Melanoma Cell Migration Research Articles

EphA3 targeted by miR-3666 contributes to melanoma malignancy via activating ERK1/2 and p38 MAPK pathways.

Melanoma is a rare, fatal type of skin tumor. Although EPH receptor A3 (EphA3) is deregulated in melanoma, its detailed role remained uncharacterized. Using real time quantitative PCR analysis and western blotting, EphA3 was identified to be upregulated in melanoma tissues and cells, while miR-3666 showed an opposite expression trend. Cell counting kit-8, scratch wound, and in vivo assays proved that EphA3 silence inhibited the melanoma cell proliferation and migration and retarded tumor growth in vivo. Furthermore, western blotting results displayed that EphA3 silence resulted in a low expression of p38-MAPK and p-ERK1/2. Mechanically, miR-3666 was proved to target EphA3 3'UTR by the luciferase reporter assay. Furthermore, miR-3666 mimic compromised the driven melanoma cell proliferation and migration by EphA3 overexpression. In addition, induction of ERK1/2 and p38 MAPK pathways offset the positive effect of EphA3 overexpression on melanoma cells. In conclusion, miR-3666 downregulated EphA3 expression and retarded melanoma malignancy via inactivating ERK1/2 and p38 MAPK pathways. Hence, miR-3666/EphA3 axis may represent a druggable target against melanoma progression.

Insights into Melanoma Fibroblast Populations and Therapeutic Strategy Perspectives: Friends or Foes?

Cutaneous melanoma (CM) is an aggressive and highly metastatic solid tumor associated with drug resistance. Before 2011, despite therapies based on cytokines or molecules inhibiting DNA synthesis, metastatic melanoma led to patient death within 18 months from diagnosis. However, recent studies on bidirectional interactions between melanoma cells and tumor microenvironment (TME) have had a significant impact on the development of new therapeutic strategies represented by targeted therapy and immunotherapy. In particular, the heterogeneous stromal fibroblast populations, including fibroblasts, fibroblast aggregates, myofibroblasts, and melanoma associated fibroblasts (MAFs), represent the most abundant cell population of TME and regulate cancer growth differently. Therefore, in this perspective article, we have highlighted the different impacts of fibroblast populations on cancer development and growth. In particular, we focused on the role of MAFs in sustaining melanoma cell survival, proliferation, migration and invasion, drug resistance, and immunoregulation. The important role of constitutively activated MAFs in promoting CM growth and immunoediting makes this cell type a promising target for cancer therapy.

Interleukin-1β triggers matrix metalloprotease-3 expression through p65/RelA activation in melanoma cells.

Melanoma shows highly aggressive behavior (i.e., local invasion and metastasis). Matrix metalloprotease-3 (MMP-3), a zinc-dependent endopeptidase, degrades several extracellular substrates and contributes to local invasion by creating a microenvironment suitable for tumor development. Here, we report that interleukin-1β (IL-1β) triggers the MMP-3 expression in canine melanoma cells. The activity of MMP-3 in the culture supernatant was increased in IL-1β-treated melanoma cells. IL-1β time- and dose-dependently provoked the mRNA expression of MMP-3. IL-1β induced the migration of melanoma cells; however, this migration was attenuated by UK356618, an MMP-3 inhibitor. When the cells were treated with the nuclear factor-κB (NF-κB) inhibitor TPCA-1, the inhibition of MMP-3 expression was observed. In IL-1β-treated cells, the phosphorylation both of p65/RelA and p105 was detected, indicating NF-κB pathway activation. In p65/RelA-depleted melanoma cells, IL-1β-mediated mRNA expression of MMP-3 was inhibited, whereas this reduction was not observed in p105-depleted cells. These findings suggest that MMP-3 expression in melanoma cells is regulated through IL-1β-mediated p65/RelA activation, which is involved in melanoma cell migration.

