Upregulation of MicroRNA-1246 Is Associated with BRAF Inhibitor Resistance in Melanoma Cells with Mutant BRAF

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.

METTL3 promotes non-small-cell lung cancer growth and metastasis by inhibiting FDX1 through copper death-associated pri-miR-21-5p maturation

Objective: We probed into the significance of METTL3 in the maturation process of pri-miR-21-5p. We specifically investigated its impact on the regulation of FDX1 and its involvement in the progression of non-small-cell lung cancer (NSCLC). Methods: The Cancer Genome Atlas (TCGA) identified NSCLC factors. Methylation-specific PCR (MSP), clonogenic tests and flow cytometry analyzed cells. Methylated RNA immunoprecipitation (Me-RIP) and dual-luciferase studied miR-21-5p/FDX1. Mice xenografts showed METTL3's tumorigenic effect. Results: METTL3, with high expression but low methylation in NSCLC, influenced cell behaviors. Its suppression reduced oncogenic properties. METTL3 enhanced miR-21-5p maturation, targeting FDX1 and boosting NSCLC tumorigenicity in mice. Conclusion: METTL3 may promote NSCLC development by facilitating pri-miR-21-5p maturation, upregulating miR-21-5p and targeting inhibition of FDX1.

BRAF Mutations in Melanoma: Biological Aspects, Therapeutic Implications, and Circulating Biomarkers

Melanoma is an aggressive form of skin cancer resulting from the malignant transformation of melanocytes. Recent therapeutic approaches, including targeted therapy and immunotherapy, have improved the prognosis and outcome of melanoma patients. BRAF is one of the most frequently mutated oncogenes recognised in melanoma. The most frequent oncogenic BRAF mutations consist of a single point mutation at codon 600 (mostly V600E) that leads to constitutive activation of the BRAF/MEK/ERK (MAPK) signalling pathway. Therefore, mutated BRAF has become a useful target for molecular therapy and the use of BRAF kinase inhibitors has shown promising results. However, several resistance mechanisms invariably develop leading to therapeutic failure. The aim of this manuscript is to review the role of BRAF mutational status in the pathogenesis of melanoma and its impact on differentiation and inflammation. Moreover, this review focuses on the mechanisms responsible for resistance to targeted therapies in BRAF-mutated melanoma and provides an overview of circulating biomarkers including circulating tumour cells, circulating tumour DNA, and non-coding RNAs.

Autophagy in BRAF-mutant cutaneous melanoma: recent advances and therapeutic perspective

Macroautophagy, hereafter referred to as autophagy, represents a highly conserved catabolic process that maintains cellular homeostasis. At present, the role of autophagy in cutaneous melanoma (CM) is still controversial, since it appears to be tumor-suppressive at early stages of malignant transformation and cancer-promoting during disease progression. Interestingly, autophagy has been found to be often increased in CM harboring BRAF mutation and to impair the response to targeted therapy. In addition to autophagy, numerous studies have recently conducted in cancer to elucidate the molecular mechanisms of mitophagy, a selective form of mitochondria autophagy, and secretory autophagy, a process that facilitates unconventional cellular secretion. Although several aspects of mitophagy and secretory autophagy have been investigated in depth, their involvement in BRAF-mutant CM biology has only recently emerged. In this review, we aim to overview autophagy dysregulation in BRAF-mutant CM, along with the therapeutic advantages that may arise from combining autophagy inhibitors with targeted therapy. In addition, the recent advances on mitophagy and secretory autophagy involvement in BRAF-mutant CM will be also discussed. Finally, since a number of autophagy-related non-coding RNAs (ncRNAs) have been identified so far, we will briefly discussed recent advances linking ncRNAs to autophagy regulation in BRAF-mutant CM.

Tumor microenvironment responded naturally extracted FOF1-ATPase loaded chromatophores for antitumor therapy

Tumor microenvironment (TME) plays an important role in the growth, invasion, and metastasis of tumor cells. The pH of TME is more acidic in solid tumors than in normal tissues. Although targeted delivery in TME has progressed, the complex and expensive construction of delivery systems has limited their application. F_OF1-ATP synthase (F_OF1-ATPase) is a rotation molecular motor found in bacteria, chloroplasts, and mitochondria. Here, F_OF1-ATPase loaded chromatophores (chroma) isolated from thermophilic bacteria were extracted and utilized as a new delivery system targeting TME for the first time. Curcumin as model drug was successfully loaded by a filming-rehydration ultrasonic dispersion method to prepare a curcumin-loaded chroma delivery system (Cur-Chroma). The mobility and propensity distributions of Cur-Chroma reveal its specific pH-sensitive targeting driven by the transmembrane proton kinetic potential, demonstrating its distinct distribution in the TME and more favorable targeting delivery. Cellular uptake experiments indicated that Cur-Chroma entered cells through grid pathway-mediated endocytosis. In vivo studies have shown that Cur-Chroma can specifically target tumor tissue and effectively inhibit tumor growth with good safety. Curcumin's bioavailability and anti-tumor effects were significantly improved. These studies demonstrate that ATPase-loaded chromatophores are potentially ideal vehicles for anti-tumor drug delivery and have promising applications.

