MLK3 promotes melanoma proliferation and invasion and is a target of microRNA-125b

Design, synthesis of new 3H-imidazo[4,5-b]pyridine derivatives and evaluation of their inhibitory properties as mixed lineage kinase 3 inhibitors

Mixed-lineage protein kinase 3 (MLK3) is implicated in several human cancers and neurodegenerative diseases. A series of 3H-imidazo[4,5-b]pyridine derivatives were designed, synthesized and evaluated as novel MLK3 inhibitors. A homology model of MLK3 was developed and all designed compounds were docked to assess their binding pattern and affinity toward the MLK3 active site. Based on this knowledge, we synthesized and experimentally evaluated the designed compounds. Majority of the compounds showed significant inhibition of MLK3 in the enzymatic assay. In particular, compounds 9a, 9e, 9j, 9 k, 12b and 12d exhibited IC50 values of 6, 6, 8, 11, 14 and 14 nM, respectively. Furthermore, compounds 9a, 9e, 9 k and 12b exhibited favorable physicochemical properties among these compounds.

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

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

Phosphorylation of mixed lineage kinase MLK3 by cyclin-dependent kinases CDK1 and CDK2 controls ovarian cancer cell division

Mixed lineage kinase 3 (MLK3) is a serine/threonine mitogen-activated protein kinase kinase kinase that promotes the activation of multiple mitogen-activated protein kinase pathways and is required for invasion and proliferation of ovarian cancer cells. Inhibition of MLK activity causes G2/M arrest in HeLa cells; however, the regulation of MLK3 during ovarian cancer cell cycle progression is not known. Here, we found that MLK3 is phosphorylated in mitosis and that inhibition of cyclin-dependent kinase 1 (CDK1) prevented MLK3 phosphorylation. In addition, we observed that c-Jun N-terminal kinase, a downstream target of MLK3 and a direct target of MKK4 (SEK1), was activated in G2 phase when CDK2 activity is increased and then inactivated at the beginning of mitosis concurrent with the increase in CDK1 and MLK3 phosphorylation. Using in vitro kinase assays and phosphomutants, we determined that CDK1 phosphorylates MLK3 on Ser548 and decreases MLK3 activity during mitosis, whereas CDK2 phosphorylates MLK3 on Ser770 and increases MLK3 activity during G1/S and G2 phases. We also found that MLK3 inhibition causes a reduction in cell proliferation and a cell cycle arrest in ovarian cancer cells, suggesting that MLK3 is required for ovarian cancer cell cycle progression. Taken together, our results suggest that phosphorylation of MLK3 by CDK1 and CDK2 is important for the regulation of MLK3 and c-Jun N-terminal kinase activities during G1/S, G2, and M phases in ovarian cancer cell division.

LncRNA LNCOC1 is Upregulated in Melanoma and Serves as a Potential Regulatory Target of miR-124 to Suppress Cancer Cell Invasion and Migration

Background

A cascade of genes and pathways have been reported in the precise regulation of malignant melanoma (MM). Previous study has demonstrated that lncRNA LNCOC1 is an oncogenic factor in the pathogenesis and development of various cancers. The present study explored the functionalities of LNCOC1 and its interactions with miR-124 in MM.

Methods

A total of 65 melanoma patients were enrolled in this study. The expression of LNCOC1 and miR-124 after cell transfection were detected by RT-qPCR. The migration rates of SK-MEL-3 and A375 cells after transient transfection with LNCOC1 expression vector and miR-124 mimic was detected by trans-well assay.

Results

LNCOC1 was accumulated to high levels in melanoma, and it was significantly correlated with the low survival rate of melanoma patients. Our bioinformatics data showed that miR-124 could target LNCOC1. Overexpression of miR-124 could downregulate LNCOC1. However, up-regulated the expression of LNCOC1 did not affect the expression of miR-124. Our correlation analysis also revealed that the expression of LNCOC1 and miR-124 were inversely correlated in both melanoma tissues and non-tumor tissues. The trans-well invasion and migration assays indicated that overexpression of miR-124 inhibited the melanoma cell invasion and migration. However, overexpression of LNCOC1 promoted melanoma cell invasion and migration.

Conclusion

LNCOC1 is upregulated in melanoma, which can be considered as a potential target of miR-124 in modulating melanoma cell invasion and migration. LNCOC1 may also be an interfering target of MM therapy.