Dioscin induces M1 macrophage polarization through Connexin-43 Channels in Tumor-associated-macrophages-mediated melanoma metastasis

BackgroundTumor-associated macrophages (TAMs) are important constituent parts of tumor microenvironment that connected with tumor metastasis in melanoma. Connexin 43 (Cx43) was expressed in all the immune cells which modulated different aspects of immune response. However, the concrete molecular mechanism maintains unclear. PurposeThe study aimed to find a natural drug monomer effectively reversed the polarity of tumor-associated macrophages inhibiting melanoma metastasis and improving survival time. MethodsFlow cytometry was used to determine the effects of dioscin on the macrophage phenotype. Western bolt and ELISA were performed to explore the underlying mechanism of dioscin and a co-culture experiment in vitro was applied to assess the role of dioscin on TAMs-mediated melanoma proliferation, invasion and migration. Moreover, in vivo melanoma metastasis models were established for examining effects of dioscin on TAMs-mediated melanoma metastasis. ResultsDioscin repolarized macrophages from M2 towards M1-like phenotype. Dioscin suppressed M2-like phenotype macrophages through enhanced the expression and transport function of Cx43. Furthermore, the stimulation IFN-γ/STAT1 pathway and suppression IL-4/JAK2/STAT3 pathway were major mechanism of dioscin. Importantly, dioscin suppressed Cx43G21R mutation TAMs induced proliferation, invasion, migration and metastasis of melanoma cells. It worthily noting that dioscin ameliorated tumor-associated-macrophages-mediated melanoma metastasis in vitro and vivo. ConclusionDioscin re-polarized macrophages from M2 to M1 phenotype through activation of Cx43-gap-junction-intercellular-communications (Cx43-GJs)/IFN-γ/STAT1 pathway and inhibition of Cx43-GJs/IL-4/JAK2/STAT3 suppressing migration, invasion and metastasis of melanoma, which provided a theoretical and experimental basis for treating melanoma metastasis.

The Inhibitory Effects and Cytotoxic Activities of the Stem Extract of Sarracenia purpurea against Melanoma Cells and the SsbA Protein.

The Staphylococcus aureus SsbA protein (SaSsbA) is a single-stranded DNA-binding protein (SSB) that is categorically required for DNA replication and cell survival, and it is thus an attractive target for potential antipathogen chemotherapy. In this study, we prepared the stem extract of Sarracenia purpurea obtained from 100% acetone to investigate its inhibitory effect against SaSsbA. In addition, the cytotoxic effects of this extract on the survival, apoptosis, proliferation, and migration of B16F10 melanoma cells were also examined. Initially, myricetin, quercetin, kaempferol, dihydroquercetin, dihydrokaempferol, rutin, catechin, β-amyrin, oridonin, thioflavin T, primuline, and thioflavin S were used as possible inhibitors against SaSsbA. Of these compounds, dihydrokaempferol and oridonin were capable of inhibiting the ssDNA-binding activity of SaSsbA with respective IC50 values of 750 ± 62 and 2607 ± 242 μM. Given the poor inhibition abilities of dihydrokaempferol and oridonin, we screened the extracts of S. purpurea, Nepenthes miranda, and Plinia cauliflora for SaSsbA inhibitors. The stem extract of S. purpurea exhibited high anti-SaSsbA activity, with an IC50 value of 4.0 ± 0.3 μg/mL. The most abundant compounds in the stem extract of S. purpurea were identified using gas chromatography-mass spectrometry. The top five most abundant contents in this extract were driman-8,11-diol, deoxysericealactone, stigmast-5-en-3-ol, apocynin, and α-amyrin. Using the MOE-Dock tool, the binding modes of these compounds, as well as dihydrokaempferol and oridonin, to SaSsbA were elucidated, and their binding energies were also calculated. Based on the S scores, the binding capacity of these compounds was in the following order: deoxysericealactone > dihydrokaempferol > apocynin > driman-8,11-diol > stigmast-5-en-3-ol > oridonin > α-amyrin. Incubation of B16F10 cells with the stem extract of S. purpurea at a concentration of 100 μg/mL caused deaths at the rate of 76%, reduced migration by 95%, suppressed proliferation and colony formation by 99%, and induced apoptosis, which was observed in 96% of the B16F10 cells. Overall, the collective data in this study indicate the pharmacological potential of the stem extract of S. purpurea for further medical applications.