MITF Downregulation Induces Death in Human Mast Cell Leukemia Cells and Impairs IgE-Dependent Degranulation

Activating mutations in KIT (CD117) have been associated with several diseases, including gastrointestinal stromal tumors and mastocytosis. Rapidly progressing pathologies or drug resistance highlight the need for alternative treatment strategies. Previously, we reported that the adaptor molecule SH3 binding protein 2 (SH3BP2 or 3BP2) regulates KIT expression at the transcriptional level and microphthalmia-associated transcription factor (MITF) expression at the post-transcriptional level in human mast cells and gastrointestinal stromal tumor (GIST) cell lines. Lately, we have found that the SH3BP2 pathway regulates MITF through miR-1246 and miR-5100 in GIST. In this study, miR-1246 and miR-5100 were validated by qPCR in the SH3BP2-silenced human mast cell leukemia cell line (HMC-1). MiRNA overexpression reduces MITF and MITF-dependent target expression in HMC-1. The same pattern was observed after MITF silencing. In addition, MITF inhibitor ML329 treatment reduces MITF expression and affects the viability and cell cycle progression in HMC-1. We also examine whether MITF downregulation affected IgE-dependent mast cell degranulation. MiRNA overexpression, MITF silencing, and ML329 treatment reduced IgE-dependent degranulation in LAD2- and CD34⁺-derived mast cells. These findings suggest MITF may be a potential therapeutic target for allergic reactions and deregulated KIT mast-cell-mediated disorders.

SH3BP2 Silencing Increases miRNAs Targeting ETV1 and Microphthalmia-Associated Transcription Factor, Decreasing the Proliferation of Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Gain of function in receptor tyrosine kinases type III, KIT, or PDGFRA drives the majority of GIST. Previously, our group reported that silencing of the adaptor molecule SH3 Binding Protein 2 (SH3BP2) downregulated KIT and PDGFRA and microphthalmia-associated transcription factor (MITF) levels and reduced tumor growth. This study shows that SH3BP2 silencing also decreases levels of ETV1, a required factor for GIST growth. To dissect the SH3BP2 pathway in GIST cells, we performed a miRNA array in SH3BP2-silenced GIST cell lines. Among the most up-regulated miRNAs, we found miR-1246 and miR-5100 to be predicted to target MITF and ETV1. Overexpression of these miRNAs led to a decrease in MITF and ETV1 levels. In this context, cell viability and cell cycle progression were affected, and a reduction in BCL2 and CDK2 was observed. Interestingly, overexpression of MITF enhanced cell proliferation and significantly rescued the viability of miRNA-transduced cells. Altogether, the KIT-SH3BP2-MITF/ETV1 pathway deserves to be considered in GIST cell survival and proliferation.

Paradoxical downregulation of LPAR3 exerts tumor-promoting activity through autophagy induction in Ras-transformed cells

Background

Lysophosphatidic acid receptor 3 (LPAR3) is coupled to Gα_i/o and Gα_11/q signaling. Previously, we reported that LPAR3 is highly methylated in carcinogen-induced transformed cells. Here, we demonstrate that LPAR3 exhibits malignant transforming activities, despite being downregulated in transformed cells.

Methods

The LPAR3 knockout (KO) in NIH 3 T3 and Bhas 42 cells was established using the CRISPR/Cas9 system. Both RT-PCR and DNA sequencing were performed to confirm the KO of LPAR3. The cellular effects of LPAR3 KO were further examined by WST-1 assay, immunoblotting analysis, transwell migration assay, colony formation assay, wound scratch assday, in vitro cell transformation assay, and autophagy assay.

Results

In v-H-ras-transformed cells (Ras-NIH 3 T3) with LPAR3 downregulation, ectopic expression of LPAR3 significantly enhanced the migration. In particular, LPAR3 knockout (KO) in Bhas 42 (v-Ha-ras transfected Balb/c 3 T3) and NIH 3 T3 cells caused a decrease in cell survival, transformed foci, and colony formation. LPAR3 KO led to the robust accumulation of LC3-II and autophagosomes and inhibition of autophagic flux by disrupting autophagosome fusion with lysosome. Conversely, autolysosome maturation proceeded normally in Ras-NIH 3 T3 cells upon LPAR3 downregulation. Basal phosphorylation of MEK and ERK markedly increased in Ras-NIH 3 T3 cells, whereas being significantly lower in LPAR3 KO cells, suggesting that increased MEK signaling is involved in autophagosome–lysosome fusion in Ras-NIH 3 T3 cells.

Conclusions

Paradoxical downregulation of LPAR3 exerts cooperative tumor-promoting activity with MEK activation through autophagy induction in Ras-transformed cells. Our findings have implications for the development of cancer chemotherapeutic approaches.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-10053-0.

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.