Exosomes Immunity Strategy: A Novel Approach for Ameliorating Intervertebral Disc Degeneration

Low back pain (LBP), which is one of the most severe medical and social problems globally, has affected nearly 80% of the population worldwide, and intervertebral disc degeneration (IDD) is a common musculoskeletal disorder that happens to be the primary trigger of LBP. The pathology of IDD is based on the impaired homeostasis of catabolism and anabolism in the extracellular matrix (ECM), uncontrolled activation of immunologic cascades, dysfunction, and loss of nucleus pulposus (NP) cells in addition to dynamic cellular and biochemical alterations in the microenvironment of intervertebral disc (IVD). Currently, the main therapeutic approach regarding IDD is surgical intervention, but it could not considerably cure IDD. Exosomes, extracellular vesicles with a diameter of 30–150 nm, are secreted by various kinds of cell types like stem cells, tumor cells, immune cells, and endothelial cells; the lipid bilayer of the exosomes protects them from ribonuclease degradation and helps improve their biological efficiency in recipient cells. Increasing lines of evidence have reported the promising applications of exosomes in immunological diseases, and regarded exosomes as a potential therapeutic source for IDD. This review focuses on clarifying novel therapies based on exosomes derived from different cell sources and the essential roles of exosomes in regulating IDD, especially the immunologic strategy.

LATS1 Regulates Mixed-Lineage Kinase 3 (MLK3) Subcellular Localization and MLK3-Mediated Invasion in Ovarian Epithelial Cells

Mixed-lineage kinase 3 (MLK3) activates mammalian mitogen-activated protein kinase (MAPK) signaling pathways in response to cytokines and stress stimuli. MLK3 is important for proliferation, migration, and invasion of different types of human tumor cells. We observed that endogenous MLK3 was localized to both the cytoplasm and the nucleus in immortalized ovarian epithelial (T80) and ovarian cancer cells, and mutation of arginines 474 and 475 within a putative MLK3 nuclear localization sequence (NLS) resulted in exclusion of MLK3 from the nucleus. The large tumor suppressor (LATS) Ser/Thr kinase regulates cell proliferation, morphology, apoptosis, and mitotic exit in response to cell-cell contact. RNA interference (RNAi)-mediated knockdown of LATS1 increased nuclear, endogenous MLK3 in T80 cells. LATS1 phosphorylated MLK3 on Thr477, which is within the putative NLS, and LATS1 expression enhanced the association between MLK3 and the adapter protein 14-3-3ζ. Thr477 is essential for MLK3-14-3-3ζ association and MLK3 retention in the cytoplasm, and a T477A MLK3 mutant had predominantly nuclear localization and significantly increased invasiveness of SKOV3 ovarian cancer cells. This study identified a novel link between the MAPK and Hippo/LATS1 signaling pathways. Our results reveal LATS1 as a novel regulator of MLK3 that controls MLK3 nuclear/cytoplasmic localization and MLK3-dependent ovarian cancer cell invasion.

MicroRNA Signature in Melanoma: Biomarkers and Therapeutic Targets

Melanoma is the utmost fatal kind of skin neoplasms. Molecular changes occurring during the pathogenic processes of initiation and progression of melanoma are diverse and include activating mutations in BRAF and NRAS genes, hyper-activation of PI3K/AKT pathway, inactivation of p53 and alterations in CDK4/CDKN2A axis. Moreover, several miRNAs have been identified to be implicated in the biology of melanoma through modulation of expression of genes being involved in these pathways. In the current review, we provide a summary of the bulk of information about the role of miRNAs in the pathobiology of melanoma, their possible application as biomarkers and their emerging role as therapeutic targets for this kind of skin cancer.

The regulatory function of mixed lineage kinase 3 in tumor and host immunity

Protein kinases are the second most sought-after G-protein coupled receptors as drug targets because of their overexpression, mutations, and dysregulated catalytic activities in various pathological conditions. Till 2019, 48 protein kinase inhibitors have received FDA approval for the treatment of multiple illnesses, of which the majority of them are indicated for different malignancies. One of the attractive sub-group of protein kinases that has attracted attention for drug development is the family members of MAPKs that are recognized to play significant roles in different cancers. Several inhibitors have been developed against various MAPK members; however, none of them as monotherapy has shown sustainable efficacy. One of the MAPK members, called Mixed Lineage Kinase 3 (MLK3), has attracted considerable attention due to its role in inflammation and neurodegenerative diseases; however, its role in cancer is an emerging area that needs more investigation. Recent advances have shown that MLK3 plays a role in cancer cell survival, migration, drug resistance, cell death, and tumor immunity. This review describes how MLK3 regulates different MAPK pathways, cancer cell growth and survival, apoptosis, and host's immunity. We also discuss how MLK3 inhibitors can potentially be used along with immunotherapy for different malignancies.