Interference in melanoma CD248 function reduces vascular mimicry and metastasis

BackgroundTumor vascular mimicry is an emerging issue that affects patient survival while having no treatment at the current moment. Despite several factors implicated in vascular mimicry, little is known about stromal factors that modulate tumor microenvironment and shape malignant transformation. CD248, a type-I transmembrane protein dominantly expressed in stromal cells, mediates the interaction between cells and extracellular matrix proteins. CD248 protein expression is associated with the metastatic melanoma phenotype and promotes tumor progression in the stromal cells. This study aimed to explore the cell-autonomous effects of CD248 in melanoma vascular mimicry to aid cancer therapy development.MethodsLoss-of-function approaches in B16F10 melanoma cells were used to study the cell-autonomous effects of CD248 on cell adhesion, migration, proliferation, and vascular mimicry. A solid-phase binding assay was performed to identify the interaction between CD248 and fibronectin. Horizontal and vertical cell migration assays were performed to analyze cell migration activity, and cell-patterned network formation on Matrigel was used to evaluate vascular mimicry activity. Recombinant CD248 (rCD248) proteins were generated, and whether rCD248 interfered with melanoma CD248 functions was evaluated in vitro. An experimental lung metastasis mouse model was used to investigate the effect of rCD248 treatment in vivo.ResultsCD248 protein expression in melanoma cells was increased by a fibroblast-conditioned medium. Knockdown of CD248 expression significantly decreased cell adhesion to fibronectin, cell migration, and vascular mimicry in melanoma cells. The lectin domain of CD248 was directly involved in the interaction between CD248 and fibronectin. Furthermore, rCD248 proteins containing its lectin domain inhibited cell adhesion to fibronectin and slowed down cell migration and vascular mimicry. Treatment with rCD248 protein could reduce pulmonary tumor burden, accompanied by a reduction in vascular mimicry in mice with melanoma lung metastasis.ConclusionCD248 expression in melanoma cells promotes malignant transformation by increasing the activity of cell adhesion, migration, and vascular mimicry, whereas rCD248 protein functions as a molecular decoy interfering with tumor-promoting effects of CD248 in melanoma cells.

KCNQ1OT1 sponges miR-34a to promote malignant progression of malignant melanoma via upregulation of the STAT3/PD-L1 axis.

Malignant melanoma is a leading cause of skin cancer-related death. In over 30% of cases, the melanoma is invasive and has a metastatic phenotype. KCNQ1 overlapping transcript 1 (KCNQ1OT1) was previously identified as an oncogenic long noncoding RNA (lncRNA). Our study intends to uncover the mechanism of KCNQ1OT1 functioning in melanoma. qRT-PCR, immunohistochemical analysis, and Western blotting were used to investigate mechanisms of the lncRNA KCNQ1OT1, on its downstream genes in melanoma tissues, cells as well as the impact on CD8+ T cells. Proliferation, apoptosis, and migration/invasion were assessed in melanoma cells to evaluate the effects of KCNQ1OT1, miR-34a, and signal transducer and activator of transcription 3 (STAT3). The RNA interactions were determined by dual-luciferase reporter, and melanoma cells were co-cultured with CD8+ T cells to study immune evasion. A lactate dehydrogenase (LDH) cytotoxicity assay was used to investigate the cytotoxicity of CD8+ T cells toward melanoma cells. The in vivo tumorigenic potential of KCNQ1OT1 was defined using xenograft models. KCNQ1OT1 was upregulated in melanoma tissues leading to a poor prognosis, and knocking down it inhibited melanoma cell proliferation, migration, and invasion. KCNQ1OT1 regulated the progression of the melanoma via its action as a miR-34a sponge. STAT3 was found to be a downstream target of miR-34a, resulting in transcriptional regulation of Programmed cell death 1 ligand 1 (PD-L1). KCNQ1OT1 regulated STAT3 by targeting miR-34a. Knockdown of KCNQ1OT1 reduced PD-L1 level, enhanced CD8+ T cell cytotoxicity, and proliferation and inhibited apoptosis of CD8+ T cells. Melanoma cells overexpressed KCNQ1OT1, which influenced the miR-34a/STAT3 axis, to promote proliferation, migration, and invasion of melanoma cells. In addition, KCNQ1OT1 inhibited CD8+ T cell function, also via the miR-34a/STAT3/PD-L1 axis, thus promoting immune evasion of melanoma cells. The current findings expose a potential therapeutic target of melanoma.

