis and cancer-associated fibroblasts and enabling the tumor to evade inhibitory immune responses. In this review, we will consider the role of TGF-β signaling in cell cycle arrest, apoptosis, EMT and cancer cell metastasis. In particular, we will highlight recent insights into the multistep and dynamically controlled process of TGF-β-induced EMT and the functions of miRNAs and long noncoding RNAs in this process. Finally, we will discuss how these new mechanistic insights might be exploited to develop novel therapeutic interventions.

Integrative Analysis of Long Noncoding RNA (lncRNA), microRNA (miRNA) and mRNA Expression and Construction of a Competing Endogenous RNA (ceRNA) Network in Metastatic Melanoma

Worldwide, metastatic melanoma of the skin has an aggressive course with high morbidity and mortality. Therefore, an increased understanding of the pathogenesis of metastatic melanoma has gained increasing attention, including the role of epigenetic modification and competing endogenous RNA (ceRNA). This study aimed to used bioinformatics data to undertake an integrative analysis of long noncoding RNA (lncRNA), microRNA (miRNA) and mRNA expression to construct a ceRNA network in metastatic melanoma. Data from the Cancer Genome Atlas (TCGA), the Gene Ontology (GO) database, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway were analyzed. There were 471 cases that included 103 primary solid tumors and 368 cases of metastatic melanoma that included transcriptome sequencing data (including lncRNA and mRNA); 452 cases had miRNA sequencing data. Analysis of chip data identified 85 6 mRNAs, 67 miRNAs, and 250 lncRNAs that were differentially expressed in cases of metastatic melanoma, of which 25 miRNAs, 18 lncRNAs, and 18 mRNAs participated in the formation of ceRNAs. Survival analysis identified seven differentially expressed mRNAs, five differentially expressed miRNAs (miRNA-29c, miRNA-100, miR-142-3p, miR-150, miR-516a-2), and six differentially expressed lncRNAs (AC068594.1, C7orf71, FAM41C, GPC5-AS1, MUC19, LINC00402) that were correlated with survival time in patients with metastatic melanoma. Bioinformatics data and integrative analysis identified lncRNA, miRNA, and mRNA expression to construct a ceRNA and patient survival network in metastatic melanoma. These findings support the need for further studies on the mechanisms involved in the regulation of metastatic melanoma by ceRNAs.

Knockdown of Delta-like 3 restricts lipopolysaccharide-induced inflammation, migration and invasion of A2058 melanoma cells via blocking Twist1-mediated epithelial-mesenchymal transition

AIMS

To investigate the effects and mechanisms of DLL3 in inflammation-mediated A2058 melanoma cell invasion and metastasis.

MATERIALS AND METHODS

Melanoma A2058 cells was stimulated with lipopolysaccharide (LPS), with or without transfection of DLL3 siRNA, or DLL3 overexpression vector, or Twist1 siRNA. Cell migration and invasion were detected by wound healing and transwell invasion assay. The production of inflammatory factors TNF-α and IL-6 was measured by ELISA. The expression of Notch signaling-related molecules was detected by PCR and western blot. The protein expression of MMP1, MMP9, VEGF, DLL3, and EMT-related molecules was tested by western blot.

KEY FINDINGS

LPS treatment increased migration and invasion of A2058 cells, accompanied by increased expression of TNF-α and IL-6. DLL3 was both upregulated in the LPS- or TNF-α-stimulated A2058 cells, and DLL3 knockdown inhibited LPS-induced inflammation, migration and invasion of A2058 cells, accompanied by down-regulation of MMP1, MMP9 and VEGF. Besides, DLL3 knockdown inhibits the expression of Twist1, a key EMT regulating factor, as well as the EMT hallmarks slug, N-cadherin and vimentin. Moreover, Twist1 silence inhibited EMT, and limited LPS-induced migration and invasion of A2058 cells, with decreased expression of MMP1, MMP9 and VEGF and reduced production of TNF-α and IL-6 in LPS-stimulated A2058 cells.

SIGNIFICANCE

Knockdown of DLL3 restricts LPS-induced inflammation, migration and invasion of A2058 melanoma cells via blocking Twist1-mediated EMT. Therefore, targeting DLL3 may be a promising therapeutic strategy against inflammation-aggravated melanoma progression.

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.