MLK3 Is Associated With Poor Prognosis in Patients With Glioblastomas and Actin Cytoskeleton Remodeling in Glioblastoma Cells

Mixed lineage kinase 3 (MLK3) has been implicated in human melanoma and breast cancers. However, the clinical significance of MLK3 in human gliomas and the underlying cellular and molecular mechanisms remain unclear. We found that MLK3 proteins were highly expressed in high-grade human glioma specimens and especially prevalent in primary and recurrent glioblastoma multiforme (GBM). High levels of MLK3 mRNA were correlated with poor prognosis in patients with isocitrate dehydrogenase (IDH)-wild-type (wt) gliomas. Furthermore, genetic ablation of MLK3 significantly suppressed the migration and invasion abilities of GBM cells and disrupted actin cytoskeleton organization. Importantly, MLK3 directly bound to epidermal growth factor receptor kinase substrate 8 (EPS8) and regulated the cellular location of EPS8, which is essential for actin cytoskeleton rearrangement. Overall, these findings provide evidence that MLK3 upregulation predicts progression and poor prognosis in human IDH-wt gliomas and suggest that MLK3 promotes the migration and invasion of GBM cells by remodeling the actin cytoskeleton via MLK3-EPS8 signaling.

Importance of microRNAs in Skin Oncogenesis and Their Suitability as Agents and Targets for Topical Therapy

Skin cancer is the most common cancer worldwide, with rapidly increasing incidence and consistent mortality. Skin cancer encompasses melanoma and non-melanoma skin cancer, which in turn is mainly divided into cutaneous squamous cell carcinoma and basal cell carcinoma. Small noncoding micro-RNAs (miRNAs) regulate protein expression after transcription and play a role in the development and progression of skin cancer. Deregulated expression of miRNAs in skin cancer is associated with cell proliferation, angiogenesis, metastasis, apoptosis, immune response, and drug resistance. Specific patterns of miRNAs in specific skin cancer types can be used as diagnostic markers. For therapeutic purposes, both miRNA and chemically modified variants thereof as well as miRNA antagonists (antagomiRs) or RNA inhibitors may be applied topically. Due to their specific physicochemical properties, physical or chemical diffusion promoters are used with varying degrees of success. There is no question by now that such preparations have a high potential for the treatment of epithelial skin tumors in particular.

Advances in Natural or Synthetic Nanoparticles for Metastatic Melanoma Therapy and Diagnosis

Advanced melanoma is still a major challenge in oncology. In the early stages, melanoma can be treated successfully with surgery and the survival rate is high, nevertheless the survival rate drops drastically after metastasis dissemination. The identification of parameters predictive of the prognosis to support clinical decisions and of new efficacious therapies are important to ensure patients the best possible prognosis. Recent progress in nanotechnology allowed the development of nanoparticles able to protect drugs from degradation and to deliver the drug to the tumor. Modification of the nanoparticle surface by specific molecules improves retention and accumulation in the target tissue. In this review, we describe the potential role of nanoparticles in advanced melanoma treatment and discuss the current efforts of designing polymeric nanoparticles for controlled drug release at the site upon injection. In addition, we highlight the advances as well as the challenges of exosome-based nanocarriers as drug vehicles. We place special focus on the advantages of these natural nanocarriers in delivering various cargoes in advanced melanoma treatment. We also describe the current advances in knowledge of melanoma-related exosomes, including their biogenesis, molecular contents and biological functions, focusing our attention on their utilization for early diagnosis and prognosis in melanoma disease.