Afrormosin exerts an anticancer effect via MAPK and AKT signaling pathways in B16F10 cells

Melanoma is a deadly skin cancer with high mortality, and its incidence is increasing every year. Although numerous anticancer drugs have been developed, these treatments have various side effects, such as skin rash, fatigue, diarrhea, cough, and muscle pain. Therefore, there is a need for research on novel anticancer drugs with low cytotoxicity and few side effects. In this study, we investigated whether afrormosin (7-hydroxy-4′,6-dimethoxyisoflavone), a member of the isoflavonoid family, could have the potential as a novel anticancer drug. Afrormosin decreased the viability of B16F10 melanoma cells in a time- and dose-dependent manner. We also found that the afrormosin-induced decrease in cell viability was caused by the reduction of cell proliferation through Go/G1 arrest and the induction of apoptosis in B16F10 melanoma cells. Furthermore, afrormosin decreased the metastatic activity (cell invasion and migration) of B16F10 melanoma cells. At the molecular level, afrormosin reduced the levels of Bcl-2, an anti-apoptotic protein, and augmented the levels of Bax, a pro-apoptotic protein, and p53, a tumor suppressor. Additionally, procaspase-3 levels were reduced by afrormosin treatment. When we examined the signaling pathways affected by afrormosin, we found that the AKT/ERK pathways were inhibited and the p38/JNK pathway was activated by afrormosin. Collectively, these results suggest the potential anticancer effect of afrormosin, making it a prospective candidate for development as an anticancer drug.

YTHDF3 promotes melanoma metastasis by reading N6‐methyladenosine

YTHDF3 promotes melanoma metastasis by reading N⁶‐methyladenosine

Centrosomal protein55 enhances melanoma cell proliferation, invasion and migration through PI3K/AKT signaling

Purpose: To investigate the role of centrosomal protein55 (CEP55) in melanoma. 
 Methods: The CEP55 expression in human melanoma cells and normal human melanocytes were determined by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blot. Cell proliferation was evaluated by colony formation and CCK8 assays, while cell cycle was assessed by flow cytometry. Transwell assay was used to investigate cell migration and invasion. 
 Results: The CEP55 protein expression was higher in A-2058 and A375 melanoma cells than in normal HEMn-LP cells. Overexpression of CEP55 increased melanoma cell viability and the number of melanoma cell colonies (p < 0.01), while CEP55 silencing reduced melanoma cell viability and proliferation. Overexpression of CEP55 promoted cell cycle (p < 0.01) via decreased p21 expression, but increased CyclinD1 and CDK1 expression. Knockdown of CEP55 enhanced p21 expression and reduced CyclinD1 and CDK1 expression to induce cell cycle arrest. Knockdown of CEP55 suppressed melanoma cell migration and invasion by downregulating p-AKT and p-PI3K. 
 Conclusion: Centrosomal protein55 functions as an oncogene in melanoma by activating PI3K/AKT signaling. Therefore, CEP55 might be a promising target for melanoma diagnosis and treatment.