A Review on the Role of miR-1246 in the Pathoetiology of Different Cancers

miR-1246 is a microRNA firstly recognized through application of a high throughput sequencing technique in human embryonic stem cells. Subsequent studies have shown the role of this microRNA in the carcinogenesis. miR-1246 has been found to exert oncogenic roles in colorectal, breast, renal, oral, laryngeal, pancreatic and ovarian cancers as well as melanoma and glioma. In lung, cervical and liver cancers, studies have reported contradictory results regarding the role of miR-1246. miR-1246 has been reported to regulate activity of RAF/MEK/ERK, GSK3β, Wnt/β-catenin, JAK/STAT, PI3K/AKT, THBS2/MMP and NOTCH2 pathways. In addition to affecting cell cycle progression and proliferation, miR-1246 can influence stemness and resistance of cancer cells to therapeutics. In the current review, we describe the summary of in vitro and in vivo studies about the influence of miR-1246 in carcinogenesis in addition to studies that measured expression levels of miR-1246 in clinical samples.

METTL3 promotes the initiation and metastasis of ovarian cancer by inhibiting CCNG2 expression via promoting the maturation of pri-microRNA-1246

Ovarian cancer is a common gynecological malignant tumor with a high mortality rate and poor prognosis. There is inadequate knowledge of the molecular mechanisms underlying ovarian cancer. We examined the expression of methyltransferase-like 3 (METTL3) in tumor specimens using RT-qPCR, immunohistochemistry, and Western blot analysis, and tested the methylation of METTL3 by MSP. Levels of METTL3, miR-1246, pri-miR-1246 and CCNG2 were then analyzed and their effects on cell biological processes were also investigated, using in vivo assay to validate the in vitro findings. METTL3 showed hypomethylation and high expression in ovarian cancer tissues and cells. Hypomethylation of METTL3 was pronounced in ovarian cancer samples, which was negatively associated with patient survival. Decreased METTL3 inhibited the proliferation and migration of ovarian cancer cells and promoted apoptosis, while METTL3 overexpression exerted opposite effects. Mechanistically, METTL3 aggravated ovarian cancer by targeting miR-1246, while miR-1246 targeted and inhibited CCNG2 expression. High expression of METTL3 downregulated CCNG2, promoted the metabolism and growth of transplanted tumors in nude mice, and inhibited apoptosis. The current study highlights the promoting role of METTL3 in the development of ovarian cancer, and presents new targets for its treatment.

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.

Resistance to Molecularly Targeted Therapies in Melanoma

Malignant melanoma is the most aggressive type of skin cancer with invasive growth patterns. In 2021, 106,110 patients are projected to be diagnosed with melanoma, out of which 7180 are expected to die. Traditional methods like surgery, radiation therapy, and chemotherapy are not effective in the treatment of metastatic and advanced melanoma. Recent approaches to treat melanoma have focused on biomarkers that play significant roles in cell growth, proliferation, migration, and survival. Several FDA-approved molecular targeted therapies such as tyrosine kinase inhibitors (TKIs) have been developed against genetic biomarkers whose overexpression is implicated in tumorigenesis. The use of targeted therapies as an alternative or supplement to immunotherapy has revolutionized the management of metastatic melanoma. Although this treatment strategy is more efficacious and less toxic in comparison to traditional therapies, targeted therapies are less effective after prolonged treatment due to acquired resistance caused by mutations and activation of alternative mechanisms in melanoma tumors. Recent studies focus on understanding the mechanisms of acquired resistance to these current therapies. Further research is needed for the development of better approaches to improve prognosis in melanoma patients. In this article, various melanoma biomarkers including BRAF, MEK, RAS, c-KIT, VEGFR, c-MET and PI3K are described, and their potential mechanisms for drug resistance are discussed.

Carfilzomib in Combination with Bortezomib Enhances Apoptotic Cell Death in B16-F1 Melanoma Cells

Simple Summary

The incidence rate of metastatic melanoma has been rapidly increasing worldwide and its 5-year survival rate is very low. Due to partial responses, various side effects, and resistance to any known cancer therapeutics, more potent and safer therapeutics are needed to increase the survival rate of patients with melanoma. Since proteasome inhibitors, such as bortezomib and carfilzomib, have been suggested as treatments for various cancers, we investigated their potential for the treatment of melanoma by studying their molecular mechanisms of action in B16-F1 melanoma cells. In this study, we found that both bortezomib and carfilzomib lead to apoptosis via ER stress as well as ROS accumulation and MMP loss in melanoma cells. Bortezomib and carfilzomib synergistically reduced B16-F1 tumor growth in vitro and in a C57BL/6 xenograft mouse model. Therefore, a combination therapy with carfilzomib and bortezomib at submaximal concentrations may reduce their side effects and be beneficial for melanoma treatment.