Mesenchymal stem cells-derived exosomes ameliorate nucleus pulposus cells apoptosis via delivering miR-142-3p: therapeutic potential for intervertebral disc degenerative diseases

Intervertebral disc degeneration (IDD) is the main cause of lower back pain (LBP), and puzzles massive individuals worldwide. Mesenchymal stem cells (MSCs) transplantation has been demonstrated to potentially ameliorate IDD progression, while the underlying mechanism has not been fully explained. Interleukin-1β (IL-1β) was used to induce nucleus pulposus cells (NPCs) injury. Bone marrow MSCs-derived exosomes were isolated using the super centrifugation method, and characterized using Transmission electron microscopy (TEM) and western blot. Cell viability was determined by MTT, while apoptosis was measured by Annexin-V staining using flow cytometry. miR-142-3fp and gene expressions were measured by real-time PCR. The protein expressions were determined by western blot. Herein, we found exosomes from bone marrow MSCs are circular vesicles, about 80 nm in diameter, and with robust expression of TSG101 and CD63, but without of Calnexin. MSCs exosomes alleviated NPCs apoptosis by reducing IL-1β-induced inflammatory cytokines secretion and MAPK signaling activation. Additionally, MSCs exosomes inhibited NPCs apoptosis and MAPK signaling by delivering miR-142-3p that targets mixed lineage kinase 3 (MLK3). Overexpression of MLK3 abolished the effects of MSCs exosomes on the inflammatory condition, cell apoptosis, and MAPK signaling activation in NPCs. The results confirmed that bone marrow MSCs-derived exosomes-packaged miR-142-3p alleviates NPCs injury through suppressing MAPK signaling by targeting MLK3. The work highlights the therapeutic effect of MSCs on IDD progression, and bone marrow MSCs exosomes might be apromising therapeutic strategy for IDD.

Long non-coding RNA LINC00520 promotes the proliferation and metastasis of malignant melanoma by inducing the miR-125b-5p/EIF5A2 axis

BACKGROUND

Long intergenic non-protein coding RNA 520 (LINC00520), a novel identified lncRNA, has been shown to modulate the malignant phenotype of tumor cells in some malignant tumors. However, the exact role and molecular mechanism of LINC00520 in malignant melanoma has not been studied.

METHODS

The expression of LINC00520 in melanoma tissues were detected by using RNA-seq analysis and qRT-PCR. Melanoma cases from the public databases (The Cancer Genome Atlas (TCGA), GEO#GSE15605, GEO#GSE34460 and GEO#GSE24996) were included in this study. CCK-8 assay, EdU assay, transwell and scratch wound assay were used to explore the role of LINC00520 in melanoma cells. Luciferase reporter assays, MS2-RIP, RNA pull-down and RNA-ChIP assay were used to demonstrate the molecular biological mechanism of LINC00520 in melanoma.

RESULTS

We found that LICN00520 was found to be overexpressed in melanoma tissue. High expression of LICN00520 is a risk factor for the prognosis of melanoma patients. LINC00520 promotes the proliferation, invasion and migration of melanoma cells. LICN00520 exerted its oncogenic role by competitive binding miR-125b-5p to promote Eukaryotic initiation factor 5A2 (EIF5A2) expression. We also showed that LICN00520 promotes the growth and metastasis of melanoma in vivo through regulating miR-125b-5p/EIF5A2 axis.

CONCLUSIONS

All results elucidated the role and molecular mechanism of LINC00520 in the malignant development of melanoma. LINC00520, a new oncogene in melanoma, maybe serve as a survival biomarkers or therapeutic target for melanoma patients.

MLK3 is a newly identified microRNA-520b target that regulates liver cancer cell migration

The roles of microRNAs (miRNAs) in liver cancer have attracted much attention in recent years. In this study, we demonstrate that miR-520b is downregulated in MHCC-97H cells, a liver cancer cell line with high potential of metastasis, compared with MHCC-97L cells which has a low potential of metastasis. Furthermore, the enhanced expression of miR-520b could inhibit liver cancer cell migration, while silencing its expression resulted in increased migration. Mixed lineage kinase 3 (MLK3) was identified as a direct and functional new target of miR-520b. This regulation was also confirmed by luciferase reporter assays. In addition, our results showed that overexpression of the MLK3 expression partially reversed the effect of miR-520b on liver cancer cell migration, indicating that MLK3 contributes to the migration in liver cancer. The newly identified miR-520b/MLK3 axis partially elucidates the molecular mechanism of liver cancer cell migration and represents a new potential therapeutic target for liver cancer treatment.