Transcriptome-based network analysis related to M2-like tumor-associated macrophage infiltration identified VARS1 as a potential target for improving melanoma immunotherapy efficacy

RationaleThe M2-like tumor-associated macrophages (TAMs) are independent prognostic factors in melanoma.MethodsWe performed weighted gene co-expression network analysis (WGCNA) to identify the module most correlated with M2-like TAMs. The Cancer Genome Atlas (TCGA) patients were classified into two clusters that differed based on prognosis and biological function, with consensus clustering. A prognostic model was established based on the differentially expressed genes (DEGs) of the two clusters. We investigated the difference in immune cell infiltration and immune response-related gene expression between the high and low risk score groups.ResultsThe risk score was defined as an independent prognostic value in melanoma. VARS1 was a hub gene in the M2-like macrophage-associated WGCNA module that the DepMap portal demonstrated was necessary for melanoma growth. Overexpressing VARS1 in vitro increased melanoma cell migration and invasion, while downregulating VARS1 had the opposite result. VARS1 overexpression promoted M2 macrophage polarization and increased TGF-β1 concentrations in tumor cell supernatant in vitro. VARS1 expression was inversely correlated with immune-related signaling pathways and the expression of several immune checkpoint genes. In addition, the VARS1 expression level helped predict the response to anti-PD-1 immunotherapy. Pan-cancer analysis demonstrated that VARS1 expression negatively correlated with CD8 T cell infiltration and the immune response-related pathways in most cancers.ConclusionWe established an M2-like TAM-related prognostic model for melanoma and explored the role of VARS1 in melanoma progression, M2 macrophage polarization, and the development of immunotherapy resistance.

Netrin-1 Stimulates Migration of Neogenin Expressing Aggressive Melanoma Cells.

Netrin-1 is a neural guidance factor that regulates migration and positioning of neural crest-derived cells during embryonic development. Depending on the type of Netrin-1 receptor expression, cells are either attracted or repulsed by Netrin-1. Postnatal expression of Netrin-1 is detected in brain, colon, liver, and kidney, which are common sites of cancer metastasis, including melanoma. Thus, understanding the dynamics between Netrin-1 and its receptors could explain the attraction of melanoma towards these Netrin-1-expressing tissues. Here, we investigate whether the Netrin-1-attractive receptor Neogenin can affect migration of melanoma cells towards a Netrin-1 source. Results from Western blot (WB) analysis show higher expression of Neogenin in aggressive compared to non-aggressive melanoma cells. Cell migration experiments show increased migration of Neogenin-expressing aggressive melanoma cells towards exogenous, soluble recombinant human Netrin-1 and towards a Netrin-1-expressing cell line. Furthermore, WB reveals ERK1/2 activation and increased N-cadherin expression in Neogenin-expressing aggressive melanoma cells treated with rhNetrin-1. Moreover, treatment with anti-Neogenin blocking antibody caused decreased migration towards Netrin-1-expressing cells and reduced ERK1/2 activity in Neogenin-expressing aggressive melanoma cells. These results suggest Neogenin may play a role during migration of melanoma cells towards Netrin-1 via ERK1/2 signaling.

METTL14 promotes migration and invasion of choroidal melanoma by targeting RUNX2 mRNA via m6A modification.

The modification of N6-methyladenosine is involved in the progression of various cancers. This study aimed to clarify its regulatory mechanism in the pathogenesis of choroidal melanoma. Expression of methyltransferase-like 14 in choroidal melanoma or normal choroidal tissues was determined by Western blot and immunohistochemistry. The impacts of methyltransferase-like 14 on invasion and migration of choroidal melanoma cells were determined using functional and animal experiments. The interaction between methyltransferase-like 14 and its downstream target was identified by methylated RNA immunoprecipitation and a dual-luciferase reporter assay. Additionally, Wnt/β-catenin signalling pathway was evaluated by Western blot. Methyltransferase-like 14 was upregulated in choroidal melanoma compared to the normal choroidal tissues. Overexpression or knockdown of methyltransferase-like 14 enhanced or inhibited the invasion and migration of choroidal melanoma cells, respectively, both in vivo and in vitro. Methyltransferase-like 14 directly targeted downstream runt-related transcription factor 2 mRNA, depending on N6-methyladenosine. Additionally, the Wnt/β-catenin signalling pathway was activated by methyltransferase-like 14 in choroidal melanoma cells. Our study identified a novel RNA regulatory mechanism in which runt-related transcription factor 2 was upregulated by enhanced expression of methyltransferase-like 14 via N6-methyladenosine modification, thus facilitating migration and invasion of choroidal melanoma cells.