Abstract

Proteasome inhibitors, such as bortezomib (BZ) and carfilzomib (CFZ), have been suggested as treatments for various cancers. To utilize BZ and/or CFZ as effective therapeutics for treating melanoma, we studied their molecular mechanisms using B16-F1 melanoma cells. Flow cytometry of Annexin V-fluorescein isothiocyanate-labeled cells indicated apoptosis induction by treatment with BZ and CFZ. Apoptosis was evidenced by the activation of various caspases, including caspase 3, 8, 9, and 12. Treatment with BZ and CFZ induced endoplasmic reticulum (ER) stress, as indicated by an increase in eIF2α phosphorylation and the expression of ER stress-associated proteins, including GRP78, ATF6α, ATF4, XBP1, and CCAAT/enhancer-binding protein homologous protein. The effects of CFZ on ER stress and apoptosis were lower than that of BZ. Nevertheless, CFZ and BZ synergistically induced ER stress and apoptosis in B16-F1 cells. Furthermore, the combinational pharmacological interactions of BZ and CFZ against the growth of B16-F1 melanoma cells were assessed by calculating the combination index and dose-reduction index with the CompuSyn software. We found that the combination of CFZ and BZ at submaximal concentrations could obtain dose reduction by exerting synergistic inhibitory effects on cell growth. Moreover, this drug combination reduced tumor growth in C57BL/6 syngeneic mice. Taken together, these results suggest that CFZ in combination with BZ may be a beneficial and potential strategy for melanoma treatment.

Mechanisms of Acquired BRAF Inhibitor Resistance in Melanoma: A Systematic Review

This systematic review investigated the literature on acquired v-raf murine sarcoma viral oncogene homolog B1 (BRAF) inhibitor resistance in patients with melanoma. We searched MEDLINE for articles on BRAF inhibitor resistance in patients with melanoma published since January 2010 in the following areas: (1) genetic basis of resistance; (2) epigenetic and transcriptomic mechanisms; (3) influence of the immune system on resistance development; and (4) combination therapy to overcome resistance. Common resistance mutations in melanoma are BRAF splice variants, BRAF amplification, neuroblastoma RAS viral oncogene homolog (NRAS) mutations and mitogen-activated protein kinase kinase 1/2 (MEK1/2) mutations. Genetic and epigenetic changes reactivate previously blocked mitogen-activated protein kinase (MAPK) pathways, activate alternative signaling pathways, and cause epithelial-to-mesenchymal transition. Once BRAF inhibitor resistance develops, the tumor microenvironment reverts to a low immunogenic state secondary to the induction of programmed cell death ligand-1. Combining a BRAF inhibitor with a MEK inhibitor delays resistance development and increases duration of response. Multiple other combinations based on known mechanisms of resistance are being investigated. BRAF inhibitor-resistant cells develop a range of 'escape routes', so multiple different treatment targets will probably be required to overcome resistance. In the future, it may be possible to personalize combination therapy towards the specific resistance pathway in individual patients.

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.

Circulating miRNAs in Small Extracellular Vesicles Secreted by a Human Melanoma Xenograft in Mouse Brains

The identification of liquid biomarkers remains a major challenge to improve the diagnosis of melanoma patients with brain metastases. Circulating miRNAs packaged into tumor-secreted small extracellular vesicles (sEVs) contribute to tumor progression. To investigate the release of tumor-secreted miRNAs by brain metastasis, we developed a xenograft model where human metastatic melanoma cells were injected intracranially in nude mice. The comprehensive profiles of both free miRNAs and those packaged in sEVs secreted by the melanoma cells in the plasma demonstrated that most (80%) of the sEV-associated miRNAs were also present in serum EVs from a cohort of metastatic melanomas, included in a publicly available dataset. Remarkably, among them, we found three miRNAs (miR-224-5p, miR-130a-3p and miR-21-5p) in sEVs showing a trend of upregulation during melanoma progression. Our model is proven to be valuable for identifying miRNAs in EVs that are unequivocally secreted by melanoma cells in the brain and could be associated to disease progression.

Roles of S100 family members in drug resistance in tumors: Status and prospects

Chemotherapy and targeted therapy can significantly improve survival rates in cancer, but multiple drug resistance (MDR) limits the efficacy of these approaches. Understanding the molecular mechanisms underlying MDR is crucial for improving drug efficacy and clinical outcomes of patients with cancer. S100 proteins belong to a family of calcium-binding proteins and have various functions in tumor development. Increasing evidence demonstrates that the dysregulation of various S100 proteins contributes to the development of drug resistance in tumors, providing a basis for the development of predictive and prognostic biomarkers in cancer. Therefore, a combination of biological inhibitors or sensitizers of dysregulated S100 proteins could enhance therapeutic responses. In this review, we provide a detailed overview of the mechanisms by which S100 family members influence resistance of tumors to cancer treatment, with a focus on the development of effective strategies for overcoming MDR.