MicroRNA Ratios Distinguish Melanomas from Nevi

The use of microRNAs as biomarkers has been proposed for many diseases, including the diagnosis of melanoma. Although hundreds of microRNAs have been identified as differentially expressed in melanomas as compared to benign melanocytic lesions, a limited consensus has been achieved across studies, constraining the effective use of these potentially useful markers. In this study, we applied a machine learning-based pipeline to a dataset consisting of genetic features, clinical features, and next-generation microRNA sequencing from micro-dissected formalin-fixed paraffin embedded melanomas and their adjacent benign precursor nevi. We identified patient age and tumor cellularity as variables that frequently confound the measured expression of potentially diagnostic microRNAs. By employing the ratios of microRNAs that were either enriched or depleted in melanoma compared to the nevi as a normalization strategy, we developed a model that classified all the available published cohorts with an area under the receiver operating characteristic curve of 0.98. External validation on an independent cohort classified lesions with 81% sensitivity and 88% specificity and was uninfluenced by the tumor content of the sample or patient age.

Therapeutic potential of targeting mixed lineage kinases in cancer and inflammation

Dysregulation of intracellular signaling pathways is a key attribute of diseases associated with chronic inflammation, including cancer. Mitogen activated protein kinases have emerged as critical conduits of intracellular signal transmission, yet due to their ubiquitous roles in cellular processes, their direct inhibition may lead to undesired effects, thus limiting their usefulness as therapeutic targets. Mixed lineage kinases (MLKs) are mitogen-activated protein kinase kinase kinases (MAP3Ks) that interact with scaffolding proteins and function upstream of p38, JNK, ERK, and NF-kappaB to mediate diverse cellular signals. Studies involving gene silencing, genetically engineered mouse models, and small molecule inhibitors suggest that MLKs are critical in tumor progression as well as in inflammatory processes. Recent advances indicate that they may be useful targets in some types of cancer and in diseases driven by chronic inflammation including neurodegenerative diseases and metabolic diseases such as nonalcoholic steatohepatitis. This review describes existing MLK inhibitors, the roles of MLKs in various aspects of tumor progression and in the control of inflammatory processes, and the potential for therapeutic targeting of MLKs.

Association between microRNA-125b expression in formalin-fixed paraffin-embedded tumor tissues and prognosis in patients with melanoma

Melanoma is an invasive and malignant type of tumor with unsatisfactory therapeutic outcomes. The present study aimed to detect the expression levels of microRNA (miR)-125b in formalin-fixed paraffin-embedded (FFPE) melanoma tissues and the association of its expression levels with the clinical features, diagnosis and prognosis of melanoma. Expression levels of miR-125b in 29 FFPE melanoma specimens (16 primary and 13 metastatic tumors), and 16 intradermal nevus (IDN) specimens as a control, were detected by reverse transcription-quantitative PCR. Associations among miR-125b expression and mortality, patient age and sex, tumor location and size, lymph node metastasis (LNM) and TNM stage were analyzed by t-test. The diagnostic value of miR-125b for melanoma was evaluated by receiver operating characteristic (ROC) curve analysis. Prognosis of patients in the microRNA-125b low- and high-expression groups was analyzed by Fisher's exact test. The association between miR-125b expression and the overall survival of patients with melanoma was assessed using Kaplan-Meier curve analysis and a Cox proportional hazards model. The results revealed that the expression levels of miR-125b in primary and metastatic melanomas were significantly lower than those in the IDN control group (P<0.05), and the expression levels of miR-125b in the metastatic group were significantly lower than those in the primary group (P<0.05). In addition, the expression levels of miR-125b were significantly associated with LNM (P=0.001) and TNM stage (P=0.004), but not with age, sex, tumor size or location (P>0.05). ROC curve analysis revealed that the area under the curve (AUC) was 0.880, with a 95% CI of 0.777–0.984 (P<0.05). The overall survival rate of the patients with a low expression level of miR-125b (20.0%) was lower than that of patients with a high expression level of miR-125b (64.3%) (P<0.05). miR-125b expression was an independent predictor of overall survival in patients with melanoma [hazard ratio (HR), 0.252; 95% CI, 0.087–0.729]. Overall, these findings indicated that a low expression level of miR-125b was associated with higher LNM and TNM stage in patients with melanoma, and that this has a certain diagnostic value. miR-125b may be used for the early screening of melanoma and determining the prognosis of patients with melanoma, and may be a potential target for the treatment of the disease.