Bad company: Microenvironmentally mediated resistance to targeted therapy in melanoma

This review will focus on the role of the tumor microenvironment (TME) in the development of drug resistance in melanoma. Resistance to mitogen-activated protein kinase inhibitors (MAPKi) in melanoma is observed months after treatment, a phenomenon that is often attributed to the incredible plasticity of melanoma cells but may also depend on the TME. The TME is unique in its cellular composition-it contains fibroblasts, immune cells, endothelial cells, adipocytes, and among others. In addition, the TME provides "non-homeostatic" levels of oxygen, nutrients (hypoxia and metabolic stress), and extracellular matrix proteins, creating a pro-tumorigenic niche that drives resistance to MAPKi treatment. In this review, we will focus on how changes in the tumor microenvironment regulate MAPKi resistance.

Application of the Transcriptional Disease Signature (TDSs) to Screen Melanoma-Effective Compounds in a Small Fish Model

Cell culture and protein target-based compound screening strategies, though broadly utilized in selecting candidate compounds, often fail to eliminate candidate compounds with non-target effects and/or safety concerns until late in the drug developmental process. Phenotype screening using intact research animals is attractive because it can help identify small molecule candidate compounds that have a high probability of proceeding to clinical use. Most FDA approved, first-in-class small molecules were identified from phenotypic screening. However, phenotypic screening using rodent models is labor intensive, low-throughput, and very expensive. As a novel alternative for small molecule screening, we have been developing gene expression disease profiles, termed the Transcriptional Disease Signature (TDS), as readout of small molecule screens for therapeutic molecules. In this concept, compounds that can reverse, or otherwise affect known disease-associated gene expression patterns in whole animals may be rapidly identified for more detailed downstream direct testing of their efficacy and mode of action. To establish proof of concept for this screening strategy, we employed a transgenic strain of a small aquarium fish, medaka (Oryzias latipes), that overexpresses the malignant melanoma driver gene xmrk, a mutant egfr gene, that is driven by a pigment cell-specific mitf promoter. In this model, melanoma develops with 100% penetrance. Using the transgenic medaka malignant melanoma model, we established a screening system that employs the NanoString nCounter platform to quantify gene expression within custom sets of TDS gene targets that we had previously shown to exhibit differential transcription among xmrk-transgenic and wild-type medaka. Compound-modulated gene expression was identified using an internet-accessible custom-built data processing pipeline. The effect of a given drug on the entire TDS profile was estimated by comparing compound-modulated genes in the TDS using an activation Z-score and Kolmogorov-Smirnov statistics. TDS gene probes were designed that target common signaling pathways that include proliferation, development, toxicity, immune function, metabolism and detoxification. These pathways may be utilized to evaluate candidate compounds for potential favorable, or unfavorable, effects on melanoma-associated gene expression. Here we present the logistics of using medaka to screen compounds, as well as, the development of a user-friendly NanoString data analysis pipeline to support feasibility of this novel TDS drug-screening strategy.

Association of miR-1247-5p expression with clinicopathological parameters and prognosis in breast cancer

Our study aimed to clarify the correlation between miR‐1247‐5p expression and clinicopathological parameters and survival of patients with breast cancer (BC). We evaluated the expression level of miR‐1247‐5p in 224 formalin‐fixed, paraffin‐embedded specimens (112 BC and matched cancer free tissues) by quantitative real‐time reverse transcriptase polymerase chain reaction (qRT‐PCR). miR‐1247‐5p expression in BC tissues was found to be decreased compared with matched normal tissues (P < 0.01). Additionally, low miR‐1247‐5p expression in BC tissues was significantly associated with the advanced TNM stage (P = 0.007), lymph node metastasis (P = 0.015), poorer pathological differentiation (P = 0.005) and molecular subtype (P = 0.027). The patients in the low miR‐1247‐5p group had a shorter disease‐free survival and overall survival than those in the high miR‐1247‐5p group (P < 0.01). Furthermore, the univariate and the multivariate analyses showed that miR‐1247‐5p expression was an independent predictor of overall survival (P < 0.01). Our study showed that miR‐1247‐5p was related to the biological behaviour of breast tumour and prognosis of patients with BC. miR‐1247‐5p could be a novel tumour suppressor and act as a potential biomarker and therapeutic agent for breast carcinoma.