Autophagy inhibition in 3T3-L1 adipocytes breaks the crosstalk with tumor cells by suppression of adipokine production

Several studies have revealed the functional importance of autophagy in both adipogenesis and carcinogenesis. Here, we investigated autophagy as a link between tumorigenesis and adipogenesis using 3T3-L1 cells, which have been shown to closely mimic the in vivo differentiation process. The relative levels of LC3-II/I showed that autophagy was the highest after 4–6 days of initiation of differentiation and it diminished thereafter. Furthermore, chloroquine (CQ), a late autophagy inhibitor, effectively inhibited adipogenic differentiation of 3T3-L1 cells, suggesting that autophagy may have a positive impact on adipogenic differentiation. Notably, real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis showed that CQ completely blocked the mRNA expression of three adipokines (adiponectin, leptin, and peroxisome proliferator-activated receptor-γ (PPARγ)), which increased proportionally to adipocyte differentiation. Using adipokine antibody arrays, we also found that among 38 adipokines examined, 6 adipokines were significantly differentially regulated in mature adipocytes compared to those in preadipocytes. A comparative analysis of adipokine production revealed that CQ-treated adipocytes displayed a profile similar to that of preadipocytes. Subsequently, CQ treatment significantly inhibited the migration capacity of v-Ha-ras-transformed cells in both 3T3-L1 adipocyte-conditioned medium and co-culture with 3T3-L1 using a transwell plate. Taken together, our results suggest that autophagy inhibition blocks the production of mediators relevant to the adipogenic process and may significantly contribute to reducing obesity-related cancer risk.

Choosing The Right Animal Model for Renal Cancer Research

The increase in the life expectancy of patients with renal cell carcinoma (RCC) in the last decade is due to changes that have occurred in the area of preclinical studies. Understanding cancer pathophysiology and the emergence of new therapeutic options, including immunotherapy, would not be possible without proper research. Before new approaches to disease treatment are developed and introduced into clinical practice they must be preceded by preclinical tests, in which animal studies play a significant role. This review describes the progress in animal model development in kidney cancer research starting from the oldest syngeneic or chemically-induced models, through genetically modified mice, finally to xenograft, especially patient-derived, avatar and humanized mouse models. As there are a number of subtypes of RCC, our aim is to help to choose the right animal model for a particular kidney cancer subtype. The data on genetic backgrounds, biochemical parameters, histology, different stages of carcinogenesis and metastasis in various animal models of RCC as well as their translational relevance are summarized. Moreover, we shed some light on imaging methods, which can help define tumor microstructure, assist in the analysis of its metabolic changes and track metastasis development.

MicroRNA-1246 Promotes Melanoma Progression Through Targeting FOXA2

Introduction

Recently, the incidence of melanoma has been rising and there is a lack of effective targeted therapies. The regulatory mechanisms of microRNA-1246 (miR-1246) have been found in many cancers, except melanoma. This study focused on the regulatory mechanism of miR-1246 in melanoma development.

Methods

The expression of miR-1246 was assessed using quantitative real-time polymerase chain reaction (RT-qPCR). Cell viability and metastasis were detected by Transwell and MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assays. The protein expression of epithelial mesenchymal transition (EMT) makers was assessed by Western blot analysis. The target gene of miR-1246 was detected using luciferase reporter assay.

Results

MiR-1246 expression was increased in melanoma tissues and cells. In addition, upregulation of miR-1246 promoted cell viability and metastasis in melanoma. Forkhead box protein A2 (FOXA2) was confirmed to be a direct target of miR-1246. And FOXA2 expression was decreased in melanoma and was suppressed by miR-1246. Importantly, upregulation of FOXA2 restored the carcinogenesis of miR-1246 in melanoma.

Conclusion

MiR-1246 promoted cell viability and metastasis in melanoma by inhibiting FOXA2 expression.

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.

Targeting CDC7 sensitizes resistance melanoma cells to BRAFV600E-specific inhibitor by blocking the CDC7/MCM2-7 pathway

Although the utilization of selective BRAF^V600E inhibitors is associated with improved overall survival in patients with metastatic melanoma, a growing challenge of drug resistance has  emerged. CDC7 has been shown to be overexpressed and associated with poor prognosis in various cancers including melanoma. Thus, we aimed to elucidate the biological role of CDC7 in promoting Vemurafenib resistance and the anticipated benefits of dual targeting of BRAF^V600E and CDC7 in melanoma cells. We performed exosomes-associated microRNA profiling and functional assays to determine the role of CDC7 in drug resistance using Vemurafenib-sensitive and resistant melanoma cells. Our results demonstrated that Vemurafenib-resistant cells exhibited a persistent expression of CDC7 in addition to prolonged activity of MCM2 compared to drug-sensitive cells. Reconstitution of miR-3613-3p in resistant cells downregulated CDC7 expression and reduced the number of colonies. Treatment of cells with low concentrations of CDC7 inhibitor TAK-931 sensitized resistant cells to Vemurafenib and reduced the number of cell colonies. Taken together, CDC7 overexpression and downregulation of miR-3613-3p were associated with Vemurafenib resistance in BRAF^V600E- bearing melanoma cells. Dual targeting of CDC7 and BRAF^V600E reduced the development of resistance against Vemurafenib. Further studies are warranted to investigate the clinical effect of targeting CDC7 in metastatic melanoma.

The Role of Autophagy in the Resistance to BRAF Inhibition in BRAF-Mutated Melanoma

Malignant melanoma is the most aggressive and notorious skin cancer, and metastatic disease is associated with very poor long-term survival outcomes. Although metastatic melanoma patients with oncogenic mutations in the BRAF gene initially respond well to the treatment with specific BRAF inhibitors, most of them will eventually develop resistance to this targeted therapy. As a highly conserved catabolic process, autophagy is responsible for the maintenance of cellular homeostasis and cell survival, and is involved in multiple diseases, including cancer. Recent study results have indicated that autophagy might play a decisive role in the resistance to BRAF inhibitors in BRAF-mutated melanomas. In this review, we will discuss how autophagy is up-regulated by BRAF inhibitors, and how autophagy induces the resistance to these agents.