Interplay between small and long non-coding RNAs in cutaneous melanoma: a complex jigsaw puzzle with missing pieces

The incidence of cutaneous melanoma (CM) has increased in the past few decades. The biology of melanoma is characterized by a complex interaction between genetic, environmental and phenotypic factors. A greater understanding of the molecular mechanisms that promote melanoma cell growth and dissemination is crucial to improve diagnosis, prognostication, and treatment of CM. Both small and long non-coding RNAs (lncRNAs) have been identified to play a role in melanoma biology; microRNA and lncRNA expression is altered in transformed melanocytes and this in turn has functional effects on cell proliferation, apoptosis, invasion, metastasis, and immune response. Moreover, specific dysregulated ncRNAs were shown to have a diagnostic or prognostic role in melanoma and to drive the establishment of drug resistance. Here, we review the current literature on small and lncRNAs with a role in melanoma, with the aim of putting into some order this complex jigsaw puzzle.

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

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

miR‑590‑5p inhibits tumor growth in malignant melanoma by suppressing YAP1 expression

The microRNAs (miRNAs/miRs) involved in the carcinogenesis and progression of malignant melanoma (MM) remain unclear. In the present study, miR-590-5p was identified to be upregulated in MM cells compared with human melanocytes using a reverse transcription-quantitative polymerase chain reaction to screen established oncogenic and tumor suppressor miRNAs. miR-590-5p was demonstrated to inhibit the cell proliferation and tumor growth of MM cells in vitro and in vivo by performing Cell Counting Kit-8 and tumour xenograft assays, respectively. In addition, flowcytometry assays indicated that miR-590-5p induced cell apoptosis and cell cycle arrest at the G1 stage in MM cells. Finally, luciferase assays and western blot analysis results confirmed that the transcriptional regulator Yes-associated protein 1 (YAP1) is upregulated and inversely associated with miR-590-5p expression in MM cells, and is the direct target and functional mediator of miR-590-5p in MM. Altogether these results reveal the functional and mechanistic link between miR-590-5p and YAP1 in the progression of MM. Therefore, miR-590-5p is a potential therapeutic target in MM.

MLK3 phosphorylation by ERK1/2 is required for oxidative stress-induced invasion of colorectal cancer cells

Mixed lineage kinase 3 (MLK3) functions in migration and/or invasion of several human cancers; however, the role of MLK3 in colorectal cancer (CRC) invasion is unknown. MLK3 is a mitogen-activated protein kinase (MAPK) kinase kinase (MAP3K) which activates MAPK pathways through either kinase-dependent or -independent mechanisms. Human colorectal tumors display increased levels of reactive oxygen species (ROS) or oxidative stress. ROS, such as H2O2, are important for carcinogenesis and activate MAPK signaling pathways. In human colorectal carcinoma (HCT116) cells treated with H2O2, extracellular signal-regulated kinases 1 and 2 (ERK1/2) were activated and MLK3 exhibited reduced electrophoretic mobility (shift) in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), which was eliminated by phosphatase treatment. Pretreatment with the ROS scavenger N-acetyl-L-cysteine, the ERK1/2 inhibitor UO126, or ERK1/2 siRNA knockdown blocked the H2O2-induced shift of MLK3, while MLK3 inhibition with Cep1347 did not. In co-immunoprecipitation experiments performed on H2O2-treated HCT116 cells, endogenous MLK3 associated with endogenous ERK1/2 and B-Raf. Active ERK1 phosphorylated kinase dead FLAG-MLK3 in vitro, whereas ERK1 phosphorylation of kinase dead FLAG-MLK3-S705A-S758A was reduced. Both MLK3 siRNA knockdown and FLAG-MLK3-S705A-S758A expression decreased ERK1/2 activation in H2O2-treated cells. Prolonged H2O2 treatment activated ERK1/2 and promoted invasion of colon cancer cells, which was attenuated by MLK3 siRNA knockdown. Furthermore, S705A-S758A-FLAG-MLK3 demonstrated decreased oxidative-stress induced colon cancer cell invasion, but increased interaction with GST-B-Raf as compared with wild-type-FLAG-MLK3 in H2O2-treated cells. These results suggest oxidative stress stimulates an ERK1/2-dependent phosphorylation of MLK3 on Ser705 and Ser758, which promotes MLK3-dependent B-Raf and ERK1/2 activation; this positive feedback loop enhances the invasion of colon cancer cells.