MiR-214-Enriched Extracellular Vesicles Released by Acid-Adapted Melanoma Cells Promote Inflammatory Macrophage-Dependent Tumor Trans-Endothelial Migration.

Simple SummaryCutaneous melanoma is the most aggressive form of skin cancer with high-metastatic ability. Despite the recent advancements in melanoma treatments, the prognosis of metastatic patients remains very poor. A better understanding of the molecular mechanisms leading to melanoma dissemination is urgently needed in order to develop novel therapeutical strategies to ameliorate patients’ outcomes. Extracellular vesicles (EV) released by tumor cells are key players in metastasis development: by conveying bioactive molecules with oncogenic activity, they can modulate the surrounding—and even the distant—microenvironment and reprogram recipient cells to facilitate the metastatic cascade. Here, we show that melanoma cells release a higher amount of miR-214-enriched EV when adapted to extracellular acidosis, which promote a macrophage activation state, capable of facilitating the trans-endothelial migration of melanoma cells. Thus, we disclose a new molecular mechanism to prevent melanoma intravasation based on miR-214 targeting.The understanding of the molecular mechanisms leading to melanoma dissemination is urgently needed in view of the identification of new targets and the development of innovative strategies to improve patients’ outcomes. Within the complexity of tumor intercellular communications leading to metastatic dissemination, extracellular vesicles (EV) released by tumor cells are central players. Indeed, the ability to travel through the circulatory system conveying oncogenic bioactive molecules even at distant sites makes EV capable of modulating recipient cells to facilitate metastatic dissemination. The dynamic remodeling of the tumor microenvironment might influence, along with a number of other events, tumoral EV release. We observed that, in melanoma, extracellular acidosis increases the release of EV enriched in miR-214, an onco-miRNA involved in melanoma metastasis. Then, miR-214-enriched EV were found to induce a state of macrophage activation, leading to an overproduction of proinflammatory cytokines and nitric oxide. Such an inflammatory microenvironment was able to alter the endothelial cell permeability, thereby facilitating the trans-endothelial migration of melanoma cells, a crucial step in the metastatic cascade. The use of synthetic miR-214 inhibitors and miR-214 overexpression allowed us to demonstrate the key role of miR-214 in the EV-dependent induction of macrophage activation. Overall, our in vitro study reveals that the release of tumor miR-214-enriched EV, potentiated by adapting tumor cells to extracellular acidosis, drives a macrophage-dependent trans-endothelial migration of melanoma cells. This finding points to miR-214 as a potential new therapeutic target to prevent melanoma intravasation.

Loss of NECTIN1 triggers melanoma dissemination upon local IGF1 depletion

Cancer genetics has uncovered many tumor-suppressor and oncogenic pathways, but few alterations have revealed mechanisms involved in tumor spreading. Here, we examined the role of the third most significant chromosomal deletion in human melanoma that inactivates the adherens junction gene NECTIN1 in 55% of cases. We found that NECTIN1 loss stimulates melanoma cell migration in vitro and spreading in vivo in both zebrafish and human tumors specifically in response to decreased IGF1 signaling. In human melanoma biopsy specimens, adherens junctions were seen exclusively in areas with low IGF1 levels, but not in NECTIN1-deficient tumors. Our study establishes NECTIN1 as a major determinant of melanoma dissemination and uncovers a genetic control of the response to microenvironmental signals.

TRIP13/FLNA Complex Promotes Tumor Progression and Is Associated with Unfavorable Outcomes in Melanoma.