Upregulation of S100A9 contributes to the acquired resistance to BRAF inhibitors

BACKGROUNDS

Acquired resistance is a significant clinical challenge in targeted therapy of melanomas using BRAF inhibitors. We previously identified that downregulation of miR-92a-1-5p confers acquired resistance to BRAF inhibition using an miRNA array platform.

OBJECTIVE

In this study, we investigated the target genes of miR-92a-1-5p and their functional significance in BRAF inhibitor resistance.

METHODS

The miRNA target prediction data were combined with RNA-Seq data to identify possible target genes for miR-92a-1-5p. Cellular effects of target genes were further examined using siRNA knockdown, WST-1 assay, and immunoblotting analysis.

RESULTS

We selected S100 calcium-binding protein A9 (S100A9) as a possible target gene for functional validation. S100A9 knockdown abrogated resistance to PLX4720 in A375P/Mdr cells. This result was similar to those described earlier for miR-92a-1-5p, indicating that miR-92a-1-5p inhibits cell viability by targeting S100A9. S100A9 overexpression partially conferred PLX4720 resistance to A375P cells. We also demonstrated that MAPK re-activation does not contribute to the promotion of BRAF inhibitor resistance by S100A9.

CONCLUSION

Taken together, our results indicate that S100A9 might be functionally involved in development of resistance to BRAF inhibitors and might be a target for melanoma therapy in the future.

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.

The "-OMICS" facet of melanoma: Heterogeneity of genomic, proteomic and metabolomic biomarkers

In the recent decade, cutting edge molecular and proteomic analysis platforms revolutionized biomarkers discovery in cancers. Melanoma is the prototype with over 51,100 biomarkers discovered and investigated thus far. These biomarkers include tissue based tumor cell and tumor microenvironment biomarkers and circulating biomarkers including tumor DNA (cf-DNA), mir-RNA, proteins and metabolites. These biomarkers provide invaluable information for diagnosis, prognosis and play an important role in prediction of treatment response. In this review, we summarize the most recent discoveries in each of these biomarker categories. We will discuss the challenges in their implementation and standardization and conclude with some perspectives in melanoma biomarker research.

miR-126-3p down-regulation contributes to dabrafenib acquired resistance in melanoma by up-regulating ADAM9 and VEGF-A

Background

Development of resistance to inhibitors of BRAF (BRAFi) and MEK (MEKi) remains a great challenge for targeted therapy in patients with BRAF-mutant melanoma. Here, we explored the role of miRNAs in melanoma acquired resistance to BRAFi.

Methods

miRNA expression in two BRAF-mutant melanoma cell lines and their dabrafenib-resistant sublines was determined using Affymetrix GeneChip® miRNA 3.1 microarrays and/or qRT-PCR. The effects of miR-126-3p re-expression on proliferation, apoptosis, cell cycle, ERK1/2 and AKT phosphorylation, dabrafenib sensitivity, invasiveness and VEGF-A secretion were evaluated in the dabrafenib-resistant sublines using MTT assays, flow cytometry, immunoblotting, invasion assays in Boyden chambers and ELISA. ADAM9, PIK3R2, MMP7 and CXCR4 expression in the sensitive and dabrafenib-resistant cells was determined by immunoblotting. Small RNA interference was performed to investigate the consequence of VEGFA or ADAM9 silencing on proliferation, invasiveness or dabrafenib sensitivity of the resistant sublines. Long-term proliferation assays were carried out in dabrafenib-sensitive cells to assess the effects of enforced miR-126-3p expression or ADAM9 silencing on resistance development. VEGF-A serum levels in melanoma patients treated with BRAFi or BRAFi+MEKi were evaluated at baseline (T0), after two months of treatment (T2) and at progression (TP) by ELISA.

Results

miR-126-3p was significantly down-regulated in the dabrafenib-resistant sublines as compared with their parental counterparts. miR-126-3p replacement in the drug-resistant cells inhibited proliferation, cell cycle progression, phosphorylation of ERK1/2 and/or AKT, invasiveness, VEGF-A and ADAM9 expression, and increased dabrafenib sensitivity. VEGFA or ADAM9 silencing impaired proliferation and invasiveness of the drug-resistant sublines. ADAM9 knock-down in the resistant cells increased dabrafenib sensitivity, whereas miR-126-3p enforced expression or ADAM9 silencing in the drug-sensitive cells delayed the development of resistance. At T0 and T2, statistically significant differences were observed in VEGF-A serum levels between patients who responded to therapy and patients who did not. In responder patients, a significant increase of VEGF-A levels was observed at TP versus T2.