Recent advances in melanoma research via "omics" platforms

Melanoma has a high mortality rate and metastatic melanoma is highly resistant to conventional therapies. "Omics" fields such as proteomics and microRNA and exosome studies have provided new knowledge to complement the information generated by genomic studies. This work aimed to review the current status of biomarker discovery for melanoma through multi-"omics" platforms. A few sets of novel microRNAs and proteins are described, some of them with important implications in suppressing melanoma at different stages. Upregulation of genes involved in angiogenesis, immunosuppressive factors, modification of stroma, capture of melanoma cells in lymph nodes and factors responsible for tumour cell recruitment have been identified in exosomes, among molecules with other functions. A remarkable series of proteins involved in epithelial-mesenchymal/mesenchymal-epithelial transitions, inflammation, motility, proliferation and progression processes, centrosome amplification, aneuploidy, inhibition of CD8+ effector T-cells, and metastasis in general were identified. Genomic and protein-protein interactions or metabolome levels were not analysed. Proteomics tools such as Orbitrap shotgun mass spectrometry or deep mining proteomic analysis utilizing high-resolution reversed phase nanoseparation in combination with mass spectrometry are also discussed. The application of these tools together with bioinformatics approaches applied to the clinical setting will enable the implementation of personalized medicine in the near future.

MicroRNA dysregulation in melanoma

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

MLK3 Signaling in Cancer Invasion

Mixed-lineage kinase 3 (MLK3) was first cloned in 1994; however, only in the past decade has MLK3 become recognized as a player in oncogenic signaling. MLK3 is a mitogen-activated protein kinase kinase kinase (MAP3K) that mediates signals from several cell surface receptors including receptor tyrosine kinases (RTKs), chemokine receptors, and cytokine receptors. Once activated, MLK3 transduces signals to multiple downstream pathways, primarily to c-Jun terminal kinase (JNK) MAPK, as well as to extracellular-signal-regulated kinase (ERK) MAPK, P38 MAPK, and NF-κB, resulting in both transcriptional and post-translational regulation of multiple effector proteins. In several types of cancer, MLK3 signaling is implicated in promoting cell proliferation, as well as driving cell migration, invasion and metastasis.

Overexpression of miR-199a-5p decreases esophageal cancer cell proliferation through repression of mitogen-activated protein kinase kinase kinase-11 (MAP3K11)

Studies examining the oncogenic or tumor suppressive functions of dysregulated microRNAs (miRs) in cancer cells may also identify novel miR targets, which can themselves serve as therapeutic targets. Using array analysis, we have previously determined that miR-199a-5p was the most downregulated miR in two esophageal cancer cell lines compared to esophageal epithelial cells. MiR-199a-5p is predicted to bind mitogen-activated protein kinase kinase kinase 11 (MAP3K11) mRNA with high affinity. In this study, we observed that MAP3K11 is markedly overexpressed in esophageal cancer cell lines. Forced expression of miR-199a-5p in these cells leads to a decrease in the mRNA and protein levels of MAP3K11, due to decreased MAP3K11 mRNA stability. A direct binding interaction between miR-199a-5p and MAP3K11 mRNA is demonstrated using biotin pull-down assays and heterologous luciferase reporter constructs and confirmed by mutational analysis. Finally, forced expression of miR-199a-5p decreases proliferation of esophageal cancer cells by inducing G2/M arrest. This effect is mediated, in part, by decreased transcription of cyclin D1, due to reduced MAP3K11-mediated phosphorylation of c-Jun. These findings suggest that miR-199a-5p acts as a tumor suppressor in esophageal cancer cells and that its downregulation contributes to enhanced cellular proliferation by targeting MAP3K11.