Targeting PDK4 inhibits breast cancer metabolism

Dysregulated metabolism in the form of aerobic glycolysis occurs in many cancers including breast carcinoma. Here, we report PDK4 (pyruvate dehydrogenase kinase 4) as key enzyme implicated in the control of glucose metabolism and mitochondrial respiration is relatively highly expressed in breast cancers, and its expression correlates with poor patient outcomes. Silencing of PDK4 and ectopic expression of miR-211 attenuates PDK4 expression in breast cancer cells. Interestingly, low miR-211 expression is significantly associated with shorter overall survival and reveals an inverse correlation between expression of miR-211 and PDK4. We have found that depletion of PDK4 by miR-211 shows an oxidative phosphorylation-dominant phenotype consisting of the reduction of glucose with increased expression of PDH and key enzymes of the TCA cycle. miR-211 expression causes alteration of mitochondrial membrane potential and induces mitochondrial apoptosis as observed via IPAD assay. Further, by inhibiting PDK4 expression, miR-211 promotes a phenotype shift towards a pro-glycolytic state evidenced by decreased extracellular acidification rate (ECAR); increased oxygen consumption rate (OCR); and increased spare respiratory capacity in breast cancer cell lines. Taken together this data establishes a molecular connection between PDK4 and miR-211 and suggests that targeting miR-211 to inhibit PDK4 could represent a novel therapeutic strategy in breast cancers.

Circulating MicroRNA Biomarkers in Melanoma: Tools and Challenges in Personalised Medicine

Effective management of melanoma depends heavily on early diagnosis. When detected in early non-metastatic stages, melanoma is almost 100% curable by surgical resection, however when detected in late metastatic stages III and IV, 5-year survival rates drop to ~50% and 10–25%, respectively, due to limited efficacy of current treatment options. This presents a pressing need to identify biomarkers that can detect patients at high risk of recurrence and progression to metastatic disease, which will allow for early intervention and survival benefit. Accumulating evidence over the past few decades has highlighted the potential use of circulating molecular biomarkers for melanoma diagnosis and prognosis, including lactate dehydrogenase (LDH), S100 calcium-binding protein B (S100B) and circulating tumor DNA (ctDNA) fragments. Since 2010, circulating microRNAs (miRNAs) have been increasingly recognised as more robust non-invasive biomarkers for melanoma due to their structural stability under the harsh conditions of the blood and different conditions of sample processing and isolation. Several pre-analytical and analytical variables challenge the accurate quantification of relative miRNA levels between serum samples or plasma samples, leading to conflicting findings between studies on circulating miRNA biomarkers for melanoma. In this review, we provide a critical summary of the circulating miRNA biomarkers for melanoma published to date.

Tumor exosomes: a double-edged sword in cancer therapy

Tumor cells produce and secrete more nucleic acids, proteins and lipids than normal cells. These molecules are transported in the blood or around the cells in membrane-encapsulated exosomes. Tumor-derived or tumor-associated exosomes (usually 30-100 nm in diameter) contain abundant biological contents resembling those of the parent cells along with signaling messengers for intercellular communication involved in the pathogenesis, development, progression, and metastasis of cancer. As these exosomes can be detected and isolated from various body fluids, they have become attractive new biomarkers for the diagnosis and prognosis of cancer. Furthermore, tumor exosomes have also attracted increasing attention due to their potential as novel therapeutic strategies for the treatment of cancers. On the one hand, the lipid bilayer membrane-encapsulated vesicles are promising carriers of drugs and other therapeutic materials targeting specific cancer cells. On the other hand, tumor exosomes are important mediators for modulation of the microenvironment that orchestrates events critical to the growth and metastasis of cancer cells as well as chemoresistance. Here, we summarize the advances in our understanding of tumor-associated or tumor-derived exosomes in recent years, and discuss their roles in cancer development, progression, invasion, and metastasis of cancers and, more importantly, their potential in strategies for precision therapy of various cancers as well as important caveats.

Advances in Proteomic Techniques for Cytokine Analysis: Focus on Melanoma Research

Melanoma is a skin cancer with permanently increasing incidence and resistance to therapies in advanced stages. Reports of spontaneous regression and tumour infiltration with T-lymphocytes makes melanoma candidate for immunotherapies. Cytokines are key factors regulating immune response and intercellular communication in tumour microenvironment. Cytokines may be used in therapy of melanoma to modulate immune response. Cytokines also possess diagnostic and prognostic potential and cytokine production may reflect effects of immunotherapies. The purpose of this review is to give an overview of recent advances in proteomic techniques for the detection and quantification of cytokines in melanoma research. Approaches covered span from mass spectrometry to immunoassays for single molecule detection (ELISA, western blot), multiplex assays (chemiluminescent, bead-based (Luminex) and planar antibody arrays), ultrasensitive techniques (Singulex, Simoa, immuno-PCR, proximity ligation/extension assay, immunomagnetic reduction assay), to analyses of single cells producing cytokines (ELISpot, flow cytometry, mass cytometry and emerging techniques for single cell secretomics). Although this review is focused mainly on cancer and particularly melanoma, the discussed techniques are in general applicable to broad research field of biology and medicine, including stem cells, development, aging, immunology and intercellular communication.