Conclusions

Strategies restoring miR-126-3p expression or targeting VEGF-A or ADAM9 could restrain growth and metastasis of dabrafenib-resistant melanomas and increase their drug sensitivity. Circulating VEGF-A is a promising biomarker for predicting patients’ response to BRAFi or BRAFi+MEKi and for monitoring the onset of resistance.

Electronic supplementary material

The online version of this article (10.1186/s13046-019-1238-4) contains supplementary material, which is available to authorized users.

MicroRNA heterogeneity in melanoma progression

The altered expression of miRNAs has been linked with neocarcinogenesis or the development of human malignancies including melanoma. Of significance, multiple clinical studies have documented that distinct sets of microRNAs (miRNAs) could be utilized as prognostic biomarkers for cancer development or predict the outcomes of treatment responses. To that end, an in-depth validation of such differentially expressed miRNAs is necessary in diverse settings of cancer patients in order to devise novel approaches to control tumor growth and/or enhance the efficacy of clinically-relevant therapeutic options. Moreover, considering the heterogeneity and sophisticated regulation of miRNAs, the precise delineation of their cellular targets could also be explored to design personalized medicine. Given the significance of miRNAs in regulating several key cellular processes of tumor cells including cell cycle progression and apoptosis, we review the findings of such miRNAs implicated in melanoma tumorigenesis. Understanding the novel mechanistic insights of such miRNAs will be useful for developing diagnostic or prognostic biomarkers or devising future therapeutic intervention for malignant melanoma.

Differential Gene Expression Common to Acquired and Intrinsic Resistance to BRAF Inhibitor Revealed by RNA-Seq Analysis

Melanoma cells have been shown to respond to BRAF inhibitors; however, intrinsic and acquired resistance limits their clinical application. In this study, we performed RNA-Seq analysis with BRAF inhibitor-sensitive (A375P) and -resistant (A375P/Mdr with acquired resistance and SK-MEL-2 with intrinsic resistance) melanoma cell lines, to reveal the genes and pathways potentially involved in intrinsic and acquired resistance to BRAF inhibitors. A total of 546 differentially expressed genes (DEGs), including 239 up-regulated and 307 down-regulated genes, were identified in both intrinsic and acquired resistant cells. Gene ontology (GO) analysis revealed that the top 10 biological processes associated with these genes included angiogenesis, immune response, cell adhesion, antigen processing and presentation, extracellular matrix organization, osteoblast differentiation, collagen catabolic process, viral entry into host cell, cell migration, and positive regulation of protein kinase B signaling. In addition, using the PANTHER GO classification system, we showed that the highest enriched GOs targeted by the 546 DEGs were responses to cellular processes (ontology: biological process), binding (ontology: molecular function), and cell subcellular localization (ontology: cellular component). Ingenuity pathway analysis (IPA) network analysis showed a network that was common to two BRAF inhibitor-resistant cells. Taken together, the present study may provide a useful platform to further reveal biological processes associated with BRAF inhibitor resistance, and present areas for therapeutic tool development to overcome BRAF inhibitor resistance.

The origin of exosomal miR-1246 in human cancer cells

miR-1246 is considered an oncomiR in various cancer types. However, the origin and biogenesis of miR-1246 remain controversial which often leads to misinterpretation of its detection and biological function, and inevitably masking its mechanisms of action. Using next generation small RNA sequencing, CRISPR-Cas9 knockout, siRNA knockdown and the poly-A tailing SYBR qRT-PCR, we examined the biogenesis of exosomal miR-1246 in human cancer cell model systems. We found that miR-1246 is highly enriched in exosomes derived from human cancer cells and that it originates from RNU2-1, a small nuclear RNA and essential component of the U2 complex of the spliceosome. Knockdown of Drosha and Dicer did not reduce exosomal miR-1246 levels, indicating that exosomal miR-1246 is generated in a Drosha- and Dicer-independent manner. Direct digestion of cellular lysate by RNase A and knockdown of the RNU2-1 binding protein SmB/B' demonstrated that exosomal miR-1246 is a RNU2-1 degradation product. Furthermore, the GCAG motif present in the RUN2-1 transcript was shown to mediate miR-1246 enrichment in cancer exosomes. We conclude that exosome miR-1246 is derived from RNU2-1 degradation through a non-canonical microRNA biogenesis process. These findings reveal the origin of an oncomiR in human cancer cells, providing guidance in understanding miR-1246 detection and biological function. Abbreviations: CRISPR, Clustered Regularly Interspaced Short Palindromic Repeats; miRNA, microRNA; PDAC, pancreatic ductal adenocarcinoma; RNU2-1, U2 small nuclear RNA; RT-PCR, Reverse transcription polymerase chain reaction; sgRNA, single-guide RNA.