MAP3K11 is a tumor suppressor targeted by the oncomiR miR-125b in early B cells

MicroRNAs (miRNAs) are a class of small, non-coding RNAs that posttranscriptionally regulate gene expression and thereby control most, if not all, biological processes. Aberrant miRNA expression has been linked to a variety of human diseases including cancer, but the underlying molecular mechanism often remains unclear. Here we have screened a miRNA expression library in a growth factor-dependent mouse pre-B-cell system to identify miRNAs with oncogenic activity. We show that miR-125b is sufficient to render pre-B cells growth factor independent and demonstrate that continuous expression of miR-125b is necessary to keep these cells in a transformed state. Mechanistically, we find that the expression of miR-125b protects against apoptosis induced by growth factor withdrawal, and that it blocks the differentiation of pre-B to immature B cells. In consequence, miR-125b-transformed cells maintain expression of their pre-B-cell receptor that provides signals for continuous proliferation and survival even in the absence of growth factor. Employing microarray analysis, we identified numerous targets of miR-125b, but only reconstitution of MAP3K11, a critical regulator of mitogen- and stress-activated kinase signaling, interferes with the cellular fitness of the transformed cells. Together, this indicates that MAP3K11 might function as an important tumor suppressor neutralized by oncomiR-125b in B-cell leukemia.

MicroRNA-125b suppresses the epithelial-mesenchymal transition and cell invasion by targeting ITGA9 in melanoma

Increasing evidence has shown that aberrant miRNAs contribute to the development and progression of human melanoma. Previous studies have shown that miR-125b functions as a suppressor in malignant melanoma. However, the molecular function and mechanism by which miR-125b influences melanoma growth and invasion are still unclear. In this study, we aimed to investigate the role of miR-125b in melanoma progression and metastasis. We found that miR-125b expression is significantly downregulated in primary melanoma, and an even greater downregulation was observed in metastatic invasion. Restored expression of miR-125b in melanoma suppressed cell proliferation and invasion both in vitro and in vivo. Furthermore, our findings demonstrate that upregulating miR-125b significantly inhibits malignant phenotypes by repressing the expression of integrin alpha9 (ITGA9). Finally, our data reveal that upregulated expression of ITGA9 in melanoma tissues is inversely associated with miR-125b levels. Together, our results demonstrate that upregulation of ITGA9 in response to the decrease in miR-125b in metastatic melanoma is responsible for melanoma tumor cell migration and invasion.

High expression of kinesin light chain-2, a novel target of miR-125b, is associated with poor clinical outcome of elderly non-small-cell lung cancer patients

Background:

MiR-125b has critical role in non-small-cell lung cancer (NSCLC) cell migration, and its target genes have not been elucidated. Kinesin-1 light chain (KLC)-2 was predicted as one of miR-125b's targets by bioinformatics analysis. This study is to identify the function of KLC2 and its interaction with miR-125b in NSCLC.

Methods:

Kinesin-1 light chain-2 protein expression and its clinical relevance were analysed in 140 matched NSCLC and adjacent non-neoplastic lung tissues. Both KLC2 gain- and loss-of-function analyses were performed in NSCLC cell lines by transient transfection. The direct interaction between KLC2 and miR-125b was confirmed by a luciferase reporter assay and a transient co-transfection assay as well as an analysis of eight matched clinical samples.

Results:

KLC2 protein was upregulated in NSCLC cell lines and tissues, and was an independent predictor of poor prognosis for elderly NSCLC patients. Kinesin-1 light chain-2 remarkably enhanced the invasive and migratory ability of NSCLC cells. MiR-125b inhibited KLC2 3′-untranslated region luciferase activity and protein expression, and inversely correlated with KLC2 expression in clinical samples. Kinesin-1 light chain-2 almost completely reversed miR-125b-induced inhibition on migration and invasion.

Conclusions:

Kinesin-1 light chain-2 protein overexpression predicts poor survival in elderly NSCLC patients. Kinesin-1 light chain-2 acts as a proto-oncogene and a functional target of miR-125b in NSCLC cells.

MicroRNAs in melanocyte and melanoma biology

The importance of microRNAs as key molecular components of cellular processes is now being recognized. Recent reports have shown that microRNAs regulate processes as diverse as protein expression and nuclear functions inside cells and are able to signal extracellularly, delivered via exosomes, to influence cell fate at a distance. The versatility of microRNAs as molecular tools inspires the design of novel strategies to control gene expression, protein stability, DNA repair and chromatin accessibility that may prove very useful for therapeutic approaches due to the extensive manageability of these small molecules. However, we still lack a comprehensive understanding of the microRNA network and its interactions with the other layers of regulatory elements in cellular and extracellular functions. This knowledge may be necessary before we exploit microRNA versatility in therapeutic settings. To identify rules of interactions between microRNAs and other regulatory systems, we begin by reviewing microRNA activities in a single cell type: the melanocyte, from development to disease.