Cutaneous melanoma is a high-grade malignant tumor originating from skin melanocytes with high risk of recurrence and metastasis. Further study on the mechanism of melanoma development is urgently needed. Here, we performed a bioinformatic analysis to identify critical genes in melanoma using public datasets in the Gene Expression Omnibus database. Among these differentially expressed genes, thyroid hormone receptor interactor 13 (TRIP13) has been reported to exert an important role in the development of various tumors, while its role in melanoma remains unclear. We selected TRIP13 as a candidate gene for further study. TRIP13 expression in clinical specimens was evaluated by immunohistochemistry, and its association with patient prognosis was analyzed by the Kaplan-Meier method and log-rank test. MV3 and A2058 melanoma cells were transfected with lentiviral vector to overexpress or knockdown TRIP13 expression level, and then, its biological function was studied using a series of in vitro and in vivo assays. RNA sequencing, co-immunoprecipitation, and mass spectrometry were used to identify the underlying mechanism of TRIP13. The results of this study exhibited that TRIP13 expression was upregulated in melanoma tissue compared with normal tissues, and high levels of TRIP13 were closely correlated with poor prognoses of melanoma patients. Elevated TRIP13 promoted the invasion and migration of melanoma cells in vitro and enhanced lung metastasis in vivo, without an influence on tumor growth. Importantly, elevated TRIP13 promoted the epithelial-mesenchymal transition (EMT) of melanoma cells, indicating a higher metastatic potential of these cells. Mechanically, TRIP13 physically interacted with filamin A (FLNA) and then activated the PI3K/AKT pathway to transcriptional activation of EMT-related genes. The present study revealed that TRIP13 is a novel prognostic biomarker and potential therapeutic target for melanoma treatment.

RAI14 Promotes Melanoma Progression by Regulating the FBXO32/c-MYC Pathway.

Melanoma originates from the malignant transformation of melanocytes. Compared with other skin cancers, melanoma has a higher fatality rate. The 5-year survival rate of patients with early-stage primary melanoma through surgical resection can reach more than 90%. However, the 5-year survival rate of patients with metastatic melanoma is only 25%. Therefore, accurate assessment of melanoma progression is critical. Previous studies have found that Retinoic Acid Induced 14(RAI14) is critical in tumorigenesis. However, the biological function of RAI14 for the development of melanoma is unclear. In this study, RAI14 is highly expressed in melanoma and correlated with prognosis. The expression of RAI14 can affect the proliferation, migration and invasion of melanoma cells. F-Box Protein 32(FBXO32) is an E3 ubiquitin ligase of c-MYC. We found that RAI14 affects the transcriptional expression of FBXO32 and regulates the stability of c-MYC. These results suggest that RAI14 play an important role in the growth of melanoma and is expected to be a therapeutic target for melanoma.

Bidirectional regulation between tumor cell-intrinsic PD-L1 and TGF-β1 in epithelial-to-mesenchymal transition in melanoma.

Transforming growth factor-β1 (TGF-β1) is the predominant form of TGF-β and induces epithelial-to-mesenchymal transition (EMT) in melanoma. Tumor cell-intrinsic programmed death ligand-1 (PD-L1) plays a crucial role in maintenance of the EMT in melanoma. However, the relationship among tumor cell-intrinsic PD-L1, TGF-β1 and EMT is very complicated. We investigated the bidirectional regulation between cell-intrinsic PD-L1 and TGF-β1 in melanoma, and explored the role of PD-L1 in TGF-β1-induced EMT and tumor progression. We found that TGF-β1 upregulated PD-L1 expression in B16-F0 and B16-F10 melanoma cells. Interestingly, PD-L1 also enhanced the intracellular TGF-β1 mRNA levels and induced the secretion of TGF-β1. Immunohistochemical staining revealed that PD-L1 protein expression was co-localized with α-smooth muscle actin (SMA) protein expression in melanoma, suggesting that PD-L1 was associated with EMT. By using shRNA lentivirus to knockdown PD-L1 (PD-L1-shRNA) in melanoma cell lines, we showed that TGF-β1-induced EMT was significantly inhibited in PD-L1-shRNA melanoma cells, which was characterized by the lower fibronectin (FN1) mRNA and higher E-cadherin (CDH1) mRNA levels (both are EMT markers) than that in control. TGF-β1-induced melanoma cell proliferation and migration were also markedly inhibited in PD-L1-shRNA cells. Consistent with the observation in vitro, PD-L1 knockdown inhibited tumor growth and repressed TGF-β1-induced EMT characterized by reduction of FN1 and increase of CDH1 in mouse model. The present study demonstrated a bidirectional regulation between cell-intrinsic PD-L1 and TGF-β1 in melanoma, which may help in designing promising combinations which include targeting TGF-β1 signaling along with PD-L1.