A three plasma microRNA signature for papillary thyroid carcinoma diagnosis in Chinese patients

Whether plasma miRNAs could be used as novel non-invasive biomarkers in diagnosing papillary thyroid carcinoma (PTC) remains unknown. In this study, we designed a four-phase study to identify differentially expressed plasma miRNAs in Chinese PTC patients. Exiqon panel was initially utilized to conduct plasma miRNA profile (3 PTC pools VS. 1 healthy control (HC) pool; each 10 samples were pooled as 1 sample). The dysregulated miRNAs were then analyzed in the training (30 PTC VS. 30 HCs), testing (57 PTC VS. 54 HCs) and external validation phases (33 PTC VS. 30HCs). The identified miRNAs were further affirmed in benign nodules (2 nodular goiter (NG) pool VS. 1 HC pool). We also verified the expression of identified miRNAs in 17 matched malignant and normal tissue samples, NG plasma samples (29 PTC VS. 29 NG) and plasma exosomes (25 PTC VS. 25 HCs). Receiver operating characteristic (ROC) curves were constructed to evaluate the diagnostic value of the identified miRNAs. As a result, the screening phase demonstrated 30 dysregulated plasma miRNAs in PTC patients compared with HCs. After multiphase experiment processes, miR-346, miR-10a-5p and miR-34a-5p were found significantly elevated in PTC plasma samples relative to HCs. The areas under the ROC curve (AUC) of the three-miRNA panel for the training, testing and validation phases were 0.926, 0.811 and 0.816, separately. The panel could also differentiate PTC from NG with the AUC of 0.877. MiR-346 and miR-34a-5p but not miR-10a-5p were up-regulated in PTC tissues. And the three miRNAs showed consistently up-regulation in PTC plasma exosomes. In conclusion, our study established a three-miRNA panel in plasma with considerable clinical value in discriminating PTC from HC or NG.

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.

Targeting signal-transducer-and-activator-of-transcription 3 sensitizes human cutaneous melanoma cells to BRAF inhibitor

Melanoma treatment with the BRAF V600E inhibitor vemurafenib provides therapeutic benefits but the common emergence of drug resistance remains a challenge. To define molecular mechanisms of vemurafenib resistance, we generated A375-R, WM35-R cell lines resistant to vemurafenib and show that the phosphorylated (p)-STAT3 was upregulated in these cells in vitro and in vivo. In particular, activation of the Signal-transducer-and-activator-of-transcription 3 (STAT3) pathway was associated with vemurafenib resistance. Inhibition of this pathway with STAT3-specific siRNA (shRNA) sensitized A375-R, WM35-R cells to vemurafenib and induced apoptosis in vitro and in vivo. Moreover, targeting STAT3 induced expression of miR-579-3p and elicited resistance to vemurafenib. However, targeting microRNA (miR)-579-3p with anti-miR-579-3p reversed the resistance to vemurafenib. Together, these results indicated that STAT3-mediated downexpression of miR-579-3p caused resistance to vemurafenib. Our findings suggest novel approaches to overcome resistance to vemurafenib by combining vemurafenib with STAT3 sliencing or miR-579-3p overexpression.

Exosome-packaged miR-1246 contributes to bystander DNA damage by targeting LIG4

Background

An increasing number of studies have recently reported that microRNAs packaged in exosomes contribute to multiple biological processes such as cancer progression; however, little is known about their role in the development of radiation-induced bystander effects.

Methods

The exosomes were isolated from the culture medium of BEP2D cells with or without γ-ray irradiation by ultracentrifugation. To monitor DNA damage and repair efficiency, the DNA double-strand break biomarker 53BP1 foci, comet, micronuclei, expression of DNA repair genes and NHEJ repair activity were detected. The miR-1246 targeting sequence of the DNA ligase 4 (LIG4) mRNA 3′UTR was assessed by luciferase reporter vectors.

Results

miR-1246 was increased in exosomes secreted from 2 Gy-irradiated BEP2D cells and inhibited the proliferation of nonirradiated cells. The miR-1246 mimic, exosomes from irradiated cells, and radiation-conditioned cell culture medium increased the yields of 53BP1 foci, comet tail and micronuclei in nonirradiated cells, and decreased NHEJ efficiency. miR-1246 downregulated LIG4 expression by directly targeting its 3′UTR.

Conclusions

Our findings demonstrate that miR-1246 packaged in exosomes could act as a transfer messenger and contribute to DNA damage by directly repressing the LIG4 gene. Exosomal miR-1246 may be a critical predictor of and player in radiation-induced bystander DNA damage.

Chemotherapy Resistance Mechanisms in Advanced Skin Cancer

Melanoma is a most dangerous and deadly type of skin cancer, and considered intrinsically resistant to both radiotherapy and chemotherapy. It has become a major public health concern as the incidence of melanoma has been rising steadily over recent decades with a 5-year survival remaining less than 5%. Detection of the disease in early stage may be curable, but late stage metastatic disease that has spread to other organs has an extremely poor prognosis with a median survival of less than 10 months. Since metastatic melanoma is unresponsive to therapy that is currently available, research is now focused on different treatment strategies such as combinations of surgery, chemotherapy and radiotherapy. The molecular basis of resistance to chemotherapy seen in melanoma is multifactorial; defective drug transport system, altered apoptotic pathway, deregulation of apoptosis and/or changes in enzymatic systems that mediate cellular metabolic machinery. Understanding of alterations in molecular processes involved in drug resistance may help in developing new therapeutic approaches to treatment of malignant melanoma.