EIF3B stabilizes PTGS2 expression by counteracting MDM2-mediated ubiquitination to promote the development and progression of malignant melanoma.

Malignant melanoma (MM) is a neoplasm that develops from human melanocytes. It was reported that eukaryotic translation initiation factor 3 subunit B (EIF3B) is associated with multiple types of cancers, but its role in MM has not been reported. In the present study, we found that EIF3B was abundantly expressed in MM and was strongly related to lymphatic metastasis and pathological stage of MM patients. In addition, EIF3B depletion could block the progression of MM in vitro and in vivo. In contrast, EIF3B overexpression increased cell proliferation and migration in melanoma cells. More importantly, we identified that EIF3B's driver role in MM was mediated by PTGS2. In detail, we found that EIF3B stabilized PTGS2 expression by inhibiting PTGS2 ubiquitination, which is mediated by the E3 ligase MDM2. Moreover, like EIF3B, silencing PTGS2 could suppress MM development, and more interestingly, it could reverse the situation caused by overexpression of EIF3B in vitro and in vivo. Furthermore, the proliferation and migration inhibited by silencing of EIF3B were also partially recovered by overexpression of PTGS2. Overall, our findings revealed the potential of EIF3B as a therapeutic target for MM. Identification of EIF3B's function in MM may pave the way for future development of more specific and more effective targeted therapy strategies against MM.

Role of the Hedgehog Pathway and CAXII in Controlling Melanoma Cell Migration and Invasion in Hypoxia.

Simple SummaryMalignant melanoma is the leading cause of death among skin cancer patients due to its tendency to metastasize. Hypoxia, which is a common feature of the tumor microenvironment, as well as different alterations at the molecular level, may affect melanoma aggressiveness. The aims and the objectives of this work were to investigate whether and how the Hedgehog pathway and CAXII may control malignant melanoma cell migration and invasiveness either in normoxic or hypoxic conditions. To this end we evaluated the migratory and invasive capabilities of SK-MEL-28 and A375 cell lines, where the hedgehog pathways and CAXII were inhibited by short interfering RNA. Our results indicate that SMO and GLI1 silencing caused the downregulation of CAXII expression. Furthermore, the Hedgehog pathway and CAXII inhibition, resulted in impaired melanoma cell migration and invasion either under normoxic or hypoxic conditions. The fact that CAXII and the Hedgehog pathway are relevant in melanoma cell invasion may be exploited to discover novel and promising therapeutical targets for melanoma clinical management.Background: Malignant melanoma is the leading cause of death among skin cancer patients due to its tendency to metastasize. Alterations at the molecular level are often evident, which is why melanoma biology has garnered increasing interest. The hedgehog (Hh) pathway, which is essential for embryonic development, is aberrantly re-activated in melanoma and may represent a promising therapeutic target. In addition, carbonic anhydrase XII (CAXII) represents a poor prognostic target for hypoxic tumors, such as melanoma, and is involved in cell migration. Thus, we decided to investigate whether and how the Hh pathway and CAXII may control melanoma cell migration and invasiveness. Methods: The migratory and invasive capabilities of SK-MEL-28 and A375 cell lines, either un-transfected or transiently transfected with Smoothened (SMO), GLI1, or CAXII siRNA, were studied under normoxic or hypoxic conditions. Results: For the first time, we showed that SMO and GLI1 silencing resulted in the downregulation of CAXII expression in both moderately and highly invasive melanoma cells under hypoxia. The Hh pathway as well as CAXII inhibition by siRNA resulted in impaired malignant melanoma migration and invasion. Conclusion: Our results suggest that CAXII and the Hh pathway are relevant in melanoma invasion and may be novel and promising therapeutical targets for melanoma clinical management.